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Marine engineer officer exam question and answer

Under sized expansion valve

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December 12, 2021

1.in low load no problem

2.during high load flow will be less.

3. High degree of superheat so compressor running long time and become hot.

4.room temp. Will rise.

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Oversized expansion valve

December 12, 2021

1. In high load ,no problem. 2.during low load ,flow will more. 3. Low degree of superheat tev close so short cycling. 4. Ice formation on evaporator and suction side 5.liquid hammer on compressor

High specific enthalpy of vaporization

December 13, 2021

It is the property of refrigerant .this property makes it attractive because 1.reduce the quantity of refrigerant in circulation 2. We can use lower speed machine and small plant 3.increase cofficent of performance

What is bumping clearance? What happens if bumping clearance too much or too little.

December 14, 2021

✍️What is bumping clearance? What happens if bumping clearance too much or too little. 1) Bumping clearance is to accommodate thermal expansion and to avoid piston hitting the cylinder cover head. 2) A clearance is given between piston head and cylinder head at piston TDC 3) Bumping clearance should be as small possible, high clearance reduce volumetric efficiency 4) Low clearance will result in mechanical fault 5) Bumping clearance to be checked and measured every major overhaul 6) Bumping clearance normally 6% of swept volume 7) Bumping clearance affect by thickness of gasket and bearing wear,