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单选题
The steam coils in a high pressure evaporator used for saltwater service should be de-scaled with （）.
A
a needle gun
B
soap and water
C
a wire brush
D
a chipping hammer
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更多 “单选题The steam coils in a high pressure evaporator used for saltwater service should be de-scaled with （）.A a needle gunB soap and waterC a wire brushD a chipping hammer” 相关考题
考题
The expansion valve used in a refrigeration system regulates theA.superheat of the gas leaving the compressorB.back pressure in the evaporatorC.temperature in the refrigerated spaceD.degree of superheat of the gas leaving the evaporator
考题
A thermostatic expansion valve is properly controlling evaporator superheat. Adjusting this valve to lower the superheat will result in a/anA.evaporator pressure decreaseB.evaporator coil over-feedC.evaporator capacity increaseD.expansion valve diaphragm rupture
考题
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?A.A shortage of liquid refrigerant.B.Excessive frost on the evaporator.C.Excessive condenser cooling water.D.Insufficient condenser cooling water flow.
考题
If the feed pump for an auxiliary boiler fails to deliver the feed water to the boiler, the cause may be ______.A.high steam pressure in the boilerB.abnormally high feed-water temperatureC.abnormally high boiler water temperatureD.steam demand exceeding feed pump capacity
考题
Which of the listed problems could produce a high absolute pressure within a flash type evaporator?A.production of high salinity distillateB.seawater feed temperature below 165℃C.a leak in the first stage demisterD.a cracked distillate pump vent line
考题
Geothermal(地热)Energy
1 Since heat naturally moves from hotter regions to cooler ones, the heat from the earth's center flows outwards towards the surface. In this way, it transfers to the next layer of rock. If the temperature is high enough, some of this rock melts and forms magma(岩浆). The magma ascends in its turn towards the earth's surface. It often remains well below the earth's surface, creating vast areas of hot rock. In such regions, there are deep cracks, which allow rainwater to descend underground. Some of the heated rainwater travels back up to the earth's surface where it will appear as a hot spring. However, if this ascending hot water reaches a layer of impermeable(不可渗透的)rock, it remains trapped, forming a geothermal reservoir. If geothermal reservoirs are close enough to the surface, they can be reached by drilling wells. Hot water and steam shoot up the wells naturally, and can be used to produce electricity in geothermal power plants.
2.A few geothermal power plants depend on dry-stem reservoirs which produce steam but little or no water. In these cases, the steam is piped up directly to provide the power to spin a turbine generator. The first geothermal power plant, constructed at Lardarello in Italy, was of this type, and is still producing electricity today.
3.Most currently operating geothermal power plants are either "flash" steam plants or binary(双重的)plants. Flash plants produce mainly hot water ranging in temperature from 300° to 700°Fahrenheit. This water is passed through one or two separators where released from the pressure of the underground reservoir, it "flashes" or boils into steam Again, the force of this steam provides the energy to spin the turbine and produce electricity. The geothermal water and steam are then reinjected directly back down into the earth to maintain the volume and pressure of the reservoir. Gradually they will be reheated and can then be used again.
4.A reservoir with temperatures below 300° Fahrenheit is not hot enough to flash steam but it can still be used to generate electricity in binary fluid. The steam from this is used to power the turbines. As in the flash steam plant, the geothermal water is recycled back into the reservoir.
