Numerical Analysis of Smoke Confinement by Means of Air Curtains in High-Rise Buildings

2016 ◽  
Vol 858 ◽  
pp. 287-293 ◽  
Author(s):  
Xiao Tao Zhang ◽  
Chong Tan ◽  
Yu Shi Lu
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Discharge Coefficient ◽  
Wind Effect ◽  
Cfd Simulations ◽  
Air Curtain ◽  
High Rise ◽  
Discharge Velocity ◽  
Fire Effect ◽  
Computational Fluid Dynamics Cfd

As an effective approach to confine fire-induced smoke transportation, the application of air curtains is introduced in high-rise buildings during fire. A series of computational fluid dynamics (CFD) simulations were carried out for a full scale corridor in high-rise building, in which different factors such as air curtain discharge velocity (ACDV), human evacuation and pressure difference are considered. The results show that with the ACDV increasing, the smoke flowing resistance of air curtain is greater. The factor of evacuation cause significant impact on the efficiency of air curtain. Compared with the pressure difference caused by wind effect, the fire effect would lead to higher critical pressure difference and discharge coefficient.

Active Air Flow Control to Reduce Cavity Receiver Heat Loss

2015 ◽  
Author(s):  
J. Jack Zhang ◽  
John D. Pye ◽  
Graham O. Hughes
Keyword(s):  
Heat Loss ◽  
Thermal Power ◽  
Solar Thermal ◽  
Cfd Simulations ◽  
Air Curtain ◽  
Fluid Physics ◽  
Computational Fluid Dynamics Cfd ◽  
Optimum Velocity ◽  
Solar Receiver ◽  
Good Agreement

Convective air flows are a significant source of thermal loss from tubular cavity receivers in concentrating solar-thermal power (CSP) applications. Reduction in these losses is traditionally achieved by tailoring the cavity geometry, but the potential of this method is limited by the aperture size. The use of active airflow control, in the form of an air curtain, is an established practice to prevent infiltration of cold air through building doorways. Its application in reducing solar receiver convective heat loss is new. In this study, computational fluid dynamics (CFD) simulations are presented for the zero wind case, demonstrating that an optimised air curtain can readily reduce convective losses by more than 45%. A parametric investigation of jet direction and speed indicates that two distinct optimal air curtain flow structures exist. In the first, the jet reduces the size of the convective zone within the cavity by partially sealing the aperture. The optimum velocity range for this case occurs with a low strength jet. At higher jet speeds, the losses are generally set by the flow induced in the cavity and entrainment into the jet. However, a second optimal configuration is discovered for a narrow range of jet parameters, where the entrainment is reduced due to a shift in the stack neutral pressure level, allowing the jet to fully seal the cavity. A physical model is developed, based on the fluid physics of a jet and the ‘deflection modulus’ concept typically used to characterise air curtains in building heating and ventilation applications. The model has been applied to the solar thermal cavity case, and shows good agreement with the computational results.

CFD Analysis of Compressible Flow Across a Complex Geometry Venturi

2007 ◽  
Vol 129 (9) ◽  
pp. 1193-1202 ◽  
Author(s):  
Diego A. Arias ◽  
Timothy A. Shedd
Keyword(s):  
Compressible Flow ◽  
Discharge Coefficient ◽  
Static Pressure ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Turbulent Model ◽  
Cfd Simulations ◽  
Pressure Losses ◽  
Computational Fluid Dynamics Cfd ◽  
Fuel Tube

A commercial computational fluid dynamics (CFD) package was used to develop a three-dimensional, fully turbulent model of the compressible flow across a complex-geometry venturi, such as those typically found in small engine carburetors. The results of the CFD simulations were used to understand the effect of the different obstacles in the flow on the overall discharge coefficient and the static pressure at the tip of the fuel tube. It was found that the obstacles located at the converging nozzle of the venturi do not cause significant pressure losses, while those obstacles that create wakes in the flow, such as the fuel tube and throttle plate, are responsible for most of the pressure losses. This result indicated that an overall discharge coefficient can be used to correct the mass flow rate, while a localized correction factor can be determined from three-dimensional CFD simulations in order to estimate the static pressure at locations of interest within complex venturis.

