Optimal Ventilation Research Articles

Impact of modified ventilation strategies on water evaporation rate and thermal comfort in an indoor swimming pool by numerical study

The evaporation rate from a pool surface and the thermal comfort of bathers were evaluated numerically in a swimming pool enclosure in Canada while modifying the ventilation strategies, aiming to reduce trichloramine (NCl3) concentrations in the breathing zone. Air movement is required near the pool surface to remove NCl3 emanating from the water, but this airflow may cause unwanted thermal discomfort and water evaporation increase. A reference case based on the existing conditions and four simulated cases with varied ventilation strategies were evaluated to assess the impact on the water evaporation rate and thermal comfort. We implemented a water evaporation model in the Fire Dynamics Simulator (FDS) code to study how the modified airflow patterns may impact the evaporation rate. We also determined with a PMV modified index how thermal comfort of bathers with wet and dry skin is affected by the modified airflow of each case. Our findings show that adding deck level air extraction vents allow 41% NCl3 reduction without negatively impacting thermal comfort and with only a 4% water evaporation increase. Conversely, with commonly used dilution ventilation strategy and remaining within ASHRAE's recommendations for the airflow rate, we obtain only a 3% NCl3 reduction but up to 51% of dissatisfied bathers (with a local peak of 99%) for a “cool” environment. Water evaporation rate is also increased by 16%. Numerical airflow simulation is recommended as a tool to plan an optimal ventilation strategy balancing air quality, energy expenditure and thermal comfort in indoor aquatic environments.

Numerical performance of CO2 accumulation and droplet dispersion from a cough inside a hospital lift under different ventilation strategies

The impact of mechanical ventilation on airborne diseases is not completely known. The recent pandemic of COVID-19 clearly showed that additional investigations are necessary. The use of computational tools is an advantage that needs to be included in the study of designing safe places. The current study focused on a hospital lift where two subjects were included: a healthy passenger and an infected one. The elevator was modelled with a fan placed on the middle of the ceiling and racks for supplying air at the bottom of the lateral wall. Three ventilation strategies were evaluated: a without ventilation case, an upwards-blowing exhausting fan case and a downwards-blowing fan case. Five seconds after the elevator journey began, the infected person coughed. For the risk assessment, the CO2 concentration, droplet removal performance and dispersion were examined and compared among the three cases. The results revealed some discrepancies in the selection of an optimal ventilation strategy. Depending on the evaluated parameter, downward-ventilation fan or no ventilation strategy could be the most appropriate approach.

Technologies for Heat Hazard Governance and Thermal Energy Recovery in Deep Mines

As the depth of mines continues to increase, the problems of high temperature and potential heat damage become more prominent. In this study, the characteristics of natural and industrial heat sources in mines were reviewed, and then mainstream heat hazard governance technologies and corresponding utilization methods were discussed and compared. The first category of technologies comprises the optimization of ventilation systems, the insulation of roc heat, and artificial refrigeration. These cooling approaches are limited because the heat resources cannot be recovered. The second category is the utilization of waste industrial heat in mines, including the use of waste heat from the air compressors, drainage water, and foul airflow, but the current applications of these approaches have limited effectiveness in cooling the underground space. The third category is the application of geo-structures to recover natural heat in mines. Based on the principles of the chiller/heat pump cycle and the characteristics of heat sources and sinks in mines, the potential and constraints of each technology were discussed and summarized. This study provides a scientific reference for the selection of suitable heat governance and utilization technologies.

A new tool for energy conservation in operating room: The role of machine learning models in enhancing airflow control

Maintaining high ventilation rates in operating rooms (ORs) is critical to ensure the safety of healthcare professionals and patients. Yet, the significant energy consumption associated with ventilation systems is a growing global concern. While traditional approaches have predominantly focused on optimizing ventilation design, limited attention has been given to operational control strategies. This study aims to control ceiling air supply speed by exposure aerosol concentrations exhaled by the patient. It achieves this by integrating empirical data with machine learning (ML) models, effectively balancing the need for maintaining optimal ventilation conditions and ensuring a safe aerosol exposure concentration. Experimental results from a full-scale OR setup, manipulating ceiling air supply speed, respiratory flow rate, and surgical bed height, generated 81 datasets. These datasets served as the basis for assessing the performance of 11 ML models. Notably, the extra trees (ET) and multi-layer perceptron (MLP) models outperformed the others, exhibiting impressive coefficient of determination (R2) values of 0.954 and 0.904, respectively. Moreover, the models were further enhanced by assessing their robustness with Gaussian noise and interval prediction. This study presents a novel approach that holds significant relevance for the practical control of ventilation systems, particularly with regard to health and energy efficiency considerations.

