Thermal conductivity of polyimide foams

Thermal radiation in ultralight metal foams with open cells

“…More recently, Doermann and Sacadura [26], Baillis et al [27,28], Glicksman et al [29,30], Kuhn et al [31], Lee and Cunnington [32,33] and Caps et al [34], amongst others, modelled thermal radiation in fibrous insulations by using a diffusion approximation based on a combination of the geometric optics laws and diffraction theory. Since the latter approach can provide a better prediction and clearer physical understanding on thermal radiation in metal foams, it will be employed below.…”

“…If the thickness of the foam sample is large enough for it to be optically thick, its radiative conductivity can be approximated by the Rosseland equation [26][27][28][29][30][31][32][33][34] as…”

“…The transport process of radiation in metal foams is complicated because of the complex cellular morphology and the inherent complexities associated with the transport mechanism itself. Although numerous studies on thermal radiation [21][22][23][24][25][26][27][28][29][30][31][32][33][34] have been carried out for polymer foams and fibrous insulations, little information can be found in the open literature on radiative heat transfer in metallic foams. Since metal foams have much higher effective solid conductivities (k c > 10 W/mK) and larger diameters of cell ligaments (d o ¼ 30-800 m), in contrast with the commonly used thermal insulation foams (k c < 1 W/mK and d o ¼ 3-20 lm), it is expected that their radiative properties will be considerably different from those of the insulation foams.…”

Influence of Water on the Total Heat Transfer in ‘Evacuated’ Insulations

“…Significant coupling effects have been observed in semi-transparent media like monolithic aerogels or low-density foams in combination with low-emissivity boundaries or integrated radiation shields [6,7], as well as in materials with dot-like contacts between fibers and grains [8]. For example, in a bed of glass spheres, comparing the total thermal conductivity of the evacuated and the non-evacuated specimen, the contribution from the gas is seven times as large as expected just from the thermal conductivity of still air [4].…”

The effects of PE additive on the performance of polystyrene vacuum insulation panels

“…Many previous studies have attempted to determine the heat transfer of solid conduction [2][3][4][5], gaseous conduction [5] and thermal radiation [6][7][8][9][10][11][12][13][14][15][16][17][18] in porous medium. Most of the studies assumed all closed-cell or all open-cell structures in their analyses.…”