Design Fabrication and Installation of an Open Loop Geothermal Cooling System for a Residential House Application

Design, Fabrication and Installation of an OpenLoop Geothermal Cooling System for a Residential House Application

A Thesis Proposal presented to the School of Mechanical Engineering Mapua Institute of Technology

In Partial Fulfillment Fulfillment of the Requirements for the Degree of Bachelor of Science in Mechanical Engineering

By:

Alcarde, Alfred S. Manansala, John Luigi T. Rendaje, Reycian G. Villarosa, Alan Daniel B.

July 13, 2012

Acknowledgment

This study would not have been possible without the guidance and help of several individuals who, in one way or another, contributed and extended their valuable assistance in the preparation and completion of this study. We would like to express our most sincere gratitude to Engr. Hans Bosshard, for having him as our adviser whose patience, motivation, enthusiasm, and immense knowledge have helped us all throughout our research and writing process. We coul d n ot have ima gin ed h avi ng a b ett er mentor other than him. We are deeply indebted to Engr. Luis Angelo Sevilla for sponsoring our thesis, for lending his time and patience to us, without him our study will not be a success. We would like to thank the rest of our panel members: Dr. Manuel Belino, the Dean of The School of Mechanical and Manufacturing Engineering, Engr. Jonathan Anastasio, and Engr. Jaime Honra, for their encouragement, insightful comments, and questions. We would also like to thank our parents for their unwavering support throughout the completion of the whole course. Above all, to our Almighty God for the countless blessings He has bestowed upon us. For this achievement, we give back all the glory and praises to the omnipotent Father Almighty.

Abstract

This undergraduate thesis focuses on the evaluation of the open-loop geothermal cooling for a residential house application. It involves the design, fabrication and installation of the open-loop geothermal cooling system for an eight by ten ft. conditioned room. The system was composed of three subsystems for an open loop geothermal cooling system which were the centrifugal air blower system, piping system and damper system. The operation of the designed geothermal cooling system utilizes the cold temperature of the soil which can serve as a heat sink. It promotes conduction and convection heat transfer process between the air from the conditioned room and the heat exchanger burrowed to the soil at a depth of 10 feet. With this, the study could provide possible alt ernative for an air-conditioning system. The results gathered proved that the geothermal cooling system can provide a comfort cooling and that the soil of the Philippines is applicable for the geothermal cooling system. It lessened the room temperature with an approximate value of 2°C after two hours of continuous operation and with an average air-flow discharge velocity of 5m/s. Based on the computation which compared the window type air conditioning unit versus the installed geothermal cooling system (based from power consumption) electricity consumption for one month, it showed that it is more economical to use a geothermal cooling system having a computed cost of P571.809.00 than an aircon ditioning system having a computed cost of P964.768.00.

CHAPTER I INTRODUCTION 1.1 Overview

Geothermal cooling systems work by utilizing the principle of transferring the heat from the room to an underground heat sink. The medium utilized for heat transfer is a refrigerant, which is usually air or a liquid (water or a solution). The selection of the medium for the underground heat exchanger varies with both the application and the required capacity. In this study, the medium considered was air based from the system’s design and availability. The system for the study was composed of three subsystems for an open loop geothermal cooling system which were the centrifugal air blower system, piping system and damper system. The centrifugal air blower was used to induce air flow for the system through suction and discharge between the room and the piping system. The piping system served as the heat exchanger where conduction and convection heat transfer occurred. The damper system was installed to regulate the humidity and the temperature of the room. The design of these three subsystems varied with both the application and the capacity of the system. The geothermal cooling system served as an alternative means for providing the benefits brought by a conventional air-conditioning system to control a room temperature regardless of the ambient temperature and humidity in the Philippines. Also, the application of geothermal cooling system can provide the benefits of a conventional air conditioning system but with a lesser electrical cost.

The study provided the necessary data to prove the possibility of finding other means of cooling processes for the room to be economical, environmental and practical that can be shown from a small scale design. The dependence of the air conditioning unit to refrigerants, such as R12, will be minimized while the utilization of the Philippines’ soil temperature will be the group’s priority to be considered (United States Environmental Protection Agency 2010). 1.2 Statement of the Problem

In consideration to the climate of the Philippines, the group focused on the necessity to find much sustainable and environmental ways to provide comfort cooling, as compared to traditional air-conditioning systems. The study considered an open loop geothermal cooling system to provide a comfort cooling in the conditioned room instead of an air-conditioning system. The open loop geothermal cooling system was studied to provide convenience and alternatives for an air conditioning unit to help lessen the electricity consumption. The selection of subsystems such as damper and centrifugal air blower for the geothermal cooling system was evaluated based from the theoretical computation to maximize the efficiency of the operation of the system and minimize its electricity consumption. The operation of the subsystems damper and centrifugal air blower was needed to function simultaneously, to lessen the excessive use of electricity and refrain the system from being overused. Over usage occurs when the centrifugal air blower continuously discharges cool air to the room while the damper introduces fresh air. Thus, the cooling comfort is not achieved.

Selection and installation of thermostat control system was also needed in order for the system to function effectively. The computation for the design of the geothermal cooling system was based from existing studies available only from foreign countries. Most of the standard values used for the computation for the designed system, such as length of the piping system for heat exchanger and selection of centrifugal air blower, were approximate values and empirical formulas based from other countries due to the absence of the necessary data in the Philippines. The system was developed to investigate the feasibility and practicability of the system for local residential use. The materials needed for the study were easily available and could provide an inexpensive means for achieving the small scale geothermal cooling system. The effectiveness of using subterranean soil as a heat sink in the Philippines has not yet been proven widely by many institutions. This study relied mostly on empirical formulas and data from the studies of other countries in evaluating the properties of the Philippine soil. However, small groups from the Philippines had studied the geothermal cooling system and it resulted to an effective comfort cooling. These results proved the possibility of installing a geothermal cooling system in the Philippines. The design of the geothermal cooling system was made to promote comfort cooling in a conditioned room by satisfying the standards of a room temperature based on the Philippine Mechanical Code that is between 23 ºC and 27 ºC or in accordance with local regulations.

1.3 Objectives of the Study

The group achieved the following objectives: 1.3.1 General Objective

The group aimed to design, fabricate, install and test an open loop geothermal cooling system with an automatic temperature control using a thermostat and a damper in a controlled room for residential house application. 1.3.2

Specific Objectives

The group aimed the following objectives: 1.3.2.1 Select a site that is suitable for geothermal cooling 1.3.2.2 Measure and evaluate room and ambient temperature 1.3.2.3 Design, fabricate and install an open loop earth-coupled heat exchanger/

piping system 1.3.2.4 Select and install a centrifugal air blower 1.3.2.5 Install thermostat control system in centrifugal air blower 1.3.2.6 Fabricate and install a damper with an actuator controlled by a thermostat

for automatic cut off/cut on 1.3.2.7 Compare the outdoor temperature (ambient), room temperature and soil

temperature 1.3.2.8 Evaluate the performance of the system 1.3.2.9 Identify the economic benefits of the study

1.4 Significance of the Study

The geothermal cooling system provides a more environment friendly air conditioning alternative because of the absence of hazardous refrigerants. Instead of using a refrigerant, the system used air from the room and brought it to the geothermal heat exchanger with the use of a blower. Upon passing the heat exchanger, the air was cooled and returned to the conditioned room. The use of thermostat control system for automatic temperature control installed at the damper system provided convenient comfort inside the conditioned room. The function of the thermostat control system at the damper was to maintain the computed effective temperature needed for comfort cooling. When the geothermal cooling system reached the set temperature (computed effective temperature), the controller of the air blower will send a cut-off signal that will turn off the air blower. The conditioned room is then supplemented by a damper with ambient air. The damper operates by introducing fresh air (10% of total volumetric flow in the heat exchanger) and change the humidity of the room until it reaches the effective comfort cooling of 60% relative humidity. The application of these two thermostat controllers assists in the minimization of the electricity consumption of the geothermal cooling system by limiting the time of operation automatically. The installation of the geothermal cooling system provides Filipinos more access to air conditioning system with low electric costs. With a properly designed geothermal cooling system, the long term benefit it can offer in the electric bill will be noticed through a less airconditioning unit operational cost which is approximately 25% only.

The study served as a starting point that may invite other innovations for future references and recommendations. 1.5 Scope and Limitations

The thesis topic concentrated on the design, fabrication and installation of a small scale geothermal cooling system that was applied to a constructed room in Limay, Bataan with the dimensions of 8ft. by 10ft. The system was composed of three systems: piping system, air blower and damper system with a thermostat device which served as the control system for delivering the cooled air to the room. Its function was not evaluated continuously for one whole day rather it was done at predetermined intervals for every two hours. The evaluation of operation of geothermal cooling system must not be compared to the operation of an air-conditioning unit. The use of existing geothermal studies was the basis of this study to avoid in-depth analysis of the soil property for standard values used in the computations. The maximum depth of the heat exchanger is 10 ft. as limited by the design and the innate difficulty for excavation of the site. Soil and temperature gradient analysis was not included in the study. The installation was done in the month of June only. The data used for performance testing of the system was limited to those gathered during the same period. The design computations and the operation of the developed system were limited to the available data on the characteristics of air during the said period. Moreover, the data gathered by the group focused more on the conditioned room temperature and not on relative humidity. The group purchased materials based on the design computation such as the air blower, black iron pipes and damper. The damper was modified to install the electronic control system with the thermostat. The damper system was attached to the room beside the suction pipe of the

centrifugal air blower so that the introduced fresh air may go directly to the designed heat exchangers underground. The reason for installing the thermostat controller in both the single phase motor of the air blower and the actuator of the damper was to maintain the desired temperature inside the room, lessen the electricity consumption of the system by not having excessive operation and for the damper and the geothermal cooling system to function efficiently in uniform. In-depth details about the thermostat control system are not part of the discussion of the study. To prove the economic benefits of the small scale geothermal cooling system, only the electric bill for one month based on the theoretical MERALCO computations. Options for site selection were minimal because of the expensive labor and works needed in an installation of a geothermal cooling system. It required a large area of empty lot, which will be dug to a depth of 10 feet. Also, it was necessary to have the consent of the landlord since there will be risks and precautions

CHAPTER 2 REVIEW OF RELATED LITERATURE

This chapter provides a review of various studies and literature related to geothermal cooling. 2.1 Review of Related Studies

This section will highlight different kinds of related studies on geothermal cooling. 2.1.1 Investigating the Potential Benefits and Risks for Low to Zero Energy AirSourced Earth Coupled Cooling and Heating Systems. (Butler, Littlewood and Tucker 2011)

The paper determines the compliance requirements in relation to energy consumption and greenhouse gas emissions for buildings. It also discussed the technology of the ASECch systems that provide potential benefits in designing an energy saving building that operates in both cooling and heating depending on its purpose. Criteria were also proposed in this paper for the calculation of the performance for a given climate location. One objective of this paper is to maintain healthy indoor air quality which maintains relative concentrations of carbon dioxide (CO 2) below the standard levels. A study from Health Canada suggests that CO 2 concentrations above 1800



are indicative

that inadequate or no fresh air is introduced in the room though complaints have been recorded at concentrations as low as 1100



.

Through this study, the group prioritized supplying fresh air into the system to ensure that CO2 concentration was not above the standards. The effect of supplying fresh air in the system is very important to lessen the possibility of having a sick building syndrome and to lessen the possibility of causing loss of productivity and possible illnesses inside the built environment. 2.1.2 Study on Using the Ground as a Heat Sink for a 12,000-Btu/h Modified Air Conditioner (Tanatvanit 2009)

The paper presents an experiment of a modified air conditioner with a capacity of 12,000-Btu/h that used the ground as a heat sink for the condenser. The objective of the study was to reduce the energy consumption of air conditioning, particularly in household and building, using sink reservoir. Generally, there were two large sources of sink reservoirs that can be applied, namely water (i.e. sea and lake) and ground (Odey 1993). Regarding the ground, two methods were proposed: earth/air tunnel and ground source heat pump (Givoni, and Katz, 1985). The experiment was performed in a room with a nearby soil. A modified air conditioner was used by extending the copper coils 1 meter below the ground acting as a heat sink varied in four values of lengths: 67, 50, 40, and 30 m in length. The test runs were done during day time from 8am to 5pm for a week per different values of condensing coil lengths. The electrical consumption of Modified Air Conditioner (compressor and evaporating fan) was also measured during test runs to maintain similar conditions. The values that yielded are presented in Table 2-1.

