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基于Brinkman扩展达西模型,采用直角坐标系下的压力与速度耦合SIMPLE算法,对竖直线热源下松散颗粒的物料传热特性进行了数值模拟.结果表明,竖直线热源作用下的松散颗粒物料中存在明显对流换热效应,且与粒度大小和空隙率无明显相关性.热源表面平均Nusselt数Nuavg随瑞利数Ra增大呈线性增加趋势,而热源表面局部Nusselt数NuR与Ra之间的关系较复杂,但除热源表面顶端位置外,其余位置均可由关联式NuR?a Ra2+b Ra+c表示.为降低对流换热的影响,利用热源表面温升数据测算试样导热系数时(交叉热线法),实验时间不宜超过120 s;而基于平行热线法测热物性参数,温度测点宜布置在试样筒中下部位置处(Y?0.33).利用本模型计算的典型测点温升与实测结果较吻合,而利用热传导模型计算的部分测点温升与实测值最大偏差达17℃,中下部区域则较小.
Based on the Brinkman extended Darcy model, the pressure-velocity coupled SIMPLE algorithm in Cartesian coordinates was used to simulate the heat transfer characteristics of loose particles under the vertical heat source. The results show that the loose particles There is obvious convective heat transfer in the material, and there is no obvious correlation with particle size and void ratio.The average Nusselt number Nuavg of heat source surface increases linearly with increasing Rayleigh number Ra, while the local Nusselt number between heat source NuR and Ra However, except for the location of the top of the heat source surface, the remaining positions can be expressed by the relation NuR? A Ra2 + b Ra + c. In order to reduce the influence of convection heat transfer, when using the heat source surface temperature rise data to calculate the thermal conductivity of the sample (Cross hot-wire method), the test time should not exceed 120 s; and based on the parallel hot-wire method to measure the thermal properties, the temperature measuring point should be arranged in the lower part of the sample tube (Y? 0.33) The results of temperature rise and measured are in good agreement with each other. However, the maximum deviation of the measured temperature rise from the measured value calculated by the heat conduction model reaches 17 ° C, while the middle and lower regions are smaller.