Ventilatory Efficiency Research Articles

The promotion effect of human activity intensity on displacement ventilation efficiency by the enhancement indoor thermal stratification

In a displacement ventilation system, the human body heat source plays a significant role and should not be overlooked. The intensity of human activity is a crucial factor in determining the amount of heat generated by the human body. In this work, the impact of thermal plumes generated by different levels of human activity intensity on the temperature stratification and ventilation efficiency in displacement ventilation system have been explored with experimental and numerical methods. The airflow patterns in the displacement air supply system under various levels of human activity intensity were simulated. The results show that under the same air supply speed, as the human activity intensity increasing from 125 W to 402 W, the phenomenon of temperature stratification becomes more pronounced. With the promotion of thermal plumes, the air flow velocity on the human body surface increases, leading to an enhancement in ventilation efficiency. Therefore, to elimination of the indoor thermal load, the air supply speed can be reasonably reduced according to the human activity intensity in the room, further enhancing the energy-saving effect of displacement ventilation.

Respiratory physiological mechanism of two types of equal-intensity inspiratory muscle training in stable patients with chronic obstructive pulmonary disease

PurposeThis study aimed to investigate the respiratory physiological changes resulting from short-term inspiratory resistance training (R-IMT) and inspiratory threshold training (T-IMT) in patients with chronic obstructive pulmonary disease (COPD) and to compare the mechanisms of the two training methods. Patients and methodsA total of 75 stable patients with COPD combined with inspiratory muscle weakness were randomly allocated to three groups: R-IMT (n = 26), T-IMT (n = 24), and control (n = 25). Before and after 8 weeks of inspiratory muscle training(IMT), cardiopulmonary exercise tests were conducted to assess respiratory patterns, respiratory central drive, exercise tolerance, and ventilation efficiency. ResultsAfter 8 weeks of IMT, Inspiratory muscle strength, represented by MIP (maximum inspiratory mouth pressure) and exercise capacity increased during exercise in both IMT groups (P < 0.05). In the R-IMT group, inspiratory time (Ti) prolonged (P < 0.05), tidal volume (Vt) increased (P < 0.05), ventilation efficiency (represented by ventilation-center coupling) increased (P < 0.05) during exercise. Conversely, the T-IMT group did not exhibit any of these changes after IMT (P > 0.05). ConclusionIn summary, the improvement in exercise tolerance was associated with an increase in inspiratory muscle reserve in both R-IMT and T-IMT. However, only R-IMT was associated with deeper and slower breathing, as well as improved ventilation efficiency.

Effect of Arm-Ergometry Versus Treadmill Supervised Exercise on Cardiorespiratory Fitness and Walking Distances in Patients With Peripheral Artery Disease: The ARMEX Randomized Clinical Trial.

To compare arm-ergometry and treadmill supervised exercise training on cardiorespiratory fitness and walking distances in patients with peripheral artery disease (PAD). ARMEX was a single-center, single-blinded, parallel group, non-inferiority trial enrolling symptomatic patients with PAD. Patients were randomized (1:1 ratio) to a 12-wk arm-ergometry (AEx) or standard treadmill (TEx) supervised exercise training protocol. The powered primary end point was the change in peak oxygen uptake (VO 2 ) at 12 wk, measured on a treadmill cardiopulmonary exercise test (CPX). Secondary outcomes included changes in VO 2 at the first ventilatory threshold (VT-1), ventilatory efficiency (ratio of minute ventilation [VE] to carbon dioxide production [VCO 2 ], VE/VCO 2 ), walking distances by CPX and 6-min walking test (6MWT), and self-reported walking limitations. Fifty-six patients (66±8yr; 88% male) were randomized (AEx, n =28; TEx, n =28). At 12 wk, VO 2peak change was not significantly different between groups (0.75 mL/kg/min; 95% CI, -0.94 to 2.44; P =.378), despite a significant increase only in AEx. VO 2 at VT-1 improved in both groups without between-group differences, and VE/VCO 2 slope improved more in AEx. The TEx attained greater improvements in walking distance by CPX (121.08 m; 95% CI, 24.49-217.66; P =.015) and 6MWT (25.08 m; 95% CI, 5.87-44.29; P =.012) and self-perceived walking distance. Arm-ergometry was noninferior to standard treadmill training for VO 2peak , and treadmill training was associated with greater improvements in walking distance. Our data support the use of treadmill as a first-line choice in patients with PAD to enhance walking capacity, but arm-ergometry could be an option in selected patients.

