單項(xiàng)選擇題Air leakage between the shaft and stuffing box packing in a centrifugal pump is prevented by ().

A.a compressed packing gland
B.lantern tings between the packing rings
C.a liquid seal
D.the stuffing box gland


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1.單項(xiàng)選擇題Tube leaks in the distillate cooler of a two stage flash evaporator will result in ().

A.loss of second stage vacuum
B.contamination of the distillate
C.lower feed inlet temperature
D.contamination of the second stage condenser

2.單項(xiàng)選擇題The pressure of a liquid leaving the pump can be referred to as the ().

A.total head
B.discharge head
C.net positive suction head
D.suction head

4.單項(xiàng)選擇題Which of the following statements describes the relationship between viscosity and specific gravity?()

A.Liquids with different viscosities will always have the same specific gravity
B.Liquids with different viscosities will never have the same specific gravity
C.Viscosity and specific gravity are directly proportional
D.Viscosity and specific gravity are not related in that one does not define or limit the other

5.單項(xiàng)選擇題Some chloronated flourocarbon refrigerants may decompose into a toxic irritating gas if it is ().

A.stored at temperatures below 60 degrees Fahrenheit
B.charged into a system having copper fittings
C.allowed to mix with compressor oil
D.exposed to an open flame or hot surface

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If the head pressure of a reciprocating refrigeration compressor is excessive, ().

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The major source of chemical contaminants in hydraulic fluid is ().

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The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?()

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The output volume of a positive fixed displacement pump can be changed only by ().

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If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump ().

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The rate of heat transfer from a hot region to a cold region is affected most by the ().

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When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should ().

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The control mode in which the final control element is moved from one of two flexed positions to the other is known as ().

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An excessive charge of refrigerant in an air-cooled refrigeration system can cause ().

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Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?()

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