Optimal ventilation mode for double fires in a typical interchange subway station

This paper investigates the optimal ventilation mode for double fires in a typical interchange subway station. Numerical simulations were carried out in a full-scale subway station with different heat release rates, ventilation modes, and fire source locations. Results demonstrate that when double fires occur, activating ventilation systems in one line may affect the smoke spread in other lines due to the existence of transfer channels. For the platform-tunnel mixed exhaust mode, when the fire size is small, the optimal TVF exhaust volume range exists. There is no optimal smoke exhaust volume for double fires with the large fire size or near the ends of the platform. Under such circumstances, the subway staff should take some measures to hinder the unwanted smoke flow path.

Critical Care Management of Severe Asthma Exacerbations

Severe asthma exacerbations, including near-fatal asthma (NFA), have high morbidity and mortality. Mechanical ventilation of patients with severe asthma is difficult due to the complex pathophysiology resulting from severe bronchospasm and dynamic hyperinflation. Life-threatening complications of traditional ventilation strategies in asthma exacerbations include the development of systemic hypotension from hyperinflation, air trapping, and pneumothoraces. Optimizing pharmacologic techniques and ventilation strategies is crucial to treat the underlying bronchospasm. Despite optimal pharmacologic management and mechanical ventilation, the mortality rate of patients with severe asthma in intensive care units is 8%, suggesting a need for advanced non-pharmacologic therapies, including extracorporeal life support (ECLS). This review focuses on the pathophysiology of acute asthma exacerbations, ventilation management including non-invasive ventilation (NIV) and invasive mechanical ventilation (IMV), the pharmacologic management of acute asthma, and ECLS. This review also explores additional advanced non-pharmacologic techniques and monitoring tools for the safe and effective management of critically ill adult asthmatic patients.

A novel transparent cabin used in the classroom during the coronavirus pandemic: a CFD analysis

A coronavirus family is a diverse group of many viruses. Coronavirus disease 19 (COVID-19) spreads when an infected person breathes out droplets and very small particles that contain the virus. These droplets and particles can be breathed in by other people or land on their eyes, noses, or mouths. In this paper, the airflow distribution and the movement of coronavirus particles during normal breathing and sneezing in classrooms have been studied using a CFD model developed in ANSYS® 2022R2. The objective is to find ways to control the spread of the virus that enable us to practice academic activity and deal normally with the pandemic and the spread of the disease. Experiments were done with more than one turbulence model to know which was closest to the experiments as well as to determine the best number of meshes in the classroom. The effect of turbulent dispersion on particles is resolved using a discrete random walk model for the discrete phase and the RANS model for the continuous phase in a coupled Eulerian–Lagrangian method. Furthermore, that is done in two scenarios: the first is to find the best ventilation configuration by investigating the following parameters: the effect of air change per hour, the height of the air inlets and outlets, and the infected student's position. The second is to control the spread of the coronavirus in the classroom in the event of sneezing from an infected student by placing cabins and an air filter with optimal design installed at the top around each student. It was found that optimal ventilation is achieved when fresh air enters from the side walls of the classroom at a distance of 1 m from the floor and the air exits from the ceiling in the form of two rows, and the rate change of air per hour (ACH) is 4, which leads to energy savings. In addition, a novel transparent cabin is designed for the student to sit in while in the classroom, consisting of a high-efficiency particulate air filter (HEPA) that collects any contamination and recirculates it from the top of the cabin back into the classroom with different fan speeds. Through this study, this cabin with a filter was successfully able to prevent any sneeze particles inside from reaching the rest of the students in the classroom.

Optimising Mechanical Ventilation for Indoor Air Quality and Thermal Comfort in a Mediterranean School Building

The growing concern over indoor air quality (IAQ) and thermal comfort in classrooms, especially post-COVID-19, underscores the critical need for optimal ventilation systems to bolster students’ health and academic performance. This study explores the potential for improving indoor air quality and thermal comfort in the most energy- and cost-optimal manner using a demand-controlled ventilation (DCV) system coupled with a carbon dioxide control sensor. This is achieved through precooling via night purging in summer and by introducing warmer corridor air into the classroom in winter. The methodology employs both computer simulation and a real-world case study. The findings reveal that while natural ventilation in winter can achieve IAQ standard (EN 16798-1) thresholds for classrooms under favourable outdoor conditions, it results in uncontrolled and excessive energy loss. The retrofitted DCV system, however, maintained CO2 levels below the recommended thresholds for at least 76% of the year depending on classroom orientation and only exceeded 1000 ppm for a maximum of 6% of the year. This study also indicates that utilising the external corridor as a sunspace can further enhance the system’s efficiency by preheating incoming air. This comprehensive study highlights the significant potential for integrating mechanical and passive solutions in school ventilation systems. This contributes to the attainment of the United Nations Sustainable Development Goal 11 and ensures healthier and more energy-efficient learning environments that benefit both students and the environment.