Study on the Influence of High-Altitude Helical Tunnel Curvature on Jet Fan Spatial Layout

During the operational ventilation process of high-altitude helical tunnels, the installation method of jet fans is a key factor in determining the ventilation efficiency of the tunnel. In this study, the CFD numerical simulation method is adopted to establish three-dimensional ventilation models of helical tunnels with different curvature radii. Through orthogonal experiments, the effects of tunnel curvature radius on the characteristics of the air jet flow field, under the coupled influences of factors such as lateral spacing of jet fans, vertical height of fans, longitudinal spacing, and lateral offset, are investigated. The results show that when R = 500 m, 600 m, 700 m, and 800 m, the longitudinal spacing has the most significant impact on ventilation efficiency, followed by vertical height, with lateral offset and fan spacing having the least impact. The optimal spacing and vertical height of the fan groups remain consistent under different curvature radii, at 1.25D (fan diameter) and 15 cm, respectively. The optimal longitudinal spacing of the fan groups is 90 m, 90 m, 135 m, and 90 m, respectively. Shifting the fan groups 0.25 to 0.75 m towards the inner side of the tunnel helix (for R &lt; 700 m) can optimize the flow field distribution within the tunnel. Finally, expressions for the relationship between the helical radius and the lateral offset and longitudinal spacing of the fan groups are established for the optimal installation parameters of fan spatial positions under different helical tunnel radii.

Physiological and clinical effects of trunk inclination adjustment in patients with respiratory failure: a scoping review and narrative synthesis

BackgroundAdjusting trunk inclination from a semi-recumbent position to a supine-flat position or vice versa in patients with respiratory failure significantly affects numerous aspects of respiratory physiology including respiratory mechanics, oxygenation, end-expiratory lung volume, and ventilatory efficiency. Despite these observed effects, the current clinical evidence regarding this positioning manoeuvre is limited. This study undertakes a scoping review of patients with respiratory failure undergoing mechanical ventilation to assess the effect of trunk inclination on physiological lung parameters.MethodsThe PubMed, Cochrane, and Scopus databases were systematically searched from 2003 to 2023. Interventions: Changes in trunk inclination. Measurements: Four domains were evaluated in this study: 1) respiratory mechanics, 2) ventilation distribution, 3) oxygenation, and 4) ventilatory efficiency.ResultsAfter searching the three databases and removing duplicates, 220 studies were screened. Of these, 37 were assessed in detail, and 13 were included in the final analysis, comprising 274 patients. All selected studies were experimental, and assessed respiratory mechanics, ventilation distribution, oxygenation, and ventilatory efficiency, primarily within 60 min post postural change.ConclusionIn patients with acute respiratory failure, transitioning from a supine to a semi-recumbent position leads to decreased respiratory system compliance and increased airway driving pressure. Additionally, C-ARDS patients experienced an improvement in ventilatory efficiency, which resulted in lower PaCO2 levels. Improvements in oxygenation were observed in a few patients and only in those who exhibited an increase in EELV upon moving to a semi-recumbent position. Therefore, the trunk inclination angle must be accurately reported in patients with respiratory failure under mechanical ventilation.

Evaluation of microclimate in dairy farms using different model typologies in computational fluid dynamics analyses

Ventilation plays a key role in the livestock buildings since it is important to guarantee a comfortable environment and adequate indoor air quality for the animals. Naturally ventilated barns are usually characterized by high variability in the ventilation conditions. Moreover, the ventilation efficiency can be very different in different areas of a barn because of the different presence of the animals. On the other hand, appropriate ventilation is an essential requirement to ensure animal welfare and efficient and sustainable production since a proper ventilation is the most efficient way to remove undesirable air pollutants and to obtain a comfortable microclimate for the welfare of the animals. In this regard, the computational fluid dynamic (CFD) simulations represent a powerful and useful tool because they can be used to assess ventilation and microclimate conditions. In this context, the present study has the object to assess whether different CFD modelling approaches (i.e. model with animals modelled as obstacles with closed volume and model enriched with cows modelled as obstacles capable of exchanging heat with the surrounding air volume) show differences in relation to the climatic conditions inside a naturally ventilated dairy barn. The comparison of the results, set in terms of indoor air temperature and air velocity contours of the two different models, arises that if a precise definition of the microclimatic features is necessary, in order to correlate them with production parameters or assess animal welfare indexes, thermal simplification is not acceptable since can lead to completely misleading conclusions and incorrect evaluations. Then, only adopting CFD models considering the animal thermal behaviour is possible to obtain effective information both for the proper barn system management and for the creation of useful tools driving the farmers' choices.

