Effect Of Natural Ventilation Research Articles

The effect of natural ventilation through roof vents following hydrogen leaks in confined spaces

Hydrogen has a high diffusion rate and a wide range of combustion, making it essential to take safety precautions against leakage during storage. We investigate the change in hydrogen concentration in confined spaces due to hydrogen leakage through experimental and numerical methods assuming the worst-case scenario. The vent area consists of 12 %, 24 %, and 36 % of the floor area and is installed in the ceiling of the concrete enclosure. We confirm that the improvement of ventilation performance is insignificant just by increasing the ventilation area above a certain standard during emergency ventilation. Moreover, the improvement of ventilation performance by forced ventilation is more effective as the natural ventilation area is smaller. Still, the effect decreases as the natural ventilation area becomes larger. In conclusion, we confirm that ventilation efficiency is determined by the natural ventilation area rather than forced ventilation.

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

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

Effect of Natural Ventilation on Thermal Performance of Different Residential Building Forms in the Hot-dry Climate of Jordan

This work presents a simulation study on the impact of natural ventilation on the thermal performance and thermal comfort of residential buildings of different forms in the hot-dry climate of Amman, the capital of Jordan. Three existing triple-storey residential buildings with different forms, i.e., rectangular, L-shape, and U-shape, are taken as case studies. Models with similar construction and dimensions of the buildings under investigation are designed using the OpenStudio plugin SketchUp software. Two rooms within these buildings have been considered for simulation with the aid of the EnergyPlus simulator for two cases: the basic case with no ventilation and the case with ventilation. The thermal parameters, including the air temperature, relative humidity, air speed, and mean radiant temperature of both rooms, have been extracted from the simulation. The thermal performance of these buildings is analyzed based on the indoor air temperature and mean radiant temperature, while the thermal performance is investigated via the ASHRAE-55 adaptive model. The results show that the rectangular-shaped building has the best thermal performance in unventilated conditions for the middle room on the middle floor (Room 1). In contrast, the U-shape shows better results for the west-northern room on the same floor (Room 2). On the other hand, introducing natural ventilation to the buildings reduces the indoor temperature and, subsequently, enhances the thermal performance where the buildings transform to be within the comfort zone most of the time, according to the ASHRAE-55 adaptive model. Generally, rectangular and U-shaped buildings show comparable thermal performance, while L-shaped buildings have relatively the worst performance.

The Effect of Courtyard Geometry on Airflow Regimes for Ventilation in Tropical Nigerian Environment

Effective natural ventilation is subject to the ambient wind flow, as well as the conditions of the micro-climate and the geometry of the built structures in the environment. Architects and designers adopt the courtyard concepts for designs in hot tropical climates owing to its unique geometrical characteristics that enable the improvement of airflow required for natural ventilation. This paper presents a review of the airflow regimes within an urban settlement as well as flow regions cultivated when winds interface with courtyard buildings. The impacts of these winds are further studied against different courtyard configurations using schematic analysis based on the H/W ratios, to predict the natural ventilation potentials of various courtyard building types.

Indoor environmental quality trade-offs due to summertime natural ventilation in London care homes

We evaluate current and future summertime temperature and indoor air quality (IAQ) in two London care homes, occupied by seniors. We further examine the effect of natural ventilation, aiming to identify strategies that can maintain temperature, CO2 and key pollutants (PM2.5, NO2) within acceptable ranges. Data come from simulations in DesignBuilder. Results show a higher risk of overheating in the newer care home, with 85% of hourly outputs exceeding 26°C. In addition, bedrooms are much warmer than lounges in both homes, with averages expected to reach 32-35°C by 2050. In terms of IAQ, 65% of PM2.5 and NO2 hourly outputs are within range; however, without any ventilation, the high CO2 levels are expected to rise by 70-130ppm in 2050, especially in bedrooms of the newer home. Results further indicate that natural ventilation can substantially reduce temperature and CO2, but at the same time it may increase PM2.5 and NO2 coming from outdoors. Yet, these trade-offs can be reduced through a careful ventilation strategy that considers building-specific characteristics, as well as time of day and duration. Findings suggest a need to focus on the interdependencies among indoor environmental quality outputs and highlight the value of inexpensive and sustainable passive ventilation.