Discharge Coefficients in Aerostatic Bearings With Inherent Orifice-Type Restrictors

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
S. H. Chang ◽  
C. W. Chan ◽  
Y. R. Jeng
Keyword(s):  
Film Thickness ◽  
Discharge Coefficient ◽  
Reynolds Equation ◽  
Orifice Diameter ◽  
Model Accuracy ◽  
Cfd Simulations ◽  
Flow Parameters ◽  
Computational Fluid Dynamics Cfd ◽  
Aerostatic Bearings ◽  
Conicity Angle

In aerostatic bearing analysis, determining film pressure by solving the Reynolds equation in a numerical model is more effective than conducting bearing experiments or performing computational fluid dynamics (CFD) simulations. However, the discharge coefficient of an orifice-type restrictor is generally a given number that dominates model accuracy. This study investigated the influence of geometry and flow parameters on this discharge coefficient. The results indicate that this discharge coefficient is sensitive to the orifice diameter and film thickness and that the effects of the supply pressure, bearing radius, supply orifice length, supply passage diameter, conicity depth, and conicity angle can be disregarded. This study also built a surrogate model of this discharge coefficient based on the orifice diameter and film thickness by using artificial neural networks (ANNs).

scholarly journals Impact of volume distribution on pedestrian wind environment in high-rise urban districts: a CFD study

2021 ◽  
Vol 2042 (1) ◽  
pp. 012064
Author(s):  
Milad Sadeghfar ◽  
Sadra Sahebzadeh
Keyword(s):  
Urban Design ◽  
Urban Areas ◽  
Volume Distribution ◽  
Cfd Simulations ◽  
Wind Environment ◽  
High Rise ◽  
Urban Districts ◽  
Computational Fluid Dynamics Cfd ◽  
Wind Comfort ◽  
The Impact

Abstract Pedestrian wind environment assessment is becoming an essential part of the urban design process especially in dense urban areas due to its ability to address the wind comfort/safety/health concerns in an early phase. In this paper, high-fidelity computational fluid dynamics (CFD) simulations, validated with experimental data, are performed on eight different designs in a generic urban layout to study the impact of volume distribution on pedestrian wind environment in high-rise urban districts. The results show that the blockage effects of the high-rise buildings decelerates the wind in the streets parallel to the flow while accelerating the flow in the streets perpendicular to the flow. This effect is evident up to a two block distance upstream of the high-rises. Furthermore, it is shown that consequent rows of high-rises in the downstream of the first row facing the wind flow have little effect on the upstream pedestrian wind; however, they have a significant role in the extent of affected areas downstream. The findings of this study provide further understanding about the impact of different volume distributions on pedestrian wind environment in high-rise urban districts and clarify their effect on wind safety and comfort.

scholarly journals Using CFD to Evaluate Natural Ventilation through a 3D Parametric Modeling Approach

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2197
Author(s):  
Nayara Rodrigues Marques Sakiyama ◽  
Jurgen Frick ◽  
Timea Bejat ◽  
Harald Garrecht
Keyword(s):  
Natural Ventilation ◽  
Parametric Modeling ◽  
Cfd Simulations ◽  
3D Design ◽  
Post Process ◽  
Test House ◽  
Model Set ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Passive Strategy

Predicting building air change rates is a challenge for designers seeking to deal with natural ventilation, a more and more popular passive strategy. Among the methods available for this task, computational fluid dynamics (CFD) appears the most compelling, in ascending use. However, CFD simulations require a range of settings and skills that inhibit its wide application. With the primary goal of providing a pragmatic CFD application to promote wind-driven ventilation assessments at the design phase, this paper presents a study that investigates natural ventilation integrating 3D parametric modeling and CFD. From pre- to post-processing, the workflow addresses all simulation steps: geometry and weather definition, including incident wind directions, a model set up, control, results’ edition, and visualization. Both indoor air velocities and air change rates (ACH) were calculated within the procedure, which used a test house and air measurements as a reference. The study explores alternatives in the 3D design platform’s frame to display and compute ACH and parametrically generate surfaces where air velocities are computed. The paper also discusses the effectiveness of the reference building’s natural ventilation by analyzing the CFD outputs. The proposed approach assists the practical use of CFD by designers, providing detailed information about the numerical model, as well as enabling the means to generate the cases, visualize, and post-process the results.

scholarly journals Dependence of the Flue Gas Flow on the Setting of the Separation Baffle in the Flue Gas Tract

2021 ◽  
Vol 11 (7) ◽  
pp. 2961
Author(s):  
Nikola Čajová Kantová ◽  
Alexander Čaja ◽  
Marek Patsch ◽  
Michal Holubčík ◽  
Peter Ďurčanský
Keyword(s):  
Particulate Matter ◽  
Flue Gas ◽  
Gas Flow ◽  
Negative Impact ◽  
Combustion Process ◽  
Cfd Simulations ◽  
Piv Measurements ◽  
Computational Fluid Dynamics Cfd ◽  
Particle Imaging ◽  
Combustion Of Solid Fuels

With the combustion of solid fuels, emissions such as particulate matter are also formed, which have a negative impact on human health. Reducing their amount in the air can be achieved by optimizing the combustion process as well as the flue gas flow. This article aims to optimize the flue gas tract using separation baffles. This design can make it possible to capture particulate matter by using three baffles and prevent it from escaping into the air in the flue gas. The geometric parameters of the first baffle were changed twice more. The dependence of the flue gas flow on the baffles was first observed by computational fluid dynamics (CFD) simulations and subsequently verified by the particle imaging velocimetry (PIV) method. Based on the CFD results, the most effective is setting 1 with the same boundary conditions as those during experimental PIV measurements. Setting 2 can capture 1.8% less particles and setting 3 can capture 0.6% less particles than setting 1. Based on the stoichiometric calculations, it would be possible to capture up to 62.3% of the particles in setting 1. The velocities comparison obtained from CFD and PIV confirmed the supposed character of the turbulent flow with vortexes appearing in the flue gas tract, despite some inaccuracies.

