Ventilation Performance Research Articles

Research on a novel method of air distribution to create a uniform indoor environment in a long and narrow building

Because people work a long time in buildings, good indoor thermal environments and air distributions have attracted increased amounts of attention. To improve the indoor thermal environment and air quality, an effective ventilation strategy must be used. In the air conditioning of a building, the air distribution has been identified as a significant factor that affects the indoor thermal environment. A novel method for air distribution was presented to create a uniform indoor environment along the room length direction. In this study, numerical simulations were carried out to analyse the airflow pattern and performance of the sidewall air supply (SAS) and the sidewall air supply with deflector (SASD). Orthogonal experiments were conducted to study the airflow distribution law of the deflector. The ventilation performance of the two air supply modes was evaluated by air velocity distribution, temperature distribution, horizontal temperature difference, age of air, and other evaluation indicators. The results indicate that the horizontal air temperature differences in the SASD at three heights are 46.05%, 16.44%, and 26.51% lower than those in the SAS, which has a better energy-saving effect. Moreover, the indoor air distribution performance was obtained under three influencing factors: the gap width from the deflector to the ceiling, the horizontal position, and the length of the deflector. A better deflector optimization scheme was obtained. Experimental research was carried out to verify the indoor air distribution of the SASD. This research can provide a reference for the innovative design of indoor air supply systems

Impact of Window Opening Shapes on Wind-Driven Cross Ventilation Performance in a Generic Isolated Building: A Simulation Study

Both environmental concerns and sustainable development goals have led to the search for alternative energy-efficient solutions. Natural ventilation, a crucial aspect of energy-efficient building design, reduces dependence on mechanical systems and regulates indoor air quality and temperature using natural forces. It improves indoor air quality, reduces energy consumption, and lowers operating costs. This paper presents a computational fluid dynamics analysis of natural cross-ventilation in an isolated building with varying window opening geometries. u/uref showed a marked decrease in triangular geometries, while trapezoidal and reference geometries exhibited comparable declines. The airflow velocity profile revealed a U-shaped curve, with reductions observed within 0

Uncertainty quantification: For an IAQ and energy performance assessment method for smart ventilation strategies

In new low-energy buildings or buildings after thermal refurbishment, the envelope high airtightness could have an impact on air renewal and could decrease the indoor air quality (IAQ). In this context smart-ventilation systems with variable airflows could play a role in providing better IAQ without compromising the energy performance.However, smart-ventilation strategies are quite recent, and their benefits need to be clearly quantified. This article, proposes to quantify the uncertainty of a recent multi-criteria performance assessment method, using global RBD-FAST sensitivity analysis. The impact of the pollutant emissions scenarios, model input parameters and ventilation strategies is assessed.Five ventilation systems were studied: two constant airflow, one humidity-controlled and two humidity/CO2 controlled, applied on a French low-energy house. 2500 simulations were performed to calculate 504 sensitivity indices across 12 input variables and 9 output performance indicators. The sensitivity analysis shows that occupant bio-effluent, formaldehyde and PM2.5 emissions rates are responsible for 11 %–87 % of the uncertainty for the IAQ performance indicators. The PM2.5 deposition velocity parameter is responsible for 50 % of the uncertainty on the PM2.5 indicator, which was an unknown impact. In addition, the benefits of humidity-controlled ventilation were highlighted regarding energy performance, with, in average, 20 % lower heat-loss compared to constant airflow ventilation. Moreover, smart-ventilation provides clear IAQ benefits without drastically increasing the energy demand. This work demonstrates the potential of the proposed evaluation method for ventilation performance assessment.

