Compact New Formulae for Mean Temperature Difference and Efficiency of Heat Exchangers

Summary

Recently a system of very compact formulae for the well known efficiency — NTU relationships for heat exchangers of various flow configurations has been presented by the author[1, 2]. The advantages of these new formulae in the calculations required in thermal design of heat exchangers will be demonstrated for a number of flow configurations. Shell-and-tube exchangers with multiple passes, with split flow and two tube passes, as well as a number of cross-counterflow configurations will be shown to be treated very much easier using the new formulae. In combination with the cell-method, as developed by Gaddis and Schlünder, the new formulae may be used as efficient engineering tools in computer programs. The application of now widely available software, such as a spreadsheet calculation program for easy execution of heat exchanger design calculations with the cell method will also be demonstrated in this context.