Engineering :: Heat Transfer

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51.

A substance above critical temperature exists as

A.	Solid	B.	Liquid
C.	Dry vapour	D.	Wet vapour
E.	Gas

52.

There are two spheres of copper the ratio of their radii being 1 : 3 both at the same temperature. The ration of heat contents will be

A.	1 ; 1	B.	1 ; 3
C.	1 ; 9	D.	1 ; 27
E.	1 ; 81

53.

When analogy is drawn between heat flow and electricity flow in circuits, the heat flow of thermal circuits is equated in the electrical circuit against

A.	Voltage	B.	Current
C.	Resistance	D.	Charge (coulombs)

54.

Thermal diffusivity is least for

A.	Rubber	B.	Lead
C.	Aluminium	D.	Iron
E.	Mercury

55.

The lower temperature limit for mercury thermometer is

A.	0?C	B.	0?F
C.	? 39?F	D.	100?C
E.	Absolute zero

56.

For temperature below -40?C which one of the following substance can be used as thermometric substance

A.	Alcohol	B.	Pentane
C.	Ether	D.	Any of the above
E.	None of the above

57.

Heat is transferred from an insulated pipe to the surrounding still air mainly by

A.	Conduction	B.	Free convection
C.	Forced convection	D.	Radiation
E.	All above together

58.

Non-dimensional number generally involved in case of heat transfer from horizontal cylinder by natural convection is

A.	Reynolds number	B.	Nusselt number
C.	Prandtl number	D.	Grashof's numbr
E.	(B), (C) and (D) above

59.

Transformer oil having kinematic viscosity of 3.66 x 10-6 m2/s flows through a tube 8 mm diameter at velocity of 0.6 m/s. The value of Reynolds number of flow would be

A.	1000	B.	1310
C.	1415	D.	1510
E.	1625

60.

The nature of flow of a fluid inside a tube i.e., whether it is turbulent or laminar, is ascertained by

A.	Flow velocity	B.	Tube size
C.	Surface conditions	D.	Viscosity of fluid
E.	Reynolds number