Ventilation Design Research Articles

Ventilation measures to control aerosol transmission based on COVID‐19 outbreaks in hospitals in Japan

AbstractCOVID‐19 outbreaks occurred in several hospitals, and the National Institute of Infectious Diseases, local authorities, and universities carried out investigations into ventilation in hospitals. The results indicated that ventilation performance was insufficient to prevent aerosol infection due to poor air conditioning, equipment maintenance, and existing ventilation design guidelines. The authors investigated guidelines for ventilation measures for general patient wards with the cooperation of The Society of Air‐Conditioning and Sanitary Engineers of Japan and the Japanese Society for Infection Prevention and Control. Based on a survey of COVID‐19 outbreaks in hospitals, ventilation countermeasure plans for 3 stages (a. normal conditions, b. increased risk of outbreaks, and c. infected patients treated) were compiled.

Simulation of natural ventilation for semi-enclosed buildings

Energy-saving buildings have become a topical issue and widely used the energy-saving ventilation design, which aims to maximize the use of natural ventilation while reducing demand on mechanical ventilation. In this research, natural ventilation performance of two different semi-enclosed building layouts, "O" type and "L-L" type, are studied by numerical simulation. According to the simulation results, in the "O" type, the maximum indoor air velocity occurs in building A (orientation facing the inflow direction). The minimum indoor air velocity occurs in building C (orientation facing building A). In the "L-L" type, the maximum indoor air velocity occurs in building A (orientation facing the inflow direction). The minimum indoor air velocity occurs in buildings B and D (orientation parallel to the inflow direction). And air flow field simulation results show that, the "L-L" type exhibits better than the "O" type in natural ventilation. Furthermore, simulation results show that the natural ventilation performance in the room is influenced not only by the building orientation, but also by the window size.

Ventilation design of tour buses for suppressing airborne transmission and highly efficient virus elimination in post COVID-19 period

Ventilation design of tour buses for suppressing airborne transmission and highly efficient virus elimination in post COVID-19 period

ОСОБЛИВОСТІ ВЛАШТУВАННЯ ВЕНТИЛЯЦІЇ В ЗАХИСНИХ СПОРУДАХ ЦИВІЛЬНОГО ЗАХИСТУ

Given the urgency of armed aggression, ensuring the safety of the civilian population is of utmost importance. Various types of structures are used for this purpose, including simple shelters, anti-radiation shelters, storage facilities, and dual-purpose structures. The construction of these facilities must be equipped with diverse internal engineering systems to ensure the livelihood of people. With the introduction of the updated State Building Code of Ukraine (DBN) B 2.2.-5:2023 [1], the requirements for the engineering support of these structures have significantly increased. This article aims to analyze the features of arranging engineering systems in these facilities, particularly ventilation systems, and provide recommendations for specific cases of ventilation and conditioning system installation.
 The article examines regulatory requirements for the installation of ventilation systems in the most common civil defense structures at present - anti-radiation shelters and dual-purpose structures with NBC (nuclear, biological, chemical) properties. Using the solution to a differential equation, the concentrations of carbon dioxide in rooms with people present are calculated depending on the ventilation mode: normal, reserve, and emergency. It is determined that in all cases, the concentration will not exceed the critical value. Recommendations are given for the design of ventilation systems for these buildings, and the specifics of ventilating and cooling rooms in diesel power stations for backup power supply are discussed.
 It is revealed that, at significant capacities of diesel power stations, the arrangement of ventilation for cooling becomes structurally complex. Solutions to this problem are proposed. It is recommended for large NBC structures and dual-purpose structures to have two ventilation chambers with separate air intakes. This will help reduce the risks of contaminating the inflow air and prevent an increase in carbon dioxide concentration during fires near civil defense structures.

