Question

Heat transfer by molecular collision in ____________________

(a) Conduction

(b) Convection

(c) Scattering

(d) Radiation

This question was addressed to me by my school principal while I was bunking the class.

The question is from Convective Mass Transfer topic in division Mass Transfer of Bioprocess Engineering

Answer 1

Right choice is (b) Convection

To explain I would say: Flow of heat through currents within a fluid (liquid or gas). Convection is the displacement of volumes of a substance in a liquid or gaseous phase. When a mass of a fluid is heated up, for example when it is in contact with a warmer surface, its molecules are carried away and scattered causing that the mass of that fluid becomes less dense. For this reason, the warmed mass will be displaced vertically and/or horizontally, while the colder and denser mass of fluid goes down (the low-kinetic-energy molecules displace the molecules in high-kinetic-energy states). Through this process, the molecules of the hot fluid transfer heat continuously toward the volumes of the colder fluid.