67) Thermal diffusivity of a substance is

directly proportional to the thermal conductivity

inversely proportional to density of substance

inversely proportional to specific heat

all of the above

Answer is:

all of the above

Explanation:

Thermal diffusivity of a substance is
* directly proportional to the thermal conductivity
* inversely proportional to density of substance
* inversely proportional to specific heat

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68) Fouling factor is used

in heat exchanger design as a safety factor

in case of Newtonian fluids

when a liquid exchanges heat with a gas

none of the above

Answer is:

in heat exchanger design as a safety factor

69) The natural convection air cooled condensers are used in

domestic refrigerators

water coolers

room air conditioners

all of these

Answer is:

domestic refrigerators

70) The process, generally used in winter air-conditioning to warm and humidity the air, is called

humidification

dehumidification

heating and humidification

cooling and dehumidification

Answer is:

heating and humidification

71) At 100% relative humidity, wet bulb temperature, dry bulb temperature, dew point temperature and saturation temperature are equal.

Correct

Incorrect

Answer is:

Correct

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