The Effective Thermal Conductivity of High Porosity Fibrous Metal Foams

The effective thermal conductivity of open cell replicated aluminium metal sponges

“…Three simplified models were used, one based on the assumption that conduction through the solid material can be either in series or parallel. A simple scaling expression was also used, along with D model [8,15,36], and an analytical model based on the numerical and 3D tomographic structure parameters in terms of ratio between the thickness of the struts and the nodes (referred to as lumps in the originating work, and preserved in the notation here, D st /d lu ) and the node shape [18]. Two empirical expressions for high porosity (> 90%) foams are also compared to our experimental measurements.…”

“…There is a network of solid ligaments of generally high thermal conductivity and a fluid with lower thermal conductivity [8,9]. The principle process of heat transfer in non-flowing fluid saturated media is conduction through both the solid and fluid phases.…”

“…The effective thermal conductivity has been found to be highly sensitive to the porosity, increasing as the porosity decreases [5][6][7][8][13][14][15]. The effect of pore size on ETC is less significant, and generally no noticeable effect of pore size has been reported [5,8,9,15], provided the pore size is below a certain value shown to be 4 mm diameter in closed cell polymer foams which is sufficient to suppress convection [3,16,17]. Although it can be demonstrated that the pore size has little direct influence on ETC, the pore size will influence the foam fabrication process, and by establishing limits on what foams may actually be produced (there are usually upper and lower size limits).…”

Estimation of effective thermal conductivity enhancement using foam in heat exchangers based on a new analytical model

“…The simplified one-dimensional model for estimating the eff k of foam is expressed as ( ) eff f s k =εk + 1-ε k (Boomsma and Poulikakos, 2001;Calmidi and Mahajan, 1999). But this equation is not precise in the case of the vastly different thermal conductivities encountered in the metal foam combinations.…”

“…But this equation is not precise in the case of the vastly different thermal conductivities encountered in the metal foam combinations. Calmidi and Mahajan (1999) proposed a onedimensional conductivity model considering the porous medium to be formed of a two-dimensional array of hexagonal cells and using square nodes at the intersection of ligaments. Using a onedimensional REV for estimating the effective thermal conductivity is not precise.…”