Abstract:

Direct contact condensation characteristics in cool water of steam jet with non-condensable gas in it were investigated experimentally in this paper. The jet plume length of the mixture gas was obtained by measuring temperature field, which was used later to get condensation heat transfer coefficient. Using a circular nozzle with a diameter of 1.6 mm, this experiment covered the range of mixture gas mass flux from 100 to 330 kg·m^-2·s^-1, non-condensable gas content from 0 to 15% and cool water temperature from 300 to 340 K. The results showed that the existence of non-condensable gas led the decrease of temperature more slowly near the nozzle exit and the increase of jet plume length with increasing content of non-condensable gas. The effect of the addition of non-condensable gas on mixture mass flux and water subcooling was the same as pure steam jet. The condensation heat transfer coefficient was found to be in the range of 0.7 and 2 MW·m^-2·K^-1, and it decreased with increasing subcooling and non-condensable gas content, while the mixture mass flux has a little effect on it. Finally, correlations predicting the jet plume length and the condensation heat transfer coefficient were obtained by fitting the experimental dates.

Key words: direct contact condensing, non-condensable gas, jet plume length, heat transfer coefficient

摘要：

对含不凝气体蒸汽射流在冷水中直接接触冷凝现象进行了实验研究,通过测量流场中的温度分布确定汽羽长度,进而推导其传热系数。实验使用直径为1.6 mm的圆形喷嘴,出口混合气体质量流量密度在100~330 kg·m^-2·s^-1之间,不凝气体的含量在0~15%之间,冷水温度在300~340 K之间。实验结果表明:不凝气体的加入,使喷嘴出口附近的温度下降减慢;汽羽长度随不凝气体含量的增加而变长,其受喷嘴出口质流密度和过冷度的影响规律与纯蒸汽射流一致;冷凝传热系数在0.7~2 MW·m^-2·K^-1之间,随过冷度的增大和不凝气体含量的增加而减小,受气体流量的影响较小。对实验数据进行拟合,获得了汽羽长度的关联式,并由此得到了冷凝传热系数关联式。

关键词: 直接接触冷凝, 不凝气体, 汽羽长度, 传热系数