矩形通道内过冷流动沸腾传热特性试验研究

Experiments on Subcooled Flow Boiling Heat Transfer in a Rectangular Channel

以高强化发动机缸盖材料蠕铁作为加热块材料,在矩形通道内开展了接近发动机冷却系统的不同流动工况下过冷沸腾传热特性的试验研究。流动工况取发动机常用范围：压力为0.10-0.25MPa,主流温度为60-95℃,流速为0.347-6m/s。研究结果表明：提高冷却液流速可以强化壁面对流换热强度,但是存在沸腾换热的低流速工况同样能够达到高流速工况下换热效果,系统压力和主流温度都会影响冷却液过冷度,进而影响沸腾传热效果。可视化结果表明：气泡直径增大、生长频率升高及气泡之间相互作用都会使气泡对边界层流体扰动增强,从而提高传热效率。在压力为0.2MPa、主流温度为95℃、流速为1m/s工况下,在壁温达到170℃以上时沸腾开始出现,在壁温达到210℃时,沸腾传热效率比单相对流换热提高了40%以上。

Experiments on subcooled boiling flow in rectangular channel under different flow conditions of a similar engine cooling systerm were conducted, using heating block with VGCI as the high-reinforced engine cylinder head material. The flow conditions were within the engine＇s common operating range. Which should be related to the pressure from 0.1 MPa to 0. 25 MPa, the temperature from 60 ℃ to 95 ℃, and the flow velocity from 0. 347 m/s to 6 m/s. The results shows that the improved coolant flow rate can enhance convection heat transfer, but low velocity boiling heat transfer can achieve the same effect of high velocity heat transfer. Because system pressure and main stream temperature will affect coolant subcooling, thereby affecting the boiling heat transfer. The visualization results shows that., increasing the bubble diameter, the growth frequency, and the interaction between the bubbles will cause the boundary layer flow disturbances to increase, so as to enhance the heat transfer efficiency. At the pressure of 0.2 MPa, main stream temperature of 95℃ and flow velocity of 1 m/s, the boiling occurs when the wall temperature reaches 170 ℃above. When the wall temperature is 210 ℃, the boiling heat transfer efficiency will increase by more than 40% as compared to that of single-phase flow.