Abstract The modern commercial or office building consists of the HVAC system which is Heating, Ventilation, Air-conditioned. Air-conditioned. In this report, we’ll going to identify the purpose and goals of HVAC HVAC system, describe HVAC types, describe HVAC parts and describe how this part wor!s together or it’s wor!ing cycle. "esides to air-conditioning air-conditioning there are #entilation systems li!e ceiling fan, fresh air supply and e$haust fan where ceiling fan is used is used to #entilate the air with rotating blades and e$haust fan is used to displace the inside air to the outside en#ironment, fresh air supply is used to displace the inside air to the outside en#ironment by supplying fresh air from the outside air.
%b&ecti#e The ob&ecti#e of the report to !now and understand the HVAC system, it’s wor!ing cycle, the HVAC parts and types of HVAC. HVAC stand for heating, #entilation, air-conditioning. 'ith #entilation we can control the (uality of air either by displacing the air to the outside or may be #entilating the air with ceiling fan.
Introduction Air (uality is essential considerations in maintaining the producti#ity, comfort and health of the occupants. If air (uality and temperature are not maintained, occupants comfort in the wor! place can suffer directly affecting producti#ity. Air conditioning is the process of altering the properties of air )primarily temperature and humidity* to more fa#orable conditions. The control of these conditions may be desirable to maintain the health and comfort of the occupants, or to meet the re(uirements of industrial processes irrespecti#e of the e$ternal climatic conditions. It is used to cool products or a building en#ironment. An air conditioning system is an assembly of different part of the system used produce a specified condition of air within a re(uire space or building. +efrigeration systems are also used for pro#iding cooling and dehumidification in summer for personal comfort )air conditioning*. The first air conditioning systems were used for industrial as well as comfort air conditioning. astman oda! installed the first air conditioning system in /0 in +ochester, 1ew 2or! for the storage of photographic films. An air conditioning system was installed in a printing press in 034 and in a telephone e$change in Hamburg in 035. 6any systems were installed in tobacco and te$tile factories around 033. The first domestic air conditioning system was installed in a house in 7ran!furt in /05. A pri#ate library in t 8ouis, 9A was air conditioned in /0:, and a casino was air conditioned in 6onte Carlo in 03. fforts ha#e also been made to air condition passenger rail coaches using ice. The widespread de#elopment of air conditioning is attributed to the American scientist and industrialist 'illis Carrier. Carrier studied the control of humidity in 034 and designed a central air conditioning plant using air washer in 035. ;ue to the pioneering efforts of Carrier and also due to simultaneous de#elopment of different components and controls, air conditioning (uic!ly became #ery popular, especially after 04<. At present comfort air conditioning is widely used in residences, offices, commercial buildings, air ports, hospitals and in mobile applications such as rail coaches, automobiles, aircrafts etc. Industrial air conditioning is largely responsible for the growth of modern electronic, pharmaceutical, chemical industries etc. 6ost of the present-day air conditioning systems use either a #apor compression system or a #apor absorption system.
=rinciple of wor!ing cycle )how does it wor!>* The goal is to !eep it more comfortable inside the house than it is outside.
Fig 1: cycles of refrigeration Principles of Refrigeration •
8i(uids absorb heat when changed from li(uid to gas
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?ases gi#e off heat when changed from gas to li(uid.
7or an air conditioning system to operate with economy, the refrigerant must be used repeatedly. 7or this reason, all air conditioners use the same c ycle of compression, condensation, e$pansion, and e#aporation in a closed circuit. The same refrigerant is used to mo#e the heat from one area, to cool this area, and to e$pel this heat in another area. •
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The refrigerant comes into the compressor as a low-pressure gas, it is compressed and then mo#es out of the compressor as a high-pressure gas. The gas then flows to the condenser. Here the gas condenses to a li(uid, and gi#es off its heat to the outside air. The li(uid then mo#es to the e$pansion #al#e under high pressure. This #al#e restricts the flow of the fluid, and lowers its pressure as it lea#es the e$pansion #al#e. The low-pressure li(uid then mo#es to the e#aporator, where heat from the inside air is absorbed and changes it from a li(uid to a gas. As a hot low-pressure gas, the refrigerant mo#es to the compressor where the entire cycle is repeated.