Study on the Natural Ventilation Model of a Single-Span Plastic Greenhouse in a High-Altitude Area

The natural ventilation model plays a crucial role in greenhouse environmental control. It has been extensively studied by previous researchers, but it is limited to low-altitude areas. This study established a numerical model of single-span plastic greenhouses in high-altitude areas. The model was validated using measured data, showing a good agreement between the measured and simulated values. By setting boundary conditions based on on-site monitoring data, ventilation rates were extracted under different conditions for numerical simulations. Through nonlinear fitting, an empirical formula for natural ventilation rates, with a determination coefficient (R2) of 0.9724, was derived. The formula was validated through an energy balance analysis of indoor air. Different ventilation opening sizes were simulated to derive an empirical formula for natural ventilation rates based on opening size. Building on this, the relationship between plant height and ventilation rate was analyzed. As the dominant factors of natural ventilation change with environmental fluctuations, this study also proposed the threshold wind speed for wind pressure ventilation, thermal pressure ventilation, and coupled ventilation, filling the knowledge gap in relevant ventilation rate calculations. This is the first time that a natural ventilation model of single-span plastic greenhouses in high-altitude areas has been proposed, providing the basis in terms of modeling for the further development of local facility agriculture.

Experimental comparison of aerosol transmission in displacement ventilation and mixing ventilation in a meeting scenario

The performance of displacement ventilation (DV) and mixing ventilation (MV) in aerosol contamination control was compared. The considered contamination was an aerosol emitted from a person in meeting scenarios of two and four persons. The experiments were carried out in a full-scale room measuring 4.4 m × 5.2 m × 2.9 m. Particle counting was carried out at 41 measurement points in the room to assess the concentration field of particles in the room and in the inhalation zone. The influence of the supply airflow rate and the number of activated thermal mannequins on the contaminant removal effectiveness were examined. The main conclusion is that the DV system was superior to the MV system in reducing contamination. An enhanced contaminant removal effectiveness of displacement ventilation was observed for all supply air flow rates and increased with higher airflow rates. At lower airflow rates, contamination in the inhalation zone was reduced by 40% compared to mixing ventilation, while at higher flow rates, the reduction surpassed 50%. This study highlights the advantages of displacement ventilation in terms of contamination control, infection prevention and energy efficiency, emphasising the importance of ventilation system selection for indoor environments, particularly those where airborne transmission risks are prevalent.

Performance and safety of volume guarantee ventilation in neonates using the fabian ventilator, a multicenter study.

To evaluate the performance (i.e., agreement between set and measured parameters) and safety (adverse events, device malfunctions, and ventilator alarms) of the fabian HFOi neonatal ventilator in volume guaranteed (VG) mode during conventional ventilation. To analyze the impact of leakage around the endotracheal tube and the set maximum allowed inflating pressure (Pmax). Prospective multicenter observational study. Clinical and ventilator data were collected from 71 infants receiving VG ventilation for ≥12 h in four neonatal intensive care units (NICUs). Ventilator settings, parameters, and alarms were downloaded with 0.5 Hz sampling rate. Data from 4,341 h of ventilation were analyzed. The median (interquartile range, IQR) of the absolute difference between the target and measured expired tidal volume was 0.76 (0.51-1.16) mL/kg. It was less when leak was <50% (median 0.36, IQR: 0.25-0.64 mL/kg, p < .001) and even less when the required peak inflating pressure (PIP) was also below Pmax (median: 0.09 mL/kg, IQR: 0.00-0.16 mL/kg, p < .001). On NICUs setting Pmax higher, tidal volume was maintained significantly closer to target. In 56 patients VG was continued until extubation. Two ventilator malfunctions were reported, none of them resulting in patient harm. "Tidal volume not reached" alarm occurred 32 times hourly, usually lasting for <10 s. The fabian HFOi ventilator maintains tidal volume close to its target, particularly when leak is <50% and when PIP is below Pmax. In most patients VG can be continued until extubation. Despite frequent ventilator alarms, ventilator malfunctions occur very rarely.

Natural ventilation in large spaces: CFD simplified model validated with full-scale experimental data of Roman Baths

