Effects Of Ventilation Research Articles

The application of a high-density street-level air temperature observation network (HiSAN): Spatial and temporal variations of thermal and wind condition in different climatic condition types

Different patterns of urban development will result in different characteristics of the urban heat island effect (UHI). In order to explore the impacts of urban environment characteristics, wind conditions, and climatic condition types on UHI over different periods, this study adopted Tainan City as the study site, and utilized the surface roughness length and wind prediction, to evaluate the correlation between wind conditions and UHI, as well as the thermal environment affected by different environmental. The UHI characteristics were evaluated by using 100 measurement stations (HiSAN) located in different urban environments. The results revealed the expansion of the daily temperature range was associated with an increase in the eastwest UHI centroid point movement; wind conditions affected north-south shifts of UHI centroid point. The built environments was positively correlate with daytime (0.24) and nighttime (0.68) temperatures. Daytime water bodies notably cool surroundings (correlation -0.52), and green spaces enhance nighttime cooling (correlation -0.64). Wind speed negatively correlates with UHI deviation values during the daytime (-0.17) and nighttime (-0.58). The study highlights the impact of wind speeds and temperature ranges on UHI movement, emphasizing effective ventilation's role in urban cooling and quantifying the importance of water and green space in mitigating UHI.

Emission of volatile organic compounds during open fire cooking with wood biomass: Traditional three-stone open fire vs. gasifier cooking stove in rural Kenya

Cooking with wood biomass fuels releases hazardous air pollutants, including volatile organic compounds (VOCs), that often disproportionally affect women and children. This study, conducted in Kwale and Siaya counties in Kenya, employed thermal desorption gas chromatography – mass spectrometry to analyse VOC emissions from cooking with a wood biomass three-stone open fire vs. top-lit updraft gasifier stove. In kitchens with adequate ventilation, total VOC levels increased from 35–252 μg∙m−3 before cooking to 2235–5371 μg∙m−3 during open fire cooking, whereas use of a gasifier stove resulted in reduced emissions from cooking by 48–77 % (506–2778 μg∙m−3). However, in kitchens with poor ventilation, there was only a moderate difference in total VOC levels between the two methods of cooking (9034–9378 μg∙m−3 vs. 6727–8201 μg∙m−3 for the three-stone open fire vs. gasifier stove, respectively). Using a non-target screening approach revealed significantly increased levels of VOCs, particularly benzenoids, oxygenated and heterocyclic compounds, when cooking with the traditional open fire, especially in closed kitchens, highlighting the effects of poor ventilation. Key hazardous VOCs included benzene, naphthalene, phenols and furans, suggesting potential health risks from cooking. In kitchens with good ventilation, use of the gasifier stove markedly reduced emissions of these priority toxic VOCs compared to cooking with an open fire. Thus, substituting open fires with gasifier stoves could help to improve household air quality and alleviate health risks. The study revealed that VOCs were present prior to cooking, possibly originating from previously cooked food (buildup) or the outside environment. VOC emissions were also exacerbated by reduced air flow in high humidity during rainfall, suggesting an area for further research. The findings underscore the importance of adopting cleaner cooking technologies and enhancing kitchen ventilation to mitigate the impacts of VOCs in developing countries.

What are standard monitoring devices for anesthesia in future?

Monitoring the patient's physiological functions is critical in clinical anesthesia. The latest version of the Japanese Society of Anesthesiologists' Guidelines for Safe Anesthesia Monitoring, revised in 2019, covers various factors, including electroencephalogram monitoring, oxygenation, ventilation, circulation, and muscle relaxation. However, with recent advances in monitoring technologies, the information provided has become more detailed, requiring practitioners to update their knowledge. At a symposium organized by the Journal of Anesthesia in 2023, experts across five fields discussed their respective topics: anesthesiologists need to interpret not only the values displayed on processed electroencephalogram monitors but also raw electroencephalogram data in the foreseeable future. In addition to the traditional concern of preventing hypoxemia, monitoring for potential hyperoxemia and the effects of mechanical ventilation itself will become increasingly important. The importance of using AI analytics to predict hypotension, assess nociception, and evaluate microcirculation may increase. With the recent increase in the availability of neuromuscular monitoring devices in Japan, it is important for anesthesiologists to become thoroughly familiar with the features of each device to ensure its effective use. There is a growing desire to develop and introduce a well-organized, integrated "single screen" monitor.

