强化管外CFC11与HCFC123沸腾换热系数的对比试验研究

Comparative Experiments on Boiling Heat Transfer Coefficients of CFC11 and HCFC123 Outside an Enhanced Tube

本文通过强化管外CFC11与HCFC123沸腾换热系数的对比试验分析与研究，分别得出了HCFC123与CFC11沸腾换热系数，并对这两种工质的实际应用情况进行了分析。

The refrigerant CFC11 has commonly been adopted as the working fluid for centrifugal-compressor refrigerating systems of large capacity. According to the 'Montreal Protocol', CFC11 is one of the substances which ought to be phased out in the first place. It is deemed at the moment that the refrigerant HCFC123 is the most likely alternative to CFC11. In this work, comparative experiments on boiling heat transfer of CFC11 and HCFC123 outside an enhanced tube were carried out. Experimental results for boiling heat transfer coefficients of CFC11 and HCFC123 were presented and analyzed. It was found that the boiling heat transfer coefficients of CFC11 and HCFC123 increase rapidly with increasing heat flux and the boiling heat transfer coefficient of HCFC123 is smaller than that of CFC11 at given heat flux. Furthermore, the difference between the boiling heat transfer coefficients of CFC11 and HCFC123 increases with increasing heat flux as well, and the boiling heat transfer coefficient of HCFC123 is 29% smaller than that of CFC11 when the heat flux becomes 20.6 kW/m2. Replacing CFC11 by HCFC123 as the working fluid will therefore decrease the performance of heat exchangers in refrigerating systems. In the end, some suggestions for improvement of boiling heat transfer in the boiling chamber were offered to ensure the boiling heat transfer performance when using HCFC123.