Fins improve heat transfer in two ways. One way is by creating turbulent flow through fin geometry, which reduces the thermal resistance (the inverse of the heat transfer coefficient) through the nearly stagnant film that forms when a fluid flows parallel to a solid surface. A second way is by increasing the fin density, which increases the heat transfer area that comes in contact with the fluid. Fin geometries and densities that create turbulent flow and improve performance also increase pressure drop, which is a critical requirement in most high performance applications. The optimum fin geometry and fin density combination is then a compromise of performance, pressure drop, weight, and size. A figure-of-merit comparison based on performance, pressure drop, weight, and size among common fin types is described in “Air Cooled Compact Heat Exchanger Design for Electronics Cooling.” Aside from fin geometry, parameters such as thickness, height, pitch, and spacing can also be altered to improve performance. Typically, fin thicknesses vary from 0.004 in (0.1 mm) to 0.012 in (0.3 mm), heights vary from 0.035 in (0.89 mm) to 0.6 in (15.24 mm), and densities vary from 8 to 30 FPI (Fins per Inch).

The problem for IC is a bit more complex as for electronics - in a way -.

Your design has to consider first of all which manufacturing technology will be used for the cylinder. Will you use a cover to direct the air flow ? Is it a forced or natural convection you intend to use ? Those are the first question you have to give an answer.

Qualitatively speaking the distance between two fins depend on the air flow velocity and the pressure drop you can afford. If the fins are to near to each other and velocity too small boundary layers will be too thick and heat transfer not very efficient. Thickness of fins will depend on manufacturing approach as well their height. It is an optimal ratio depending on the conductivity of the fin and convection coefficients.

You mention temperatures in your explanation but this is not enough you should also look at how much heat you want to transfer this will give you the transfer surfaces you will need.

It was mentioned "turbulence", if for instance the fins are too long the boundary layer can grow and reduce average heat transfer intensity. S that it is better for instance to have shorter fins (in flow direction) and if possible not in same plane in order to increase turbulence.

I think you should of course look at the recommended source but also look in a general heat transfer book to have a better feeling about. The problem of fins is in almost books very well explained. And last but not least have a look at motorbike engines it will give you an idea about many aspects you should take care of.

Dear Pankaj,

These articles may help you.

Dear sir

You should first searching papers with Nusselt number difention for fin heat transfer and calculation of Nusselt number. After it you can easily calculated it.