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"Ventilation systems"
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Learning from Nature: Bio-Inspired Designs and Strategies for Efficient On-Earth and Off-Earth Ventilation Systems
Efficient ventilation systems are of paramount importance for maintaining optimal air quality in indoor and enclosed environments, both on Earth and in space. Such environments include buildings, space habitats, international space station crew quarters, tunnels, underground mines and other structures. However, conventional ventilation systems encounter various challenges, including uneven air distribution, energy inefficiency, noise, and limited adaptability to fluctuating environmental conditions. Concurrently, a multitude of organisms in nature have demonstrated the capacity to construct structures that can facilitate efficient air exchange and heat regulation. Illustrative examples of such structures include ant nests, termite mounds and prairie dog burrows. The present study explores, analyses and summarizes the mechanisms, structures and strategies found in nature that can inspire the design of efficient and effective ventilation systems. The purpose of this paper is to highlight the practical implications of the aforementioned designs. To this end, it reviews the progress of research into bio-inspired ventilation, focusing on the following three areas: air regulation, component optimization and environmentally adaptive strategies. A bibliometric analysis and research trend is presented to illustrate the key developments in this field over the past 25 years. The potential of integrating the bio-inspired strategies into ventilation systems, with a particular emphasis on off-Earth habitats and underground mines, is discussed. This study provides a comprehensive overview of the development of bio-inspired ventilation systems, thereby establishing the foundation for the creation of innovative and efficient design solutions.
Journal Article
Study on Methane Distribution in the Face Zone of the Fully Mechanized Roadway with Overlap Auxiliary Ventilation System
An overlap auxiliary ventilation system is very often used for driving roadways in methane-rich coal seams. An overlap zone between the outlets of the forcing duct ends with a whirl flow air-duct (WFAD) and the exhaust duct ends with a dust scrubber that is created by applying the overlap system. This study examines the distribution of methane concentrations at various distances in the overlap zone. Maintaining a long overlap zone could increase the advance of the face. Therefore, the impact of overlap zone length on the methane concentration distribution, in and beyond the overlap zone, is investigated. The evaluation of methane concentrations is performed utilizing a well-established computational fluid dynamics (CFD) approach. The mathematical model of methane emissions into the roadway is adopted. Moreover, the CFD model is validated. A vortex of the return air, caused by the free airstream flowing out of the dust scrubber, is found. This air vortex is responsible for higher methane concentrations at the end of the overlap zone. Therefore, the conclusion can be drawn that maintaining the length of the overlap zone at 5 m to 10 m should be done to control permissible methane concentrations.
Journal Article
Heat stress, thermal comfort and control strategy in a warm-humid workplace
The purpose of this study was to design a local ventilation system (LVS) to help reduce the moisture content of a Scalder hall, evaluate its comfort and thermal stress before and after implementation of LVS and introduce an appropriate index to evaluate warm and humid workplaces. The design of the LVS was performed according to the ACGIH standard (VS-30-01). Heat stress and thermal comfort assessment were performed before and after LVS using humidity index (Humidex), discomfort index (DI), heat index (HI), wet-bulb globe temperature (WBGT) and predicted mean vote index (PMV) indices and the results were compared with predicted mean vote index-predicted percentage of dissatisfied (PMV-PPD) subjective indices. The results of heat stress parameters showed that LVS was able to reduce relative humidity (RH) and wet temperature (tnw) by 47% and 7 ° C, respectively. This has caused subjects to feel the heat from hot and very RH hot to warm and the hot and percentage of dissatisfaction has dropped by more than 70%. Design and implementation of a LVS reduced the ambient tnw by decreasing RH. Results also showed in warm and humid workplaces, DI index are highly correlated with subjective evaluation of thermal comfort and this index can be used to evaluate the thermal conditions of the workplaces.
Journal Article
A Study of Absolute Pressure Inside the Cabins of Land Transport Vehicles—The Concept of a Ventilation System Regulating the Pressure in the Vehicle
This paper presents the concepts of a vehicle pressure regulation ventilation system based on the results of absolute pressure measurements in land transport vehicles: passenger cars, buses and trains. Despite the fact that absolute pressure affects human well-being and health, this parameter is often overlooked in studies assessing thermal comfort. Absolute pressure measurements were taken during normal passenger transport operation. The studies were conducted for various terrain types: lowlands, highlands, and mountains. Absolute pressure fluctuations in land transport depended primarily on altitude, with the largest atmospheric pressure differences recorded in mountains and the smallest in lowlands. A pressure change of 8 hPa within a 24 h period constitutes an unfavorable mechanical stimulus for the human body and causes changes in the excitability of the nervous system. In all measurement series, absolute pressure fluctuations exceeded 8 hPa. Based on the results of absolute pressure measurements and altitude, a simplified model for predicting absolute pressure in transport vehicles was developed. To reduce absolute pressure fluctuations inside passenger land vehicle cabins, a ventilation scheme regulating pressure inside land vehicle cabins was proposed.
