Smoke Exhaust System Research Articles

Egress Safety for STUDIO Residential Buildings

In recent years, the number of studio residential buildings has increased significantly in Korea, as well as in many other countries, due to changes in living patterns. In Korea especially, there have been many fire accidents in studio residential buildings, which have caused a huge number of casualties and property damages, because the buildings were not adequately equipped for firefighting. In this study, the egress safety of a typical studio residential building in Korea is analyzed. Fire simulations were performed with variables of the fire location and the capacity of the smoke exhaust system to estimate the available safe egress time (ASET); egress simulations were also performed with the variable of egress delay time, and the required safe egress time (RSET) was determined. Then, the egress safety was evaluated, and the criteria for egress safety evaluation were proposed based on the simulation results. A studio residential building with a floor plan different from the prototype was used to validate the proposed egress safety criteria. Finally, a simple evaluation model is presented to estimate the required safe egress time (RSET) without simulation and to examine the impact of bottlenecks.

Study on the Natural Smoke Exhaust Performance of Board-Coupled Vertical Shaft in High-Altitude Tunnel Fires

Vertical shaft natural ventilation is a common smoke exhaust method in highway tunnel fires. This study investigated the vertical shaft natural smoke exhaust work in highway tunnel fires with the effect of multiple factors through numerical simulation. Using the analysis of the flow field of smoke in nearby areas of the vertical shaft and the quantitative calculation of the gas exhausted through the vertical shaft, considering the impact of shaft division and board height, an optimal vertical shaft arrangement was proposed, and the working conditions of this arrangement in low-pressure environments were discussed. The results show that dividing a single large vertical shaft into multiple small vertical shafts and appropriately adjusting the board height can reduce the incidence of vertical shaft plug holes and significantly enhance the vertical shaft smoke exhaust performance. Meanwhile, the board-coupled shaft (BCS) has excellent working ability in low-pressure environments, and when pressure drops, smoke exhaust efficiency will improve. This research offers a foundation and reference value for improving the vertical shaft smoke exhaust system in highway tunnels.

A simplified mathematical modeling approach for thermal runaway of Li(Ni0.8Co0.1Mn0.1)O2 pouch cells based on thermal runaway experimental data

Currently, the numerical modeling methods used to characterize the thermal runaway and propagation mechanisms in NCM811 pouch batteries still face numerous challenges. This is primarily due to the uncertainties in thermal runaway reactions and the immense computational demands encountered when modeling begins at the granular level of the cell. To address this issue, this study designed a series of experiments for an NCM811 pouch battery. By employing experimental data, reasonable assumptions were made regarding the combined effects of solid-state thermal conduction, electrochemical heating, and fluid-solid heat transfer through gas jet streams. A simplified thermal runaway mathematical modeling method based on experimental data was proposed, effectively tackling the problem. This framework was then applied to thermal runaway experiments on a single NCM811 battery used in this study, providing essential input parameters for three-dimensional numerical modeling of modules composed of multiple batteries in multiphysics simulation software. The simulation results derived from the proposed method were in good agreement with experimental data. This study can characterize the thermal runaway and thermal propagation characteristics of battery modules using single-cell thermal runaway experiments. Moreover, the proposed modeling approach not only predicted the experimental outcomes of the NCM811 pouch battery with reasonable accuracy but also provided smoother data, elucidating the highly fluctuating trends observed in experimental data. This method also offers guidance for designing fire prevention and smoke exhaust systems for battery packs. This study presents a novel approach for the mathematical modeling of thermal runaway and thermal propagation in battery modules using NCM811 pouch batteries, contributing to the ongoing development of lithium-ion battery module design.

