Fin efficiency and mechanisms of heat exchange through fins in multi-stream plate-fin heat exchangers: development and application of a rating algorithm

Abstract

The basic heat balance equations for separating surface and passage in a multi-stream plate-fin heat exchanger are derived based on a formalism proposed earlier [Prasad, International Journal of Heat and Mass Transfer 1996, 39(2), 419–428]. An algorithm is developed for rating heat exchangers based on the equations, and incorporated into an existing computer code called STACK [Prasad, Heat Transfer Engineering, 1991, 12(4), 58–70]. The program is used to analyse some typical heat exchangers. It was found that though transverse conduction could be present in some and absent in some passages, it tended to play an increasingly important role as fin effectiveness increased. Of the three mechanisms of heat exchange identified, Mechanism 1 and Mechanism 3 dominated at low fin effectiveness, whereas Mechanism 2 tended to dominate at high fin effectiveness. It was found that the developed method reliably predicted heat transfer in special situations such as the presence of dummy passages, where other methods were known to fail.