Journal Article
Research on gas hazard prevention and control of a high-gas fully mechanized mining face based on ventilation system optimization
The gas accumulation in the return corner of a high-gas fully mechanized mining face can easily cause the gas volume fraction to exceed the safety limit, threatening the safety of coal mines. In this study, the unit method was used to analyze the gas sources and emissions based on the actual case. The airflow and gas distribution characteristics of the two-inlet-one-outlet (TIOO) ventilation system and the one-inlet-two-outlet (OITO) ventilation system were studied using CFD numerical simulation. The results show that under the TIOO ventilation system, the “U”-type air leakage in the goaf leads deep gas into the return corner, which causes the gas volume fraction in the return corner to rise to 0.4–2.0%. After the mining face is optimized into the OITO ventilation system, the “J”-type air leakage of the goaf suppresses the high concentration of gas in the deep position of the goaf. Combined with the gas extraction measures, the gas volume fraction in the return corner, exhaust roadway’s outlet, and retaining roadway’s outlet is controlled at 0.28%, 0.34%, and 0.23%. This study will provide new ideas for solving the problem of gas accumulation in the return corner of a high-gas fully mechanized mining face.
Journal Article
Aerodynamic performance of a ventilation system for droplet control by coughing in a hospital isolation ward
Over 766 million people have been infected by coronavirus disease 2019 (COVID-19) in the past 3 years, resulting in 7 million deaths. The virus is primarily transmitted through droplets or aerosols produced by coughing, sneezing, and talking. A full-scale isolation ward in Wuhan Pulmonary Hospital is modeled in this work, and water droplet diffusion is simulated using computational fluid dynamics (CFD). In an isolation ward, a local exhaust ventilation system is intended to avoid cross-infection. The existence of a local exhaust system increases turbulent movement, leading to a complete breakup of the droplet cluster and improved droplet dispersion inside the ward. When the outlet negative pressure is 4.5 Pa, the number of moving droplets in the ward decreases by approximately 30% compared to the original ward. The local exhaust system could minimize the number of droplets evaporated in the ward; however, the formation of aerosols cannot be avoided. Furthermore, 60.83%, 62.04%, 61.03%, 60.22%, 62.97%, and 61.52% of droplets produced through coughing reached patients in six different scenarios. However, the local exhaust ventilation system has no apparent influence on the control of surface contamination. In this study, several suggestions with regards to the optimization of ventilation in wards and scientific evidence are provided to ensure the air quality of hospital isolation wards.
Journal Article
Study on temporal and spatial evolution law for dust pollution in double roadway ventilation system of short wall continuous mining face
To explore the laws of variations in the evolution of dust pollution within a double tunnel ventilation system at a short wall continuous mining face, a numerical simulation of air flow movement was conducted in this study. Results showed that after the wind flowing in the supporting and heading tunnels reached the head, the wind sides returned at speeds of 6.5 and 10.3 m/s, respectively. Affected by the air volume and pressure differences between the two tunnels, part of the air flow entered the connecting tunnel at an average speed of 0.8 m/s and moved to the heading tunnel. Affected by the turbulence at the driving face, a high dust concentration zone with a maximum dust concentration of 1700 mg/m
3
was formed in the tunnels at a distance of 15 m from the heading. Dust blocked by the shuttle car accumulated and settled near it and formed a dust zone with an approximate average concentration of 750 mg/m
3
at a distance of 19–23 m from the heading. The dust produced by the bolt machine formed a dust mass with an average concentration of 900 mg/m
3
at a distance of 0.5–4.5 m from the head. Quantitative analyses of the changes in dust concentration with time at the position of a driver of the continuous mining machine, shuttle car, and anchor bolt machine were conducted, and functional formulae for the quadratic distribution were obtained. Suggestions for dust control were then proposed.
Journal Article
Indoor air-pollutant reduction performance of photocatalytic ventilation system in apartments
In apartments and buildings, dilution ventilation systems are traditionally used to improve the air quality and reduce dust and pollution. However, this is not feasible without various filter systems if the outdoor air is not clean. Korea’s atmosphere contains ultrafine dust and various gaseous pollutants. Therefore, the use of air cleaners or ventilation systems with dust collection and activated carbon filters to improve indoor air quality has recently increased. However, traditional dust collection and activated carbon filters exhibit limited performance in removing gaseous pollutants in homes. Photocatalysts remove gaseous pollutants; therefore, a model combining a titanium dioxide (TiO
2
) photocatalytic reactor and mechanical ventilation system, which is mostly applied in new apartments in Korea, was proposed. The performance of indoor pollutant removal was assessed through mock-up tests, and it was verified that formaldehyde (HCHO) could be reduced by at least 35.48% (with 1ACH (air change per hour) over 150 min) and toluene (C
7
H
8
) by at least 39.95% (with 1ACH over 300 min). Thus, it is anticipated that if the photocatalytic ventilation system is applied to apartments, it will provide enhanced performance in the removal of various indoor pollutants.
Journal Article
Comparison of Local Mean Age of Air between Displacement Ventilation System and Mixing Ventilation System in Office Heating Conditions during Winter
A novel displacement ventilation system (DVS) was designed using a four-way cassette fan coil unit (FCU) and air purifiers (APs) for supplying clean air. The proposed DVS in this study involved drawing indoor air through the FCU and diffusers installed in the ceiling, controlling air temperature using the FCU, and then discharging it back into the office through the APs placed on the floor. The comparative ventilation system considered was the typical mixing ventilation system (MVS) that intakes and exhausts indoor air using diffusers installed on the ceiling. The local mean age of air was used as an index to compare indoor air quality between DVS and MVS under winter heating conditions. It was found that the DVS was more effective in improving indoor air quality in winter than the MVS. Moreover, compared to the MVS, utilizing the DVS designed in this study resulted in the advantage of a much more uniform air temperature variation in the office space. Therefore, it is anticipated that modifying the structure of an indoor space with an FCU installed in the ceiling and APs on the floor to use the DVS designed in this study would greatly assist in enhancing indoor air quality.
Journal Article