Ventilation Design Research Articles

Influence of natural ventilation design on the dispersion of pathogen-laden droplets in a coach bus

Natural ventilation is an energy-efficient design approach to reduce infection risk (IR), but its optimized design in a coach bus environment is less studied. Based on a COVID-19 outbreak in a bus in Hunan, China, the indoor-outdoor coupled CFD modeling approach is adopted to comprehensively explore how optimized bus natural ventilation (e.g., opening/closing status of front/middle/rear windows (FW/MW/RW)) and ceiling wind catcher (WCH) affect the dispersion of pathogen-laden droplets (tracer gas, 5 μm, 50 μm) and IR. Other key influential factors including bus speed, infector's location, and ambient temperature (Tref) are also considered. Buses have unique natural ventilation airflow patterns: from bus rear to front, and air change rate per hour (ACH) increases linearly with bus speed. When driving at 60 km/h, ACH is only 6.14 h−1 and intake fractions of tracer gas (IFg) and 5 μm droplets (IFd) are up to 3372 ppm and 1394 ppm with ventilation through leakages on skylights and no windows open. When FW and RW are both open, ACH increases by 43.5 times to 267.50 h−1, and IFg and IFd drop rapidly by 1–2 orders of magnitude compared to when no windows are open. Utilizing a wind catcher and opening front windows significantly increases ACH (up to 8.8 times) and reduces IF (5–30 times) compared to only opening front windows. When the infector locates at the bus front with FW open, IFg and IFd of all passengers are <10 ppm. More droplets suspend and further spread in a higher Tref environment. It is recommended to open two pairs of windows or open front windows and utilize the wind catcher to reduce IR in coach buses.

Study on temperature field and influencing factors of the high geothermal tunnel with extra-long one-end construction ventilation

The increasing number of deep-buried high geothermal tunnels with extra-long one-end ventilation distance makes it critical to develop an accurate and efficient computational model to predict the ambient temperature of such tunnels. A numerical model capable of quickly calculating the longitudinal temperature field of the tunnel construction environment has been established by combining the finite difference method and finite element software. The model, which accounts for the initial ground temperature distribution as well as the heat exchanges at the working face, agrees well with the field monitoring results of the Dechang Tunnel. The research results show that the air temperature during tunnel construction varies as follows: stable heating section in the duct → rapid heating section near the working face → slow heating section of the return air → temperature drop section of the return air. The temperature of the characteristic sections (duct outlet, working face, and tunnel maximum temperature section) all show a quadratic function upward with construction length (L). These also show an exponential trend with ventilation volume (v), insulated duct thickness (t1), and tunnel insulation layer thickness (t2). To achieve a temperature change slope greater than 0.5 in the working face of the Dechang tunnel, the recommended criteria include a ventilation volume below 110 m3/s, an insulated duct thickness below 3 cm, and a tunnel insulation layer thickness below 7 cm. The research results can provide a basis for ventilation and heat insulation design of the extra-long high geothermal tunnel.

An efficient design method of indoor ventilation parameters for high-speed trains using improved proper orthogonal decomposition reconstruction

The ventilation parameters inside a compartment of a high-speed train (HST) are of great significance to the thermal comfort and air quality around passengers. Additionally, parameter design relying on traditional numerical simulations takes considerable time and resources. This study proposed an improved inverse design approach based on proper orthogonal decomposition (POD) to the design of supply air parameters of a compartment for an HST; this method was combined with the radial basis function (RBF) model and the orthogonal experimental design (OED) to facilitate the process. The feasibility and accuracy of this improved method applied to ventilation design inside the HST were validated by experimentally verified numerical simulations. Three design parameters (i.e., the temperature of the inlets, the ratio of the upper air supply, and the angle of the upper inlets) and evaluation indexes (i.e., predicted mean vote, draught rate and air age) were taken into consideration, and the sensitivity of the design parameters to the evaluation indexes was analysed by orthogonal cases using range analysis. The proposed POD reconstruction method has a remarkable advantage over traditional numerical simulation methods with respect to the time and efficiency of design and can take approximately 40% less time than the current POD method to obtain numerical simulation samples. Moreover, the reconstructed results by the RBF model were more consistent with the actual simulation data, and the average determination coefficients (R2) of all test cases for all evaluation indexes are more than 0.97.

