Rac
Rac
Rac
136 S 51
FOUR YEAR ts.TECH. DEGREE EXAMINATION _ APRIL, 2016.
MECHANiCAL ENGINEERING
REFRIGERATION AND AIR CONDITIONING (RAC)
(scHEME - 2013)
Question No. 1 carries 10 marks and remaining questions carry 15 marks each.
Use of Thermal Data Handbook is Permitted.
1. (a) Define ton of refrigeration.
(b) List different types of refrigerants used in air conditioners.
(c) What is a cooling tower?
(d) What are zeotropes?
(e) What are the desirable properties of absorbent?
(0 What is Peltier effect?
(e) What is ozone depletion potential?
(h) Define wet bulb depression
(i) Represent chemical dehumidification on psychrometric chart.
CI) What is infiitrated ioad?
2. (a) Differentiate between wet and d.ry compression. (5)
(b) A coz refrigerator works between 56.25 bar and 2L.2 bar. The
temperature of vapour leaving compressor is 32oC, Determine
(i) Dryness fraction of vapour entering and leaving the evaporator,
(il) COP. Take enthalpy of COz = 245,78 KJIKg at the end' of
compression. Properties of COz are : (10)
Sat. Sta. Enthalpy KJIIk Entropv KJ/Kg
Pr. (bar) Temp ("C) Liquid Vapour Liquid Vapour
56.25 18.5 52.67 2L4.02 0,t672 0.7231
2r.2A -18.0 -3?.60 2g4.50 *0.1505 0.9154
Turn Over
3. A refrigeration system is run by a engine. The actual cop of refrigeration
system is 70% of ideal cycle and efficiency of the engine is 50% of ideal. The
heat is supplied to the engine at 1000'C and rejected to atmosphere at 30oC.
The refrigerator has to maintain the temp of -10oC. If the load on ,the
refrigerator is 40 TR, find the heat supplied to the engine. (15)
(b) With the help of a neat sketch explain the working of a thermostatic
expansion valve. (8)
5. (a) Explain the working principle of actual aqua ammonia vapour absorption
refrigeration cycle. (9)
(b) What are the advantages of vapour absorption system over vapour
compression system? (6)
2 136 s 51