Table 2-1 Result data for the values of COP for different condensing coil lengths of modified air conditioner compared to that of condenser air conditioner.

Flow rate of R-134a (kg/s)

COP

M-AC (67 m)

0.035

6.9

M-AC (50 m)

0.028

5.5

M-AC (40 m)

0.0201

3.3

M-AC (30 m)

0.014

2.1

C-AC (22 m)

0.0145

2.5

The COP values of M-AC were higher than that of C-AC except for the case of 30m coil length. Through this experiment, the group will surely have an idea that if the length of coils is longer, the higher the value of COP. 2.1.3 Development of an Earth-Coupled Air-conditioning System for Residential Application (Abracia, Dizon et al. 2009)

The paper mentioned above was the researchers’ primary source of information about geothermal cooling system. The study was very relevant since it was done in the Philippines. The study aimed to design and develop an air-conditioning system using the underground temperature to cool down the temperature of the ventilation air or using the soil as heat sink. The study also aimed to provide a suitable environment for a process being carried out regardless of heat inside the house and external weather conditions. The group used polyvinyl chloride pipe as the material for the ground loop. The ground loop was on a depth of 6 ft. and used 36 square feet of area. The length of the

ground loop amounted to 107 ft. The cooling system had an option of getting air from the ambient air by using a return duct. The study was able to reach a temperature difference between the supply and ambient temperature of 3 °C to 8 °C. It maintained a room temperature of 24 °C to 26 °C. The average relative humidity of the ambient air and the supply air was recorded 70% and 75% respectively.

2.1.4 Air Conditioning Earth Coupled Water Source Heat Pumps - Closed

and

Open Loop Systems (Williams Jr. and Sveter 2010)

The paper focuses on the thermodynamic and heat transfer principles as applied to earth-coupled. There are two types of loops being discussed in this paper namely: open loop and closed loop system. In open loop system, water under the ground is being withdrawn by an aquifer and used for cooling or heating purposes then discharged into an injection back in the aquifer. In closed system, water inside the pipe is circulated in a continuous closed pipe loop from the soil through the heat exchanger and then back into the soil to be cooled or heated. 2.2 Related Literature

This section will focus on the different related literature on geothermal cooling. 2.2.1 Weather Conditions

There are only two seasons in the Philippines, wet and dry. The northern part of the Philippines is cooler in the months of November to February and the

hottest in the months of April and May. In big cities like Metro Manila, concrete and asphalts retain the heat in said cities (Purdie 2008). 2.2.2 Soil Temperature

Soil temperature plays an important role in many processes, which take place in the soil such as chemical reactions and biological interactions. Soil temperature varies in response to exchange processes that take place primarily through the soil surface. These effects are propagated into the soil profile by transport processes and are influenced by such things as the specific heat capacity, thermal conductivity and thermal diffusivity (Amoozegar 1989). Soil temperature varies from month to month as a function of incident solar radiation, rainfall, seasonal swings in overlying air temperature, local vegetation cover, type of soil, and depth in the earth (McNeill 1992). 2.2.3 Soil Thermal Properties

These soil thermal properties depend strongly on soil porosity and moisture content. Therefore, any preliminary assessment of a potential geothermal heat pump project will require knowing the soil texture and the average groundwater level at the project site (McNeill 1992). 2.2.4 Air Properties

Because the weight of air varies with pressure and temperature, it has to be defined accurately. The following figures may be used. The weight of dry air (no o

moisture content) at 0 C and under a normal atmospheric pressure of 1013

3

o

mbar is 1.293 kg/m . The weight of dry air (no moisture content) at 0 C and at a 3

pressure of 1000 mbar (1 Bar) is 1.275 kg/m (Frazer 1999). Table 2-2 shows the changes of air properties with regard to its temperature. Table 2-2 Common properties for air



Temperature Density -to

- 3

Specific heat

Thermal

Kinematic

Expansion

capacity

conductivity

viscosity

coefficient

- cp -

-l-

- ν -

-b-

(kJ/kg.K)

(W/m.K)

Prandtl's number

( C)

(kg/m )

-150

2.793

1.026

0.0116

3.08

8.21

0.76

-100

1.980

1.009

0.0160

5.95

5.82

0.74

-50

1.534

1.005

0.0204

9.55

4.51

0.725

0

1.293

1.005

0.0243

13.30

3.67

0.715

20

1.205

1.005

0.0257

15.11

3.43

0.713

40

1.127

1.005

0.0271

16.97

3.20

0.711

60

1.067

1.009

0.0285

18.90

3.00

0.709

80

1.000

1.009

0.0299

20.94

2.83

0.708

100

0.946

1.009

0.0314

23.06

2.68

0.703

120

0.898

1.013

0.0328

25.23

2.55

0.70

140

0.854

1.013

0.0343

27.55

2.43

0.695

160

0.815

1.017

0.0358

29.85

2.32

0.69

-6

2

-3

x 10 (m /s) x 10 (1/K)

- Pr -



Temperature Density -to

- 3

Specific heat

Thermal

Kinematic

Expansion

capacity

conductivity

viscosity

coefficient

- cp -

-l-

- ν -

-b-

(kJ/kg.K)

(W/m.K)

Prandtl's number

( C)

(kg/m )

180

0.779

1.022

0.0372

32.29

2.21

0.69

200

0.746

1.026

0.0386

34.63

2.11

0.685

250

0.675

1.034

0.0421

41.17

1.91

0.68

300

0.616

1.047

0.0454

47.85

1.75

0.68

350

0.566

1.055

0.0485

55.05

1.61

0.68

400

0.524

1.068

0.0515

62.53

1.49

0.68

-6

2

-3

x 10 (m /s) x 10 (1/K)

- Pr -

2.2.5 Principles of Heat Exchangers

Heat exchangers work because heat naturally flows from higher temperature to lower temperatures. Therefore, if a hot fluid and a cold fluid are separated by a heat conducting surface, heat can be transferred from the hot fluid to the cold fluid (Cripps 2006). Figure 2-1 shows the simplified heat exchanger.

Figure 2-1 Simplified Heat Exchanger (Source: http://www.vesma.com) 2.2.5.1

The rate of heat flow at any point depends on the following:

2.2.5.1.1

Heat transfer coefficient (U), itself a function of the properties of the fluids involved, fluid velocity, materials of construction, geometry and cleanliness of the exchanger

2.2.5.1.2 Temperature difference between hot and cold streams 2.2.5.2 Total heat transferred (Q) depends on the factors mentioned below: 2.2.5.2.1 Heat transfer surface area (A) 2.2.5.2.2 Heat transfer coefficient 2.2.5.2.3

Average temperature difference between the streams, strictly the log mean temperature (DT LM)

Thus, total heat transferred Q = UADT LM. However, the larger the area, the greater the cost of the exchanger (Cripps 2006).

2.2.6 Heat Transfer

The transfer of heat is normally from a high temperature object to a lower temperature object. Heat transfer changes the internal energy of both systems involved according to the First Law of Thermodynamics (Nave 1998). 2.2.6.1 Heat Conduction

Heat conduction is the flow of internal energy from a region of higher temperature to one of lower temperature by the interaction of the adjacent particles (atoms, molecules, ions, electrons, etc.) in the intervening space (Elert 1998).

The nature of the transfer of energy from the pipes and the soil is

through conduction due to the direct contact of solid particles. 2.2.6.2 Heat Convection

Convection is the flow of heat through a bulk, macroscopic movement of matter from a hot region to a cool region, as opposed to the microscopic transfer of heat between atoms involved with conduction (Drakos 1998). As this air heats, the molecules spread out, causing this region to become less dense than that of the surrounding. Being less dense than the surrounding cooler air, the hot air will subsequently rise due to buoyant forces - this movement of hot air into a cooler region is then said to transfer heat by convection. Convection will take place inside the pipe where the air flow transfers heat to the pipe. The transfer of the heat is called convection because the moving hot air transfers the heat to the walls of the pipe.

2.2.6.3 Temperature and Humidity

Warm air can hold much more mass of water vapor than cold air. Hypothetically, at 80ºF, it holds 10 grams of water vapor at 60% humidity. However, if the temperature is changed by 40ºF, then the warm air can hold 11 grams of water vapor. Thus, the 10 grams at new temperature holds 95% humidity. This is why the relationship is proportional. The dew point temperatures are typically closer to the current temperature in cold air, making the relative humidity, or the percent of water vapor in the air from what the water can hold, much higher. If the same temperature is considered and raised while keeping the same amount of water vapor, the maximum amount of water that can be held is much higher, making the relative humidity much lower (Ahrens 2007). Relative humidity has a particular value for a particular temperature. The value may be less for a higher temperature and high for a lower temperature as it denotes the ratio of the amount of water vapor actually present to the amount of water vapor required to saturate the air. 2.2.6.4 Air Flow Rate

The volume of fluid is displaced by a pump or compressor into a hydraulic or pneumatic system (Jergens 2012). Flow rate may be determined by measuring the velocity of fluid over a known area. Air flow rate is important because through this flow rate, other parameters can be solved.

2.2.7 Geothermal Energy

Geothermal heating and cooling systems, also known as GeoExchange systems, tap into the constant, moderate temperatures found a few feet below the surface of the earth, to offer the finest in home comfort conditioning. The shallow ground or upper 10 feet of the Earth's surface maintains a nearly constant temperature between 50° and 60°F (10° and 16°C) (Montgomery 2012). Types of Geothermal System

Geothermal systems use the earth as a heat source or heat sink. A series of pipes, commonly called a "loop," carry a fluid used to connect the geothermal system's heat pump to the earth. The different types of geothermal systems are shown in the following subsections below: 2.2.7.1 Open Loops

Open

loop

systems

were

used

successfully

for

decades.

Groundwater is drawn from an aquifer through a well. The water is then passed through the heat pump’s heat exchanger, and is discharged to the same aquifer through a second well at a distance from the first. Generally, two to three gallons per minute per ton of capacity is necessary for effective heat exchange. Since the temperature of ground water is nearly constant throughout the year, open loops are a popular option in areas where they are permitted.

Some local ground water chemical conditions can lead to fouling the heat pump's heat exchanger. Such situations may require precautions to keep carbon dioxide and other gases in the water solution. Other options include the use of cupronickel heat exchangers and heat exchangers that can be cleaned without introducing chemicals into the groundwater. Increasing environmental concerns means that local officials must be consulted to assure compliance with regulations concerning water use and acceptable water discharge methods. For example, discharge to a sanitary sewer system is rarely acceptable. Figure 2-2 shows a diagram of an open loop system.

Figure 2-2 Open Loop System (Source: http://www.energysavers.gov)

2.2.7.1.2 Closed Loops

Closed loop systems are the most commonly used loop orientation in geothermal heat pump. When properly installed, such systems are economical, efficient, and reliable. Water (or a water and antifreeze solution) is circulated through a continuous buried pipe keeping. The closed loop system is environmentally friendly because water in the loop prevents contamination to the external environment. The length of loop piping varies depending on ground temperature, thermal conductivity of the ground, soil moisture, and system design. (Some heat pumps work well with larger inlet temperature variations, which allow marginally smaller loops). 2.2.7.1.3 Closed Horizontal Loops

Horizontal closed loop installations are generally most costeffective for small installations, particularly for new construction where sufficient land area is available. These installations involve burying pipe in trenches dug with back-hoes or chain trenchers. Up to six pipes, usually in parallel connections, are buried in each trench, with minimum separations of a foot between pipes and ten to fifteen feet between trenches. Figure 2-3 shows a diagram of a closed loop system.

