HEAT TRANSFER QUIZ

Harmonic mean temperature difference is given by

(ΔT₁ - ΔT₂)/(ΔT₁ . ΔT₂)

2.(ΔT₁ . ΔT₂)/(ΔT₁ + ΔT₂)

2.(ΔT₁ . ΔT₂)(ΔT₁ - ΔT₂)

√(ΔT₁ . ΔT₂)

TRUE ANSWER : ?
YOUR ANSWER : ?

The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by

Natural convection

Steady state conduction

Transient conduction

Forced convection

TRUE ANSWER : ?
YOUR ANSWER : ?

With increase in porosity, the thermal conductivity of a solid substance

Decreases

Increases

May increase or decrease; depends on the solid

Remains unchanged

TRUE ANSWER : ?
YOUR ANSWER : ?

Kirchoff's law is applicable to

Only volumes and not to surfaces

Monochromatic radiation only

Both A and B

Total radiation only

TRUE ANSWER : ?
YOUR ANSWER : ?

A diathermaneous substance __________ the thermal radiation completely.

Absorbs

Transmits

None of these

Reflects

TRUE ANSWER : ?
YOUR ANSWER : ?

A hot body will radiate heat most rapidly, if its surface is

White & rough

Black & polished

White & polished

Black & rough

TRUE ANSWER : ?
YOUR ANSWER : ?

The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation.

Greater than

Is same as

Lower than

Half

TRUE ANSWER : ?
YOUR ANSWER : ?

The energy radiated from a surface Q at absolute temperature T is related as

None of these

Q ∝ T³

Q ∝ T⁴

Q ∝ T²

TRUE ANSWER : ?
YOUR ANSWER : ?

In a heat exchanger, one transfer unit means

Both A and B

None of these

A section of the exchanger in which change in temperature of one stream equals the average driving force in the section

The size of the exchanger in which heat transfer rate is 1 kcal/hr

TRUE ANSWER : ?
YOUR ANSWER : ?

Nusselt number is the ratio of the temperature gradient at the wall to

None of these

Heat flux

Temperature difference

That across the entire pipe

TRUE ANSWER : ?
YOUR ANSWER : ?