In freeze drying, thermal radiation has a significant effect on the drying process of vials located near the corner and edge of the trays, resulting in non-uniformity of the products. Understanding and being able to predict the impact of thermal radiation are therefore critical to accurate determination of the drying process endpoint given the variation in heat transfer of each vial. This article presents a new mechanistic model that describes complex thermal radiation during primary drying in conventional, microwave-assisted, and hybrid freeze drying. Modeling of thermal radiation employs the diffuse gray surface model and radiation network approach, which systematically and accurately incorporates simultaneous radiation exchange between every surface including the chamber wall and vials, allowing the framework to be seamlessly applied for analyzing various freeze-dryer designs. Model validation with data from the literature shows accurate prediction of the drying times for all vials, including inner, edge, and corner vials. The validated model is demonstrated for thermal radiation analysis and parametric studies to guide the design and optimization of freeze dryers.

翻译：在冷冻干燥过程中，热辐射对位于托盘边角区域的小瓶干燥过程具有显著影响，导致产品非均匀性。因此，理解并预测热辐射的影响，对于在每瓶传热变化的情况下准确确定干燥过程终点至关重要。本文提出了一种新型机理模型，用于描述传统、微波辅助及混合冷冻干燥初次干燥阶段的复杂热辐射过程。热辐射建模采用漫灰表面模型与辐射网络方法，系统且精确地整合了包括腔壁与小瓶在内的所有表面间的同步辐射交换，使该框架可无缝应用于分析不同冷冻干燥器设计。利用文献数据进行的模型验证表明，该模型能够准确预测所有小瓶（包括内侧、边缘及角落小瓶）的干燥时间。经验证的模型被用于热辐射分析与参数研究，以指导冷冻干燥器的设计与优化。