Comparison Of Nucleate Boiling Heat Transfer Characteristics Outside Tubes Between R1234ze And R134a

With the progress of human beings and the development of society,generations of refrigerants have been updated.The application of R134 a is gradually restricted because of the high value of GWP.For R1234 ze,its ODP value is 0 and GWP value is less than 1,which has attracted wide attention in the refrigeration industry.The experiment of boiling heat transfer of R1234 ze and R134 a outside the smooth tube and enhanced tube w studied,and the experimental data of boiling heat transfer outside the tube of R134a/R125 mixed refrigerant has been comparative analysis.From this,we may safely draw some conclusion:(1)The boiling heat transfer coefficient outside the tube increases with the increase of heat flux density regardless of the refrigerant.For enhanced tubes,the boiling heat transfer coefficient increases as the heat flux increases,but there is a slight repetition of the heat flux density near 50-60 kW/㎡.(2)The boiling heat transfer coefficient of R1234 ze is higher than that of R134 a under the same heat flux density.For enhanced tubes,the difference of the boiling heat transfer coefficient from R1234 ze to R134 a is decrease with the increase of heat flux density.(3)Compared with the boiling heat transfer data of the smooth tube and tube E43a(46fpi),tube E44a(50 fpi),tube E45a(56 fpi),the boiling heat transfer outside tube with a same heat flux grow from a small beginning into a mighty is Esmooth,E43 a,E44a.(4)Within the range of the Re number of the experimental study,the ratio of thermal resistance to total thermal resistance of enhanced tubes is greater than 50%,and there is no significant difference in the proportion of R134 a and R1234 ze under the same Re number.(5)The correlation equation of boiling heat transfer outside the tube is fitted by the analysis of the date from the mixer refrigerant with R134 a and R125,and the error between the calculated value and the experimental value is within 20%.