Abstract:

The flow，resistance and heat transfer performance in fluted tube were numerically investigated and compared with smooth tube by application of three-dimensional steady incompressible fluid turbulence model and water as the working medium. Results showed that the heat transfer performance became stronger in fluted tube than that in smooth tube because of the larger local temperature gradient of the bottom layer flow by disturbance and vortex flow. The fluted structure could significantly enhance the disturbance and mixing of fluids，and produce radial vortex，reduce the boundary layer thickness，increase fluid turbulence，and promote the surface boundary layer to update rapidly. As a result，heat transfer was enhanced but the flow resistance increased also. The heat transfer enhancement mechanism in the fluted tube was analyzed using the field synergy principle. Another important way to strengthen the heat exchange was to make the angle of velocity and temperature fields smaller and to improve the coordination level between velocity field and temperature field.

摘要：

以水为工作介质，应用三维常物性不可压缩流体稳态湍流模型，对凹槽管内的流动、阻力与传热性能进行了模拟研究，并与光滑管进行对比。结果表明，凹槽管主要通过扰动、漩涡使层流底层的局部温度梯度变大，从而使换热性能比光滑管强。凹槽结构能显著增强流体的扰动和相互掺混，并产生径向漩涡，减小边界层厚度，加剧流体湍流，促使边界层表面快速更新，从而强化传热，但同时也使其流动阻力增加。最后应用场协同理论，从局部换热角度分析了凹槽管强化换热的机制。强化换热另一重要途径是使换热器内速度场与温度梯度场之间夹角变小，改善速度场与温度场协同程度。