纸浆模塑饭盒真空状态下传热传质的数值模拟

Simulation of the vacuum drying process of the pulp-molded products

针对缺少纸浆模塑制品在真空条件下的干燥的数值模拟相关资料的情况下,本文建立了描述其干燥过程传热传质特性的数学模型并进行了有限元计算。计算结果表明,在本文假设前提下,±10℃温度差对纸浆模塑制品加热干燥过程的影响较小;在真空度为0.03～0.04MPa时,纸浆模塑制品的干燥时间能够满足工艺周期要求;随着真空度的降低,干燥时间急剧增加。计算结果符合薄物料热传导干燥的变化趋势,物理意义明确,且与实测值基本相符。该模拟分析可以清晰地反映出温度、真空度对干燥过程进行的不同影响。

In this paper, FEA method is used to solve the mathematic model, which describes the heat and mass transfer in vacuum drying process of pulp-molding products. We use the domain decomposition technique and moving-grids to track the vaporing interface continuously. It's assumed that the pulp product meets the demand of quality and is heated up to critical temperature. The computed results shows: ±10℃ difference in temperature has little effect on the pulp-molded drying; the drying time will meet the technical requirement at 0.03～0.04MPa; when pressure rises, the drying time will rapidly increase. We compare the computed and measured values and find the computed results basically agree with the measured ones. The varying trend of the drying curves accords with that of the thin material when it dries by heat conduction. We also draw up several drying curves in different pressure. From the analog computation, it's known that vacuum is a main factor that influences the drying process.