1ote that the four-part cycle is di#ided at the center into a high side and a low side This refers to the pressures of the refrigerant in each side of the system
A.C. wor!s on the mechanism of refrigerant li(uid. This li(uid change to gas and e#aporates as it e$tracts heat from the air around it and in low pressure conditions it again gets con#erted to li(uid and after entering into the normal pressure region this again changes into gas. Any A.C. will comprise of 5 parts i.e. a compressor, a condenser, e$pansion #al#e and an e#aporator. Compressor and condenser are usually !ept outside the house where as an e#aporator is !ept inside the house. Compressor is the most important part of all the three as it pumps the #apor refrigerant through the system. In the e#aporator, the fluid lea#es as low pressure cool gas to reach compressor. The compressor will compress the gas to li(uid. As the gas becomes li(uid, the molecules are together and their energy is high resulting in high temperature. The wor!ing fluid lea#es compressor and flows into condenser as hot air which will con#ert this hot air to low pressuri@ed li(uid. %ne can obser#e the temperature around outside unit, which is high due to heat dissipated from compressor. The temperature in condenser is #ery low and this con#erts the high temperature gas into low pressuri@ed li(uid. Through a small hole )e$pansion #al#e* this pressuri@ed li(uid will flow to into e#aporator. In this process, the pressure drops and the li(uid is con#erted into low pressure cool air to start the cycle once again. In the process of changing li(uid to gas it e$tracts heat from the air around it. #aporator has fins and it will blow that cool air into the room. The hot air is lighter than cool air, so it is in the upper part of the room whose heat is used to con#ert high pressuri@ed li(uid into low pressuri@ed gas. This process continues till the room attains the temperature you set. The thermostat present in the A.C. will temporarily stop A.C. for some time if the room temperature raises again, the thermostat will automatically on the A.C. to set the temperature of your room to your desired le#el. The basic elements of air conditioning system: -• • • • •
7ansB 7or circulation of air 7iltersB 7or cleaning air ?rillB It ad&ust the direction of the conditioned air to the room. TrayB It collects condensed water. +efrigerating =lantB pro#ide cooling. It consists of compressorgenerator and absorber, e#aporator, condenser, e$pansion de#ice )capillary tube*. TYPE OF AIR-O!"ITIO!I!#
The choice of which air conditioner system to use depends upon a number of factors including how large the area is to be cooled, the total heat generated inside the enclosed area, etc. An HVAC designer would consider all the related parameters and suggest the system most suitable for your space. * 'indow air-conditioning system 4* plit air-conditioning system <* Centrali@ed air-conditioning system 5* =ac!age air-conditioning system * 'indows Air-conditioning ystem 'indow air conditioner is the most commonly used air conditioner for single rooms. In this air conditioner all the components, namely the compressor, condenser, e$pansion #al#e or coil, e#aporator and cooling coil are enclosed in a single bo$. This unit is fitted in a slot made in the wall of the room, or more commonly a window sill.
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'indow air conditioners are one of the most commonly used and cheapest type of air conditioners. To install one of these units, you need the space to ma!e a slot in the wall, and there should also be some open space behind the wall. 'indow air-conditioner units are reliable and simple-to-install solution to !eep a room cool while a#oiding the costly construction of a central air system. "etter yet, when the summer heat dies down, these units can be easily re mo#ed for storage, and you can use the window sill for other purpose
Fig 2: window air conditioner
4* plit Air-Conditioning ystem The split air conditioner comprises of two partsB the outdoor unit and the indoor unit. The outdoor unit, fitted outside the room, houses components li!e the compressor, condenser and e$pansion #al#e. The indoor unit comprises the e#aporator or cooling coil and the cooling fan. 7or this unit, you don’t ha#e to ma!e any slot in the wall of the room. 7urther, present day split units ha#e aesthetic appeal and do not ta!e up as much space as a window unit. A split air conditioner can be used to cool one or two rooms.
