单侧周期性温度边界下多孔介质方腔内自然对流传热数值模拟

Numerical stimulation of natural convection in a square cavity filled porous medium under periodical thermal boundary condition

采用局部非热平衡模型,在方腔左侧壁面温度正弦波变化的边界条件下,应用SIMPLER算法数值模拟研究了固体骨架发热多孔介质方腔内的稳态非达西自然对流,主要探讨了不同正弦波波动参数N、振幅A及方腔的高宽比M/L对方腔内自然对流与传热的影响规律。计算结果表明:方腔左侧壁面附近出现了周期性的正负变化的温度场分布,壁面局部传热系数出现了周期性的震荡现象;存在一个最佳温度波动参数N=3,此时流体相壁面的平均Nu达到最大值;存在一个最佳的方腔高宽比M/L=0!1,使得多孔介质方腔内自然对流传热效果最好,增加或减小高宽比都会在一定程度上削弱多孔介质方腔内的传热效果;相对于温度均一的边界条件,正弦波温度边界条件能够增大壁面的平均Nu数,起到强化传热的作用。

Steady non-Darcian natural convection in a square cavity filled with a heat-generating porous medium is numerically studied in the spatial coordinates by using the local non-thermal equilibrium model and SIMPLER algorithm. The other walls of the cavity are adiabatic except the left wall,which is partially heated and cooled by sinusoidal temperature profile. The influences of the fluctuant parameter N,the amplitude A of sine wave and the height to width ratio of the square cavity on the natural convection law are discussed. The results show that,the temperature field and the local Nusselt number near the left wall vary periodically because of the sinusoidal boundary condition. There is an optimal value of temperature fluctuant parameter N = 3,which makes the heat transfer rate of fluid phase in the square cavity maximum. Also there is an optimal height-to-width ratio of the square cavity in 0 ~ 1,which makes the natural convection effect in a square cavity the best,and smaller or greater height-to-width ratio makes the natural convection effect worse. Compared with uniform temperature boundary,sinusoidal temperature boundary can increase the average Nusselt number of wall to enhance heat transfer effect.