Heat and Mass Transfer MCQs

Thermal conductivity of air at room temperature in kcal/m hr °C is of the order of

According to Stefan's law, the total radiation from a black body per second per unit area is proportional to

The critical temperature is the temperature

Thermal conductivity of non-metallic amorphous solids with decrease in temperature

Thermal conductivity of air with rise in temperature

Thermal conductivity of water in general with rise in temperature

Heat is closely related with

The thermal diffusivities for gases are generally

Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be