Effects of acute beetroot juice intake on performance, maximal oxygen uptake, and ventilatory efficiency in well-trained master rowers: a randomized, double-blinded crossover study.

Beetroot juice (BRJ) intake has been considered a practical nutritional strategy among well-trained athletes. This study aimed to assess the effects of BRJ intake on performance, cardiorespiratory and metabolic variables during a simulated 2000-meter rowing ergometer test in well-trained master rowers. Ten well-trained male master rowers (30-48 years) participated in a randomized, double-blind, crossover design for 3 weeks. In the first week, a researcher explained all the experimental procedures to the participants. In the next two weeks, the participants were tested in 2 rowing ergometer sessions, separated from each other by a 7-day washout period. In both strictly identical sessions, the participants randomly drank BRJ or placebo (PL) 3 hours before the start of the tests. Subsequently, the participants carried out the 2000-meter rowing ergometer tests. Oxygen saturation and blood lactate measurements were performed before starting (pretest) and at the end of the test (posttest). Performance parameters and cardiorespiratory variables were recorded during the rowing ergometer test. An improvement in time trial performance was observed, with a mean difference of 4 seconds (90% confidence limits ± 3.10; p ≤ 0.05) compared to PL. Relative and absolute increased (mean difference of 2.10 mL·kg-1·min-1, 90% confidence limits ± 1.80; mean difference of 0.16 L·min-1 90% confidence limits ± 0.11, respectively; p ≤ 0.05) compared to PL. No ergogenic effect was observed on ventilatory efficiency and blood lactate concentrations after BRJ intake. Acute BRJ intake may improve time trial performance as well as in well-trained master rowers. However, BRJ does not appear to improve ventilatory efficiency.

Clinical features and associated factors of impaired ventilatory efficiency: findings from the ECOPD study in China

BackgroundImpaired ventilatory efficiency during exercise is a predictor of mortality in chronic obstructive pulmonary disease. However, little is known about the clinical features and associated factors of impaired ventilatory efficiency...

Differences in Exercise Capacity, Ventilatory Efficiency, and Gas Exchange between Patients with Pulmonary Arterial Hypertension and Chronic Thromboembolic Pulmonary Hypertension Residing at High Altitude.

Cardiopulmonary exercise testing (CPET) assesses exercise capacity and causes of exercise limitation in patients with pulmonary hypertension (PH). At altitude, changes occur in the ventilatory pattern and a decrease in arterial oxygen pressure in healthy; these changes are increased in patients with cardiopulmonary disease. Our objective was to compare the response to exercise and gas exchange between patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) residing at the altitude of Bogotá (2640 m). All patients performed an incremental CPET with measurement of oxygen consumption ( ), dead space (VD/VT), ventilatory equivalents (VE/ ), and alveolar-arterial oxygen gradient ( ). test and one-way analysis of variance were used for comparisons between PAH and CTEPH. We included 53 patients, 29 with PAH, 24 with CTEPH, and 102 controls as a reference of the normal response to exercise at altitude. CTEPH patients had a higher New York Health Association (NYHA) functional class than PAH (p = 0.037). There were no differences between patients with PAH and CTEPH in hemodynamics and % of predicted (67.8 18.7 vs. 66.0 19.8, p 0.05), but those with CTEPH had higher dyspnea, VD/VT (0.36 0.09 vs. 0.23 0.9, p 0.001), VE/ (45.8 7.1 vs. 39.3 5.6, p 0.001), and (19.9 7.6 vs. 13.5 7.6, p 0.001) than PAH patients. At altitude, patients with PH present severe alterations in gas exchange during exercise. There were no differences in exercise capacity between PAH and CTEPH, but patients with CTEPH had more dyspnea and greater alterations in gas exchange during exercise. CPET made it possible to identify alterations related to the pathophysiology of CTEPH that could explain the functional class and dyspnea in these patients.

