Design of a Compact Helical Counterflow Heat Exchanger
Thirumalai Ananthanpillai, Aravindakshan
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Compact heat exchangers are desirable in many aerospace applications. New additive manufacturing approaches, such 3D printing, have enabled the fabrication of heat exchange devices utilizing geometries that cannot be fabricated using traditional approaches. The new geometries enabled by 3D printing may result in higher heat transfer using smaller devices, however, constraints associated with the fabrication of these devices also impose potential performance degradations. This document presents the design and analysis of a novel, compact counter flow heat exchanger which uses helically shaped passages to enhance the effectiveness of the heat transfer. Although the helical passages increase the heat transfer and reduce the size of the device, 3D print build constraints mandate that the passages are constructed with a lean angle for structural support that also increases the overall pressure loss of the fluid. An analytical model is developed, that can be used to trade the size and mass of the device for required heat transfer performance and acceptable levels of fluid pressure loss. Various working fluids, including water and cryogens are considered and designs that meet specified heat transfer goals while minimizing the pressure loss and volume of the device are presented. These designs are compared against a straight channel counter flow heat exchanger which can be fabricated using traditional approaches. This work demonstrates that for the same working fluids and for a set of given geometric constraints a tradeoff between heat exchange, pressure loss and compactness is observed while designing an optimized model.