Experimental And Mechanism Research Of R410A Two-phase Flow In Horizontal Enhanced Tubes

In this paper,experimental and mechanism research of the two-phase flow heat transfer of refrigerant R410A in various horizontal three-dimensional enhanced tubes is performed.The research objects are 3 copper pipes(OD 12.7mm)-2EHT1,2EHT2,and smooth tubes,and 4stainless-steel tubes(OD 9.52mm)-1EHT1,1EHT2 4LB and smooth tubes.Evaporation tests are conducted at a saturation temperature of 6?,over a mass flow range of 50-390kg/m~2s,with inlet and outlet vapor quality of 0.2 and 0.9,respectively;Condensation tests are conducted at a saturation temperature of 45?,over a mass flow range of 80-400kg/m~2s,with inlet and outlet vapor quality of 0.9 and 0.2,respectively.In this paper,the author systematically summarizes the research of two-phase flow heat transfer,including research routes,classic calculation models and new calculation methods.Principles of experimental systems,experimental instruments,experimental steps,and data processing methods are introduced.The author has performed single-phase tests,Wilson-plot tests,flow boiling and condensation heat transfer experiments on the tested tubes.Based on the experimental data,the heat transfer characteristics of each enhanced tube are analyzed.The author also evaluates existing correlations of single-phase,evaporation and condensation heat transfer coefficient and pressure drop with experimental data.Heat transfer characteristics of each tube are compared and heat transfer mechanism is analyzed from a numerical perspective.In this paper a predictive correlation fitting method based on dimensionless parameter analysis is proposed.The new correlation for evaporation heat transfer provides HTC prediction for the copper tubes with MAE of 7.94%and MRE of-2.26%;while for stainless steel tubes,it predicts with MAE and MRE of 14.39%and 4.61%,respectively.The new correlation for condensation heat transfer can predict 82.6%of the experimental data within the 8%error band;the average MAE of its prediction for the tested copper tubes and stainless-steel tubes are 3.38%and 5.39%,respectively.Meanwhile,a semi-empirical pressure drop prediction correlation fitting method based on non-linear surface fitting is proposed in this paper.The new formula predicts71.6%of all the two-phase flow data within the 25%error band,which shows stable prediction performance.The two formula fitting methods proposed in this paper have good practical effect in the prediction and application of heat transfer coefficient and frictional pressure drop of different tubes.They have unified equation form and intuitive analysis process,which make them reproducible and stable.At the end of this paper,the author introduces future work prospects,including visualization studies of unconventional enhanced tubes and flow boiling studies of multiport mini-channel.