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The vacuum drying of cellulose-based insulation is an essential step in the transformer production process which usually consists of both heat and vacuum application. The moisture inside the cellulose insulation during this process is transferred by various transport mechanisms, some of which could be affected by temperature of the insulation as well. Furthermore, the conditions inside the vacuum chamber are generally transient and highly dynamic depending on the process control strategy and could include various types of phenomena such as gas expansion during the pump down process or heat transfer by radiation. Mathematically speaking, the above-mentioned conditions will have influence on the drying rate by altering the boundary conditions of heat and mass transport equations. In this study, a mathematical model that considers the process at both the scale of the cellulose insulation and the scale of the vacuum chamber is presented. By introducing a simplified drying system with two-point process control, a model test case and drying case were simulated. Model results demonstrated that chamber dynamics significantly affect drying behaviour. The proposed model could thus facilitate the estimation of total energy consumption and process duration, offering a valuable tool for optimization of vacuum drying procedures.