封闭圆内开缝圆自然对流换热的振荡特性

本文通过数值计算探讨了封闭圆内开缝圆自然对流换热的振荡特性。数值计算以整个圆为计算区域,采用了非稳态的数学模型和具有QUICK差分格式的SIMPLE算法。在相同条件下计算结果和实验结果符合很好。数值结果显示, 当几何结构一定时,Rayleigh数Ra小于某个临界值时,流动和换热处于稳态,并且关于垂直中心线对称;Ra大于这个临界值时,流动和换热是振荡的,非对称的。数值实验还表明,流动和换热出现振荡时的临界Rayleigh数Rac与开缝圆的开缝度有关,且流动和换热的振荡会出现对称振荡和非对称振荡两种情形。

OSCILLATION OF NATURAL CONVECTION IN A CYLIN DRICAL ENCLOSURE WITH AN INTERNAL CONCENTRIC SLOTTED CYLINDER

The oscillation phenomena of natural convection in a cylindrical enclosure with an internal concentric slotted cylinder are investigated by numerical computations using SIMPLE algorithm with QUICK scheme. The whole enclosure is taken as the solution domain and an unsteady mathematical model is adopted for the numerical computations. The numerical results of average dimensionless equivalent conduction coefficient Keq obtained in this paper agree well with previous experimental results. It can be found that oscillatory natural convections can be obtained when Rayleigh number is over a critical value for a certain geometric configuration. The flow and heat transfer are steady and symmetrical about the vertical line when Rayleigh number is less than the critical value, and are unsteady and unsymmetrical when Rayleigh number is greater than the critical value. It is also found that the critical Rayleigh number Rac changes with slot widths, and there exists symmetrical and unsymmetrical oscillation for the oscillatory flow and heat transfer.