Q. The space between the two walls of a thermos flask is evacuated because vacuum is a __________ conductor of heat.

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Q. The ratio of actual heat transfer to the maximum possible heat transfer is known as heat exchanger effectiveness.

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Q. The mass of water vapour present in 1 kg of dry air, is called humidity ratio.

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Q. In a vapour compression refrigeration system, a throttle valve is used in place of an expander because

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Q. The unit of overall coefficient of heat transfer is

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Q. Most thermostatic expansion valves are set for a superheat of

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Q. For large tonnage (more than 200 TR) air-conditioning applications, the compressor recommended is

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Q. Air refrigerator works on

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Q. The reciprocating refrigerant compressors are very suitable for

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Q. The boiling point of carbon dioxide is

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Q. The mass of water vapour present in __________ is called absolute humidity.

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Q. The relative coefficient of performance is equal to

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Q. The final relative humidity of the air during cooling and dehumidification is generally __________ than that of entering air.

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Q. The emissivity of a polished silver body is __________ as compared to black body.

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Q. In a pressure enthalpy chart, the space between the saturated liquid line and saturated vapour line, represents sub-cooled liquid region.

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Q. R-11 has the highest critical point temperature.

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Q. The ratio of heat extracted in the refrigerator to the workdone on the refrigerant is called

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Q. The boiling point of ammonia is

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Q. The by-pass factor (B. P. F.) in case of sensible heating of air is (Where td1 = Dry bulb temperature of air entering the heating coil, td2 = Dry bulb temperature of air leaving the heating coil, and td3 = Dry bulb temperature of heating coil)

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Q. The refrigerant used for absorption refrigerators working on heat from solar collectors is a mixture of water and

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