Balancing therapeutic effect and safety in ventilator parameter recommendation: An offline reinforcement learning approach

Reinforcement learning (RL) is increasingly applied in recommending ventilator parameters, yet existing methods prioritize therapeutic effect over patient safety. This leads to excessive exploration by the RL agent, posing risks. To address this, we propose a novel offline RL approach that leverages existing clinical data for exploration, employing fitted Q evaluation (FQE) for policy evaluation to minimize patient risk compared to online evaluation. Our method introduces a variational auto-encoder-gumble softmax (VAE-GS) model, discerning the hidden relationship between patient physiological status and ventilator parameters to constrain the exploratory space of the agent. Additionally, a noise network aids the agent in fully exploring the reachable space to find optimal ventilator parameters. Our approach significantly enhances safety, as evidenced by experiments on the Medical Information Mart for Intensive Care III (MIMIC-III) dataset. It outperforms existing algorithms including the deterministic policy gradient algorithm (DDPG), soft actor-critic (SAC), batch-constrained deep Q-learning (BCQ), conservative Q-learning (CQL), and closed-form policy improvement operators (CFPI), showing improvements of 76.9%, 82.8%, 23.5%, 49.1% and 23.5%, respectively, while maintaining therapeutic effect.

Numerical simulation for optimising of inlet and outlet positions for mechanical ventilation and heat dissipation: A case study to improve ventilation in an indoor 110kV substation

Efficient ventilation and heat dissipation in indoor substations are crucial for the stable operation of transformers. This study investigates the impact of inlet and outlet positions on ventilation and heat dissipation performance in a 110kV indoor substation using computational fluid dynamics. A model of the 110kV main transformer chamber is developed. Twelve combinations of inlet and outlet positions are analysed. Inlet positions include side walls parallel to radiators, side walls perpendicular to radiators and both side walls perpendicular to radiators. Outlet positions include the top of the chamber, the side of the inlet, adjacent to the inlet, and opposite inlet. Results demonstrate that locating outlets at the top of the chamber reduces transformer temperature by 0.5-1.6?C and increases energy utilization by8.6%-24.8% regardless of inlet position. Two opposite inlets perpendicular to radiators allows even air distribution between radiators. And this configuration reduces transformer temperature by 3.4?C when the outlet is located at the top of the chamber. Overall, the optimal ventilation design involves top chamber outlets and inlets on opposite walls perpendicular to radiators.

Pulmonary response prediction through personalized basis functions in a virtual patient model

Background and ObjectiveRecruitment maneuvers with subsequent positive-end-expiratory-pressure (PEEP) have proven effective in recruiting lung volume and preventing alveoli collapse. However, determining a safe, effective, and patient-specific PEEP is not standardized, and this more optimal PEEP level evolves with patient condition, requiring personalised monitoring and care approaches to maintain optimal ventilation settings. MethodsThis research examines 3 physiologically relevant basis function sets (exponential, parabolic, cumulative) to enable better prediction of elastance evolution for a virtual patient or digital twin model of MV lung mechanics, including novel elements to model and predict distension elastance. Prediction accuracy and robustness are validated against recruitment maneuver data from 18 volume-controlled ventilation (VCV) patients at 7 different baseline PEEP levels (0 to 12 cmH2O) and 14 pressure-controlled ventilation (PCV) patients at 4 different baseline PEEP levels (6 to 12 cmH2O), yielding 623 and 294 prediction cases, respectively. Predictions were made up to 12 cmH2O of added PEEP ahead, covering 6 × 2 cmH2O PEEP steps. ResultsThe 3 basis function sets yield median absolute peak inspiratory pressure (PIP) prediction error of 1.63 cmH2O for VCV patients, and median peak inspiratory volume (PIV) prediction error of 0.028 L for PCV patients. The exponential basis function set yields a better trade-off of overall performance across VCV and PCV prediction than parabolic and cumulative basis function sets from other studies. Comparing predicted and clinically measured distension prediction in VCV demonstrated consistent, robust high accuracy with R2 = 0.90–0.95. ConclusionsThe results demonstrate recruitment mechanics are best captured by an exponential basis function across different mechanical ventilation modes, matching physiological expectations, and accurately capture, for the first time, distension mechanics to within 5–10 % accuracy. Enabling the risk of lung injury to be predicted before changing ventilator settings. The overall outcomes significantly extend and more fully validate this digital twin or virtual mechanical ventilation patient model.