This study addresses the escalating need for energy-efficient and well-ventilated buildings by examining natural ventilation in large spaces. Validation of a CFD model was pursued through in-site experiments at the Roman Baths Museum in Chaves, Portugal. A sensitivity analysis aimed to determine the optimal number of monitoring points for model validation, crucial for establishing procedures in large-volume settings. Findings emphasized the feasibility of using a minimal number of monitored points, notably with a 3 × 3 test point arrangement, showcasing consistent temperature variations with low relative errors (0.50 %–1.75 %). Furthermore, the validated model assessed ventilation performance under diverse operational conditions, revealing slight enhancements in experimental settings, including an increase in air change rate (2.4 vs. 2.2 ACH) and a decrease in buoyancy dominance (Richardson number 197.3 vs. 241.3) compared to design conditions. Quantitative analysis highlighted similar temperature and velocity trends, with greater stratification in experimental conditions (temperature ratios 0.12 to 0.36 vs. 0.10 to 0.32). Qualitative assessments align with the quantitative analysis and enable the identification of stagnation zones and airflow distribution patterns. These findings affirm the methods' reliability in analysing ventilation in large spaces naturally ventilated, validating the model across diverse contexts, despite fewer data points.

Reinterpretation of Passive Cooling Strategies in Hot And Dry Climate Traditional Architecture: Vents in The Building

The building sector is among the most critical factors affecting environmental sustainability due to its impacts, such as energy consumption and greenhouse gas production. The reasons for energy consumption and greenhouse gas production in the building sector may vary according to climatic characteristics. In hot and arid climate regions, a significant portion of energy consumption is caused by indoor cooling, especially since the focus is on reducing the indoor temperature. In the periods when traditional architecture was developed, the lack of technological products that would increase energy consumption was effective in providing indoor air conditioning with passive design strategies. This study aims to identify the building openings for natural ventilation and cooling used in the traditional architecture of hot and dry climates and to analyze and evaluate their modern interpretations. A total of 235 award-winning projects were analyzed, and 21 were included in the study. In this context, it was determined that 16 different strategies used in traditional architecture were re-interpretation, and their modern interpretations were analyzed through award-winning projects. The traditional passive design strategies identified in this context have been adapted to modern architecture in 18 types. Wind orientators come to the forefront. In addition, it was determined that the strategies adapted to modern architecture are generally integrated. This study guides modern interpretations of traditional passive design strategies for sustainable building design.

Fire Resistance Performance of Constrained H-Shaped Steel Columns with Uneven Vertical Temperature Distributions

Steel columns, which are widely used in building frameworks and spatial structures, are susceptible to capacity degradation during fires, potentially leading to the overall collapse of buildings. Existing research on the fire resistance of steel columns assumes that the temperature loads encountered by steel columns are evenly distributed vertically. However, real-world fire scenarios often feature significant vertical temperature differences. Therefore, this study comprehensively investigated these variations to derive a temperature curve that accurately represents real fire conditions. Subsequently, the fire resistance limits of steel columns were studied using this temperature curve, leading to a revised calculation formula for the critical fire resistance temperatures of steel columns. The following conclusions were drawn: (1) Nonuniform longitudinal temperature distributions are influenced by parameters such as the fire source distance, the heights of ventilation openings, and the distance between a vent and the temperature measurement point. Among them, the fire source distance has the greatest impact, with the maximum longitudinal temperature difference reaching over 500 °C. (2) Variations in the load ratio and longitudinal temperature differences alter the failure positions of steel columns, reducing their critical temperatures by up to 200 °C. (3) The revised critical fire resistance temperature formula is more accurate and safer compared with that outlined in the “Technical Code for Fire Protection of Steel Structures” (GB51249-2017). These findings offer valuable insights for the fire designs of steel columns.

An evaluation of the ventilation performance using a new structure of plastic low tunnels

An evaluation of the ventilation performance using a new structure of plastic low tunnels

Experimental study on the transitional behavior of the room fire under sub-atmospheric pressures

Fuel diffusion combustion and flame behavior within a confined space is a fundamental scientific problem in the energy and combustion field, it involves complicated chemical reaction, fire behavior, thermal dynamics, heat transfer, room-opening flowing and sub-processes of over-ventilated and under-ventilated room fire. However, previous classical knowledges and models about it are usually at standard atmospheric pressure (100 kPa), no work considers the fire evolution and flame behavior within the room for various sub-atmospheric pressures. In this paper, the experiment is carried by utilizing a 0.3 m × 0.3 m × 0.3 m reduced-scale cubic room with an opening of various dimensions, and using propane as fuel to simulate fuel combustion inside, which was placed at the Low Pressure Chamber creating various atmospheric pressures. The flame behavior and temperature evolution within the room was recorded and measured with 693 experimental conditions. The experimental results show that, (1) the air inflowing rate through opening into room and heat release rate within the room increase with atmospheric pressure; (2) the flame extinction or reaching well-mixed condition are more easily occurred for lower atmospheric pressure and opening dimension. These characteristic parameters and fire behaviors could be well described by new corrected opening ventilation factor involving effect of atmospheric pressure and the opening dimension. The research work fills the gap in basic scientific research of building fire at sub-atmospheric pressures, which also has important practical applicability of urban building fire protection design code (such as the materials in wall) in different altitudes, room fire suppression, and protecting urban safety.

