Fire in large-volume buildings poses separate and distinct challenges from compartmented spaces.In particular,the risk it poses on life safety is mostly due to the smoke it produces,its effects on the evacuation proce...Fire in large-volume buildings poses separate and distinct challenges from compartmented spaces.In particular,the risk it poses on life safety is mostly due to the smoke it produces,its effects on the evacuation process,and how it can affect the firefighters when they approach the building to fight the fire and rescue the occupants.This is why smoke control in large-volume enclosures is of utter importance for life safety,property protection and business continuity.This research presents an experimental and numerical study of the smoke dynamics from four fire sources(combined heat release rate of 5.2 MW)with different ignition times and under transient ventilation conditions,inside a 20 m high cubic atrium.Temperature measurements in the plume and close to the walls have been recorded using 59 thermocouples.The data was used in the determination of the smoke layer interface height,with the least-square and the N-Percent methods.Results show that significantly worse conditions are induced by multiple sources than those in a single fire of equal power.The results have been obtained using the computational fluid dynamics code FDS(Fire Dynamics Simulator,v6.7.1).The comparison shows that in the far field the temperature predictions are accurate inside the smoke layer(10 m and 15 m)with discrepancies lower than 10%,whereas higher significant discrepancies were observed at the smoke layer interface,i.e.5 m high,with discrepancies up to 20%.Furthermore,a grid analysis has been performed showing that grid resolutions,D*/δ,based on the global HRR of the fire might be sufficient to predict the fire induced conditions far from the fire.The analysis confirmed the applicability of FDS to the assessment of the smoke dynamics under complex fire conditions away from flames.Ultimately,the present work shows the importance of considering fires with multiple sources due to the faster smoke production compared with single fires.展开更多
In the present study we have explored the time dependent combined convectional flow on a rotating cone in a rotating Jeffrey fluid with the combined effects of heat and mass transfer.The governing equations of motion,...In the present study we have explored the time dependent combined convectional flow on a rotating cone in a rotating Jeffrey fluid with the combined effects of heat and mass transfer.The governing equations of motion,energy and mass transfer for unsteady flow are presented and simplified using similar variables.The reduced coupled nonlinear differential equations are solved analytically with the help of strong analytical technique homotopy analysis method.The heat transfer analysis for prescribed wall temperature is considered.Numerical results for Nusselt number and Sherwood number have computed and discussed.The physical features of pertinent parameters are discussed by plotting the graphs of velocity,heat transfer,concentration,skin friction,Nusselt number and Sherwood number.展开更多
Hydrocyclones are widely used in industry, of which the geometrical design using CFD techniques is gaining more popularity in recent years. In this study, the Euler-Euler approach and the Reynolds stress model are app...Hydrocyclones are widely used in industry, of which the geometrical design using CFD techniques is gaining more popularity in recent years. In this study, the Euler-Euler approach and the Reynolds stress model are applied to simulate the liquid-solid flowfield in a hydrocyclone. The methodology is validated by a good agreement between experimental data and numerical results. Within the research range, the simulation indicates that the liquid-solid separation mainly occurs in the conical segment, and increasing conical height or decreasing cylindrical height helps to improve the grade efficiencies of solid particles. Based on these results, two of the same hydrocyclones are designed and installed in series to establish a liquid-solid separation system. Many experiments are then conducted under different conditions, in which the effects of the water cut and the second hydrocyclone on the separation are investigated. The results also confirm that smaller solid particles are more susceptible to the inlet conditions, and the second hydrocyclone plays a more important role as the water cut reduces.展开更多
An analysis has been carried out to study the effects of radiation absorption and firstorder chemical reaction on unsteady mixed convective flow of a viscous incompressible electrically conducting fluid through a poro...An analysis has been carried out to study the effects of radiation absorption and firstorder chemical reaction on unsteady mixed convective flow of a viscous incompressible electrically conducting fluid through a porous medium of variable permeability between two long vertical non conducting wavy channels in the presence of heat generation.The unsteadiness in the flow is due to traveling thermal wave imposed on the walls.The governing equations are solved subject to the relevant boundary conditions with the assumption that the solution consists of a mean part and a perturbed part.The zeroth-order,the first order and the total solution of the problem are numerically evaluated and displayed graphically for pertinent parameters.This model finds applications in studying fixed-bed catalytic reactors and packed bed heat exchangers.展开更多