Examining the Risk of Summertime Overheating in UK Social Housing Dwellings Retrofitted with Heat Pumps

The UK government has announced its ten-point plan to annually install 600,000 low-carbon heat pumps by 2028. However, there is a lack of evidence showing potential overheating risk in dwellings retrofitted with heat pumps. This paper examines the prevalence and magnitude of summertime overheating across 24 naturally ventilated social housing dwellings retrofitted with ground source heat pumps (GSHPs). The dwellings are located in a socially deprived area in Oxford (UK). The empirical study included longitudinal monitoring of indoor temperatures in the living rooms and bedrooms during the non-heating seasons of 2021 and 2022 (May–September), which included a record-breaking heatwave in July 2022. Indoor temperature and CO2 levels in bedrooms were monitored across a subset of six dwellings alongside the monitoring of window opening state in three bedrooms to understand the effect of natural ventilation in removing excess heat. About 136 thermal comfort surveys were conducted to ascertain the subjective responses of residents. Overheating risk assessment was carried out using CIBSE static and adaptive methods, which revealed that summertime overheating was prevalent across half of the dwellings in the non-heating season of 2022, as compared to 17% overheated dwellings in 2021. Bungalows with upgraded cavity wall insulation and top floor flats facing south and south-west had a propensity to overheat. The variation in indoor temperature and CO2 levels across a small sample also indicated the relationship between overheating and residents’ behaviour. Given that the majority of the dwellings were occupied by retired elderly people with low incomes who are vulnerable to heat and cannot afford active forms of cooling, it is vital to deploy passive design measures, such as appropriate shading devices that are suitable for a heating-dominated climate and enhanced ventilation, as part of home energy retrofits. Implementing reversible heat pumps coupled with solar PVs can provide cooling during heatwaves while delivering low-carbon heat in the winter.

Effect of open windows on airborne contamination and its topographical distribution in the dental operatory.

Aerosols produced by dental handpieces represent a permanent risk of disease transmission in the dental environment. The current study evaluated the effects of natural ventilation (open windows) on Streptococcus mutans airborne contamination by dental handpieces in simulated clinical conditions. A dental phantom was placed on a dental chair at a standard university dental clinic operatory. An S. mutans suspension was infused into the phantom's mouth while an operator performed standardized dental procedures using low (contra-angle) and high speed (turbine) dental handpieces or an ultrasonic scaler, with windows open or closed. Selective medium Petri dishes were placed in 18 sites of the operatory environment to evaluate contamination topographically. Sites were clustered as: wall, floor, ceiling, dental chair, and cabinet. Contamination was expressed as log10 CFU/cm2 . A linear mixed model analysis was used, nesting the sites within each ventilation and handpiece combination. Open windows significantly reduced contamination. The high-speed handpiece provided the highest contamination, followed by the ultrasonic scaler and the low-speed handpiece. Contamination values were much smaller at the ceiling, and much larger at the chair. Opening windows produced more homogeneous contamination of the operatory compared to closed windows. Natural ventilation during dental procedures decreases contamination and affects its topographical distribution.

Simulation Study on Natural Ventilation Performance in a Low-Carbon Large-Space Public Building in Hot-Summer and Cold-Winter Region of China