Numerical Study on the Efficiency of the Point Smoke Exhaust System in V-shaped Urban Underground Road Tunnel

In order to study the exhaust effect of the point smoke exhaust system in V-shaped urban underground tunnel with different structures, effects of the slope differences on both sides of the slope changing point and the operating mode of the exhaust vent on the smoke spread distance, temperature at the height of 2 m above the road and the ceiling temperature were studied by the numerical method. The research results show that for the symmetric V-shaped tunnel, smoke can be controlled in the required range, but for asymmetric V-shaped tunnel with the slope difference on both sides, smoke cannot be easily controlled, ventilation supply is needed to improve the smoke exhaust efficiency. Point smoke exhaust system cannot effectively reduce the maximum temperature of the ceiling above the fire. When the fire source power is large, for the symmetrical V-shaped tunnel with a small slope, some fire prevention measures must be taken to protect the ceiling partition. For the asymmetric V-shaped tunnel, two exhaust vents opened on the small slope side and four opened on the large slope side are suggested for the occupant safe evacuation in tunnel.

Influence of Smoke Exhaust Volume and Smoke Vent Layout on the Ceiling Centralized Smoke Exhaust Effect in Tunnel Fires

This research focuses on the impact of smoke exhaust volume and smoke vent layout, which are two crucial factors affecting the smoke control efficiency in tunnels, on the smoke exhaust effect in tunnel fires. Numerical simulation methods are employed to investigate the impact of changing the smoke exhaust volume and the smoke vent number on the smoke exhaust performance in a curved tunnel with a ceiling centralized smoke exhaust system. This research primarily examines the length of the smoke distribution, the smoke temperature under the ceiling, the vertical visibility, and the exhausted smoke mass flow rate. The findings indicate that, in a tunnel with a single-side ceiling centralized smoke exhaust mode, an imbalance in smoke distribution occurs between the upstream and downstream of the fire source. The upstream area experiences a higher amount of smoke, while the downstream area has thinner smoke. Increasing the smoke exhaust volume yielded positive effects on smoke control, as evident in the reduced the smoke spread range, and improved the smoke exhaust efficiency. The influence of changing smoke vent number on the smoke exhaust effect was dependent on the smoke exhaust volume. When the smoke exhaust volume was excessive, altering the number of smoke vents had a minimal impact on smoke exhaust, while in cases with small smoke exhaust volumes, changes in smoke vent numbers obviously influenced the smoke control effect. Therefore, selecting an appropriate smoke exhaust volume and raising the smoke vent number can effectively optimize the performance of the ceiling centralized smoke exhaust system.

Study on Smoke Spreading Characteristics of Highway Tunnel Fire

In the event of a fire in a road tunnel, the effect of natural smoke exhaust alone is far inferior to that of mechanical smoke exhaust. Study of the characteristics of the flux of smoke gases inside the tunnel with the use of mechanical exhausts in case of sudden fire in road tunnels by means of specific model simulation methods, specific analysis by setting fixed exhaust spacing and different emission volumes, and the addition of fine water mist is studied. The results show that: when the exhaust vent spacing is 30m, the smoke exhaust volume in 30m³/s, 40m³/s, 50m³/s mechanical smoke exhaust device under the action of temperature, CO concentration and visibility will not affect the safe evacuation of the personnel, but taking into account the control of smoke propagation and economic reasonableness, the smoke exhaust volume of 40m³/s is better than the smoke exhaust volume of 30m³/s and 50m³/s. Under the coupling effect of mechanical smoke exhaust system and fine water mist, the spread of smoke in the tunnel can be controlled within a certain range and the internal temperature of the tunnel can be reduced. It can provide a certain basis for the design of the exhaust vent and the setting of water mist in the future.

A Prediction Model for Ceiling Temperature in the Ultra-Wide Road Tunnel Fire with Lateral Smoke Exhaust

ABSTRACT Ultra-wide road tunnel plays an important role in relieving traffic pressure. The lateral smoke exhaust system was used to control the fire smoke in the ultra-wide road tunnel. This study conducted a series of experiments in a 1:20 scale tunnel to explore the effects of lateral smoke exhaust volume and heat release rate (HRR) on the ceiling temperature in the ultra-wide road tunnel. The results demonstrate that the ceiling temperature in the ultra-wide road tunnel with the lateral smoke exhaust is obliquely distributed along the longitudinal direction, which is different from the other smoke exhaust modes. The lateral smoke exhaust system can create a better evacuation environment for the tunnel space near the exhaust duct. As the HRR increases or the lateral smoke exhaust volume decreases, the ceiling temperature decays more slowly along the longitudinal direction of the tunnel. Finally, a longitudinal attenuation prediction model of the ceiling temperature is proposed based on a nondimensional analysis. The prediction model conforms to a double exponential function and is suitable for ultra-wide road tunnels with lateral smoke exhaust. Therefore, the research results of this study can provide references for ultra-wide road tunnel fire research and the design of lateral smoke exhaust systems.

