Research On R245fa Condensation Heat Transfer Characteristic Inside Horizontal Tubes

Currently, the process energy consumption leads to environmental burden. Energy and environmental issues have become a major problem all over the world which needs to be solved quickly. Medium and low temperature waste heat from industrial emissions is precious waste heat resources having enormous energy saving potential. R245 fa working fluid during heat recovery has a thick single-day advantage, and it can be used as good working substance in organic Rankine cycle system. Meanwhile, R245 fa substituting other refrigerants has made relevant research with the development of refrigeration and air conditioning industry. Condensation heat transfer characteristics of R245 fa in a horizontal pipe is mainly studied in the paper.According to the research purpose, the author designed and built the experiment of R245 fa condensation heat transfer in a horizontal pipe. The content, steps and data processing method of the experiment of R245 fa condensation heat transfer in a horizontal pipe are introduced in detail. The uncertainty of the experiment system is analyzed, which insure the reliability of experiment system and experiment method. The experiment of R245 fa condensation heat transfer in a horizontal pipe is done in this paper.The characteristics of R245 fa steam condensation heat transfer in a horizontal circular tube are studied by analyzing the effect of steam mass flow rate, inlet temperature, working medium dry degree, cooling water temperature and cooling water flow rate. The regulars of R245 fa condensation heat transfer in a horizontal circular tube are got, and it can be expressed as follows:1. As steam mass flow rate increases from 4.38kg/h to 10.05kg/h, the condensation coefficient increases. When the steam inlet mass flow rate increases, the steam velocity increases, the force acting on liquid film generated by the process of condensation increases, so that the film thickness decreases, reducing resistance generated by the film, condensation heat transfer coefficient increases.2. When the condensate temperature rises from 51.2℃to 58.9℃, the condensation heat transfer coefficient reduces with the rise of condensation temperature, it is mainly because the condensation temperature difference causes the different physical properties.3. When the inlet dryness varies from 0.89 to 1, the condensation heat transfer coefficient increases. The reason is when the dryness entrance increases, gas velocity and surface tension becomes larger, gas-liquid two-phase interfacial shear stress increases, their total effect makes condensate film thinner,which is generated by wall releasing, heat resistance decreases.4.When the cooling water temperature decreases from 40℃to37℃, the condensation heat transfer coefficient increases. The cooling water temperature is lower, the greater the heat transfer coefficient. When the cooling water is lower, the tube wall temperature is lower, and the condensation heat transfer temperature difference rises.5. The cooling water flow rate rises from 0.69L/min to 0.87L/min, the condensation heat transfer coefficient increases. The cooling water side heat transfer strengthen, at the same time, the changes in temperature of cooling water side is reduced, the difference of heat transfer temperature decreases, and the heat transfer coefficient increases.R245fa condensation in tube is simulated by using the CFD software, the VOF model, and working medium steam condensation heat transfer in a horizontal tube is analyzed by combing with UDF programming. The experimental conditions are simulated, the error of simulation results and experimental results less than17%.This paper is mainly on the study of pure working medium R245 fa condensation heat transfer in tube. And by controlling the operation conditions of operation parameters, the state of efficient condensation heat transfer in a horizontal pipe can be kept. It can provide basis for improving the heat-exchanging unit heat transfer coefficient, saving energy and the next step development design R245 fa efficient condensation heat exchanger.