Air pollutant removal performance using a BiLSTM-based demand-controlled ventilation method after tunnel blasting

Efficient tunnel ventilation is essential for ensuring construction safety and protecting personnel health during tunnel construction. This study proposes a demand-controlled ventilation (DCV) method on the basis of deep learning algorithm to both improve pollutant removal efficiency and reduce energy consumption. The DCV method utilizes a two-layer bidirectional long short-term memory algorithm (BiLSTM) to predict pollutant concentrations. The air volume is dynamically adjusted based on the gaseous pollutant removal requirements. The coefficient of ventilation performance (COVP) is proposed to evaluate the performance of two ventilation methods (DCV and constant air-volume ventilation (CAV)) through computational fluid dynamics (CFD) simulations. The results show that the DCV results in a lower maximum average CO concentration and higher removal efficiency in the heading area (372.3 mg/m3) than the CAV does (404.1 mg/m3). The fan's energy consumption of DCV is 64.6% lower than that of CAV during a 1000 s ventilation period. The COVPs for both methods exhibit temporal variation and achieves their maximums (2.25 for DCV and 0.741 for CAV) after reaching the constraint conditions (air volume threshold). The DCV method expedites pollutant elimination, reduces construction waiting period, and minimizes energy consumption, providing a novel application of a deep learning algorithm in construction engineering.

Wind tunnel experiment on cross-ventilation of generic isolated building with various roof shapes: Impact of roof pitch and eaves

This study examined the effects of roof shape, specifically roof pitch and eaves, on cross-ventilation performance through wind tunnel experiments that measure static pressure on walls and the detailed wind velocity distribution for isolated building models with basic roof geometries. A flat roof, a gable roof, and two types of shed roof with different orientations were compared. The buildings with a flat or shallow roof pitch (15°) showed no significant change in the pressure difference between windward and leeward facades. However, a steeper roof pitch (30°) caused a significant increase in pressure difference, especially for the shed roof that ascends in the wind direction (shed-A roof). This was caused by larger projected building areas creating stronger recirculation zones behind the building, leading to lower pressure on the leeward facade. The shed-A roof with a pitch of 30° had the best ventilation performance among the tested cases. Eaves generally reduced pressure differences, except for the shed-A roof. The effect of eaves was weaker than reported in previous studies. The experimental results obtained in this study can serve as a validation database for a more detailed study of this problem using computational fluid dynamics.

Ventilation performance of induction displacement units in indoor spaces within cold regions

Efficient ventilation systems play a crucial role in reducing occupants' exposure to indoor contaminants, including particles potentially carrying viruses like SARS-CoV-2. Displacement ventilation systems have demonstrated their effectiveness in improving indoor air quality during cooling modes. However, traditional displacement ventilation systems often struggle to achieve satisfactory distribution of contaminant concentrations during heating modes. To address this issue, this study focused on enhancing the ventilation performance of a dual-coil displacement-induction unit. Through a combination of experimental measurements and computational fluid dynamic (CFD) techniques, the study examined airflow and contaminant concentration distributions in an environmental chamber conditioned by these units. The results demonstrated good agreement between measured and simulated data, validating the CFD model. Further evaluation in a 25-occupant classroom under cold outdoor conditions showed that the dual-coil unit could achieve satisfactory ventilation performance in heating modes with proper design, comparable to traditional displacement ventilation in cooling modes. Additionally, the unit's versatility allows it to accommodate a wide range of air conditioning applications, from heating to cooling, making it a promising solution for displacement ventilation in various environments.

