等壁温加热微通道内气体流动换热特性的直接蒙特卡罗模拟

用直接模拟蒙特卡罗方法对压力边界条件下气体在微通道内的流动换热特性进行了研究,给出了壁面与来流存在温差时的沿程速度分布特点,以及在可压缩性与换热条件综合作用下的温度分布特点。研究结果表明:微通道内气体可压缩性作用显著,温度分布由可压缩性和换热强度的相对强弱综合决定;壁面与来流存在温差时气体沿程速度分布型线在入口段内上凸;壁温高于来流温度时,气流速度与等温流动工况下的速度的相对大小与气体稀薄性有关。

Simulation of constant wall-temperature heat transfer in microchannel by Direct Simulation Monte Carlo Method

Pressure-driven gaseous flow in microchannel under constant wall-temperature boundary condition was simulated with Direct Simulation Monte Carlo(DSMC) method.The velocity and temperature distributions were presented for different wall temperatures and different ratios of microchannel length to height.The simulation results show that: Compressibility plays an important role on the temperature distributions and the actual temperature distributions are affected by both compressibility and heat transfer condition.The streamwise distribution of gas temperature may decrease when the gas is heated by the wall due to significant compressibility in short microchannel.When the gas is heated by wall,the pressure gradient increases and the profile of streamwise velocity becomes raised near the channel entrance.The cross-sectional averaged velocity decreases in the case of Kn=0.055 and increases in another case of Kn=0.88.The variation of friction factor with the wall temperature is distinct when gas flows in slip and transition regions.