About fins

No replies here ?

Fins are indeed extended surfaces for heat transfer. Not necessarily on engines or compressors or other equipment that require cooling. In many applications they are used to heat gases. Also the principle is not just Newton's law of radiation.
All gases have very poor thermal conductivities. In any heat transfer what are called film coefficients control the heat transfer. The reciprocal of the overall heat transfer coefficient is the sum of the reciprocals of individual coefficients, which means that the overall coefficient will be more like the minimum coefficient. One way to get round the problem is to have a much larger surface area on the side with the least coefficient. Hence fins. Since the contact coefficients are high there is no need to have integral fins. In the industry quite often the fins are crimped on or brazed on. Since the coefficient of conduction in metal is hundreds of times more than that on the gas film side any metal compatible with the gas can be used. The great advantage of this is that the fins can be of a much cheaper metal than the tube carrying the fluid.

thank you sir, now i know what i needed to know.