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The receiver used in a refrigeration system（）
A . stores liquid refrigerant
B . collects non-condensable gases
C . allows refrigerant sub-cooling
D . prevents compressor surging
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When fruit is carried as refrigerated cargo，the most frequent cause of its being infected at the discharge port is（）.
A . leaks in the ship's refrigeration system
B . improper cleaning of the cargo spaces
C . carriage at the wrong temperature
D . improper precooling of the cargo space
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In the refrigeration system, a shortage of refrigerant is indicated by （）.
A . the compressor short cycling on high pressure cut out switch
B . high suction pressure
C . high head pressure
D . bubbles in the sight gla
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A refrigerant with oil in solution has a （）.
A . higher boiling temperature for a given pressure than does a pure refrigerant
B . lower boiling temperature for a given pressure than does a pure refrigerant
C . boiling pressure equal to that of a pure refrigerant at a given pressure
D . boiling point will not be affected by entrained oil
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Before charging a refrigeration unit, the refrigerant charging lines should be（）
A . flushed with clean refrigerant oil
B . purged with the refrigerant
C . washed with an ammonia and alcohol solution
D . grounded to compressor
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In a refrigeration system, the refrigerant absorbs the latent heat of vaporization in the（）.
A . compressor
B . condenser
C . receiver
D . evaporator
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A refrigerant gives up heat when it goes through （）.
A . condenser
B . regurgitate
C . evaporator
D . boil coil
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Insufficient refrigerant in a refrigeration plant may result in （）.
A . high discharge pressure
B . frosting of the crankcase
C . high temperature of the overboard water
D . low suction pressure of compressor
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Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?（）
A . Sub-cooled liquid
B . Sub-cooled vapor
C . Superheated vapor
D . Liquid
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Ammonia when used as a refrigerant is valuable because of its high efficiency, it is however （）.
A . toxic
B . flammable
C . explosive
D . all of the above
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The component of a refrigerating system in which the refrigerant vaporizes and absorbs heat is known as the （）.
A . condenser
B . vapor generator
C . accumulator
D . evaporator
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When liquid reaches the compressor of a refrigeration system through the suction line, the condition is called （）.
A . flooding back
B . superheating
C . overflowing
D . recycling
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In a compression refrigeration cycle, the temperature of the liquid refrigerant experiences its greatest decrease in the（）.
A . evaporator
B . compressor
C . expansion valve
D . condenser
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A refrigeration unit will tend to short cycle when operating （）.
A . under heavy loads
B . during hot gas defrost
C . under light loads
D . during starting conditio
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When the relief valve opens it discharges high pressure refrigerant vapor to the （）.
A . liquid strainer
B . refrigerant inlet of the condenser
C . inlet side of the evaporator
D . suction side of the compressor
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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
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In an operating refrigeration system low on refrigerant, a liquid line sight glass will（）
A . be clear
B . be blue
C . be light green
D . show bubble
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The function of （） in a refrigeration plant using Freon is to move moisture from all refrigeration system.
A . filter
B . filter drier
C . heat exchanger
D . air cooler
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When a refrigeration compressor is in the ‘off’ cycle, the thermal expansion valve will（）.
A . always be wide open when the compressor restarts
B . continue to operate as if the system were in operation
C . remain open until evaporator pressure equalizes, then close until the compressor restarts
D . always be completely closed until the compressor restart
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When the temperature of the refrigerant flowing out from the condenser is below the condensing temperature, it is said to be （）.
A . dry
B . wet
C . super-cooled
D . superheated
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Refrigerant enters the condenser as a （）.
A . high pressure liquid
B . low pressure vapor
C . high pressure vapor
D . low pressure liquid
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The fridge is considered necessary. It has been so since the 1960s when packaged food list appeared with the label: "Store in the refrigerator."
In my fridgeless fifties childhood, 1 was fed well and healthy. The milkman came every day, the grocer, the butcher (肉商), the baker, and the ice-cream man delivered two or three times each week. The Sunday meat would last until Wednesday and surplus(剩余) bread and milk became all kinds of cakes. Nothing was wasted, and we were never troubled by rotten food. Thirty years on food deliveries have ceased, fresh vegetables are almost unobtainable in the country.
The invention of the fridge contributed comparatively little to the art of food preservation. Many well-tried techniques already existed -- natural cooling, drying, smoking, salting, sugaring, bottling...
What refrigeration did promote was marketing --- marketing hardware and electricity, marketing soft drinks, marketing dead bodies of animals around the world in search of a good price.
So most of the world's fridges are to be found, not in the tropics where they might prove useful, but in the rich countries with mild temperatures where they are climatically almost unnecessary. Every winter, millions of fridges hum away continuously, and at vast expense, busily maintaining an artificially-cooled space inside an artificially-heated house -- while outside, nature provides the desired temperature free of charge.
The fridge's effect upon the environment has been evident, while its contribution to human happiness has been not important. If you don't believe me, try it yourself, invest in a food cabinet and mm off your fridge next winter. You may not eat the hamburgers, but at least you'll get rid of that terrible hum.
The statement "In my fridgeless fifties childhood, I was fed well and healthily." suggests that
A．the author was well-fed and healthy even without a fridge in his fifties.
B．the author was not accustomed to fridges even in his fifties.
C．there was no fridge in the author's home in the 1950s.
D．the fridge was in its early stage of development in the 1950s.
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When a refrigeration compressor is in the ‘off’ cycle, the thermal expansion valve will .
A.always be wide open when the compressor restarts
B.continue to operate as if the system were in operation
C.remain open until evaporator pressure equalizes, then close until the compressor restarts
D.always be completely closed until the compressor restarts
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Excessive circulation of the lubricating oil with the refrigerant in a refrigeration system will cause______.
A.carbon deposits on the compressor suction valves
B.the evaporator temperature to increase
C.rapid corrosion of the thermal expansion valve
D.no operating problems
