HEAT TRANSFER QUIZ

Harmonic mean temperature difference is given by

2.(ΔT₁ . ΔT₂)/(ΔT₁ + ΔT₂)

2.(ΔT₁ . ΔT₂)(ΔT₁ - ΔT₂)

(ΔT₁ - ΔT₂)/(ΔT₁ . ΔT₂)

√(ΔT₁ . ΔT₂)

TRUE ANSWER : ?
YOUR ANSWER : ?

Heat transfer rate per unit area is called

thermal diffusivity

thermal conductivity

heat flux

heat transfer co-efficient

TRUE ANSWER : ?
YOUR ANSWER : ?

Which of the following is unimportant in forced convection ?

none of the listed here

Reynolds number

Grashhoff number

Prandtl number

TRUE ANSWER : ?
YOUR ANSWER : ?

All analogy equations connecting friction factor and heat transfer co-efficient apply only to

Turbulent flow

Form friction

Wall or skin friction

Both A and B

TRUE ANSWER : ?
YOUR ANSWER : ?

The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoffs law.

Wavelength of radiation

None of these

Temperature of the body

Nature of the body

TRUE ANSWER : ?
YOUR ANSWER : ?

'Duhring's plot' is of use in

Absorption

Extractive distillation

Evaporation

Leaching

TRUE ANSWER : ?
YOUR ANSWER : ?

A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.

5 minutes

10 minutes

20 minutes

40 minutes

TRUE ANSWER : ?
YOUR ANSWER : ?

The units of resistance to heat transfer is

W⁻¹m²K

J.m⁻².K⁻¹

W.m⁻².K⁻¹

J.m⁻¹.K⁻¹

TRUE ANSWER : ?
YOUR ANSWER : ?

When vaporisation takes place directly at the heating surface, it is called

nucleate boiling

all of the listed here

vapour binding

film boiling

TRUE ANSWER : ?
YOUR ANSWER : ?

Kirchoff's law is applicable to

Monochromatic radiation only

Total radiation only

Only volumes and not to surfaces

Both A and B

TRUE ANSWER : ?
YOUR ANSWER : ?

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