Test System Design And Experimental Investigation Of Horizontal In-tube Flow Boiling Heat Transfer Of R245fa At High Saturation Temperature

The working fluid is the core of refrigeration system,heat pump system,and Organic Rankine Cycle(ORC)system.The two-phase flow heat transfer characteristics of the organic working fluid in tube directly affect the thermal and economic performance of system.In terms of the accurately design of phase change heat exchange equipment and thermal system,it is very important to study the phase change and flow characteristics of organic working fluid.At present,most of the experimental researches on the heat transfer characteristics of two-phase flow aim at low temperature evaporation process of the heat pump and refrigeration system,and the experimental data on heat transfer characteristics of high temperature phase change what applied to ORC are lacking.So,in this paper,an experimental test rig is designed and established for the test of the in-tube heat transfer and flowing characteristics of the organic working fluids with high temperature and high pressure,and relevant experimental research is carried out.The main research con tents are as follow:(1)Based on the principle of single-tube experimental test,a design method of the organic working fluid single-tube experimental system which integrates of boiling and condensation is proposed.Based on the selected working fluid,the flow boiling and condensation test sections are designed,and selection of experimental auxiliary partial by collation was carried out.Lastly,the experimental system of the organic w orking fluid in single-tube can realize the integration of boiling and condensation is designed;(2)Based on the design of the single-tube experimental test system,an experimental test rig is established for the test of the single-tube phase change heat transfer and flowing of the organic working fluids,and a dynamic test on the experimental rig was carried out.Furthermore,a complete experimental system data processing model was established,and the experimental results were overall analysis.Experimental test results show that the experimental system has the characteristics of high stability,small fluctuations,easy adjustment,non-conflict,excellent control accuracy,and can satisfy various of organic working fluid to carry out flow boiling or condensation heat transfer experiments in the tube.Besides,the two ends of the test section in the experimental system are connected by flanges,so the test sections with different diameters and tube types can be replaced according to the experimental needs,which provides experimental conditions for the study of the phase change heat transfer characteristics of the organic working fluid;(3)The experimental study on the high-temperature flow boiling transfer characteristics of the organic working fluid R245 fa in a horizontal smooth tube was carried out,and effects of the main parameters such as mean quality,mass flow rate and saturated evaporation temperature on the average flow boiling heat transfer coefficient and wall temperature distribution along the tube were analyzed.Based on the classical heat transfer correlation,a modified semi-empirical heat transfer correlation is proposed.