复合填料热传导过程数值模拟

Numerical Simulation of Heat Conduction in Composite Backfill

复合填料由废铸砂、粉煤灰、聚苯乙烯(EPS)颗粒、水泥和水按一定质量比例混合制成,具有低导热性、抗冻胀和轻质特性。根据热阻力法则和比等效导热系数相等法则,将材料视为由大量正方形单元体组成,其中心为一个球形EPS颗粒,这种单元体与总体的导热系数相等。运用AN SY S软件对复合填料单元体的传热过程进行了有限元模拟,根据瞬态法导热系数测试原理,推求不同EPS掺入比情况下的复合填料导热系数,分析EPS颗粒与导热系数的关系,发现材料导热系数随着EPS掺入比的增加而快速降低。将材料导热系数数值模拟与实测结果作比较,发现有限元模拟值与实测值接近,说明采用有限元方法可以实现对材料传热过程的模拟。

A composite backfill is described in this study, which is composed of waste foundry sand, fly ash, expanded polystyrene （EPS） bead, cement and water in designated proportions, and takes the advan- tage of low thermal conductivity, frost resistance and light weight. Based on the thermal resistance law and the law of ratio effective thermal conductivity, a simplified model was established, which treats the composite matrix as numerous heat transfer cubic elements which are physically contacted to transfer heat. A spherical EPS bead is centered in an element, which is surrounded by cemented earth material. Finite el- ement （FE） analysis was conducted to simulate the heat transfer taken place through the element, and to estimate the thermal conductivity of the backfill by using ANSYS software package. It is indicated that the thermal conductivity of the backfill decreases with the increase of EPS content. The test results were well simulated by the FE results.