Register Number
SATHYABAMA UNIVERSITY
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - P-MECH
Title of the Paper :Refrigeration and Air Conditioning Max. Marks:80
Sub. Code :615PTE05(2007-08-09)
Time : 3 Hours
Date :15/05/2012
Session :AN
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1.
PART - A
(10 x 2 = 20)
Answer ALL the Questions
Name the important components of a simple vapour compression
refrigeration system.
2.
What is an azeotrope? Give example.
3.
What do you mean by hermetic sealed compressor? Give its
advantage.
4.
What are the factors that affect that affect the heat transfer
capacity of an evaporator?
5.
What is function of thermostat in refrigeration system?
6.
Why is balancing of components of a refrigeration system
required?
7.
Define dew point temperature.
8.
What is bypass factor of cooling or heating coil?
9.
Define room sensible heat factor. How room sensible heat factor
is drawn on a psychrometric chart?
10. Define the following
(a) fan total pressure
(b) Fan total efficiency.
PART – B
(5 x 12 = 60)
Answer All the Questions
11. Describe the mechanism of simple vapour compression
refrigeration with neat sketch. Also sketch the T-s and P-h
diagrams for the vapour compression refrigeration cycle.
(or)
12. Explain the designation system of a refrigerant. How will you
assign number to the refrigerants methyl chloride (CH3Cl) and
tetra-chloroethane (C2H4Cl4)
13. Explain, with the help of neat sketch, the principle of operation of
screw compressor and scroll compressor.
(or)
14. Discuss the natural convection and forced convection types of air
cooled condensers.
15. Discuss the principle of pressure actuated cycling control with
neat sketch.
(or)
16. Discuss the graphical analysis of system equilibrium.
17. The readings of a sling Psychrometer are as follows: dry bulb
temperature=30º C; wet bulb temperature = 20º C. Determine
1. Dew point temperature;
2. Relative humidity;
3. Specific humidity;
4.Degree of saturation;
5. Vapour density; and
6. Enthalpy of moist air.
(or)
18. 800 m3/min of re-circulated air at 22ºC DBT and 10ºC dew point
temperature is to be mixed with 300 m3/min of fresh air at 30ºC
DBT and 50% RH. Determine the enthalpy, specific volume,
humidity ratio and dew point temperature of the mixture.
19. Draw a neat diagram of air- conditioning system required for
summer season. Explain the working of different components in
the circuit.
(or)
20. A hall to be maintained at 24ºC dry bulb temperature and 60%
RH under the following conditions:
Out door conditions= 38ºC DBT and 28ºC WBT
Sensible heat load of the room = 46.4 kW
Latent heat load in the room = 11.6 kW
Total infiltration air = 1200 m3/hr
Apparatus dew point temperature = 10ºC
Quantity of re-circulated air from the hall =60%
If the quantity of re-circulated air is mixed with the conditioned
air after the cooling coil, find the following:
a) The condition of air leaving the conditioner coil and before
mixing with the re-circulated air;
b) The condition of air before entering the hall;
c) The mass of air entering the cooler;
d) The mass of total air passing through the hall;
e) The by-pass factor of the cooling coil;
f) The refrigeration load on the cooling coil in tonnes of
refrigeration.