Assessment of urban ventilation in typical Egyptian housing layouts from four eras using a multi-directional CFD analysis

ABSTRACTAir pollution is globally rising, especially in low- and middle-income countries, due to rapid urbanization. In hot arid environments like Egypt, adequate outdoor ventilation is required to aid in the removal of heat and pollutants and provide healthy living environments. In this context, the current research analyses the urban ventilation of typical Egyptian housing layouts using a simulated multi-directional approach. It is significant because few studies on evaluating urban ventilation of housing prototypes were undertaken in Egypt, and the approaches used were employed in nearly no relevant research in the region. Linear parallel, clustered, dot, and clustered-shifted patterns were investigated. Eight wind directions were analyzed to assess five parameters: 1) wind velocity, 2) age of air (aoa), 3) airflow, 4) pressure coefficient (cp) and 5) comfort index. An automated toolkit that enables the simultaneous simulation of several wind directions was employed. It consists of Eddy3D, a validated Grasshopper tool that uses OpenFOAM’s RANS models. The results showed that best velocities were found in the linear-parallel-unaligned and clustered layouts, directions NNE and N. The latter exhibited favorable airflow within its courtyards. In addition, wind directions had little influence on aoa, as did the layout pattern. Uncomfortable wind was greater in the clustered layout and lowest in the clustered-shifted layout. Except for ENE direction, cp was in opposition with ventilation, since W and WNW directions witnessed the greatest cross-ventilation potential. While linear-parallel-unaligned and clustered layouts created optimum ventilation and allowed outdoor activities, they require more research to increase cp and reduce uncomfortable winds.

In vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle through ultrasound-guided hybrid near-infrared spectroscopies

Objective. In this paper, we present a detailed in vivo characterization of the optical and hemodynamic properties of the human sternocleidomastoid muscle (SCM), obtained through ultrasound-guided near-infrared time-domain and diffuse correlation spectroscopies. Approach. A total of sixty-five subjects (forty-nine females, sixteen males) among healthy volunteers and thyroid nodule patients have been recruited for the study. Their SCM hemodynamic (oxy-, deoxy- and total hemoglobin concentrations, blood flow, blood oxygen saturation and metabolic rate of oxygen extraction) and optical properties (wavelength dependent absorption and reduced scattering coefficients) have been measured by the use of a novel hybrid device combining in a single unit time-domain near-infrared spectroscopy, diffuse correlation spectroscopy and simultaneous ultrasound imaging. Main results. We provide detailed tables of the results related to SCM baseline (i.e. muscle at rest) properties, and reveal significant differences on the measured parameters due to variables such as side of the neck, sex, age, body mass index, depth and thickness of the muscle, allowing future clinical studies to take into account such dependencies. Significance. The non-invasive monitoring of the hemodynamics and metabolism of the sternocleidomastoid muscle during respiration became a topic of increased interest partially due to the increased use of mechanical ventilation during the COVID-19 pandemic. Near-infrared diffuse optical spectroscopies were proposed as potential practical monitors of increased recruitment of SCM during respiratory distress. They can provide clinically relevant information on the degree of the patient's respiratory effort that is needed to maintain an optimal minute ventilation, with potential clinical application ranging from evaluating chronic pulmonary diseases to more acute settings, such as acute respiratory failure, or to determine the readiness to wean from invasive mechanical ventilation.

Exposure Assessment of Infectious Virus Particles in a Classroom Setting Using Computational Fluid Dynamics Model

Indoor air quality in classrooms directly affects comfort, focus, and academic performance. This research leveraged Computational Fluid Dynamics (CFD) to analyze the dispersion of infectious virus particles in classrooms. While Negative Pressure Systems (NPS) are often used at medical centers to inhibit virus particles’ dispersion, those are seldom applied in educational settings. The study aimed to pinpoint optimal ventilation and heating/AC flow rates to prevent virus particle spread. Results showed that prioritizing a higher flow rate at the ventilation unit over the heating/AC unit creates a negative pressure differential, decreasing virus dispersion by up to 93%. To establish negative pressure, the minimum flow rate ratio of ventilation to heating/AC should be 1.0. But for maximal virus particle reduction, a ratio of 2.8 is optimal. This research underscores CFD's value in understanding NPS dynamics and simulating virus behavior in classrooms. The findings suggest that NPS implementation in schools could significantly curb virus particle spread.

