Thermal diffusivity determination

Whereas heat capacity is a measure of energy, thermal diffusivity is a measure of the rate at which energy is transmitted through a given plastic. It relates directly to processability. In contrast, metals have values hundreds of times larger than those of plastics. Thermal diffusivity determines plastics rate of change with time. Although this function depends on thermal conductivity, specific heat at constant pressure, and density, all of which vary with temperature, thermal diffusivity is relatively constant. 

Thermal diffusivity determines plastics rate of change with time. Although this function depends on thermal conductivity, specific heat at constant pressure, and density, all of which vary with temperature, thermal diffusivity is relatively constant. 

The foremnner of the modern methods of asphalt fractionation was first described in 1916 (50) and the procedure was later modified by use of fuller s earth (attapulgite [1337-76-4]) to remove the resinous components (51). Further modifications and preferences led to the development of a variety of fractionation methods (52—58). Thus, because of the nature and varieties of fractions possible and the large number of precipitants or adsorbents, a great number of methods can be devised to determine the composition of asphalts (5,6,44,45). Fractions have also been separated by thermal diffusion (59), by dialysis (60), by electrolytic methods (61), and by repeated solvent fractionations (62,63). 

The thermal diffusivity for aluminum is = 5.2 x 10 m s [50]. Use this value to determine the time necessary for substantial temperature change over the length scale of 10 following creation of shear bands in the shock front. Should the temperature evolution of the shear band be included in a constitutive description on time scales of compression and release ... 

If a laser pulse of sub-picosecond duration is used, deposition of the laser energy to the sample is so rapid that the thermal diffusion length is determined by the diffusion of hot electrons before they transfer the energy to the lattice of the solid sample. 

The spatially periodic temperature distribution produces the corresponding relxactive index distribution, which acts as an optical phase grating for the low-power probing laser beam of the nonabsorbed wavelength in the sample. The thermal diffusivity is determined by detecting the temporal decay of the first-order diffracted probing beam [°o exp(-2t/x)] expressed by... 

Farver J.R. and Giletti B.J. (1989) Oxygen and strontium diffusion in apatite and potential applications to thermal history determinations. Geochim. Cosmochim. Acta S3, 1621-1631. 

In addition, the thermal diffusivity of the soil at both locations varies from a = 10 to 0 = 10 m /s. The post hole depth must be below the frost line, so that we do not have frost heave on our posts. The frost line would be at the depth where temperature never goes below freezing, T = 0°C. We should set the cosine term from equation (E4.2.2) to -1 and set the temperature to 0°C to determine this depth ... 

Person 1 Determine the density and thermal diffusivity for polycarbonate at 350°C from the plots. 

A five-fold increase in effective burning rate is possible by using 0.005-in diameter silver wires. The degree of increase that can be obtained with wires of various metals is apparently determined by the thermal diffusivity and melting temperatures of the metal. This is illustrated in Table II (12). The burning rate at 1000 p.s.i.a. and 70°F. 

The parameters n and k are determined by such factors as the initial reactant concentration and the ambient temperature, whereas p is simply the ratio of the mass and thermal diffusivities. We can treat eqn (10.51) as a condition on P (in which it is quadratic) in terms of /i and k. If the inequality is to be satisfied, giving the possibility of diffusion-driven instability, then P must be larger than a given critical value Pc given by... 

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