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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 6时半径比的影响可忽略
The effect of variable properties on the natural convection heat transfer in concentric casing cascades was investigated. Ra was found to be 1.06, and the temperature difference θ0 = (Th-Tc) / Tc was 0.2, 0.5, 0 and 2.0, the radius ratio is from 1.50, 2.28, 3.33 to 5.0 0, the mass average temperature Tm is taken as the reference temperature, the distribution of velocity field and temperature field are obtained.With different radius ratios, Get the heat transfer correlation Nu-Ra in the form of convection heat transfer zone: Keq = C × Ran (0 .2 ≤ θ0 ≤ 2.0, 4.5 × 10 3 ≤ Ra ≤ 2.5 × 10 5) The values of C and exponent n depend on the radius ratio, but the effect of radius ratio is negligible when κ> 2.0, 4 × 10 3 ≤ Ra ≤ 2.0 × 10 6