Abstract The Wilson plot method has widely used to determine general heat transfer correlations, but this technique needs considerable experimental data. The Gnielinski correlation, however, simplifies the evaluation of the inside heat transfer coefficient of heating tubes only by using friction factor and hydraulic diameter. Nowadays, enhanced tubes, are used in an absorption refrigeration system to improve the thermal performance of the system. As these enhanced tubes have various heat transfer surfaces, the Wilson plot method based on numerous measured experimental data has been responsible for the evaluation of the Nusselt correlation; the validation of the Gnielinski correlation has not been found yet for enhanced tubes. The current study, thus, pursues to find the validity of the Gnielinski correlation to simplicate the assessment of the inside heat transfer coefficient of enhanced tubes over the Wilson plot method. First, a non-linear regression scheme developed by the Wilson plot method examined the Nusselt correlations of three different types of enhanced tubes including a smooth tube; friction factors of enhanced tubes, then, were measured to apply the Gnielinski correlation. Gnielinski correlation was modified using 103 data points and a new correlation was obtained, which showed a total mean error of 2.1%, and an agreement within ±5%.

中文翻译：

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非线性回归模型对Gnielinski相关系数评估增强管传热系数的验证：吸收式制冷系统的实验研究

摘要 威尔逊图法已广泛用于确定一般传热相关性，但该技术需要大量实验数据。然而，Gnielinski 相关性仅通过使用摩擦系数和水力直径简化了加热管内部传热系数的评估。如今，增强型管用于吸收式制冷系统以提高系统的热性能。由于这些增强型管具有不同的传热表面，因此基于大量实测实验数据的威尔逊图法一直负责评估 Nusselt 相关性；尚未发现增强管的 Gnielinski 相关性的验证。因此，目前的研究，试图找到 Gnielinski 相关性的有效性，以简化对增强管内部传热系数的评估，而不是威尔逊图法。首先，由威尔逊图法开发的非线性回归方案检查了三种不同类型的增强管（包括光滑管）的 Nusselt 相关性；然后，测量增强管的摩擦系数以应用 Gnielinski 相关性。使用 103 个数据点修改 Gnielinski 相关性并获得新的相关性，其显示总平均误差为 2.1%，一致性在 ±5% 内。然后，测量增强管的摩擦系数以应用 Gnielinski 相关性。使用 103 个数据点修改 Gnielinski 相关性并获得新的相关性，其显示总平均误差为 2.1%，一致性在 ±5% 内。然后，测量增强管的摩擦系数以应用 Gnielinski 相关性。使用 103 个数据点修改 Gnielinski 相关性并获得新的相关性，其显示总平均误差为 2.1%，一致性在 ±5% 内。