Constant density adiabatic reaction

In order to derive specific numbers for the temperature rise, a first-order reaction was considered and Eqs. (10) and (11) were solved numerically for a constant-density fluid. In Figure 1.17 the results are presented in dimensionless form as a function of k/tjjg. The y-axis represents the temperature rise normalized by the adiabatic temperature rise, which is the increase in temperature that would have been observed without any heat transfer to the channel walls. The curves are differentiated by the activation temperature, defined as = EJR. As expected, the temperature rise approaches the adiabatic one for very small reaction time-scales. In the opposite case, the temperature rise approaches zero. For a non-zero activation temperature, the actual reaction time-scale is shorter than the one defined in Eq. (13), due to the temperature dependence of the exponential factor in Eq. (12). For this reason, a larger temperature rise is foimd when the activation temperature increases. 

Consider an exothermic irreversible reaction with first order kinetics in an adiabatic continuous flow stirred tank reactor. It is possible to determine the stable operating temperatures and conversions by combining both the mass and energy balance equations. For the mass balance equation at constant density and steady state condition,... 

At constant density, the volume is constant, no work can be done on the system, and since in an adiabatic reaction no heat flows into or out of the system, the thermodynamic energy equation per unit mass is... 

The theory of the multi-vibrational electron transitions based on the adiabatic representation for the wave functions of the initial and final states is the subject of this chapter. Then, the matrix element for radiationless multi-vibrational electron transition is the product of the electron matrix element and the nuclear element. The presented theory is devoted to the calculation of the nuclear component of the transition probability. The different calculation methods developed in the pioneer works of S.I. Pekar, Huang Kun and A. Rhys, M. Lax, R. Kubo and Y. Toyozawa will be described including the operator method, the method of the moments, and density matrix method. In the description of the high-temperature limit of the general formula for the rate constant, specifically Marcus s formula, the concept of reorganization energy is introduced. The application of the theory to electron transfer reactions in polar media is described. Finally, the adiabatic transitions are discussed. 

We have a first-order homogeneous reaction, taking place in an ideal stirred tank reactor. The volume of the reactor is 20 X 10 3 m3. The reaction takes place in the liquid phase. The concentration of the reactant in the feed flow is 3.1 kmol/m3 and the volumetric flow rate of the feed is 58 X 10 m3/s. The density and specific heat of the reaction mixture are constant at 1000 kg/m3 and 4.184kJ/(kg K). The reactor operates at adiabatic conditions. If the feed flow is at 298 K, investigate the possibility of multiple solutions for conversion at various temperatures in the product stream. The heat of reaction and the rate of reaction are... 

If a batch reactor initially contains 500 lb of acetylated castor oil at 340°C (density 0.90) and the operation is adiabatic, plot curves of conversion (fraction of the acetylated oil that is decomposed) and temperature vs time. It is estimated that the endothermic heat effect for this reaction is 15,000 cal/g mole of acetic acid vapor. The acetylated oil charged to the reactor contains 0.156 g of equivalent acetic acid per gram of oil i.e., complete decomposition of 1 g of the oil would yield 0.156 g of acetic acid. Assume that the specific heat of the liquid reaction mixture is constant and equal to 0.6 Btu/(lb)(°F). Also assume that the acetic acid vapor produced leaves the reactor at the temperature of the reaction mixture. 

Quantal spectroscopic constants, as defined in Eq. (25), were calculated for the three reactions from fits to assigned peak energies in the finite-resolution density. Vibrationally adiabatic thresholds (the maxima in vibrationally adiabatic curves calculated using the procedure described for H 4- H2) were also least-squares fit with Eq. (25). Results are... 

In the SAM experiments the molecular redox group transfers an electron to/from a metal electrode. How does the rate depend upon the metal Equation (71), the expression for the rate constant for this process, is based on the assumption that the electron transfer process is nonadiabatic and that all electronic levels near the Fermi level (represented in the metal density of states near E p) contribute equally to the rate. If the reaction is adiabatic, it should not depend on the nature of the metal. If it is nonadiabatic and all electronic levels near Ef contribute equally to the rate, then k Jf>(Ep) should be independent of the metal. Gosavi and Marcus calculated rate constants for gold (p(Ef) = 0.29 eV atom" ) and platinum (p( p) = 2.2 eV atom" ) and found that the Pd d bands contribute little to the rate. This was confirmed experimentally in a study of (NH3)5RuNC5H4NHC(0)(CH2)i5S— in monolayers of H0C(0)(CH2)isS— on different metals. The rate constants were 1.0 0.3s", 1.7 0.4s", and 0.6 0.2s" for Au, Pt, and Ag A was 0.8 0.1 eV. 

Based on a co-flow configuration, the effect of various parameters on cell performance has been studied systematically. The study covers the effect of (a) air flow rate, (b) anode thickness, (c) steam to carbon ratio, (d) specific area available for surface reactions, and (e) extend of pre-reforming on cell efficiency and power density. Though the model predicts many variables such as conversion, selectivity, temperature and species distribution, overpotential losses and polarization resistances, they are not discussed in detail here. In all cases calculations are carried for adiabatic as well as isothermal operation, fii calculations modeling adiabatic operation the outer interconnect walls are assumed to be adiabatic. All calculations modeling isothermal operation are carried out for a constant temperature of 800°C. Furthermore, in all cases the cell is assumed to operate at a constant voltage of 0.7 V. 

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