EFFECTIVENESS NUMBER OF TRANSFER UNITS RELATIONSHIPS FOR HEAT-EXCHANGER COMPLEX FLOW ARRANGEMENTS

Heat exchanger performance (or terminal temperatures), size and fluid flow rates are related in a dimensionless form in terms of the exchanger effectiveness, number of transfer units and heat capacity rate ratio. Such relationships are essential for design and analysis of any heat exchangers. Over the last 100 years, many heat exchanger flow arrangements have been analyzed and reported in the literature. However, since 1969, several very powerful methods have been developed to analyze complicated flow arrangements for two-fluid recuperators. These are matrix formalism, chain rule, and rules for exchangers with one fluid mixed, among others. These methods are briefly summarized in the paper with illustrative examples. Using these methods, 18 new recuperator flow arrangements have been analyzed and the results are presented in closed-form formulas assuming constant overall heat transfer coefficient and fluid properties. The results summarized here together with those published in the open literature should then provide the reader with an idea as to where to concentrate future research efforts on the subject.