Electric furnace, modelling

Fig. 10.15 Simulated temperature distribution at the electrolyte during an operation of the singlecell stack model. The stack is assumed to be operated at 1000°C in an electric furnace.

Apparatus and Method. The fixed-bed coluiiui was a 316 stainless steel tube, with an inside diameter of 1.09cm and a length of 40cm. The temperature of the column was maintained with an electric furnace located at its outer wall. Concentrations of NO and NO2 that exhausted from the bypass line and adsorption coluriui were analyzed by using a chemiluminescent NO, analyzer (Thermo Environmental Instruments Inc., model 42C). 

Helium leak tests were carried out under load pressure up to 4 MPa and surface temperature of the models up to 500°C. All cormections were installed in a vacuum electric furnace, and leak rates were measured with a helium leak detector. Table 2 shows the leak rates obtained at 500°C in the third times at the heat cycle up to 5()()°C, and Table 3 obtained under 2()°C after the leak measurement at 500°C shown in Table 2. In these tables, line loads and seating stresses (tightening forces) are also indicated. As seen these tables, although the tightening forces under 500°C decreased down to less than... 

Accretion management by CFD modeling of heat dissipation (McMaster University) and electric furnace control strategies (Mintek)... 

The flow of heat and momentum in the electric furnace was assumed to occur under steady state conditions, so that only steady-state solutions were sought. Further, the flow was mainly laminar, but where it was turbulent the conventional k-e model (9) was applied. Hence, the steady-state transport equations for momentum and heat were solved in three dimensions. The generalized steady-state three-dimensional equation for a conserved variable, q>, is ... 

The authors are very grateful to Dr. J. Dableh for his help in developing the electrical model of the furnace. The many fruitful discussions with Dr. G.G. Richards and Mr. A. Hall of Cominco Ltd. on all aspects of the electric furnace operation are greatly predated. The financial support of CANMET and Cominco Ltd. for this project is also gratefiilly acknowledged. Finally, the authors would like to thank Cominco and Snamprogetti for reviewing the final paper. 

Fig. 10.1 Metal atom reactor. A - Glass reaction vessel. B - Electron beam furnace, model EBSl, G.V. Planer Ltd. C - Vapour beam of metal atoms. D - Co-condensate of metal and substrate vapours. E - Heat shield. F - Furnace cooling water pipes. G - Electrical lead for substrate solution dispersion device. H - Furnace electrical leads. J - Substrate inlet pipe (vapour). K - Substrate inlet pipes (solution). M - Rotation of reaction vessel. N - To vacuum rotating seal, service vacuum lead troughs and pumping systems. 0-Level of coolant (usually liquid nitrogen). P-Capped joint for product extraction. 0-Substrate vapour dispersion device. R-Substrate vapour beam. (From Green, M.L.H., 1980, /. Organomet. Chem., 300, 119.)...

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

The Limiting Case of a Transparent Medium For the special case of a transparent medium, K = 0, many practical engineering applications can be modeled with the zone method. These include combustion-fired muffle furnaces and electrical resistance furnaces. 

Approximately 2 g. of the desired model compounds were heated in a stream of dry nitrogen (pyrolysis) or of a mixture of 92 % nitrogen and 8% oxygen (gasification). The sample was placed in a combustion boat of porcelain. The boat was heated in a quartz tube which was placed in an electrically heated furnace. The furnace was heated with 50 C/min to the desired temperature which was kept for 30 minutes, and the sample was cooled under nitrogen and weighed. The fraction of solid residue left in the vessel was calculated and analysed on its chlorine content. 

Additional parameters specified in the numerical model include the electrode exchange current densities and several gap electrical contact resistances. These quantities were determined empirically by comparing FLUENT predictions with stack performance data. The FLUENT model uses the electrode exchange current densities to quantify the magnitude of the activation overpotentials via a Butler-Volmer equation [1], A radiation heat transfer boundary condition was applied around the periphery of the model to simulate the thermal conditions of our experimental stack, situated in a high-temperature electrically heated radiant furnace. The edges ofthe numerical model are treated as a small surface in a large enclosure with an effective emissivity of 1.0, subjected to a radiant temperature of 1 103 K, equal to the gas-inlet temperatures. 

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