Comparative Analysis of Korean and Japanese Standards for Natural Smoke Ventilation in Logistic Warehouses

This study investigated the design methodologies outlined in Korean and Japanese legislation, along with Japanese design guidelines, pertaining to natural smoke ventilation systems in logistics warehouses. Subsequently, we determined the effective area of the smoke exhaust system based on the combustible materials and building characteristics. Our findings indicated that the calculated effective area per the statutory standards of both nations was 10 m<sup>2</sup> and 20 m<sup>2</sup>, respectively. According to Japanese guidelines, the space accommodating the CUP ranged from 24.71 m<sup>2</sup> to 13.76 m<sup>2</sup> for floor heights between 7 to 16 m, while the space accommodating CEP ranged from 41.83 m<sup>2</sup> to 22.54 m<sup>2</sup>. Analyzing the quantity of smoke emitted through the calculated effective area, we observed that, when applying domestic legal standards, the smoke exhaust rate consistently remained lower than the plume flow rate. Conversely, under the Japanese standard, the smoke emission efficiency of the CUP loading warehouse surpassed that of smoke emission from 9 m to 16 m, while it was lower from 7 m to 8 m. Notably, the smoke exhaust rate consistently exceeded the generated smoke quantity in all instances within the effective area governed by the guidelines.

Study on smoke flow characteristics in immersed tunnel fires with lateral centralized exhaust: Considering the effect of the slope

In the case of fires in inclined immersed tunnels, smoke flow patterns differ from those of horizontal tunnels, and require a unique approach to lateral centralized smoke exhaust. In this study, we propose a prediction model for the exhausted mass flow rate near each vent and use Fire Dynamics Simulator (FDS) to analyze the flow field and components. Our findings indicate that temperature and smoke velocity distributions follow exponential decay with varying slopes, with exhaust efficiency and entrainment coefficient first increasing then decreasing at 1% and 2% slopes, and continuously decreasing at 3%, 4%, and 5% slopes. Only at a 6% slope can the smoke reach the nearest vent. Exhausted mass flow rate and exhaust volume have a positive correlation, and calculated values and simulated results agree well. This study can guide the design and management of lateral centralized smoke exhaust systems for inclined tunnels.

Numerical study on the influence of subway platform air curtains on smoke diffusion

To control longitudinal smoke spread and increase the time available for evacuation at subway platforms, this paper proposes a system for separating smoke on subway platforms using a combination of external air supply platform air curtains, stair (or escalator) air curtains, and a mechanical smoke exhaust system. In this paper, CFD simulations are conducted using Fire Dynamics Simulator (FDS) to investigate the impact of various air curtain speeds at a 20° angle on smoke dispersion. The results show that: (1) The system is effective and reasonable, which can effectively prevent longitudinal smoke diffusion in the platform. (2) For the 2.5 MW firepower, when the air curtain speed is between 3 m/s and 5 m/s, the protected area is not affected by smoke. The supplementary cold air from the air curtains mixed and dispersed the heat, leading to a decrease in the temperature of the suspended ceiling above the fire source by approximately one-third, to below 200 °C. (3) For the 5.0 MW firepower, when the air curtain speed is 4 m/s, the protected area is not affected by smoke. The enhanced impact of the air curtain on fire source combustion surpasses the cooling effect of supplementary air.

