Reg. No. ________
Karunya University
(Karunya Institute of Technology and Sciences)
(Declared as Deemed to be University under Sec.3 of the UGC Act, 1956)
End Semester Examination – November/December 2010
Subject Title:
Subject Code:
REFRIGERATION AND AIR CONDITIONING
09ME238
Time : 3 hours
Maximum Marks: 100
Answer ALL questions
PART – A (10 x 1 = 10 MARKS)
1.
2.
3.
Define Cascade system.
Sketch the T-s diagram for boot strap air cooling system.
Mention any two differences between reciprocating compressor and rotary compressor and
rotary compressor.
4. Mention four biological applications of refrigeration system.
5. Define by pass factor.
6. What you understand about comfort air-conditioning?
7. Define Room sensible Heat Factor (RSHF).
8. What is fog?
9. Mention the different types of cooling water.
10. Define air-washer.
PART – B (5 x 3 = 15 MARKS)
11. 2 kW per tonne of refrigeration is required to maintain the temperature of -40oC in the
refrigerator. If the refrigeration cycle works on Carnot cycle, determine the (a) COP of the
cycle and (b) temperature of the sink.
12. Write a short note on cryogenic in medicine application.
13. Air has a dry bulb temperature of 30oC and 50% relative humidity. Find the dew point
temperature, enthalpy.
14. Explain the procedure to draw a Grand Sensible Heat Factor (GSHF) line on a Psychrometric
chart.
15. Discuss the thermal insulation of air-conditioning system.
PART – C (5 x 15 = 75 MARKS)
16. A vapour compression system works between the pressure limit of 60 bar and 25 bar. The
working fluid is just dry at the end of compression and there is no undercooling of the liquid
before the expansion valve. Determine the (a) COP of the cycle, and (b) capacity of the
refrigerator, if the fluid is at the rate of 5 kg/min.
(OR)
17. Explain the function of lithium bromide water absorption system. List the major application of
this system.
18. a.
b.
19. a.
b.
What are the desirable properties of an ideal refrigerant?
(7)
Differentiate between short-term and long-term storages.
(8)
(OR)
Discuss the natural convection and forced convection types of air cooled condensers. (7)
Discuss the refrigeration plant testing and charging.
(8)
[P.T.O]
20. 800 m3/min of recirculated air at 22oC DBT and 10oC dew point temperature is to be mixed
with 300 m3/min of fresh air at 30o DBT and 50% relative humidity. Determine (a) specific
volume (b) humidity ratio and (c) dew point temperature of the mixture.
(OR)
21. a. What is “Effective Temperature”? What are the factors affecting it?
(10)
b. When is dehumidification of air necessary?
(5)
22. The following data refer to summer air-conditioning of a restaurant:
Inside design condition
= 27oC DBT and 21oC WBT
Outside design conditions
= 38oC DBT and 27oC WBT
Sensible heat load
= 126000 kJ/h
Latent heat load
= 50400 kJ/h
The outside air is supplied at the rate of 20 m3/min directly into the room through ventilators
and by infiltration. The outside air to be conditioned is passed through a cooling coil which has
an apparatus dew point of 12oC and 60% of the total air is recirculated from the conditioned
space and mixed with conditioned air after the cooling coil. Find (a) condition of air after the
cooling coil before mixing with recirculated air (b) condition of air entering the restaurant (c)
by-pass factor of the cooling coil.
(OR)
23. The room sensible and latent heat loads, for an air conditioned space are 25 kW and 5 kW
respectively. The room condition is 25oC dry bulb temperature and 50% relative humidity.
The outdoor condition is 40oC dry bulb temperature and 50% relative humidity. The
ventilation requirement is such that a mass flow rate basis 20% of fresh air is introduced and
80% of supply air is recirculated. The by-pass factor of the cooling coil is 0.15.
24. a.
b.
25. a.
b.
Explain the air transport and rail transport refrigeration system.
Describe the different methods of air conditioning duct design.
(OR)
Discuss the various type of air distribution system.
Explain spray pond.
(10)
(5)
(10)
(5)