低质量流率蒸汽真空水平管内凝结传热特性实验研究

Experimental study of heat transfer characteristics of low mass flux steam condensation in vacuum horizontal tube

中文关键词: 凝结传热  水平管  海水淡化

英文关键词: condensation heat transfer  horizontal tube  desalination

中文摘要:

      在内径为38 mm、长度为3.4 m的水平管中，测量了饱和温度为50、60、70 ℃，质量流率小于8 kg/(m2·s)的饱和蒸汽的局部冷凝传热参数．在凝结过程中，由于重力的作用，管内上下部分存在两种换热模式．上部是膜状凝结换热区，下部是凝结液对流换热区．实验结果表明，随着管内入口饱和蒸汽和冷却水温差的增大，蒸汽在光滑管段内换热量增加，冷凝液增多，管段底部凝结液聚集区局部温度降低较大．随着总传热温差的增大，管壁顶部膜状凝结换热区传热系数降低，而管壁底部凝结液对流换热区变化较小．

英文摘要:

      Local condensation heat transfer parameters are measured for saturated steam at temperatures of 50, 60, 70 ℃ and mass fluxes less than 8 kg/(m2·s) in a horizontal tube with an inner diameter of 38 mm and a length of 3.4 m. In the condensation process, two heat exchange modes consist in the upper and lower parts of the tube due to the effect of gravity. The upper part is the film wise condensation heat exchange zone, and the lower part is the condensate convection heat exchange zone. The results of the experiment show that with the temperature difference between inlet saturated steam and cooling water increasing, the heat exchange of steam in the smooth pipe section increases, condensate increases, and the local temperature in the condensate accumulation area at the bottom of the pipe section decreases more. With the increase of the total heat transfer temperature difference, the heat transfer coefficient of the film wise condensation heat exchange zone at the top of the tube wall decreases, while the change of the condensate convection heat exchange zone at the bottom of the tube wall is smaller.