Q1 List down the main sources that add heat to the passenger cabin in aero planes? Q2 The coefficient of performance of Carnot refrigeration, which extracts 8350 kj/min from a heat source is 5. Find power required to run the compressor Q3 An inventor claims to have developed a refrigerating unit which maintains the refrigerated space at -5º C which operating in a room where temperature is 26º C and has a COP = 8.4. Find out whether his claim is correct or not? Q4 What are main components of simple vapour compression refrigeration system? Q5 What are the main factors affecting the performance of simple vapour compression refrigeration system? Q6 How does actual simple vapour compression refrigeration system differ from theoretical vapour Compression system? Q7 Define Clearance volume and volumetric efficiency Q8 What is the difference between wet compression and dry compression? Q9 what are the main components of vapour absorption refrigeration system? Q10 List the properties of ideal refrigerant and ideal absorbent for vapour absorption refrigeration system Q11 what are the main advantages of vapour absorption refrigeration system over vapour compression refrigeration system? Q12 Give at least 2 examples exa mples of most commonly used refrigerant absorbent combination Q13 what are the desirable properties of thermoelectric material? Q14 Explain Peltier, Seeeck and Thomson effects Q15 what are the applications of Vortex tube? Q16 what is a refrigerant? How refrigerants are classified? Q17 what is an Azeotrope? Give an example Q18 What are secondary refrigerants? Give examples Q19 List the main methods used in leak detection of commonly used refrigerants? Q20 State the effect and causes of moisture in refrigeration system Q21 Give the chemical formula for following refrigerants (1) R – 12 (2) R – 22 Q22 Define the term Psychometry and psychrometrics Q23 Differentiate between specific humidity and relative humidity Q24 Differentiate between dry bulb temperature and wet bulb temperature Q25 Define the term dew point temperature and dew point depression Q26 what are psychometric processes? List important psychometric processes Q27 What are psychometric charts? What is there use? Q28 Differentiate between grand sensible heat factor and room sensible heat factor Q29 following following data data pertains pertains to an air air conditionin conditioning g systems systems : uncondition unconditioned ed space space DBT = 30º C : unconditioned space WBT = 22º C, cold duct supply surface temperature temperature 14º C Determine (1) Dew point point temperatu temperature re (2) Whether Whether or not condensation condensation will form on the duct?
Q30 Define effective temperature as applied to human comfort Q31 List the factors governing optimum effective temperature Q32 Sketch comfort chart and show comfort zone on it Q33 Explain how air conditioning systems are classified? Q34 List the various types of expansion devices used in air conditioning systems Q35 Write the different heat loads that are taken up by air conditioning system Q36 Explain how ERSHF differ from GSHF? Q37 What are ducts? Explain how they are classified? Q38 What is the function of fan in air conditioning system ? Q39 Discuss when does dry bulb temperature and wet bulb temperature equal ? Q40 Explain why semiconductor materials prefered to metals in thermoelectric refrigeration ?
5 mark category questions :
Q1 What is the main characteristic feature of an air refrigeration system? Q2 Differentiate clearly between open and closed air refrigeration systems Q3 State merits and demerits of air refrigeration system Q4 Describe briefly the working of simple air cooling system used for a ir crafts Q5 A carnot refrigerator operates between -45º C and 45º C Determine the COP. It is desired to the COP to make the COP equal to 3.5 by changing temperatures. The increase (or decrease) in upper temperature is to be equal to decrease (increase) in lower temperature . Determine the new temperatures. Q6 Derive an expression for volumetric efficiency of a reciprocating compressor Q7 Discuss some methods for improving the performance o simple vapour compression refrigeration System Q8 A refrigeration cycle uses Freon – 12 as a working fluid. The temperature of the refrigerant in the evaporator is – 10 º C. The condensing temperature is 40º C. The cooling load is 150 W and volumetric efficiency of the compressor is 80%. The speed of the compressor is 720 r.p.m Calculate the mass flow rate of the refrigerant and displacement volume of the compressor using properties of Freon – 12. Q9 Describe a simple vapour compression cycle giving clearly its flow diagram Q10 Discuss the advantages of multistage or compound compression over single stage compression Q11 Explain by flow diagram and on p-h diagrams the 2 evaporator at different temperatures with compound compression and perfect intercooling, vapour compression refrigeration systems Q12 Compare Vapour absorption and Vapour compression refrigeration Systems Q13 Explain the working of Electrolux Refrigerator with the help of suitable diagram Q14 Discuss the working of Practical vapour absorption system explaining in detail the function of each component
Q15 Discuss the working of Lithium bromide absorption refrigeration system using suitable diagram Q16 What is non conventional refrigeration system? Why it is ca lled so? Q17 Discuss the advantages and disadvantages of non conventional refrigeration systems Q18 Explain in detail working, advantages and applications of Vortex tube Q19 Discuss why refrigerants are so selected that evaporator and condenser pressures are greater than atmospheric pressures? Q20 Discuss the physical and thermodynamic properties of the following refrigerants R- 11, R-12, R-21 Q21 State how will you carry out leak detection in following refrigerants (1) Ammonia (2) R – 12 Q22 Discuss in detail important physical, chemical and thermodynamic properties of an ideal refrigerant? Q23 Discuss Lined and Claude methods for liqufication of air Q24 what are Cascade systems? Discuss with the h elp of an example Q25 Derive mathematical relation between specific humidity and relative humidity Q26 Define enthalpy of moist air and derive mathematical relation for it Q27 The atmospheric conditions are 20º C and specific humidity of 0.0095 kg/kg of dry air Calculate the following (1) Partial pressure of vapour (2) Relative humidity (3) Dew point temperature Q28 0.004 kg of water vapours per kg of atmospheric are removed and temperature of air after removing the water vapors becomes 20º C Determine (1) Relative humidity (2) Dew point temperature Assume that condition of atmospheric air is 30º C and 55% R.H and pressure is 1.0132 bars. Q29 Using psychometric charts discuss the various psychometric processes. Q30 1kg of air at 35º C DBT and 60% RH is mixed with 2 kg of air at 20º C DBT and 13º C dew point temperature. Calculate the specific humidity of the mixture Q31 100 kg/s of moist air at 35º C DBT 20º C DPT mixes adiabatically with 30 kg/s of moist air at 40º C DBT and 30% RH ,determine (1) humidity ratio of mixture (2) temperature of mixed stream (3) enthalpy of mixed stream Make use of steam tables and psychometric charts Q32 90 m3 of air per minute at 20º C and 75% RH is heated until its temperature becomes 30º C . Calculate (1) RH of the heated air (2) Heat added to the air per minute.
