Thermal coupling coefficient

FIGURE 18.34 Schematic of (a) the physical system and (ft) predicted overall thermal coupling coefficient for Gaussian irradiation of aluminum [166],... 

Thermal Properties. Many commercial glass-ceramics have capitalized on thek superior thermal properties, particularly low or zero thermal expansion coupled with high thermal stabiUty and thermal shock resistance properties that are not readily achievable in glasses or ceramics. Linear thermal expansion coefficients ranging from —60 to 200 x 10 j° C can be obtained. Near-zero expansion materials are used in apphcations such as telescope mirror blanks, cookware, and stove cooktops, while high expansion frits are used for sealing metals. 

Effectively, Eqs. (86) and (87) describe two interpenetrating continua which are thermally coupled. The value of the heat transfer coefficient a depends on the specific shape of the channels considered suitable correlations have been determined for circular or for rectangular channels [100]. In general, the temperature fields obtained from Eqs. (86) and (87) for the solid and the fluid phases are different, in contrast to the assumptions made in most other models for heat transfer in porous media [117]. Kim et al. [118] have used a model similar to that described here to compute the temperature distribution in a micro channel heat sink. They considered various values of the channel width (expressed in dimensionless form as the Darcy number) and various ratios of the solid and fluid thermal conductivity and determined the regimes where major deviations of the fluid temperature from the solid temperature are found. 

In such a material under these conditions, Fourier s law again pertains, but the thermal conductivity K depends on the direct coefficient Lqq, as in Eq. 2.25, as well as on the direct and coupling coefficients associated with electrical charge flow. In general, the empirical conductivity associated with a particular flux depends on the constraints applied to other possible fluxes. 

Heating up amorphous solids, we observe an unsteady increase A0th of the thermal expansion coefficient in a characteristic temperature range. This effect is coupled with the formation of the free volume (Fig. 10) and a strong decrease of... 

As a final note on this section, whichever method is used, it is also necessary to consider how the pyroelectric is mechanically mounted in the system. Any mechanical clamping (such as bonding the material to a substrate of different thermal expansion coefficient) can lead to spurious currents due to changes in the stress on the sample, coupling via one or more of the piezoelectric coefficients. 

The hybrid circuit 10 comprises a buffer structure 16 which is comprised of a material which accommodates the difference in thermal expansion coefficients of the HgCdTe detector array 12 and the silicon read-out chip 14. The buffer layer is made of sapphire which also has good thermal conductivity properties. The buffer structure has laser drilled vias 18 which are formed in registration with unit cells of the detector array and the read-out circuit. Each of the vias is provided with indium bumps 20 at opposing ends thereof. The buffer structure is interposed between the detector array and the read-out chip. Cold weld indium bump technology is employed to couple the bumps 20 to the buffer structure. The buffer structure is further... 

The possibility of negative thermal-expansion coefficient (TEC) values along a direction of strong coupling in layered or chain structures (the so-called membrane effect") was suggested for the first time by Lifshitz [4] for strongly anisotropic compounds. In the phonon spectra of such compounds... 

Table 1.1. Abundance of the metal in the earths s crust, optical band gap Es (d direct i indirect) [23,24], crystal structure and lattice parameters a and c [23,24], density, thermal conductivity k, thermal expansion coefficient at room temperature a [25-27], piezoelectric stress ea, e3i, eis and strain d33, dn, dig coefficients [28], electromechanical coupling factors IC33, ksi, fcis [29], static e(0) and optical e(oo) dielectric constants [23,30,31] (see also Sect. 3.3, Table 3.3), melting temperature of the compound Tm and of the metal Tm(metal), temperature Tvp at which the metal has a vapor pressure of 10 3 Pa, heat of formation AH per formula unit [32] of zinc oxide in comparison to other TCOs and to silicon...

Coefficients Lqq and Lt] are associated with the thermal conductivity k and the mutual dififusivity D, respectively, while the cross coefficients Liq and Lqi define the coupling. Thermal conductivity (k) is related to Lqq by k = LqJT, while the thermal diffusion coefficient is related to Liq by Liq = pDTi. Tables 7.9 and 7.10 show the values of the phenomenological cofficients Lq for the ternary mixture of toluene (l)-chlorobenzene (2)-bromobenzene (3) at 298.15 and 308.15 K. 

If we use Eq. (7.101) instead ofEq. (7.105) and a thermal diffusion coefficient for one-dimensional heat and diffusion flows for a binary mixture, we have the following coupled balance equations ... 

For a ternary mixture, equations above can describe thermodynamically and mathematically coupled mass and energy conservation equations without chemical reaction, and electrical, magnetic and viscous effects. To solve these equations, we need the data on heats of transport, thermal diffusion coefficient, diffusion coefficients and thermal conductivity, and the accuracy of solutions depend on the accuracy of the data. 

In myoglobin, we find that the anharmonic contribution significantly enhances thermal conduction over that in the harmonic limit, by more than a factor of 2 at 300 K. Moreover, the thermal conductivity rises with temperature for temperatures beyond 300 K as a result of anharmonicity, whereas it appears to saturate around 100 K if we neglect the contribution of anharmonic coupling of vibrational modes. The value for the thermal conductivity of myoglobin at 300 K is about half the value for water. The value for the thermal diffusivity that we calculate for myoglobin is the same as the value for water. Thermal transport coefficients for other proteins will be presented elsewhere. 

NEM of equation (2) for perturbations in the coupling coefficients of the nonlinear NEM strategy [7]. For the treatment of local thermal and hydraulic and fission product feedbacks, an additional second order accurate, nonlinear correction is applied in the evaluation of equation (3). This correction is obtained by direct substitution of the uncorrected power density response of equation (3) into analytical sensitivities for the change in cross-section with locd power [14]. 

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