tailieunhanh - Two Phase Flow Phase Change and Numerical Modeling Part 19

Tham khảo tài liệu 'two phase flow phase change and numerical modeling part 19', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 530 Two Phase Flow Phase Change and Numerical Modeling and the material properties involved in equations 1 to 3 are written as follows p p P ps - p pĩ Pl - ps p Pps Pĩ Pi - ps k ks fi kg - ks F - kg cp 9 cp x - PF cpi - . Fig. 4. Temperature dependent smoothed function for modeling properties intermediate between the solid and liquid phases A smoothed piecewise-polynomial profile which is a function of temperature is used due to discontinuities in properties between solid and liquid PCM. This is shown in Fig. 4. Initial and boundary conditions The initial temperature of domain is 300 K and the localized thermal input temperature is 500 K. The conjugated thermal boundary condition is applied between the copper and the solid PCM and the heat balance equation between the PCM and air. The boundary conditions are expressed as follows at X 0 T 300K at interface between the PCM and air dTi dTs _ n . k ks - 0 dn 6 dn 15 at interface between the solid and liquid PCM A sS A S l Ts i at other boundaries 9T n dT n 0 or 0. ch 91 531 A Numerical study on Time-Dependent Melting and Deformation Processes of Phase Change Material PCM Induced by Localized Thermal Input 3. Results and discussion Model validation To validate the model a simple melting problem of gallium in a cavity by the use of Enthalpy-Porosity method was solved and compared with experimental results. Fig. 5 shows the schematic illustration of the physical configuration of gallium melting. Solid gallium occupies the whole domain Th 311 K is heated wall temperature and Tc K is cold wall temperature. The boundaries of the top and bottom surfaces are isothermal walls. The width w cm and the height H cm. Normal gravity is applied in the downward. Details of the applied material properties and information on the experimental setup are described in Brent s work Brent 1988 . Once the calculation is started the solid gallium melts. Fig. 6 shows the shape and location of the .