Numerical analysis of the heat transfer enhancement by using metal foam

Abstract

Forced convection heat transfer in metal foam pipe under uniform heat flux was investigated numerically. Water has been used as the fluid medium in numerical simulations with copper metal foam. The test sample used metal foam for four cases (A, B, C, and D) by using varying thicknesses of foam along the pipe. In case (A), the pipe was completely filled with metal foam; in case (B), the pipe was partially embedded with metal foam and close to the wall; in case (C), the pipe was partially filled in the section's center; and in case (D), the pipe was partially filled in the form of three sections along the pipe. The foam employed in this study has a porosity of 0.90 and pore density ranges from (10–40) PPI. The fluid and energy transfers are simulated using the Forchheimer-extended Darcy equation and the local thermal non-equilibrium (LTNE) model. The simulation is performed using the commercial software FLUENT with specific boundary conditions. Turbulence was taken into account using the k- ε model. The results reveal that when the pipe is filled partially with metallic foam as indicated in case B, the Nusselt ratio rises due to the velocity gradient and temperature distribution is more homogenous inside the pipe led to enhancement in overall heat transfer. Also, the metallic foam 40PPI has a highly Nusselt number ratio, with a big value equal to 5.5 in case B due to the highly conductive surface area of heat transfer from the wall heated to the fluid. Additionally, the pipe in case A was completely filled with metallic foam, resulting in a bigger pressure drop than in the other cases, which increases flow resistance. The metal foam in case C, which is centered in the pipe's center, has the lowest pressure drop measurement. The 10PPI metallic foam exhibits the highest performance factor when compared to other metallic foam.

Keywords

• Heat transfer coefficient
• Pressure drop
• Metal foam
• Nusselt number
• Heat flux