Assessment of indoor air quality in health clubs: insights into (ultra)fine and coarse particles and gaseous pollutants.

Exercising on regular basis provides countless health benefits. To ensure the health, well-being and performance of athletes, optimal indoor air quality, regular maintenance and ventilation in sport facilities are essential. This study assessed the levels of particulate, down to the ultrafine range (PM10, PM2.5, and particle number concentration in size range of 20-1,000 nm, i.e., - PNC20-1000 nm), gaseous pollutants (total volatile organic compounds - TVOCs, CO2, and O3) and comfort parameters (temperature - T, relative humidity - RH) in different functional spaces of health clubs (n = 8), under specific occupancy and ventilation restrictions. In all HCs human occupancy resulted in elevated particles (up to 2-3 times than those previously reported), considering mass concentrations (PM10: 1.9-988.5 μg/m3 PM2.5: 1.6-479.3 μg/m3) and number (PNC 1.23 × 103 - 9.14 × 104 #/cm3). Coarse and fine PM indicated a common origin (rs = 0.888-0.909), while PNC showed low-moderate associations with particle mass (rs = 0.264-0.629). In addition, up to twice-higher PM and PNC were detected in cardiofitness & bodybuilding (C&B) areas as these spaces were the most frequented, reinforcing the impacts of occupational activities. In all HCs, TVOCs (0.01-39.67 mg/m3) highly exceeded the existent protection thresholds (1.6-8.9 times) due to the frequent use of cleaning products and disinfectants (2-28 times higher than in previous works). On contrary to PM and PNC, TVOCs were higher (1.1-4.2 times) in studios than in C&B areas, due to the limited ventilations combined with the smaller room areas/volumes. The occupancy restrictions also led to reduced CO2 (122-6,914 mg/m3) than previously observed, with the lowest values in HCs with natural airing. Finally, the specific recommendations for RH and T in sport facilities were largely unmet thus emphasizing the need of proper ventilation procedures in these spaces.

Experimental Study on Dynamic Exhaust Law for Ventilation System of Gas Tunnel

The ventilation system is the only channel for gas exchange inside and outside the gas tunnel, which determines whether the high-risk gas in the tunnel can be exhausted in time after a gas leakage accident; thus, it is essential to study the dynamic ventilation characteristics. A fire-retarding division of the gas tunnel in Songjiang District of Shanghai is taken as the study object, and, based on the similarity theory, a similarity experiment platform is built. The simulation experiments of exhaust are carried out under different exhaust velocities, ventilation equivalent diameters and initial gas concentrations by using the control variable method. The changes in ventilation duration and gas concentration are analyzed in detail. The conclusions are as follows: (1) Time–concentration curves at all positions in the gas tunnel exhibit an “asymptote” distribution. (2) Average gas concentration has a linear relationship with time at the beginning and becomes an exponential relationship after a certain time. (3) When the exhaust velocity is 5 m/s, the initial gas concentration is 15%VOL; when the equivalent diameter of the vent in the model is 0.2 m, the ventilation duration is 100.2 s. A calculation model of ventilation duration for the standard gas tunnel is established, and the application limits of the model are 1 ≤ v ≤ 5, 0.5 ≤ d ≤ 1.5, and 5 ≤ φo ≤ 25. (4) In practical engineering, an exhaust velocity of 5 m/s and an equivalent ventilation diameter of 1 m are relatively optimal ventilation parameters.

