Reg Non 00000ME4051219hame:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Seventh semester B.Tech examinations (S), September 2020

Course Code: ME405
Course Name: REFRIGERATION AND AIR CONDITIONING
Max. Marks: 100 Duration: 3 Hours
Use of chart and tables are permitted
PART A
Answer any three full questions, each carries 10 marks. Marks

1 a) Prove that COP Heat Pump= COP Refrigerator + 1. Use necessary sketches to (5)
justify your answer.
b) What are the limitations of reversed Carnot cycle? What is the significance of (5)

Carnot cycle?

1௮

With the help of the schematic, T-s and P-h diagrams describe the working ofa (10)
simple vapour compression refrigeration system. Also write down the
expressions to find out the Capacity, Compressor work and COP of the system.

3 The cooling load of a new Boeing aeroplane is 10 Tonnes. A boot strap cooling (10)
system is proposed. The temperature and pressure conditions of the
atmospheric air are 20°C and 0.9 bar. The cabin pressure is 1.02 bar and
temperature of air leaving the cabin should be greater than 25°C. The pressure
of air will be increased from 0.9 bar to 1.1 bar due to ramming and this process
is considered isentropic. The pressures of air leaving the main and auxiliary
compressor will be 3 bar and 4 bar respectively. Isentropic efficiency of
compressors and turbine to be used are 0.85 and 0.8 respectively. It is
considered that 50% of the total heat of air leaving the main compressor is
removed in the first heat exchanger and 30% of the total heat of air leaving the
auxiliary compressor is removed in the second heat exchanger. Calculate 1) the
power required to take heat load of the cabin and 2) the COP of the system.

4 A vapour-compression refrigeration system use Refrigerant 134a as the (10)

working fluid. The R134a flow rate is 6 kg/min. The refrigerant enters the

compressor at -10°C and 1.4 bar. The isentropic compressor efficiency is 70%.

The refrigerant leaves the condenser at 24°C and 7 bar. There are no

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