Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Factor thermal diffusivity

Thermal transpiration and thermal diffusion will not be considered here, but it would be incorrect to assume that their influence is negligible, or even small in all circumstances. Recent results of Wong et al. [843 indi cate that they may Influence computed values of the effectiveness factor iby as much as 30. An account of thermal transpiration and thermal diffu-Ision is given in Appendix I. [Pg.157]

If temperature gradients are small, Cr may be regarded as effectively constant. Furthermore, Kart is a function of composition, being approximately proportional to the product x, Xr. It is therefore useful to work in terms of the thermal diffusion factor a, where ... [Pg.590]

Equation 10.61 gives the mole fraction of the two components A and B as a function of the absolute temperatures and the thermal diffusion factor. [Pg.590]

Table 10.5. Values of thermal diffusion factor (a) for binary gas mixtures (A is the heavier component, which moves towards the cooler end)... Table 10.5. Values of thermal diffusion factor (a) for binary gas mixtures (A is the heavier component, which moves towards the cooler end)...
Thermal diffusivity Temperature sensitivity Temperature difference Thickness of tube Aspect ratio, relation of Cp/Cy Fluid dielectric constant Wall zeta potential Dimensionless temperature Friction factor, Debye length Mean free path Dynamic viscosity Kinematic viscosity Bejan number Density... [Pg.193]

OL velocity correction factor (unitless) or thermal diffusivity (area/time)... [Pg.652]

The time-dependence of the SSP process has to be viewed in connection with the temperature and the factors concerning diffusion. After a certain period into the reaction, no increase in the IV is observed and thermal decomposition becomes the dominant process. [Pg.235]

To model diffraction intensities, detector effects and the background intensity from thermal diffuse scattering must be included. A general expression for the theoretical intensity considering all of these factors is... [Pg.159]

Early studies, which did not include many high-order reflections, revealed systematic differences between spherical-atom X-ray- and neutron-temperature factors (Coppens 1968). Though the spherical-atom approximation of the X-ray treatment is an important contributor to such discrepancies, differences in data-collection temperature (for studies at nonambient temperatures) and systematic errors due to other effects cannot be ignored. For instance, thermal diffuse scattering (TDS) is different for neutrons and X-rays. As the effect of TDS on the Bragg intensities can be mimicked by adjustment of the thermal parameters, systematic differences may occur. Furthermore, since neutron samples must be... [Pg.86]

All of the above discussion of diffusion considers physical motion of particles excited by thermal energy of the system (because the system is not at 0 K), rather than by outside factors. Eddy diffusion is different. It is due to random disturbance in water by outside factors, such as fish swimming, wave motion, ship cruising, and turbulence in water. On a small length scale (similar to the length scale of disturbance), the disturbances are considered explicitly as convection or flow in the mass transfer equation (Equation 3-19). On a length scale much larger than the individual disturbances, the collective effect of all of the disturbances... [Pg.188]

Thermal diffuse scattering (TDS) is ascribed to low-frequency lattice vibrations. The atoms in a perfect crystal are not fixed to their sites and oscillate about their positions. The Bragg intensities are reduced by the Debye-Waller factor, proportional to... [Pg.139]

With krypton, the ability to use larger samples of low-area powders facilitates measuring low surface areas because larger signals are generated in the absence of thermal diffusion. Also, as is true for nitrogen, krypton measurements do not require void volume, or ideality corrections, nor is thermal transpiration a factor as in the volumetric measurements. [Pg.179]

The quantity kr is so defined that when hr is positive the component A moves to the cold region, and when kr is negative A moves to the hot region. This definition of kr is in agreement with the accepted definitions of previous workers, and in particular with the text books of Chapman and Cowling (C3) and Grew and Ibbs (G12). In the gas phase many authors prefer to write the mass flux in terms of the thermal diffusion factor a, which is defined as... [Pg.176]

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... [Pg.274]

In this equation the kinematic viscosity is v = fi/p, the thermal diffusivity is a = X/p-cp, and cp is the specific heat (per unit mass) at constant pressure. The Prandtl number is related to the Eucken factor as... [Pg.100]

The thermal diffusivity in the basal plane is isotropic and the diffusivity along the c-axis is smaller than in the basal plane by a factor of 4. [Pg.122]


See other pages where Factor thermal diffusivity is mentioned: [Pg.92]    [Pg.92]    [Pg.10]    [Pg.658]    [Pg.55]    [Pg.144]    [Pg.140]    [Pg.207]    [Pg.159]    [Pg.439]    [Pg.439]    [Pg.440]    [Pg.228]    [Pg.391]    [Pg.302]    [Pg.255]    [Pg.259]    [Pg.261]    [Pg.264]    [Pg.189]    [Pg.251]    [Pg.471]    [Pg.33]    [Pg.106]    [Pg.14]    [Pg.220]    [Pg.180]    [Pg.226]    [Pg.233]    [Pg.324]    [Pg.117]    [Pg.117]    [Pg.118]    [Pg.487]    [Pg.642]   
See also in sourсe #XX -- [ Pg.51 ]




SEARCH



Diffusion factor

Diffusivities thermal

Diffusivity factors

Thermal diffusion factor

Thermal diffusivity

Thermal factor

© 2024 chempedia.info