均流腔结构对微细通道内相变流动特性影响的实验研究

Experimental study on the effect of flow sharing cavity structure on phase change flow characteristics in microchannels

以R134a制冷剂为工质,在质量流率为416~728 kg/(m^(2)·s),基面热通量为36.7~242.6 kW/m^(2)条件下,研究了方形均流腔和圆弧均流腔微细通道换热器内两相流型的变化规律以及不同条件下微通道的压降特性、压力波动特性与传热特性。结果表明:两种均流腔结构的微通道内流型过渡是相似的,在弹状流型时均观察到了流动逆转现象;相比于方形均流腔微通道,圆弧均流腔微通道的压降更低,压力波动幅度更小,且具有更高的传热系数。在热通量为242.6 kW/m^(2),质量流率为416 kg/(m^(2)·s)条件下,压降降低了51%;在热通量为154.4 kW/m^(2),质量流率为416 kg/(m^(2)·s)时,出口压力波动幅度降低了35%;当热通量为242.6 kW/m^(2),质量流率为728 kg/(m^(2)·s)时,微细流道末端的传热系数提高了9.7%。

In order to make the heat dissipation system run more safely and reliably,and improve the instability and heat transfer performance of two-phase flow and heat transfer in microchannels,R134a refrigerant is used as the working fluid,and the boiling flow characteristics of microchannels with square flow sharing cavity and microchannels with circular-arc flow sharing cavity are compared.The experiment was carried out in 9 parallel microchannels arrays,with a base area of 136 mm^(2) and a hydraulic diameter of 400μm.Under the conditions of mass flow rate of 416—728 kg/(m^(2)·s)and base heat flux of 36.7—242.6 kW/m^(2),the variation of two-phase flow pattern in the microchannels was studied by experiment and simulation,and the pressure drop,pressure fluctuation and heat transfer characteristics of microchannels under different conditions were studied by experiment.The results show that the simulation results are in good agreement with the experimental results.The flow patterns in the microchannels of the two kinds of flow sharing cavities are similar,and the flow reversal phenomenon is observed in the slug flow pattern.Compared with the square flow sharing cavity microchannels,the circular-arc microchannels have lower pressure drop,smaller pressure fluctuation and higher heat transfer coefficient.When the heat flux density is 242.6 kW/m^(2) and the mass flux density is 416 kg/(m^(2)·s),the pressure drop is reduced by 51%.When the heat flux is 154.4 kW/m^(2) and the mass flux is 416 kg/(m^(2)·s),the fluctuation of outlet pressure decreases by 35%.When the heat flux is 242.6 kW/m^(2) and the mass flow rate is 728 kg/(m^(2)·s),the corresponding heat transfer coefficient is increased by 9.7%.