Theory Study On Heat And Mass Transfer Process In Transformer Kerosene Vapor Phase Drying System

The kerosene vapor phase drying technology is one of the most important processes during the production and maintenance for large oil-immersed power transformer. Due to large-size transformer, remote operation place, overall transportation difficulties and other factors, the mobile kerosene vapor phase drying equipment for transformer emerges at the right moment. However, the heat and mass transfer mechanism for the kerosene vapor phase drying processes is studied rarely, and the mechanism is nearly blank. But research on this aspect has an important significance and function for the mobile kerosene vapor phase drying technology and development of drying devices.In this paper, quantitative theoretical research and simulation calculation are conducted for the heat and mass transfer mechanism of the mobile kerosene vapor phase drying processes in the aspect of macro and micro.In the aspect of overall system research:Two mathematical models are established. One of them is established aiming at the mobile kerosene vapor phase drying processes and the corresponding phase equations are given, which can reflect the quantitative relationship of process parameters in different stages. So this mathematical model can more intuitively quantitatively describe the mobile kerosene vapor phase drying processes and can be applied to provide theoretical basis for the control of drying technological process. The other mathematical model is established aiming at the mobile kerosene vapor phase drying equipment system, a heat mass transfer mathematical model including 48 mathematical equations, which represents completely thermodynamics laws of phase change and transport process of kerosene, water and air in the mobile kerosene vapor phase drying technological processes, and describes in detail the quantitative relationship among important physical quantities such as temperature, pressure and flux in key equipment units and process. The simulation calculation for the heat mass transfer mathematical model is carried out by MATLAB software, which verifies the correctness and reasonability of the mathematical model established. This mathematical model can has practical application value.In the aspect of micro process research:The microstructure of various transformer insulation papers is observed by the metallographic optical microscope, and the complex capillary inside the insulation papers can be observed clearly. The insulation paper porosity is determined by the infiltration absorption method. The moisture content of insulation paper is determined by the MB45 halogen moisture meter. A vacuum thermal drying test bench is set up, and the microscope system can monitor the migration of kerosene in the insulation paper all the time under vacuum hot condition. This experiment can help us study the heat mass transfer process of transformer insulation paper on the micro scale, which will enrich the content in the field of micro research drying porous medium. A porous media model is established aiming at the drying process of insulation paper. The numerical simulation of drying porous medium is conducted by COMSOL software, which can predict the change rule of the related parameters over time.