Assessment of cardiopulmonary capacity in deconditioned athletes because of knee injury.

An athlete's career inevitably goes through periods of forced physical exercise interruption like a knee injury. Advanced echocardiographic methods and cardiopulmonary exercise testing (CPET) are essential in evaluating athletes in the period elapsing after the injury. However, the feasibility of a maximal pre-surgery CPET and the capacity of resting advanced echocardiographic techniques to predict cardiorespiratory capacity still need to be clarified. We evaluated 28 non-professional athletes aged 18-52, involved in prevalently aerobic or alternate aerobic/anaerobic sports activities, affected by a knee pathology with indications for surgical treatment. The evaluation was performed at rest by trans-thoracic echocardiography, including global longitudinal strain (GLS) and myocardial work (MW) assessment, and during exercise by CPET. The percent-predicted peak oxygen consumption (peak VO<inf>2</inf>%) was 82.8±13.7%, the mean respiratory exchange ratio was 1.16±0.08, and the mean ventilation/carbon dioxide (V<inf>E</inf>/VCO<inf>2</inf>) slope was 24.23±3.36. Peak VO<inf>2</inf>% negatively correlated with GLS (r=-0.518, P=0.003) and global wasted work (GWW) (r =-0.441, P=0.015) and positively correlated with global work efficiency (GWE) (r=0.455, P=0.012). Finally, we found that the V<inf>E</inf>/VCO<inf>2</inf> slope during exercise was negatively correlated with GWE (r=-0.585, P=0.001) and positively correlated with GWW (r=0.499, P=0.005). A maximal CPET can be obtained in deconditioned athletes because of a knee injury, allowing a comprehensive functional pre-surgery evaluation. In these patients, peak VO<inf>2</inf> is reduced due to decreased physical activity after injury; however, a lower cardiopulmonary efficiency may be a concause of the injury itself. In addition, we demonstrated that the MW indexes obtained at rest could predict exercise capacity and ventilatory efficiency as evaluated by CPET.

Ventilation performance study of a high-speed train cabin based on displacement ventilation and mixed ventilation

Indoor ventilation systems play an important role in controlling energy consumption, thermal comfort, and airborne pollutants. This work is concerned with whether the combination of displacement and mixed ventilation can overcome these systems' respective shortcomings to improve the ventilation performance of high-speed train cabins. This work is based on computational fluid dynamics. The results show that when more fresh airflow enters the compartment from the top vents, the flow field is mainly driven by mechanical forces, and two vortices are formed. When more fresh airflow enters the compartment from the bottom vents, the flow field is mainly driven by thermal buoyancy. Meanwhile, the airflow mainly spreads upward, with lower cooling energy consumption, lower wind speed, higher ventilation efficiency, and smaller longitudinal diffusion of pollutants, but increased temperature difference. When the ratio of top and bottom supply air flow is 75%/25%, thermal comfort can be improved, while balancing energy consumption and air quality. If there was a disease outbreak, the flow rate of the bottom air supply could be increased appropriately. To further improve the ventilation performance, on the one hand, it is necessary to appropriately increase the temperature of the bottom air supply, and on the other hand, it is necessary to avoid short-circuiting of the airflow, due to the lack of synergy between thermal buoyancy and mechanical force. The results of the study can provide a reference for safeguarding passengers and improving the ventilation design of high-speed trains.

Assessment of cardiorespiratory function in adolescent athletes affected by COVID-19: a comparative analysis

