Ventilation Design Of Buildings Research Articles

Effectiveness of enhanced roof ventilation unit (ERU) based on venturi cap in different wind environments and new evaluation models: A numerical study

Reasonable building ventilation design can effectively improve indoor thermal comfort and reduce energy consumption. Therefore, an enhanced roof ventilation unit (ERU) was developed for this study, and its performance and influence law under various wind speeds and directions were explored through numerical simulation. Additionally, a new evaluation method for ERU was proposed through data fitting, and applicability was verified for different climate zones in China. The results showed that: (1) With a maximum difference of 3.11 °C, the ERU performed best in the N direction and poorest in the SW direction for indoor temperature. Furthermore, the impact of wind directions was more evident than wind speeds. (2) The wind speed affected the volume flow rate significantly in the NE direction (7.77 m3/s) and insignificantly not in the SE direction (0.32 m3/s). Nevertheless, the performance was the opposite in the NE and SE directions when the wind speed increased from 0.5 m/s (3) The air age performed best in the NE and worst in the SE directions. As wind speeds surpassed 2.0 m/s, the air age variation steadily stabilized in various wind directions. (4) The fitted equation for indoor temperature has applicability in typical cities in five climate zones, and the fitted equation for volume flow rate is applicable in four climate zones except the hot summer and warm winter zone. The study results can provide references for the ERU to improve indoor thermal ventilation, contributing to sustainable building energy efficiency.

Effect of outdoor wind on the hybrid natural ventilation performance of monitor roofs

The monitor roof of a building has a raised structure running along the gable ridge, with its smaller roof parallel to the lower main roof. As a common building ventilation design, monitor roofs are expected to induce indoor airflow through thermal buoyancy and/or wind; however, studies on the design details and the induced natural ventilation performance are limited. In this study, how outdoor wind affects the efficiency of induced hybrid natural ventilation of monitor roofs was analyzed through computational fluid dynamics (CFD). Based on engineering practice and weather conditions, the Grashof number (Gr) was 2.11x1011-5.67x1011, and the Reynolds number (Re) was 2.5x105-1.7x106. The results indicated that for a larger monitor roof (width = 3 m, height = 1.2 m), the presence of outdoor wind combined with thermal buoyancy increased the ventilation rate to 1.5–3.5 times that found when only buoyancy was present. For a smaller monitor roof (width = 1.2 m, height = 0.3 m), Gr/Re2 = 0.45–3.2 was the transition range over which the presence of outdoor wind decreased the ventilation rate below that found when only buoyancy was present. Therefore, attention should be given to this disadvantage in ventilation design.

Application of Visual Recognition Based on BP Neural Network in Architectural Design Optimization.

In order to establish the mapping relationship between architectural design parameters and building performance and optimize architectural design parameters, an architectural design optimization method based on BP neural network is proposed. The selected main design parameters of building ventilation include spacing coefficient, air outlet area, and height from the bottom of the window sill to the ground. Take the comprehensive performance of building ventilation design as the main optimization objective to optimize the building design. First, nine groups of samples of building optimization design are obtained through uniform experimental design. Then, based on the architectural design sample data obtained by BP neural network training, the mapping relationship between architectural design parameters and building performance is established, and based on this mapping, the optimal design parameters of the building are calculated. The research results have a certain reference value for architectural design optimization.

Prediction of exhaled carbon dioxide concentration using a computer-simulated person that included alveolar gas exchange.

Accurate prediction of inhaled CO2 concentration and alveolar gas exchange efficiency would improve the prediction of CO2 concentrations around the human body, which is essential for advanced ventilation design in buildings. We therefore, developed a computer-simulated person (CSP) that included a computational fluid dynamics approach. The CSP simulates metabolic heat production at the skin surface and carbon dioxide (CO2 ) gas exchange at the alveoli during the transient breathing cycle. This makes it possible to predict the CO2 distribution around the human body. The numerical model of the CO2 gas exchange mechanism includes both the upper and lower airways and makes it possible to calculate the alveolar CO2 partial pressure; this improves the prediction accuracy. We used the CSP to predict emission rates of metabolically generated CO2 exhaled by a person and assumed that the tidal volume will be unconsciously reduced as a result of exposure to poor indoor air quality. A reduction in tidal volume resulted in a decrease in CO2 emission rates of the same magnitude as was observed in our published experimental data. We also observed that the predicted inhaled CO2 concentration depended on the flow pattern around the human body, as would be expected.