Evaluating the effects of envelope features on the pollutant distribution and ventilation performance by CFD simulations and scaled outdoor experiments

Previous studies on the effects of envelope features on ventilation performance have neglected the buoyancy effect or simplified it as a uniform surface heating effect. However, envelope features can create a shading effect that changes the temperature distribution and enhances the buoyancy effect, thus resulting in inaccurate findings. We conducted computational fluid dynamics (CFD) simulations based on scaled outdoor experiments to investigate the effects of different envelope features (balconies, overhangs, and wing walls) on pollutant dispersion and ventilation performance. The buoyancy effect created a new local vortex and changed the wind flow pattern at the base of the flat-facade and wing wall street canyons. The age of the air at the base of the flat-facade, balcony, overhang, and wing wall street canyons increased by 30.23 %, 20.45 %, 21.74 %, and 30.95 %, respectively. Moreover, when investigating the effects of envelope features on ventilation performance while ignoring the buoyancy effect, there was a high error rate in the ventilation performance, and the rates were as follows: wing wall (24.03 %) > flat-facade (23.20 %) > overhang (18.56 %) > balcony (14.05 %). This study provides a suitable methodology for investigating the effects of different envelope features on pollutant dispersion and ventilation performance in two-dimensional street canyons.

Numerical Investigation of Cross Ventilation Flow in A Gable Roof Building with Asymmetric Opening Positions

Natural ventilation can be a suitable alternative to mechanical ventilation as it is cost-effective and environmentally friendly. Therefore, an effective design of the natural ventilation system is very crucial. In this work, an attempt has been made to investigate the impact of opening positions and roof pitch on the performance of wind-induced cross-ventilation in a gable roof building. Numerical simulations were carried out using the computational fluid dynamics (CFD) technique based on the steady Reynolds averaged Navier-Stokes equations (RANS) model. Six configurations with asymmetric openings on opposite facades were considered to evaluate the effect of opening positions. Further, for studying the influence of roof pitch on the flow properties, three roof pitches, viz. 3:10, 5:10 and 7.5:10 were considered. It is found that the configuration with a windward opening in the middle and a leeward opening at the bottom (Configuration D) has the highest flow rate. The configuration with a windward opening at the top and a leeward opening at the bottom (Configuration B) has the lowest flow rate. Furthermore, the investigation with different roof pitches reveals that buildings with lower roof pitches are more vulnerable to wind loading due to higher flow separation at the windward eave. The investigation concludes that the opening position and roof pitch significantly influences the indoor airflow characteristics thereby affecting the ventilation performance.

Dynamic energy optimization strategy to provide appropriate thermal comfort and fresh air under occupants’ different activity types

An effective strategy for optimizing indoor air distribution in stratum ventilation heating systems under different types of human activity has been proposed, in order to provide appropriate thermal comfort while exploiting the potential for energy savings. The stratum ventilation was optimized using strategy 1 (the optimization strategy of three ventilation performance indicators based on VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR)), the strategy 2 (the optimization strategy with constraint based on VIKOR) and the strategy 3 (the optimization strategy aimed at energy conservation), respectively. These strategies provide optimal indoor air distribution within a stratum ventilation system that is influenced by various factors (i.e. supply air temperature, supply air vane angle, supply air velocity, metabolic rate, clothing insulation and outdoor air temperature). Firstly, the parameters of the stratum ventilation system are obtained using Computational Fluid Dynamics (CFD) software. In addition, using the simulation results as input variables, predictive models of ventilation performance (i.e., PMV, local mean air age (LMAA) and energy consumption) was developed using Artificial Neural Network (ANN). Finally, by optimizing the proposed ANN based strategy 1, strategy 2 and strategy 3, the ventilation performance is output. The proposed strategy 1 provides a comfortable indoor environment and saves energy, and compared to the strategy 1, the strategy 3 saves more energy while ensuring that thermal comfort meets the requirements. In addition, considering the optimization of clothing insulation while providing appropriate thermal comfort also indirectly saves energy. Moreover, these strategies also work well as the outdoor air temperature changes.