Application of renewable energy decorative materials in modern architectural design under low-carbon concept

Abstract The construction industry is booming, but construction projects will consume much non-renewable energy and cause environmental pollution. In response to this problem, this article establishes a low-carbon architectural design model and discusses the application of renewable energy decorative materials in modern architectural design in detail. Previous studies have shown that renewable energy decorative materials are widely used in ventilation design, thermal insulation design, interior design and lighting design, and the weights of carbon emissions in the use stage are 20%, 46%, 29% and 33%, respectively. In 2021, the usage weights of renewable energy decorative materials in ventilation design, thermal insulation design, interior design and lighting design will be 70%, 72%, 80% and 70%, respectively, far exceeding the usage of traditional materials.

Simulation Research on Effects of Ambient Pressure on Plug-Holing Phenomenon in Tunnel Fires with a Shaft

This paper studied the effects of ambient pressure on the plug-holing phenomenon in tunnel fires with a shaft by a Fire Dynamics Simulator. The influence of ambient pressures on the smoke movement, temperature distribution, critical Richard number (Ric) and critical shaft height for plug-holing were analyzed in detail. A new prediction formula of smoke flow velocity considering different pressures was modified. A prediction formula of smoke temperature distribution beneath the ceiling under different pressures was developed. As a result, a prediction model of Richard numbers to determine whether the plug-holing occurs was proposed by combining smoke flow velocity and smoke temperature distribution. The critical Richard numbers (Ric) and critical shaft height (hc) increases as the pressure decreases. Outcomes in this study can provide references for the design of a natural ventilation system in tunnel fires at a higher altitude.

Sensitivity and preference of local airflows beneath garments with personalised temperatures and velocities

Microclimate ventilation under garment is one of the effective means to relieve heat stress of human body, while the sensitivity and preference of airflow at different body parts are not thoroughly studied. This study investigates the local airflow sensitivity of five body segments by a psychophysical method, whereby twelve subjects were stimulated by three temperatures of ventilation under garment (Tsk - 5 °C, Tsk, or Tsk + 5 °C, Tsk is the initial local skin temperature); at the front chest, upper back, lower back, front thigh, and back thigh areas. Airflow sensitivity was tested to enhance when the airflow became warmer or cooler than the Tsk, showing that human skin can recognise variations in airflow velocity with a difference threshold of 0.23 ± 0.06 m/s. The front chest was the least sensitive of all three airflow temperatures, while the back thigh was the most sensitive to cool airflow. Twelve subjects then underwent controllable local ventilation at 35 °C, RH 40%. The airflow preference, psychological and physiological responses, and energy consumption were analysed. The preferred airflow temperature was approximately 26 °C (25.7 ± 1.8–25.9 ± 1.4 °C), while the preferred airflow velocity had a large individual variation. The lower back should be primarily ventilated, obtaining comfort enhancement with an energy saving of 30–40% compared to others; the front chest or the upper back should be added for higher cooling demand. This study helps us to understand the characteristics of airflow sensitivity on localised skin and optimises the design of individual ventilation.

中間季の換気行為に着目した都市部の保育施設における換気に関する研究

This paper aims to clarify ventilation issues, and the field survey was conducted during the intermediate season at nursery facilities in Yokohama City. As a result, nursery facilities are classified into three categories according to ventilation behavior of nursery teachers. “Window-ventilation type” tends to have high room temperature and risk of heat stroke. “Mechanical-ventilation type” and “Combined-ventilation type” indicate high CO2 concentrations and have difficulties with ventilation routes and use of ventilation equipment. Based on the estimated ventilation rates, “Mechanical-ventilation type” was found not to meet the ventilation standards and design ventilation rates.