Climatic Variations and Indoor Environmental Quality Performance of Houses in Selected Cities in Oyo State, Nigeria

Understanding how climatic variations influence Indoor Environmental Quality (IEQ) becomes crucial for designing sustainable and comfortable living spaces in this specific region. This study therefore investigates the effect of climatic variations on IEQ performance of houses in selected cities within Oyo State, Nigeria. The types of data collected for the study were numeric and ordinal. The numeric data of air temperature, relative humidity, air velocity and noise level, were gotten through objective measurements and IEQ through IEQ Calculator. The ordinal data were gotten through observation and questionnaire. Control Potential Zone technique on psychometric chat was used to analyze climate of Ibadan, Ogbomoso and Kisi. The physical measurements were conducted in the living, bedroom and kitchen spaces of the sampled houses in the low, medium and high residential density zones of the selected cities. A sample size of 581 houses from 3,490 were selected across each of the three residential density zones in the selected cities. The indoor temperature and relative humidity in the three cities were higher during the afternoon period with average thermal stress index of 39.40C, 36.90C and 38.40C respectively for Ibadan, Ogbomoso and Kisi respectively. None of the spaces satisfied the effective indoor ventilation comfort criteria of between 0.5m/s -1.5 m/s. All the spaces except the bedroom space in the compound impluvium house type satisfied the illumination range of between 50 – 60 lux. The maximum indoor noise level during the morning, afternoon and evening periods in study area were 58db, 59db and 58db respectively. Result from the IEQ calculator indicated that majority of the houses (83.6%) were star 2 in the IEQ performance. The implication was that these houses were below average in terms of IEQ performance.

Numerical simulation and optimisation design for ventilation and heat dissipation in high-temperature and high-load indoor substations

Under high-temperature and high-load operational conditions, inadequate ventilation and suboptimal cooling arrangements within indoor substations result in high oil temperatures, posing a threat to the secure and steady operation of transformers. In this paper, the ventilation and heat dissipation effect of a 110 kV indoor substation is studied by the computational fluid dynamics method. Initially, the three-dimensional simulation model of the main transformer chamber is constructed to mirror the actual substation structure. Subsequently, the impact of the upper outlet on ventilation and heat dissipation is explored. The results show that the proximity of the upper outlet to the fan on the side wall prompts the fan to draw air from the upper outlet, diminishing the air volume entering the lower intake outlet by 38.8 %. It proves detrimental to the transformer's heat dissipation efficiency. Lastly, with the upper outlet closed, the study delves into the impact of various configurations of intake and exhaust ports on optimizing ventilation and heat dissipation. A total of six cases of two scenarios for the air inlet location and three exhaust vent positions are explored. According to the simulation results, the optimal case of substation ventilation and heat dissipation is obtained by considering four evaluation parameters.

Analyzing temperature distribution in cable cabins within utility tunnels: Developing effective ventilation strategies for local thermal environment enhancement

Convection heat transfer between the cables and the air in the cable cabin of the utility tunnel can lead to high temperatures in the cable cabin. High-temperature environments may cause the performance of cable systems to degrade, threatening the stability of the city's power supply. Increasing ACH (air changes per hour) alone could not effectively improve the high temperature at the end of the cable cabin. This paper employed numerical simulations and rigorous experimental validation to study the summer temperature field of cable cabins in Xi'an. An innovative disturbance ventilation method was proposed to alleviate the high-temperature phenomenon. The results indicated that as the wind flow length increases, the temperatures rise rapidly with the distance increased, resulting in a stable high-temperature area at the end of the cable cabin and the high-temperature air accumulated at the top by thermal buoyancy. When the ACH (air changes per hour) increased from 2 to 6, the temperature field range decreased by 3.25–6.39 %, and the variance decreased by 6.03–14.42 %. After installing a disturbance fan at the beginning of the stable zone, the temperature field in the cable cabin was fully mixed. Compared to directly increasing the ACH, the temperature field range decreased by 20.65–44.76 %, and the variance decreased by 40.28–64.47 %. The introduction of a disturbance fan could thoroughly mix the air and effectively improve the local thermal environment in the cable cabin. This study contributed to the optimization of cable cabin ventilation strategies.

