In a chilled water air conditioning unit using a reciprocating compressor, the refrigerating effect of the primary refrigerant can be increased by （）.
A . increasing refrigerant pressure in the coil
B . increasing chilled water flow through the cooler
C . sub-cooling the refrigerant in the condenser
D . superheating the refrigerant in the compressor
相似题目
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Air bubbles in a hydraulic governor can cause （）
A . sluggish response
B . speed droop variations
C . isochronous governing
D . sensitivity increase
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If a small electric motor is immersed in salt water it should be （） (1) washed in fresh water (2) dried in an oven
A . (1) only
B . (2) only
C . both (1) and (2)
D . neither (1) or (2)
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The latent heat of water vapor in air is dependent upon the （）
A . dry bulb temperature
B . wet bulb temperature
C . dew point
D . dry point
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Compared to a low pressure system，generally the air in a high is（）.
A . warmer，less dense，and less stable
B . cool，more dense，and drier
C . muggy and cloudy
D . extremely moist with high relative humidity
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After "F.W.E" is given, the air system is shut down, the （） gear put in, all drains and indicator cocks opened, and the cooling water kept running.
A . steering
B . timing
C . turning
D . running
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For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should remain constant regardless of load changes?（）
A . Chilled water system supply temperature
B . Chilled water system return temperature
C . Compressor discharge temperature
D . Compressor suction pressure
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The fresh air coming in through the inner air ports, is compressed by（） to a higher pressure.
A . the cylinder head
B . the cross-head
C . the moving piston
D . the stationary pisto
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Relative humidity is the percentage of water vapor that is in the air as compared to the maximum amount it can hold at（）.
A . a specific barometric pressure
B . a specific temperature
C . a specific wind speed
D . any time
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The most serious effect of air trapped in a diesel engine jacket water cooling system is that it（）.
A . causes colloid suspension in the cooling water
B . reduces the capability of the lubrication system
C . can form pockets which block the flow of coolant through the system
D . leads to the scuffing of cylinder wall
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A yellow signal floating in the air from a small parachute，about 300 feet above the water，would indicate that a submarine（）.
A . has fired a torpedo during a drill
B . is about to rise to periscope depth
C . is on the bottom in distress
D . is disabled and unable to surface
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A restricted air intake to a diesel engine may result in the engine （）.
A . failing to reach rated speed
B . knocking under maximum load
C . hunting or surging under light load
D . overspeeding and running away
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（）reters to be amount of water vapour in the air.
A . Humidity
B . Temperature
C . Precipitation
D . Wind
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Defective air cooler in a diesel engine will lead to （）.
A . smoky exhaust
B . starting failure
C . overload
D . over speed
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Cast irons weakness in tension and under shock loading limits its use to low pressure steam, air, oil and low speed water fittingsThe above sentence, most probably means （）.
A . cast iron has weakness
B . cast iron can stand up shock loading
C . cast iron fittings are only suitable in low pressure situation
D . east iron fittings are not suitable in low pressure situatio
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Too much excess air is （）because the heat generated is being lost through the exhaust trunking instead of being made used of in heating the water to produce steam.
A . not good
B . good
C . better
D . the best
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____ no air or water, there would be no life in the world.
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原文:物体在水中比在空气中轻,这是一个大家共有经验。译文:It is a of common experience that are in water than they are in air.
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Choose a correct sound for the underlined letters in the following sentence.The winter wind will bring a big chill.
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In what way is culture like the water a fish swims in?
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原文:物体在水中比在空气中轻,这是一个大家共有经验。译文:It is a of common experience that are in water than they are in air.第一空：matter；第二空： bodies；第三空： lighter
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When the air in a certain space is squeezed to occupy a smaller space, the air is said to be ______.
A．commenced
B．compressed
C．compromised
D．compensated
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In international air cargo transportation， a freightforwarder offering a consolidation service will issue its own air waybill.Thisis called（）.
A．MAWB
B．HAWB
C．IATA
D．TACT
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They made a fire in the open air and cooked a meal over it. ______ was made in the open air and a meal ______ over it.
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I have certainly seen lots of changes in my lifetime! I look around my home and see "mod cons" that I could never have dreamed of 50 or 60 years ago. I spent the early part of childhood in a cottage without running water or electricity and yet these days, I feel paralyzed if there is a power cut for even just an hour or two! So, I have changed too. Things that I couldn't even imagine in the past now seem quite normal.
Businessmen can travel from London to New York in three hours and lots of people exceed the seventy-mile-per-hour speed limit on motorways. A person of 75 is not old these days. A serious illness does not mean certain death because there have been so many advances in medical science. We no longer need to be afraid of contracting diseases like polio or smallpox. I can speak to my son in Australia from my own sitting room here in Manchester, watch athletes running a race on the other side of the world without moving from my own home and I can even do my shopping while I sit here in an armchair. I never need to worry about food going bad in the warm weather and, at the flick of a switch, I can have a hot meal in a couple of minutes. So, it seems, the quality of life has greatly improved since my own childhood.
I'm not convinced, however, that people are happier today than they were 50 years ago. We are certainly materially better off than we were but most people still seem to be weighed down by problems. My daughter and her family are a good illustration. They have a spacious, comfortable home with every labor-saving device you can think of. There's a washing machine, a clothes dryer, a food processor, a vacuum cleaner and all sorts of other household items which are designed to save time but it seems to me that my daughter and her husband just spend all that "saved" time working! They never relax and are always complaining of being tired and "stressed".
What is the passage mainly about？
A．How life has improved.
B．How life has become worse.
C．A comparison of life now and that in the past.
D．Memory of life in the past.