Background and Study Aim. Given the global spread of COVID-19 and its profound effects on public health, understanding its impact on the physical health and performance of young athletes is crucial for developing guidelines to support their recovery and well-being. The goal of this research was to assess the impact of the COVID-19 infection and possible consequences on the functional abilities of schoolchild athletes, and determine whether there are differences compared to their peers who did not suffer the infection. Material and Methods. This study involved 100 teenagers (median age 15.7±1.167), who engage in two different sports (basketball and soccer), divided into two groups. The first group comprised young athletes (n=53, age 15.79±1.854) who had contracted COVID-19 and underwent 14 days of home isolation. The second group consisted of healthy child athletes (n=47, age 15.60±1.313). Participants underwent a comprehensive pre-participation sports medical examination, which included a cardiopulmonary exercise test (CPET) on a treadmill. CPET assessed various physiological parameters: maximum oxygen consumption (VO2max); heart rates at the first and second ventilatory thresholds (HR at VT1 and HR at VT2); respiratory exchange ratio (RER); maximal pulmonary ventilation (VEmax); ventilatory efficiency (VE/VCO2); oxygen pulse (O2/HR); maximum heart rate (HRmax); three-minute heart rate recovery; and potential electrocardiographic changes. Results. The results indicate that COVID-19 infection has led to statistically significant impairments in the cardiorespiratory functions of child athletes. Notably, there were significant reductions in maximum oxygen consumption (VO2max), maximal pulmonary ventilation (VEmax), oxygen pulse (O2/HR), as well as heart rates at the first ventilatory threshold (HR at VT1), maximum heart rate (HRmax), and heart rate recovery following maximal effort, all demonstrating p-values less than 0.05. Conclusions. The assessed parameters demonstrated that the functions were statistically significantly impaired in child athletes who had recovered from COVID-19 compared to their healthy peers of the same age. However, the infection appeared to have a minimal impact on heart rate variability at ventilatory thresholds. These findings offer valuable insights for coaches and sports medicine physicians in adjusting training programs and supporting the rehabilitation process for young adolescent athletes resuming their training after recovering from COVID-19.

Study on the Influence of Some Ventilation Parameters on Dust Dispersion in Heading Face Coal Mine Using CFD Numerical Model

Coal dust is one of the environmental factors that seriously affect the health of workers as well as the mining equipment in underground coal mines. At present, coal dust is commonly generated during drilling, blasting, excavation, and transportation processes in mining operations. During mining blasting processes, coal dust is generated with varying particle sizes and high concentration levels. High concentrations of dust will affect mining operations and increase the ventilation time required for mining faces. In addition, coal dust exists in suspended form in the roadway and is harmful to human health, especially fine dust particles that have a negative impact on work efficiency. To improve ventilation efficiency and eliminate coal dust, this article presents a CFD-DPM numerical modeling method that integrates a DEM collision model based on the finite element method to analyze the motion characteristics of airflow and dust particles in the mine tunnel, while considering collisions between particles and between particles and walls. The article analyzes the distribution of wind speed, the dispersion of dust in the space around the roadway, and dust concentrations at distances of 1 m, 3 m, and 6 m from the working personnel and at a position 1.5 m above the roadway floor, corresponding to the breathing zone of the workers, with varying parameters such as velocity and duct position. The results indicate that with a wind velocity of V = 18 m/s and an air duct height h = 3.0 m, the best dust reduction results are achieved, and they provide theoretical guidance for selecting and optimizing ventilation parameters in dust control.

Effects of Cardiopulmonary Rehabilitation on Cardiorespiratory Fitness and Clinical Symptom Burden in Long COVID: Results from the COVID-Rehab Randomized Controlled Trial.

To investigate the effectiveness of an eight-week cardiopulmonary rehabilitation program on cardiorespiratory fitness (VO2peak) and key cardiopulmonary exercise test measures, quality of life, and symptom burden in individuals with Long COVID. Forty individuals with Long COVID (mean age 53 ± 11 years), were randomized into 2 groups: 1/ Rehabilitation group: centre-based individualized clinical rehabilitation program (8 weeks, 3 sessions per week of aerobic and resistance exercises, and daily inspiratory muscle training) and 2/ Control group: individuals maintained their daily habits during an eight-week period. There was a significant difference between groups in mean VO2peak improvement (p = 0.003). VO2peak improved significantly in the rehab group (+2.7 mL.kg.min 95%IC:+1.6 to +3.8 p < 0.001) compared to the control group (+0.3 mL.kg.min 95%IC:-0.8 to +1.3 p = 0.596), along withVE/VCO2 slope (p = 0.032) (-2.4 95%IC:-4.8 to +0.01 p = 0.049 and + 1.3 95%IC:-1.0 to +3.6 p = 0.272 respectively) and VO2 at first ventilatory threshold (p = 0.045). Furthermore, all symptom impact scales improved significantly in the rehabilitation group compared to the control group (p < 0.05). An individualized and supervised cardiopulmonary rehabilitation program was effective in improving cardiorespiratory fitness, ventilatory efficiency, and symptom burden in individuals with Long COVID. Careful monitoring of symptoms is important to appropriately tailor and adjust rehabilitation sessions.

