As part of a final year undergraduate project, I was a part of a team of 4 students employed by Albaj Engineering Co-op PVT LTD, to design and manufacture and air cooled heat exchanger.
An Air Cooled Heat Exchanger (ACHE) is a device for rejecting heat from a fluid directly to ambient air. This is in contrast to rejecting heat to water and then rejecting it to air, as with a shell and tube heat exchanger and a wet cooling tower system. The main advantage of an ACHE is that it does not require water, which means that plants requiring large cooling capacities need not be located near a supply of cooling water.
Air-cooled heat exchangers (ACHEs) enhance heat transfer through fins. They are extensively used to remove heat from process fluids (liquid or gas) by transferring it (heat) to atmosphere. The process includes conduction from the fluid through the tube to the fin and convection from the fin to atmosphere.

We were involved in all the various stages, right from the thermal calculations, verification by HTRI software, to the manufacture and final testing and inspection.