Zero Energy Building Approach in Design of Biohydrogen Research Centre

The utilisation of natural energy not only can reduce energy consumption in buildings but also can lower carbon emissions from the use of fossil fuel energy for building services. It is believed that with appropriate design and a good attitude of building users, the role of renewable energy in reducing carbon emissions will be maximised. This study proposed the implementation of Zero Energy Buildings (ZEB) concept in the initial stage of building design by considering buildings’ form and façade design in relation to daylighting, natural ventilation and thermal design of buildings, and photovoltaic placement to save energy and to produce electrical energy in the designed building. In this study, ZEB Concept is treated as a secondary consideration in producing the architectural design for Biohydrogen Research Centre. The primary design generator is based on the philosophy of chemical bonds form representing biohydrogen chemical bonds. For a successful implementation of the ZEB concept in the Biohydrogen Research Centre design, both active and passive means are utilised in the building design. For passive means, daylighting and natural ventilation strategies were applied. While for active means, photovoltaic panels were employed as the primary electrical energy generation. Energy demand scenarios were predicted and calculated by the amount of energy used for lighting, air conditioning, and other appliances in the building. The total area needed for photovoltaic installation was obtained by balancing the energy demand prediction with the expected energy generation. The resulting design showed a promising outcome where the building is expected to achieve surplus energy with a total of 845,595.5 kWh electricity per year.

Analysis of Palu City’s Readiness Level Assessment Towards Adipura (case study: Siranindi Village)

The utilisation of natural energy not only can reduce energy consumption in buildings but also can lower carbon emissions from the use of fossil fuel energy for building services. It is believed that with appropriate design and a good attitude of building users, the role of renewable energy in reducing carbon emissions will be maximised. This study proposed the implementation of Zero Energy Buildings (ZEB) concept in the initial stage of building design by considering buildings’ form and façade design in relation to daylighting, natural ventilation and thermal design of buildings, and photovoltaic placement to save energy and to produce electrical energy in the designed building. In this study, ZEB Concept is treated as a secondary consideration in producing the architectural design for Biohydrogen Research Centre. The primary design generator is based on the philosophy of chemical bonds form representing biohydrogen chemical bonds. For a successful implementation of the ZEB concept in the Biohydrogen Research Centre design, both active and passive means are utilised in the building design. For passive means, daylighting and natural ventilation strategies were applied. While for active means, photovoltaic panels were employed as the primary electrical energy generation. Energy demand scenarios were predicted and calculated by the amount of energy used for lighting, air conditioning, and other appliances in the building. The total area needed for photovoltaic installation was obtained by balancing the energy demand prediction with the expected energy generation. The resulting design showed a promising outcome where the building is expected to achieve surplus energy with a total of 845,595.5 kWh electricity per year.

Research on the Form of Energy-saving Building under the Influence of Natural Ventilation Technology

With the development of science and technology and the progress of society, humanity is confronting a huge energy crisis. The energy consumption of buildings and the energy consumed to produce that energy have greatly changed the environment in which we live, causing serious energy and environmental consequences. Taking the natural ventilation design method as the main line and the excellent energy-saving building cases as the breakthrough point, this paper focuses on the three dimensions of building groups, building units and building components, and compares and studies the effects of various natural ventilation technologies, the shape of the building. These buildings have strong climate adaptability and climate regulation ability, which can effectively improve and create comfortable indoor microclimates, so that the buildings do not need or reduce the dependence on building equipment, so as to achieve the purpose of reducing building energy consumption.

