Experimental Investigation On Condensation Heat Transfer Enhancement Of R134a Refrigerant In Helical Baffle Heat Exchangers

As the Montreal Protocol has been implemented, people pay more attention to environment protection. Refrigerant R22 will be phased out gradually due to its depletion of the ozone layer. However, R134 a is an environmental friendly refrigerants which will be used as main alternatives of R22. Therefore,it is necessary to investigate the condensation heat transfer performances of it. More over,in order to save energy, it’s necessary to use heat transfer enhancement techniques like helical baffle and new effective enhanced heat transfer tubes to enhance the condensation heat transfer performance of refrigerants.In this work, the condensation heat transfer performance of smooth tube helical baffle condenser(HBS), low fin tube helical baffle condenser(HBF) and petal shaped fin tube helical fin helical baffle condenser(with discharge channel, HBP; without, HBP-DC) were investigated at saturation temperature of 35℃ and 39 ℃. According to the result of the experiment, a semi-experiential, semi-theoretical model of condensation HTC was suggested in this work, and we made a comparison of different condenser, and investigated the heat transfer enhancement of two enhanced tubes. In the same time, the effect of discharge channel would be studied in this work.The influences on condensation HTCs such as saturated temperature, wall subcooling, flow conditions et.al would be discussed in this paper, and the distribution of the thermal resistances would also be analyzed.According to the result of this work, the rank of the condensation HTCs of the three condensers is: HBP>HBF>HBS. The two enhanced tube can contribute to the condensation heat transfer effectively. On stainless steel three-dimensional fin tube, under a same wall sub-cooling, the enhancement factor of HBP and HBF are 1.68~1.96 and 2.36~4.84 times than those on stainless steel plain tube, respectively; The condenser with discharge channel was influenced by the effect of vapor “short circuit”, and its condensation performances was greatly weaken. The ratio of outside heat resistance of the three condenser are: 77.4%~79.1%, 68.4%~70.3% and 65.0%~66.2%, respectively. The petal shaped tube can low down the outside heat resistance effectively.