Natural ventilation potential of teaching building complexes with different block shapes and layout patterns

Natural ventilation significantly enhances building energy efficiency and indoor air quality, thereby reducing virus transmission risks, especially crucial in teaching buildings on university campuses frequently occupied by large numbers of students. This study investigates the design impacts of teaching building complexes on indoor and outdoor wind environments, aiming to propose practical design recommendations. Firstly, a typological analysis of teaching building complexes from ten universities in Guangzhou University Town (GUT) was conducted, screening out several archetypes representing diverse design features. Computational fluid dynamics (CFD) simulations were then performed on 16 hypothetical teaching building complexes derived from these archetypes. The wind velocity distributions and area-weighted wind velocities across various hypothetical scenarios were compared and analyzed, allowing for a thorough assessment of the natural ventilation performance associated with different block shapes and layout patterns. The findings reveal that canyons between buildings have a marginal impact on natural ventilation within scenarios characterized by aligned layouts. In contrast, staggered layouts notably enhance natural ventilation, particularly with orthogonal prevailing winds. Furthermore, semi-enclosed courtyard blocks outperform fully enclosed courtyard blocks in natural ventilation, especially when their openings align with prevailing wind directions. Finally, several practical recommendations were summarized for achieving sustainable teaching building design in similar climate regions. Key contributions include demonstrating the significant influence of block shape and layout on ventilation performance and offering novel insights into optimizing building designs for improved natural ventilation.

A comparative study of DQN and D3QN for HVAC system optimization control

Ensuring the optimal performance of Heating, Ventilation, and Air Conditioning (HVAC) systems is paramount for achieving energy efficiency. This paper investigates the application of deep reinforcement learning algorithms in HVAC system control, aiming to identify the most suitable Q-network structure for optimizing HVAC systems and comparing the performance of Deep Q-learning (DQN) and Double Dueling Deep Q-learning (D3QN) algorithms. Initially, this paper evaluates and analyses existing literature to perform a normalization treatment on the state space. Through systematic simulation and rigorous data analysis, the impact of the Q-network structure on the efficacy of the DQN and D3QN algorithms is evaluated, resulting in the proposal of specific values for the Q-network structures within these two algorithms. Subsequently, comparisons are drawn on the optimization effectiveness, stability and reliability of these algorithms across diverse engineering projects. Results highlight the superiority of the D3QN algorithm over the DQN algorithm regarding both optimization effectiveness and stability across all evaluated projects. The proposed efficient Q-network structure comprises two hidden layers, with 64 and 12 neurons respectively in each layer. The findings of this paper are crucial in providing insights for HVAC systems control optimization using reinforcement learning and pave the way for advanced research and applications in the future.

“Knowledge, attitude and reporting practices of ventilator-related errors among nursing professionals"

BackgroundVentilator-related errors (VREs) pose a critical concern for patient safety, necessitating a thorough understanding and mitigation strategies within healthcare settings. This study delves into the prevalence of VREs, while examining the nurse's knowledge of VREs and their reporting attitudes, and practices. Study designCross sectional analytical study. MethodsA cross-sectional study was conducted on 129 nurses working in the Intensive Care Unit (ICU) of a major tertiary care hospital located in the southern part of India. The study involved the administration of a Knowledge, Attitude, and Practice (KAP) survey questionnaire. ResultsThe findings demonstrate a deficiency in the comprehension of VREs among ICU nurses, which subsequently affects their attitudes and reporting practices. Only a small percentage of nurses possess good knowledge (13.2 %), attitude (7 %), and reporting practices (5.4 %). Many nurses identified issues with ventilator performance, including component failure (17 %), design issues (14 %), and alarm problems (14 %). They also reported battery-related problems (9 %), lack of awareness of the instruction manual (7 %), software challenges (6 %), and wear and tear (6 %). A significant association between VRE knowledge and staff experience (p < 0.05) and attitude (P < 0.001) was found. Reporting practices are influenced by staff attitudes (moderate, P < 0.001; good, P < 0.001). ConclusionThis study highlights the significant impact of VRE on patient safety, emphasizing the urgent need for comprehensive understanding and effective preventative measures in healthcare settings.