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The split air conditioner comprises of two partsB the outdoor unit and the indoor unit. The outdoor unit, fitted outside the room, houses components li!e the compressor, condenser and e$pansion #al#e. The indoor unit comprises the e#aporator or cooling coil and the cooling fan. 7or this unit, you don’t ha#e to ma!e any slot in the wall of the room. 7urther, the present day split units ha#e aesthetic loo!s and add to the beauty of the room. The split air conditioner can be used to cool one or two rooms
The plit Air Conditioner di#ided in two partsB -* 7irst partB-Include the e#aporator, filter, e#aporator fan and grill. They placed inside the room. 4* econd partB-Include Condenser, fan, compressor. This placed outside the room. ;iameter tubes. therefore, small hole re(uired in wall of installation of split air condition. The split air conditioning units are a#ailable in capacity range of to < tons. $OR%I!# OF &P'IT A O!"ITIO!ER
The fans blow air o#er the coils to impro#e their ability to dissipate heat )to the outside air* and cold )to the room being cooled*. 'hen you get into larger air-conditioning applications, it’s time to start loo!ing at split-system units. A split-system air conditioner splits the hot side from the cold side of the system, as in the diagram below. The cold side, consisting of the e$pansion #al#e and the cold coil, is generally placed into a furnace or some other air handler. The air handler blows air through the coil and routes the air throughout the building using a series of ducts. The hot side, !nown as the condensing unit, li#es outside the building. The unit consists of a long, spiral coil shaped li!e a cylinder. Inside the coil is a fan, to blow air through the coil, along with a weather-resistant compressor and some control logic. This approach has e#ol#ed o#er the years because itDs low-cost, and also because it normally results in reduced noise inside the house )at the e$pense of increased noise outside the house*. %ther than the fact that the hot and cold sides are split apart and the capacity is higher )ma!ing the coils and compressor larger*, thereDs no difference between a split-system and a window air conditioner.
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A split air conditioner does not re(uire ma&or installation wor! because it does not re(uire ductwor!. +ather, the indoor and outdoor units are connected with a set of electrical wires and tubing. This is good for your wallet and the en#ironment. The ductwor! re(uired for many traditional AC units generally increases energy e$penditures, as many centrali@ed AC units lose a lot of energy due to heat e$change in the air duct system. o, without a duct system, there is #ery little opportunity for heat or energy loss in a split air conditioner system.
enefits of a &plit Air onditioning &ystem
This !ind of air conditioner system has many ad#antages o#er traditional air conditioners. =erhaps the most ob#ious benefit is the (uiet performance of a split air conditioner system. The parts of an air conditioner that ma!e the most noise is the compressor and the fan that cools the condenser. In a split system, the compressor and fan for the condenser are located outside of the room being cooled and therefore the ma&or sources of noise are remo#ed - unli!e with window units. Another benefit of a split air conditioner system is that you can opt for a multi-split system, where you can ha#e more than one indoor unit connected to a single outdoor unit. This ma!es it easy to cool multiple rooms or maintain the temperature throughout a large room through the use of two indoor cooling units. A split air conditioner is an efficient and cost-effecti#e way to cool your home. It should be noted that the initial cost of this !ind of air conditioning unit is significantly higher than a window unit and it does re(uire professional installation. Howe#er, the amount of money you will sa#e on your energy bills as well as the longe#ity of the unit will ma!e it worth your while in the end. <* * entrali.ed Air-onditioning &ystem
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The central air conditioning plants or the systems are used when large buildings, hotels, theaters, airports, shopping malls etc. are to be air conditioned completely. The window and split air conditioners are used for single rooms or small office spaces. If the whole building is to be cooled it is not economically #iable to put window or split air conditioner in each and e#ery room. 7urther, these small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc.