Figure 2-3 Closed Horizontal Loops (Source: http://www.energysavers.gov) 2.2.7.1.4 Closed Vertical Loops

Vertical closed loops are preferred in many situations. For example, most large commercial buildings and schools use vertical loops because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching. Vertical loops also minimize the disturbance to existing landscaping. For vertical closed loop system, a U-tube (more rarely, two Utubes) is installed in a well drilled 100 to 400 feet deep. Because conditions in the ground may vary greatly, loop lengths can range from 130 to 300 feet per ton of heat exchange. Multiple drill holes are required for most installations, where the pipes are generally joined in parallel or series-parallel configurations.

A vertical loop well field, being used for the Finger Lakes Institute, consists of 20 wells, drilled to a depth of 100 feet. There are 5 (clusters) of 4 wells spaced approximately 12 feet on center, The depth and number of wells was determined by the estimated heat and cooling load required to maintain a comfortable environment for the occupants. Figure 2-2 shows a diagram of a closed vertical loop system.

Figure 2-4 Closed Vertical Loops (Source: http://www.energysavers.gov) 2.2.7.1.5 Pond Loops

Pond closed loops are a special kind of closed loop system. Where there is a pond or stream that is deep enough and with enough flow, closed loop coils can be placed at the bottom of the pond. Fluid is pumped just as for a conventional closed loop ground system where conditions are

suitable, the economics are very attractive, and no aquatic system impacts have been shown. Figure 2-5 shows a diagram of a closed loop system at a pond or lake.

Figure 2-5 Closed Pond Loops (Source: http://www.energysavers.gov) 2.2.7.1.6 Hybrid Systems

Hybrid systems using several different geothermal resources, or a combination of a geothermal resource with outdoor air (i.e., a cooling tower), are another technology option. Hybrid approaches are particularly effective where cooling needs are significantly larger than heating needs. Where local geology permits, the "standing column well" is another option. In this variation of an open-loop system, one or more deep vertical wells are drilled. Water is drawn from the bottom of a standing column

and returned to the top. During periods of peak heating and cooling, the system can bleed a portion of the return water rather than re-injecting it all, causing water inflow to the column from the surrounding aquifer. The bleed cycle cools the column during heat rejection, heats it during heat extraction, and reduces the required bore depth. 2.2.8 Geothermal Cooling and Heating Application

The application of geothermal heating/cooling, also known as ground source

heat

pumps,

environmentally

has

sensitive

been of

all

named space

"the

most

energy-efficient

conditioning

systems",

by

and the

Environmental Protection Agency. The system's basic concept takes advantage of the earth's constant temperature, approximately 55°F, to heat and cool a building. By tapping this steady flow of heat from the earth in the winter, and displacing heat in the earth in the summer, a geothermal heat pump can save homeowners 40 to 70 percent in heating costs and 30 to 50 percent in cooling costs compared to conventional systems (Fitch 2009). A passive house is a building in which a comfortable interior climate can be maintained without active heating and cooling systems (Adamson 1987 and Feist 1988). The house heats and cools itself, hence "passive". For European passive construction, prerequisite to this capability is an annual heating requirement that is less than 15 kWh/(m²a) (4755 Btu/ft²/yr), not to be attained at the cost of an increase in use of energy for other purposes (e.g., electricity). Furthermore, the combined primary energy consumption of living

area of a European passive house may not exceed 120 kWh/(m²a) (38039 Btu/ft²/yr) for heat, hot water and household electricity. A passive house is costeffective when the combined capitalized costs (construction, including design and installed equipment, plus operating costs for 30 years) do not exceed those of an average new home (Feist 2012).

CHAPTER 3 THEORETICAL CONSIDERATIONS

This chapter discusses concepts necessary for the design, fabrication and installation of a small scale Geothermal Cooling System at Limay, Bataan. 3.1 Design of a Small Scale Geothermal Cooling System

The design of the geothermal cooling system was meant to control and modify the given room temperature as affected by the ambient temperature and other possible sources of temperature that could affect the controlled room temperature. The cooling was done by the temperature difference between the room temperature and the soil temperature that occurs at the system that was designed to have three subsystems which were thermostat controlled air blower system, piping system and thermostat controlled damper. The process starts with the provided air with certain temperature inside the piping system which circulates at a closed loop system. The air was cooled through conduction heat transfer between the temperature difference of air flowing in the pipe and the cold soil temperature at the depth of 6 feet for the first layer of horizontal loop, 8 feet for the secondary layer of horizontal loop and 10 feet for the third and last layer from the ground. The air was brought by a centrifugal air blower from the room with a high temperature to the piping system which served as the heat exchanger so that convection heat transfer could take place between the air flowing from the pipes and the piping system design and acted as a cooling coil. Conduction heat transfer took place from the temperature difference between the soil and the piping system.

Electricity consumption only took place at centrifugal air blower and damper, to promote efficient electricity consumption. The use of control system was introduced to the air blower and the damper to work uniformly. The air blower and the damper were set to achieve and maintain the room temperature equivalent to the computed effective temperature for comfort cooling. 3.2 Design of Piping System

The piping system served as the passage and the heat exchanger of the geothermal cooling system. The air travelled from the room to the piping system that acted as the heat exchanger. The air that underwent conduction and convection heat transfer carries the lower temperature from the soil and is used to control the room temperature to achieve comfort cooling though the pipe. 3.2.1 Piping System of Small Scale Geothermal Cooling System

The design of piping system for small scale geothermal system was classified into two loops: closed and opened loop. The loop applied to the study was an open loop with air as the medium in carrying the cold temperature. The cycle took place inside the system as conduction and convection heat transfer at the piping system. An open loop system is a process where the cooled medium is at cycle inside the system that is being contaminated by other substance or is affected by outside contaminants. In the study’s case, the air flowing through the system was affected by the outside air when the damper’s thermostat control detected that the room temperature was less than the maintained effective temperature.

The size of the piping system varied from the pump inlet and the further computation of the study. 3.2.2 Underground Piping System

The piping system underground is classified into two: Horizontal loop and Vertical loop. The loop applied for the study is a horizontal loop where the conduction heat transfer takes place. This piping system is placed underground with a depth of 6 feet for the first horizontal layer, 8 feet for second horizontal layer and 10 feet for third horizontal layer. It is considered to be the most cost effective for small installation such as for private uses (Geothermal Heating & Cooling systems 2005). Figure 3-1 shows an example of a horizontal type loop of a geothermal cooling system.

Figure 3-1 An example of a Horizontal Loop (Source: http://www.hydro.mb.ca)

3.3 Selection of Air Blower System

The air blower unit was used to distribute the cold temperature harnessed from the soil to the room using conduction and convection heat transfer. The design was composed of piping system where the geothermal cooling system was coupled while the single phase air blower induces the conditioned air. The selection of the air blower unit varied with the air temperature it was carrying, air flow, operational efficiency, power consumption, size occupied for its room installation and its initial price. In the study, the air blower unit was a single phase centrifugal blower. 3.4 Heat Transfer at the System

The heat transfers that were present at the Geothermal Cooling System were convection and conduction. Conduction occurred between the piping system and soil while convection occurred at air flowing through the pipe at turbulent flow. nd

The system followed the 2 law of thermodynamics which stated that “energy has quality as well as quantity, and actual process occurs in the direction of decreasing quality of nd

energy.” The 2 law of thermodynamics was followed when the horizontal loop gave off heat from the air flow to the soil of Limay, Bataan. 3.4.1 Conduction from fluids through pipes

Conduction was the transfer of energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interaction between particles. This occurred at the horizontal loop burrowed under the ground with the depth of 6 feet for first horizontal loop, 8 feet for second horizontal loop and 10 feet for third horizontal

loop. The heat transfer occurred between the cold soil and flowing warm air from the tube, as shown in equation 3.1.

  

Where:

(3.1)

=heat transfer U= overall conductance



A= area of the pipe =difference in temperature between the solid surface and surrounding fluid area

3.4.2 Convection

Convection was the transfer of energy between a solid surface and the adjacent fluid that was in motion. It involved the combined effects of conduction and fluid motion. This occurred at the piping system when the warm air flowed through the pipe at a turbulent flow. The air flow was induced by the centrifugal air blower. Equation 3.2 shows the effect of the temperature difference, mass flow rate, and the specific heat on the convection heat transfer rate.

     

Where: = heat transfer

 

m= mass flow rate = specific heat = designed temperature

(3.2)



= temperature leaving the heat exchanger

3.5 Room Heat Load Calculation

The room temperature was evaluated with relation to the ambient temperature, water at underground temperature, and sources of heat gain through heat load calculation and psychrometric chart. 3.5.1 Psychrometric Chart

The state of the atmospheric air at a specified pressure was evaluated using the psychrometric charts for air-conditioning applications. Psychrometry is the study of moist air and of the changes in its conditions. The psychrometric chart graphically represents the interrelation of air temperature and moisture. 3.5.1.1 Absolute humidity is the vapor content of air, given in grams or

kg of water vapor per kg of air, i.e. g/kg or kg/kg. It is also known as moisture content or humidity ratio. Air at a given temperature can support only a certain amount of moisture and no more. This is referred to as the saturation humidity. 3.5.1.2 Relative humidity is an expression of the moisture content of a

given atmosphere as a percentage of the saturation humidity at the same temperature. 3.5.1.3 Wet-bulb temperature (WBT) is measured by a hygrometer or a

sling psychrometer and is shown as sloping lines on the psychrometric chart. A status point on the psychrometric chart can be indicated by a pair of dry-bulb temperature (DBT) and WBT.

3

3.5.1.4 Specific volume, in m /kg, is the reciprocal of density and is

indicated by a set of slightly sloping lines on the psychrometric chart. 3.5.1.5 Enthalpy is the heat content of unit mass of the atmosphere, in o

kJ/kg, relative to the heat content of 0 C dry air. It is indicated on the psychrometric chart by a third set of sloping lines, near to, but not quite the same as the web-bulb lines. In order to avoid confusion, there are no lines shown, but external scales are given on two sides. 3.5.1.6 Sensible heat is the heat content causing an increase in dry-bulb

temperature. 3.5.1.7 Latent heat is the heat content due to the presence of water vapour

in the atmosphere. It is the heat which was required to evaporate the given amount of moisture. The terms above were easily evaluated and measured for the difference brought by the system applied to the room through the use of psychrometric chart. Considering that the study centers with the air conditioning system, the effect of the installation at one room will be graphically evaluated to see the air conditioning process. The sensible and latent heat gains were considered in the room. The design cooling load (or heat gain) was the amount of heat energy to be removed from a house by the HVAC equipment to maintain the house at indoor design

temperature. There were two types of cooling loads, namely: sensible cooling load and latent cooling load. The sensible cooling load was related to the dry bulb temperature of the building and the latent cooling load is related to the wet bulb temperature of the building. 3.6 Sensible and Latent Heat Gains from People

One source of sensible and latent heat gains in the computation was from people. It greatly varied from the number of people inside the room and the activities undertaken. The values used for people were taken from carrier system design manual (Carrier 1965). Table 3.1 shows the diversity factors for the different usage of the room. Table 3-2 shows the room heat gain from people. Table 3.1 Typical Diversity Factor for Large Buildings (Carrier 1965)

Table 3.2 Heat Gain From People (Carrier 1965)

The factor used in solving heat load from people: Apartment/Hotel = 0.5 x 390 = 195 (Carrier 1965). The computation can be seen on section B.2 under Appendices. 3.7 Sensible Heat and Latent heat from Light and other Electric Equipment

Appliances that consumed electricity also contributed to the heat gain in the room. Table 3-3 shows the usual power consumption of appliances as well as the rate of usage. Table 3-3 Power consumption of appliances Appliances

Quantity

Wattage

Days per month of consumption

32 110

Time of use per day 6 10

Lights Television 19’’ Electric Fan 14’’

1 1 1

80

12

30

30 30

The values written above are used in the computation of the grand total heat of the room using the carrier’s heat load form. Factor used in the heat load form being Factor = 0.5 (Carrier 1965).

3.8 Soil Temperature Variations with Time and Depth

Soil temperature fluctuates annually and daily and is affected mainly by variations in air temperature and solar radiation. The annual variation of daily average soil temperature at different depths is described with the following sinusoidal function (Hillel 1982), as shown in equation 3.3.

