MP Sub-Engineer ME: Unsteady State Heat Conduction & Fins Quiz 57

Thermal diffusivity is

Choose the correct statements:

a. Thermal diffusivity is directly proportional to thermal conductivity.

b. Thermal diffusivity is inversely proportional to density of substance.

c. Thermal diffusivity is inversely proportional to specific heat.

Which of the following parameter has the unit m²/s ?

The time constant of a thermocouple is ________.

Find the time required for a lumped system to reach the average temperature of initial temperature T_o of an object and surrounding temperature T_∞. Where  is thermal time constant.

Extended surfaces are used to increase the rate of heat transfer. When the convective heat transfer h =, where , the addition of extended surface will

Consider the following statements pertaining to large heat transfer rate using fins

(i) Fins should be used on the side where heat transfer coefficient is small.

(ii) Long and thick fins should be used

(iii) Thin fins should be used.

(iv) Thermal conductivity of fin material should be large.

Which of the following statements are correct?

Biot number signifies

Boundary condition for infinity long fins is

Where

T_o = base temp.

T_∞ = environment temp