MODELING OF NATURAL CONVECTION AT MELTING IN THE THERMAL ENERGY STORAGE MODULE WITH PHASE CHANGE «SOLID BODY - LIQUID»

• Видавець: Institute of Renewable Energy National Academy of Sciences of Ukraine
• Дата: 2023
• Автори: Yurkov, R., Knysh, L.
• Формат: Стаття
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2023
• Теми: thermal storage module; phase change “solid body – liquid”; mathematical model; effective heat capacity method; natural convection; numerical investigation.; тепловий акумулятор; фазовий перехід «тверде тіло – рідина»; математична модель; метод ефективної теплоємності; вільна конвекція; числове дослідження
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/379

Modeling results of heat exchange processes in a cylindrical element of the thermal storage module with phase change “solid body – liquid” are presented. The vertical cylindrical element has design “double pipe” which is filled the phase change material NaNO3. Chanel with heat transfer fluid is located inner the phase change material. As heat transfer fluid is used Sylthem800, which is the typical for parabolic trough collectors. Developed mathematical model is corresponded Stefan problem when latent heat is taken into account by effective heat capacity method. Influence of natural convection at melting of the phase change material is modeled using effective heat transfer coefficient which is calculated based on criteria equations. The numerical algorithm and in-house Python-code is created for finding of the temperature distributions in phase change material. These temperatures depend on time and heat transfer fluid flow regime. It is found that natural convection at laminar regime influence on the heat transfer in system significantly. Influence of the natural convection is decreased at transfer to turbulent regime. It is connected with intensification of forced convective heat and mass exchange in channel with heat transfer fluid. Velocity of moving for the phase boundary is determined at laminar and turbulent heat transfer flow regime.  This velocity is calculated with account of natural convection at melting and without one. Obtained data will be useful for choose of geometric, dynamic and thermophysical parameters of prospect thermal storage modules with phase chance “solid body – liquid”.