            

    

Where:

(3.3)

o

is the average temperature C o

is the annual amplitude of the surface soil temperature ( C)

z is the soil depth (m) d is the damping depth (m) is the time lag (days)

3.9 Ground Loop Length

Once the room heat load has been determined, the ground loop length can then be determined by using the following equations: 3.9.1 McQuay’s Ground Loop Length

The ground loop is a heat exchanger that is similar to a cooling coil or an evaporator in a chiller. The goal is to transfer energy from the heat pump loop fluid to/from the ground. The purpose of loop design is to estimate the required loop length. Equation 3.4 shows the formula of the heat needed to lower the temperature of the room. (McQuay 2002)

   

Where:

(3.4)

Q is the heat to lower the temperature of the room (W) L is the pipe length (m) tg is the ground temperature (C) tw is the fluid temperature (C) R is the thermal resistance to heat transfer

 

3.9.2 RETScreen’s Ground Heat Exchanger Sizing

Ground heat exchanger sizing is concerned mainly with the determination of heat exchanger length. The method used in the Ground Source Heat Pump (GSHP) Project Model is largely adapted from International Ground-Source Heat Pump Association (IGSHPA) (1988). Equation 3.5 shows the formula of needed length of the pipe. ( RETScreen 1965)

                              

Where: Q is the

(W)

L is the pipe length (m)

COP is the design cooling coefficient of performance, Fc is the part load factor for cooling,

Tae is thedesigned entering air from room temperature Tg is the ground temperature

(3.5)

Rp is the pipe thermal resistance Rs is the soil thermal resistance 3.9.3 Czech Technical University’s Design of earth-to-air heat exchanger loop calculation

The method allows the design of EAHXs. Particularly, the method is beneficial for the preliminary design phase when conceptual variants of building ventilation and cooling are prepared, as shown in equation 3.6. (Pavel Kopecký 1965)

              

Where:

(3.6)

NTU is the number of transfer unit, L is the pipe length (m)

ha is the air-to-pipe convective heat transfer coefficient ro is the internal diameter of pipe (m) ma is the mass air flow rate

Ca is the specific thermal capacity of air

3.10 Mass flow rate of cooling air

The mass flow rate of cooling air needed is shown on equation 3.7.

Where:

  

(3.7)

m is the mass flow rate of air (kg/s)

     

Q is the flow rate ( equation 3.8.



/s), Supply Air Quantity from heat load form, as shown on

is the density of the air (kg/

(3.8)

)

3.11 Measure of comfort: Effective Temperature

Developed by Houghten and Yagloglou at the ASHVE Pittsburgh research laboratories in 1923: represented by a set of equal comfort lines drawn on the psychrometric chart. It is defined as the temperature of a still, saturated atmosphere, which would, in the absence of radiation, produce the same effect as the atmosphere in question. Equation 3.9 shows the formula for the effective temperature (Andris Auliciems and Steven V. Szokolay 1965)

         

(3.9)

Where: ET = effective temperature Dbt = desired room temperature RH = designed room RH

Effective temperature is defined as the temperature of saturated air (RH=100%) at which the subject would experience the same feeling of comfort as experienced in the actual unsaturated environment. It serves as a single parameter for an index of comfort. (C.P.Arora 1965)

CHAPTER 4 METHODOLOGY

This chapter discusses the processes and methods of geothermal cooling that is important in the study as well as the appropriate equipment and pipes to be selected for installation. Figure 4-1 shows the step-by-step procedures that were undertaken by the group.

��

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��, ��

��

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��

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�� /�� (�� )

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Figure 4-1 Flowchart showing the steps taken in the thesis 4.1 Site Selection

In the site selection process, the group had considered the convenience and proximity of the site. The group had chosen a private property located at Limay, Bataan as its location for it was the only place that was available for excavation. The location was the most convenient because the excavation site is owned by the family of Mr. John Luigi Manansala and was the only site available to install a Geothermal Cooling System. The excavation was done by hired and trusted workers from Limay, Bataan. A small room was built on the above mentioned plot of land for the purpose of this study.

4.2 Evaluation of Room Properties

The room was evaluated with the use of equipment and proper standards in evaluating the properties of the room. Evaluation of room properties was important before the installation of the geothermal heat exchanger. It could help the group to select the proper type of materials and specifications of the equipment that were needed in the study. The different parameters measured were the dry bulb temperature, wet bulb temperature, air flow rate, relative humidity, sources of heat gain: light sensible heat, sensible and latent heat gain from people, and other sources of heat gain. The apparatus needed for measuring these parameters were the digital hygrometer for measuring wet bulb temperature, dry bulb temperature and relative humidity of the room, the speedometer for measuring the air flow rate of the intake and discharge pipes, the heat load calculation and the carrier psychometric chart for measuring heat gain and room properties.

4.3 Geothermal Cooling System

The Geothermal Cooling System consists of the three subsystems which are the blower system, piping system and damper system. Figure 4-2 shows the schematic diagram of the Geothermal Cooling System.

Figure 4.2 Schematic Diagram of Geothermal Cooling System The operation of geothermal cooling system as described by the diagram started at the suction of air to the intake pipe. The air was taken to the heat exchanger using the air blower. The air at the heat exchanger would have undergone through a conduction and convection heat transfer process, wherein the air from the room would gradually decrease its temperature after the air passed through the pipes. The air from the underground heat exchanger with a lower temperature will be discharged to the room to be conditioned. The damper operates with the help of the thermostat which serves as a control system for o

an automatic open or close operation. When the room temperature is below 27 C, then the

damper opens itself to let the fresh air enter the room. However, when the room temperature is o

above 27 C, the damper doesn’t open. The air blower also operates with the help of the thermostat. It automatically turns off o

when the temperature inside the room is below 27 C, and it turns itself on if the temperature o

inside the room is above 27 C. For the medium of heat transfer to be used, air was chosen to simplify the geothermal cooling system, since it was free, safe and non-toxic. The air from the room is cooled by passing through the ground which has a lower temperature; this is done by using pipes which will act as heat exchangers. Conduction heat transfer occurs between the heat exchanger and the soil from the ground while convection heat transfer occurs between the heat exchanger and the air flowing inside the pipe. 4.4 Design, selection and fabrication of piping system

The pipe used for the ground loop design was a black iron steel pipe. It was chosen for its durability, thermal conductivity and it was cheaper compared to the other pipes being considered in the design of the piping system. The black iron steel pipe was designed to be a three layer parallel connecting pipes and was made for the passage of air from the room to the ground, hence the heat transfer process would occur at the piping system. The piping system was designed to have three layers, the first layer starts at 6 feet, the second layer at 8 feet and the third layer at 10 feet. The horizontal ground loop piping design was chosen because of the available depth at the selected site and lack of equipment necessary for the depth required in a vertical loop piping

system installation (usually 100 feet). The horizontal ground loop piping system does not require high depth compared to vertical loop. Also, the horizontal set-up was much more ideal for the process and the system would have smaller scales in the pipe. Existing studies show that horizontal piping systems are preferable for residential application. The draining system was placed at the bottom part of the heat exchanger where liquid condensate accumulates. The system was designed to be opened manually using a lever attached to the ball valve and functions through pulling the lever up. The lever was located beside the discharge pipe. Furthermore, the heat exchanger was tilted so that the liquid condensate will reside on the bottom part of the heat exchanger. 4.5 Selection of Air Blower

Selection of blowers was dependent on the system design, on such cases, the piping and the discharge characteristics that determines blower selection. The group identified the internal heat load of the room, room temperature, air flow rate and the pressure head that was necessary in selecting the blower. Along with the parameters considered, computation of flow characteristics to determine the turbulent flow, pressure drop and blower power were done. The electricity consumption of the geothermal cooling system was evaluated based from the single phase motor of the centrifugal air blower.

4.6 Selection of Damper System

The selection of damper system varied with the size of the room and the air flow needed to modify the room’s comforting properties. The damper was mounted to an actuator for an automatic operation. The air flow passing through the damper was set to be at 10% of the total ambient air. The 10% ambient air helped affect the room’s properties such as humidity and temperature to achieve comfort cooling. 4.7 Excavation

The excavation site at Limay, Bataan is owned by the family of Mr. John Luigi Manansala. The design of the excavation was highly dependent on the existing studies that were used in the field of geothermal heat pump such as the standard depth at which the temperature of the soil was most likely effective for the soil conductivity. The total depth of the excavation was 10 feet with 3 layers of horizontal piping system burrowed at 6 feet for the first layer, 8 feet for the second layer and 10 feet for the third layer. Workers were hired to do the excavation. They were able to accomplish the work within one month. Apart from the soil excavation, removal of large stones was necessary and made the work difficult. After the installation of the piping system, the soil was filled back. New soil was added due to the removal of large boulders. No pressure was applied while filling back the soil to avoid damaging the piping system. Hence, the soil still sank and addition of new soil was required.

4.8 Installation of geothermal cooling system and damper

After the excavation and the installation of the piping system, the air blower was mounted to the intake pipe of the piping system. Furthermore, the intake and the discharge pipe was installed to the house. The damper system was installed to the wall of the house and located near the intake pipe of the piping system. The installation helps the cooling process to maintain the effective temperature and promote comfort cooling inside the conditioned room. 4.9 Installation of thermostat controller at air blower and damper for automatic cut on/cut off (For maintaining effective temperature)

The thermostat controller which was attached to both the damper and the centrifugal air blower operates by controlling the voltage input in the actuator of the damper and the single phase motor of the centrifugal air blower. The thermostat controller for the centrifugal air blower was set to have a cut-off of electricity to automatically turn off the motor of air blower when the effective temperature (set temperature) was met. The blower continuously operates when the room temperature does not meet the set temperature that is affixed at the thermostat. The set temperature was modified through the controller. The thermostat controller for the damper is set to have a cut-in voltage to automatically turn on the dampers actuator and to intake fresh air. It is designed to intake 10% of ambient air flow when the room temperature is below the desired temperature (which is the computed effective temperature) and closes when the room temperature is above the desired temperature. The desired temperature for the damper controller was modified through the controller attached to the thermostat.

4.10 Testing and Evaluation of Open Loop Geothermal Cooling System

After the installation of the open loop geothermal cooling system, the group evaluated the effectiveness of the system to the conditioned room for one week. The room’s comfort cooling properties were evaluated using the apparatus which were the digital hygrometer, anemometer, analog thermometer. The digital hygrometer was used for evaluating the air properties of the room after the cooling process such as the dry bulb temperature, wet bulb temperature and relative humidity. The analog thermometer was used for calibration of the digital hygrometer and anemometer. Anemometer was used to measure the air velocity of the evaluated room. Parameters considered for evaluating the effectiveness of the geothermal cooling system were the relative humidity, temperature of the ambient air and temperature of the conditioned room before the system was used for its operation, and also the velocity and temperature of the intake and discharge air flow, the relative humidity and temperature after the geothermal cooling system was operated.

CHAPTER 5 DATA ANALYSIS

This chapter discusses the data and analysis of the tests conducted on the geothermal cooling system. 5.1

Data gathered from operation of Geothermal Cooling System

The group observed the geothermal cooling system for one week. They gathered data in three time intervals to prevent the blower from overheating. The three time intervals were 9-11 am, 1-3 pm, and 5-7 pm. The parameters that were observed are dry bulb temperature, relative humidity, and velocity of air at the suction and discharge ends of the piping system. In naming the parameters, “T” represents the Dry Bulb Temperature. “RH” represents the Relative humidity. “V

intake”

represents the velocity at the suction end of the pipe. “V dis” represents the velocity at the discharge end of the pipe. “Room” signifies that the parameter represented is taken inside the room. “Out” signifies that the parameter represented is taken from ambient surroundings outside the room. “∆T” signifies the difference in temperature, thus “ ∆T1” represents the difference between “Tout-Troom (at start)”. “ ∆T2” represents the difference between “T out-Troom(after 2 hours)”. “ ∆T3” represents the difference between “T intake- Tdis”.

