Study About the Flow Pattern Map for Convective Boiling in Horizontal Microfin Tube of Refrigerant R1234ze

The prediction of the flow pattern for the new refrigerant HFO R1234ze has been made based on the general map of flow patterns for convective boiling of the smooth tube and microfin tube with mass flux G [kg/m2s] against quality x [–] during the phase change of saturation refrigerant. Applying the model of Wojtan et al. 2005 and Zhuang et al. 2016 for boiling in the smooth tube and the model of Rollmann and Spindler 2015 for the microfin tube to build the map for R1234ze, classified the regime of flow patterns and the transition line between them. The result focuses on the classification of the flow regime. Also, it considers the effect of mass flux, heat flow, and saturation temperature on the formation of the flow pattern map. The flow pattern maps for convective boiling have been compared for smooth tube and microfin tube, and the map of current refrigerant R134a and replacement of newest refrigerant HFO R1234ze on microfin tube. With the result of the flow pattern for the microfin tube of R1234ze, the regime of fully stratified flow is on the range of mass flux less than 60 kg/m2s for the whole range of quality. The helix flow appears on the microfin tube, while the smooth tubes do not have this pattern due to the microfin's effect on fluid flow inside the tube. Also, the dryout phenomenon is always a bad influence on the boiling in the smooth tubes; in microfin, it disappears.