罗小平, 邓聪, 冯振飞, 周建阳. 制冷系统不同表面能微通道的流动沸腾传热特性试验[J]. 农业工程学报, 2016, 32(20): 217-222. DOI: 10.11975/j.issn.1002-6819.2016.20.028
    引用本文: 罗小平, 邓聪, 冯振飞, 周建阳. 制冷系统不同表面能微通道的流动沸腾传热特性试验[J]. 农业工程学报, 2016, 32(20): 217-222. DOI: 10.11975/j.issn.1002-6819.2016.20.028
    Luo Xiaoping, Deng Cong, Feng Zhenfei, Zhou Jianyang. Flowing boiling heat transfer characteristics test for microchannels with different surface energy in refrigeration system[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(20): 217-222. DOI: 10.11975/j.issn.1002-6819.2016.20.028
    Citation: Luo Xiaoping, Deng Cong, Feng Zhenfei, Zhou Jianyang. Flowing boiling heat transfer characteristics test for microchannels with different surface energy in refrigeration system[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(20): 217-222. DOI: 10.11975/j.issn.1002-6819.2016.20.028

    制冷系统不同表面能微通道的流动沸腾传热特性试验

    Flowing boiling heat transfer characteristics test for microchannels with different surface energy in refrigeration system

    • 摘要: 为了研究微通道壁面特性对流动沸腾传热的影响,该文以具有不同表面能的微通道为研究对象,制冷剂R141b为试验工质,在不同热流密度、质量流率下对微通道内的沸腾传热特性进行了试验探究。结果表明:在该试验工况下,质量流率的增加有利于沸腾传热,但微通道内过冷段长度也相应增加;在微通道饱和沸腾区传热系数较稳定,但沿工质流动方向有缓慢降低的趋势;相比于表面能为23.93 mN/m的3#的微通道,表面能为60.03和49.54 mN/m的1#和2#微通道沸腾传热系数分别提高18.42%和9.28%;根据试验值与关联式预测值的对比情况,对Lazarek关联式进行修正,拟合得到能很好预测该试验各工况下的传热关联式,平均绝对误差为9.76%。该研究为微通道换热器的设计提供了参考。

       

      Abstract: Abstract: With the development of many applications in modern industrial system and equipment, the ability to dissipate a large amount of heat from small surface area has been becoming increasingly urgent. Flow boiling in microchannels provides unique advantages when applied in micro-module equipment. Therefore, the microchannel heat exchangers have a broad industrial and market prospects for their high heat transfer coefficients and appreciable reduction in weight and volume. Flow boiling heat transfer in microchannels becomes one of popular researching hot spots. But the researches about flow boiling in microchannels with different surface energy are still lacked and further researches are needed. In this study, the current experiments fabricated 3 different modules with the identical sizes of 240 mm × 400 mm × 7.5 mm and with the different surface energy. Flow boiling experiments were conducted with the refrigerant R141b in a test module containing 22 microchannels which were 2 mm wide and 1 mm deep. During the experiments, the heat flux imposed on the aluminum substrate varied from 9 to 26 kW/m2 and the mass flux flowing into the channel varied from 50 to 583 kg/(m2·s). The effects of the microchannels with different energy on boiling heat transfer under a certain pressure were experimentally investigated with different heat flux and mass flux. The results showed that the thermodynamic equilibrium quality increased fairly linearly with axial variation, with the slope inversely proportional to mass flow rate. The two-phase boiling heat transfer came earlier when mass flow rate was smaller and the increase of mass flow rate was beneficial to boiling heat transfer, but leading to the increasing of the length of the subcooled region. Heat transfer coefficient was relatively stable in the saturated boiling region of the microchannels and had a tendency to decrease along the flow direction due to the rise of gas phase proportion. Compared to the microchannels with the surface energy of 84.16 mN/m, the heat transfer coefficient of the microchannels with the surface energy of 21.12 and 62.99 mN/m increased by 18.42% and 9.28%, respectively. The augment of surface energy of microchannels was attributed to the boiling heat transfer coefficient. One reason was that the microchannels with higher surface energy had better wettability, which increased the liquid layer thickness and promoted dry patch rewetting, thus avoiding local dryout at heat transfer surface. Another was that there was more active nucleation in the microchannels with high surface energy, which made bubbles coalesce laterally during the growth phase before they departed from the surface. Three popular correlations were compared, and the correlation of Lazarek showed the best predictive capability with the mean absolute error (MAE) of 21.2%. In order to further improve the accuracy, the Jacobi number and thermodynamic equilibrium quality were introduced. The new correlation based on the correlation of Lazarek was obtained by fitting, which showed good predictions and was evidenced by an overall MAE of 9.76%. This research is beneficial to the parameter optimization of the predictive tool of the two-phase heat transfer coefficient and also provides the reference for the design of the microchannel heat exchangers.

       

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