If a heat transfer surface is pock-marked with a number of cavities, then as compared to a smooth surface the heat transfer by __________ will not increase.

Answer: Option C

Radiation: The heat transfer by radiation is independent of surface texture (like cavities or pock-marks) and relies on the emissivity and temperature of the surface. Hence, the heat transfer by radiation does not increase due to the presence of cavities.

Convection: Cavities on a heat transfer surface can enhance convection by disturbing the boundary layer, promoting turbulence and fluid mixing. This increases the rate of convective heat transfer.

Nucleate Boiling: Cavities act as nucleation sites, facilitating bubble formation and improving heat transfer during boiling.

Conduction: Surface irregularities could affect conduction slightly but are less significant in comparison to the other modes of heat transfer. Thus, Option C: Radiation is the correct answer because it remains unaffected, while other modes of heat transfer may increase with a pock-marked surface.