Recently, climate governance has entered a new phase of accelerating decarbonization. In order to achieve low-carbon buildings, natural ventilation has been widely used as it requires no fan power. However, there are great challenges for achieving effective natural ventilation in large-space public buildings especially in areas characterized by hot-summer and cold-winter climatic regions, due to empirically unsuitable ambient temperatures and theoretically complex joint effect of wind pressure and thermal buoyancy. Therefore, this numerical study was conducted on the performance of a natural ventilation strategy in a large-space public building in a hot-summer and cold-winter region by using computational fluid dynamics (CFD) methods. Simulations were performed by applying FLUENT software for obtaining airflow distributions within and around a typical low-carbon public building. The temperature distribution in the atrium of the building was simulated particularly for analyzing the natural ventilation performance in a large-space area. Results demonstrated that thermal pressure was dominant for the large-space building in the case study. The average indoor airflow velocities on different floors ranged from 0.43 m/s to 0.47 m/s on the windward side which met indoor ventilation requirements. Most areas of wind velocities could meet ventilation requirements. The natural ventilation performance could be improved by increasing the relative height difference between the air inlets and air outlets. These findings could help provide references and solutions for realizing natural ventilation in low-carbon large-space public buildings in hot-summer and cold-winter regions.

Simulation of photothermal building and thermal comfort analysis of PMV

Nowadays, with the development of technology and the improvement of human economic level, the energy consumption of buildings is gradually increasing. China is very rich in solar energy resources and the development of solar buildings can save a lot of energy by taking advantage of solar energy resources. The Trombe Wall to be studied in this paper are passive solar buildings. Trombe Wall can achieve good indoor natural ventilation and can meet the requirements of human thermal comfort. However, solar energy is unstable and intermittent, which can easily lead to excessive fluctuations in indoor temperature, so the use of suitable phase change or energy storage materials is also a very important measure. In this paper the mathematical model corresponding to Trombe Wall is specifically investigated and simulations are carried out using COMSOL Multiphysics software to verify the thermal characteristics of Trombe Wall at different temperatures in a given room and the natural ventilation effect they achieve. The simulations are followed by a PMV thermal comfort analysis of the room. The analysis is carried out for four scenarios: “Summer - day”, “Summer - night”, “Winter - day” and “Winter - night”, thus enabling the analysis of Trombe Wall at different temperatures.

Effect of Flare Angle and Natural Ventilation on The Aerodynamic Characteristics of a Typical Re-Entry Body At Subsonic and Transonic Mach Numbers

Aerodynamic force and moment measurements were carried out on models of a typical re-entry body, featuring a blunt nose, conical body and flare, to assess the effect of flare angle on the overall aerodynamic characteristics. In one of the configurations, the junction between the cone and the flare was vented out to the base of the model to assess the effect of ventilation on the aerodynamic characteristics. It was expected that the stability characteristics would improve, by virtue of improved contribution from the flare to the normal force of the configuration. However, measurements did not show the expected trends. Instead, there was a remarkable reduction in the axial force with ventilation, by as much as 25% all across the Mach number and angle of attack range. Base pressure measurements indicated that in the low Mach number range pressure rise occured. However, in the high transonic Mach number range, even though the force measurements showed drag reduction, there was no significant rise in base pressure. Ventilation showed delay in transonic drag rise. It is therefore suggested that the overall pressure field is modified by ventilation, which results in drag reduction of the configuration.

Optimization Analysis of Natural Ventilation in University Laboratories Based on CFD Simulation

In recent years, there has been a significant surge in the adoption of natural ventilation for building indoor spaces, garnering widespread attention. However, the research on human comfort optimization strategies closely related to the effect of natural ventilation is still relatively blank. Therefore, we have taken university laboratories as the research object and studied the use of CFD technology to construct numerical models. Based on previous research on the relevant theories of building ventilation and the impact of various air indicators on human comfort, we simulate the indoor airflow organization of buildings, and propose reasonable optimization design strategies based on simulation results and analysis conclusions. Compared to other studies on NV, we propose a completely new indicator, the Average rate of change in air age (ARCA), to assess the rate of improvement in air age. The results show that compared with the wind environment under basic conditions, the optimization strategy proposed by us increases the wind speed area suitable for human beings by about 14.3%, and reduces ARCA by about 53.3% at most.

