Paper No 345 – Experimental investigation of local nucleate boiling heat transfer and mixing ratio on copper surface about mixture R 32 / R 1234ze(E) – 13th IEA Heat Pump Conference, Jeju, Korea
In this study, the heat transfer coefficients of R 32 and R 1234ze(E) were measured, respectively. In order to mixing affect, the heat transfer coefficient and mass ratio were measured and analyzed by changing the mixture mass ratio of the R 32 / R 1234ze(E) from 3 to 100 kW/m2 heat flux. By attaching a thermocouple directly to the copper boiling surface, raw data were successfully measured without obtaining the surface temperature by a calculation formula. The mass fraction on the heating surface were also analyzed by gas chromatography. The above methods have made it possible to acquire data with high accuracy. The heat transfer coefficient was decreased for the zeotropic refrigerant mixtures compared to the pure refrigerants, specifically, the data of refrigerant mixture R 32 / R 1234ze(E) with a mass ratio of 0.2/0.8 showed the minimum value. The variation of the mass ratio near the heating surface that was not observed for the near-azeotropic refrigerant mixture occurred for the zeotropic refrigerant. In zeotropic mixtures, it was clear that the change in properties occurred in the boiling region.