This edition does not differ radically from its predecessor but it does contain the basic test data for 11 new surface configurations, including some of the very compact ceramic matrices. In addition to modernization of the theoretical solutions and correlations for simple geometries, and the transient solutions, a number of other improvements will be found. Finally, the slow conversion (at least in the United States) to the Systeme Internationale (SI) system of units suggested that the time had come to make that conversion in Compact Heat Exchangers. Since the English system is apparently destined to disappear only slowly in the United States, it was decided to introduce a dual system of units in the new edition. So all dimensions are given in both systems, and the fluid properties in the Appendix are likewise presented in both systems.A unique feature of Compact Heat Exchangers has always been that virtually all of the basic test data originate from a single research program under the supervision of the authors. There is thus no question about the comparability of the test results of one surface to another.