单项选择题When operating with a negative suction head, which of the following types of pumps will require priming?()

A.Reciprocating
B.Centrifugal
C.Rotary
D.Gear


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1.单项选择题The discharge rate or capacity of a centrifugal pump will vary directly as the ().

A.change in the impeller diameter
B.square of the impeller radius
C.cube of the impeller diameter
D.impeller efficiency for large changes in its size

2.单项选择题Which of the following best describes the thermodynamic effect on the pressure and volume relationship with regards to saturated gases?()

A.As pressure decreases, volume increases
B.As volume increases, pressure increases
C.As volume decreases, pressure decreases
D.As pressure increases, volume increases

3.单项选择题To operate a centrifugal fire pump at reduced capacity, you should ().

A.readjust the relief valve
B.throttle the suction line
C.throttle the discharge valve
D.open the priming line

4.单项选择题An AC synchronous transmission type remote steering control system consists of a ().

A.transmitter at the steering station and a receiver at the steering engine
B.reversible motor at the steering station geared to the steering pumps
C.small induction motor on the bridge which controls the redder through pulleys
D.variable displacement hydraulic pump driven by a reversible DC motor

5.单项选择题In which of the areas listed would you expect to find the highest salt concentration in a flash evaporator?()

A.Distiller air ejector cooling medium
B.Saltwater heater discharge
C.First-stage internal feed box
D.Second-stage internal feed box

7.单项选择题The low pressure side of a refrigeration system is considered to exist from the ().

A.expansion valve to the compressor
B.receiver to the expansion coil
C.expansion valve to the evaporator
D.condenser to the expansion valve

8.单项选择题If the electric motor driving an air compressor fails to start, the cause may be a ().

A.leaking unloader
B.tripped circuit breaker
C.control line leak
D.defective pop valve

9.单项选择题The refrigerant gas returning to the compressor should be ().

A.superheated
B.saturated
C.dense
D.flooded

10.单项选择题The vacuum maintained in the salt water feed heater shell of a flash-type evaporator is generally accomplished by ().

A.a separate air ejector unit
B.a direct unimpeded connection between second stage and salt water feed heater
C.either by vacuum drag or an external line from the first stage via a fixed orifice
D.the fixed orifice provided in the steam supply line