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Open-cell metal foams are promising materials for heat transfer augmentation, due to their tortuosity and high specific surface area. The volume-averaging technique under the assumption of local thermal non-equilibrium between the solid and fluid phases is often used to model devices equipped with open-cell foams; it requires an accurate knowledge of the interfacial convective heat transfer coefficient. Its dependence on the anisotropy of elongated foam cells is investigated numerically in the present work. Four aluminum foam samples with different porosities and equal PPIs are considered; their geometry is reconstructed by means of x-ray computed tomography. Mass, momentum and energy equations for the fluid phase (air) are solved, while the solid phase is accounted for with a uniform heat flux boundary condition. Interfacial convective heat transfer coefficients and Nusselt numbers are predicted. The dependence of the interfacial heat transfer coefficient in the elongation direction on the effective porosity and fluid inlet velocity is pointed out. The comparison of predicted values with those given by correlations from the open literature shows a good agreement. Finally, correlations for the prediction of Nusselt numbers, accounting for the foam anisotropy, are proposed, which can be useful in the study of metal foams.

An analytical solution to the three-dimensional quasi-stationary problem in a finite depth and width solid with a circular Gaussian moving heat source at the body surface is developed and analyzed. The temperature distribution and the axial coordinate at which the maximum midplane temperature is achieved are presented as a function of Peclet number, solid thickness and width. The dependence of the maximum midplane temperature on the process parameters is highlighted. Combinations of process parameters for which the solution to the three-dimensional problem can be approximated by those to simpler models are pointed out.

Simplified thermal models in laser and electron beam surface hardening can be very useful to industrial users. Hardening depth as a function of austenitization temperature and Peclet number is evaluated for one-dimensional stationary and two-dimensional uniform strip moving heat source problems without melting. Reliable correlations for predicting both hardening depths and maximum temperatures are given in terms of dimensionless meaningful parameters. Calculated values are also compared with experimental results reported by other authors.