Four-Port Representations of Heat Exchangers

Abstract

Two-port models represent a subsystem as a black box with an input and an output port. They are very convenient mathematical representations of subsystems, allowing easy connection between subsystem models to form a larger model. From an educational point of view, two-ports emphasize the idea of a subsystem as part of a larger structure. In this paper the concept is applied to two-stream heat exchangers, which are represented by a four-port model: two input ports and two output ports. It provides a new method of heat exchanger analysis which is complementary to the usual LMTD and effectiveness methods. It is easy to comprehend and ideal for computer programming. Large networks of heat exchangers are easily solved. In addition, it allows approximate models for heat exchangers with nonconstant properties as a cascade of constant property elements.