Study on condensation heat exchange characteristics of R513A in horizontal micro-fin tubes

The condensation heat exchange performance of R513A in a smooth tube and micro-fin tubes with different tooth densities is studied experimentally.By comparing the experimental value of the condensation heat exchange coefficient with the prediction value of the correlation,the applicability of the existing correlation to R513A is explored.The experiment is carried out in the range of condensation temperature 33,35,38 ℃ and mass flux from 50 to 150 kg/(m2·s).The experimental results show that the condensation heat exchange coefficient increases with the increase of mass flux,and the increase range of condensation heat exchange coefficient of the micro-fin tube is larger in the region of low mass flux.With the increase of tooth density,the heat exchange area in the tube increases,but the surface tension increases,the corresponding flow resistance increases,and the function of enhanced heat transfer is weakened.Compared with R134a,the enhanced heat transfer effect of the micro-fin tube on R513A is better.For the smooth tube,the prediction effect of the Bashar correlation is the best,while the prediction errors of the Cavallini correlation and the Dobson correlation are larger in the region of low mass flux.For micro-fin tubes,the prediction effect of the Yu correlation is the best,and both the Cavallini correlation and the Kedzierski correlation underestimate the condensation heat exchange characteristics in the tube.Based on the Kedzierski correlation,a new modified correlation is fitted.The prediction value of the modified correlation is in good agreement with the experimental value,and the average absolute error and the standard deviation are 7.8% and 8.5%,respectively.