Solid thermal conductivity

ZT Y r A A A A A AC dimensionless thermoelectric figure of merit electronic coefficient of heat capacity (1+ZT)F2 crystal field singlet non-Kramers doublet (crystal field state) crystal field triplet crystal field triplet hybridization gap jump in heat capacity at Tc K KL -min P 6>d X JCO total thermal conductivity of solid thermal conductivity of electrons or holes thermal conductivity of lattice minimum lattice thermal conductivity electrical resistivity Debye temperature magnetic susceptibility magnetic susceptibility at T = 0... 

Solids There is no reliable method for estimating solid thermal conductivity at this time. 

In Table 1.10 those dimensionless groups that appear frequently in the heat and mass transfer literature have been listed. The list includes groups already mentioned above as well as those found in special fields of heat transfer. Note that, although similar in form, the Nus-selt and Biot numbers differ in both definition and interpretation. The Nusselt number is defined in terms of thermal conductivity of the fluid the Biot number is based on the solid thermal conductivity. 

Figure 23.2. Experimentally derived values symbols) of the ratio backbone thermal conductivity/solid thermal conductivity XoHs as a function of the solid volume fraction f for different silica aerogels by Lu and Heinemaim [8,11], Also the ratio is given for porous glass Vycor [12]. The data indicate that the soUd thermal conductivity for the investigated silica aerogel samples follows a scaling law according to (23.7) with the scaling exponent a = 2 solid line).

Organic aerogels (Part IV) are of special interest due to their thermal insulation properties. The organic solid backbone has a low solid thermal conductivity in comparison to inorganic aerogels [27]. Heat transfer within resorcinol-formaldehyde (RF) aerogels... 

Figure 23.16. Solid thermal conductivity determined for a set of carbon aerogels treated at different temperatures. The values were determined for a temperature of 300°C under vacuum [43].

The specific heat not only describes the capacity to store heat, but also influences the dynamics of heat transfer within aerogels according to the equation of heat transfer (23.1) and (23.4). The higher the specific heat, the slower the heat propagation within a material, if the density and the effective thermal conductivity remain constant. In the late eighties and early nineties several authors investigated the specific heat of silica aerogels in detail [9,51, 52, 54, 64-67]. The focus of their research work was the study of the density of vibrational states g(a>) correlated to the specific heat and the solid thermal conductivity by phonons ... 

Good VIP insulation has low density (to reduce solid thermal conductivity), small pore size (to reduce gas thermal conductivity), high opacity (to reduce radiation thermal conductivity), and must be very rigid (to keep its shape while being evacuated). Because Aerocore is an organic LDMM, it has all four qualities - making it the only material that combines all the necessary components for the perfect VIP insulation. 

Emmerling and Fricke (1997) proposed that there is a strong relationship between the morphological and topological features of fractal gel networks and properties such as elasticity and solid thermal conductivity of the aerogels. They... 

SOLIDS (THERMAL CONDUCTIVITY OF) Thermal Conductivity of Solids at Low Temperatures (1) 262 Accurate Measurement of Certain Physical Properties Down to 20 K (1) 267 STEEL... 

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