The central air conditioning plants or the systems are used when large buildings, hotels, theaters, airports, shopping malls etc. are to be air conditioned completely. The window and split air conditioners are used for single rooms or small office spaces. If the whole building is to be cooled it is not economically #iable to put window or split air conditioner in each and e#ery room. 7urther, these small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc. In the central air conditioning systems, there is a plant room where large compressor, condenser, thermostatic e$pansion #al#e and the e#aporator are !ept in the large plant room. They perform all the functions as usual similar to a typical refrigeration system. Howe#er, all these parts are larger in si@e and ha#e higher capacities. The compressor is of open reciprocating type with multiple cylinders and is cooled by the water &ust li!e the automobile engine. The compressor and the condenser are of shell and tube type. 'hile in the small air conditioning system capillary is used as the e$pansion #al#e, in the central air conditioning systems thermostatic e$pansion #al#e is used. The chilled is passed #ia the ducts to all the rooms, halls and other spaces that are to be air conditioned. Thus, in all the rooms there is only the duct passing the chilled air and there are no indi#idual cooling coils, and other parts of the refrigeration system in the rooms. 'hat is we get in each room is the completely silent and highly effecti#e air conditions system in the room. 7urther, the amount of chilled air that is needed in the room can be controlled by the openings depending on the total heat load inside the room. The central air conditioning systems are highly sophisticated applications of the air conditioning systems and many a times they tend to be complicated. It is due to this reason that there are #ery few companies in the world that speciali@e in these systems. In the modern era of computeri@ation, a number of additional electronic utilities ha#e been added to the central conditioning systems. $OR%I!# OF E!TRA' A O!"ITIO!ER
The central A.C. type that Addis Ababa bole airport uses consists of an e#aporator, compressor, condenser E e$pansion #al#e. The compressor is of open type and can be dri#en by the motor directly or by the belt #ia pulley arrangement connected to the motor. The refrigerant fluid enters the compressor Inhaling the refrigerant from the suction channel Compressing to the discharge channel. There is a silencer de#ice which is used to !eep the noise le#el low or !eep it silent. In the condenser heat is remo#ed b y cooled water, with water flowing along the shell side and refrigerant along the tube side. In the condenser, +efrigerant #apor turn to li(uid. To complete the cycle, the high-pressure li(uid is made to flow through an e$pansion #al#e )#enturi#al#e*. The thermostatic e$pansion #al#e is operated automatically by the solenoid #al#e. In the e$pansion #al#e, 8ow the temperature and pressure of li(uid is obtained.it controls Control the flow rate in to the e#aporator.
The refrigeration effect is obtained in the cold region as heat is e$tracted by #apori@ation of refrigerant in the e#aporator. The e#aporator is also called as the chiller, because it chills the water. If the water flows along the shell side and refrigerant on the tube side, it is called as the dry e$pansion type of chiller. In the e#aporator li(uid turns to #apor and cold air flows out room.
7ig 5B central air-conditioner with blower distributing the chilled is passed #ia the ducts to all the rooms, halls and other spaces that are to be air conditioned. There are t)o types of central air conditioning plants or systems:
* ;irect e$pansion or ;F central air conditioning plantB In this system the huge compressor, and the condenser are housed in the plant room, while the e$pansion #al#e and the e#aporator or the cooling coil and the air handling unit are housed in separate room. The cooling coil is fi$ed in the air handling unit, which also has large blower housed in it. The blower suc!s the hot return air from the room #ia ducts and blows it o#er the cooling coil. The cooled air is then supplied through #arious ducts and into the spaces which are to be cooled. This type of system is useful for small buildings. 4* Chilled water central air conditioning plantB This type of system is more useful for large buildings comprising of a number of floors. It has the plant room where all the important units li!e the compressor, condenser, throttling #al#e and the e#aporator are housed. The e#aporator is a shell and tube. %n the tube side the 7reon fluid passes at e$tremely low te mperature, while on the shell side the brine solution is
passed. After passing through the e#aporator, the brine solution gets chilled and is pumped to the #arious air handling units installed at different floors of the building. The air handling units comprise the cooling coil through which the chilled brine flows, and the blower. The blower suc!s hot return air from the room #ia ducts and blows it o#er the cooling coil. The cool air is then supplied to the space to be cooled through the ducts. The brine solution which has absorbed the room heat comes bac! to the e#aporator, gets chilled and is again pumped bac! to the air handling unit. To operate and maintain central air conditioning systems you need to ha#e good operators, technicians and engineers. =roper pre#entati#e and brea!down maintenance of these plants is #ital. 5* =ac!aged Air-Conditioning ystem
The window and split air conditioners are usually used for the small air conditioning capacities up to : tons.
The central air conditioning systems are used for where the cooling loads e$tend beyond 43 tons.
The pac!aged air conditioners are used for the cooling capacities in between these two e$tremes.
The pac!aged air conditioners are a#ailable in the fi$ed rated capacities of <,:, G, 3 and : tons.
These units are used commonly in places li!e restaurants, telephone e$changes, homes, small halls, etc.
7ig :B pac!aged air-conditioner
oncl/sion
'e ha#e seen that how the A.C. wor!s , different parts, types and the wor!ing cycle