Investigation of the effectiveness of top-down natural ventilation of a poultry building in a hot-summer mediterranean climate

In this study, computational fluid dynamics (CFD) was used to examine the efficiency of ventilation and airflow patterns in a multi-level layer hen house. The utilization of windcatchers as a natural ventilation system was the main area of focus. By comparing CFD simulations with experimental data using ANSYS Fluent, the results were validated. The findings showed good agreement in airflow velocity within the windcatchers and throughout the entire building between the CFD calculations and the experimental tests, resulting in uniform airflow distribution and the absence of turbulence in the area where the chickens were kept. This setup provided the layer hens with an acceptable level of comfort by maintaining a consistent and steady temperature profile. The windcatcher-based model demonstrated better temperature uniformity than mechanical window ventilation. The study also emphasized the importance of maintaining appropriate humidity levels throughout the building to ensure the comfort and productivity of layer hens. The advantages of the windcatcher-based system in terms of temperature distribution and airflow control were highlighted by comparison with an alternative ventilation model. These results underscore the importance of using natural ventilation systems, such as windcatchers, to create optimal ventilation conditions and provide layer hens with a comfortable and productive environment (resulting in a temperature reduction from 29°C to 19.85°C with a low and uniform air velocity ranging from 0 m/s to 0.7 m/s at cage level). Practical application An effective and eco-friendly approach to enhance animal health and productivity in poultry farms is to install a natural ventilation system with wind collectors. This setup creates optimal conditions for the animals by improving air quality, regulating temperature, and fine-tuning ventilation. Additionally, it promotes overall sustainability in poultry facilities by lowering energy costs and advocating for environmentally friendly management, aligning agricultural practices with stringent environmental standards.

Optimal Ventilation Design for Flammable Gas Leaking from Gas Box Used in Semiconductor Manufacturing: Case Study on Korean Semiconductor Industry

Highly flammable substances such as hydrogen and silane are used in the semiconductor manufacturing process. When gas leaks, it is mixed with outside air and connected to a treatment facility through the duct inside the gas box. This study investigated optimal exhaust design to prevent fire explosions and health problems by optimizing the exhaust volume when hydrogen leaks from the gas box of semiconductor manufacturing equipment. After selecting the leakage rate amount based on the KS C IEC 60079-10-1, SEMI S6-0707E, and SEMI F-15 standards, a gas box was manufactured. Subsequently, the fan speed required to ventilate the gas box more than five times per minute according to the SEMI standard and the opening area and location that can reduce the lower explosive limit (LEL) to less than 25% in the event of hydrogen leakage were determined. When the air intakes were placed on the left and right, the flow rate was measured at 32 L per minute (LPM), and the maximum concentration was measured at 9111 ppm. This is less than 25% of the LEL of hydrogen and is believed to be capable of preventing fire and explosion, even if a similarly flammable gas leaks inside the gas box.

Identifying bioclimatic techniques for sustainable low-rise high-density residential units: Comparative analysis on the ventilation performance of vernacular dwellings in China

Vernacular dwellings equipped with bioclimatic techniques, used to form low-rise high-density communities in most Asian regions, are of great value for the development of modern sustainable residential units. Natural ventilation is a major concern mainly because of its climate-related characteristics of improving indoor thermal comfort at extremely low ecological costs. Therefore, this study applies a comparative analysis coupled with field investigations and numerical simulations to the ventilation technologies of vernacular dwellings in different areas of China. Geometric prototypes of typical vernacular dwellings in six climate zones were generated based on field measurements. Computational Fluid Dynamic (CFD) simulations were conducted in OpenFOAM with the Reynolds Averaged Navier-Stokes (RANS) modeling approach and the RNG k-ε turbulence model. A correlation analysis of the building elements and climate factors was also performed to determine the relevant parameters affecting ventilation performance. The results revealed different emphases and verified strategies for wind environment regulation based on different local climates. Six physical parameters, namely wind projection angle, orientation, wind inclination angle, window-to-wall ratio, top-to-bottom ratio, and height-to-width ratio of the atrium, are considered to be closely related to ventilation efficiency. The findings from the current research provide quantitative evidence of the effectiveness of natural ventilation technologies of vernacular dwellings and contribute to comprehensive knowledge for designing sustainable low-rise high-density residential units with optimum ventilation functions.

G‘UJUMSOY KONI HAVO UZATISH STVOLIDA HAVO OQIMINI BOSHQARISH SAMARADORLIGINI OSHIRISHDA HAVO PARDASINI QOʻLLASH

On the extraction of gold-bearing ores in mines, the amount of air in the ventilation network of mines increases in proportion to increases in the length of excavations and deepening of the mines. The article deals with issues of managing the air flows into mines, the use of air curtains to reduce external and internal losses to the mine, and aerodynamic resistance. The work describes the use of the main fan and an optimal ventilation scheme in order to increase the efficiency of ventilation in mines with complex ventilation systems, with the view to reducing outdoor air losses in the ventilation duct and ventilation network by determining the optimal values for air flow, air flow rates, and pressure changes with ventilation parameters to ensure ways of effective control and distribution of the air flow.