An integrated experimental and CFD analysis of ceiling-fan-integrated air conditioning system: Indoor air quality and air velocity

The Ceiling-Fan-Integrated-Air Conditioning (CFIAC) represents an innovative HVAC design, which involves directing supply air towards the vicinity of ceiling fans, facilitating the mixture and distribution of air within a room. By eliminating the need for terminal ductwork and diffusers, CFIAC offers an efficient cooling solution for occupants. This study employs experimental and CFD methodologies to assess various parameters, including airflow, air pollution, and temperature related to this system. Experimental tests were conducted in a controlled chamber, with the lowest inlet air velocity and the temperature, where supply air was projected from a high-sidewall vent directly towards a ceiling fan's centerline. Different operational conditions of the ceiling fan were examined (off, Level 2 and Level 4 downwards, and Upwards). Carbon dioxide (CO2), employed as a tracer gas, was released near a thermal manikin at three distinct locations within the chamber: the middle, lower left, and upper right, and the corresponding CO2 concentration distributions were evaluated. Additionally, air velocity measurements were collected and analyzed. The effectiveness of ventilation and potential health exposure was quantified using the age of air and intake fraction (IF) metrics. The findings indicate that operating the fan at Level 4 with downward airflow enhances air velocities and heat loss while reducing CO2 concentrations and age of air by an average of 14 % and 4 min, respectively. Moreover, the IF values for Level 4 operations, both downward and upward, were marginally lower compared to those recorded for Level 2 downward and fan-off scenarios, suggesting a decreased risk of cross-infection.

A complete review on enhancing air circulation and filtration for improving internal air quality in a healthy school environment

The health of staff and students is impacted by Indoor Air Quality (IAQ) in educational environments. A healthy atmosphere depends on good IAQ, yet millions of students worldwide might develop respiratory illnesses due to poor air quality. Immediate action is required to alleviate the burden of IAQ consequences in the pandemic-dominated period. This detailed evaluation focuses on techniques for improving air circulation and filtration systems to meet the critical demand for improved IAQ in schools. This research demonstrates the negative impacts of inadequate IAQ on students and educators’ cognitive capacities, health and performance based on an extensive examination of current records. A healthy learning environment, on the other hand, can minimize absenteeism, raise test results and increase pupil/teacher education/teaching productivity. This review explores the effectiveness of different ventilation as well as filtration methods, such as air purifiers, mechanical ventilation, natural ventilation and advanced filtration systems, in lowering airborne pollutants like particulate matter, volatile organic compounds (VOCs) and microbiological contaminants. This study reviews current information, emphasizes recent findings along with options and provides guidelines for the future of education. It underlines the limits of previous studies, gives ideas for further research and indicates a path forward for more enhancements to the air quality in schools. Comprehensive analysis with greater sample numbers is required to evaluate student performance, indoor contentment and environmental health exposure. On-site measurements are essential for comprehending the properties of contaminants. Intricate mitigation strategies must take health impacts, IAQ and energy efficiency into effect.

Efficacy analysis of non-invasive positive pressure ventilation in elderly patients with heart failure complicated with obstructive sleep apnea syndrome.

It is recommended to use non-invasive positive pressure ventilation in elderly patients with heart failure combined with obstructive sleep apnea syndrome (OSAS). To study the therapeutic effect of non-invasive positive pressure ventilation on elderly patients with heart failure complicated with OSAS. Using the random number table method, 119 elderly patients with heart failure complicated with OSAS who were admitted to our hospital from April 2020 to April 2021 were divided into the observation (60 cases) and control (59 cases) groups. On the basis of conventional drug treatment, patients in the observation group were treated with non-invasive positive pressure ventilation, and patients in the control group were treated with low-flow oxygen inhalation. The sleep quality, hemoglobin, red blood cells, erythropoietin, pro-brain natriureticpeptide (pro-BNP) levels and blood pressure were compared. After treatment, levels of hemoglobin, erythrocytes, erythropoietin, pro-BNP, blood pressure and sleep apnea-hypopnea index in the observation group were lower before treatment and in the control group in the same period. The oxygen saturation was higher before treatment and the control group in the same period (P< 0.05). The overall satisfaction with sleep quality in the observation group was higher (P< 0.05). Non-invasive positive pressure ventilation can improve blood oxygen saturation and sleep quality in elderly patients with heart failure complicated with OSAS, and reduce pro-BNP level.

