Effects Of Ventilation Conditions Research Articles

The effects of ventilation conditions on mitigating airborne virus transmission

The effects of ventilation strategies on mitigating airborne virus transmission in a generic indoor space representative of a lobby area or information desk found in a hotel, company, or cruise ship are presented. Multiphase computational fluid dynamics simulations are employed in conjunction with evaporation modeling. Four different ventilation flow rates are examined based on the most updated post-COVID-19 pandemic standards from health organizations and recent findings from research studies. Three air changes per hour provide the best option for minimizing droplet spreading at reasonable energy efficiency. Thus, a higher ventilation rate is not the best solution to avoid spreading airborne diseases. Simultaneous coughing of all occupants revealed that contagious droplets could be trapped in regions of low airflow and on furniture, significantly prolonging their evaporation time. Multiphase flow simulations can help define ventilation standards to reduce droplet spreading and mitigate virus transmission while maintaining adequate ventilation with lower energy consumption. The present work significantly impacts how heat, air-conditioning, and ventilation systems are designed and implemented.

Effects of ventilation system design on flame behavior and smoke characteristics for mitigating marine engine room fire hazards

Engine room fires are one of the most harmful types of ship fires, the development of which is closely related to the design of marine ventilation system. In this paper, a full-scale numerical study of ship's engine room fire is carried out using a fire dynamics simulator, and the effects of vent layout and air velocity on the flame behavior, smoke stratification and diffusion are investigated. The three-dimensional model of the engine room is built based on the ocean-going training ship Yukun of Dalian Maritime University. First, the variations of flame behavior under different air vent layouts and wind speeds are explored, and a mathematical model is derived to quantify the flame deflection angle. Then, the effects of ventilation conditions on the smoke stratification in the cabin are analyzed, and the characteristics of hot smoke diffusion are revealed. The results show that a higher ventilation velocity is beneficial to the rapid cooling of the ship's engine room, and the symmetric ventilation layout of Method 3 with a central intake on the upper side and a bottom exhaust on both sides is more conducive to the safety of the engine and other heat source equipment in a fire. This study provides references to the design and optimization of ventilation systems on ships, which can improve the safety of the important equipment in the engine room and prevent further expansion of fire.

Effects of Quantity and Arrangement of a Flame-Retardant Cable on Burning Characteristics in Open and Compartment Environments

The results of cable burning experiments conducted in a well-controlled or open environment may differ from fire phenomena in an actual installation environment of cables where the effects of ventilation conditions and thermal feedback exist. In order to prevent the misunderstanding of fire phenomena due to these differences, the changes in burning characteristics in open and compartment environments were investigated for a flame-retardant (TFR-8) cable and general PVC (VCTF) cable arranged on three-layer trays. As a result, it was confirmed that the fire scale, fire spread area, and cable damage varied greatly depending on the cable arrangement under the same cable quantity condition. Furthermore, the maximum heat release rate (HRR) and fire growth rate of TFR-8 in the compartment environment increased more than 3-times compared to the open environment, and showed a similar level of fire risk to VCTF even though it is a flame-retardant cable. Additional experiments using vertical and horizontal openings of various shapes were conducted to evaluate the individual contributions of thermal feedbacks from the wall and smoke layer to the changes in burning characteristics within the compartment. The results of this study can be used as basic data to reduce fire damage while providing an essential understanding of cable fire phenomena.

An Experimental Study on Compartment Crib Fires with Open Ventilation

The paper describes an experimental study on the behavior of crib fire with open ventilation conditions. An experimental setup is designed and fabricated in the fire research laboratory, IIT Roorkee to investigate and analyze the crib fire behavior in a compartment. Experiments are carried out in a compartment of the dimension of 4 * 4 * 4 and having a door of 2 * 1(All in meters). The parameters, including the gas temperature, mass loss rate, heat flux, flame temperature, and compartment pressure, were measured during the experiments. Based on experimental results and recognized fire theories, the effect of ventilation conditions on the burning properties of wood cribs was studied.

Characteristics of indoor human-induced particle resuspension under different ventilation conditions

This study performed a series of experiments to study the characteristics of human-induced particle resuspension under different ventilation conditions. Four modes of supplied airspeed were evaluated: no wind, low wind (2.742 m/s), medium wind (3.849 m/s) and high wind (4.422 m/s). Results show that the steady-state particle concentration can be approximated as a linear function of the airspeed. Human walking and ventilation conditions can have a significant and coupling role in particle behaviours. In particular, human walking provides initial energy for resuspension by disturbing the local fields, and thus increases the resuspension, especially for large particles of 5–10 μm in size. The wind has two competitive effects, that is, supplying energy to keep particles suspended and pushing the particles downward, and the latter becomes dominant when the airspeed was too high. Consequently, intermediate airspeeds can intensify the effect of human walking, and introduce higher peaks of particle concentration in the human-walking stages. As for the particle number density, similar conclusions can be drawn that the effect of ventilation conditions is more pronounced on small particles less than 1 μm while that of human walking is on large particles. This work lays a foundation for revealing the particle resuspension mechanism.