文章(23~30)
Paragraph1_____A.Dry steam plants
B.Binary plants
C.Origin of geothermal energy
D.Generation of electricity
E.Flash steam plants
F.Recyclable water and steam
考题
单选题The device used for low-pressure control and high-pressure cutout on a compressor is called a（）A
cutoutB
pressure controllerC
controller switchD
cutout switch
考题
单选题Which of the listed problems could produce a high absolute pressure within a flash type evaporator?（）A
Production of high salinity distillateB
Seawater feed temperature below 165℃C
A leak in the first stage demisterD
A cracked distillate pump vent line
考题
单选题If the high-pressure switch on the compressor opens and stops the compressor a possible cause could be:（）A
too much cooling water going through the condenserB
not enough refrigerant in the systemC
a leak in the evaporator coilsD
no enough cooling water going through the condenser
考题
单选题To assist separation of low viscosity oils steam coils or electric heaters are fitted （） of the oily water separator.A
in entranceB
in exitC
in the upper partD
on the outside
考题
单选题Hot gas bypass is one of the methods used to （）A
relieve excessive compressor head pressureB
produce flash gas at the expansion valveC
reduce flooding of the receiver at low loadD
defrost the evaporator coils
考题
单选题The bulb for the thermal expansion valve is located（）A
in the middle of evaporator coilsB
near the evaporator coil outletC
near the evaporator coil inletD
on the bottom row of evaporator coils
考题
单选题Which of the following statements is true concerning any evaporator?（）A
High conductivity of the distillate indicates distillate salinity is excessiveB
Increasing the absolute pressure of the shell will increase the distillers capacityC
Mesh separators are used in evaporators to filter the distillateD
Reducing the brine density will reduce the heat lost overboard
考题
单选题When normal operating pressure is applied to the hydraulic oil used in a high-pressure system, the oil （）.A
viscosity will decreaseB
volume will increaseC
volume will decreaseD
pour point will be reduced
考题
单选题The direction of the surface wind is（）.A
directly from high pressure toward low pressureB
directly from low pressure toward high pressureC
from high pressure toward low pressure deflected by the earth's rotationD
from low pressure toward high pressure deflected by the earth's rotation
考题
单选题Thermostatic steam pressure reducing valves are used in the fuel oil service system to control the（）A
double bottom fuel oil tank temperatureB
heater supply steam flowC
pressure of the fuel supplied to the burnersD
attemperator steam flow in the heater discharge circuit
考题
单选题One cause of high head pressure occurring in a refrigeration system can be （）.A
insufficient cooling water flow to the condenserB
a low refrigerant charge in the systemC
the liquid valve is open too muchD
high evaporator superheat
考题
单选题Seamless mild steel is used for steam (also copper for moderate pressure and temperature), h-pair, feed discharge and all oil fuel pressure pipingsAccording to the above sentence, which of the following statements is not true?（）A
Both seamless mild steel and copper may be used for middle pressure steamB
hpair means high pressure airC
The feed piping of the boilers can be made of seamless mild steelD
All oil pipings are made of mild steel
考题
单选题Which of the conditions listed represents the greatest effect of excess frost accumulation on the evaporator coils?（）A
Keeps the refrigerated space coolerB
Reduces the efficiency of the plantC
Takes the load off the compressorD
Has no affect on the system
考题
单选题Which one of the followings might not be employed to create vacuum for flash type evaporator? （）A
high-pressure steam-driven air-ejectorB
motor-driven vacuum pumpC
water-motivated air eductorD
centrifuge pump
考题
单选题The boiler feed pump discharge pressure is higher than the steam drum pressure to （）.A
ensure feed water flow into the boilerB
keep the steam drum pressure highC
prevent water hammer in the feed lineD
help the feed water flash to steam
考题
单选题The water level in a steaming auxiliary boiler will always （）A
rise when the steam pressure is increasedB
remain constant as long as the feed pump operatesC
fall when the steam pressure is decreasedD
vary as the steam demand changes
考题
单选题Which of the following pumps is used where a relatively high pressure and small capacity are required?（）A
Volute pumpB
Diffuser pumpC
Regenerative pumpD
All of the above
考题
单选题Cast iron and gunmetal fittings are used freely in small sizes at moderate pressure; large fittings, those for high pressure and temperature are cast or mild steelIn the above sentence, the word “those” means （）.A
east iron firingsB
mild steel fittingsC
small fittingsD
large fittings
考题
单选题Soot blowers should be used in proper sequence so that（）A
excess stresses will not be set up in the boilerB
the decks will not be covered with sootC
the soot will be swept toward the uptakesD
there will not be a loss of steam pressure
考题
单选题The thermal expansion valve responds to the（）A
amount of superheat in the vapor leaving the coilB
amount of superheat in the liquidC
temperature in the evaporator coilsD
pressure in the evaporator coils
考题
单选题If the feed pump for an auxiliary boiler fails to deliver the feed water to the boiler, the cause maybe （）.A
high steam pressure in the boilerB
abnormally high feed water temperatureC
abnormally high boiler water temperatureD
steam demand exceeding feed pump capacity
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