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Q3. (a) How Leaks are detected and rectified on refrigerating plant? (4)

(b) Describe how suction & discharge valves are tested for tightness? (4)

(c) Describe with an illustration, how refrigerant charging is carried out? (8)

Q7. (a) What are the reasons for foaming in refrigeration compressor crankcase? (4)
(b) Describe the causes for the following in the domestic refrigeration system: (3*4)
(i) Frequent cut-in and cut-out of the compressor.
(ii) Lub oil low pressure cut-out of the compressor.
(iii) High pressure cut-out of the compressor.
(iv) Frosting in the compressor suction side.

Q6. (a) Sketch and describe the operation of the domestic refrigeration system of a ship using freon 22 gas as refrigerant. (8)

(b) Describe the causes for the following in the domestic refrigeration system. (8)

(i) Frequent cut-in and cut-out of the compressor

(ii) Compressor running hot

(iii) High pressure cut out of the compressor

(iv) Frosting in the compressor suction side.

Q9. (a) What do you understand by the term ‘Carnot cycle’ and ‘Reverse Carnot cycle’? (5)

(b) State limitations with cycle. (5)

(c) Explain briefly, absorption type refrigeration cycle with examples using line diagram. (6)

Q7. For a fully automatic provisions refrigeration system incorporating a number of rooms.

A. Explain how each room temperature is set. (4)

B. Describe the sequence of events following a demand for increased refrigerant flow from one room. (4)

C. State with reasons the devices incorporated into the system to protect the machinery and equipment against malfunction. (4)

D. State how satisfactory operation of the plant can be established? (4)

Q4. With reference to a typical shipboard refrigeration system:

a) Sketch the arrangement which controls superheat temperature of refrigerant gas leaving the evaporator. (8)

b) Describe the operation of the arrangement sketched in (a) assuming one of the HFC refrigerants is the working medium. (4)

c) Explain the purpose of the equalizing connection. (4)

Q9. i) In a refrigeration and air-conditioning system, what are the different methods for detecting gas leakage? (3)

ii) Name different types of detectors available and state how they are used to identify point of leakage. What safeties are observed when performing 'leak detection'. (4)

iii) Explain how leakages in the piping system are rectified (a) temporarily (b) permanently? (5)

iv) What records are to be created and maintained whilst carrying out repair / maintenance on the refrigeration system? (4)

Q7.a) Sketch, describe and explain the operation of the domestic refrigeration system of a ship using one of the HFC as refrigerant. What kind of maintenance is essential for the system. (8)

b) Describe the causes for the following in the domestic refrigeration system

i) Frequent cut-in and cut-out of the compressor. (2)

ii) Lub oil low pressure cut-out of the compressor. (2)

iii) High pressure cut-out of the compressor. (2)

iv) Frosting in the compressor suction side. (2)

Q3. Explain the following briefly with reference to a domestic refrigeration system on board a ship. (16)

(a) Ingress of air into the freon system.

(b) Loss of refrigerant from a condenser.

(c) Water in the freon system.

(d) Icing of condenser external surface.