Question Paper: Refrigeration And Air Conditioning Question Paper - Dec 17 - Mechanical Engineering (Semester 8) - Mumbai University (MU)
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## Refrigeration And Air Conditioning - Dec 17

### Mechanical Engineering (Semester 8)

Total marks: 80
Total time: 3 Hours
INSTRUCTIONS
(1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Draw neat diagrams wherever necessary.

1. Answer the following question (any four)

1.a. Define (i) Refrigeration (ii) Ton of Refrigeration (iii) Air Conditioning (iv) Coefficient of Performance.
(4 marks) 10350

1.b. Explain difference between vapour compression refrigeration system and vapour absorption refrigeration system.
(4 marks) 7573

1.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.
(6 marks) 10293

1.d. What are the desirable properties of refrigerants? Compare primary and secondary refrigerants.
(6 marks) 10321

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.

(6 marks) 12720

2.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.

(14 marks) 10297

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

(12 marks) 12626

3.b. What are the types of expansion valve? Explain the working of thermostatic expansion valve.
(8 marks) 10318

4.a. Discuss various psychometric processes that can be achieved by using an air washer.
(10 marks) 12721

4.b. Explain the various methods of duct design.
(10 marks) 10376

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

(14 marks) 12722

5.b. Classify different types of compressors. Explain each type in brief.
(6 marks) 10325

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

6.a. Central air conditioning system.
(5 marks) 10363

6.b. LiBr-Water vapour absorption system.
(5 marks) 10344

6.c. Controls used in Refrigeration and Air Conditioning.
(5 marks) 10361

6.d. Vortex Tube Refrigeration.
(5 marks) 10343

6.e. Steam jet refrigeration.
(5 marks) 10345

6.f. Liquification of gases.
(5 marks) 10377