Effects of Daily Physical Activity on Exercise Capacity in Chronic Obstructive Pulmonary Disease.

Background and Objectives: In adults, 150 to 300 min a week of moderate-intensity physical activity is the recommended daily level to maintain or improve fitness. In subjects with chronic obstructive pulmonary disease (COPD), reductions in daily physical activity (DPA) amounts are related to clinically significant outcomes. In this study, we ascertain whether or not COPD patients, when clustered into active (DPA ≥ 30 min a day, 5 days a week) and inactive (DPA < 30 min a day, 5 days a week), may differ in exercise capacity, as assessed by a cardiopulmonary exercise test (CPET). Materials and Methods: A large sample of clinically stable COPD patients was retrospectively recruited and then underwent spirometry and an incremental ramp protocol 5-15 watts/min CPET. DPA was assessed by a questionnaire. Results: A total of 83 (female 25%, age range 41-85 y) active and 131 (female 31%, age range 49-83 y) inactive participants were enrolled. They were similar in age, sex distribution, body mass index (BMI) and in spirometry. The two groups were significantly different in dyspnea on exertion, as assessed by the modified Medical Research Council (mMRC), and in cardio-metabolic parameters, but not in ventilatory ones, as confirmed by the CPET. Conclusions: COPD patients experiencing physical activity of at least 30 min a day, 5 days a week, showed a greater exercise capacity and an improved cardiovascular response to exercise, when compared to inactive ones. Active and inactive participants did not differ in terms of airflow obstruction severity as well as in dynamic hyperinflation and ventilatory inefficiency during exercise. This study further suggests the benefits of regular physical activity in COPD.

Removal efficiency of restroom ventilation revisited for short-term evaluation

Ventilation efficiency or contaminant removal efficiency is often evaluated using the ratio between the concentrations in the exhaust air and the room air. This ratio does not truly represent the expectation of ventilation in restrooms, where dynamic airflow fields and sources are more typical. This study focuses on a short-term (10 min) pollutant removal percentage in a residential restroom featuring a dynamic airflow field, particularly with the onset of window-induced stack ventilation during toilet uses. Thirteen ventilation scenarios of a residential restroom were studied using the numerical method that was validated by a mock-up experiment. The scenarios differed in the operation of the exhaust fan and window. Results show that the 10-min pollutant removal percentage of a typical exhaust ventilation system at 10 h-1 air change rate (ACH) is only 68.5%. Under exhaust ventilation, opening the window can introduce both adverse short circuit and favorable stack ventilation depending on the difference between the indoor and outdoor temperatures. As the temperature difference increases from 0 to 12.5 °C, the removal percentage increases from below 50%, a drop due to short circuit, to above 98% thanks to a tripled ventilation rate. The human thermal plume has notable effect on the removal percentage, but its effect can be neglected with the presence of stack ventilation. The hybrid ventilation strategy has impact on perceived air quality and thermal comfort. When the outdoor air is colder, opening the window under exhaust ventilation may increase the current sitting user’s exposure to the self-produced pollutants but can reduce the exposure of the next immediate standing user. In addition, opening the window in cold days will make the toilet user thermally uncomfortable with reduced local temperatures and increased airflow velocities. The study highlights the importance of using the short-term removal percentage to evaluate the performance of restroom ventilation.

Numerical investigation of different building configurations for improving outdoor spatial ventilation conditions in strip-type residential neighbourhoods

Understanding the influence of building configurations on spatial wind flows is essential for architects to optimize urban ventilation in the design process. However, the design changes in urban form are abundant and many detailed design variations were not examined. This study aims to explore the potential of spatial forms to improve wind conditions in strip-type residential neighbourhoods. Several specific building design variations were investigated using computational fluid dynamic (CFD) simulations. The ventilation performance indicators including spatial averaged wind velocity (<V>), purging flow rate (PFR), and net escape velocity (NEV) were adopted to quantify the effects of design changes on spatial ventilation efficiency of overall and local residential spaces. The results show that the buildings with staggers of residential units could have a noticeable impact on the overall residential space, especially when the wind direction is inclined or parallel to the corridor space between the strip buildings. The PFR and < V > values of the residential space can be reduced by 19% and 18%. Building length variation and square setting can be beneficial to the ventilation conditions of the local residential spaces.