Effects of ventilation conditions and procedures during a fire in a reduced-scale room

This paper deals with the consequences of applying ventilation procedures during confined fires. If the air intake duct is closed after the beginning of the fire, another risk may appear, namely the ignition of unburnt gases in extraction ducts. This configuration is typical of many industrial installations equipped with ventilation networks. Heptane and dodecane pool fires were performed in a reduced-scale compartment equipped with a mechanical ventilation network. Heat release rate, temperatures and unburnt species concentration were measured for different pan diameters, different ventilation flows, with and without closing the intake duct, to study fire development and the potential risk of ignition in the exhaust system. Empirical correlations to estimate unburnt species concentrations are given. Based on these correlations, lower flammability limit calculations and scaling laws, a risk assessment methodology is proposed and a decision support tool is provided. Experimental results clearly show that the auto-ignition of unburnt gases can happen near the extraction duct, with and without closing the intake duct.

Simulation study on the influence of ventilation conditions on temperature distribution in a narrow space

Taking a college building corridor as an example, the fire simulation software FDS is used to study the fire characteristics of narrow space. By creating a numerical model, the temperature field in the space is monitored, moreover the effect of ventilation conditions on the distribution of temperature in the channel is researched to provide a reference for the setting of the temperature detector in the channel.

Comparative assessment of CFD Tools and the Eurocode Methodology in describing Externally Venting Flames

The ability of currently available Computational Fluid Dynamics (CFD) tools to adequately describe Externally Venting Flames (EVF) is assessed, aiming to demonstrate compliance with performance-based fire safety regulations. The Fire Dynamics Simulator (FDS) CFD tool is used to simulate the EVF characteristics in a corridor-compartment-façade configuration exposed to natural fire conditions. Numerical results of the temporal evolution of gas velocity, gas temperatures and flame shape are obtained for both the interior and the exterior of the compartment. Predictions are compared to respective experimental data, as well as to correlations suggested by the Eurocode methodology. The effects of ventilation conditions are investigated by simulating both Forced Draught (FD) and No Forced Draught (NoFD) test cases. The obtained results suggest that currently available CFD tools are capable of achieving good qualitative agreement with experimental data and, in certain cases (e.g. FD conditions), adequate quantitative agreement, that generally outperforms the Eurocode prescriptive methodology.

Studying the Variation of Indoor Radon Levels in Different Dwellings in Hoshiarpur District of Punjab, India

The purpose of this study was to investigate the radon levels in different houses of different villages/towns of Hoshiarpur district of Punjab, India, using a time-integrated passive technique containing LR-115 Type II solid-state nuclear track detectors, to determine the health hazards. The measured annual average indoor radon concentrations and the annual effective dose in these houses varied from 84.93 to 128.53 Bq m−3 and 1.45 to 2.19 mSv y−1, respectively. The measured values of annual effective dose were less than the lower limit of the recommended action level (3–10 mSv). The winter to summer ratio was calculated for all the studied dwellings and this ratio varied from 0.83 to 3.14. In general, the indoor radon concentration was higher in winter season than in the summer season. The effect of ventilation conditions on measured radon levels inside dwellings was also discussed. The present indoor radon concentration values were on the higher side than the world average of 40 Bq m−3.

Flame radiation from polymer fires

Abstract Enclosure fires can be divided into two ventilation regimes: well-ventilated and under-ventilated combustion. The influence of fire ventilation on flame radiation is very important in enclosure fires especially for under-ventilated conditions. An approximate model for predicting flame radiation for both well- and under-ventilated fires is proposed on the basis of the Γ-correlation, in which the role of flame sootiness and heat release is considered. This paper is an extension of work performed earlier and reported in Tewarson et al. (Combustion and Flame, 95 (1993) 151-169) [1] . The results are calculated for several typical polymers, and the relationship between the flame radiant fraction and the fuel’s smoke-point has been examined. Additionally, flame radiation is predicted by the slightly modified Global Flame Radiation (GFR) Model of de Ris and Orloff. The comparisons between experimental and predicted data are satisfactory. This study attempts to provide: (1) a deeper scientific understanding of the effect of ventilation conditions on flame radiation, and (2) available correlation, for the analysis of enclosure fires.