1. Answer the following question:

(a) Define (i) Refrigeration (ii) Ton of Refrigeration (iii) Air Conditioning (iv) Coefficient of Performance.

(b) Explain difference between vapour compression refrigeration system and vapour absorption refrigeration system.

(c) Name the different types of air refrigeration systems used for cooling of the aircraft cabin. Draw bootstrap air refrigeration cycle with neat schematic and T-S diagram.

(d) What are the desirable properties of refrigerants? Compare primary and secondary refrigerants.

2. (a) Discuss the effect of change in evaporator and condenser pressure on the performance of standard VCR cycle with the help of P-h diagram.

(b) The following data refers to simple air refrigeration cycle of 20 TR capacity

Ambient air temperature and pressure =$20^\circ C$ and 0.8bar

Ram air pressure =0.9 bar

Compressor outlet pressure = 3.6 bar

Temperature of air leaving H.E. = $60^\circ C$

Pressure of air leaving the turbine = 1bar

Temperature of air leaving the cabin = $22^\circ C$.

Compressor and turbine efficiency = 80% and 75% respectively.

Assume no pressure drop in H.E. and isentropic ramming process. Calculate net power required and COP of the system.

3. (a) A vapour compression system using R12 work between -15$^\circ$C and 35$^\circ$C as evaporator and condenser temperature respectively. Using P-h chart determine:

(i) COP

(ii) Mass flow of refrigerant TR.

(iii) Piston displacement per TR using volumetric efficiency 80%.

(iv) Heat rejected in the condenser per TR

(v) Ideal COP

(b) What are the types of expansion valve? Explain the working of thermostatic expansion valve.

4. (a) Discuss various prometric processes that can be achieved by using an air washer.

(b) Explain the various methods of duct design.

5. (a) The room sensible and latent heat loss of an air condition space are 50kW and 10 KW respectively. The room condition is 26$^\circ$C dry bulb temperature and 50% relative humidity. The outdoor condition is 37$^\circ$C dry bulb temperature and 45% relative humidity. The ventilation requirement is such that on mass flow rate basis 20% fresh air is introduced in 80% of supply areas recirculated. The bypass factor of the cooling coil is 0.15. Determine:

(i) Supply air flow rate.

(ii) Outside air sensible heat.

(iii) Outside air latent heat.

(iv) Grand total heat; and

(v) ERSHF

(b) Classify different types of compressors. Explain each type in brief.

6. Write short notes on any four of the following:

(a) Central air conditioning system.

(b) LiBr-Water vapour absorption system.

(c) Controls used in Refrigeration and Air Conditioning.

(d) Vortex Tube Refrigeration.

(e) Steam jet refrigeration.

(f) Liquification of gases.

7. Answer any four of the following:

(a) Draw simple vapour compression cycle on P-h diagram and explain the processes.

(b) What is subcooling and superheating? Explain its effect on the performance of vapour compression cycle.

(c) If the COP of a 1 TR Air Conditioner is 3.5; how much power will the compressor consume? Also calculate the amount of heat rejected in the condenser.

(d) List down types of aircraft refrigeration systems. Draw a simple air cooling system with neat schematic and T-s diagram.

(e) What is human comfort? Explain with the help of ASHRAE Comfort chart.

(f) What are primary and secondary refrigerants? Give examples with application of each type.

8. (a) A bootstrap air refrigeration system of 30 TR capacity is used for an aeroplane flying at an altitude of 2000 m. The ambient air pressure and temperature are 0.8 bar and 0$^\circ$C. The ram air pressure and temperature are 1.05 bar in 17$^\circ$C. The pressure of air after isentropic compression in the main compressor is 4 bar. This air is now cooled to 27$^\circ$C in another auxiliary heat exchanger and then expanded isentropically up to the cabin pressure of 1.01 bar. If the air leaves the cabin at 25$^\circ$C and efficiencies for the main compressor, auxiliary compressor and the cooling turbine are 80%, 75% and 80% respectively; find: (i) Power required to operate the system and (ii) COP of the system.

(b) Classify refrigeration compressors. Explain each type in brief.

9. (a) Define the terms DBT, WBT, DPT and RH.

(b) What are the different types of Cooling Towers? Define Range and Approach.

(c) Draw a neat diagram of Electrolux vapour absorption refrigeration system and explain its working.

10. (a) A vapour compression system using Ammonia works between -25$\circ$C and 40$^\circ$C as evaporator and condenser temperature respectively. Using P-h Chart, determine

i) COP

ii) Mass refrigerant per TR

iii) Piston displacement per TR using volumetric efficiency = 83%

iv) Heat rejected in the condenser per TR

v) Ideal COP

(b) Draw a neat sketch of Year Round Air Conditioning system and explain working of its components.

11. (a) What are the sources of cooling load for a Restaurant? Discuss in details.

