Simulation non-isothermal

This model is implemented in the novel object-oriented simulator RockFlow-TH/M - a fully coupled thermo-hydraulic model with mechanical coupling, which can be used to simulate non-isothermal moisture transport processes and the corresponding swelling effects. 

Recently, Fang et al. [25] and Rout and Jakobsen [66] extended the basic two-zone model for simulating non-isothermal CO2 capture processes by including the corresponding differential heat balances in terms of temperature. Moreover, Rout and Jakobsen [66] did also include transient terms in the model in order to enable simulations of the dynamic SE-SMR process. 

Figure 6-5b Temperature versus time in an adiabatic batch reactor. Fig ure 6-5. Simulation of a non-isothermal batch reactor.

Simulation of a non-isothermal reaction in a batch reactor involving the hydrolysis of acetylated castor oil... 

K. Ohno, H. Trinkaus, H. Muller-Krumbhaar. Simulation of non-isothermal nucleation. J Cryst Growth 99 68, 1990. 

The objectives of this presentation are to discuss the general behavior of non isothermal chain-addition polymerizations and copolymerizations and to propose dimensionless criteria for estimating non isothermal reactor performance, in particular thermal runaway and instability, and its effect upon polymer properties. Most of the results presented are based upon work (i"8), both theoretical and experimental, conducted in the author s laboratories at Stevens Institute of Technology. Analytical methods include a Semenov-type theoretical approach (1,2,9) as well as computer simulations similar to those used by Barkelew LS) ... 

The most comprehensive simulation of a free radical polymerization process in a CSTR is that of Konopnicki and Kuester (15). For a mechanism which includes transfer to both monomer and solvent as well as termination by combination and disproportionation they examined the influence of non-isothermal operation, viscosity effects as well as induced sinuoidal and square-wave forcing functions on initiator feed and jacket temperature on the MWD of the polymer produced. 

Energy balances are formulated by following the same set of guidelines as those given in Sec. 1.2.2 for mass balances. Energy balances are however considerably more complex, because of the many processes which cause temperature change in chemical systems. The treatment considered here is somewhat simplified, but is adequate to understand the non-isothermal simulation examples. The various texts cited in the reference section, provide additional advanced reading in this subject. 

The coupling of the component and energy balance equations in the modelling of non-isothermal tubular reactors can often lead to numerical difficulties, especially in solutions of steady-state behaviour. In these cases, a dynamic digital simulation approach can often be advantageous as a method of determining the steady-state variations in concentration and temperature, with respect to reactor length. The full form of the dynamic model equations are used in this approach, and these are solved up to the final steady-state condition, at which condition... 

Sklavounos, S. and Rigas, F., Simulation of Coyote series trials—Part I CFD estimation of non-isothermal LNG releases and comparison with box-model predictions, Chem. Eng. Sci., 61,1434, 2006. 

Xu, T., E.L. Sonnenthal, N. Spycher and K. Pruess, 2004, TOUGHREACT user s guide A simulation program for non-isothermal multiphase reactive geochemical transport in variably saturated geologic media. Report LBNL-55460, Lawrence Berkeley National Laboratory, Berkeley, California. 

The cyclic voltammograms of these systems display quasi-reversible behavior, with AEv/v being increased because of slow electrochemical kinetics. Standard electrochemical rate constants, ( s,h)obs> were obtained from the cyclic voltammograms by matching them with digital simulations. This approach enabled the effects of IR drop (the spatial dependence of potential due to current flow through a resistive solution) to be included in the digital simulation by use of measured solution resistances. These experiments were performed with a non-isothermal cell, in which the reference electrode is maintained at a constant temperature... 

Using Equations 5.53-5.56 a three-dimensional non-isothermal simulation of a typical IP process has been performed using a finite element control volume technique [31,34-36], The density specific heat and thermal conductivity of the resin and reinforcement used in the simulations are given in Table 5.1. 

The catalyst intraparticle reaction-diffusion process of parallel, equilibrium-restrained reactions for the methanation system was studied. The non-isothermal one-dimensional and two-dimensional reaction-diffusion models for the key components have been established, and solved using an orthogonal collocation method. The simulation values of the effectiveness factors for methanation reaction Ch4 and shift reaction Co2 are fairly in agreement with the experimental values. Ch4 is large, while Co2 is very small. The shift reaction takes place as direct and reverse reaction inside the catalyst pellet because of the interaction of methanation and shift reaction. For parallel, equilibrium-restrained reactions, effectiveness factors are not able to predict the catalyst internal-surface utilization accurately. Therefore, the intraparticle distributions of the temperature, the concentrations of species and so on should be taken into account. 

The work by Osswald et.al [12] was done to understand this phenomenon. To simulate the effect shown in the photograph, they used the two-dimensional mesh and processing conditions presented in Fig. 9.23. Note that in order to better see the set-up and results, the mesh is shown distorted in the thickness direction of the charge. Since the thickness-to-length (L/D) ratio is very small, the heat transfer in the non-isothermal solution reduces to a ID problem, and was solved using the finite difference technique. 

O.A. Estrada, I.D. Lopez-Gomez, C. Roldan, M. del P. Noriega, W.F. Florez, and T.A. Osswald. Numerical simulation of non-isothermal flow of non-newtonian incompressible fluids, considering viscous dissipation and inertia effects, using radial basis function interpolation. Numerical Methods for Heat and Fluid Flow, 2005. 

Fig. 10.48 Numerical simulation results of nonisothermal flow of HDPE, Melt Flow Index MFI = 0.1 melt obeying the Carreau-Yagoda model for a typical FCM model wedge of e/h — 3 and =15. (a) Velocity (b) shear rate and (c) temperature profiles [Reprinted by permission from E. L. Canedo and L. N. Valsamis, Non Newtonian and Non-isothermal Flow between Non-parallel Plate - Applications to Mixer Design, SPE ANTEC Tech. Papers, 36, 164 (1990).]...

If the rate sensitivity analysis is carried out over a non-isothermal oscillatory trace, then it is possible to see how certain reactions, in particular radical termination reactions and the reactions of water, become important at high temperatures and high conversions. The highest number of reactions is selected at the peak maximum where the temperature rises above 2000 K. All reactions required by the non-isothermal analysis, reactions 2-10, 13, 14, 16, 22-29, 35 and 45, were featured in one of the isothermal mechanisms. Therefore, it is possible to produce a reduced scheme for a non-isothermal simulation from an isothermal analysis provided the full... 

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