Boundary and Interface Treatments for One-Unit Pore-Scale Simulations of Heat and Mass Transfer in Porous Materials: A Mini-Review

In recent years, extensive pore-scale simulations have been conducted to study the microscopic flow and heat transfer processes in porous materials. In these studies, the calculation is often performed only in a small representative volume, which is called the periodic unit or unit cell. To numerically solve the governing differential equations for flow and thermal distributions in the periodic unit, appropriate boundary conditions are required for the artificial side surfaces of the periodic unit. However, the validity and assumptions behind these boundary treatments have not been examined or discussed. In this article, based on fundamental principles of fluid mechanics and energy/mass conservation, we review and analyze several commonly used methods for the thermal conditions on the periodic unit boundaries and the solid-fluid interfaces. Our analysis and discussions reveal the constraints and assumptions behind these methods and raise concerns on their applications in simulations of porous thermal flows. These examination, analysis and discussions could be valuable, especially for new researchers in computational heat transfer, on selecting appropriate boundary methods in simulations of porous thermal flows. This study can also be helpful for new boundary condition development in heat and fluid flow simulations in periodic structures.

Automated summary

Extensive pore-scale simulations have been conducted to study microscopic flow and heat transfer processes in porous materials. However, the validity and assumptions of the boundary conditions used in these simulations have not been examined or discussed. In this article, various methods for thermal conditions on periodic unit boundaries and solid-fluid interfaces are reviewed and analyzed. The analysis reveals the constraints and assumptions behind these methods and raises concerns about their applications in porous thermal flow simulations. This study is valuable for new researchers in computational heat transfer and can aid in the development of new boundary conditions in heat and fluid flow simulations in periodic structures.