Flow boiling heat transfer characteristics of R245fa in horizontal micro-fin tube

To intensify the heat transfer process of evaporator in organic Rankin cycle(ORC),flow boiling heat transfer characteristics of R245fa in a horizontal micro-fin tube were tested.The results show that boiling heat transfer coefficient increases with the increase of mass velocity of R245fa,while it decreases with the increase of saturation temperature and heat flux density.With the increase of vapor quality,boiling heat transfer coefficient reaches the maximum at a critical vapor quality.The critical vapor quality is about 0.4,and it is varied according to the operating conditions.When vapor quality is larger than the critical value,heat transfer coefficient can be promoted more remarkably at higher mass velocity or lower saturation temperature.Among the four widely used correlations,KANDLIKAR correlation has high forecast accuracy,the deviation between the forecast value and 91.6%of experimental values is within±25%,and the absolute mean deviation is 11.2%.The correlation is more precise to predict boiling heat transfer coefficients,and it can be used for the design of evaporator in ORC.