Transverse Ventilation Research Articles

The Impact of Ventilation System Type on the Microclimate of Boar's Pen and Their Clinical Triad Parameters

The purpose of the study was the impact of different types of ventilation systems in boar`s pen on the microclimate and their physiological parameters. The control group of boars was kept in a house with a transverse ventilation system, and the animals of the experimental group were kept in a geothermal air supply. It was found that, regardless of the season, transverse ventilation provides a significantly higher air velocity and relative humidity: in Winter - 0.15 m s–1 and 5.4%; in Spring - 0.35 m s–1 and 5.3%; in Summer - 0.41 m s–1 and 0.7%; in Autumn - 0.28 m s–1 and 8.1%. Maintaining a stable temperature by the normative values in the boar housing was due to geothermal ventilation, regardless of the season, especially the "basement effect" was observed in the summer months, where the air temperature was cooled to 4.5°C (P < 0.001), compared to the transverse ventilation system. Compared with the boars in the experimental group, under the influence of the temperature increase in Summer, the boars in the control group increased significantly the respiratory rate to 50.9 ppm (P < 0.001) and heartbeat rate of 45.7 ppm (P < 0.001). An increase in rectal temperature in boars at elevated ambient temperature under both air ventilation systems was not found. The obtained results make it possible to introduce the use of cost-effective geothermal air supply technology in pig farms to harmonize the physiological parameters of boars to meet their biological needs, even in closed housing to improve their welfare.

Behavioural patterns of boars by breed depending on age, season, and type of ventilation

An important tool for improving the productive characteristics of pigs, including boars, is a thorough study of their behavioural patterns and reactions to compliance with housing conditions, which serves as an indicator of the protocol for assessing the welfare of this sex group in commercial pig farms. The purpose of the experiment was to identify the influence of age, season of the year, and type of ventilation on the duration of behavioural acts of boars by breeds to establish their behavioural patterns in industrial technology. The experiment involved 18 boars of the Large White, Landrace, and Duroc breeds. The boars selected for the experiments were clinically healthy and divided into two groups of 9 animals each. The control group of boars was kept in a room with a transverse ventilation system, and the animals of the experimental group were kept in geothermal air supply conditions for a year. In the process of visualising the behaviour parameters of boars of different breeds, it was found that: the duration of rest was significant (P < 0.001) affected by 49.1-67.6% – age, 10.9-23.2% – season of the year, 0.1-3.0% – type of ventilation; the duration of movement during the day was significant (P < 0.001) affected by 44.7-68.0% – age, 9.1-28.5% – season of the year, 0.5-3.2% – type of ventilation; the duration of admission feed and water were significant affected (P< 0.001) by 49.7-71.9% – age, 7.9-25.9% – season of the year, 0.1-2.4% – type of ventilation. A behavioural act that prevailed in duration and frequency (P < 0.001), especially in the summer-autumn period, was rest, which increased in time with age from 72.3% to 76.4%, regardless of the breed, season of the year, and type of ventilation. In summer and autumn, the transverse air supply system visualised abnormal apathetic behaviour during rest in animals (lying on their sides, stomach, eyes closed, without any reactions to indifferent stimuli, and the time that boars spent on stereotypical behaviour (head banging, jumping and licking the bars of the cage) increased by 3% (P< 0.95) and in the “position of sitting dog” by 2% (P< 0.95). The results obtained allow introducing the use of ethological factors in industrial pig production to increase boar sperm production, and identify individuals with behavioural deviations to develop ways to assess welfare and integrate them into production

Effect of Semi-Transverse Ventilation Velocity on Combustion Characteristics of Pool Fire Sources in a Scaled Tunnel

Compared to longitudinal ventilation, there are few studies on fire source development under semi-transverse ventilation. This work studied the influence of semi-transverse ventilation on the combustion characteristics of fire sources in a scaled tunnel. The burning rate and heat transfer feedback during pool fire combustion were revealed under different longitudinal and transverse ventilation velocities. The results showed that transverse ventilation had little influence on combustion characteristics, and the burning rate was more obviously affected by longitudinal ventilation. The heat convection feedback increased monotonically with the increase of the longitudinal ventilation, which led to the increase of the total heat feedback on the fuel. The heat radiation feedback changed little, and the heat conduction feedback decreased monotonically with the increase of the longitudinal ventilation velocity. By aid of a Fire Dynamics Simulator, it was found that the flame tilted downstream and was in the flow line of the lower cold air flow coming from upstream and the upper hot smoke flow outgoing in the downstream direction. The transverse ventilation of 2 m/s or lower hardly affected the combustion field of the fire source. Therefore, semi-transverse ventilation is preferable to longitudinal ventilation from the point of view of limiting fire expansion.

