Chemical Heat Transfer Quiz 10

1 / 26

Which of the following has the minimum absorptivity ?

Coal dust

Iron plates

Aluminium foil

Refractory bricks

2 / 26

Which of the following has the minimum thermal conductivity ?

Tar

Steel

Carbon black

Nitrogen

3 / 26

With increase in temperature, the thermal conductivity of fresh lubricating oil _____?

Decreases

Increases

Remains unchanged

May increase or decrease; depends on its composition

4 / 26

With increase in temperature, the thermal conductivity of non-metallic amorphous solids__________?

Increases

Decreases

Remain constant

First decreases upto certain temperature and then increases

5 / 26

With the increase of temperature, the Col-burn jH factor_______?

Remains unchanged

May increase or decrease; depending on temperature

Increases

Decreases

6 / 26

Which of the following situations can be approximated to a steady state heat transfer system ?

Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180?C

A red hot steel slab (having outside surface temperature as 1300?C) exposed to the atmospheric air at 35?C

10 kg of dry saturated steam at 8 kgf/cm2 flowing through a short length of stainless steel pipe exposed to atmospheric air at 35?C

A sub-cooled refrigerant liquid at 8?C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35?C

7 / 26

Which type of heat exchanger is preferred for heavy heat loads ?

Double pipe

Series and parallel set of shell and tube

None of these

Plate fine

8 / 26

Which one gives the monochromatic emissive power for black body radiation ?

Kirchhoff?s law

Wien?s law

Stefan-Boltzmann law

Planck?s law

9 / 26

Which of the following is the most widely used heat insulating material for pipelines carrying steam ?

Tar dolomite bricks followed by asbestos

Fireclay refractory followed by aluminium sheet

85% magnesia cement and glass wool

Cotton followed by aluminium foil

10 / 26

Which of the following is correct ?

Rate = Resistance/Driving force

Rate = Driving force ? Resistance

Driving force = Rate ? Resistance

Resistance = Driving force ? Rate

11 / 26

Which of the following is not used as a medium for high temperature heating ?

Dowtherm

Liquid metal (e.g. molten sodium)

Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)

Mercury

12 / 26

Which of the following is directly concerned with the heat transfer ?

Euler number

Grashoff number

Strouhal number

Sherwood number

13 / 26

With increase in temperature, the total emissivity of conductors______?

Remain same

Decreases linearly

Decreases

Increases

14 / 26

Which of the following has the highest thermal conductivity ?

Silver

Air

Water

Brick

15 / 26

With increase in temperature, the thermal conductivity of most liquids__________?

First increases upto a certain temperature and then becomes constant

Increases

Remain same

Decreases

16 / 26

Which of the following is unimportant in forced convection ?

Prandtl number

Grashoff number

None of these

Reynolds number

17 / 26

With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer ?

Increases

Decreases

Increases exponentially

Remain unaffected

18 / 26

Which of the following is generally considered as opaque surface towards radiations ?

Both B. and C.

Solids

Gases

Liquids

19 / 26

Which of the following has the lowest overall heat transfer co-efficient ?

Molten sodium

Water

Dowtherm

Air

20 / 26

With increase in temperature, the thermal conductivity of a gas _____?

Decreases

May increase or decrease depending on the type of gas

Increases

Remain same

21 / 26

Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger ?

Convective heat transfer co-efficient

All A. B. and C.

Effective tube surface area for convective heat transfer

Tube side pressure drop and the heat transfer rate

22 / 26

While the total emissivity of a perfect black body is unity, the same for a real body is___________?

Between 0 and 1

> 1

23 / 26

With increase in porosity, the thermal conductivity of a solid substance___________?

Decreases

May increase or decrease; depends on the solid

Remains unchanged

Increases

24 / 26

Which of the following is concerned with both heat and mass transfer ?

Kutateladze number

Froude number

Lewis relationship

Nusselt number

25 / 26

Which of the following parameters of the fluid is not very important, while deciding its route in a shell and tube heat exchanger ?

Viscosity

Density

Corrosiveness & fouling characteristics

Pressure

26 / 26

Which of the following has the lowest Prandtl number ?

Transformer oil

Water

Dilute H2SO4

Molten sodium (a coolant used in fast breeder reactor)

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