Abstract
Metal foams are widely studied as possible tools for the enhancement of heat transfer from hot bodies. The basic idea is that a metal foam tends to significantly increase the heat exchange area between the hot solid body and the external cooling fluid. For this reason, this class of porous materials is considered as a good candidate for an alternative to finned surfaces, with different pros and cons. Among the pros, we mention the generally wider area of contact per unit volume between solid and fluid. Among the cons is the difficulty to produce different specimens with the same inner structure, with the consequence that their performance may be significantly variable. This paper will offer a survey of the literature with a focus on the main heat transfer characteristics of the metal foams and the energy balance model based on Local Thermal Non-Equilibrium (LTNE). Then, a numerical simulation of the heat transfer at the pore-scale level for an artificial foam with a spatially periodic structure will be discussed. Finally, these numerical results will be employed to assess the macroscopic modeling of the flow and heat transfer in a metal foam. More precisely, the Darcy–Forchheimer model and the LTNE model adopted to describe the momentum and energy transfer in metal foams have been validated for metallic periodic structures.
Highlights
The high thermal conductivity in conjunction with the high values of porosity and permeability make the metal foams the most studied devices for heat transfer enhancement in the last years
This paper will offer a survey of the literature with a focus on the main heat transfer characteristics of the metal foams and the energy balance model based on Local Thermal Non-Equilibrium (LTNE)
In Equation (34), the Reynolds number has been evaluated with reference to the characteristic length dc [30]. These results show that periodic structures generated by a gyroid surface are characterised by heat transfer coefficients similar to those obtained for other periodic structures
Summary
The high thermal conductivity in conjunction with the high values of porosity and permeability make the metal foams the most studied devices for heat transfer enhancement in the last years. In the design of heat exchangers, the metal foams provide a significant alternative to the finned surfaces as tools for increasing the heat exchange area between the hot solid body and the cooling fluid. It is precisely the design of heat exchangers which motivates the control of such characteristics of the foams as the head loss of the cooling fluid and the heat transfer rate from the solid matrix to the fluid. There are several excellent and thorough reviews surveying the main flow and heat transfer properties of metal foams [1,2,3,4,5]. Our aim is to focus on some specific features of the metal foams such as the appropriate model for heat transfer between the solid and the fluid phase
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