Effectiveness of natural ventilation through single-sided window opening in air-conditioning rooms

Since many buildings are not equipped with fresh air systems, many people open windows to allow for natural ventilation while the air conditioner is running. However, prolonged window opening may cause unnecessary energy consumption. Additionally, the diverse ways of window opening lead to significant variations in indoor airflow distribution, consequently impacting ventilation efficiency. Therefore, this study used field experiments and computational fluid dynamics (CFD) to determine the air exchange efficiency and air change rate of single-sided natural ventilation in air-conditioning rooms by fitting the decay curves of tracer gas. CFD simulation was performed using the unsteady Reynolds-averaged Navier-Stokes (RANS) model to examine how window openings affect the room’s air distribution, and the computed indoor CO2 concentration was compared to the corresponding field experiment data. The results show that natural ventilation through the window opening induced constant heat and mass exchange between indoor and outdoor air, which caused extra cooling losses but was globally effective in eliminating indoor contaminants. The air exchange efficiency is influenced to varying degrees by factors such as the air supply register’s position, window opening percentage, and window opening position. The air supply register’s position exerted the most significant impact at 46.45%. Efficient indoor-outdoor air exchange can be achieved by opening windows intermittently. When the window is opened from one side and the opening percentage is 100%, the indoor environment can be improved by opening the window for about 10 min every 39 min for X-direction air supply and about 7 min every 39 min for Y-direction.

PEEP trial and effect on hemodynamic in cardiogenic shock

Abstract Funding Acknowledgements None. Introduction Congestion is a paramount pathophysiological driver in patients with cardiogenic shock. Almost half of patients admitted due to cardiogenic shock undertake mechanical ventilation although ventilatory parameter, and their potential hemodynamic effect on the hemodynamic and congestion profile are often neglected. Purpose We sought to evaluate the hemodynamic effect of positive end-expiratory pressure (PEEP) titration on patients admitted to intensive care unit for CS. Methods We perform PEEP titration trial on patients undertaking mechanical ventilation for respiratory failure related to CS. The trial consisted in 3 steps of PEEP increase from 5 to 15 cmH2O. For each step arterial saturation, right atrial -RAP- and systemic blood pressure along with heart rate and respiratory mechanics (tidal volume-TV-, dynamic lung compliance- CLdyn, driving- Δ- and plateau pressure- Ppl) were measured. All the measures were taken at end-expiration; RAP trace was analyzed and systolic, mean and diastolic component collected. The final PEEP was decided based on the best matching between saturation, CLdyn and TV. Descriptive and repeated measures with Bonferroni correction were applied as statistical analysis (IBM SPSS 29). Results Twelve patients were included (10 male, 66 ± 7 years old; 8 acute myocardial infarction and 4 acute heart failure). At baseline the mean RAP was 8.44 (± 2.32) ; SBP 106 (IQR 92-112), HR 94 (IQR 88 - 102) Δ and Ppl pressures respectively 7.42 (± 0.79) and 12.08 (± 0.79, ),VT 427(± 65.42) and CLdyn 58.3 (± 7.1). The right atrial pressure (RAP) differed between AMI and AHDF (8.25 ± 2.25 vs 20.25 ± 1.5; p &amp;lt; 0.001), so HR did (113 ± 3.4 versus 96 ± 3.2 betas per minutes; p 0.015). RAP varied consistently during the PEEP trial (either sRAP, dRAP and mRAP- Table and Figure 1). The TV changed signficnatly between the 1st and 3rd step (p 0.004) and the CLdyn varied consistently throughout the 3 steps of the PEEP trial (p &amp;lt;0.001). A significant difference were observed according to aetiology in RAP (AMI Vs ADHF, eman difference 2.4 versus 4.3 mmHg) and in CLdyn (AMI Vs ADHF mean difference 12.31 vs 8 .65, p &amp;lt; 0.01) but not in the other parameters evaluated (p &amp;gt; 0.05). Conclusion This is the first, small, study evaluating the effect of positive pressure ventilation in CS patients according to etiologies. As previously demonstrated PEEP influences the right side hemodynamic by increasing the RAP, although resulting in better CLdyn. The extent of the effect of PEEP increased may be dependent on the underlying aetiology of CS. Considering that the sample size is extremely limited, these results advocate a wider validation. However, the positive pressures induced by the ventilation in patient with CS should be taken in consideration when the comprehensive evaluation of hemodynamic to define congestion profile and phenotype are performed.Table 1.Hemodynamic parametersGraph PEEP vs RAP