Enhancing non-domestic Passivhaus auditoria ventilation design for improved indoor environmental quality

Enhancing non-domestic Passivhaus auditoria ventilation design for improved indoor environmental quality

CFD analysis of the air supply rate influence on the aerosol dispersion in a university lecture room

The airborne droplet route has been recognized as the main pathway of infection transmission in indoor environments, drawing the attention to a proper design of Heating, Ventilation and Air Conditioning (HVAC) systems. This is particularly relevant for gathering spaces such as schools and universities, due to the high crowding levels and the long exposure times. Using 3D Computational Fluid Dynamics (CFD) numerical simulations based on a Eulerian-Lagrangian approach and validated against velocity measurements, the present study investigates the distribution over time of airborne droplets (aerosol) emitted in correspondence of the teacher position inside a lecture room, during a 2-h speaking activity (so reproducing a 2-h lesson), as a function of different air supply rates from the HVAC system. As the aim of the paper is to provide useful information for proper design and operation of HVAC systems, the room has been assumed to be empty. Results show that increasing the air supply rate is not always an effective solution to reduce aerosol concentration in correspondence of the positions occupied by the students attending the lesson. In fact, for the specific case under investigation, the aerosol concentration around the classroom seats does not always decrease when increasing the supply rates, even though the overall number of particles in the room decreases. This behaviour is mainly due to the asymmetric disposition of the seats with respect to the diffusers and extraction grilles, and underlines the importance of CFD approaches in investigating the fluid dynamics in indoor environments.

Application of Green Design Concept in the Intelligent System of Interior Art Design under the Information Technology Environment

Based on the information technology environment, this paper studies the application of the green design concept in the interior design intelligent system. First, it introduces the connotation and basic characteristics of the green design concept, and then elaborates on the four perspectives of space layout, decoration materials, furniture selection, and ventilation and lighting. The specific application of green design concept in interior design. After use, it can be recycled and reused, implement the concept of sustainable development, and establish a scientific ecological awareness; ventilation design and natural lighting, as well as a comfortable thermal environment should be fully considered in the interior design process; environmentally friendly materials are used to ensure indoor health It is safe, and the original ecological materials can be used to make the interior more environmentally friendly and artistic.

Evaluation of indoor environmental quality, personal cumulative exposure dose, and aerosol transmission risk levels inside urban buses in Dalian, China.

The transmission of pollutants in buses has an important impact on personal exposure to airborne particles and spread of the COVID-19 epidemic in enclosed spaces. We conducted the following real-time field measurements inside buses: CO2, airborne particle concentration, temperature, and relative humidity data during peak and off-peak hours in spring and autumn. Correlation analysis was adopted to evaluate the dominant factors influencing CO2 and particle mass concentrations in the vehicle. The cumulative personal exposure dose to particulate matter and reproduction number were calculated for passengers on a one-way trip. The results showed the in-cabin CO2 concentrations, with 22.11% and 21.27% of the total time exceeding 1000ppm in spring and autumn respectively. In-cabin PM2.5 mass concentration exceeded 35μm/m3 by 57.35% and 86.42% in spring and autumn, respectively. CO2 concentration and the cumulative number of passengers were approximately linearly correlated in both seasons, with R value up to 0.896. The cumulative number of passengers had the most impact on PM2.5 mass concentration among tested parameters. The cumulative personal exposure dose to PM2.5 during a one-way trip in autumn was up to 43.13μg. The average reproductive number throughout the one-way trip was 0.26; it was 0.57 under the assumed extreme environment. The results of this study provide an important basic theoretical guidance for the optimization of ventilation system design and operation strategies aimed at reducing multi-pollutant integrated health exposure and airborne particle infection (such as SARS-CoV-2) risks.

