冷冻干燥过程中非定常传热传质研究

本文对制品在两端同时受热条件下的冷冻干燥过程的非定常传热传质进行了研究,建立了冻结层和多孔干燥层的传输过程的数学模型,讨论了干燥箱内的流动及传热,通过热量和质量传递之间的相互耦合求得升华界面温度的变化以及干燥速率。

Unsteady Heat and Mass Transfer in the Freeze-Drying Process

The primary drying characteristics of a product in the freeze-drying process by back-face heating is investigated theoretically. Based on unsteady heat and mass transfer in freeze-drying, taking into account the fact that the heat will transfer both through the frozen layer to the sublimation front and through the porous dried layer by radiation, a mathematical model for the heat and mass transfer in the product is dresented. Flow and heat transfers in the chamber are analyzed and correlated to the transport process in the product. The temperature at the sublimation front and the drying rate are calculated.The effects of the thickness of the product, the temperature at the bottom of the product, and the condenser temperature on the drying times and some characteristics in the sublimation process are discussed. Unsteady models are compared with the quasi-steady ones and some practical results are given.