PROSPECTS FOR THE USE OF ACTIVE ASPIRATION ALARM SYSTEMS IN FIRE SAFETY SYSTEMS OF MANY-STOREYED HIGH BUILDINGS

At present, multi-story high-rise buildings are becoming one of the most widely used buildings in cities. Now it is very difficult to imagine urban architecture without them. The increase in the urban population in cities is the result of an increase in the level of urbanization. As a result, the price of land increases due to the lack of free land in cities. Thus, the construction of multi-story buildings has become an inevitable solution to this issue, but this, in turn, has led to new problems. Depending on the purpose, composition, and number of technical systems, multi-story buildings are complex engineering and technical objects. On the one hand, the use of engineering and technical systems leads to an increase in the standard of living of people living standards, but they are also the main causes of new problems. For example, high-rise buildings are quite large consumers of electrical energy, both as objects and as subjects of these buildings, and this, in turn, leads to an increase in the likelihood of a fire in them. To prevent such undesirable cases, one has to use fire safety systems, one of the components of building automation. One of the main responsibilities of fire safety systems is to determine the initial stage of ignition and quickly detect its source, only, in this case, it can be eliminated or at least localized. The life and property of people can be protected. The main purpose of this article is to consider the currently unused active aspiration system in multi-story high-rise buildings as an alternative to currently used systems to improve efficiency in terms of fire safety. The article includes the appointment of an active aspiration system, the principle of operation, and the main characteristics, and functions of those designed for early fire detection. In addition, several options and a comparative analysis of an active aspiration system are considered to create a highly efficient fire safety system for high-rise buildings. Keywords: fire protection systems, smoke exhaust systems, fire protection sensors, aspirator alarm systems, automatic building systems.

Full-scale experimental and theoretical study of an air leakage model and the applicable limit length for ceiling centralized smoke exhaust systems in tunnel fires

Based on the Jiangxinzhou Yangtze River Tunnel, this study investigated the air leakage of a ceiling-centralized smoke exhaust system through full-scale tests and theoretical analysis. The theoretical analysis established a functional relationship between the pressure of the exhaust vent and air leakage volume. The air leakage coefficient of the exhaust vent was defined. The exhaust vent air leakage coefficient, exhaust flue area, hydraulic diameter, resistance coefficient along the exhaust flue, and exhaust vent spacing were integrated to establish the exhaust flue air leakage coefficient. Through full-scale tests, the exhaust flue pressure and air volume distribution were analyzed under different opening schemes of the exhaust vent. A section-by-section calculation method was established for the applicable limit length and air leakage of the ceiling centralized smoke exhaust system. This study further established a simple calculation method for the applicable limit length of a ceiling centralized smoke exhaust system through theoretical analysis, which made the calculation simple and easy to perform and enabled the results to be calculated with a certain degree of accuracy.

Research on the Influence Mechanism of Outdoor Wind Environment on Indoor Smoke Exhaust Efficiency in the Super-High-Rise Tower Crown Based on Airpak Simulation

The high wind pressure and velocity of the outdoor environment make super-high-rise tower crown space distinct from general tall through space. This segregation causes the crown space to be particularly prone to smoke short-circuiting influenced by the outside wind environment if a fire occurs indoors, and causes deficient smoke exhaust efficiency in a fire. The goal of this study was to investigate the general principle regarding the effect of the outdoor wind environment on smoke exhaust efficiency of such spaces under the crown space. We measured external wind direction and wind pressure in the smoke exhaust in the tower crown and developed setting plans for the exhaust outlets and make-up air inlet. Airpak was used to create the external wind environment and compare simulations to see if smoke short-circuiting occurred. We analyzed the causes, summarized solutions that did not result in short-circuiting of smoke flow, and made adjustments. We provide an ideal plan for the setting direction and vent velocity of the make-up air inlet and exhaust outlet in the crown spaces of super-tall towers to improve the design of smoke exhaust systems in such spaces.