scholarly journals Effect of Roof Cooling and Air Curtain Gates on Thermal and Wind Conditions in Stadiums for Hot Climates

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3941
Author(s):  
Fangliang Zhong ◽  
Hassam Nasarullah Chaudhry ◽  
John Kaiser Calautit
Keyword(s):  
Energy Consumption ◽  
Electric Energy ◽  
Building Energy ◽  
Future Research ◽  
World Cup ◽  
Air Curtain ◽  
Hot Air ◽  
Computational Fluid Dynamics Cfd ◽  
Energy Consumptions ◽  
The Spectator

To host the 2022 FIFA World Cup, Qatar is facing the greatest challenge in balancing the energy consumptions for cooling the stadiums and the thermal comfort for both players and spectators. Previous studies have not considered using a combined configuration of air curtain and roof cooling supply slot in stadiums to prevent the infiltration of outside hot air and reduce the cooling system’s energy consumption. This paper presents a Computational Fluid Dynamics (CFD) study of thermal and wind modeling around a baseline stadium and simulates the cooling scenarios of air curtains and roof cooling along with the energy consumption estimations for the World Cup matches using Building Energy Simulation (BES). Sensitivity analysis of different supply speeds and supply temperatures of air curtain gates and roof cooling was carried out, and the results showed that scenario six, which provides supply air of 25 m/s and 20 m/s at the roof and air curtain gates with a supply temperature of 10 °C, demonstrates optimal thermal performances on both the spectator tiers and the pitch. Compared with the baseline stadium performance, the average reductions in temperature on the pitch and spectator tiers under scenario six could reach 15 °C and 14.6 °C. The reductions in the Predicted Percentage of Dissatisfied values for the upper and lower tiers as well as the pitch were 63%, 74%, and 78%. In terms of the estimated energy consumptions, scenario six would consume electric energy per match at a rate of 25.5 MWh compared with 22.8 MWh for one of the stadiums in the 2010 South Africa World Cup and 42.0 MWh for the 2006 Germany World Cup. Future research is recommended to explore the influence of supply angle on air curtain gates and roof cooling supply slots’ performances.

Numerical Analysis of Elevator Piston Effect on Building Airflow for an Air-Conditioned High-Rise Building in Winter

2014 ◽  
Vol 1008-1009 ◽  
pp. 1068-1074 ◽  
Author(s):  
Yan Wang ◽  
Yan Ling Guan ◽  
Yuan Sheng Yin
Keyword(s):  
Pressure Distribution ◽  
Upward Movement ◽  
Piston Effect ◽  
Air Conditioning System ◽  
Security Issues ◽  
High Rise ◽  
Computational Fluid Dynamics Cfd ◽  
Elevator Door ◽  
Mesh Technique ◽  
Storey Building

A model of a 24-storey building (94.5m high) with air-conditioning system was developed to analyze the elevator piston effect on building airflow by dynamic mesh technique of computational fluid dynamics (CFD). The results of the pressure distribution and airflow paths show that with the upward movement of elevator cabs, due to the elevator piston effect, changes in the pressure distribution and airflow paths occur in all the building; the pressure difference across the elevator door is enlarged, which is likely to cause some security issues; but the air exfiltration rate is hardly affected.

scholarly journals Investigations of Inducers Operating With High Rotational Speed

2018 ◽  
Vol 141 (4) ◽  
Author(s):  
Björn Gwiasda ◽  
Matthias Mohr ◽  
Martin Böhle
Keyword(s):  
Rotational Speed ◽  
Test Bench ◽  
Pressure Rise ◽  
Working Fluid ◽  
Cfd Simulations ◽  
High Rotational Speed ◽  
Rotating Speed ◽  
Performance Pressure ◽  
Computational Fluid Dynamics Cfd ◽  
Suction Performance

Suction performance, pressure rise, and efficiency for four different inducers are examined with computational fluid dynamics (CFD) simulations and experiments performed with 18,000 rpm and 24,000 rpm. The studies originate from a research project that includes the construction of a new test bench in order to judge the design of the different inducers. This test bench allows to conduct experiments with a rotational speed of up to 40,000 rpm and high pressure ranges from 0.1 bar to 40 bar with water as working fluid. Experimental results are used to evaluate the accuracy of the simulations and to gain a better understanding of the design parameter. The influence of increasing the rotating speed from 18,000 rpm to 24,000 rpm on the performance is also shown.

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