Abstract The aim of this study is to determine heat transfer and pressure drop characteristics in different louvered fin geometries for manufacturing of commercial louvered fin and round tube heat exchangers. Numerical simulations were carried out for various louver angles, louver lengths (pitches), fin pitches and frontal air velocities. The heat transfer and pressure drop characteristics of the louvered fin and round tube heat exchangers, Colburn and friction factors, were respectively normalized with Colburn and friction factors of the flat plate fin and round tube heat exchangers operating under the same conditions and they were presented as the relative Colburn factor j∗ and the relative friction factor f∗. Thermal & hydraulic performance was presented as JF∗. Temperature and local Nusselt number contours, and streamline patterns were provided to reveal the mechanisms behind the heat transfer enhancement. Among different heat exchangers for which heat transfer and pressure drop characteristics were obtained, one was chosen to manufacture a real size heat exchanger. Flow visualization studies were also conducted with a PIV system in an open water channel to determine whether the flow structure is louvered directed or not. The louvered fin heat exchanger tested in the PIV system was a five times scaled up model of the real size louvered fin heat exchanger and made from a transparent plexiglas material. PIV results were presented and evaluated based on streamlines and velocity vectors. Furthermore, a numerical analysis was performed using exactly the same dimensions and conditions of the model tested in the PIV system. The comparison between numerical and experimental results was done to validate the numerical model. Consequently, the performance of the fabricated real size heat exchanger was tested at different air velocities in a wind tunnel in a conditioned room. The experimental results were compared with numerical analyses and found to be compatible with each other. Finally, thermal and hydraulic performance of the louvered fin and round tube heat exchanger was compared with a wavy fin and round tube heat exchanger with identical size and specifications. It was found that the thermal and hydraulic performance of the louvered fin and round tube heat exchanger is higher than that of the wavy fin and round tube heat exchanger. The Colburn factor j, friction factor f and JF of the louvered fin and round tube heat exchanger are higher about 16.8–7%, 19.9–8.2% and 10–4.3% than that of the wavy fin and round tube heat exchanger depending on the Reynolds number, respectively.

中文翻译：

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百叶窗翅片和圆管换热器空气侧热力和水力性能的实验、计算和流动可视化研究

摘要 本研究的目的是确定用于制造商用百叶窗翅片和圆管换热器的不同百叶窗翅片几何形状的传​​热和压降特性。对各种百叶窗角度、百叶窗长度（节距）、翅片节距和正面空气速度进行了数值模拟。百叶窗翅片和圆管换热器的传热和压降特性、科尔本和摩擦系数分别用科尔本和相同条件下运行的平板翅片和圆管换热器的摩擦系数归一化，它们表示为相对科尔本系数 j∗ 和相对摩擦系数 f∗。热力和水力性能表示为 JF*。温度和局部努塞尔数等值线，并提供了流线型图案来揭示传热增强背后的机制。在获得传热和压降特性的不同换热器中，选择一个来制造实际尺寸的换热器。还在开放水道中使用 PIV 系统进行了流动可视化研究，以确定流动结构是否是百叶窗导向的。在 PIV 系统中测试的百叶窗翅片换热器是实际尺寸百叶窗翅片换热器的五倍放大模型，由透明有机玻璃材料制成。基于流线和速度矢量呈现和评估 PIV 结果。此外，使用与 PIV 系统中测试的模型完全相同的尺寸和条件进行了数值分析。对数值和实验结果进行了比较以验证数值模型。因此，在空调房间的风洞中以不同的空气速度测试了所制造的实际尺寸热交换器的性能。将实验结果与数值分析进行了比较，发现它们是相互兼容的。最后，将百叶窗翅片和圆管换热器的热力和水力性能与具有相同尺寸和规格的波浪翅片和圆管换热器进行了比较。结果表明，百叶窗翅片圆管换热器的热工水力性能高于波浪翅片圆管换热器。百叶窗翅片和圆管换热器的科尔本系数 j、摩擦系数 f 和 JF 较高，约为 16.8-7%、19.9-8。