Condensation Heat Transfer in a Horizontal Rotating Cylinder

以直径为294 mm的亚克力圆柱体和直径为310 mm的不锈钢圆柱体为实验对象，以R113为冷凝流体，对绕其水平轴线旋转的圆柱体内表面层流膜冷凝换热进行了实验和理论研究。通过板式刮刀将凝结液取出，安装在旋转圆筒顶部的内表面上，从而在圆筒内表面形成非常薄的凝结液薄膜。实验结果表明，冷凝蒸汽与气缸壁外表面之间的总换热系数受壁面与冷凝膜的导热阻力比和转速的影响。基于超薄膜假设，采用数值方法进行理论研究。在较低的转速下，凝结的液体返回到圆筒的底部。液体背面的旋转速率极限(临界旋转Froud数)表示为感热和潜热比以及Prandtl数的函数。基于总换热系数的Nusselt数num与实验结果吻合较好，在临界旋转Froud数附近，刮板角位置对num的影响非常显著，并给出了这一最佳角度。

Heat transfer in laminar film condensation on the inner surface of a cylinder rotating about its horizontal axis are investigated experimentally and theoretically.The experimental data are obtained with the acrylic cylinder of 294 mm ID and the stainless steel cylinder of 310 mm ID, and R113 as condensation fluid. Condensed liquid are removed by the plate type scraper, installed on the inner surface at the top of the rotating cylinder, so that very thin film of condensed liquid are formed on the inner surface of cylinder. As the experimental results, over-all coefficient of heat transfer between condensing vapor and the outer surface of the cylinder wall are shown to be affected by the heat conduction resistance ratio of the wall and the condensed film, and rotation rates.Theoretical studies are performed by means of numerical method, based on the assumption of very thin film. At low rotation rates, the condensed liquid backs to the bottom of the cylinder. This rotation rates limit for the back of liquid (critical rotation Froud number) is shown as a function of the ratio of sensitive and latent heat, and Prandtl number. Nusselt number based on over-all heat transfer coefficient,Num are shown by the two parameter and to be good agreement with the experiments.At region near the critical rotation Froud number, effects of the angle position of the scraper on Num become notable, this optimum angle is shown also.