REFRIGERATION AND AIR CONDITIONING
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Chapter 1:-
FUNDAMENTALS OF REFRIGERATION & AIR REFRIGERATION (2×3-6, 1×8-8, total 14marks)
Short answer questions
1. List out any six applications of refrigeration.
2. Define the terms refrigeration and COP.
3. Differentiate between the refrigerator and heat pump.
4. List out various methods of refrigeration.
5. Write any five differences between open air system and closed air system.
6. Define the term TON of refrigeration and give the value in SI units.
7. An refrigeration plant working on Carnot cycle between temperature limits of 30°C and -5°C has a
capacity of 10 tons. Determine the power input to the plant.
Essay answer questions
1. Describe with a sketch the working of a Bell-Coleman cycle. Show the processes on T-s and p – V
diagram.
2. Explain any two methods of refrigeration systems with neat diagrams.
3. In an open type air refrigeration system 550 kg of air is circulated per hour. The air is drawn from
the cold chamber at 3°C at 1bar and compressed to 5bar. It is then cooled to 20°C at the same pressure. Air is then led to expander, where it is expanded isentropically down to 1bar and is discharged to cold chamber. Find
a. Heat extracted from the cold chamber
b. Heat rejected to cooling water / hour
c. COP of the system.
4. A cold storage is supplied with 4000 kg of fish at 22°C. The fish has to be cooled to -10°C. Freezing point of the fish is -2°C. If the capacity of the plant is 10 tons, how long will it take to cool the fish? Specific heats of the fish above and below the freezing point are 3 kJ/kg K and 1.25 kJ/kg K respectively. Latent heat of freezing = 220 kJ/kg.
5. A 5 ton refrigerating machine operating on Bell-Coleman cycle has pressure limits of 10 bar and 1 bar. The temperature of air before compression and is 10°C. The compressed air is cooled to 40°C before it enters an expander. Assuming both compression and expansion are adiabatic with y = 1.4. Determine (a) COP (b) Mass of air circulated per min. (c) Power Rating of the motor assuming 90% mechanical efficiency.
Chapter 2:-
VAPOUR COMPRESSION & VAPOUR ABSORPTION REFRIGERATION SYSTEMS (2×3-6, 1×8-8, total 14marks)
Short answer questions
1. List any six thermodynamic properties of refrigerants
2. Differentiate between primary and secondary refrigerants.
3. Define refrigerant. List out any eight common refrigerants.
4. Distinguish between wet and dry compression.
5. State the purpose of flash chamber and accumulator in the Vapour compression system.
6. List out basic components of Vapour compression refrigeration system and their functions.
7. Represent Vapour compression cycle on T-S and P-H diagrams when the Vapour is wet at the
end of compression
8. Why ammonia used as a common refrigerant in Vapour absorption refrigeration system?
9. List the differences between a Vapour absorption system and a compression system.
Essay answer questions
1. Explain in detail the working of Vapour compression system with neat sketch.
2. Explain ammonia-water Vapour absorption refrigeration system with a line diagram.
3. Explain the working principle of Electrolux refrigerating system with a neat sketch.
4. Describe the desirable properties of an ideal refrigerant. (Thermodynamic properties)
5. An ammonia refrigerator produces 30 tonnes of ice from and at 0 deg * C per day. The cycle works between the temperature limits of 25 deg * C and -150C. The vapour is dry saturated at the end of compression. Find (i)COP and (ii) Power required to run the compressor. The properties of refrigerant are shown in table. Latent heat of ice is 335KJ/Kg.
