Efficient transfer of energy is an important issue addressed by numerous scholars in the literature and various methods have been proposed for enhancing the heat transfer efficiency in heat exchangers. Among many different heat exchangers, helical tubes are one of the most prevalent types of heat exchangers which have many applications in industry. In a case study, effect of twisting technique on the heat transfer in a helical tube with oval cross section has been investigated numerically and the results have been compared with simple circular cross section helical tube. Effect of cross section aspect ratio and twisting ratio in different flow Reynolds numbers has been considered. Results have been presented in terms of Nusselt number, friction factor, PEC, entropy generation and contours of velocity, streamlines and temperature. Results indicate that twisting technique can significantly enhance the heat transfer and all cases have PEC values of above unit which indicates superiority of this method. Also the velocity contours and streamlines indicate that using twisting technique result in higher mixing in the flow which is the reason for higher heat transfer characteristics in twisted oval helical tubes.

中文翻译：

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扭转技术对扭转椭圆螺旋管传热特性影响的案例研究

能量的有效传递是许多学者在文献中关注的一个重要问题，并且已经提出了各种方法来提高换热器的传热效率。在许多不同的热交换器中，螺旋管是最普遍的热交换器类型之一，在工业中有许多应用。在案例研究中，对扭转技术对椭圆形截面螺旋管传热的影响进行了数值研究，并将结果与​​简单的圆形截面螺旋管进行了比较。考虑了不同流动雷诺数下截面长径比和扭曲比的影响。结果以努塞尔数、摩擦因数、PEC、熵产生以及速度、流线和温度等值线的形式呈现。结果表明，扭转技术可以显着增强传热，并且所有情况下的PEC值均达到上述单位，这表明该方法的优越性。此外，速度等值线和流线表明，使用扭转技术会导致流动中的更高混合度，这是扭转椭圆形螺旋管中具有更高传热特性的原因。