三维双侧强化管内R410a蒸发工程模型研究

Research on engineering model for evaporation of R410a within three-dimensional doubly-reinforced tubes

为评估不同三维双侧强化管蒸发传热特性,采用实验方法对R410a在强化管内的蒸发传热特性进行了测试,并将结果与光滑管进行了比较。所采用的管型包括光滑管、人字纹管、螺旋纹管、人字/涟漪纹管、人字/疏水纹管等。R410a蒸发的饱和温度为279.15 K,质量流速为50—200 kg/(m^(2)·s),入口干度为0.2,出口干度为0.8。研究结果表明,对光滑管内蒸发传热系数,Liu和Winterton模型预测精度最高;强化管内蒸发流型均处于波状分层流。人字/疏水纹管的强化传热因子最高,这与增加成核点数量密切相关;人字/涟漪纹管没有带来明显的传热系数提升。人字/疏水纹管、螺旋纹管具有最佳的蒸发综合传热-阻力特性;人字/涟漪纹管综合性能最差,甚至逊于光滑管。已有关联式对强化管蒸发传热的预测值偏差较大,修正后的Kandlikar关联式以及Gungor和Winterton关联式对传热系数的预测偏差在±10%之内。

To assess different three-dimensional doubly-reinforced tubes with regard to their capability for evaporating heat-transfer,an experiment was conducted which tested how R410a evaporated within the tubes,and compared the experimental result with that of smooth tubes.The tubes tested in the experiment include smooth,herringbone,spiral microgrooves,herringbone/dimple and hydrophobic/herringbone tubes.The saturation temperature of R410a was 279.15 K,its mass velocity was 50-200 kg/(m^(2)·s),and its inlet dryness and outlet dryness were 0.2 and 0.8respectively.The research result shows that the models proposed by Liu and Winterton provide the most accurate prediction of the evaporation heat-transfer coefficient of the inside of smooth tubes,the flow patterns within the reinforced tubes all belong to stratified wavy flow.Hydrophobic/herringbone tubes have the highest evaporation heat-transfer coefficient,which is closely related to the additional nucleation points inside the tubes.The coefficient of herringbone/dimple tubes is not remarkably higher than that of smooth tubes.Hydrophobic/herringbone tubes and spiral microgrooves tubes show the best overall capacity for evaporative heat transfer and resistance,herringbone dimple tubes have the worst overall capacity among all the tested tubes,including smooth tubes.When it comes to the capacity of reinforced tubes for heat transfer,the predictions produced by existing correlations are remarkably skewed.Having been corrected,the correlation created by Kandlikar and the correlation proposed by Gungor and Winterton can now give a prediction of heat-transfer coefficients with a deviation rate within±10%.