变物性对水平同心套管中自然对流换热的影响

Effect of Variable Properties on Natural Convection Heat Transfer in Horizontal Concentric Circular Annulus

研究了变物性对水平同心套管夹层中自然对流换热的影响 .计算时 Ra达到了 1 0 6,温差率θ0 =( Th- Tc) /Tc分别为 0 .2、0 .5、1 .0和 2 .0 ,半径比从 1 .50、2 .2 8、3.33到 5.0 0 .计算时采用质量平均温度 Tm 作为参考温度 ,得到了速度场和温度场的分布 .在不同半径比下 ,得到换热关联式 Nu- Ra在对流换热区的形式 :Keq=C×Ran( 0 .2≤ θ0 ≤ 2 .0 ,4.5× 1 0 3≤Ra≤ 2 .5× 1 0 5) .系数 C和指数n的值取决于半径比 ,但当κ>2 .0 ,4× 1 0 3 ≤ Ra≤ 2 .0× 1 0

The effect of variable properties on natural convection heat transfer in horizontal concentric circular annulus was studied. In numerical simulation the Rayleigh number is as high as 10 6, the temperature difference ratio θ 0=(T h- T c)/ T c are 0.2,0.5,1.0,2.0, and aspect ratio are 1.50,2.28,3.33 and 5.00. The mass weighted mean temperature T m is used as reference temperature in the calculation to solve the distribution of velocity field and temperature field. Under the different aspect ratio the heat transfer correlation of Nu-Ra in the convection dominated region which is in the form of K eq = C×Ra n(0.2≤θ 0≤2.0,4.5×10 3≤Ra≤2.5×10 5 ) is deduced. The value of coefficient C and n depends upon the aspect ratio. However, the influence of aspect ratio can be neglected when κ >2.0,4×10 3≤ Ra ≤2.0×10 6.