Numerical study on the maximum temperature rise and thermal-smoke front spread length in the upstream of semi-transverse ventilated Underground Traffic Link Tunnels

To fill the gap between the high realistic demand and lack of research basis, the process of smoke spread in Underground Traffic Link Tunnel fires during operation is investigated by numerical modeling. Good agreement between numerical predictions and experimental measurements for the longitudinal temperature has been achieved. Good agreement between numerical predictions and experimental measurements for the longitudinal temperature has been achieved. The characteristics of smoke transportation at key locations (e.g., maximum excess temperature and smoke fronts) were analyzed. A novel division method for the maximum lengths of smoke bays, which depends on thermal-smoke front spread length established from the characteristic number Ri = Q̇fuel∗1/3/V∗ of mixed convection, to utilize the nature of smoke as much as possible during a fire is provided based on dimensional analysis and similarity principle. The margin of error between the final model prediction in this paper and the simulation was within plus or minus 10%. The outcomes of this study are believed to have practical guidance significance for linkage and interlock control of smoke management and passive fire protection design in tunnels during operation with a transverse ventilation system.

Safety Assessment of Hydrogen Jet Fire Scenarios within Semi-Confined Spaces

Hydrogen fuel cell vehicle (HFCV) technology poses great promise as an alternative to significantly reduce the environmental impact of the transport sector’s emissions. However, hydrogen fuel cell technology is relatively new, therefore, confirmation of the reliability and safety analysis is still required, particularly for fire scenarios within confined spaces such as tunnels. This study applied the computational fluid dynamics (CFD) simulations in conjunction with probabilistic calculation methods to determine the associated thermal risk of a hydrogen jet fire in a tunnel and its dependency on scenarios with different tunnel slopes, longitudinal and transverse ventilation velocities, and fire positions. A large-scale model of 102 m in which the effects of outlined parameter variations on the severity of the fire incident were analysed. It is found that both tunnel ventilation techniques and slope were critical for the effective ejection of accumulated heat. With ventilation playing a primary role in the ejection of heat and gas and slope ensuring the stability of the ejected heat, probabilities of thermal burns were found to be reduced by up to approximately 35% with a strong suggestion of critical combinations to further reduce the dangers of hydrogen tunnel fires.

Full-scale experimental investigation on smoke spreading and thermal characteristic in a transversely ventilated urban traffic link tunnel

Transverse ventilation system is an effective method to control the smoke propagation in tunnel fires. In the current research, 14 full-scale burning tests were conducted in an urban traffic link tunnel in Chongqing, China. Temperature and velocity profiles, as well as the smoke stratification characteristics affected by the transverse ventilation were successively explored. Results underlined that 1) Fire location and air supply system have limited influence on the induced air velocity while the induced air velocity slightly decreased as heat release rate increased. When more smoke outlets were activated, the induced air velocity increased; 2) Ceiling temperature was very sensitive to the fire location, smoke extraction, and air supply system. A distinct temperature decrease was observed when (a) the fire moved closer to the outlet; (b) more outlets were activated; (c) supply vents near the fire were opened; 3) Thermal stratification could be well predicted by the temperature quotient proposed by Newman. Considering the transverse ventilation, the relationship between temperature ratio ΔTcf/ΔTavg and Froude number Fr accounting for the transverse ventilation was modified based on the present measurements.

ABSTRACT FOR ONE AND TWO -TUNNELED COMBINED VENTILATION SYSTEM FIRE-SAFETY

It is therefore important tunnel ventilation for avoiding smoke and toxic or for reduction their distribution during the fire in tunnel. During processing and planning tunnel ventilation system its very important determination of ventilation system ability as for fire start as for developing its maximum power. In the previous work there is shown semi-transverse ventilation systems and transverse ventilation systems disadvantages which appears during the fire. Exactly in such situations motion direction of air and air consumption will be caused by fire and will not be depended on ventilators. As we. Determined the dynamic pressure launched by fire is at least 30 times more than most powerful ventilators which has been issued. Mentioned basic applies to also in such ventilation systems which contains two tunnels.