5.1.1

Day 1 Operation

The following data were gathered during the first day of operation. The general weather experienced throughout the day was sunny. The summary of data is shown in Table 5.1. Table 5.1 Data of first day Operation Date Time Weather

Troom, (°C) RHroom, (%) Tout, (°C) RHout, (%) Tintake, (°C) Vintake, (m/s) Tdis, (°C) Vdis, (m/s) Tout - Troom, (°C) Tintake-Tdis, (°C)

7/1/2012 1-3 pm Sunny

9-11 am

5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

28.7 80.5 28.2 80.7 28 2.1 26.3 5.2 0.5 1.7

27.1 85 29.3 77.6 28 2.1 26.3 5.2 2.2 1.7

31.8 78 31.5 75.4 29.5 2.1 27.1 5 0.3 2.4

29.8 79.3 32 76.7 29.5 2.1 27.1 5 2.2 2.4

28.8 85.2 29.3 80.4 28.5 2.1 26.5 5.1 0.5 2

26.8 84.2 28.6 82.3 28.5 2.1 26.5 5.1 1.8 2

The previous data were represented in graphs as shown in Figure(s) 5.1, 5.2, and 5.3.

34

T e m p e r a t u r e ( °C)

32 30 ��

28

�� 26

��

24 22 20

�� 9�� 11��

1��

3��

5��

7��

Figure 5.1 Temperatures during operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. T out increased during the 9-11 am interval and 1-3 pm interval while it decreased during the 5-7 pm interval. T room decreased all throughout the operation. 90 80 T e m p e r a t u r e ( °C)

70 60 ��

50

��

40

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20 10 0

�� 9��

11��

1��

3��

5��

7��

Figure 5.2 Relative humidity and velocity in the intake and discharge pipes

Vintake and Vdis remained constant throughout the operation. RH out decreased during 9-11 am interval while it increased during the 1-3 pm and 5-7 pm interval. 3 2.5 V e l o c i t y (

2 Δ�1

1.5

Δ�2 1 )

Δ�3

0.5

��

0 9��11��

1��3��

5��7��

Figure 5.3 Temperature Differences during Operation There was a minimal temperature difference from T room and Tout at the start of the operation, as represented by ∆T1. ∆T2 is equal and at its highest during the 9-11 am and 1-3 pm. ∆T3 was at its highest during the 1-3 pm interval and lowest during the 9-11 am interval. 5.1.2

Day 2 Operation

The following data were gathered during the second day of operation. The general weather experienced throughout the day was sunny. The summary of data is shown in Table 5.2.

Table 5.4 Data of Second Day Operation Date Time Weather

7/2/2012 1-3 pm Sunny

9-11 am

5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

Troom, (°C) RHroom, (%) Tout, (°C) RHout, (%) Tintake, (°C) Vintake, (m/s) Tdis, (°C) Vdis, (m/s)

29.4 81.7 29.1 80.4 28.4 2.1 26.6 5.2

27.8 80.9 30.2 79.5 28.4 2.1 26.6 5.2

32.6 75 31.2 77.6 29.6 2.1 27.8 5.1

30.5 78.5 32.4 77.5 29.6 2.1 27.8 5.1

28 83.4 27.6 79.6 27.5 2.1 26.3 5

26.8 82.2 27.2 80.2 27.5 2.1 26.3 5

Tout - Troom, (°C)

0.3

2.4

1.4

1.9

0.4

0.4

Tintake-Tdis, (°C)

1.8

1.8

1.8

1.8

1.2

1.2


34 T e m p e r a t u r e ( °C)

32 30 ��

28

��

26

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22 20

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1��

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Figure 5.4 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. T room. . Tout increased during the 9-11 am interval and 1-3

pm interval while it decreased during the 5-7 pm interval. T room decreased throughout the operation.


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5��

7��

Figure 5.5 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out decreased during 1-3 pm interval and 5-7 pm interval while it increased during the 1-3 pm and 5-7 pm interval. RH room decreased during the 9-11 am interval and 5-7 pm interval while it increased during the 1-3 pm interval.

3 2.5 V e l o c i t y (

2 Δ�1

1.5

Δ�2 1

Δ�3

)

0.5 0

�� 9��11��

1��3��

5��7��

Figure 5.6 Temperature Differences during Operation ∆T1 is lowest during 9-11 am and 1-3 pm while it is highest during the 1-3

pm interval. ∆T2 is at its highest during the 9-11 am and at its lowest during the 57 pm interval. ∆T3 is equal during 9-11 am interval and 1-3 pm interval and at its lowest during the 5-7 pm interval. 5.1.3

Day 3 Operation

The following data were gathered during the third day of operation. The general weather experienced throughout the day was rainy. The summary of data is shown in Table 5.3.

Table 5.3 Data of Third Day Operation Date Time Weather

7/3/2012 1-3 pm Rainy

9-11 am


5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

28.2 84.4 29.3 78.5 27.4 2.1 26.3 4.9 1.1 1.1

28.2 79 30.4 80.1 27.4 2.1 26.3 4.9 2.2 1.1

28.6 83.3 30.4 77.1 27.4 2.1 26.1 5.2 1.8 1.3

27.9 74 31.7 79.9 27.4 2.1 26.1 5.2 3.8 1.3

28.3 85.8 27.8 82.3 26.9 2.1 26.2 5.1 0.5 0.7

28.1 83 27.6 83.3 26.9 2.1 26.2 5.1 0.5 0.7



32 30 ��

28

�� 26

��

24

��

22

��

20 9��

11��

1��

3��

5��

7��

Figure 5.7 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. T out increased during the 9-11 am interval and 1-3 pm

interval while it decreased during the 5-7 pm interval. T room decreased all throughout the operation.

100 90 T e m p e r a t u r e ( °C)

80 70 60

��

50

��

40

��

30

��

20 10

��

0 9��

11��

1��

3��

5��

7��

Figure 5.8 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out increased throughout the whole operation. RH room decreased throughout the operation.

4 3.5 V e l o c i t y (

3 2.5 Δ�1

2

Δ�2 1.5 )

Δ�3

1 0.5 0

�� 9��11��

1��3��

5��7��

Figure 5.9 Temperature Differences during Operation ∆T1 was at its highest during the 1-3 pm interval while it was at its lowest

during the 5-7 pm interval. ∆T2 was at its highest during the 1-3 pm interval while it was at its lowest during the 5-7 pm interval. ∆T3 was at its highest during the 13 pm interval while it was at its lowest during the 5-7 pm interval. 5.1.4

Day 4 Operation

The following data were gathered during the fourth day of operation. The general weather experienced throughout the day was rainy. The summary of data is shown in Table 5.4.

Table 5.4 Data of Fourth Day Operation Date Time Weather

7/4/2012 1-3 pm Rainy

9-11 am


5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

27.7 86.3 28.4 80.7 27.3 2.1 25.6 4.8 0.7 1.7

27.1 87 29.8 78.9 27.3 2.1 25.6 4.8 2.7 1.7

29.7 80.8 31.3 77.8 28.4 2.1 26.4 5.1 1.6 2

28.1 82.1 30.2 76.1 28.4 2.1 26.4 5.1 2.1 2

28.8 83.5 27.9 79.6 27.8 2.1 25.5 4.4 0.9 2.3

27.1 79.3 27.8 82 27.8 2.1 25.5 4.4 0.7 2.3

The previous data were represented in graphs as shown in Figure(s) 5.10, 5.11, and 5.12. 32 T e m p e r a t u r e ( °C)

30 28 �� 26

��

24 �� 22 20

�� 9��

11��

1��

3��

5��

7��

Figure 5.10 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. Tout increased during the 9-11 am interval and 1-3 pm

interval while it decreased during the 5-7 pm interval. T room decreased all throughout the operation. 100 T e m p e r a t u r e ( °C)

90 80 70 60

��

50

��

40

��

30

��

20 10

��

0 9��

11��

1��

3��

5��

7��

Figure 5.11 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out decreased during the 9-11 am and the 1-3 pm interval while it increased during the 5-7 pm interval. RH room increased during the 9-11 am interval and the 1-3 pm interval while it decreased during the 5-7 pm interval.

3

2.5 V e l o c i t y

2 Δ�1

1.5

Δ�2 Δ�3

1 (

)

0.5

��

0 9��11��

1��3��

5��7��

Figure 5.12 Temperature Differences during Operation ∆T1 was at its highest during the 1-3 pm interval and was at its lowest

during the 9-11 am interval. ∆T2 was at its highest during the 9-11 am interval and was at its lowest during the 5-7 pm interval. ∆T3 was at its highest during the 5-7 pm interval and was at its lowest during the 9-11 am interval. 5.1.5

Day 5 Operation

The following data were gathered during the fifth day of operation. The general weather experienced throughout the day was rainy. The summary of data is shown in Table 5.5.

Table 5.5 Data of Fifth Day Operation Date Time Climate

7/5/2012 1-3 pm Rainy

9-11 am


5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

27.7 82.1 29.3 77 27.2 2.1 26.5 5.2 1.6 0.7

27.3 76.3 30 79.4 27.2 2.1 26.5 5.2 2.7 0.7

28.1 85 30.5 77.4 27.3 2.1 26.4 5 2.4 0.9

27.1 77.6 29.6 76.2 27.3 2.1 26.4 5 2.5 0.9

28.7 84.2 28.9 77.3 26.5 2.1 25.9 4.9 0.2 0.6

27.5 83 27.7 79.2 26.5 2.1 25.9 4.9 0.2 0.6

The previous data were represented in graphs as shown in Figure(s) 5.13, 5.14, and 5.15. 31 30 T e m p e r a t u r e ( °C)

29 28

��

27

��

26

��

25 24 23

�� 9��

11��

1��

3��

5��

7��

Figure 5.13 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. Tout increased during the 9-11 am interval while it decreased

during the 1-3 pm interval and the 5-7 pm interval. T room decreased all throughout the operation.


80 70 60 ��

50

��

40

�� 30 �� 20 10

��

0 9��

11��

1��

3��

5��

7��

Figure 5.14 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out decreased during the 1-3 pm interval while it increased during the 9-11 am and 57 pm interval. RHroom decreased throughout the operation.

3

2.5

V e l o c i t y (

2 Δ�1

1.5

Δ�2 )

Δ�3

1

0.5

��

0 9��11��

1��3��

5��7��

Figure 5.15 Temperature Differences during Operation ∆T1 was at its highest during the 1-3 pm interval and was at its lowest

during the 5-7 pm interval. ∆T2 was at its highest during the 9-11 am interval and was at its lowest during the 5-7 pm interval. ∆T3 was at its highest during the 1-3 pm interval and was at its lowest during the 5-7 pm interval. 5.1.6

Day 6 Operation

The following data were gathered during the sixth day of operation. The general weather experienced throughout the day was sunny. The summary of data is shown in Table 5.6.

Table 5.6 Data of Sixth Day Operation Date Time Weather

7/6/2012 1-3 pm Sunny

9-11 am


5-7 pm

At Start

After 2 Hours

At Start

After 2 Hours

At Start

After 2 Hours

28.2 80.1 28.1 80 27.3 2.1 25.2 5 0.1 2.1

27.3 79.8 29.9 79.3 27.3 2.1 25.2 5 2.6 2.1

31.7 73.5 29.7 78.2 29.7 2.1 27.3 5.2 2 2.4

29.4 75.7 29.2 80.1 29.7 2.1 27.3 5.2 0.2 2.4

28.4 82.2 28.2 80.8 27.1 2.1 25.3 5.2 0.2 1.8

27.1 81.4 27.7 81.5 27.1 2.1 25.3 5.2 0.6 1.8



32 30 ��

28

�� 26

��

24

��

22 20

�� 9��

11��

1��

3��

5��

7��

Figure 5.16 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. Tout increased during the 9-11 am interval while it decreased

during 1-3 pm interval and the 5-7 pm interval. T room decreased all throughout the operation. 90 T e m p e r a t u r e ( °C)

80 70 60 ��

50

��

40

�� 30 �� 20 10 0

�� 9��

11��

1��

3��

5��

7��

Figure 5.17 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out decreased during 9-11 am interval while it increased during the 1-3 pm and 5-7 pm interval. RHroom decreased during the 9-11 am interval and the 5-7 pm interval while it increased during the 1-3 pm interval.