A multi-scale experiment analysis of air entrainment and heat exhaust coefficient under lateral smoke exhaust in tunnel fires

This study investigated the air entrainment caused by a lateral smoke exhaust system via full-scale and model-scale tests. A particular phenomenon, shear flow, was observed downstream of the exhaust vent. The phenomenon of shear flow was more intense when the exhaust velocity increased, which destroyed the smoke layer stratification and strengthened the air entrainment. Plug-holing and shear flow intensified air entrainment, and the functional relationship between air entrainment, Froude number, and dimensionless exhaust vent size was established. The relationship between the air entrainment and heat exhaust efficiency was studied, and it was found that the heat exhaust coefficient was positively related to the air entrainment. The functional relationship between the heat exhaust coefficient and air entrainment for different lateral exhaust vent sizes was presented. In addition, we observed that lateral smoke exhaust exhibit little effect on the centerline temperature distribution. A model that can be used to describe the centerline temperature distribution with lateral smoke exhaust systems was developed.

The mathematical model of kitchen smoke exhaust system in high-rise residential buildings considering the Influence of Stack effect

In high-rise buildings with large indoor and outdoor temperature difference, neglecting the effect of stack effect in smoke exhaust shafts may cause calculation error of the fluid network model. In this paper, the mathematical model of kitchen smoke exhaust system considering the influence of stack effect was put forward and it can be inserted different range hood sub-models. Compared with the results of six working conditions of the model without considering the stack effect, the error of the proposed model were reduced by 7.6%, 4.3%, 4.1%, 2.8%, 2.4%, and 2.1%. While the indoor and outdoor temperature difference varies from −5 °C to 49 °C, the effect of stack effect on the pressure in the flue and the flow rate for each user was studied for six operating rates s. The results show that under the combined effect of stack effect and flue resistance, the static pressure of the kitchen smoke exhaust system showed a low-high-low distribution, and the maximum static pressure in the flue moved toward the bottom with the increase of temperature difference. User flow rates exhibit a low-high-low-high distribution, with an increased flow rate in the bottom users and the largest flow rate in the top users.

Numerical Simulation on Smoke Temperature Distribution in a Large Indoor Pedestrian Street Fire

In order to study the characteristics of fire smoke spread and temperature distribution of a large indoor pedestrian street under different heat release rates and smoke exhaust modes, this paper focuses on the analysis of fire smoke spread, visibility, smoke temperature distribution and variation curves in an atrium. This paper uses a numerical simulation method to conduct research. PyroSim fire simulation software is used to calculate this project, which is based on a full-scale experimental design scheme. The numerical simulation results show that under the conditions of higher heat release rate, the smoke spread rate is greater than that under the conditions of lower heat release rate. Furthermore, the average temperature of smoke in the atrium is also greater, up to about 400 °C. The conditions of a higher heat release rate also show the characteristics of faster generation, faster spread and a larger volume of smoke. When the smoke exhaust system is turned on, the thickness of the smoke layer and the smoke temperature decrease. There then comes a situation where the stabile section of the fire ends in advance. The simulation results of vertical temperature distribution in an atrium can fit the modified McCaffrey plume model in any case. Under all cases, the smoke temperature reaches the maximum directly above the fire source. The horizontal dimensionless smoke temperature rises under the atrium roof, and decreases exponentially with the dimensionless distance from the fire source. The greater the heat release rate of fire source is, the smaller the attenuation coefficient is, with a more than 50% change. When the smoke exhaust system is turned on, the smoke flow accelerates and the smoke is cooled rapidly. Thus, the attenuation coefficient increases. Additionally, the effect of mechanical smoke exhaust is better than natural smoke exhaust, because mechanical smoke exhaust makes air flow and heat exchange more intense. The variation amplitudes of the attenuation coefficient under natural smoke exhaust and mechanical smoke exhaust are 13% and 22%, respectively.

