6

4

10

a)

b)

a)
b)

a)

b)

a)

b)

G1064 Pages: 3

Derive an expression for COP of an Reversed Brayton cycle air refrigeration
system

A regenerative air cooling system is used for an airplane to take 20 TR. The
ambient air at a pressure of 0.8 bar and temperature 10°C is rammed
isentropically till pressure rises to 1.2 bar. The air bled off the main compressor
at 4.5 bar is cooled by the ram air in the heat exchanger whose effectiveness is
60%. The air from the heat exchanger is further cooled to 60°C in the
regenerative heat exchanger. The cabin is to be maintained at a temperature of
25°C and pressure of | bar. If the isentropic efficiencies of compressor and
turbine are 90% and 80% respectively, Find (1) Mass of air bled from cooling
turbine to be used for regenerative cooling (2) Power required and (3) COP.

PART 13
Answer any three full questions, each carries 10 marks.

A two stage vapour compression machine with a flash inter cooler is to produce
30 TR while working between -35°C and 45°C. The pressure in the flash cooler
is the geometric mean of the upper and lower limits. The suction gas to the low
pressure compressor is super heated by 5°C and the condenser liquid is sub
cooled by 5°C. The working substance is R-12. Determine (i) COP (ii) power
(iii) Fluid flow through LP and HP compressor
Explain working of a refrigeration system with multiple evaporators of different
capacity with figure.
Explain with a neat diagram working of a domestic refrigerator
Compare deep freezing and cold storage
Explain any one type of commonly used cooling tower with a diagram
PART ட

Answer any four full questions, each carries 10 marks.
Air at 25°C, 70% RH and | bar is compressed to 2 bar and cooled back to 25°C.
Find water condensation per kg of air
Define the terms: (a) DPT, (b) RH (c) WBT (d) SHF and show them on a
psychrometric chart
With the help of a neat diagram, explain the working of a winter air conditioning
system
Derive Bernoulli’s equation from energy equation through second law

considerations.

Page 2of 3

(4)

(6)

(10)

(10)

(6)

(4)
(10)

(6)

(4)

(6)

(4)