ABSTRACT
This chapter describes quantitative methods to define the performance benefits of enhanced heat transfer surfaces in a heat exchanger, for which at least one of the fluids is evaporating or condensing. Pressure drop of a two-phase fluid may reduce the mean temperature difference for heat exchange. This situation does not exist for heat exchange between single-phase fluids. This chapter shows how the performance evaluation criteria (PEC) previously defined for single-phase flow may be modified to account for the effect of pressure drop. Generalized PEC are defined for three basic applications of two-phase heat exchangers, and two examples of PEC analysis are presented. The PEC analysis for two-phase heat transfer was originally formulated by Webb [1988] and is the only PEC analysis advanced to date for two-phase heat transfer.
