An experimental investigation on the boiling heat transfer and frictional pressure drop of R245fa in a 7 mm horizontal micro-fin tube was performed.The results show that in terms of flow boiling heat transfer characte...An experimental investigation on the boiling heat transfer and frictional pressure drop of R245fa in a 7 mm horizontal micro-fin tube was performed.The results show that in terms of flow boiling heat transfer characteristics,boiling heat transfer coefficient(HTC)increases with mass velocity of R245fa,while it decreases with the increment of saturation temperature and heat flux.With the increase of vapor quality,HTC has a maximum and the corresponding vapor quality is about 0.4,which varies with the operating conditions.When vapor quality is larger than the transition point,HTC can be promoted more remarkably at higher mass velocity or lower saturation temperature.Among the four selected correlations,KANDLIKAR correlation matches with 91.6%of experimental data within the deviation range of±25%,and the absolute mean deviation is 11.2%.Also,in terms of frictional pressure drop characteristics of flow boiling,the results of this study show that frictional pressure drop increases with mass velocity and heat flux of R245fa,while it decreases with the increment of saturation temperature.MULLER-STEINHAGEN-HECK correlation shows the best prediction accuracy for frictional pressure drop among the four widely used correlations.It covers 84.1%of experimental data within the deviation range of±20%,and the absolute mean deviation is 10.1%.展开更多
With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitut...With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitute for R245fa in heat pump systems.In this study,the performance and economic analysis of heat pump systems with R245fa and R1233zd(E)as refrigerants are carried out.The results show that the total cost of R1233zd(E)system is more than 10%higher than that of R245fa system under the same heating load.With the increase of condensation temperature,the heating capacity of both systems decreases,and with the increase of evaporation temperature,the heating capacity increases.The variation trend of coefficient of performance(COP)of the two systems is similar to that of heating capacity.Under the same operating conditions,the COP of R1233zd(E)system is 19.2%higher than that of R245fa system,and the volumetric heat capacity of R1233zd(E)is 9.0%–13.9%lower than that of R245fa.The economic analysis results show that the investment cost of R1233zd(E)system is low under the same heat load.展开更多
Numerical simulation on R245fa condensation inside an inner diameter of 8 mm horizontal tube is researched in this paper. The effect of variation in velocity, condensation temperature and superheat of inlet steam and ...Numerical simulation on R245fa condensation inside an inner diameter of 8 mm horizontal tube is researched in this paper. The effect of variation in velocity, condensation temperature and superheat of inlet steam and variation in cooling water temperature on heat transfer coefficient are investigated as a parametric study. Condensation process of steam has been successfully modeled by applying a user defined function (UDF) added to the commercial computational fluid dynamics (CFD) package. By analyzing the corresponding condensate contours and the curves of local heat transfer coefficient, the relationships between condensation heat transfer coefficient and various parameters of R245fa inside horizontal tube are obtained. It shows that the heat transfer coefficient increases by the increase in velocity, condensation temperature and superheat of inlet steam and the decrease in cooling water temperature. The errors between the heat transfer coefficient of simulation result and model of Wang and Shah are within ±30%. The parametric study will provide the basis for designing efficient heat exchangers of R245fa.展开更多
基金Project(51606162)supported by the National Natural Science Foundation of ChinaProject(2018JJ2399)supported by the Natural Science Foundation of Hunan Province,China
文摘An experimental investigation on the boiling heat transfer and frictional pressure drop of R245fa in a 7 mm horizontal micro-fin tube was performed.The results show that in terms of flow boiling heat transfer characteristics,boiling heat transfer coefficient(HTC)increases with mass velocity of R245fa,while it decreases with the increment of saturation temperature and heat flux.With the increase of vapor quality,HTC has a maximum and the corresponding vapor quality is about 0.4,which varies with the operating conditions.When vapor quality is larger than the transition point,HTC can be promoted more remarkably at higher mass velocity or lower saturation temperature.Among the four selected correlations,KANDLIKAR correlation matches with 91.6%of experimental data within the deviation range of±25%,and the absolute mean deviation is 11.2%.Also,in terms of frictional pressure drop characteristics of flow boiling,the results of this study show that frictional pressure drop increases with mass velocity and heat flux of R245fa,while it decreases with the increment of saturation temperature.MULLER-STEINHAGEN-HECK correlation shows the best prediction accuracy for frictional pressure drop among the four widely used correlations.It covers 84.1%of experimental data within the deviation range of±20%,and the absolute mean deviation is 10.1%.
基金supported by theKorea Institute of Energy Technology Evaluationand Planning (KETEP) grant funded by the Korean Government (MOTIE) (No. 20202020900060,The development and application of operational technology in smart farm utilizing waste heat fromparticulates reduced smokestack).
文摘With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitute for R245fa in heat pump systems.In this study,the performance and economic analysis of heat pump systems with R245fa and R1233zd(E)as refrigerants are carried out.The results show that the total cost of R1233zd(E)system is more than 10%higher than that of R245fa system under the same heating load.With the increase of condensation temperature,the heating capacity of both systems decreases,and with the increase of evaporation temperature,the heating capacity increases.The variation trend of coefficient of performance(COP)of the two systems is similar to that of heating capacity.Under the same operating conditions,the COP of R1233zd(E)system is 19.2%higher than that of R245fa system,and the volumetric heat capacity of R1233zd(E)is 9.0%–13.9%lower than that of R245fa.The economic analysis results show that the investment cost of R1233zd(E)system is low under the same heat load.
文摘Numerical simulation on R245fa condensation inside an inner diameter of 8 mm horizontal tube is researched in this paper. The effect of variation in velocity, condensation temperature and superheat of inlet steam and variation in cooling water temperature on heat transfer coefficient are investigated as a parametric study. Condensation process of steam has been successfully modeled by applying a user defined function (UDF) added to the commercial computational fluid dynamics (CFD) package. By analyzing the corresponding condensate contours and the curves of local heat transfer coefficient, the relationships between condensation heat transfer coefficient and various parameters of R245fa inside horizontal tube are obtained. It shows that the heat transfer coefficient increases by the increase in velocity, condensation temperature and superheat of inlet steam and the decrease in cooling water temperature. The errors between the heat transfer coefficient of simulation result and model of Wang and Shah are within ±30%. The parametric study will provide the basis for designing efficient heat exchangers of R245fa.