STUDY RECOMMENDATIONS TO ACHIEVE THERMAL COMFORT IN AN EDUCATIONAL BUILDING

This paper evaluates natural ventilation effectiveness in one fully dependent Air Conditioned-Educational Building in Depok to recommend potential passive cooling approaches toward user thermal comfort. This study involves building surveys to measure the temperature and humidity of three selected classrooms, A, B, and C, with varying configurations and capacities. Airflow simulation using Computational Fluid Dynamics (CFD) is done under two conditions: open and closed doors. A set of parameters, which are room configuration, type of window, and ventilation strategy, are set to evaluate natural ventilation aspects. The site survey indicates that only one classroom with an area of 92 sqm facing to the southside is classified as efficiently warm (Room A). The simulation demonstrates that cross-ventilation only occurs when the door is opened. The parameters indicating shape, dimension, type, and area of natural ventilation matter, show that the building’s natural ventilation is ineffective in providing thermal comfort. This study recommends that the building’s natural ventilation be placed according to the direction of the airflow, adding vertical fin elements, and increasing the openings by more than 5% area from the floor area.

전통주거건축의 평면형태에 따른 여름철 대청마루의 통풍효과에 관한 연구

This study aims to examine the Cross ventilation effect of Daecheongmaru in summer according to the floor plan of Korean traditional housing architecture by region according to the climate characteristics of the Korean Peninsula. This study examines the climate characteristics of the Korean Peninsula and identifies the floor plan of Korean traditional housing architecture that appears accordingly. In particular, the purpose of Korean traditional housing architecture is to examine the nature-friendly construction techniques and ventilation effects of Korean traditional architecture through natural ventilation by focusing on Daecheongmaru, which is generally highly utilized in summer. The following conclusions were drawn. First, the plane form of traditional housing architecture is judged to have an overall advantageous plane form in the summer natural ventilation effect. Second, the natural ventilation effect of Daecheongmaru according to the plane shape of traditional housing architecture appeared in the order of ㄱ-shape, ㅡ-shape, ㅁ-shape, and ㄷ-shape. Third, the Daecheongmaru of traditional housing architecture is judged to be suitable for its role as a central space for summer life due to the formation of an open space in the front and back.

The effect of natural ventilation on airborne transmission of the COVID-19 virus spread by sneezing in the classroom

Since school classrooms are of vital importance due to their impact on public health in COVID-19 and similar epidemics, it is imperative to develop new ventilation strategies to reduce the risk of transmission of the virus in the classroom. To be able to develop new ventilation strategies, the effect of local flow behaviors in the classroom on the airborne transmission of the virus under the most dramatic conditions must first be determined. In this study, the effect of natural ventilation on the airborne transmission of COVID-19-like viruses in the classroom in the case of sneezing by two infected students in a reference secondary school classroom was investigated in five scenarios. Firstly, experimental measurements were carried out in the reference class to validate the computational fluid dynamics (CFD) simulation results and determine the boundary conditions. Next, the effects of local flow behaviors on the airborne transmission of the virus were evaluated for five scenarios using the Eulerian-Lagrange method, a discrete phase model, and a temporary three-dimensional CFD model. In all scenarios, immediately after sneezing, between 57 and 60.2 % of the droplets containing the virus, mostly large and medium-sized (150 μm < d < 1000 μm) settled on the infected student's desk, while small droplets continued to move in the flow field. In addition, it was determined that the effect of natural ventilation in the classroom on the travel of virus droplets in the case of Redh < 8.04 × 104 (Reynolds number, Redh=Udh/νu, dh and are fluid velocity, hydraulic diameters of the door and window sections of the class and kinematic viscosity, respectively) was negligible.

