Optimal Heat Exchangers

The design of optimal heat exchangers is formulated as the solution of five simultaneous equations. The analysis of these equations yields general properties of optimal crossflow heat exchangers; in particular, an upper bound of 1/3 is given for the fractional cost of maintaining the flow through the heat exchanger. Some of these general properties also apply in the presence of a simple constraint. It is shown that some technically feasible designs cannot be optimal under realistic costs and others under any costs.