This study develops a tube element method for thermal performance analysis of fin-and-tube heat exchangers operating with airflow nonuniformity. Experimental investigations have been performed on two fin-and-tube heat exchangers to validate the proposed tube element method. The heat exchanger tubes are discretized into a finite number of tube elements. These tube elements are observed as distinctive sub-exchangers, described by the appropriate heat transfer relations. The tube element method is capable of predicting the effectiveness in heat exchangers with complex tube circuitries, operating with either uniform or nonuniform airflows. The following general conclusions are obtained: the size of the effectiveness deterioration depends mainly on the heat exchanger operating point and on the degree of airflow nonuniformity. The effectiveness deterioration is highest when the heat capacity rate ratio is 1 and lowest when the heat capacity rate ratio is 0, for airflow nonuniformities with orientation perpendicular to the tube axis. The opposite is seen for airflow nonuniformities with orientation parallel to the tube axis. The heat exchanger effectiveness deterioration is up to 5.2% and 14.5% for complex nonuniform airflow profiles encountered in real-world operation, having airflow nonuniformity degrees of 0.43 and 0.81, respectively. Further, it was found that the heat exchanger tube circuitry design, the thermal resistance ratio and the airflow regime also influence the size of the effectiveness deterioration.

这项研究开发了一种管元方法，用于分析气流不均匀的翅片管式热交换器的热性能。在两个翅片管式换热器上进行了实验研究，以验证所提出的管元法。热交换器管离散成有限数量的管元件。这些管元件被观察为独特的子交换器，通过适当的传热关系进行描述。管元法能够预测在具有均匀或不均匀气流的复杂管回路的热交换器中的有效性。得到以下一般结论：效率下降的大小主要取决于热交换器的工作点以及气流不均匀的程度。对于垂直于管轴方向的气流不均匀性，当热容率比率为1时，效率下降最高，而当热容率比率为0时，效率下降最低。对于平行于管轴方向的气流不均匀现象，则相反。对于实际运行中遇到的复杂的非均匀气流曲线，热交换器的效率恶化分别高达5.2％和14.5％，气流不均匀度分别为0.43和0.81。此外，已经发现，热交换器管电路设计，热阻比和气流状态也影响有效性恶化的大小。垂直于管轴方向的气流不均匀。对于平行于管轴方向的气流不均匀现象，则相反。对于实际运行中遇到的复杂的非均匀气流曲线，热交换器的效率恶化分别高达5.2％和14.5％，气流不均匀度分别为0.43和0.81。此外，已经发现，热交换器管电路设计，热阻比和气流状态也影响有效性恶化的大小。垂直于管轴方向的气流不均匀。对于平行于管轴方向的气流不均匀现象，则相反。对于实际运行中遇到的复杂的非均匀气流曲线，热交换器的效率恶化分别高达5.2％和14.5％，气流非均匀度分别为0.43和0.81。此外，已经发现，热交换器管电路设计，热阻比和气流状态也影响有效性恶化的大小。气流不均匀度分别为0.43和0.81。此外，已经发现，热交换器管电路设计，热阻比和气流状态也影响有效性恶化的大小。气流不均匀度分别为0.43和0.81。此外，已经发现，热交换器管电路设计，热阻比和气流状态也影响有效性恶化的大小。