Experimental investigation of flow boiling of R134a in a vertical multi-corrugated plate heat exchanger
The flow boiling of R134a in a vertical multi-corrugated plate heat exchanger was investigated experimentally.The transition of two-phase flow pattern was captured and analyzed by a high-speed camera,meanwhile the effects of dryness on heat transfer coefficient and pressure drop were analyzed.The results show that the vapor and liquid phase show an interval distribution along the horizontal direction.With the increase of dryness,a relatively stagnant liquid film region is observed in the upper-left corner of the test section,and its area expands with the increase of dryness,and the heat transfer mechanism gradually changes from nuclear boiling to convective boiling.Under the low dryness(x<0.4),the heat transfer coefficient increases slowly with the increase of dryness,then it rises rapidly(0.4<x<0.6)to the peak value(x=0.6),and decreases rapidly due to local dry-out at the high dryness(x>0.7).The friction pressure drop increases with the dryness at the same mass flux.However,the rise of saturation pressure can lead to a lower pressure drop,and the maximum decrease is 20.4%.
plate heat exchangerflow boilingflow patternheat transfer characteristic
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