An investigation concerning optimal design of confluent jets ventilation with variable air volume

This parametric study aims to predict the performance of confluent jets ventilation (CJV) with variable air volume (VAV) from four CJV design parameters. A combination of computational fluid dynamics (CFD), and response surface method (RSM) has been used to predict the energy efficiency, thermal comfort and IAQ for the four expected vital design variables, i.e., heat load (XH), number of nozzles (XN), airflow rate (XQ) and supply temperature (XTS). The RSM was used to generate a quadratic equation for the response variables exhaust temperature (TE), supply temperature (TP), PMV, DR, εT and ACE. The RSM shows that the TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to generate setpoints optimized for thermal comfort (PMV) for summer, spring and winter cases with different CLO factors and different TS under a scenario where the heat load varied between 10-30 W/m2. TE was used as setpoint to regulate the airflow rate to keep the PMV values close to zero. The results show that by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can be improved. Further energy reduction can be gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the heat load is decreased. This means that a CJV can effectively be combined with VAV to improve environmental performance with good thermal comfort (-0.5 < PMV < 0.5, DR < 20%), above average IAQ (ACE ≈ 106%) and with a higher heat removal efficiency (ε T ≈110%) than conventional mixing ventilation.

Assessing and exploiting the interaction between ventilation and geothermal systems in an underground data centre

Digitalization and population growth lead to the development of underground data centres, while simultaneously current climate goals stimulate the development of renewable energy sources. In this framework, this study evaluates the so far unexplored domain of geothermal activation of an underground data centre using numerical modelling. Computational fluid dynamics simulations are used to properly represent the air domain. The focus of the work lies on the analysis of the interaction between ventilation and geothermal systems in the data centre, a topic that has never been evaluated for energy geostructures in general. This leads to the possibility of suboptimal air ventilation system design and thus a potential for optimization, especially in underground data centres where daily ventilation requirements are determined by air temperature limitations. The analysis first explores the sensitivity of geothermal potential to varying ventilation conditions (airflow velocities), heat release conditions in the data centre and fluid velocities in the pipes of the geothermal activation. The impact of geothermal activation on air temperature in the underground data centre cavern is then assessed and thus the consequent impact on the ventilation system. Geothermal activation of a section of the cavern leads to a regional decrease in air temperature, which allows optimization of the whole system by reducing mechanical ventilation requirements while still respecting the temperature limitations within the data centre. The economic and environmental benefits of this optimization are also explored. Overall, it is proven that ventilation conditions have an influence on the geothermal potential that can be extracted, and optimization of the complete system is possible when considering the effect of geothermal heat extraction in underground data centres while determining their ventilation requirements.

Experimental and numerical study on airflow-dust migration behavior in an underground cavern group construction for cleaner production

A large amount of dust will be generated during the construction of underground cavern group. The understanding of the dust migration in the construction ventilation of the underground cavern group can help to optimize the cavern group’s ventilation design and improve the ventilation scheme of the cavern group’s rationality. In this paper, the effects of dust particle size, dust migration path, initial dust concentration in cavern, tunnel entrance wind speed and air duct outlet wind speed on dust migration were studied by combining a model test and numerical calculation. The results show that in the process of dust ventilation migration, the larger the diameter of the dust particles, the more difficult it is to discharge. The time of dust concentration reducing to 2 mg/m3 has a logarithmic distribution with ventilation conditions. The high-speed airflow from the outlet of the air duct is an important factor affecting the migration of dust. The development of airflow is divided into vortex region, recirculation region, collision region and stability region. Vortex region and collision region have lower wind speed and higher dust concentration, which are the unfavorable positions in the ventilation process. In the actual construction process, shortening the distance of dust migration can make the dust discharge quickly. The amount of dust generated by construction has a significant impact on the peak concentration of dust migration. During the ventilation process, the wind speed at the entrance of the tunnel and at the outlet of the air duct has a significant impact on the migration time of dust, at the same time, the ventilation efficiency should be considered while selecting the wind speed.