Impact of shading louvers on wind-driven single-sided ventilation in a multi-storey building

As a passive building energy-saving technology, shading systems are usually used to reduce the solar radiation into the unit and reduce the energy consumption of air conditioning system. For multi-storey buildings, shading devices can not only change the indoor thermal environment, but also change the indoor wind environment and air quality because their impact on airflow patterns of natural ventilation. In this paper, the numerical simulation method was used to investigate external shading louvers on the single-sided ventilation performance and indoor air quality of units at different positions in a multi-storey building. Three approaching airflow directions and three rotation angles of louvers were considered and analysed. The results show that the evaluation of ventilation performance of shading louvers in multi-storey buildings is important for shaded buildings, which provide a new perspective for the geometry design of shading louvers and ventilation design of buildings.

Study on the Influence and Optimization of the Venturi Effect on the Natural Ventilation of Buildings in the Xichang Area

Natural ventilation is a way to reduce the energy consumption of building operations and improve the indoor living environment comfort. The venturi cap is designed with a roof, grille and wind deflector to intensify the natural ventilation of buildings. The structural parameters of the venturi cap were designed using an orthogonal design. Fluid analysis software was used for numerical simulation, and variance analysis was used to study the importance of seven influence factors: the width of the roof opening, the roof slope, the height of the wind deflector, the horizontal width of the wind deflector, the angle of the wind deflector, the angle of the grille, and the spacing of the grille slices. The results show that the most significant influencing factor is the width of the roof opening, while significant influence factors include the angle of the grille and the horizontal width of the wind deflector. Additionally, the optimum parameter combination for ventilation performance at the research level was put forward, with the proposed combination achieving a volume flow rate of 5.507 m3/s. The average temperature of the horizontal plane at a height of 1.2 m above the ground was 3.002 K lower than that without a venturi cap, which provides a reference for the optimization of indoor ventilation design in buildings in the Xichang area.

Carbon Dioxide Footprint and Its Impacts: A Case of Academic Buildings

Carbon emissions have been considered a major reason behind climate change and global warming. Various studies report that rapid urbanization and the changing demands of 21st century life have resulted in higher carbon emissions. This study aims to examine the carbon footprints in an academic building to observe the carbon dioxide (CO2) levels at crucial landmarks and offices. A sensor-based automated system was designed and implemented for the collection of CO2 concentrations at selected locations. In the final stage, a CO2 footprint map was generated to highlight the vulnerable areas of CO2 in the academic building. It was concluded that offices have higher CO2 concentrations at both intervals (morning and afternoon), followed by the laboratory, corridors, and praying area. The CO2 concentration did not exceed 500 ppm at any location. Thus, all locations other than offices had normal CO2 concentration levels. Similarly, the humidity level was also satisfactory. The average humidity level was below 50%, which is below the permissible value of 65%. The recommended range for temperature values as per ASHRAE standards is 22.5 °C to 25.5 °C, except for prayer places. It was concluded that the selected academic institute is providing a good environment to the users of the building, but that may change once the academic institute becomes fully functional after COVID-19. This study assists the stakeholders in making guidelines and necessary actions to reduce CO2 concentration in academic buildings, as it is expected to rise once the human load increases in the next academic year. The suggested approach can be used in any other country and the results will vary based on the building type, building energy type, and building ventilation design.

Study on Natural Ventilation Potential of Ordinary Office Buildings in Guangzhou Based on Architectural Factors

As a traditional architectural design technology, natural ventilation has the functions of improving thermal comfort, indoor air quality and energy saving, which is in line with the architectural development concept of green and healthy buildings.Guangzhou is located in the hot-humid area of Lingnan, where is rich in wind resources and attaches great importance to the natural ventilation of buildings. Natural ventilation potential (NVP) are evaluation indexes that can effectively assist and optimize the natural ventilation design of buildings. With abundant relevant studies at home and abroad, various NVP evaluation indexes and calculation methods have been proposed, and strategies for natural ventilation design of buildings in different regions have also been given. Based on the parametric building performance simulation platform, this paper introduces s new NVP evaluation method to carry out parametric simulation research on the ordinary office buildings suitable for natural ventilation in Guangzhou. The results showed that the main factors that limit the NVP of ordinary office buildings in Guangzhou is condensation in summer, and low building density, building toward southwest, high glazing ratio or cross ventilation will bring about high NVP. Meanwhile there is an optimal value for the thermal resistance of the roof, and the greater the thermal storage coefficient of the main material, the greater the night natural ventilation potential.