(b) Define body temperature regulation and effects of extremes of hot and cold climate on human body.

(c) A sling psychrometer reads 40$^\circ$C DBT and 28$^\circ$C WBT when atmospheric pressure is 750 mm of Hg.

Calculate using Steam Tables only (i) Specific humidity (ii) Relative humidity (iii) Dew point temperature (iv) Enthalpy

12. Write short notes on any four.

(a) Liquification of Gases

(b) Duct Design Methods

(c) Desirable Properties of Refrigerants

(d) Thermoelectric Refrigeration

(e) Star Rating of Air Conditioners

(f) DART rating of Air Refrigeration Systems.

13. Answer any four of the following:

(a) Explain with neat schematic diagram use of Liquid Suction heat exchanger in a Vapour Compression system.

(b) What are eco-friendly refrigerants? Discuss with examples.

(c) List down types of aircraft refrigeration systems. How are these systems compared on the basis of DART?

(d) A reversed Carnot cycle air conditioner of 1 TR capacity operates with evaporator coil temperature $t_0=7^\circ C$. The surrounding air at 43$^\circ$C is used as cooling medium rising to a temperature of 53$^\circ$C. The temperature of heat rejection is $t_k=55^\circ$. Determine COP, power consumption of the air conditioner and the mass flow rate of surrounding air entering the condenser. Take $C_P$ for air as 1.005kJ/Kg K.

(e) Define RSHF, GSHF and ERSHF.

(f) Discuss advantages of vapour absorption refrigeration system over power vapour compression refrigeration system.

14. (a) In a laboratory test, a psychrometer recorded dry bulb temperature at 34$^\circ$C and wet bulb temperature of 26$^\circ$C. Without using Psychrometric chart, calculate:

(i) Vapour pressure (ii) Relative humidity (iii) Specific humidity (iv) Degree of saturation (v) Dew point temperature (v) Enthalpy of mixture.

Barometric pressure = 740 mm of Hg.

(b) What are different types of Cooling Towers? Explain with a neat sketch and induced draft type Cooling Tower.

(c) What are the sources of cooling load? Explain how will you estimate cooling load of your College Library.

15. (a) A regenerative air refrigeration system for an aeroplane is designed to take a load of 25 TR. The temperature and pressure conditions of the atmosphere are 5$^\circ$C and 0.85 bar. The pressure of the air is increased from 0.85 bar to 1.2 bar due to ramming action. The pressure of air leaving the main compressor is 4.8 bar. 60% of the total heat of the air leaving the main compressor is removed in the heat exchanger and then it is passed through the cooling turbine. The temperature of the rammed air which is used for cooling purposes in the heat exchanger is reduced to 50$^\circ$C by mixing the air coming out from the cooling turbine. The isentropic efficiency of the compressor and turbine and 90% and 80% respectively. The pressure and the temperature required in the cabin are 1 bar and 25$^\circ$C respectively. Assuming isentropic ramming and mass of the cooled air passing through the heat exchanger equal to the mass of cooling air, find: (i) the ratio of by-passed air to the ram air used for cooling purposes; and (ii) the power required for maintaining the cabin at the required condition.

(b) Discuss with block diagram triple fluid Vapour Absorption refrigeration system.

(c) Explain with the help of neat sketch, the working of refrigerating system having three evaporators at different temperatures with individual compressors and multiple expansion valves.

16. (a) A vapour compression system using $NH_3$ works between -15$^\circ$C and 40$^\circ$C as the evaporator and condenser temperature respectively. The vapour is superheated by 5$^\circ$C before entering compressor and liquid is subcooled by 5$^\circ$C. Using P-h chart determine:

(i) COP

(ii) Mass flow of refrigerant per TR

(iii) Piston displacement per TR using volumetric efficiency = 80%

(iv) Heat rejected in the condenser per TR, and

(v) Ideal COP

(b) Draw front and side view of the Window Air Conditioner and explain the various components inside the Unit.

(c) What are the methods of duct design? Explain any one method in detail.

17. (a) The following data refer to an air conditioner space:

Outdoor condition - $38^\circ C, 50\% RH$

Room condition - $24^\circ C, 50\% RH$

Sensible heat load - 26kW

Latent heat load - 8kW

By-pass factor of the cooling coil - 0.16

If the ventilation requirement is such that on a mass flow rate basis, 20% of the fresh air is introduced and 80% of supply is recirculated, determine:

(i) Supply air flow rate

(ii) Outside air sensible heat

(iii) Outside air latent heat

(iv) Grand total heat

(v) Effective room sensible heat factor.

(b) Discuss in details various controls used in Central Plant Air Conditioning system.

18.Write short notes on any four of the following

(a) Types of Condenser and Evaporators

(b) Thermoelectric refrigeration

(c) Year Round Air Conditioning System

(d) Pressure and Temperature Controls

(e) BEE Star Rating System

(f) Bootstrap Cooling System