Enhancing Indoor Environmental Quality and Sustainability in Post-Pandemic Office Settings: A Study on Displacement Ventilation Feasibility

The COVID-19 pandemic has catalyzed global efforts toward transitioning to a sustainable society, driving rapid innovation in building technologies, working practices, building design, and whole life cycle environmental impact consideration. In this pursuit, this study explores the enduring impact of these on an alternative ventilation approach for both existing building renovations and new building implementations. Comparing displacement ventilation to mixed-mode ventilation in a Finnish office building with varying occupancy densities, this study examines indoor air quality (IAQ), thermal comfort, total building energy performance, and embodied carbon. The findings reveal that the basic case of mixed ventilation has a specified system primary energy value of 38.83 kWh/m2 (with 28 occupants) and 39.00 kWh/m2 (with 24 occupants), respectively. With the displacement ventilation alternative, it reduces this by 0.3% and 0.1%, enhancing thermal comfort and decreasing turbulence as well as having a marginal decrease in embodied carbon. In general, the study offers three-fold contributions: insights into post-pandemic office mechanical ventilation design with an emphasis on sustainability and ecological footprint considerations, a concrete case study addressing climate action and human-centric IAQ design, and a multifaceted analysis using the Environmental, Social, and Governance (ESG) paradigm, contributing to the groundwork for associated future research and policy progress.

Aspiration efficiency and respiratory tract deposition of indoor suspended micro-particles during steady and transient breathings

The assessment of potential health risks from exposure to airborne contaminants and the inhalability of microparticles through human nasal breathing is crucial for the design of ventilation systems. In this study, using a standing computer-simulated person (CSP) directly linked to a numerical model of the respiratory tract, we investigated the aspiration efficiency (AE) of microparticles ranging between 1 and 80 μm under steady and transient breathing conditions. Two ventilation scenarios with displacement and mixed ventilation systems (DV and MV) were assumed for AE calculations. To determine the appropriate particle injection location, we investigated the position of highly inhaled particles corresponding to the breathing zone using a reverse particle-tracking simulation with reversed time progression. Additionally, the total and regional deposition fractions (TDF and RDF) of the inhaled microparticles on the respiratory wall surfaces were evaluated using the Lagrangian approach. The results indicate that the transient breathing cycle showed relatively higher AE and TDF rates compared to the assumed steady inhalation conditions, particularly for the size range 1–10 μm. An insignificant variation was observed in the AE and RDF results between different ventilation systems. However, microparticles in the MV room showed slightly higher AE than the DV system. Moreover, AE and penetration ratio were highly sensitive to the initially assumed particle density. For a comprehensive and accurate assessment of inhalation exposure to microparticles, we should predict the heterogeneous flow field formed around the human body and then analyze the AE and TDF in the respiratory tract during realistic transient breathing.

Heat removal and ventilation limitations of the solar chimney attached with a built enclosure: Correlations of thermal Rayleigh numbers, port arrangements and discrete heating elements

For energy efficient ventilation and low carbon design, solar chimney has been extensively applied on buildings. In the present work, three representative solar chimneys were introduced, i.e., Model 1 with top-horizontal outlet, Model 2 with upper-vertical outlet and Model 3 with middle-vertical outlet. Updraft ventilation from the built enclosure to the outlet and heat transfer from the absorber to the fluid by heat convection were numerically and theoretically investigated, and their limitations and correlations with governing parameters were also discussed. Streamlines and heatlines were used to visualize transport paths of air and heat respectively. Reverse flow could not be observed in the solar chimney channels of Model 2 and Model 3; Therefore, total volume flow rate induced by the solar chimneys Model 2 and Model 3 and convection heat transfer rate of the absorber increases positively with thermal Rayleigh numbers (Ra). Model 2 chimney produces greater thermal buoyancy than that by Model 3, and its air flow rate is higher than that of Model 3. Generally, volume flow rate induced in Model 1 is higher than those of Model 2 and Model 3 as Ra is no more than 2.5 × 106, and simultaneously, convection heat transfer rate Nusselt number (Nu) is also greater than those of Model 2 and Model 3. When Ra exceeded 2.5 × 106, reverse air flow was intensified further, Nu of Model 1 started to decline. The three models with discrete heat sources could induce more air from indoor than that respective model without discrete heat sources. The maximum increment rate is obtained by the Model 1 solar chimney with discrete heat sources, then Model 2 and the least done by Model 3. Their power relationships between Nu and Ra, V*and Ra are regressed respectively. The dependence of volume flow rate on broad thermal Rayleigh numbers covering all the three flow regimes showed that there were linear correlations between discrete numerical volume flow rates and the scaling predictions, except in Model 1 for high Ra (exceeding critical value 9.0 × 105), where volume flow rate was remarkably reduced due to reverse air flow. This research could provide useful theoretical information for applying small sized vertical solar chimneys attached to the building sidewall to effectively reduce built energy consumption.