Impact of ventilation efficiency on restraining hazardous toilet plume post-flushing in indoor environments

This study analyzed the hybrid ventilation efficiency of indoor toilet plumes generated post-flushing with various designs. Single-sided natural ventilation and hybrid ventilation were numerically investigated to determine the impact of vent locations commonly found in multistorey buildings. An in-situ experiment was performed to identify the size distribution of the plume with time series. A computational fluid dynamics model based on the Reynolds-averaged naiver-Stokes equations and baseline k-ω turbulence equations was used to predict aerosol pollutant transmission. The aerosol-laden particles receded gradually impacted by the convection of the ambient source. Besides flush volume, temperature and ventilation scenarios were also related to the generation and droplet transmission. The results indicated that the ventilation rates were generally increased with decreased residence time if the turbulence was not suppressed. This study suggested that appropriate ventilation design could significantly reduce the average particle residence time, in which case it could also reduce the rate of virus infection.

Experimental study on the periodic pulsating ventilation by fluidic oscillator on pollutant dispersion and ventilation performance in enclosed environment

Ventilation plays an essential role in creating healthy and comfortable indoor environment, while adopting unsteady airflow field has the potential to improve the indoor air mixing effect, which is conducive to the dispersion and eventually the discharge of indoor pollutants. A fluidic oscillator capable of producing periodic pulsating airflow is employed to conduct a ventilation experiment to test the performance of such unsteady flow regime. The distribution of indoor pollutants at different source locations is compared under both steady and unsteady ventilation mode. The assessment of the fluidic oscillator ventilation system performance in eliminating pollutants involves the concentration exceedance rate, the decay of indoor pollutant concentration, and the resultant ventilation efficiency. At a relatively lower air supply rate, the fluidic oscillator device can enhance indoor air mixing, leading to a reduction of the peak indoor pollutant concentration. Additionally, the fluidic oscillator air terminal significantly prolongs the time needed to reach the pollutant concentration threshold, increases ventilation efficiency, and improves indoor air quality.

The effect of the physical characteristics of atriums on the natural ventilation of buildings

This study explores the impact of atrium designs on natural ventilation and energy efficiency in buildings, focusing on three distinct types of atriums: vertical atriums promoting stack effects, horizontal atriums facilitating cross ventilation, and atriums with varying glazing areas and materials. Each atrium type was examined through the lens of geometry and size, orientation, material specifications, and internal configuration to determine how these factors influence their effectiveness in enhancing natural ventilation and optimizing energy performance. The methodology adopted a comparative analytical approach, leveraging both theoretical and empirical assessments. Computational Fluid Dynamics (CFD) simulations and architectural modeling were utilized to measure airflow patterns, temperature gradients, and ventilation rates across different atrium configurations. This quantitative analysis was complemented by a qualitative assessment of material impacts and spatial arrangements within the atriums. Results indicate that the physical characteristics of an atrium significantly affect its ventilation efficiency and thermal behavior. Vertical atriums, with their tall structures, were found to effectively utilize the stack effect, particularly when combined with high thermal mass materials such as concrete and brick. These materials help stabilize temperature fluctuations, enhancing the natural cooling and ventilation processes. Horizontal atriums, aligned perpendicular to prevailing winds, maximize cross ventilation, which is further optimized by using low thermal mass materials like wood and gypsum that respond quickly to temperature changes. Atriums with extensive glazing areas benefit from advanced glazing materials that manage solar gain and maximize natural light, thus improving overall energy efficiency. This research provides actionable insights into atrium design, emphasizing the importance of tailored architectural strategies to leverage natural environmental forces. It contributes to the field of sustainable architecture by offering a comprehensive framework that can guide the design of atriums to achieve optimal ventilation and energy performance in various climatic conditions. Keywords: Atrium Design; Natural Ventilation; Energy Efficiency; Sustainable Architecture; Thermal Behavior; Computational Fluid Dynamics (CFD).