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Mechanical Engineering Objective Questions { Heat Transfer }



29. Moisture would find its way into insulation by vapor pressure unless it is prevented by
A.High thickness of insulation
B.High vapour pressure
C.Less thermal conductivity insulator
D.A vapor seal

30. LMTD in case of counter flow heat exchanger as compared to parallel flow heat exchanger is
A.Higher
B.Lower
C.Same
D.Depends on the area of heat exchanger

31. The amount of radiation mainly depends on
A.Nature of body
B.Temperature of body
C.Type of surface of body
D.All of the above

32. Absorptivity of a body will be equal to its emissivity
A.At all temperatures
B.At one particular temperature
C.When system is under thermal equilibrium
D.At critical temperature

33. Cork is a good insulator because it has
A.Free electrons
B.Atoms colliding frequency
C.Low density
D.All of the above

34. The rate of energy emission from unit surface. area through unit solid angle, along a normal to the surface, is known as
A.Emissivity
B.Transmissivity
C.Reflectivity
D.Intensity of radiation

35. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as
A.Krichoff's law
B.Stefan's law
C.Wien' law
D.Planck's law

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