The Numerical Simulation Study of Pumping Airflow Driven by Wind Pressure for Single- and Multi-Room Buildings

Pumping airflow occurs in single-sided natural ventilation buildings when the openings are located on the leeward side; the direction of airflow through the building then changes periodicity. In order to propose a calculation method of the ventilation rates for single-room buildings and analyze the pumping ventilation for multi-room buildings, the CFD method with an SST k-ω turbulence model was used to conduct numerical simulation in this study, which is verified by other experimental results. Firstly, the qualitative and quantitative characteristics of pumping ventilation were investigated for a single-room building with two openings. The results show that the steady-state method underestimates the ventilation flow rates, and the unsteady-state method captures the microstructures of the flow better. Secondly, the vortex-shedding and indoor airflow oscillation frequencies were analyzed based on transient simulation for a single-room building. It was found that both of them increase with air speed. Then, the factors affecting ventilation flow rates were analyzed. A calculation method for dimensionless ventilation rates is proposed. Finally, the pumping ventilation for a multi-room building was numerically simulated. The ventilation rate for a middle room is greater than that for a corner room, and the ventilation rate for any room in a multi-room building is greater than the single-room building given the same room size and the same incoming wind speed. The findings of this paper are helpful for the design and evaluation of natural ventilation.

Guidelines for elevator design to mitigate the risk of spread of airborne diseases

Airborne viral transmission in confined spaces, such as elevators, could lead to the spread of diseases such as COVID-19. A quantitative study of viral transmission in enclosed spaces, with a focus on assessing the efficacy of the present ventilation methods is hard to find. Additionally, there is a lack of guidelines for viral dispersion. The non-availability of such information reduces overall effectiveness in controlling the spread of the virus. A properly designed ventilation system for the elevator car will benefit in both pandemic situations as well as non-pandemic situations, especially for people using hospital elevators. For better control of the airborne viral transmission spread, it is essential to study the airflow in elevator cars. Exposure to high-emitter coughing for one minute by a SARS-CoV-2-infected person in an elevator can increase the risk of the virus reaching the lungs by generating a viral load that may remain airborne for a long time. There is little that has been considered for lessening the anticipated viral load in the elevator car. In this paper, we use a two-step approach. The first step is the risk assessment, and the second is risk mitigation. The risk is assessed by computing the probable viral load a healthy passenger will be subjected to during the typical travel in an elevator car contaminated by the ride of an infectious person. It is seen that the ventilation provided as per the minimum permissible requirements by various international codes is inadequate to maintain the viral load in the elevator car below the risky levels. To come up with the risk mitigation strategies, the required ventilation in the car was computed using a Computational Fluid Dynamics (CFD) model. Further, mathematical models are developed to enable quick calculations during the design of the elevator car ventilation system. Our CFD study shows that in the case of a 20-passenger capacity elevator car, with doors open, a 2000 Cubic Feet per Minute (CFM) airflow will disperse most of the viral load in less than one minute. In this paper, we give easy-to-follow design guidelines, and mathematical models to enable quick calculations during the design of the elevator car ventilation system. This study is useful for practicing engineers to achieve effective ventilation of the elevator car to curtail the spread of viral transmission.

