In this article, a new two-dimensional (2D) explicit analytical model for the evaluation of the radiation heat transfer in highly porous open-cell metal foams is formulated and validated. A correction factor, C, is introduced to correct the deviation of the specific area in a simplified manner. Numerical results are compared with the published experimental data and three-dimensional (3D) model proposed in previous works. It reveals that the present two-dimensional model is proved to be relatively accurate in estimating the radiative conductivity for all the investigated structures. In the current work, the effects of the control parameters, such as the number of order in the iterative procedure, solid emissivity, the temperature difference, shape of solid particle and correction factor on the predictions of radiation characteristics are well discussed.

Conclusions

A newly developed two-dimensional model is employed for the calculation of the radiation heat transfer in highly porous open-cell metal foams and the results are compared with available experimental data as well as three-dimensional numerical solution proposed in the previous work. A new correction factor, C, is introduced for correcting the deviation of specific area between simplified two-dimensional structure and three-dimensional structure. The results demonstrated that using a two-dimensional analytical model instead of a three-dimensional approach leads to a relatively minor discrepancy. Besides, the calculation is simpler than the three-dimensional model because of the simpler determination of configuration factors and coefficients due to the nature of the two-dimensional structure, which is significant for engineering applications. The effect of the solid emissivity on the radiative conductivity is more significant at higher temperature. The radiative conductivity is not sensitive to the temperature difference during the iterative procedure. The effect of the shape of the solid particle is observed and it is relatively small. It is found that the samples with smaller PPI could lead to a higher value of radiative conductivity. The correction factor C is found to be significant for the present model. Overall, the main contribution of the proposed two-dimensional model is the simplicity and convenience of calculation with good accuracy compared with the previous three-dimensional model. In addition, the present model is also suitable for vacuum condition. Future works are still needed to investigate the thermal radiation in metal foam in atmospheric pressure. Besides, more experimental data of different metal foams (material, PPI, porosity, etc.) are needed to validate the present model.

The results have been published on Applied Thermal Engineering 93 (2016) 1273–1281.