| Organic Rankine Cycle（ORC）power generation technology can fully use lowtemperature waste heat resources and is a potential solution to improve energy efficiency and reduce carbon emissions.The working fluid is regarded as the blood of the ORC power generation system,and its thermophysical properties and heat transfer characteristics significantly impact the ORC system’s performance.However,in the current application research of ORC systems,the research on the heat transfer characteristics of organic working fluid under medium and high-temperature conditions is insufficient.The relevant experimental data are few,and the heat transfer mechanism needs to be further revealed.Research on boiling heat transfer characteristics,based on numerical simulation to assist in explaining and revealing heat transfer flow phenomena and laws and expanding the high-temperature heat transfer flow database in organic working fluids.The main research contents are as follows:（1）The composition,experimental principle,experimental process,experimental data processing method,and experimental uncertainty analysis of the organic working fluid flow heat transfer experimental system are introduced.The heat balance experiment and singlephase heat transfer experiment are carried out to verify the reliability and experimental measurement accuracy.The numerical simulation model of organic working fluid heat transfer flow was established,including selecting mesh division,boiling and turbulence models,boundary conditions,and solution methods,and the mesh independence and model accuracy were verified.（2）The experimental study on the heat transfer characteristics of organic working fluids R245 fa and R152 a in high-temperature flow boiling in a horizontal tube was carried out.Combined with numerical simulation,the influence law and heat transfer mechanism of vapor quality,mass flux,and evaporation temperature on the flow boiling heat transfer coefficient and heat transfer mechanism were obtained.The influence degree and changing trend of flow boiling heat transfer coefficients of R245 fa and R152 a by various factors were studied.The results show that the flow boiling heat transfer coefficients of R245 fa and R152 a are both affected by mass flux,vapor quality and evaporation temperature,and are the most affected by vapor quality.（3）The heat transfer performance of R245 fa and R152 a at the evaporation temperature of 70℃ was compared,and the reason for the difference in heat transfer coefficient was analyzed.The experimental data were compared with several heat transfer correlations,and a more accurate correlation was selected.The correction study on the heat transfer correlation was carried out with the experimental data,and a more accurate heat transfer correlation was obtained.The predicted mean absolute deviation of the corrected correlation to the experimental data was 24.32%,and 73.23% data points was within ±30%. |