The analysis of the factors influencing the operation of the piston wind in the cage of the hybrid hoisting shaft and the simulation study of the operation effect

The mixed shaft in the mine is used as the main inlet and return air shaft and also as the lifting shaft. The piston wind effect caused by the frequent operation of large and efficient lifting equipment in the shaft will disturb the normal air flow in the shaft and cause the air flow disorder. So It is important to study influencing factors and the series of piston effects of inner cage operation in the hoisting shaft. This paper firstly derives a theoretical model of piston wind for double cage operation in a wellbore based on the non-constant flow theory of Bernoulli’s equation, and derives the influencing factors of piston wind. Then, according to the actual situation of the mine, a 3D fluid simulation model of cage hoisting is established. Based on the verified simulation method, the transient division of labor of piston wind effect and its influencing factors is simulated and the influence of various factors on the development law of piston wind is analyzed in detail. The study results show that the main factors influencing the piston wind are the cage operating conditions, the cage operating speed, the shaft blockage ratio and the initial ventilation speed in the shaft. The operation of the cage produces an eddy current zone, which causes air flow disorder in the wellbore and affects the ventilation effect of the shaft. The piston wind speed is the highest when the cage running against the wind, while the speed is lower running with the wind. The most complex wind flow disturbance occurs when the two cages meet, which is almost block the flow of wind in the shaft. The change of cage operating speed and wellbore blockage ratio is related to the piston wind speed and pressure changes linearly in different conditions. There is the best blockage ratio between the hoisting cage and the shaft, which can cause the highest average ventilation speed in the shaft, and the best blockage ratio of the study model is 0.32.

Pseudo-equivalent model for sandwich panels with egg-shaped honeycomb-grid core

The novel sandwich panel with egg-shaped honeycomb-grid core (SP-EHC), formed by chamfering the grid walls, can achieve a balance between lightweight and high-strength, as well as promote effective ventilation and drainage due to the semi-closed honeycomb design. To determine the panel’s equivalent stiffness properties, an asymptotic analysis of the energy functional stored within the periodic unit cell is conducted. On this base, a 2D pseudo-equivalent model (2D-PEM) in the form of the Reissner–Mindlin model was formulated. The pseudo-excitation method was employed to analyze the self-power spectral density function and root mean square response of the 2D-PEM under random vibration. The accuracy and effectiveness of the model were validated through comparisons of the three-point bending experimental results of the 3D-printed specimen, exhibiting relative errors of 2.95%. In addition, free and random vibration analyses were conducted on the hybrid SP-EHC to further validate the model. Furthermore, the influence of material and structural parameters on specific stiffness, natural frequencies and first velocity RMS was systematically investigated. The findings reveal that enhancing the grid wall’s chamfering ratio is beneficial in achieving the desired objectives of lightweight and high-strength. In addition, compared to sandwich panels with orthogonal and pyramid grid cores, this improvement positively impacts the vibration characteristics of the sandwich panel. These findings offer valuable insights for the future design and optimization of such sandwich panels.

Evaluation of ventilation and indoor air quality inside bedrooms of an elderly care centre

Ventilation and indoor air quality are important factors that affect the health of the elderly. The purpose of this study was to find effective ventilation design measures for improving ventilation and air quality in typical two-bed bedrooms in elderly care centres (ECCs). Mixing ventilation (MV), displacement ventilation (DV), zone ventilation (ZV) and stratum ventilation (SV) were analysed with twelve scenarios to find the most effective ventilation design solutions including six scenarios with curtains between the beds and six scenarios without curtains between the beds. Airflow distribution, CO2 concentration, ventilation efficiency and health risk assessment were adopted for discussion. SV was found to be an effective method for improving air quality in the ECC bedroom while also taking into account the needs and rights of elderly residents, such as privacy. Comparing scenarios with and without curtains between beds under same types of ventilation, scenarios without curtains showed a slight (≤8%) decrease in CO2 concentration in the pillow area. However, this could increase virus transmission risk and compromise elderly privacy, so it is not recommended. Regarding the scenarios with curtains between the beds, the contaminant removal efficiency (CRE) of scenarios using SV was increased by 2.58, 3.22 and 2.12 times compared to the scenarios using MV, DV, and ZV respectively. Additionally, the health ratio (HR) of SV was reduced by 46.3 %, 53.7 %, and 41.7 %. Hence, it is recommended to install curtains between the beds and apply SV in ECC bedrooms. This study can be used as a guide for systematically designing ventilation systems in ECC bedrooms. Furthermore, collaboration among environmental engineers, designers, policymakers, and the wider community is essential to develop sustainable indoor environments for the elderly.

