Heat Transfer MCQs

The sum of reflectivity and absorptivity for an opaque body is equal to

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

Prandtl number for most of dry gases is about

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

Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator?

Fouling factor

In SI units, fouling factor is expressed in

Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.

In a laboratory test run, the rate of drying was found to be 0.5 × 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is