Experimental on the flow boiling heat transfer characteristics of R513A insides horizontal tubes with different thread structures
Global warming is becoming increasingly serious,new environmentally friendly refrigerant research is imminent.The refrigeration industry also needs to replace existing refrigerants and further enhance the heat transfer efficiency of heat exchangers.Experimental research on the flow boiling heat transfer of R513A in different structures of tubes was conducted to explore the mechanism of different enhanced structures,mass flow rates[300-500kg/(m2·s)],and evaporating temperatures(5-10℃)on the heat transfer coefficient and pressure drop.The results showed that the heat transfer coefficient of R513A in microfin tubes was 23％-120％higher than that in smooth tube,while the pressure drop was higher than that in smooth tube.Larger helix angles exacerbated the generation of secondary flow in the tube;a larger number of teeth can increase the effective heat transfer area of boiling heat transfer,enhancing heat transfer.The boiling heat transfer coefficient and pressure drop of R513A increased with increasing mass flow rate;as the evaporating temperature rose,the heat transfer coefficient increased while the pressure drop decreased.By comparing the unit pressure drop heat transfer coefficient,it can be concluded that the 4# microfin tube had the best heat transfer performance.The differences in thread parameters mainly affected the comprehensive performance of microfin tubes in the low and medium vapor quality,with less impact in the high vapor quality.Under the present experimental conditions,the Kaew-on correlation and Chisholm correlation had the highest accuracy in predicting the heat transfer coefficient and pressure drop inside the smooth tube for R513A,with a mean relative error of-4.74％and 7％,respectively;and the Yu correlation and Miller-Steinhagen correlation were better in predicting the heat transfer coefficient and pressure drop inside the microfin tube,with a mean relative error of 14.16％and 3.66％,respectively.
enhanced structureflow boilingR513Acoefficient of heat transferpressure dropcorrelation
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