3

2.5

V e l o c i t y (

2 Δ�1

1.5

Δ�2 )

Δ�3

1

0.5

0

�� 9��11��

1��3��

5��7��

Figure 5.18 Temperature Differences during Operation ∆T1 was at its highest during the 1-3 pm interval while it was at its lowest

during the 9-11 am interval. ∆T2 was at its highest during the 9-11 am interval while it was at its lowest during the 1-3 pm interval. ∆T3 was at its highest during the 1-3 pm interval while it was at its lowest during the 5-7 pm interval. 5.1.7

Day 7 Operation

The following data were gathered during the seventh day of operation. The general weather experienced throughout the day was sunny. The summary of data is shown in Table 5.7.

Table 5.7 Data of Seventh Day Operation ��

7/7/2012 1�3 ��

9�11 ��

5�7 ��

�� 2 �� 2 �� 2 ��


29 76.9 29.4 77.3 28.5 2.1 26.4 5.1 0.4 2.1

28.1 78.3 31.3 79 28.5 2.1 26.4 5.1 1.3 2.1

30.4 75.7 30.8 76.4 29.9 2.1 27.4 4.9 0.4 2.5

28.6 78.3 31.5 77.8 29.9 2.1 27.4 4.9 2.2 2.5

28.8 83.2 27.9 78.4 27.2 2.1 25.9 5 0.9 1.3

27.5 80.8 26.8 80.4 27.2 2.1 25.9 5 0.4 1.3

The previous data were represented in graphs as shown in Figure(s) 5.19, 5.20, and 5.21. 34 T e m p e r a t u r e ( °C)

32 30 ��

28

�� 26

��

24

��

22 20

�� 9��

11��

1��

3��

5��

7��

Figure 5.19 Temperatures during Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. T out increased during the 9-11 am interval and 1-3 pm

interval while it decreased during the 5-7 pm interval. T room decreased all throughout the operation.


80 70 60 ��

50

��

40

�� 30 �� 20 10 0

�� 9��

11��

1��

3��

5��

7��

Figure 5.20 Relative humidity and velocity in the intake and discharge pipes Vintake and Vdis remained constant throughout the operation. RH out increased throughout the operation. RH room increased during the 9-11 am interval and the 1-3 pm interval while it decreased during the 5-7 pm interval.

3.5 3

V e l o c i t y (

2.5 2

Δ�1 Δ�2

1.5 )

Δ�3 1 0.5 0

�� 9��11��

1��3��

5��7��

Figure 5.21 Temperature Differences during Operation ∆T1 was at its highest during the 5-7 pm interval. ∆T2 was at its highest

during the 1-3 pm interval while it was at its lowest during the 5-7 pm interval. ∆T3 was at its highest during the 1-3 pm interval while it was at its lowest during

the 5-7 pm interval.

5.1.8

Average for One Week Operation

Table 5.8 Average Data of Seven-Day Operation Date

Average

Time

9-11 am

1-3 pm

Weather

5-7 pm

Sunny After 2 At Start Hours 30.41429 28.77143

28.54286

After 2 Hours 27.27143

Troom, (°C)

28.41429

After 2 Hours 27.55714

RHroom, (%)

81.71429

80.9

78.75714

77.92857

83.92857

81.98571

Tout, (°C)

28.82857

29.85714

30.77143

30.84286

28.22857

27.78571

RHout, (%)

79.22857

79.11429

77.12857

77.75714

79.77143

81.27143

Tintake, (°C)

27.72857

27.72857

28.82857

28.82857

27.52857

27.52857

Vintake, (m/s)

2.1

2.1

2.1

2.1

2.1

2.1

Tdis, (°C)

26.12857

26.12857

26.92857

26.92857

25.94286

25.94286

Vdis, (m/s)

5.057143

5.057143

5.071429

5.071429

4.957143

4.957143

Tout - Troom, (°C) Tintake-Tdis, (°C)

0.414286 1.6

2.3 1.6

0.357143 1.9

2.071429 1.9

0.314286 1.585714

0.514286 1.585714

At Start

At Start

The average data were represented in graphs as shown in Figure(s) 5.22, 5.23, 5.24.


31 30 29 ��

28

��

27

�� 26 �� 25 24 23

�� 9��

11��

1��

3��

5��

7��

Figure 5.22 Average Temperatures for Seven-Day Operation Tintake and Tdis remained constant throughout the operation of the geothermal cooling. T out increased during the 9-11 am interval and 1-3 pm interval while it decreased during the 5-7 pm interval. T room decreased all throughout the operation. Based on the graph above, the geothermal cooling system can successfully decrease the temperature of the room after a continuous operation for 2 hours, regardless of the temperature of the ambient or outside air.


80 70 60 ��

50

��

40

�� 30 �� 20 10 0

�� 9��

11��

1��

3��

5��

7��

Figure 5.23 Average RH and Velocity for Seven-Day Operation Vintake and Vdis remained constant throughout the operation. RH out decreased during 9-11 am interval while it increased during the 1-3 pm and 5-7 pm interval. RHroom decreased throughout the operation. Based on the graph, the average RH room decreases throughout the operation. V intake and Vdis does not affect the RH room based on the graph.

2.5 V e l o c i t y (

2

1.5 Δ�1 Δ�2

1

Δ�3

)

0.5

��

0 9��11��

1��3��

5��7��

Figure 5.24 Average Temperature Differences for Seven-Day Operation There was a minimal temperature difference from T room and Tout at the start of the operation, as shown from the graph. ∆T2 was at its highest during the 9-11am interval while it was at its lowest during the 5-7pm interval. ∆T3 was at its highest during the 1-3pm interval and was its lowest during the 5-7pm interval. 5.2 Computation of Payoff Period (Using ROI)

This section shows the comparison of the geothermal cooling system and conventional air-conditioning under the operation of 6 hours in one day. Table 5.9 shows the power consumption, capital cost, and monthly operational cost. Table 5.9 Data Comparison of Geothermal Cooling System and Conventional AirConditioning Unit For Computing Payoff Period

A. Power Consumption, (HP) B.Capital Cost Initial Cost, peso Labor Cost, peso C. Monthly Operational Cost, peso

Geothermal Cooling System 0.75

Air-conditioning System 1.27

21716 14000 571.809

12000 n/a 964.768

Geothermal cooling system used a centrifugal air blower with a power consumption of 0.75 HP. It was compared to conventional air-conditioning system with a power consumption of 1.27 HP which was the recommended air-conditioning unit for an 8ft X 10ft floor plan. The comparisons of the two systems were observed under the operation of six hours (interval of two hours) in one day for a whole month. The initial cost of the geothermal cooling system, composing of three subsystems, was P21726.00, as compared to an air-conditioning unit with an initial cost of P12000.00. The labor cost for geothermal cooling system was P14000.00 which included the excavation, assembly, and other labor works. With this, the monthly operational cost for an installed geothermal cooling system was computed to P571.809.00 while air-conditioning system was computed to P964.768.00. The computation was done using MERALCO monthly estimated computation. This proves that the geothermal cooling system, based from power consumption, costs less. The payoff period was 66.396 months. It was based from the computation using breakeven analysis as shown from Computation of Pay-off Period using Break-Even Analysis for Geothermal Cooling System at Appendix A.6.

CHAPTER 6 CONCLUSION AND RECOMMENDATION

This section discusses the conclusion and recommendation after the accomplishment of the study. 6.1 Conclusion

The group was able to design, fabricate, install and test an open loop geothermal cooling system with an automatic temperature control using thermostat for the centrifugal air blower and the damper with actuator in a controlled room for residential house application. Weather conditions were a huge factor during the excavation since the work was done outdoors. The excavation took one month due to removal of big rocks. During the installation of the pipes, rains were imminent which added difficulty on the process. The selection of the site was highly dependent on the availability of the lot on where the excavation and the installation will be done and therefore, the group was not able to install the geothermal cooling system at a more suitable site. Measurement and evaluation of the room and ambient properties before the installation were successfully done and were used throughout the computation. The design of geothermal cooling system was done with the aid of heat load calculations and carrier handbook manual. Measurements were done using hygrometer which measured relative humidity and analog thermometer which measured the ambient and room temperatures. The design of the Geothermal Cooling System started with the design of the heat exchanger which is also the piping system. The computation of total length of the pipe was done

using the standards that was gathered by the group from previous existing studies and was included to the study’s reference. Fabrication was done in a machine shop near the site to ensure that every small detail was being followed and finished on time. The installation of the heat exchanger was not a problem for the group since the group hired a heavy equipment boom truck to help with the installation. The selection of the centrifugal air blower was based on the computation done by the group. Its performance capacity was evaluated by its computed output power, pressure head and velocity. Installation of the centrifugal air blower was done by mounting the suction pipe and discharge pipe to the room. The centrifugal air blower was located outside the house due to the design of the piping system. After the installation of the centrifugal air blower which completed geothermal cooling system, the addition of a thermostat controller added further the efficiency of the single phase motor. The thermostat controller system that was connected to the motor was fabricated and designed for automatic cut off and cut on of the voltage supply. The thermostat controller cuts off the voltage supply when the cooling system meets the set temperature that is considered for comfort cooling. This completes the process of cooling the room by taking air from the room using a centrifugal pump, taking it to a designed piping system and bringing it back to the room at a lower temperature. In the completion of the study, it was necessary for the addition of a damper with an actuator controlled by a thermostat for automatic cut on/cut off of voltage.

The damper served

as a heater by introducing a hot air to maintain the effective temperature designed for comfort cooling. The design temperature of the room was 27°C with a relative humidity of 60%. However, based from studies, comfort cooling was evaluated mainly by one parameter which was the effective temperature. The effective temperature computed was 25°C. The damper was

designed to have a cut on when the temperature of the room reached below this temperature to maintain the effective temperature throughout the process and maintain a comfort cooling regardless of the relative humidity. The geothermal cooling system was able to bring down the temperature inside the room by taking the air from the room and let the air pass through the heat exchanger that was designed to remove heat from the air, through conduction and convection heat transfer, and putting it back on the room. Through this continuous process, the design heat exchanger can lower the temperature of the room at 2°C at most. The evaluation of the soil temperature was based from existing studies and was proved to provide a consistent temperature regardless of the ambient temperature throughout the week of evaluation. It maintained an approximate temperature change of 2°C between the suction and discharge temperature at the start of the operation. By comparing the capital cost and monthly operational cost of a conventional 1.27 HP window type air conditioning unit versus the installed geothermal cooling system (based from power consumption), the group was able to get an approximation on how long will the investment return by break-even analysis. The payback period was calculated to be 67 months. After that period of time, the geothermal cooling system will be able to cool the room at a rate much cheaper than a conventional AC unit.

6.2 Recommendation

For further improvement of the study of the geothermal cooling system, several suggestions were gathered after the evaluation of the system. The system must be constructed during the dry season. If the system is constructed during the rainy season, problems with the digging will be experienced because water may cause hindrance for the workers. Before the piping system installation, it is highly advisable for the fabricated pipes to undergo a hydrostatic test before placing it at the excavated lot. Hydrostatic test is a test which involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified test pressure. This will ensure that there are no defective parts in the pipe which could lead to leakage. After the pipe is placed under the earth, the soil must be left to subside naturally. If the soil is compressed by force, the pipe will experience undue damages. The same with what the group did, it is recommended to put a foundation to the piping system because the soil, after excavation and removal of stones for efficient conduction heat transfer weakened when the soil was dug. It is required to place a drain section in the pipe to remove the water present in the pipe due to condensation. The placement of the drain pipe must be secured in order to prevent the water from entering the pipes through soil. The damper should be placed near the suction fan to let the fresh air enter the room instead of using induced fan. However, for a more effective fresh air flow, use an induced fan. Induced fan should be attached along with the damper’s actuator to the thermostat controller so that they can turn on and off at the same time as the damper.