Study on attached ventilation based on inclined walls

In practical engineering, inclined building walls are often presented due to their functional and aesthetic needs. A reasonable air distribution design is essential for creating a satisfactory indoor environment in such buildings. In the present study, inclined walls with a variable inclination angle β were used as the research object to explore a novel air supply mode. Visualization experiments and numerical simulations were conducted to investigate the induced airflow, such as the airflow pattern, the airflow characteristics (maximum jet velocity decay and jet spreading rate) and the ventilation effect (vertical air temperature difference, draft rate, air diffusion performance index). The results show that the “air lake” phenomena occurred over the floor, which resembles the displacement ventilation to some extent. The proposed air supply mode has a good ventilation effect and could be applied to building spaces with inclined walls. The current study can be used as a reference for ventilation design in buildings with inclined walls.

Propagation and entrainment of buoyancy-driven flows in a narrow horizontal space and implications for buoyant contaminant transport under natural ventilation

Contaminant transport induced by buoyancy-driven flows is crucial for proper ventilation design in buildings. Compared to conventional single-zone spaces, considerably less research has been conducted on the dynamics of buoyant contaminated flows in narrow horizontal spaces with large length-to-width ratios. Experiments were performed to explore the characteristics of natural convection produced by a brine source in a narrow horizontal tank immersed in fresh water. The source was located at the center of the tank ceiling; hence, the buoyancy-driven flow consisted of a plume region and a symmetrical horizontal current. A light attenuation technique was used to measure the density distribution and vertical profile of the horizontal velocity of the current. The current density was vertically stratified, but declined very slowly in the horizontal direction. The head of the horizontal current advanced toward the two ends of the tank at a constant velocity that depended only on the source buoyancy flux. The average thickness of the horizontal current was correlated to the tank height and the source Froude number. In our experiments, the interface between the tail of the horizontal current and the fresh water was very stable, and nearly no mass exchange through the interface was observed. However, mixing between the fresh water and brine occurred in both the plume region and the rearward side of the horizontal current head. Both the total entrainment and the proportion of the entrainment occurring in the head were determined. The latter increased with the source Froude number.

Using the central ventilation shaft design within public buildings for natural aeration enhancement

The natural ventilation of buildings can be closely related to building design. The object of this investigation is to conduct computational fluid dynamic (CFD) simulations and field measurements for studying the natural ventilation effectiveness of office space in a common public building with a built-in central ventilation shaft (CVS). The aeration flow behavior was predicted and compared with the measured air velocity and temperature data at 16 monitoring positions over three different floors inside the main building to validate the computer software as well as attain a better understanding of the natural ventilation mechanism associated with the interaction of the wind with the building. CFD simulations were also extended to examine the design impacts of removing the CVS and reducing the cross-sectional area to a half-sized CVS on the building aeration performance in terms of the air exchange rate per hour (ACH) and the adaptive comfort standard (ACS) and predicted mean vote (PMV) results. This CFD simulation procedure can serve as a useful analysis tool to facilitate architects for improving the natural ventilation design of buildings during their decision-making process.

Research on Natural Ventilation Effect Based on Ventilation Network Model - Case Study of an Office Building in Chongqing, China

This paper proposed HVAC engineer should simulate natural ventilation () of building based on the Ventilation Network Model (VNM) and software of loop pipe network hydraulic calculation and analysis of hydraulic conditions (LPNHHC) V1.0 which is developed by Chongqing University. It presents two indexes, which are requirement of ventilation in local building regulation () and thermal comfortable ventilation (), should be used to evaluate the design talent on building natural ventilation. We can say the building ventilation design meet the requirement under the premise of bigger than and simultaneously. Architecture, otherwise, needs to modify the building design according to the comments of HVAC engineer. HVAC engineer should design mechanical ventilation (MV) if natural ventilation really can not meet the requirement after modification. It, at last, shows a case study of office building in Chongqing in order to prove the method proposed in the paper. We conclude that ventilation network model can be used to evaluate the design effect of building natural ventilation.

Energy Saving from Traditional Settlement – A Case Study on Environmental Ideology of Traditional Settlement in Fujian, China

In the contemporary era of low-carbon and emission reduction, the energy-saving researches on the single architecture have become more and more attentive, including several new building materials, equipment and techniques, etc. However, this strategy in the wholly macro level has been neglected, such as the harmony between the settlement and its natural environment, the space site-positioning program and the reasonable distribution of architectural groups, which should be offered a priority before the sole establishment design. 400 years ago in the south Fujian, China, the ancestors had been trying to explore natural resources and dedicated to the sustainable development, from the angle of environmental plan and design. For instance, comb-style settlement distribution with wide front and narrow side, ventilation design in buildings and locally selected materials are qualified to be the representativeness and afford us lessons.

