Enhanced Design of Cross-Flow Microchannel Heat Exchanger Module for High-Performance Aircraft Gas Turbine Engines

Abstract

This study explores the design of highly compact air–fuel heat exchangers for high-performance aircraft turbine engines. The heat exchangers consist of a large number of modules that can be brazed together into a rectangular or annular outer envelope. Inside the module, fuel flows through parallel microchannels, while air flows externally perpendicular to the direction of the fuel flow over rows of short, straight fins. A theoretical model recently developed by the authors for a single module is both validated experimentally, by simulating aircraft fuel with water, and expanded to actual heat exchangers and JP-8 aircraft fuel. An optimization study of the module’s geometrical parameters is conducted for high-pressure-ratio engine conditions in pursuit of the highest heat transfer rate. These parameters are then adjusted based on such considerations as microfabrication limits, stress and rupture, and the need to preclude clogging of the fuel and air passage. Using the revised parameters, the analytical model is used to generate effectiveness plots for both rectangular and annular heat exchangers with one air pass and one, two, or three fuel passes. These results demonstrate both the effectiveness of the module design and the versatility of the analytical tools at designing complex heat exchangers for high-performance aircraft gas turbine engines.