Present-day vehicular traffic tunnels in designing stage and under construction

The characteristics are given for the tunnels of the principal countries where vehicular traffic tunnels are being designed, constructed and used. The analysis of the data has shown that the existing ventilation systems that operate in a stable economic regime call for the use of natural draught along with the modern hardware. Using Rikoti and Rocki vehicular traffic tunnels as an example, it has been shown that the longitudinal and transverse ventilation scheme employed in Rikoti and Rocki vehicular traffic tunnels is inconsistent with the internationally accepted schemes for the tunnels of similar length. A comparison has been made between the ventilation system of 6560 m long tunnel in Norway (Fodnes) and that of Rikoti tunnel. The analysis of tunnel cross-section configurations, geometric parameters and the schematic diagrams of ventilator arrangement has shown the advantage of the replacement of the semi-longitudinal ventilation scheme existing in Rikoti tunnel by the longitudinal scheme. Table 1 provides a list of vehicular traffic tunnels, both in-service and under construction. A separate table 1 includes the parameters of tunnels under construction in Germany and Norway. 111.2, tabl. 2, bibl.2.

Numerical Investigation of Smoke Propagation in Road Tunnels Caused by a Burned Truck

Abstract The efficiency of smoke extraction for longitudinal and transverse tunnel ventilation systems was studied in this paper by conducting numerical simulations using computational fluid dynamics (CFD). The smoke was assumed to result from a fire initiated from a truck inside the tunnel. The most dangerous issue regarding the fire inside tunnels is smoke as it leads to low visibility and choking and may lead to death. The most important result of this paper refers to that the longitudinal ventilation design does not provide efficient smoke extraction compared to the transverse ventilation design as the air jets push the smoke in the downstream direction and then the smoke spreads randomly after the flow loses its momentum gradually. There is a big drop in the visibility for the longitudinal ventilation design that appeared many times and at many locations downstream the fire location. On the other hand, the transverse ventilation design provided more efficient smoke extraction as the jet fan upstream the fire is turned off while the supply fan downstream the fire is reversed to work as an exhaust fan. As a conclusion based on the findings of this paper, it may be said that the transverse ventilation design provided more safe conditions, lower contaminants concentrations, and higher visibility values compared to the longitudinal ventilation design. This work tends to add more information to minimize the research gap related to having a detailed comparison between the two ventilation strategies for a special case where the fire size is relatively large in a long tunnel.

Numerical Simulation of the Evacuation Process and Smoke Propagation Due to a Fire in a Road Tunnel With Transverse Ventilation System

Abstract Fire accidents in road tunnels can form a great danger in the life of people if the evacuation process does not happen effectively. This paper introduces a numerical investigation of fire and evacuation analysis in a road tunnel and provides important insights into the conditions that people are exposed to during evacuation. The fire was assumed to originate from a bus with a fire size of 30 MW at the moment corresponding to the peak heat release rate. Results including smoke distribution, visibility distribution, paths of people during evacuation, people existence density, and people speed are presented and analyzed. One of the important findings of this paper is the estimation of the time available for people to evacuate safely before the approach of the smoke layer to the occupation zone causing deterioration of the visibility values. The discussion introduced a clarification of the connection between the time of exposure to smoke, people speed, and smoke propagation speed. Results showed that the time of exposure to smoke during evacuation can be significantly increased if the fire size is increased especially for persons located within 15 m from the fire location and take more than 2 min to take the decision of evacuation.

NUMERICAL INVESTIGATION ON SMOKE MANAGEMENT IN UNDERGROUND BRANCHED TUNNELS

Soot is perhaps the most harmful element in vehicle tunnels fire as smoke moves harmonize with the way passengers flee. It decreases visibility and can cause suffocation fatalities.
 This paper presents an empirical analysis on the effect of removing smoke through different ventilation systems on smoke distribution inside the vehicle tunnel, such as water mist system with transverse ventilation with several extractions of exhaust fans Sustainable human conditions were also tested. FDS 2019 ver. was used to predict temperature, visibility, and concentration of co.
 Motivation/Background: Present work to investigate the effect of extracting the smoke by different system of ventilation on smoke spread inside the vehicular tunnel. 
 Method: By FDS 2019 that used governing equations and naver-stocks equations. 
 Results: We predicted in this paper smoke spread, temperature distribution, co concentration distribution and visibility. 
 Conclusions: This study looks at the importance of smoke control generally as well as the smoke control criteria in the automotive tunnel configuration which acknowledged them. 
 Because the smoke barrier water mist screen with a transverse ventilation device improves the smoke removal technique. FDS is a valuable method for simulating smoke diffusion as well as other effects.

