Conduction in the solid phase

Along with wall heat transfer coefficient in non-adiabatic reactors, another effect frequently added in models is that of thermal conduction in the solid phase (27, 28, 29). One should be particularly careful here, since most of the correlations available in the literature (9 y 32) are for effective... 

Axial heat conduction in the solid phase is important, however, when reactor light-off or hot spots in the reactor have to be considered [38]. 

Simulations performed at the same conditions, but without axial heat conductivity, showed identical temperature profiles as the ones given in Fig. 10, while results at a low mass flow, typically 0.83 kg m7 sec, showed a temperature of the solid phase at the inlet of the reactor that is lower than the temperature calculated from the model with axial heat conductivity. This phenomenon was also observed by Lie et al. [35] and indicates that axial heat conduction in the solid phase can be neglected under steady-state conditions when the fluid flow is large enough. 

In the geometrically coupled cell model, it is assumed that a fluid cell has contact with the front half of the particle in front of it. This model has been studied by Vanderveen el ai, (1968), and has been recently modified by Rhee et al. (1973) to account for thermal conductivity in the solid phase. 

Nucleophilic sttbstilutions. Nucleophilic substitutions can be conducted in the solid phase by means of quaternary ammonium exchange resins. For example, alkylation of jS-dicarbonyl compounds can be conducted by removal of the chloride ion from Amberlite IRA 900(C1") and then treatment of the resulting... 

The first two terms on the right-hand side consider the heat conduction in the solid phase in both directions. The first two heat sources in the bracketed expression consider the enthalpy flux due to gases that enter the electrodes ... 

Ionic materials do not conduct in the solid phase, since in this phase there are no ions. True/False... 

Thermal conduction in the solid phase is a key factor, as already mentioned in section 1.2.4. The heat conduction process is accounted for by Fourier s law in the heat balance equation which is thus a second order partial differential equation. An efficient numerical technique is required to avoid "numerical conduction" because the solid temperature gradient is very sharp at the light-off point (see section 3.1). There is no study of Ais numerical problem in the literature. However, Eigenberger (1972) studied the consequences of heat conduction on steady-state multiplicity. He showed that the conduction process is responsible for a reduction of the number of steady state solutions. In the example studied by Eigenberger, the steady-state solution is close to the "highest steady state" (i.e., steady state with the temperature maximum close to reactor inlet) without conduction because "the temperature maximum moves to the front of the reactor, driven by the backward conduction of heat". 

Polycondensadon is usually conducted in a melt at a temperature of up to 300-350 C for several hours. To prevent thermal decomposition in preparation of polyesters with high melting points, the last stage of synthesis is sometimes conducted in the solid phase. 

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