窄环形流道流体阻力与传热特性的研究

以蒸馏水为实验工质,用紫铜管对间隙为0.540～2.685 mm和间隙为0.540 mm的窄环形流道的流体分别进行了阻力和传热特性的实验研究。结果表明：窄环形通道内流体流动出现了从层流向湍流过渡提前的现象,且转捩雷诺数随着窄环隙尺寸的减小而降低。当Re〉750时,窄环形流道能够加强传热效果;而当Re〈750时,出现传热恶化现象,窄环形通道的传热系数小于理论计算的传热系数。

Study on Flow Friction and Heat Transfer Experimental Characteristics in Narrow Annuli

Fluid friction and heat transfer characteristics were experimented and studied on narrow annuli with the gap size ranging from 0.540 mm to 2.685 mm and the gapsize being 0.540 mm of copper tubes,with distilled water used as working fluid in the experiment.The experimental results showed the narrow annuli flow advanced ealier than the Reynolds number from the laminated to the turbulent,however,friction factor went down with decrease of the gap sizes.The narrow annuli channel can strengthen heat transfer when Re was bigger than 750,but the heat transfer was worsening when Re was smaller than 750.And the heat transfer coefficient in narrow annuli channel was smaller than that calculated theoretically.