Compact Heat Exchangers

4Finite Element Analysis of Compact Heat Exchangers

4.1 Introduction

Many types of heat transfer matrices are used in direct transfer type heat exchangers. The heat transfer matrices can generally be classified into plate‐fin surfaces, tubular surfaces and micro‐channels. Heat exchangers are analysed to obtain the temperature distribution in the exchanger and hence to calculate the performance variations due to longitudinal wall heat conduction, inlet flow non‐uniformity and inlet temperature non‐uniformity and fluid property variations. In the present section, the representation of exchangers for FEM analysis is introduced. The element models used for the analysis of various types of plate‐fin, tube‐fin and micro‐channel heat exchangers are given. As a result, accurate prediction of the thermal performance of a heat exchanger, when the effects of longitudinal wall heat conduction, inlet flow non‐uniformity and temperature non‐uniformity are significant, is almost impossible before the production and testing of a prototype. Longitudinal heat conduction in the wall and the fluids is detrimental to the heat exchanger performance. Longitudinal heat conduction in the fluids is generally negligible, except for liquid metals as working fluids. However, it is important for heat exchanger to be designed with high effectiveness and having high temperature gradients in the wall.

The inlet fluid flow and temperature distribution over the heat exchanger core is usually not uniform under ...