Pyrolytic characteristics, kinetics, thermodynamics, volatile products and chemical reactions of micron polypropylene infiltrated with kerosene

The pyrolysis of polymers infiltrated with combustible liquids is one common behavior in the fire accidents resulted by the leakage and overflow of combustible liquids over polymers. The present study may provide a theoretical basis and guidance for the prediction of fire development, the selection or design of fire detection and the design of ventilation and fire extinguishing systems. In the present study, the thermal decomposition behaviors, kinetics, thermodynamics, volatiles and chemical reactions of micron polypropylene (typical polymer) infiltrated with kerosene (typical combustible liquid) are investigated. It is concluded that the thermal decomposition process of micron PP with kerosene can be divided into two stages, and all stages can be considered as one-step reaction. As the kerosene content increases, the average and peak reaction rates of the first stage increase, while they decrease for the second stage and the whole process. As the heating rate increases, the average and peak reaction rates of the whole process decrease. In addition, increasing the heating rate or kerosene content may result in better combustion performance compared with that of pure PP. The calculated average activation energy, pre-exponential factor and global reaction model of the second stage can well predict the thermal decomposition behaviors of this stage. Thermodynamic analysis shows that the thermal decomposition of micron PP with kerosene is an endothermic and non-spontaneous reaction. The main volatile products contain olefins, alkynes, alkanes, hydrogen, carbon dioxide, carbon monoxide and aromatic compounds. The possible chemical reactions generating the above-mentioned products are deduced.

Study on emergency ventilation strategies for various fire scenarios in a double-island subway station

The double-island subway station with complex structure and dense crowds brings about serious fire safety issues. Aiming to control fire-induced smoke, numerical simulations were conducted to investigate the emergency ventilation strategies. The numerical model was validated by the reduced-scale model experiments and full-scale experiments. Various ventilation modes were compared under different fire scenarios and platform screen door (PSD) types. The results demonstrated that a reasonable co-work mode of ventilation system was vitally important in preventing smoke dispersion and reducing pollutant concentration. Opening the screen doors was found to be conducive to the joint ventilation in the platform and tunnel under the type of full-height PSD, whereas whether opening the half-height PSD had little influence on ventilation effect. On this basis, the optimal ventilation modes were developed respectively for platform fire, fire inside the carriage and carriage fire, among which the best control measurement for carriage fire was related with the location of the train. Additionally, a reasonable optimization of the ventilation system could further improve the safe environment. This work could provide guidance for emergency response under sudden fire accident, and provide reference for engineer design of ventilation system in the metro stations.

Contribution of temperature measurements to the hydrogeological model in the Snowy 2.0 deep tunnels

This paper refers to experiments developed on the deep tunnels design of the Snowy 2.0 pumped-storage hydroelectric project in NSW, Australia. The 27 km long waterway and the power station complex are about 800 m below ground, and are in a complex tectonic and lithological setting. Long-term temperature monitoring in boreholes has been used to infer an empirical thermal model along the deep tunnels, which is presented as an example of input data for the ventilation design during construction, and for durability design during operation. An innovative aspect of this paper is related to the graphical interpretative method of borehole temperature logs that is proposed to infer downward or upward groundwater flows and predict the hydrogeological behaviour of fractured and faulted zones that cross the tunnel alignment. A large campaign of thermal acquisition in boreholes, using an acoustic televiewer probe, identified local anomalies of the geothermal gradient, which were correlated to permeability and pressure data measured in the boreholes, to identify zones of greater permeability that intersect the tunnels. Furthermore, the application of thermal measurements during tunnel excavation is proposed as an additional tool for the prediction of water inflow or identification of zones to be pre-grouted and/or drained. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices

Numerical investigation of indoor air quality in health care facilities: A case study of an intensive care unit