The soil conditions should be considered in choosing the site because the type of soil present will also affect the ground temperature and the rate of heat transfer between the soil and the induced air flow. In site selection, the place where the excavation was done was the only available vacant slot that the group could find and was therefore the site chosen to where the system is to be installed and evaluated. It is recommended to do the installation near a water source to improve the cooling effect of the geothermal cooling system. The group only based the calculated values based on current studies and available equipment to properly evaluate the soil conductivity, temperature, stability and other properties such as thermocouple and parameter.

APPENDICES: A. Computation for Geothermal Cooling System

                                          A.1 Data:

Ambient Air Properties;

Solving for CFM(Air Flow)

                                     Q = Supply Air Quantity from heat load form

Solving for the temperature entering and leaving the heat exchanger

By temperature balance: mR TR + mOTO = mm Tm

; mm = mR + mO

mR TR + mOTO = (mR + mO) Tm Tm =

 

Solving for m R;

mR = mdR + mvR

     

mdR= =

mvR = mdR (ωR) = 11.9031 mR = mdR + mvR = 11.9031

    

= 11.9031

(0.0136

+ 0.16188

Solving for mO;

) = 0.16188

= 12.06498

mO = mdO + mvO

                mdO= =

= 1.2757

mvO = mdO (ωO) = 1.2757

mO = mdO + mvO = 1.2757 Solving for T m; Tm =

Tm =

Tm = 81.8472°F = 27.6929°C

(0.021

+ 0.02679

) = 0.02679

= 1.30249

Solving for Temperature leaving Heat Exchanger:

                                                                        Solving for Temperature leaving 1 layer Heat Exchanger

Using 1 layer:

Solving for heat surface area in 1 layer:

; The heat a 1layer can remove

where

where

= thermal conductivity of GI pipe =

                                                                                                             ;

; Area of Heat Transfer at 1 layer

Solving for temperature leaving at 3 layers

; Constant number of pipe at 3 layers

st

Solving for the heat the 1 layer can remove with

nd


                                                                                  nd

(Temperature leaving at 2 layer) rd


rd

(Temperature leaving at 3 layer);Final temperature 3 layers can supply

Total

;

Data of B.I. Pipe:

= outside diameter = 3.5in;

= inside diameter = 3.068in; =

Circumference = 0.23939m

= thermal conductivity of B.I. pipe =

Total resistance:

For

;

                                                                                   where

;

For

;

where

= outside diameter = 3.5in

= inside diameter = 3.068in =

= thermal conductivity of GI pipe =

RT=

RT= 0.06737

+



     For

;

                                                        where

S = conduction shape factor of the pipe =

where

d = total depth d = depth +

= 10ft +

= 10.1458ft

= outside diameter

= thermal conductivity =

(clay and sand)

= 1.27307

A.2 Air Blower Selection:

where

where

= 3.09249m

                                                                                     

First, define the flow characteristic (Turbulent or laminar flow)

where

to solve for for turbulent flow;

where

                                       Solving for pressure drop;

Solving for blower power;

A.3 Soil Temperature Calculation:

                          Thermal diffusivity:

= thermal diffusivity

= thermal conductivity (W/(m·K)) = density (kg/m³)

= specific heat capacity (J/(kg·K))

Damping depth:

                                                                                                   Soil temperature

o

= average temperature C

o

= annual amplitude of the surface soil temperature ( C)

z = soil depth (m)

d = damping depth (m)

= time lag (days)

o

•

20 C average soil temp

•

34.11 C air temp

•

3.048m = 10ft

o

     A.5 Length Calculation: st

1 length computation:

Solving for L:

     

                       where

= ground temperature = 19°C

= supply to pump= 27.6929°C

L=



  

  

L= L

                                                          nd

2 length computation:

where:

Assumption:

A horizontal GHX(geothermal heat exchange) consists of a series of pipes laid out in trenches, usually one to two meters below the surface.Typically, about 35 to 55 meters of pipe are installed per kW of heating /cooling capacity.

                 rd

3 length calculation:

-

                                Using;

Theoretically, we should increase NTU as much as possible to increase the exchanger efficiency. It would lead to a combination of minimal airflow rate and a very long pipe. However, when a certain value of NTU (2.0 – 2.5) is reached, there is only a minor gain in efficiency. Therefore, NTU should be higher than 1.2, but it should not exceed2.5. Such a range leads to efficiency from 70 % to92 %.

                         

*EAHX efficiency ηZVT[-] represents how much the outlet air temperature comes close to the internal pipe surface temperature. Solving for efficiency;

    

A.6 Computation of Pay-off Period using Break-Even Analysis for Geothermal Cooling System:

Initial Cost (includes materials and labor) = 21716 peso Labor Cost = 14000 peso

                          Yearly electrical cost when Geothermal Cooling System is in operation:

Cost of 1 hp Air-conditioning Unit: Initial Cost: 12000 pesos

                                                          Yearly electrical cost when 1 hp Air-conditioning unit is installed:

To compute how many years will it take to get back the Investment:

Where n is the no of years

After isolating n, the equation becomes

                        

Where:

FC1 is the total cost of Geothermal Cooling System FC2 is the total cost of Conventional Air-conditioning Unit A1 is the yearly electrical cost of Geothermal Cooling System A2 is the yearly electrical cost of Conventional Air-conditioning Unit i is the inflation rate (average year-to-date inflation rate for June is 3%,

source: http://www.bsp.gov.ph/publications/media.asp?id=2913 ) Substituting the terms,

                                        

B. Heat Load Form and Computation B.1 Heat Load Form

Prepared by :

Date

:

Name of Job :

Prop. No.

:

A p p r o ve

:

Space used f : Siz e : ITEM

7

x

8

=

54

7

SUN GAIN OR Temp.

AREA OR QUANTITY

=

378

FACTOR

cu. ft. BTU/HO UR

16 16

SQ. FT. SQ. FT. SQ. FT. SQ. FT. SQ. FT.

x x x x x

14 25

x x x x x

1 1

224.00 400.00 0.00 0.00 0.00

SQ. FT. SQ. FT. SQ. FT. SQ. FT. SQ. FT. SQ. FT.

x x x x x x

local time

Peak Load

Sun time

sun time

CONDITIONS

DB F

WB F

%RH %

Outdoor (OA)

93.4

81.9

60

147

Room (RM)

80.6

70.2

60

95

Difference

12.8

XXX

XXX

SOLAR & TRANS. GAIN - WALLS & ROOF WALLS 48 WALLS 59 WALLS 80 WALLS 48 ROOF-SUN 80 ROOF-SHADED

local time

Estimate for Hours of Operation

SOLAR GAIN -LOSS GLASS GLASS GLASS GLASS SKYLIGHT

:

1.5 0.6 1 0.5 6.4

x x x x x x

0.26 0.26 0.26 0.26 0.26

18.72 9.20 20.80 6.24 133.12 0.00

DP

GR/LB

XX X

52

FM/PERSO CFM/SQ. FT 26.2

= =

26.2 0

FM/PERSO CFM/DOOR 0 CFM/ FEET 0

= =

0 0

=

0

OUTDOOR AIR 2 0

VENTILATION

PEOPLE x SQ. FT. x CFM V ENTILATION =

13.1 0

TRANS. GAIN - EXCEPT WALLS & ROOF ALL GLASS PARTITION CEILING FLOOR INFILTRATION

SQ. FT. SQ. FT. SQ. FT. SQ. FT. CFM

80

x x x x x

x x x x x

52.8

0.00 0.00 0.00 929.28 0.00

0.22

2

PEOPLE HP OR kW WATTS

20

195 3

x 0.5

190

1

SUBTOTAL STORAGE

SQ. FT

INFILTRATION

x

390.00 0.00 85.00 95.00 0.00 2311.36

) SUBTOTAL

0.00 2311.36 231.14

R O O M S E N S I B LE H E A T

2542.50

0.00

SAFETY FACTOR

0.1

EFFECTIVE SENS. HEAT ESHF

ESHF

SUPP LY DUCT LEAK CFM x

+ %

OUTDOOR AIR

26.2

+ %

FAN H.P.

F x

6.26

TEMP RISE

(

1

D E HU M C F M

0.1

% 1.08

Gr/lb x 195

PEOPLE

190

0.5 x

CFM x

OUTDOOR AIR

95.00 0.00 0.00

Gr/ l x SUBTOTAL

485.00

0.1

48.50

ROOM LATENT HEAT % BF Gr/lbs x

533.50

SAFETY FACTOR SUPPLY DUCT LEAKAGE

DEHUMIDIFIED AIR QUANTITY BF)

F

0

F)

=

=

CFMda

=

F(rm-outlet)

x ROOMSENSIBLEHEAT

1.08

x

2560.21

0.00 390.00 0.00

LB-HR

0.001

SELECTED ADP =

S U P P LY A I R Q U A N T I T Y

CFM

SQ. FT x

APPARATUS DEW POINT 2560.21 EFFECTIV E ROOM SENS. HEAT = 3093.7137 EFFECTIVE ROOM TOTAL HEAT = 0.83

17.71

S U P P LY C F M

2

CFM

0.00

x

LATENT HEAT

APPLIANCES ETC. ADDITIONAL HEAT GAINS VAPOR TRANS

26.2

FFECTIVE ROOM SENS. HEAT

OUTLET TEMP DIFF

E F F E C T I V E R O O M S E N S I B LE H E A T

INFILTRATION PEOPLE STEAM

0

INDICATED ADP

AD P

1.08 SUPPL Y DUCT HEAT

0

CFM OUTDOOR AIR THRU OPERATION =

INTERNAL HEAT PEOPLE POWER LIGHTS APPLIANCES ETC. ADDITIONAL HEAT GAINS

SWINGING REVOLVING OPEN DOORS 0 EXHAUST FAN CRACK 0 CFM INFILTRATION =

2542.5 1.08

OOM SENSIB LE HEA x 12.8 -

D E HU M C F M

ED B

=

183.920

CFM sa

CFMda

R E S U L T I N G E N T . & LV G C O N D I T I O N S A T A P P A R A T U S Trm F+ CFM oa F - Trm Tedb 0.00

LDB

=

Tad

0

F

CFM

F+

BF

FROM PSYCH. CHART:

F - Tadp

0

F

Tldb

F

F

0.00

EFFECTIVE ROOM LATENT HEAT

533.50

E F F E C T I V E R O O M T O T A L HE A T

3093.71

RC

=

GTH 12000

=

0.3514

OTAL AREA

180 0.3514

tons

OUTOOOR AIR HEAT SQ. FT 26.2 26.2

SENSIBLE

LATENT

RETU RN DUCT

FM FM +

%

RE TU RN

6.26 60.09

F x ( Gr/ lbs x ( + %

0.9 BF) 0 .9 BF) HP PUM P

1.08 0.68

159.42 963.51

SUBTOTAL +

DENU M

%

G R A N D T O T A L H EA T

1122.93 0.00

4216.64

LB

=

RC

=

512.26

sq. ft ton

B.2 Computation of Heat Load (without geothermal cooling) Outside Conditions: Temperature: 34.11 C or 93.4 F %RH = 60% Room Conditions (desired): Temperature: 27 C or 80.6 F %RH = 60%

  

Room Conditions (hygrometer): Temperature: or 92.12 F %RH = 60% Room Dimension: Length = 7 feet Width = 8 feet Height = 9 feet Windows and Doors: South Window: Length x Height 2 (4 ft x 4 ft) = 16 ft

North Window: Length x Height 2 (4 ft x 4 ft) = 16 ft East Door:

Width x Height 2 (4 ft x 4 ft) + (7ft x 3ft) = 37 ft

Glass factor = 1.00 from Table 16, page 52; Carrier System Design Manual Exposure Sun Gain for the Month of April South 14 North 25 Table 6 Equivalent Temperature Difference page 30 Walls:

South Wall:

Width x Height 2 2 (8 ft x 8 ft) – (16 ft ) = 48 ft

East Wall:

Length x Height 2 2 (10 ft x 8 ft) – (21 ft ) = 59 ft

West Wall:

Length x Height 2 (10 ft x 8 ft) = 80 ft

North Wall:

Width x Height

2

1

2

(8 ft x 8 ft) – 16ft = 48ft

 