Study on the aerodynamic characteristics and ventilation effects of ultra-high-speed elevator car-counterweight system under the influence of multiple parameters

When the ultra-high-speed elevator car-counterweight system runs opposite each other, significant piston effects are caused, seriously affecting the elevator operation's stability. In order to explore the aerodynamic characteristics of the whole operation process of a car-counterweight system under multi-parameters, this study first establishes a three-dimensional transient model of the car-counterweight system and a multi-region dynamic layering numerical simulation method based on this model is proposed. Then, the actual elevator experiment validates the correctness of the model and the method. Finally, the influence rules of key parameters on the car's aerodynamic characteristics and ventilation effect are analyzed, and the car's aerodynamic characteristics at intersection time are analyzed emphatically. The results show that with the increase in the blocking ratio, the pressure drag and viscous drag have similar change trends at each stage, but the influence of pressure drag is more significant. The air displacement ratio increases by 34.1%, 75.8%, and 117.3%, respectively. With the increase in the hoistway height, the air displacement ratio decreases by 0.9%, 2.4%, and 2.9%, respectively. The spacing significantly affects the car's aerodynamic characteristics at the intersection time. The drag peak increases by 6.8%, 13.6%, and 20.5% and the lift peak by 21.2%, 47.8%, and 82.5%, respectively.

Wind Flow Characteristics on a Vertical Farm with Potential Use of Energy Harvesting

The response to the climate emergency requires solutions that address multiple sustainability targets, which could be conducted by merging scientific research from areas that have traditionally evolved separately. This investigation presents advances in that direction by studying a building prototype designated for vertical farming, which enables the wind energy potential across built-up areas to be explored, in this case through the implementation of micro-wind turbines on the surface of the prototype. The study includes a parametric analysis consisting of varying locations of wind turbines across the building envelope, and the width of ventilation corridors. The effects of different widths of outdoor ventilation corridors, various locations, and additional wind angles on the capacity to harvest wind resources were investigated. The results showed that the 5 m wide outdoor corridor has the best ventilation effect, and the wind turbine placed on the roof has the best wind energy potential. The efficiency of wind turbines decreases significantly when multiple devices are placed at the same height on the façades, although overall, the potential for energy harvesting seems incremental.

An Experimental Study on the Efficacy of Local Exhaust Systems for the Mitigation of Exhaled Contaminants in a Meeting Room

In industrial applications, local exhaust systems have been used extensively for capturing and confining contaminants at their source. The present study investigates the efficacy of these systems in mitigating the spread of exhaled pollutants by combining them with mixing and displacement ventilation. Experiments were conducted in a simulated meeting room with six closely situated workstations, featuring five exposed persons (simulated with heated dummies) and one infected person (simulated with a breathing manikin). Six overhead local exhaust units, merged with panels, corresponding to workstations, were installed using a lowered false ceiling. Additionally, a table plenum setting for air inlets was introduced to enhance displacement ventilation effectiveness along with local exhaust systems. Results from 16 experimental cases are presented, using the local air quality index and ventilation effectiveness in the breathing zone. The local exhaust system improved the local air quality at the measuring locations closest to the infector in almost all test scenarios. The improvement, particularly significant with displacement ventilation, marked a maximum 35% increase in the local air quality index adjacent to the infector and 25% in the entire breathing zone of the tested meeting room. Moreover, the table plenum settings, coupled with displacement ventilation, further enhanced conditions in the breathing zone. Under the specific conditions of this investigation, the number of operational local exhausts had a marginal impact on mixing ventilation but a significant one on displacement ventilation tests. The efficacy of local exhaust systems was also influenced by the levels of heat gains present in the room. Overall, the study aims to contribute to ongoing efforts to identify sustainable solutions to mitigate indoor airborne diseases with a combination of supply and local exhaust units.