文摘Fire in large-volume buildings poses separate and distinct challenges from compartmented spaces.In particular,the risk it poses on life safety is mostly due to the smoke it produces,its effects on the evacuation process,and how it can affect the firefighters when they approach the building to fight the fire and rescue the occupants.This is why smoke control in large-volume enclosures is of utter importance for life safety,property protection and business continuity.This research presents an experimental and numerical study of the smoke dynamics from four fire sources(combined heat release rate of 5.2 MW)with different ignition times and under transient ventilation conditions,inside a 20 m high cubic atrium.Temperature measurements in the plume and close to the walls have been recorded using 59 thermocouples.The data was used in the determination of the smoke layer interface height,with the least-square and the N-Percent methods.Results show that significantly worse conditions are induced by multiple sources than those in a single fire of equal power.The results have been obtained using the computational fluid dynamics code FDS(Fire Dynamics Simulator,v6.7.1).The comparison shows that in the far field the temperature predictions are accurate inside the smoke layer(10 m and 15 m)with discrepancies lower than 10%,whereas higher significant discrepancies were observed at the smoke layer interface,i.e.5 m high,with discrepancies up to 20%.Furthermore,a grid analysis has been performed showing that grid resolutions,D*/δ,based on the global HRR of the fire might be sufficient to predict the fire induced conditions far from the fire.The analysis confirmed the applicability of FDS to the assessment of the smoke dynamics under complex fire conditions away from flames.Ultimately,the present work shows the importance of considering fires with multiple sources due to the faster smoke production compared with single fires.
文摘In the present study we have explored the time dependent combined convectional flow on a rotating cone in a rotating Jeffrey fluid with the combined effects of heat and mass transfer.The governing equations of motion,energy and mass transfer for unsteady flow are presented and simplified using similar variables.The reduced coupled nonlinear differential equations are solved analytically with the help of strong analytical technique homotopy analysis method.The heat transfer analysis for prescribed wall temperature is considered.Numerical results for Nusselt number and Sherwood number have computed and discussed.The physical features of pertinent parameters are discussed by plotting the graphs of velocity,heat transfer,concentration,skin friction,Nusselt number and Sherwood number.
文摘Hydrocyclones are widely used in industry, of which the geometrical design using CFD techniques is gaining more popularity in recent years. In this study, the Euler-Euler approach and the Reynolds stress model are applied to simulate the liquid-solid flowfield in a hydrocyclone. The methodology is validated by a good agreement between experimental data and numerical results. Within the research range, the simulation indicates that the liquid-solid separation mainly occurs in the conical segment, and increasing conical height or decreasing cylindrical height helps to improve the grade efficiencies of solid particles. Based on these results, two of the same hydrocyclones are designed and installed in series to establish a liquid-solid separation system. Many experiments are then conducted under different conditions, in which the effects of the water cut and the second hydrocyclone on the separation are investigated. The results also confirm that smaller solid particles are more susceptible to the inlet conditions, and the second hydrocyclone plays a more important role as the water cut reduces.
文摘An analysis has been carried out to study the effects of radiation absorption and firstorder chemical reaction on unsteady mixed convective flow of a viscous incompressible electrically conducting fluid through a porous medium of variable permeability between two long vertical non conducting wavy channels in the presence of heat generation.The unsteadiness in the flow is due to traveling thermal wave imposed on the walls.The governing equations are solved subject to the relevant boundary conditions with the assumption that the solution consists of a mean part and a perturbed part.The zeroth-order,the first order and the total solution of the problem are numerically evaluated and displayed graphically for pertinent parameters.This model finds applications in studying fixed-bed catalytic reactors and packed bed heat exchangers.