( in. thick), Concrete (Sand and Gravel) from Table 25, page 69; Carrier System Design



Manual

Wall factor = 0.26 for in insulation board from Table 25, page 69; Carrier System Design Manual

         

Exposure

Weight of Wall (

Sun Time (2pm)

South

1

1.5

East

1

0.6

West

1

1

North

1

0.5

Table 19 Equivalent Temperature Difference page 62 Roof:

Length x Width 2 (10 ft x 8 ft) = 80 ft

2

 



( in. thick), Sheet Metal from Table 28, page 72; Carrier System Design Manual

Roof factor = 0.26 for in insulation board from Table 28, page 72; Carrier System Design Manual

Sun Gain (roof) = 6.4 from Table 20 at 2 Manual



(Exposed to sun), page 63; Carrier System Design

Floor:

7

 

(Length x Width) 2 (10 ft x 8 ft) = 80 ft

( in. thick), plywood from Table 29, page 73; Carrier System Design Manual

Factor = 0.22 for no insulation Table 29, page 73; Carrier System Design Manual Heat Gain = (Area, sq. ft.) x (U value) x (outdoor temp. – inside temp – 5 F) 2 Heat Gain = (80 ft ) x (0.22) x (86 F – 78 F – 5 F) Heat Gain = 52.8

Internal Heat:

People: Apartment/Hotel = 0.5(Table 14, page 38) x 390(Table 48, page 100) = 195 Appliances

Quantity

Wattage

Time of use per day 6 10

Days per month of consumption

Lights 1 32 30 Television 1 110 30 19’’ Electric Fan 1 80 12 30 14’’ Factor = 0.5 (recommended value) table 50, page 101; Carrier System Design Manual

B.3Psychrometric Chart 5 3 . r 0 i e r a u r y t s d i o f m o f d o n s u d o n p u r o e P p



r e i r u a t y r s d i o f m o f d o n s u n o i a r p G r e p

0 4 . 0

5 2 0 .

0 8 1

4 2 0 .

0 7 1



5 4 . 0

3 2 0 .

2 2 0 .

0 6 1

1 2 0 .

0 5 1

0 5 . 0

0 2 0 .

5 5 . 0

9 1 0 .

0 4 1

8 1 0 .

0 6 . 0

7 1 0 .

6 1 0 .

0 2 1

0 3 1

5 6 . 0

0 7 . 0

5 1 0 .

0 1 1

5 0 5 0 5 0 7 . 8 . 8 . 9 . 9 . 0 . 0 0 0 0 0 1

4 1 0 .

3 1 0 .

0 0 1

2 1 0 .

0 9

1 1 0 .

0 8



e l b t r i o s a t n c e e a S H F

0 1 0 .

9 0 0 .

0 7

8 0 0 .

7 0 0 .

0 6

6 0 0 .

0 5

5 0 0 .

0 4

4 0 0 .

3 0 0 .

0 3

2 0 0 .

0 2

1 0 0 .

0 1

0 0 0 . 0 1 1 0 5 0 1

r i a y r d f o d n u o p r e p u t B n o i t a i v e d y p l a h t n E - u t B 3 . 0 0 0 1

1 4. 5 r i a y r d f o d n u o p r e p u t B , n o i t �� 14.4167 a r u t a s t a y p l a h t n E

u t B 2 . 0 -

A O

5 9

0 9

 0 8

9 4

Y T I D I M U H E V I T A L E R % 0 1

% 0 2

% 0 3

% 0 4

% 0 5

% 0 6

% 0 7

% 0 8

% 0 9

8 4

I R R Y A B. D E R L T. P F . - C U U M E V O L 1 4 .0

E R U T X I M M O O R

u t B 1 . 0

5 8

m o c . e r a w t f o s n w o d s d n a h . w w w , E R A W T F O S N W��93.4 O D S D N A H : y b t r a h C

DBmx=81.84 ��80.6

0 8

5 7

7 4 6 4

� ��

5 4

5 7

13.9062

4 4

u t B 8 0 . -

3 4 2 4

��81.9

1 4

u t B 6 0 . -

0 7

0 4 9 3

0 7

1 3. 5

��66.8

u t B 4 0 . -

8 3 7 3 6 3

5 6

5 3

5 6

u t B 2 0 . -

4 3 3 3

G H . n i 1 2 e 9 . r 9 u 2 t : E a C r R I U R e S T p S E E m R M e L P E O T s C V I R R l t i E T T a H n L E R M C m U A r A O Y H o S P E R A P C N I S B

��70.2

0 6

2 3 1 3

0 6

0 3 9 2 8 2

5 5

7 2 5 5

1 3. 0 0 5 0 5

6 2

u t B 4 . 0

5 2 4 2 3 2

u t B 3 . 0

5 4

2 2 1 2

5 4

0 2 u t B

9 1

0 4

2 . 0

0 4 u t B 1 . 0

1 2. 5

5 3

8 1

5 3

7 1 6 1

0 3

5 1 4 1

0 3

3 1 2 1

5 2

5 2

1 1

0 1

0 2  F  F

9 8 7

r e o r u t n t b n o r a l i i t u o e a p B p r - u t t m e w e a e W D S T

. e c i r o f e r a s e n i l n o i t a i v e d y p l a h t n e d n a s e i t r e p o r p , F 2 3 w o l e B

e r u t a b r l e u p B - m y r e D T

C. Pictures of the Geothermal Cooling System

C.1 outside View of House (Without the Damper System)

C.2 Excavation of Soil

�

C.3 Fabricated Piping System (Heat Exchanger)

C.4 Mounting of piping system to Centrifugal Air Blower

�

C.5 Discharge Pipe and Suction Pipe (Centrifugal Air Blower at Suction Pipe)

C.6 Installation of Damper System and Thermostat Control for Centrifugal Air Blower’s Single Phase Motor and Actuator of Damper System

�

REFERENCES:

[1] “Geothermal Energy” last modified August 18, 2011, http://www.geothermalenergy.org/ [2] “Geothermal Heating and Cooling” last modified 2009, http://fli.hws.edu/pdf/GEOTHERMAL%20HEATING%20AND%20COOLING.pdf [3] “Location of Philippines to equator” last modified 2010, http://sdwebx.worldbank.org/climateportalb/doc/GFDRRCountryProfiles/wb_gfdrr_climate_ change_country_profile_for_PHL.pdf [4] “Improper disposal of an air conditioning unit” last modified August 19, 2010, http://www.epa.gov/ozone/title6/608/disposal/household.html [5]“Guidelines on Energy Conserving Design on Building” last modified 2010 http://www.doe.gov.ph/pelmatp/Guidelines_on_Energy_Conserving_Design_on_Buildings_( v._2008).pdf [6] “Relative humidity” last modified 2011, http://www.epa.gov/iaq/pubs/insidestory.html [7] “Humidity Control” last modified 2010, http://www.weather.com/activities/health/allergies/mold/control_humidity.html [8] “Electric Bill” last modified 2011, http://www.geothermalenergy.org [9] “Philippine Weather” last modified 2008, http://www.internationalcircuit.com/philippines/weather.html [10] “Soil Temperature” last modified 2002, http://www.usyd.edu.au/agric/ACSS/sphysic/temperature.html [11] “Soil Temperature” last modified 2006, http://www.geo4va.vt.edu/A1/A1.htm [12] “Earth Temperature and Site Geology” last modified 2006, http://www.geo4va.vt.edu/A1/A1.htm [13] “Air properties” last modified 1999, http://www.arca53.dsl.pipex.com/index_files/propair.htm [14] “Principles of Heat Transfer” last modified 2006, http://www.vesma.com/tutorial/hr_principles.htm [15] “Definition of Dependent Variable” last modified 2012, http://chemistry.about.com/od/chemistryglossary/g/Definition-Of-DependentVariable.htm [16] “Heat Transfer” last modified 1998, �

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatra.html [17] “Heat Conduction” last modifies 1998, http://physics.info/conduction/ [18] “Heat Convection” last modified 1999, http://theory.uwinnipeg.ca/mod_tech/node76.html [19] “Temperature and Humidity” last modified 2007, Conceptual Physics C. Donald Ahrens [20] “Fluid Flow” last modified 2012, http://www.toolingu.com/definition-570210-31848-fluid-flow-rate.html [21] “Geothermal Energy” last modified 2012, http://www.renewableenergyworld.com/rea/tech/geothermal-energy [22] “How Does Geothermal Energy Work for Heating and Cooling?” last modified 2009, http://www.all-energy-solutions.com/how-does-geothermal-energy-work.html [23] “Passive House” last modified 2012, http://www.passivehouse.com/English/PassiveH.HTM [24] "Geothermal Heating & Cooling systems" last modified 2005, http://welldrillingschool.com/courses/pdf/geothermal.pdf [25] "Geothermal Heating and Cooling Introduction"last modified 2001, http://fli.hws.edu/pdf/GEOTHERMAL%20HEATING%20AND%20COOLING.pdf [26] "geothermal heat pump design manual"last modified 2002, http://www.mcquay.com/mcquaybiz/literature/lit_systems/AppGuide/AG_31008_Geothermal_021607b.pdf copyright @ 2002 McQuay International [27] "Air Conditioning Air Flow Rates"last modified 2005, http://www.arca53.dsl.pipex.com/index_files/airflow.htm [28 ] “Geothermal Source Heat Pump; Length Computation” last modified 2009http://www.retscreen.net/download.php/ang/479/0/Textbook_GSHP.pdf, pg.49 [29] PavelKopecký “Designof Earth-to-Air Heat Exchangers” last modified 2009 http://www.cideas.cz/free/okno/technicke_listy/3tlven/TL06EN_1213-2.pdf, pg.1 [30] Carrier handbook “Part 1 carrier load estimating” [31] C.P. Arora “Refrigeration and Air Conditioning,” Comfort Cooling, pg. 451-455 �

[32] AndrisAuliciems and Steven V. Szokolay“ Thermal Comfort” Effective Temperature, pg. 24 last modified 2009, http://www.scribd.com/doc/74707001/4/Basic-psychrometry/ [33] J.P. Holman, “Heat transfer” Table A-5: Properties of air at atmospheric pressure, pg. 649 [34]McQuay “Geothermal Heat Pump” computation/pg.36 http://www.mcquay.com/mcquaybiz/literature/lit_systems/AppGuide/AG_31008_Geothermal_021607b.pdf [35] J.P. Holman “Heat Transfer” Overall Heat transfer eq. (10-2) pg. 554 [36] J.P. Holman “Heat Transfer” Overall heat transfer pg. 554; last modified 2009 http://cmrt.centrale-marseille.fr/cpi/ever09/documents/papers/re7/EVER09-paper-166.pdf; pg 116 [37]“Convective heat transfer coefficient” h value of air,last modified http://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html [38] “Total Resistance” last modified 2007http://cmrt.centralemarseille.fr/cpi/ever09/documents/papers/re7/EVER09-paper-166.pdf; pg.80 [39] “Black Iron pipe data”; pipe handbook, pg. 60 th

[40] J.P. Holman 8 Ed “Heat Transfer” Thermal Conductivity of pipes; p. 638; th

[41]Frank Incropera 6 Ed “Introduction to Heat transfer” by Frank Incropera August 28, 2005 page 645. [42] “Thermal Cinductivity”, k value for clay and sand last modified 2009, learn.greeanlux.org/packages/clear/thermal/buildings/building fabric/properties/conductivity.html [43] “Pressure drop”, last modified 2009 http://www.thermexcel.com/english/ressourc/pdcline.htm [44] J.P. Holman “Heat transfer” Table A-5: Properties of air at atmospheric pressure, pg. 649 [45] “Roughness coefficient” last modified 2009 http://www.engineeringtoolbox.com/surfaceroughness-ventilation-ducts-d_209.html [46] “Thermal conductivity” last modified 2009; http://www.engineeringtoolbox.com/thermalconductivity-d_429.html [47] “Specific heat capacity” last modified 2008 http://www.engineeringtoolbox.com/specificheat-solids-d_154.html

�

Design Fabrication and Installation of an Open Loop Geothermal Cooling System for a Residential House Application

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