Abstract

Compact recuperative heat exchangers are critical components in supercritical carbon dioxide (sCO₂) waste heat to power conversion systems. To investigate their thermohydraulic performance, a model based on the segmental design and the ε-NTU method has been developed. Four different types of heat exchanger have been considered: printed circuit heat exchanger with straight channels (PCHE-SC); printed circuit heat exchanger with zigzag channels (PCHE-ZC); microtube heat exchanger (MTHE); and microtube heat exchanger with separator sheets (MTHE-SS). The performance of the heat exchangers for different fluid mass flow rates, temperatures, and lengths was investigated in terms of Nusselt number, heat transfer coefficient, friction factor, pressure drop, heat transfer rate, entropy generation rate, and augmentation entropy generation number. Results show that these parameters significantly impact on the thermohydraulic performance of compact recuperative heat exchangers and their optimal design. For the same operating conditions and equal heat transfer rate, PCHE-ZC and MTHE-SS can have a significantly smaller size than PCHE-SC and MTHE. The augmentation entropy generation number also demonstrates the improved performance and compactness that can arise from zigzag channels and separator sheets, making them suitable for demanding high pressure and temperature applications such as sCO₂ heat to power conversion systems.

摘要

紧凑型回热式换热器是超临界二氧化碳 (sCO ₂ ) 废热发电系统中的关键部件。为了研究它们的热工水力性能，基于分段设计和ε-NTU的模型方法已开发。已经考虑了四种不同类型的热交换器： 带直通道的印刷电路热交换器 (PCHE-SC)；带锯齿形通道的印刷电路热交换器（PCHE-ZC）；微管换热器（MTHE）；和带隔板的微型管换热器 (MTHE-SS)。根据努塞尔数、传热系数、摩擦系数、压降、传热率、熵产生率和增熵产生数，研究了换热器在不同流体质量流量、温度和长度下的性能。结果表明，这些参数对紧凑型换热器的热工水力性能及其优化设计有显着影响。在相同的工况和相同的传热率下，PCHE-ZC 和 MTHE-SS 的尺寸可以明显小于 PCHE-SC 和 MTHE。熵增代数还展示了锯齿形通道和隔板可以提高性能和紧凑性，使其适用于苛刻的高压和高温应用，例如 sCO₂热电转换系统。