On the weak coupling between geometry and heat transfer in heat exchanger optimization

Abstract

Several case studies have shown that the overall heat transfer coefficient is weakly coupled to the geometric dimensions of the shell and tube heat exchanger in the near optimal region. The criteria for weak coupling have been investigated by establishing the dependence of objective function, geometry and heat transfer coefficient on the major exchanger parameters. Further, these criteria have been shown to hold good when the influence of baffle spacing on the objective function is negligible. This provides us with a heuristic to simplify the problem of optimal synthesis of shell and tube heat exchangers which has been illustrated by an example. The existence of weak coupling between geometry and heat transfer aspects allows us to synthesize the exchanger without using any approximations and to obtain a near optimum in about four iterations. Also, the problem can now be handled on a personal computer whereas previously sophisticated nonlinear optimization codes were used for this task requiring large computers.