Experimental Study On The Condensation Heat Transfer Of R290 And R1234ze In Horizontal Minichannels

Microchannel heat exchangers play an important role in improving the energy efficiency of the refrigeration and air-condition systems because the compacted and efficiency. Due to the HCFCs refrigerant need to be replaced progressively, the performance of the refrigerant with low GWP become a research hotspot nowadays.In this paper, the condensation heat transfer coefficients and pressure drop characteristics during condensation of R290 and R1234 ze were experimantally investigated in the circular and the rectangular horizontal microchannel, and the experimental results were compared with that of R22. The inner diameter of the circular tube is 1.085 mm and the hydraulic diameter of rectangular tube is 0.952 mm. During the experiments, the saturation temperatures of the refrigerations are 40℃ and 50℃, the mass flow rate of the R22 is 200~1200 kg/(m2·s), that of the R290 is 200~650 kg/(m2·s), and the mass folw rate of R1234 ze is 200~800 kg/(m2·s), the quality range is from 0 to 1.In this paper, the influence of the mass flow rate, quality, saturation temperature and channel geometry to the frictional pressure drop and the heat transfer coefficient are researched. The frictional pressure drop and the heat transfer coefficient are compared with each other, and the experimental data is also compared with the existing correlations. Results show that, the frictional pressure drop and the heat transfer coefficient increase with mass flux and quality, and decrease with saturation temperature. The frictional pressure drop and the heat transfer coefficient in the rectangular tube are larger than those in the circular tube. The frictional pressure drop and the heat transfer coefficient of R290 is the largest and those of the R22 are the smallest.The comparison of the experimental results with the existing correlations indictated that the Gerimella and Kim correlations agree well with the pressure drop results, and the Sun and Mishima and Lopez Belchi correlations predict higher than experimental data. The Kim, Koyama and Wang correlations agree with the heat trandfer data well, while the Shah correlation only agree with the data of R1234 ze well. The Bohdal correlation over predicts all the heat transfer data.