Effects of natural ventilation on indoor thermal comfort in a residential house constructed with reinforced concrete wall

This study aims to investigate the effect of natural ventilation on the thermal performance of a double-story end-lot unit residential house constructed with reinforced concrete walls and structure in Kluang, Johor. Field measurement was conducted in the master bedroom of the house. Five ventilation cases were investigated which are night ventilation (case 1), no ventilation (case 2), day ventilation (case 3), day ventilation with fan (case 4), and night ventilation with fan (case 5). The measured data were indoor air temperature, outdoor air temperature, indoor relative humidity, outdoor relative humidity, and globe temperature. Then, the thermal comfort assessment was conducted based on the adaptive thermal comfort equation for hot-humid climate for all cases. The results show that the mean indoor temperature for all cases is in the range of 29°C to 31.5°C which indicates a high indoor air temperature. Furthermore, the analysis of air temperature difference between outdoor and indoor (out-in) for different natural ventilation modes showed that the indoor thermal conditions of the master bedroom were not significantly different when compared between cases. In the thermal comfort assessment, the night ventilation case (case 1) provided the most comfortable hours during the measurement with a range of 11 to 35.4 %, thanks to the lower outdoor climate conditions at night compared to the other cases. Overall, in this study, the effect of natural ventilation modes on the indoor thermal condition of a master bedroom in a residential house with concrete walls and structures was found not significantly different in the performance of air temperature reduction and comfort hour improvement when compared between cases.

The Ventilation Capacity of Earthen Vernacular Buildings With Timber Projections (Sachnisi) in Dense Urban Canyons – Findings From a Field Study in the Mediterranean

Vernacular architecture employs numerous elements for enhancing natural ventilation, especially in the Mediterranean climate. However, the cooling effectiveness of natural ventilation also relies on occupant behaviour and is highly determined by urban scale attributes. Still, airflow in real, inhomogeneous historic urban settings is rarely integrated in the thermal comfort studies of historic buildings. In this study, a multi-scale approach is adopted in order to assess the role of ventilation in establishing thermal comfort in earthen buildings, in real field conditions. This is achieved by addressing field monitoring of air velocity, temperature and relative humidity in: a) a dense (packing density λp=0.60) and inhomogeneous historic neighbourhood in Nicosia, Cyprus (measurement at a reference height); b) the street-canyon (measured at the mid-height of a narrow canyon with aspect ratio 2); and c) the interior of a typical adobe building with semi-open, pass-through spaces (portico) and closed timber projections with multiple openings, called sachnisi. Building ventilation was addressed as a function of in-street and rooftop airflow. Indoor thermal comfort was assessed in the case of specific ventilation patterns, comparing three adaptive comfort models. The results highlight the complexity of airflow in real inhomogeneous urban canopies and demonstrate that air velocity level in the street canyon is approximately one third of the reference free-stream wind velocity, while indoor air velocity remains at minimum levels. The study also reveals the contribution of night-time ventilation in cooling. Finally, spatial differentials of indoor environmental conditions in the portico were recorded for the first time, demonstrating the role of the sachnisi as a wind-capture element.

Climate-responsive opportunities and challenges in urban vernacular heritage.

In response to today’s contemporary challenge regarding how to tackle the effects of climate change in heritage environments, natural ventilation arises as a compatible, low-cost and environmentally friendly passive cooling strategy for the Mediterranean climate. However, an identified research gap concerns the lack of studies addressing data from both the urban and building scales. An innovative, multi-scale approach is introduced in this research, through the study of airflow on the neighbourhood, street canyon and building scales, which is then evaluated using field measurements. The effect of urban density and street-canyon geometry on indoor thermal comfort is discussed in the case of adobe buildings with pass-through spaces (portico), and timber projections with multiple openings (sahnisi). The originality of the presented research lies in the adopted multi-scale methodology. On the district level of study, analytical tools and urban-scale considerations in the development of vernacular buildings are discussed through the lens of environmental performance. Building ventilation is addressed as a function of in-street and rooftop airflow, demonstrating the airflow gradient across the scales under study. Furthermore, the impact of various window operation patterns is quantified, given the variability of the background wind and street geometry. The results indicate best practices for enhancing the cooling effect of natural ventilation, highlighting the role of occupant behaviour and night-time ventilation. Finally, key directions regarding conservation practices in urban contexts are discussed, bringing energy performance and comfort into cultural heritage studies.

