Thermokinetic effects

Current Seebeck (Thompson effect) Diffusion and membrane potential Electric conduction Rouss effect thermokinetic effect... 

A nonlinear dependence of the contribution of the most important elementary gas-phase reactions that determine the course of the DMTM process on the concentration of initial reagents, a strong temperature dependence of the key stages, and a complex interaction of the homogeneous and heterogeneous reactions give rise to a variety of thermokinetic effects in... 

Thus, in certain conditions, under the influence of thermokinetic effects, the partial oxidation of methane in a CSTR becomes unstable. All the parameters, including the temperature and methanol yield, can vary dramatically. Figure 8.11 displays the calculated temperature evolution for the nonisothermal oxidation of methane when the temperature of the CSTR... 

If we consider the effect of the real values of the parameter Sh/Nu on the region of instabilities, then the value Lw decreases however, the inequality Lw > 1 is still valid (12). From the material presented it is apparent that the occurence of unstable steady states cannot be explained in terms of thermokinetic theory (12). 

The use of excess formic acid to destroy excess nitric acid (5M) in nuclear fuel reprocessing waste solutions at 100°C is potentially hazardous because of an induction period, high exothermicity and the evolution of large amounts of gas, mainly carbon dioxide, dinitrogen oxide and nitrogen oxide, with some nitrogen and dini-trogen tetraoxide. The system has been studied thermokinetically, and the effects of various salts (which decrease the reaction rate) and sulfuric acid (which increases the rate) were determined [1],... 

Fubini et al. (121-123) used calorimetric and thermokinetic results for the adsorption of H2 and CO at room temperature to determine the occurrence of different crystal faces on different samples of ZnO. They accomplished this by identifying the various kinds of gas-surface interactions and by evaluating the variations in the population and interaction energy of the adsorption sites. The interaction of H2 with one of the ZnO samples showed an unusual effect the heat of adsorption, related to the formation of atomic H species... 

The activation parameters are collected in Table III for the 1,2-dioxetanes (1) and a-peroxylactones (2). Clearly, variation of substituent structure has a minor effect on the activation parameters. A significant exception is the diadamantylidene system (lz), which is unusually thermally stable.38 Assuming a diradical mechanism for the thermal decomposition of 1,2-dioxetanes, O Neal and Richardson97 were able to reproduce the experimental activation parameters with good precision, employing thermokinetic calculations developed by Benson.9741... 

The dynamic phenomena associated with the rhodium-catalyzed oxidation of carbon monoxide, methane and propane have been studied by in-situ infrared thermography. High-resolution temperature maps of the reacting catalyst revealed the mobility of the reaction front during ignition and extinction of the CO oxidation, and the development of thermokinetic oscillations. The catalytic oxidation of methane and propane produced weaker dynamics. Chemisorption and kinetic experiments suggest that the competitive adsorption of the reactants and the occurrence of self-inhibition, represent key factors in the development of the observed transient effects. 

In category 1, the order of the autocatalytic species in the cycle reaction is equal to one (and equal to the order of X in the exit reaction). Category 2 oscillators include mechanisms with autocatalytic reaction of a higher (effective) order in X than the order of X in the removal reaction, and the type X species need not necessarily be chemical species. Rather, they may include vacant surface sites in heterogeneous catalysis, or temperature in thermokinetic oscillation. 

Systematic studies on thermokinetic wave propagation have been reported for various reactions, and different approaches have been reported to implement nonisothermal effects in the theoretical modeling [53]. Even if the details of the reaction mechanism are less well understood, the basic features of spatio-temporal pattern formation with such systems can often be modeled successfully, because the decisive effects can be approximated by a heat balance equation in which the chemistry is reduced to single variable and surface diffusion of adsorbates is neglected [54,55]. 

Thermokinetic Model of Electrolysis in the Conditions of Anode Effect... 

Kinetic analysis of PP compositions thermo-oxidative degradation at heating rates of 3, 5 and lOK/min. was carried out using NETZSCH Thermokinetics software in order to provide an extra evidence of the diffusion-stabilizing effect of nanoclay structure. 

Many methods are used to determine heat effects. Some of them allow the determination of the total heat effect Q studied, while others permit the determination not only of the total heat effects, but also of the course of thermal power P in time t (function P(t), called the thermokinetics or thermogenesis). 

In the dynamic method ( 3.2.6), the calorimeter is treated as a simple body of uniform temperature. The detailed form of Eq. (1.148) is then a heat balance equation of a sint5)le body. The dynamic method is a one of the most frequently used in the determination of total heat effects and thermokinetics. 

The multibody (domain) method [67, 209, 210] allows the determination of thermokinetics as well as the total heat effects of the process examined. The method is based on the general heat balance equation [Eq. (1.148)]. The mathematical model of the calorimeter is described by the following set of equations ... 

Thermokinetics is determined on the basis of deconvolution of the pulse response of the examined system and the measured thermogram. For calculations, the first nonzero value of the pulse response R (R is taken. The increase in temperature AT of the element (in which the heat effect is generated) is determined on the basis of the equation... 

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