Compact Heat Exchangers

Double-pipe heat exchangers, shell-and-tube heat exchangers, and plate heat exchangers may have either parallel flow or counterflow arrangement. Finned-tube heat exchangers are gas-to-liquid heat exchangers and have dense fins attached on the tubes of the air side, because the heat transfer coefficient on the air side is generally one order of magnitude less than that on the liquidside. Plate-fin heat exchangers, are the most compact heat exchangers, commonly having triangular or rectangular cross sections. Printed-circuit heat exchangers were developed for corrosive and reactive chemical processes, which do not tolerate dissimilar materials in fabrication. Polymer compact heat exchangers also provide resistance to fouling. The louver-fin geometry provides heat transfer coefficients comparable to those of the offset-strip-fin geometry. In the last decades the importance of heat recovery in both civil and industrial applications is continuously growing. The chapter considers a typical plate finned heat pipe heat exchanger for recovering waste heat in a ventilation system.