Influence of winter natural ventilation on thermal environment of university dormitories under central heating mode in severe cold regions of China

The indoor thermal environment impacts people’s health, while it can be adjusted by natural ventilation. However, studies on the effects of winter natural ventilation on the thermal environment in severe cold regions are minimal. Through field measurements in university dormitories in winter in Shenyang, China, this study explored, under the central heating mode, the thermal environment differences in different orientations of the dormitory and its different indoor positions under natural ventilation and the influence of window opening area and duration on the thermal environment. The results show that under winter natural ventilation, the air temperature, mean radiation temperature, and adaptive predicted mean vote (APMV) of dormitories facing different orientations were mainly affected by the direct solar radiation reception. When the ventilation duration reached 15mins, with the ratio of window opening area to a ground area of 0.05, 0.11, and 0.16, the APMV decreased by about 0.35, 0.5, and 1, respectively.

Numerical Study on Coupled Smoke Control Using Longitudinal Ventilation and Naturally Ventilated Shafts during Fires in a Road Tunnel

Longitudinal ventilation and smoke extraction by shaft are common smoke control methods in road tunnel fires. Tunnels often adopt one of these methods in practical engineering. However, it may have a better effect to adopt the method of mixing the two smoke exhaust methods together, which has not been revealed in the previous literature. Hence, the coupled effects of longitudinal ventilation and natural ventilation with shafts on the smoke control in tunnel fires were studied in this work. Numerical simulation was carried out considering different longitudinal ventilation velocities (0–4 m/s) and 4 kinds of typical shaft arrangements (shaft lengths range of 3–12 m, shaft intervals range of 27–60 m). The smoke spread length and smoke exhaust efficiency were analyzed systematically. Results show that (1) with the increase in longitudinal ventilation velocity, the total smoke spread length firstly decreases (V &lt; 1 m/s) and then keeps almost constant (1 m/s &lt; V &lt; 2 m/s), finally increasing significantly (V &gt; 2 m/s). (2) The length of the dangerous area (over 60 °C) at human height is basically 0 for all cases (except for Scenario 4 of shaft arrangement) when the longitudinal ventilation velocity is less than 2 m/s. (3) The CO smoke flow rate through the shaft is relatively high when the longitudinal ventilation velocity is within the range of 1–2 m/s for 4 kinds of shaft arrangement scenarios. Factors such as smoke spread and smoke exhausted through the shaft are comprehensively considered to judge smoke exhaust performance. The following conclusions can be drawn: when the ventilation velocity ranges from 1–2 m/s, it has a positive impact on the smoke control in tunnel fires with natural ventilation with shafts. When the ventilation velocity exceeds 2 m/s, the total smoke spread length and the length of the danger area increase, and the smoke stratification becomes worse, which brings inconvenience to rescue work. The results can provide reference for the design of fire protection in tunnels.

Simulation Study on Geometric Parameters Influencing the Flow Coefficient of Perforated Plate

Natural ventilation is one of the vital means for passive energy-efficient design in green buildings. As a widely used building façade, the perforated plate is mostly utilized for appearance decoration, noise absorption, and sun shading, but its impact on the natural ventilation effect has rarely been paid attention to. In this study, the influence of the perforation rate, the perforation size, and the perforation shape on the flow coefficient of the perforated plate were simulated using the commercial CFD software Fluent, and the correlation between the flow coefficient and these geometric parameters was then regressed. The results show that the flow coefficient of perforated plate increases with the increase in perforation rate, which is slightly greater than that of ordinary building openings, and the corresponding flow coefficients of different holes rank as circle &gt; square &gt; triangle under the same conditions. The flow coefficient increases with the increase in the perforation size, and this effect is greater when the size is small. In addition, the flow coefficient is less affected by the size of round holes compared to triangular and square holes. The regression model indicates that both the perforation rate and the perforation size have a considerable positive influence on the flow coefficient, while the square and triangle holes have a negative influence on the flow coefficient compared with the circular hole. Moreover, the geometric parameters of perforated plates that have the greatest influence on flow coefficient are perforation rate, perforation shape, and size, in descending order.