Comparative Evaluation of Effectiveness of Two-handed E-C Clamp Technique versus V-E Technique in Patients with Predicted Difficult Mask Ventilation

Abstract Background: The skill of bag mask ventilation (BMV) remains pivotal during airway management for maintenance of oxygenation in apneic unconscious patients. Two-handed BMV techniques viz., the traditional E-C and V-E have been proven to be superior to one-handed techniques in optimizing BMV in difficult mask ventilation (DMV) scenarios. Aims and Objectives: This study aimed to compare the effectiveness of these two techniques of BMV in adult patients with predicted DMV. Methods: Four hundred ASA I-III adult patients with predictors of DMV received BMV after induction of anaesthesia using E-C clamp and V-E techniques in a randomized cross-over manner. Ventilator was set to VCV mode delivering tidal volume of 7 ml/kg, respiratory rate of 10 breaths per minute, and no PEEP. The primary outcome was exhaled tidal volume (Vte) and secondary outcomes analysed included air-leak, peak inspiratory pressure (PIP), end-tidal carbon dioxide (EtCO2), minute ventilation (MV), plateau pressure and SpO2. Results: Two-handed V-E technique generated significantly higher mean Vte of 377.83 ± 58.43 ml as compared to two-handed E-C technique (303.26 ± 103.34 ml). The air-leak was found to be significantly more with E-C technique (131.05 ml ± 100.95 ml) as compared to V-E technique (59.08 ± 49.62 ml). Higher EtCO2, MV with concomitant lower airway pressures were observed with V-E technique. Failure rate of BMV was significantly higher with E-C technique (19%) as compared to V-E technique (1%) (P = 0.001). Conclusion: Two-handed V-E technique results in more effective ventilation as compared to two-handed E-C technique in patients with predictors of difficult BMV. This technique may be preferred as a first option in patients with anticipated DMV.

The structure of cross-ventilation flow in an isolated cylindrical building: Numerical study

Cross-ventilation serves as an efficient means to expel pollutants and heat from buildings, requiring no energy consumption due to variations in wind pressure. The structure of the cross-ventilation flow significantly influences ventilation effectiveness. However, limited attention has been given to understanding the impact of a building's cross-section on the structure of cross-ventilation flow. This study aims to fill this gap by numerically investigating the cross-ventilation flow structure in an isolated cylindrical building. The numerical simulation results are validated against reported experimental data, indicating a negligible simulation error of 0.8 % in the volume ventilation rate. This attests to the accuracy of the numerical method in predicting cross-ventilation flow in isolated buildings. As airflow traverses the cylindrical building along the curved side walls, pressure loss diminishes, facilitating increased air inflow. This results in a more horizontal entry of the incoming jet compared to that in a square building. Analysis of Root-Mean-Square streamwise-velocity and turbulence kinetic energy reveals greater airflow fluctuation outdoors for the square building and increased turbulence indoors for the cylindrical building. Notably, the volume ventilation rate of the cylindrical building demonstrates an 8.3 % improvement. Furthermore, the air exchange rate in the cylindrical building surpasses that of the square building by 1.38 times.

Annual performance of solar chimney for a multi-story building based on Modelica multizone model

Integration of solar chimney is an effective passive strategy for facilitating fresh air flow and offering significant potential for building energy conservation. This research evaluates the optimal design and control strategy for a six-story office building that includes a solar chimney, focusing on stack effect ventilation and energy performance throughout the year. The ventilation rates in different configurations of solar chimney are compared to meet fresh air requirements. The results indicate that the separated solar chimney ensures uniform airflow across each floor, with ventilation standard-reaching rates ranging from 79.5 % to 88.6 %. Furthermore, maximums of air flow rate occur at each floor, with critical cavity width values of 0.5 m, 0.4 m, 0.4 m, 0.3 m, 0.3 m, and 0.2 m on the 1st to 6th floor, respectively. Under the condition of equal cavity inlet area, air flow rates rise with the increasing length/width ratios. Finally, when the outdoor temperatures fall beyond the design range, controlling excessive ventilation generated by solar chimney leads to a 19.6 % reduction in total energy consumption over the year, with 71.5 % of the savings during winter.