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Abstract
The thermal decomposition of an explosive material is accompanied by generation of a certain amount of heat and, under certain conditions, can lead to the well-known phenomena of self-ignition. Therefore, it is of great importance to predict whether or not an explosive material will ignite under given conditions (specimen mass and shape, surrounding temperature, etc.). An own computer program named THERMEX, for studying thermal ignition phenomena, is discussed in this paper. The program uses the finite difference method to describe the reactive heat conduction phenomena in infinite slab, cylindrical, and spherical geometry of explosive materials. The analysis of the stability requirements of the finite difference method applied in the program is carried out. The program is tested by the comparison of calculated results with the results of calculation by other authors. Reasonable agreement was found under identical computational conditions.
Abstract
A kinetic model for the reaction sintering of oxide ceramics in the system Al2O3–SiO2–ZrO2 using mixtures of intermetallic compounds is presented. A 2D finite-difference model is developed to describe the exothermic gas-solid reactions taking place during the firing of ZrAl3/ZrSi2 powder compacts. The model accounts for the oxidation kinetics of the powder particles, as well as the consumption and diffusion of gaseous oxygen through the porous matrix. Additionally, possible changes in the pore structure of the green body due to the oxidation reactions and sintering effects are incorporated in the model. The resulting differential equations are coupled with a two-dimensional Fourier heat balance equation leading to a system of nonlinear partial differential equations, which is solved by the numerical method of lines. The influence of different processing parameters like sample composition and heating cycle on the reaction sintering process is investigated and the model-predicted reaction behaviour is compared to experimental results.
Abstract
The spiral plate heat exchanger (SHE) is widely used in plenty of industrial services in full counter current flow liquid-liquid heat exchange. We have produced a thermal modelling of the heat exchanges in both steady-state and time dependent cases with 2D spiral geometry, allowing computation with different materials, forced convective heat transfer models in turbulent flow and geometrical parameters options. We will display here some results in steady-state conditions in order to improve the exchanger performances.
method 2.1 Finite difference method (FDM) The explanation of the physical principles governing space- and time-dependent issues is typically represented in terms of partial differential equations, which are frequently difficult to solve analytically
Abstract
The adsorption coefficient is the fundamental parameter characterizing activated charcoal"s ability to adsorb 222Rn. The adsorption coefficient is determined for 222Rn activated charcoal detectors. In addition, a diffusion and adsorption model is developed for the transport of 222Rn in a porous bed of activated charcoal. These processes can be described by parabolic second order differential equation. The equation is numerically solved using the finite differences method. With this model, the 222Rn activity adsorbed in the detector is calculated for diverse situations.
Calculations by Finite Differences, International Text Book, 1961 (as cited in: I. Onaka, Introduction to Heat Transfer and Solidification Analysis, Maruzen, Tokyo 1986, in Japanese).
A new L 2 norm joint inversion technique is presented and combined with the series expansion inversion method applied for different simulated erroneous Vertical Electric Sounding (VES) data sets over a complicated two dimensional structure. The applied joint inversion technique takes into consideration the complete form of the likelihood function. As a result there is no need to apply input weights to the individual objective functions. The model consists of three layers with homogeneous resistivities. The first layer boundary is a horizontal plane, the other is a two dimensional laterally varying surface. For the VES inversion the exact data sets were calculated by finite difference method, one in strike direction and the other in dip direction. These data sets were contaminated with normally distributed random errors. During inversion the second layer boundary function was determined. For comparison individual and joint inversion examples were calculated for the two data sets. The best model parameter estimate result was produced by the method of automated weighting.
