Experimental determination of the role of roughness and wettability on pool-boiling heat transfer of refrigerant

In order to investigate pool boiling heat transfer characteristics of refrigerants on different surfaces, an experimental rig is established and verified in this study. The pool boiling heat transfer experiment is conducted with R134a at three saturation temperatures. Six surfaces with Ra roughness ranging from 0.133 to 5.742 μm and two types of wettability are tested in the study. The heat flux varies from 40 to 280 kW/m². Experimental results indicate that higher roughness is favorable to boiling heat transfer. Shieldex coating on copper surfaces can deteriorate heat transfer by 20% approximately. Visualization analysis was carried out with a high-speed camera to study bubble behavior. A new-found mode of bubble departing was observed at lower heat flux. Besides, the data were correlated in the form of Rohsenow correlation, and comparison and supplement are concluded based on data obtained in this study.