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.
Q7. With reference to air conditioning units
a) With the aid of a sketch, explain the operation of a unit that includes means of dehumidifying, humidifying, and refrigerated cooling.
b) (i) Describe the conditions that could lead to legionella growth.
(ii) List the precautions necessary in the maintenance of air conditioning systems to reduce the risk of legionnaires disease being contacted.
Q7. a) Explain with a sketch the operation of an automatic expansion valve as fitted in the direct expansion refrigeration plants. How is this valve adjusted? (6)
b) Explain how critical temperature restricts plant operation and how these limitations can be overcome? (5)
c) Explain how this system maintains the provision rooms at different temperatures? (5)
Q7. With respect to the refrigeration system on board vessels, answer the following
a) Why are some TEVs fitted with an external equalizing connection?
Q6. With Respect to Container Ship: -
A. Sketch a ship’s indirect refrigeration system arranged for cooling containers stowed in stacks in the hold;
B. Describe the refrigeration system sketched in (A);
C. State the advantages of the system described in (A) compared with containers with their own refrigeration self-contained units.
Q9. (a) For Freon-22 vapor compression refrigeration machine, state how each of the following faults are indicated and how they are remedied:
(i) Air in the system
(ii) Moisture in the system
(iii) Undercharge
(iv) Overcharge
(b) Describe with a diagram detailing the devices incorporated into the refrigeration system to protect the machinery and equipment against malfunction.
Q6. With regard to refrigeration system explain;
A. What are the possible reasons for HP cut out in the refrigeration system?
B. What are the indication if air is present in the refrigerant system and how to remove air from refrigeration system?
C. How unloader works in refrigeration system?
D. What are the possible reasons for Icing on evaporation coil?
E. Why compound gauge fitted in refrigeration system?
Q8. Detail the desirable properties of a refrigerant. Make a table and compare following refrigerants for use in a provision cooling plant for a 50000 DWT Oil tanker: R-22, R-134a.
Q6. A. Draw a block diagram for a fully automated accommodation air conditioning unit, labelling the component parts and indicating the directions of air flow; B. Explain why the unit includes means of dehumidification and humidification; C. A chart is used for ensuring that the accommodation conditions are within the so-called Comfort Zone: what useful information does the chart give?
Q9. With reference to ships air conditioning plants:
(a) state the temperatures and relative humidity at EACH of the points that are regarded as the boundaries of the comfort zone;
(b) explain how the temperatures and relative humidity could be maintained within the comfort zone when the ship is in EACH of the following locations:
(i) North West Europe in winter;
(ii) Arabian Gulf in summer.
(c) State with reasons FOUR locations within the accommodation that conditioned air must not be recirculated.
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