氦气冲刷螺旋管束传热的数值研究

采用CFD软件对氦气冲刷螺旋管束的传热特性进行了数值模拟。计算时采用了轴对称简化模型;湍流模拟采用低Re k-ε模型。通过与实验数据对比,发现低Re模型比壁面函数法更适合计算冲刷管束类型的流动。计算结果表明,顺排管束前几层平均Nu高于叉排管束,而深层管平均Nu低于叉排管束;管列距离较大时排列方式对深层管的传热影响很小;管束与边界距离约为管束中心部分氦气流道宽度的一半时,各列传热管传热和氦气出口温度都较为均匀;管束横向位置发生偏移将导致管束内流动、传热出现不均匀。结果对于螺旋管蒸汽发生器设计具有参考意义。

Numerical analysis of heat transfer characteristics of helium flow cross helically coiled tube bundle

The convective heat transfer process of helium flow cross helically coiled tube bundle was simulated by CFD method.Because of the small helical angle of the bundle,a simplified 2-D axisymmetric model was adopted during calculation,which has saved computer memory and CPU time dramatically.The turbulence was simulated by a low Re k-ε model which can get relatively good result in the simulation of cross flow problems in comparing with wall-function treatment.The numerical results show that the average Nu number of the first several tubes in inline arrangement is bigger than that in staggered arrangement,while the average Nu of the inner tubes in inline arrangement is smaller than that in staggered arrangement.However,for large transverse distance the difference of Nu between the two arrangements is small.The optimum distance between the bundle and the bundle wall may be about half the transverse distance of two adjacent inner tube rows,which results in both uniform helium temperature distribution at outlet of the bundle and uniform heat transfer rate of the tube in different rows.It is also found that the departure of tube row from original position will cause ununiformity of heat transfer in different tube rows.The results obtained can be used in the design of helically coiled tube type steam generator and heat exchanger.