°C hf hg sf sg
-15°C -54.7 1310 -0.2142 5.07784
25°C 100.4 1324 0.3486 4.5024
6. Analyse the result from the following data: A simple vapour compression plant produces 5 tons of refrigeration. The enthalpy values at the inlet to compressor, at the exit of compressor and at exit from the condenser are 183.2KJ/Kg, 209.4KJ/Kg and 74.6KJ.Kg respectively. Calculate:(a)The refrigerant flow rate(b) The COP (c The) power required to drive the compressor
7. The ammonia refrigeration plant works between the temperature limits of -15°C to 30°C. The working fluid ammonia is assumed to be dry saturated at the end of compression. Calculate (a)Refrigerating effect (b) COP
°C hf hg sf sg
-15°C 112.2 1424.9 0.4564 5.5423
30°C. 322.6 1468.1 1.2017 4.9809
Chapter 3:-
REFRIGERATION EQUIPMENT & APPLICATIONS OF REFRIGERATION
Short answer questions (2x3=6, 1x8-8, total 14marks)
1. Compare between water cooled and air cooled condensers.
2. What is function of compressor in a refrigeration system?
3. What is the function of condenser? How do you classify the condensers?
4. List the different types of evaporators?
5. State the function of expansion device in a refrigeration system and Classify expansion devices.
6. What is hermitic compressor? State its applications.
7. What is capillary tube? State its function.
Essay answer questions
1. Explain the working of thermostatic expansion valve with neat sketch.
2. Draw the neat sketch of flooded type evaporator and explain it’s working.
3. Explain the working of evaporative condenser with neat diagram and explain it’s advantages and disadvantages over other.
4. Explain the construction and working principles of ice plant with a neat sketch
5. Draw a neat sketch of water cooler and explain it’s working.
Chapter 4:-
AIR CONDITIONING & PSYCROMETRY
Short answer questions (2x3=6, 1×8-8, total 14marks)
1. Define air conditioning.
2. State any six the factors that determine human comfort.
3. What are the applications of air conditioning?
4. Write requirement of human comfort conditions.
5. Define the terms relative humidity and specific humidity
6. Define the terms DBT, WBT & DPT
7. Define Psychrometry. What is Psychrometric chart?
Essay answer questions
1. 900 kg/hr. of return air at DBT 24°C and RH 60% mixes with 100 kg/hr.of fresh air of DBT 40° C and RH 30%. Calculate the final condition of this mixture.
2. For a sample of air having 22° C DBT, relative humidity 30% at barometric pressure of 760 mm of Hg. Calculate (a)Vapour pressure.(b)Humidity ratio. (c)Enthalpy.
3. Find dew point temperature, relative humidity and specific humidity of moist air at dry bulb temperature of 30 °C and wet bulb temperature of 20 °C.
4. The atmospheric conditions of air are specified by Dry bulb temperature is 30°C and humidity ratio is 15gms/Kg of air. Determine (a) Partial pressure of water vapour (ii) Relative humidity
5. A steam of outdoor air is mixed with a steam of return air in an air conditioning system that operates at 101 kPa pressure. The flow rate of outdoor air is 2 kg/s and its condition is 35°C dry bulb temperature. The flow rate of return air is 3 kg/s, and its condition is 24 °C and 50% relative humidity. Determine (a) the enthalpy of the mixture (b) the humidity ratio of the mixture (c) the dry bulb temperature of the mixture.
Chapter 5:-
AIR CONDITIONING EQUIPMENT & APPLICATIONS OF AIR CONDITIONING
Short answer questions (2x3=6, 1×8-8, total 14marks)
1. Give detailed classification of air-conditioning systems.
2. State the need of cooling towers in A.C system.
3. State the advantages of unitary air conditioning system.
4. What are the various duct systems? Why ducts are used in air conditioning system.
5. Why filter is used in air-conditioning system? List out different types of filters.
6. What are the essential components of air conditioning system?
Essay answer questions
1. Draw and explain year round air conditioning.
2. Describe any two types of duct systems employed to supply conditioned air to outlets.
3. Describe the working of an air cooler with a neat sketch.
4. Explain various air distribution systems.
5. Explain the summer air conditioning system with neat sketch
PART-C: 10 Marks question will be given from 2nd, 3rd or 5th lesson.