單項選擇題The heat required to change a substance from a solid to a liquid while at its freezing temperature, is known as the latent heat of （）.

A.fusion
B.vaporization
C.condensation
D.sublimation


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1.單項選擇題With reference to a vessel’s structural integrity, the most significant characteristic of a cryogenic liquid is its （）.

A.capability of causing brittle fractures
B.highly corrosive action on mild steel
C.vapor cloud which reacts violently with saltwater
D.toxicity at atmospheric pressure

2.單項選擇題The only means of removing the latent heat of condensation from a refrigerant in the normal refrigeration cycle is by （）.

A.passing it through the expansion valve
B.condensing refrigerant in the system condenser
C.passing the gaseous refrigerant through the heat interchanger on the suction side of the compressor
D.maintaining a high pressure on the systems receiver

3.單項選擇題In a refrigeration system, the refrigerant absorbs the latent heat of vaporization in the（）.

A.compressor
B.condenser
C.receiver
D.evaporator

4.單項選擇題The FIRST thing to do to ensure that a refrigeration unit will not start while undergoing repairs, is to （）.

A.secure and tag the electrical circuit
B.place a crow bar in the flywheel of the unit
C.inform all persons in the area not to start the unit
D.make a log book entry

5.單項選擇題One of the main differences between the various types of screw pumps is in the （）.

A.stuffing box diameter
B.direction of rotation of the screws
C.pitch of the screws
D.type of driving gears