Browsing by Author "Gohari Darabkhani, Hamidreza"
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Item Open Access Assessment of a common nonlinear eddy-viscosity turbulence model in capturing laminarization in mixed convection flows(Taylor and Francis, 2015-11-30) Keshmiri, Amir; Revell, Alistair; Gohari Darabkhani, HamidrezaLaminarization is an important topic in heat transfer and turbulence modeling. Recent studies have demonstrated that several well-known turbulence models failed to provide accurate prediction when applied to mixed convection flows with significant re-laminarization effects. One of those models, a well-validated cubic nonlinear eddy-viscosity model, was observed to miss this feature entirely. This paper studies the reasons behind this failure by providing a detailed comparison with the baseline Launder–Sharma model. The difference is attributed to the method of near-wall damping. A range of tests have been conducted and two noteworthy findings are reported for the case of flow re-laminarization.Item Open Access Kinetic simulation of a 100kWth oxy-combustor using Aspen Plus(C2ES, 2013-12) Jurado Pontes, Nelia; Gohari Darabkhani, Hamidreza; Anthony, Edward J.; Oakey, JohnOxy-fuel combustion is a clean coal technology based on firing fuel in an enriched oxygen atmosphere to obtain high CO2 concentrations in the exhaust gas. Experimental tests were performed at Cranfield University using a 100kWth retrofitted oxy-combustor. In parallel, a kinetic simulation model using Aspen Plus was designed and validated to serve as a computer tool to predict the behaviour of the oxy-combustion process for a wide range of fuels and conditions. The main input parameters varied in the simulation study were: fuel type (El Cerrejon coal, Daw Millcoal, Cereal Co-product biomass, and coal/biomass blends); percentage of recycled flue gas (55, 60,and 65%); type of recycled flue gas (wet or dry); percentage of excess oxygen (0 and 5%), and the amount of air ingress into the process (0, 2, 10, and 18% of the total flue gas fed to the oxycombustor).The last input condition, percentage of air ingress, is of greater importance as a result of the unit being a retrofitted oxy-combustor; for which air ingress is more probable and this represents a situation likely to be an issue for any boiler retrofitted for oxyfuel firing. Results from the simulations as well as the definition of the operating conditions that best represents the behaviour of the rig are presented.Item Open Access Simulation of oxy-combustion co-firing coal and biomass with ASU and steam turbine using Aspen Plus(International Centre for Sustainable Carbon, 2013-05) Jurado Pontes, Nelia; Gohari Darabkhani, Hamidreza; Oakey, John