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Q5) With regard to a reciprocating refrigerator compressor.

(a) Sketch the mechanical shaft seal showing its component parts and how it is lubricated (8)

(b) Describe the sealing arrangement stating the materials used for the component parts (4)

(c) State the effect on the environment of the release of refrigerants into the atmosphere (4)

Q8. (a) Explain 'short cycling' in the context of refrigeration and air conditioning systems onboard ship. State its causes and how it can be avoided. (6)
(b) State the symptoms of 'overcharging' and 'undercharging' in refrigeration system. What are its effects and state remedial measures (5)
(c) What are the visible indicators of oil in refrigeration system. What would be its effects? State remedial measures (5)

Q9. (a) Make a detailed sketch of a direct expansion two room refrigeration system. (10)

(b) Give a full description of such a Refrigeration System, explaining the purpose of the relevant control and safety devices. (6)

Q4) (a) Make a detailed sketch of a Ship's domestic refrigeration system. (8)

(b) Give a full description of such a Refrigeration System, explaining the purpose of the relevant control and safety devices. (8)

Q5. (a) Describe how air in the refrigeration plant is purged out (6)

(b) Describe how lube oil is added in the refer compressor (5)

(c) Describe how the lube oil filter of a reefer compressor is cleaned (5)

Q8. With reference to the lubrication of refrigeration compressors:

a) State the advantage of using fully synthetic oils

b) Explain why oil may be carried over from the compressor

c) Describe a device which returns oil from the compressor discharge to the compressor sump

d) State the reasons why an accumulation of oil in the evaporator is undesirable.

1. Q5. a) With reference to a vapour compression refrigeration plant, explain why each of the following conditions are desirable;

(i) Superheating at the compressor suction

(ii) Undercooling at the condenser outlet

(b) Describe, with the air of a pressure-enthalpy diagram, how the evaporator cooling load is affected by the conditions stated in Q5 (a)

Q9. With reference to main refrigeration plants give reason for each of the following

operational irregularities and state how these are dealt with: -

(a) Rapid loss of lubricating oil from the crankcase of a “vee” block compressor; (4)

(b) Steady “fall off " in refrigeration effect over a comparatively short period of time; (4)

(c) Excessive “icing up" at compressor suction; (4)

(d) Short cycling. (4)

Q5. Describe the functional components of a reefer plant for the domestic refrigeration. system and temperatures to be maintained in different cold rooms; (8)

i) Describe the pressure switches; (2)

(ii) The tubular heat exchanger; (2)

(iii) The Oil separator and, (2)

(iv) The drier system. (2)

Q2. With reference to main refrigeration plant give reason for each of the following operational irregularities and state how these are dealt with:

a) Rapid loss of lubricating oil from the crankcase of a "vee" block compressor. (4)

b) steady "fall off" in refrigeration effect over a comparatively short period of time. (4)

c) Excessive "icing up" at compressor suction. (4)

d) Short cycling. (4)

Q9. a) What are the reasons of frosting in the refrigeration chambers and its effect. (6)

b) What are the methods used for defrosting refrigerated chambers? (6)

c) What is the arrangement of Reefer Chamber drains. (4)

Q7. a) How leaks are detected and rectified on refrigerating plant? (4)

b) Describe how Suction & Discharge valve are tested for tightness? (4)

c) Describe how refrigerant charging is carried out? (8)