Optimizing design of heat exchangers based on targeted control of local thermal resistance ratio

Heat exchanger design is primarily based on lumped parameters method, employing an average thermal resistance approach. However, this conventional method often yields inaccurate results, thus necessitating excessive design margins. To overcome these limitations, a novel design methodology focusing on targeted control of the local thermal resistance ratio was proposed herein. Through systematic adjustment of the local thermal resistance ratio, this approach breaks away from the traditional uniform structure design, leading to the development of non-uniform heat exchangers. These non-uniform structures can achieve a significant improvement in the overall performance of heat exchangers. The proposed methodology utilized a sectional calculation approach to modify the physical structure of each heat exchange unit, thereby enabling the attainment of desired local thermal resistance ratios. Furthermore, a comprehensive evaluation criterion was established to select the optimal non-uniform structural configuration. This design was applied to a Z-channel heat exchanger, utilizing supercritical helium as the working fluid. The results demonstrate that, under identical heat exchange conditions, the pressure drop could be reduced by 8% compared with conventional uniform structures. The non-uniform configuration exhibits greater uniformity in thermal resistance, which can either reduce heat exchanger resistance or enhance heat transfer performance.