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首页> 外文期刊>International Journal of Multiphase Flow >Flow boiling heat transfer characteristics of R123 and R134a in a micro-channel
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Flow boiling heat transfer characteristics of R123 and R134a in a micro-channel

机译：R123和R134a在微通道中的沸腾传热特性

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摘要

Flow boiling heat transfer in a single circular micro-channel of 0.19 mm ID has been experimentally investigated with R123 and R134a for various experimental conditions: heat fluxes (10, 15, 20 kW/m(2)), mass velocities (314, 392, 470 kg/m(2) S), vapor qualities (0.2-0.85) and different saturation pressures (158. 208 kPa for R123; 900, 1100 kPa for R134a). The heat transfer trends between R123 and R134a are clearly distinguished. Whether nucleate boiling is suppressed at low vapor quality or not determines the heat transfer trend and mechanism in the flow boiling of micro-channels. High convective heat transfer coefficients in the two-phase flow of micro-channels enables nucleate boiling to be suppressed even at low vapor quality, depending on the wall superheat requirement for nucleate boiling. In the case of early suppression of nucleate boiling, specifically RI 23, heat transfer is dominated by evaporation of thin liquid films around elongated bubbles. In the contrary case, namely R134a, nucleate boiling is dominant heat transfer mechanism until its suppression at high vapor quality and then two-phase forced convection heat transfer becomes dominant. It is similar to the heat transfer characteristic of macro-channels except the enhancement of nucleate boiling and the short forced convection region.
机译：已使用R123和R134a在各种实验条件下对R123和R134a的单个圆形微通道中的沸腾传热进行了实验研究，包括各种条件：热通量（10、15、20 kW / m（2）），质量速度（314、392） ，470 kg / m（2）S），蒸汽质量（0.2-0.85）和不同的饱和压力（R123为158. 208 kPa; R134a为900、1100 kPa）。 R123和R134a之间的传热趋势得到明显区分。在低蒸汽质量下是否抑制核沸腾，决定了微通道流沸腾的传热趋势和机理。在微通道两相流中的高对流传热系数使得即使在低蒸汽质量下也可以抑制成核沸腾，具体取决于成核沸腾的壁过热要求。在早期抑制核沸腾，特别是RI 23的情况下，传热主要由细长气泡周围的液态薄膜蒸发所决定。在相反的情况下，即R134a，成核沸腾是主要的传热机制，直到在高蒸气质量下抑制它，然后两相强制对流换热才成为主导。它与大通道的传热特性相似，除了增加了核沸腾作用和较短的强制对流区域。

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