Flow boiling heat transfer characteristics of R513A in horizontal tube
In order to study the flow boiling heat transfer characteristics of R513A in horizontal tube,the effects of mass flux,saturation temperature and vapor quality(heat flux)on heat transfer coefficient were analyzed,in the working conditions range of mass flux of 100-200 kg/(m2·s),saturation temperature of 5-10℃,heat flux of 0-56 kW/m2 and vapor quality of 0-1.The results show that the flow boiling heat transfer coefficient increases and then decreases with the increase of the vapor quality.When the liquid film on the tube wall is flushed by the vapor,"ring-drying flow"is occurred in the stage of annular flow,the emergence of the local drying causes the flow boiling heat transfer coefficient to decrease.When the mass flux and the flow boiling heat transfer coefficient become higher,the critical dryness of the dryout decreases.This is mainly due to the scouring effect of the gas.However,the critical dryness increases with the increase of the mass flux in the microfin tube with an external diameter of 9.52 mm.Comparing the prediction results between four empirical models,the Gungor-Winterton model has the highest prediction accuracy with a mean absolute error of 13.92%before the onset of drying,and the Jung model has the highest prediction accuracy with a mean absolute error of 2.56%after the onset of drying.
boiling in tubeR513Amicrofin tubeheat transfer coefficient
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