粉煤灰传热的影响研究

Research on the heat transfer effects of fly ash

近年来国内外竞相开展利用粉煤灰等制各保温材料的研发工作，以粉煤灰传热为研究对象，对粉煤灰内的流场、温度场、高温壁面平均努谢尔数Nu进行研究；采用整场求解法方法进行数值求解，对网格的独立性和计算过程进行了验证；得到了粉煤灰传热一些基本数据，分析了粉煤灰温度场和流场随瑞利数Rα的变化规律。研究结果表明：随着Rα增加，开始流线均匀分布为一个顺时针大窝，逐渐变化为流线集中分布在流场外侧，而在中央基本上保持静止状态；当Rα很小时，无量纲等值线近似于平行高低温壁面的垂直线，随着Rα数逐渐增大，对应的温度等值线近似呈高温至低温的线性变化趋势；Rα小于10^5时，高温壁面Nu基本为2．37～3-31的定值；高温壁面底部努谢尔数Nu数大，最大值为30．8，上部Nu数小，最小值为1．19。

In recent years, researches and development works on making thermal insulation material with fly ash and others are competitively launched at home and abroad. Heat transfer of fly ash is the object of study. The flow field, temperature field and average Nusselt numbers Nuu of the high temperature wall surface in the fly ash are studied. Numerical solution is carded out using whole field solving method. The grid independence and computation process are verified. Some basic data is obtained and the change of temperature field and flow field of fly ash with Rayleigh number Ra is analyzed. The results of the study show that： with the increase of Ra, at first the flow lines are uniformly distributed as a clockwise big nest, gradually the flow lines are concentrated in the outer side of the flow field, while in the centre they remain mainly stationary state; When Ra is very small, non-dimensional contours approximately parallel the vertical line of wall surface of the high and low temperature, with the gradually increase of Ra, the corresponding temperature contours approximately forms as the linear trend of the high temperature to the low temperature; When Ra is less than 105, Nu of the high temperature wall surface is a constant value of 2.37 to 3.31; Nu of the bottom of high temperature wall surface is large, the maximum value is 30.8, Nu of the upper part is small, the minimum value is 1.19.