Research on the effect of ceiling centralized smoke exhaust system with air curtains on heat confinement and plug-holing phenomenon in tunnel fires

As tunnel fires can easily cause numerous casualties, this paper proposes a combination of ceiling centralized smoke exhaust and air curtain ventilation to study the temperature distribution characteristics and smoke control effects to assist passenger evacuation and firefighting. Dimensionless Froude number was introduced for a theoretical analysis and a series of CFD simulations. The plug-holing phenomenon in the coupling effect between air curtains and ceiling centralized smoke exhaust systems was investigated by changed the parameters of the heat release rate, the smoke exhaust rate, and the jet velocity of the air curtains. The results demonstrate a mutually reinforcing effect of the combined ceiling centralized smoke exhaust system and air curtains in terms of smoke control. The optimal distance between the ceiling exhaust port and the air curtains is 30 m. The blocked holes in the coupled system are mainly located at the downstream edge of the exhaust port, which directly reduces the smoke exhaust efficiency. The smoke exhaust efficiency is more affected by the smoke exhaust rate variation than by the air curtains velocity. A model was built to predict the smoke exhaust efficiency of the coupled system when the fire source power is 20 MW. We propose a new modified critical Fr number (3.69), which can be used to predict the phenomenon of smoke plug-holing in the coupled system. These results allow the design of a fire protection system for tunnel fires with a high barrier and high smoke exhaust effect, facilitating the safe escape of people and efficient fire rescue in the event of a fire.

Using electric boilers with hierarchical load control systems to supply heat to apartments

Introduction. Using electrical energy, transformed into thermal energy, to supply heat to premises is not a good idea due to its low efficiency. It is generally believed that the use of electricity to supply heat to multi-family buildings is considered to have a higher carbon footprint than gas-fired heating. If we consider the entire life cycle of heat supply systems, as well as the production of smoke exhaust systems, air supply, gas supply, operating expenses, the comparison between the carbon footprints of the above technologies is ambiguous. The use of electric boilers as sources of heat supply to apartments is limited due to the amount of energy, thus produced, which is equal to 15 kW.
 Materials and methods. The author analyzed the operation of a wall-mounted electric boiler with a hierarchical load control system. Its mode of operation was focused on meeting the top-priority physiological and social needs of apartment residents.
 Results. The operation of electric heat generators, having triac and relay control systems, was compared for the case of a limited amount of electricity supplied. The authors determined the boundaries of comfortable use of electric heat generators for apartment heat supply.
 Conclusions. Electric boilers with a triac control system and a small load change step can demonstrate linear modulation in the entire range of changes in heat load values of independent heat supply systems. The structure of electrical energy consumption by electric boilers is hierarchical. An electric boiler control system must have an independent line equipped with priority and time relays. 15 kW is enough to ensure the comfortable use of any standard electrical appliances for premises up to 80 m2 located in the central areas of the Russian Federation.

Risk and Reliability Assessment of Smoke Control Systems in the Buildings

Abstract: During building fires, the most lethal factor affecting the occupants is the spread of smoke and toxic gases in the compartment, adjacent spaces, evacuation routes, and locations that are remote from the fire origin threatening life and damage to the property of the facility. Smoke and heat control in building fires is a major challenge for the egress of occupants as well as the fire-fighting operations. This paper provides an insight into risks due to the failure of smoke control and ventilation systems. Life and fire safety in and outside the building must also be analyzed in order to limit the spread of fire and control the spread of smoke thereby, offering adequate time and structural stability for the evacuation process as well as firefighting operations. This paper focuses on the identification of factors to establish the critical risk and reliability of the smoke control and exhaust systems in the buildings in an event of a fire

Numerical study on the smoke movement in office rooms with various exhaust vents settings

The ventilation system is essential to maintain a high level of the smoke layer to improve visibility during a building fire. The high level of the smoke layer allows the nearby exits can be easily located, and the fire sources can be identified during the building fire and rescue. Hence, the study of smoke movement in building fires with exhaust vent settings is essential to improve fire safety in the building. In this study, the smoke movement in real-scale offices is numerically investigated by utilising the Large Eddy Simulation (LES) computational model. Six scenarios with various exhaust vents settings are considered. The temperature distribution and the smoke layer height in the four office rooms and lobby area are analysed for all the cases. Results confirmed that the temperature distribution and the layer height have no significant difference by increasing exhaust vent size. However, the upper wall-mounted exhaust vents provide an effective smoke exhaust system, significantly increasing the smoke layer height in all office rooms.