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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)

Q5. With respect to refrigeration gases used on-board vessels, answer the following:

A. Explain Ozone Depleting Potential (ODP) and Global warming potential (GWP) of conventional refrigerant gases.

B. Name the alternate refrigerant gases available and being used onboard.

C. Explain the steps you will take to ensure that release of refrigerant gases from the plant in minimized during normal operation and during maintenance activities.

Q3. Explain vapor compression refrigeration cycle on T-S and PH diagram and explain the purpose of EACH of the following:

(a) Expansion valve

(b) Room thermostat

(c) High pressure cut out.

(d) Equalizing line.

Q9. With respect to the refrigeration system on board vessels, answer the following
a) Why are some TEVs fitted with an external equalising connection?

b) What is the purpose of a back pressure valve. what will the effect if it leaks?

c)How does an electronic TEV function.

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.