Abstract <p>In modern industrial processes for the treatment of chemical and petrochemical feedstocks, it is often necessary to operate under vacuum. One of the key stages in such processes is the condensation of vapor-gas mixtures (VGMs) in vacuum condensers, which enables the recovery of target products and enhances overall production efficiency. This stage is particularly crucial when handling thermally unstable substances, such as ethylene glycols, where maintaining low temperatures is critical to prevent product degradation. The condensation of VGMs under vacuum is complicated by the presence of non-condensable gases, which adversely affect the efficiency of the heat transfer process. This factor requires special attention when selecting a calculation method and designing heat exchange equipment. Existing calculation methodologies used in industrial practice often have limitations and require adaptation to specific operating conditions. This article addresses the problem of vapor-gas mixture condensation under vacuum in the chemical industry. The features of the condensation process in the presence of non-condensable gases (NCGs) and its impact on the performance of vacuum condensers are examined. The main theoretical principles and existing methods for calculating VGM condensation are presented, along with an analysis of both Russian and international literature on the topic. To automate and improve the accuracy of engineering calculations, a program code was developed in Visual Basic for Applications (VBA), integrated with the universal simulation program Aspen HYSYS V12. The results of practical calculations based on the application of various methods and specialized software packages are presented. The study revealed significant discrepancies in the results obtained from different calculation methods, highlighting the need for further research and refinement of methods for calculating vapor-gas mixture condensation under vacuum.</p>