Optimized design of air inlet devices based on environmental analysis of a broiler house model

A typical broiler house in the cold region of northern China was selected as the research object of this study. The environment of the broiler house was studied in depth by using the Airpak software. Then, an optimized design of air inlet devices for this typical broiler house in the cold region, under the condition of transverse ventilation, was made on basis of two influence factors: the length of the flow guiding device, and the direction of airflow. The optimized air inlet devices helped to improve the airflow in the broiler house, hence changing environmental factors such as internal temperature distribution, wind speed distribution, and carbon dioxide distribution. The length of the ideal flow guiding device should be approximately 1 m and not more than 2 m. Influence by the direction of the air inlet devices was affected by length of the guided airflow. Increase in the direction of the air inlet device led to rise of the body plane temperature of the chickens and the overall wind speed, while carbon dioxide distribution remained basically unchanged. The best direction of airflow (3) should be 30°∼45°.

Hazard analysis on tunnel hydrogen jet fire based on CFD simulation of temperature field and concentration field

In order to research the fire characteristic of hydrogen jet fire in tunnels under different conditions, computational fluid dynamics (CFD) simulations of the hydrogen jet fire from a hydrogen transport vehicle inside a tunnel were carried out. Several new different factors, such as hydrogen leakage rate, leakage area, longitudinal ventilation, transverse ventilation, the volume of the tunnel and the leakage location, were considered to analyze the influence on the temperature and diffusion of hydrogen inside the tunnel during the jet fire. Results indicate that the temperature rise-rate and hydrogen diffusion rate in the tunnel increased with an increase in the hydrogen release rate. However, the excessive leak rate could inhibit further diffusion of hydrogen in the tunnel. Hydrogen diffusion rate decreased as the cross-sectional area of tunnel increased. Longitudinal ventilation can effectively reduce the overall temperature inside the tunnel but will lower the high-temperature layer in the tunnel below the safe height. In addition, compared with an open space, the hazards of the hydrogen jet fire inside a tunnel lie in not only high temperature but also the accumulation of hydrogen, which may pose a secondary disaster inside the tunnel. In order to control the hazard and avoid the secondary disaster after the hydrogen jet fire happened, adequate longitudinal and transverse ventilation is necessary inside the tunnel.

Smoke control in tunnel with a transverse ventilation system: An experimental study

We carried out a series of experiments in a small-scale tunnel to study the confinement of smoke flow between two exhaust vents located on either side of a buoyant source placed at ground level within a ventilated tunnel. The objective of our study is to quantify the influence of the shape and the position (with respect to the tunnel axis) of the dampers, including the specific case of full-width dampers, on the performance of the transverse ventilation system. To that purpose, we investigated the extent of the backflow length downstream of the dampers, the “confinement velocity” (suppressing the back-layering flow downwind of the vents) and the stability of the smoke stratification. The results show that the best performances are achieved when the width of the dampers is the same as the tunnel width: this minimises the extent of the back-layering flow (for given extraction flow rates) and ensures the stability of the smoke stratification. The worst conditions are observed with square-shaped dampers located on the side of the ceiling, this configuration disturbs the stratification of the smoke layer before the confinement conditions are reached. Subsequently, we evaluated the effect of solid barriers -placed on the tunnel ceiling downstream of same three dampers typologies-on the propagation of the smoke. The results show that these barriers improve significantly the efficiency of system with square-shaped dampers located on the side of the ceiling: they reduce the confinement velocity and enhance the stability of the smoke stratification.

Critical velocity in the transverse passages of a railway tunnel rescue station with semi-transverse ventilation

In the event of a railway tunnel fire, rescue stations are intended to provide a safe, smoke-free refuge for evacuated passengers. Rescue stations are required for railway tunnels longer than 20 km. Located near the middle of the tunnel, evacuated passengers access the rescue station through a series of transverse passages. Under such emergency conditions, railway tunnel systems operate under longitudinal, transverse, or semi-transverse mechanical ventilation modes to draw in fresh air and exhaust the smoke through the top or end of the tunnel. A minimum flow velocity is required during ventilation to prevent smoke from entering the transverse passages leading to the rescue station. This critical velocity in the transverse passages is important for ensuring the safety of evacuated passengers and differs depending on the tunnel system’s mode of ventilation. In this study, we used both experimental and numerical methods to investigate the critical velocity in the transverse passages with a semi-transverse ventilation mode at the railway tunnel rescue station. We constructed a 1:20 scale model of a railway tunnel system to support experimentation and used numerical simulations to determine the dependence of the critical velocity in the transverse passages on the fire source position and heat release rate, semi-transverse smoke exhaust velocity, height and width of the protection door, and tunnel blockage ratio. The results indicated that the critical velocity in the transverse passages is dependent upon the fire source position, semi-transverse smoke exhaust velocity, height of the protection door, and tunnel blockage ratio. These findings are inconsistent with previously reported findings for railway tunnel systems operating under a longitudinal ventilation mode.

