Heat Transfer, Refrigeration and Air Conditioning – Section 2

21. Free convection flow depends on

A. density
B. coefficient of viscosity
C. gravitational force
D. all of these

Correct Answer: D. all of these

22. The critical pressure of a liquid is the pressure

A. above which a liquid will remain a liquid
B. above which a liquid will explode
C. above which a liquid will always convert into a vapor
D. below which a liquid will always be in vapor form

Correct Answer: A. above which a liquid will remain a liquid

23. Conduction is a process of heat transfer

A. from one particle of the body to another without the actual motion of the particles
B. from one particle of the body to another by the actual motion of the heated particles.
C. from a hot body to a cold body, in a straight line, without affecting the intervening medium
D. none of the above

Correct Answer: A. from one particle of the body to another without the actual motion of the particles

24. Thermal diffusivity of a substance is

A. directly proportional to the thermal conductivity
B. inversely proportional to density of substance
C. inversely proportional to specific heat
D. all of the above

Correct Answer: D. all of the above

25. The sensible heat factor during the heating and humidification process is given by (where h1 = Enthalpy of air entering the heating coil, h2 = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)

ht-se2-25

Correct Answer: Option D

26. Fouling factor is used

A. in heat exchanger design as a safety factor
B. in case of Newtonian fluids
C. when a liquid exchanges heat with a gas
D. none of the above

Correct Answer: A. in heat exchanger design as a safety factor

27. The natural convection air cooled condensers are used in

A. domestic refrigerators
B. water coolers
C. room air conditioners
D. all of these

Correct Answer: A. domestic refrigerators

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

A. humidification.
B. dehumidification
C. heating and humidification
D. cooling and dehumidification

Correct Answer: C. heating and humidification

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

A. Correct
B. Incorrect

Correct Answer: A. Correct

30. Bell-Coleman cycle is a

A. reversed Carnot cycle
B. reversed Otto cycle
C. reversed Joule cycle
D. reversed Rankine cycle

Correct Answer: C. reversed Joule cycle

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