Modeling and validation of a photocatalytic oxidation reactor for indoor environment applications

Modern building ventilation design must take into account the health, safety and comfort of the occupants, as well as energy consumption and the environment. The system needs to protect occupants against chemical contaminants from numerous internal sources—office equipment, furniture, building materials, appliances, as well as intentional release. A promising technology which has great potential in this respect is UV photocatalytic oxidation (UV-PCO). Designing a UV-PCO system for a building requires full understanding of its performance, which strongly depends on the UV intensity field, types and concentration levels of reactants, oxygen and moisture levels, temperature, reflectance of duct surfaces, system configuration, orientation, air stream characteristics like temperature, humidity, air velocity and mixing, just to mention a few. This paper reports the development of a mathematical model for predicting the performance of a honeycomb monolith PCO reactor used in building mechanical ventilation systems. The model is validated by comparing its prediction with experimental data and with the prediction made by an existing model. The influence of several kinetic parameters such as airflow rate, pollutant inlet concentration, light intensity, humidity and catalyst deactivation has been investigated. The developed model can be used as a practical tool to simulate and optimize a UV-PCO system for application in building mechanical ventilation system.

Multi-zone modeling of probable SARS virus transmission by airflow between flats in Block E, Amoy Gardens

More than 300 residents of a private high-rise housing estate were infected with severe acute respiratory syndrome within a short period during the 2003 epidemic in Hong Kong. The outbreak occurred after the identified index patient visited a flat on a middle floor in Block E of the Amoy Gardens estate on two nights. Approximately 45% of the subsequently infected people resided in Block E, while the other 55% of infected cases mainly resided in six other blocks close to Block E. The distribution of the infected flats in Block E conformed to a non-uniform spatial pattern. Probable environmental causes for airborne transmission associated with the air movements between flats in Block E are identified. The well-established multi-zone airflow modeling method was used to analyze the virus-laden bio-aerosol dispersion between flats through door and window leakage areas in Block E under six different scenarios. The distribution of infection risk in Block E matched with the virus concentrations in flats predicted with the use of multi-zone modeling. Our study shows the importance of ventilation design in high-rise residential apartments. The present study on the Amoy Gardens outbreak presented a scenario in which crowded living spaces might lead to infection disasters. There is a need to improve the current sanitary drainage design and maintenance standards to avoid any leakage of foul gas into the indoor environments. Our study revealed the need for a review of indoor air quality and ventilation design in buildings including offices, homes and hotels. The study has implications to public health in, for example, the control of other airborne respiratory infectious diseases such as influenza, and in bio-terror safety in buildings.

Buoyancy-driven ventilation between two chambers

A model of single-room displacement ventilation is extended to a space consisting of two chambers of equal height connected by two openings. Individually, both chambers have displacement ventilation in this geometrical arrangement, but the space itself is not connected to the outside. Thus we are considering ventilation of two chambers in the interior of a building, such as an office connected to an internal atrium. Theoretical analysis and experimental results are presented in this paper. The experiments use salt solutions to simulate thermal forcing in buildings and the theoretical analysis is based on plume theory. The two chambers have a time-dependent interaction resulting from changing stratification in the two chambers. We concentrate here on a small chamber with an internal heat source connected to a large unheated chamber, and show that the time variation is determined by the size of the larger chamber. We discuss the implications of these results for building ventilation design and control.

Effect of building ventilation design on environment and performance of turkeys

Summary Environmental variables in 10 commercial turkey confinement buildings, representing 2 natural ventilation designs, were measured during summer and the following winter. Sliding doors spaced at intervals along the walls of 5 of the buildings provided about 35% opening, and continuous wall curtains provided 60 to 80% opening in the other 5 buildings. Environmental variables assessed included airspeed; temperature; relative humidity; gases; particle number, size, and mass per cubic meter of air; and colonies of bacteria, yeasts, and other fungi per cubic meter of air. Colonies of yeasts and other fungi were quantitated in feed and litter. For most of the variables evaluated, significant differences were not attributable to building ventilation design; however, in winter, the total mass of particulate matter per cubic meter of air was higher in the curtain-type houses, compared with sliding door-type houses. Ammonia concentration in the air of sliding door-type houses progressively increased during summer and winter sampling periods. A significant effect of building ventilation design on turkey performance was not detected when using mortality, average daily gain, feed conversion, condemnations at slaughter, or average individual bird weight as measures of production.