Integrated performance analysis of ventilation schemes for double-line subway tunnel

The analysis of ventilation schemes for double-line subway tunnel uses criteria of operational economy and efficiency in routine and emergency modes. The longitudinal, transverse and longitudinal–transverse schemes ventilations are considered. It is shown that the most efficient and economic scheme is longitudinal ventilation in the routine mode and longitudinal–transverse ventilation in the emergency mode.

A uniform air flow distribution design strategy for use in tunnel transverse ventilation systems

We focused mainly on a uniform air flow distribution design strategy for a multi-perforated air supply duct with a multi-blade opposed regulation damper. This design is especially required in tunnel transverse ventilation systems, in which a uniform air flow distribution is needed to dilute vehicle exhaust gases or vehicle emissions to acceptable concentrations. First, local resistance coefficients arising when air flows out of the duct through the damper were investigated by means of dimensional analysis and computational fluid dynamics (CFD) simulation, and a mutual authentication was performed with 3D and 2D simulation results. This revealed that the ratio of the velocity in the duct and the damper, and the blade opening angle are the two main factors affecting the resistance coefficient. Second, theoretical analysis based on Bernoulli’s equation was implemented to establish the relationship between the local resistance coefficient and the pressure drop. Based on the simulation results, a uniform air flow distribution design strategy corresponding to the opening angle adjustment was obtained. Finally, a calculation case study was carried out, and sufficient consistency between the theoretical and numerical calculation results was achieved, verifying the reliability of the design strategy.

Application of transverse ventilation in grain storage in China: Presentation

Application of transverse ventilation in grain storage in China: Presentation

Understanding sidewall constraint involving ventilation effects on temperature distribution of fire-induced thermal flow under a tunnel ceiling

This study focused on temperature distribution of thermal flow under an arced ceiling, induced by a pool fire impinging on the sidewall of tunnels with natural ventilation. A sequence of full-scale simulations were carried out for fires against the sidewall with decreasing transverse distances from 7 to 0.5 m and considering five different wind velocities from 0 to 2 m/s. The differences in temperature distribution between the arced ceiling and flat ceiling are compared and analyzed. The simulated values are also compared to the previous results from full-scale tests and empirical models. The results show that the longitudinal temperatures beneath the flat ceiling are lower than those beneath the arced ceiling when x/Hef > 1, owing to a greater heat loss in the movement process. For the arced ceiling, the correlation between the normalized ceiling jet temperature rise and the dimensionless transverse distance can still fit an exponential function, but the constraint effect of the sidewall is more significant compared to that in the flat ceiling because there exists a transition from a weak plume to a strong plume as the transverse distance is reduced. In addition, a modified correlation is proposed to predict the maximum temperature rise under an arced ceiling in the range of HL < Hef, wherein different transverse fire locations and ventilation velocities are considered simultaneously.

Multi-scale Coupling Analysis of Partial Transverse Ventilation System in an Underground Road Tunnel

Abstract A real underground road tunnel is selected for analyzing the changing law of the supplementary air volume at both ends of tunnel by a multi-scale coupling method. The partial transverse ventilation system has been installed in this tunnel. For a long tunnel, one-dimensional (1D) model or three-dimensional (3D) model has its own limitation in the numerical simulation. A multi-scale model which couples 1D and 3D models has been adopted. The computed results by multi-scale couple model are compared with those by 3D model in which open boundary condition are set at two portals. The results indicated that the air supplement volume at two portals of the tunnel by multi-scale coupling method is less than the recommended value of smoke exhaust by engineering standard. In addition, the multi-scale coupling simulation has obvious advantages in evaluating the functional of partial transverse ventilation systems. A formula has been put forward for the design of smoke exhaust volume. Compared with the recommended value of the smoke production in the engineering specification, this smoke calculation formula is more operable and more convenient to estimate the capacity of the exhaust system in design.