Conductivity effects

Reactor Configuration. The horizontal cross-sectional area of a reactor is a critical parameter with respect to oxygen mass-transfer effects in LPO since it influences the degree of interaction of the two types of zones. Reactions with high intrinsic rates, such as aldehyde oxidations, are largely mass-transfer rate-limited under common operating conditions. Such reactions can be conducted effectively in reactors with small horizontal cross sections. Slower reactions, however, may require larger horizontal cross sections for stable operation. 

Trace elements added to copper exert a significant influence on electrical conductivity. Effects on conductivity vary because of inherent differences ia effective atomic size and valency. The decrease ia conductivity produced by those elements appearing commonly ia copper, at a fixed atomic concentration, rank as follows Zn (least detrimental), Ag, Mg, Al, Ni, Si, Sn, P, Fe (most). Table 12 summarizes these effects. In the absence of chemical or physical interactions, the increase in electrical resistivity is linear with amounts of each element, and the effect of multiatom additions is additive. 

Table 12. Solubility Limits and Electrical Conductivity Effects of Elemental Additions to Copper ...

A pseudo-convective heat-transfer operation is one in which the heating gas (generally air) is passed over a bed of solids. Its nse is almost exchisively limited to drying operations (see Sec. 12, tray and shelf dryers). The operation, sometimes termed direct, is more aldu to the coudnctive mechanism. For this operation, Tsao and Wheelock [Chem. Eng., 74(13), 201 (1967)] predict the heat-transfer coefficient when radiative and conductive effects are absent by... 

Given the complications of strongly nonlinear mechanical and electrical behaviors in a strongly coupled mode along with electrical conduction effects, it is not difficult to appreciate why the physical processes are poorly understood. 

Interesting systems, mainly with respect to solid-state optoelectronics and chalco-genide glass sensors (due to ionic conductivity effects) are found among the Group IIIB (13) and IVB (14) chalcogenides, such as the p-type semiconductors MSe (M = Ga, In, Sn), SnS, and GeX (X = S, Se, Te). Some of the IIIB compounds. 

Stief et al. [125] investigated the performance of coimter-current micro heat exchangers, especially with respect to the wall conduction effects and the choice of... 

In closer approximations, correction must be made for conductivity effects (relaxation and electrophoretic) and for the real shape of the particles. Thus, the velocity of electrophoretic motion depends on the composition of the... 

Carne, M., and D. H. Charlesworth, 1966, Thermal Conduction Effects on the Critical Heat Flux in Pool Boiling, Chem. Eng. Prog. Symp. Ser. 62(64) 24-34. (5)... 

The physical properties of the catalyst (specific surface area, porosity, effective thermal conductivity, effective diffusivity, pellet density, etc.). 

Typically items with a thickness of less than about 1 mm can be treated as thermally thin. This constitutes single sheets of paper, fabrics, plastic films, etc. It does not apply to thin coatings or their laminates on noninsulating substances, as the conduction effects of the substrate could make the laminate act as a thick material. The paper covering on fiberglass insulation batting would be thin pages in a closed book would not. 

In materials that have high ionic conductivity, effects such as the above are undoubtedly very important. They show up particularly in materials that have a high concentration of mobile ions and in experimental values of the ac conductivity measured as a function of frequency. In materials with a high carrier concentration, mobile ions are inevitably quite close together, separated by at most a few angstroms. Consequently, ions cannot hop in isolation but are influenced by the distribution of mobile ions in their vicinity. This contrasts with the behaviour of dilute defect systems with low carrier concentrations. In these, the mobile ions are well separated from each other and their conduction can largely be treated in terms of isolated hops. 

As far as heat transfer is considered, Fenner [27] made a detailed comparison of the thermally fully developed flow and thermally developing flow. He indicated that the thermally developed flow will not be achieved when heat conduction effects become significant [34]. Bruker et al. [35] experimentally verified that the thermally developing flow analysis provided a more accurate description of the flow in the extruder. 

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