The risk of healthcare-associated infections (HAIs) is higher in patients admitted to intensive care units (ICU) and high dependency units (HDU). Currently, most ventilation studies focus on specialized areas, mainly isolation rooms and operating rooms. This paper focuses on the ventilation of multiple-bed hospital wards in developing countries. This study uses computational fluid dynamics (CFD) simulation to model and investigate airflow and the spread of pollutants. The study aims to investigate ICUs with various ventilation system designs. These predicted behaviors and characteristics were compared numerically to determine compliance with the requirements of airflow patterns, airborne contaminant distribution, and current international standards. The case study simulations were carried out using ANSYS Fluent simulation software as a solution tool. Three different ventilation systems, Vertical Laminar Airflow Ventilation (VLAF), Horizontal Laminar Airflow Ventilation (HLAF), and Temperature-Controlled Airflow Ventilation (TcAF), were modeled within five different designs to determine the most effective possible distribution of air inside the patient's room, based on different categories, primarily temperature distribution, CO2 concentration, and airflow distribution. The authors applied the TcAF technique in an ICU room, comparing the results of the proposed technique with those of other common techniques (HLAF and VLAF). It was found that TcAF showed the most effective airflow distribution around patients, isolating each patient from the others. However, the temperature distribution was excluded from the ASHRAE standard. HLAF with two exhausts is the most suitable option, with a lower CO2 concentration than the alternatives and a temperature that meets ASHRAE standards.

Experimental investigation and numerical modeling for induction fans

Induced ventilation systems have been widely used in the design of underground space architecture; they are used to agitate the air and eliminate the smoke and harmful gases formed by fire. In the application design of induced ventilation systems, most people often use the Computational Fluid Dynamics (CFD)-technique to simulate and study the flow distribution in underground space buildings. However, there has been little research carried out on the performance of the induction fan, which is a key equipment of induced ventilation systems, especially a lack of experimental verification data on the simulation model of the induction fan. In this paper, the performance of a specific type of axial induction fan is measured experimentally, modeled in CFD. The velocity boundary condition method was adopted for the modeling, and the k-w SST model was adopted for the turbulence model. The CFD model is validated using experimental data on velocity distribution along the axis of the fan jet. The experimental results show that, in addition to wind speed along the jet direction, the axial flow induction fan also has a large deflection wind speed in the y and z directions of 3D space at the outlet. The simulation results show that, along the jet direction, within 1.0 m from the fan outlet, when the efflux induced fan outlet was set to Uniform Wind Speed (UWS), Non-Uniform Wind Speed (NUWS) and Spatial Three-Dimensional Wind Speed (STDWS), the simulation results on average velocity along the jet axis were significantly different from the experimental values. At x = 1.0 m, the agreement between the STDWS simulation results and experimental values is about 183% higher than that of NUWS. With the development of the jet flow, the simulation results of UWS are basically consistent with those of NUWS, and the simulation results of STDWS are significantly better than those of UWS and NUWS, which are closer to the experimental values. At the far end of the jet, the three simulation values are in good agreement with the actual measured values, and the simulation values of STDWS are closer to the actual measured values.

Numerical simulation on exploring influencing factors of wind-driven natural ventilation effect in large indoor dock

The shipbuilding industry is booming and the health problems of workers caused by the harsh indoor dock environment force us to explore efficient and reasonable ventilation methods suitable for large workshops. Due to the strong specificity of large workshops, general or local ventilation methods cannot be universally applied. It has great potential and good economy to improve indoor environment by changing natural ventilation design. Computational fluid dynamics (CFD) has gradually become a powerful tool for predicting indoor and outdoor airflow organization and optimizing indoor ventilation. This paper adopts CFD to study the effect of the inflow wind speed, the position of the side wall shutters, the area ratio and form of roof ventilators on the effectiveness of natural ventilation in a large shipyard driven by wind pressure. The results show that the influence on total ventilation volume is more obvious when the intake side is shaded than the exhaust side. Different incoming wind speeds will affect the wind pressure at the ventilation position, which is the decisive external factor affecting the natural ventilation of docks. When the area ratio of roof ventilators increases to a certain extent, its continued increase has an insignificant effect on the total ventilation volume. The influence of changing the arrangement of the roof ventilator on the natural ventilation effect can be neglected when the area ratio is kept constant.