Q33 Explain briefly as to how the human body reacts to changes in temperature of human body. Also explain the effect of activities on the heat load calculation for comfort calculation
10 mark category questions
Q1 A Bell Coleman refrigerator operates between pressure limits of 1 bar and 8 bar. Air is drawn from the cold chamber at 9º C, compressed and then cooled to 29 º C before entering the expansion cylinder. Expansion and compression follow the law pv1.35 = C. Calculate the theoretical COP of the system . For air take cp as 1.003 kj/kg k Q2 An air conditioning system unit of pressurized aircraft receives air from the jet engine compressor at a pressure of 1.25 bar. The ambient pressure and temperature are 0.2 bar and 237 K respectively. The work produced by the turbine is sufficient to drive the compressor. The compressed air is then cooled in the cooler at constant pressure and then expanded in the turbine to the cabin pressure of 1.0 bar and temperature of 280 K. calculate (1) the compressor discharge pressure (2) the cooler exit temperature Q3 A refrigerator works between 7º C and 27º C. The vapour is dry at the end of adiabatic compression. There is no undercooling and evaporation is by throttle valve. Determine (1) the COP (2) Power of compression to remove 180 kj/min Refrigerant used is R -12 Make use of refrigerant tables. Q4 28 tonnes of ice from and at 0º C is produced per day in an ammonia refrigerator . The temperature range in the compressor is from 25º c to -15º C. Th e vapour is dry and saturated at the end of compression process and expansion valve is used. Assuming COP of 62% of the theoretical, calculate the power required to drive the compressor. Make use of refrigerant tables, charts Latent heat of ice = 335 Kj/kg
Q5 The following data relate to conference room for seating 80 persons Inside design condition …………………. 22 C DBT and 55% RH Outside design condition………………….38 C DBT and 28 C WBT Sensible and latent heat loads per person…75 W and 45 W Lights and fans loads……………………….12000 W Sensible heat gain through glass, walls …….12000 W Air infiltrations ………………………………18 m 3 / min Fresh air supplied………………………………80 m3 / min Bypass factor of the coil………………………..0.1 If two- third of recirculated room air and on e third of fresh air are mixed before the cooling coils, determine (1) apparatus dew point temperature (2) grand total heat load (3) effective room sensible heat factor Q6 Explain the step by step procedure of designing an air conditioning system for a class room of 60 seating capacity. Q7 An air conditioning system is to be designed for restaurant with the following data : Outside design condition…………………………………..40 C DBT 28 C WBT Inside design condition……………………………………..25 C DBT 50% RH Solar heat gain through walls , roof and floor………………5.87 KW Solar heat gain through glass………………………………...5.52 KW Occupants…………………………………………………….25 Sensible heat gain per person………………………………….58 W Latent heat gain per person…………………………………….58 W Internal lightning load …………………………………………15 lamps of 100 W Sensible heat gain from other sources…………………………..11.63 KW Infiltered air ……………………………………………………..15 m3 / min If 25 % fresh air is mixed with 75% recirculated air and passed through conditioner coil, (1) The amount of total air required in m3/ hr. (2) the dew point temperature of coil (3) the condition of supply air to the air (4) the capacity of conditioning plant Assume the bypass factor = 0.2
Q 8 250 m3 of air is supplied per minute from outdoor condition of 38 º DBT and 25 º WBT to an air conditioned room. The air is dehumidified by cooling coil having a bypass factor 0.35 and dew point temperature 13 C and then by chemical dehumidifier. Air leaves the chemical dehumidifier at 32 C DBT. Air is then passed over a cooling coil whose surface temperature is 13 C and bypass factor 0.25. Calculate the capacities of 2 cooling coils and dehumidifier. Q9 What are psychrometric processes? Explain briefly all the psychrometric processes using psychrometric charts. Q10 What do u mean by charging of refrigeration system? Explain in details using suitable diagram the mechanism of charging of refrigeration system
