CO2 flow condensation heat transfer and pressure drop in multi-port microchannels at low temperatures
CO2 flow condensation heat transfer and pressure drop in multi-port microchannels at low temperatures
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DOI：
10.1016/j.ijrefrig.2009.01.030
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发表时间：
2009-09
期刊：
影响因子：
--
通讯作者：
C. Park;P. Hrnjak
中科院分区：
文献类型：
--
作者：
C. Park;P. Hrnjak
研究了水平流动条件下0.89mm微通道内CO2流动的凝结换热系数和压降。它们是在饱和温度为−15和−25°C，质量通量为200至800 kgm −2s−1，壁面过冷温度为2至4°C的条件下测量的。根据两种流型图对实验工况下的流型进行了预测，除低质量流量和低干度工况外，大多数工况下均能出现环状流型。实验测得的换热系数随质量流量和蒸汽干度的增加而增加，但几乎不受壁面过冷度变化的影响。几个关联式可以在允许的误差范围内预测换热系数，并从这一比较可以推断，在0.89mm通道中的流动凝结机制应该类似于大的管。绝热条件下CO2两相压降随质量流量和干度的增大而增大，随饱和温度的升高而减小。通过比较压降的测量值与计算值，表明几个关联式可以较好地预测测量值。
CO2flow condensation heat transfer coefficients and pressure drop are investigated for 0.89mm microchannels at horizontal flow conditions. They were measured at saturation temperatures of −15 and −25°C, mass fluxes from 200 to 800kgm−2s−1, and wall subcooling temperatures from 2 to 4°C. 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 0.89mm channels should be similar to that in large tubes. CO2two-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.