Engineering :: Thermodynamics

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151.

By doubling the temperature the radiant heat will increase

A.	2 times	B.	4 times
C.	8 times	D.	16 times

152.

The heat flows through solids only by

A.	Conduction	B.	Convection
C.	Radiation

153.

Highly polished surfaces of a thermosflask prevent heat by

A.	Conduction	B.	Convection
C.	Radiation

154.

If the roof of a house is replaced by a shiny metallic surface the temperature inside will

A.	Increase	B.	Remain unaltered
C.	Decrease

155.

The concept of black body in heat transfers applies to

A.	Objects which are black in colour	B.	Objects which are good conductors of heat
C.	Objects that completely absorb impinging radiation	D.	Objects well insulated from surroundings

156.

The rate of diffusion along a column of certain cross-sectional area is proportional to the concentration gradient. Above statement is known as

A.	Thompson's law	B.	Law of diffusion
C.	Kirchhoff's law	D.	Fick's law
E.	None of the above

157.

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

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

158.

Non-dimensional numbers generally involved in case of heat transfer from horizontal cylinders by natural convection are

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

159.

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.	1600

160.

In case of a four cylinder diesel engine, the heat carried away by exhaust gases will be

A.	5 to 7 percent	B.	7 to 10 percent
C.	10 to 20 percent	D.	25 to 35 percent
E.	50 to 70 percent