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首页> 外文期刊>International Journal of Heat Exchangers >Smooth-and Enhanced-Tube Heat Transfer and Pressure Drop: Effect of Prandtl Number and the Role of Transition to Turbulence
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Smooth-and Enhanced-Tube Heat Transfer and Pressure Drop: Effect of Prandtl Number and the Role of Transition to Turbulence

机译：光滑和增强管的传热和压降：Prandtl数的影响以及湍流过渡的作用

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An extensive experimental investigation was carried out to determine the pressure drop and heat transfer characteristics in laminar, transitional, and turbulent flow through one smooth tube and twenty-three enhanced tubes. The working fluids for the experiments were air, water, ethylene glycol, and ethylene glycol/water mixtures; Prandtl number (Pr) ranged from 0.7 to 125.3. The smooth-tube experiments were carried out with Pr values of 0.7, 6.8, 24.8, 39.1, and 125.3; Pr values of 0.7, 6.8, and 24.8 were tested with enhanced tubes. Reynolds number (Re) range (based on the maximum internal diameter of a tube) was 200 to 55,000, depending on Prandtl number and tube geometry. The enhanced-tube friction factors are no more than 5.5 times the smooth-tube values. For some tubes, the friction factors are practically the same for 0.7 ≤ Pr ≤ 25, with moderate differences in laminar, transitional, or turbulent flow for some of the tubes. Consistent with the low-pressure-drop characteristics of these enhanced tubes, the increases in heat transfer coefficient are no more than 2.5 times the smooth-tube values for the Re and Pr ranges covered in the study. For most enhanced tubes, heat-transfer coefficients are insensitive to variations in the Prandtl number for liquids. There is a definite connection between the attainable friction or heat transfer and the transition process.
机译：进行了广泛的实验研究，以确定通过一个光滑管和二十三个增强管的层流，过渡和湍流中的压降和传热特性。实验的工作流体是空气，水，乙二醇和乙二醇/水混合物；普朗特数（Pr）在0.7到12.53之间。在Pr值为0.7、6.8、24.8、39.1和125.3的条件下进行了光滑管实验。用增强管测试了0.7、6.8和24.8的Pr值。雷诺数（Re）范围（基于管的最大内径）为200至55,000，具体取决于普朗特数和管的几何形状。增强管的摩擦系数不超过平滑管值的5.5倍。对于某些管子，摩擦系数在0.7≤Pr≤25时实际上是相同的，其中某些管子的层流，过渡流或湍流差异适中。与这些增强管的低压降特性一致，传热系数的增加不超过研究中涵盖的Re和Pr范围的光滑管值的2.5倍。对于大多数增强型管，传热系数对液体的普朗特数变化不敏感。在可获得的摩擦或热传递与过渡过程之间存在明确的联系。

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