單項(xiàng)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


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1.單項(xiàng)選擇題The temperature at which water vapor in the atmosphere begins to condense is called the （）.

A.dew point temperature
B.condensation temperature
C.psychometric temperature
D.absolute humidity temperature

2.單項(xiàng)選擇題The tendency for lubricating oil to thin out at high temperatures and thicken at low temperatures will be characterized by a （）.

A.low viscosity index
B.high viscosity index
C.high neutralization number
D.low demulsibility quality

3.單項(xiàng)選擇題Increasing the speed of a rotary pump above its rated speed will result in which of the following conditions to occur?（）

A.Loss of suction
B.Increased clearances
C.Decreased clearance
D.Decreased slippage

4.單項(xiàng)選擇題The dew point of air is reached when the wet bulb temperature is （）.

A.Twice the dry bulb temperature
B.10℃ above the dry bulb temperature
C.5℃ above the dry bulb temperature
D.Equal to the dry bulb temperature

5.單項(xiàng)選擇題Which of the listed problems could produce a high absolute pressure within a flash type evaporator?（）

A.Production of high salinity distillate
B.Seawater feed temperature below 165℃
C.A leak in the first stage demister
D.A cracked distillate pump vent line