Simulation of Chemical Reactors

This thesis consists basically of two parts. They are, however, interrelated by the fact that both parts concerns modelling of catalytic reaction systems and also by the fact that in both parts, spectral methods are used for simulation. The first part describes the numerical treatment of the dispersion model. The model is used to simulate a packed-bed reactor producing formaldehyde from methanol with an iron/ molybdenum catalyst. The self-adjoint partial differential operators involved in the model can, based on the Spectral theorem, be used to obtain infinite series of ordinary differential equations. After solving these equations, the solution to the original equation is obtained by summation. An advantage of the solution method is the possibility to obtain information regarding system behaviour, before actually simulating the system. This information can be extracted from the spectra of eigenvalues obtained after resolving the self- adjoint operators. The second part describes the simulation of heterogeneous/homogeneous combustion where the catalyst is located at the solid wall in contact whith a reactive gas flow. The full equation system, describing compressible fluid flow and chemical reactions, is solved. The numerical solution includes handling of non-linear differential operators which makes the simulation much more difficult than the one performed in part I. The impact of the convective/diffusive operators involved in the simulations become differently important in different areas in space, i.e. in areas far from the solid phase, the convective part will dominate whereas the diffusive part will dominate close to the solid. In order to resolve each contribution efficiently, a fractional step method was used whereby the equation systen was divided into hyperbolic, parabolic and reaction steps. The different steps were then calculated with spectral methods suitable for each specific type of equation system

The VINNOVA water mist research project : A description of the 500 m3 machinery space tests

This report describes water mist and water spray system tests inside a simulated machinery space. The tests were conducted inside a compartment measuring 8,0 m by 12,5 m with a ceiling height of 5,0 m. The corresponding volume was 500 m3. The walls and the ceiling were constructed from steel plates. The test compartment replicates an intermediate size machinery space compartment onboard a ship. Either diesel oil or heptane pool fires were used as the fire source. The fires had nominal heat release rates of 500 kW, 1 MW and 2 MW, respectively and were either fully exposed to the water spray or completely shielded by a horizontal obstruction steel plate measuring 2 m by 2 m. Three different systems were tested; (1) a water spray system flowing 500 L/min at 2 bar (this system was designed according to the SOLAS convention), (2) a low-pressure system flowing 97 L/min at 12 bar and (3) a high-pressure system flowing 60 L/min at 70 bar. In addition to the tests using these three systems, free burn tests were conducted inside the compartment. This report contains a description of the test set-up, its instrumentation, the fire test procedures and a limited presentation of the results. A more thorough analysis of the test results will be made in subsequent reports, articles and papers

Scaling of internal wall temperatures in enclosure fires

Physical scaling is an efficient and cost-effective modeling tool to be used in fire safety engineering. Scaling of internal wall temperatures was investigated in room fire tests in three different scales, that is, full scale (1:1), medium scale (1:2), and small scale (1:3.5). The fire sources were either placed at the center or in the corner of the enclosures. The measured time-dependent internal wall temperatures, incident heat fluxes, and gas temperatures in different scales are compared and analyzed. Test results show that the proposed scaling method is able to scale the internal wall temperatures (temperatures inside the walls) and incident heat fluxes well, especially in medium scale. </jats:p