單項(xiàng)選擇題The degree to which the viscosity of an oil will change with a change in temperature is indicated by the ().

A.weight designation
B.viscosity index
C.pour point
D.thermal change value


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2.單項(xiàng)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

3.單項(xiàng)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

4.單項(xiàng)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

5.單項(xiàng)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