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首页> 外文期刊>International Journal of Refrigeration >CO_2 flow condensation heat transfer and pressure drop in multi-port microchannels at low temperatures
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CO_2 flow condensation heat transfer and pressure drop in multi-port microchannels at low temperatures

机译：低温下多端口微通道中的CO_2流动凝结传热和压降

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摘要

CO_2 flow condensation heat transfer coefficients and pressure drop are investigated for 0.89 mm microchannels at horizontal flow conditions. They were measured at saturation temperatures of -15 and -25℃, mass fluxes from 200 to 800 kgm~(-2)s~(-1), and wall sub-cooling temperatures from 2 to 4℃. Flow patterns for experimental conditions were predicted by two flow pattern maps, and it could be predicted that annular flow patterns could exist in most of flow conditions except low mass flux and low vapor quality conditions. Measured heat transfer coefficients increased with the increase of mass fluxes and vapor qualities, whereas they were almost independent of wall subcooling temperature changes. Several correlations could predict heat transfer coefficients within acceptable error range, and from this comparison, it could be inferred that the flow condensation mechanism in 0.89 mm channels should be similar to that in large tubes. CO_2 two-phase pressure drop, measured in adiabatic conditions, increased with the increase of mass flux and vapor quality, and it decreased with the increase of saturation temperature. By comparing measured pressure drop with calculated values, it was shown that several correlations could predict the measured values relatively well.
机译：研究了水平流动条件下0.89 mm微通道的CO_2流动冷凝传热系数和压降。在饱和温度-15和-25℃，质量通量从200到800 kgm〜（-2）s〜（-1）和壁过冷温度从2到4℃进行测量。通过两个流型图预测了实验条件下的流型，并且可以预测到，除了低质量通量和低蒸气质量条件外，环形流型可能存在于大多数流动条件下。测得的传热系数随着质量通量和蒸汽质量的增加而增加，而它们几乎与壁冷温度的变化无关。几种相关性可以预测传热系数在可接受的误差范围内，并且从该比较中可以推断出，0.89 mm通道中的冷凝水机制应与大型管中的相似。在绝热条件下测得的CO_2两相压降随质量通量和蒸气质量的增加而增加，随饱和温度的升高而减小。通过将测得的压降与计算值进行比较，表明几种相关性可以较好地预测测得的值。

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