Analysis of the Indoor Climate in a Small, Newly-Built Auditorium

Abstract The article focuses on an analysis of the indoor climate in a small, newly-built auditorium. Providing optimal indoor climate parameters in the interiors of a university is extremely important for students. Meeting these parameters is essential not only from a physiological point of view, but also to achieve desirable student performances. The parameters of CO2 concentration are also influenced by the air distribution system in a small auditorium. The correct positions of the supply and extract air is very important. The first experimental measurements of CO2 concentration were carried out in a small auditorium in an old building. The natural ventilation of the small auditorium was evaluated. The second experimental measurements of the CO2 concentration were made in a small auditorium in a newly-built building. The ventilation system and the modern air distribution system of the small, newly-built auditorium were evaluated based on the CO2 concentration and the PMV index. A Testo 480 was used for the measurements. The conclusion of this paper contains the recommendations for the design of a newly-built ventilation system in a small auditorium.

What are the impacts of architectural design on occupants’ well-being, and how can architects optimize spaces to enhance productivity?

In the context of rising urbanization and the growing enhancement of green architecture, architectural design is a topic of increasing importance. This study examines the detailed relationship between architectural design and the human experience, emphasizing the significant effects of design decisions on people's well-being. The research delves into the psychological effects of architectural design and explores how architects can optimize spaces to increase occupants' productivity and well-being while taking environmental sustainability and cost-efficiency into account. Numerous studies have demonstrated the critical relationship between indoor environmental conditions and occupant well-being. This study examines the relationships between architecture and the effects that various elements have on inhabitants' moods, behavior, and general well-being, including ventilation, lighting, color, layout, and biophilic design. Further, it discusses possible solutions that could be implemented, such as eco-friendly architectural design, adaptable floor plans, biophilic design principles, and a variety of color and aesthetic decisions to create environments that foster occupant comfort, creativity, and productivity. The study does, however, identify a few limitations including the possible financial effects of incorporating sustainable design elements. Architects can play a critical role in creating environments that improve the quality of life and productivity of their occupants while respecting the environment and budgetary constraints by taking into account the psychological effects of design choices and advocating for innovative, sustainable, and occupant-centric design approaches.

Features of ventilation and air conditioning design in deep mines

Features of ventilation and air conditioning design in deep mines

Numerical Simulation of Airflow Organization in Paint Spraying System of car Lampshade

According to the design requirements of the airflow organization of the car lampshade paint spraying system, the corresponding physical model is established, and the flow state of the air organization in the entire paint spraying system was simulated using Fluent software. On this basis, the wind speed of all mechanical air supply and air exhaust in the paint spraying system are adjusted to find the optimization and improvement direction of the airflow organization, so that the air pressure and wind direction in the system meet the environmental requirements of the car lampshade painting process, economically reducing the harm of paint, and providing reference for the ventilation design of the paint spraying system.

Quantifying Ventilation Design, Room Layout, and Occupant Activity Parameters during Aerosol-Generating Medical Procedures in Hospitals

The risk of airborne disease transmission in hospital rooms during aerosol-generating medical procedures is known to be influenced by the size of the room, air ventilation rate, input-to-output flow ratio, vent surface area, and vent location. However, quantitative recommendations for each ventilation design parameter are scarce. Moreover, room layout and occupant activity parameters, such as furniture locations and healthcare worker movement, are often omitted from studies on airborne disease transmission in hospital settings. As a result, the development of policies and technologies aimed at mitigating airborne disease transmission in hospitals has been limited. To address this shortfall, this study is aimed at first characterizing existing ventilation, room layout, and occupancy parameters in hospital rooms where aerosol generation medical procedures (AGMPs) occur and then testing the hypotheses that ventilation, room layout, and occupancy parameters vary significantly between hospital rooms and, in some cases, with time. Information on AGMPs was collected via a survey circulated to healthcare workers within British Columbia’s Interior Health Authority (IHA), while hospital room and ventilation system information was collected by reviewing drawing packages of 37 IHA hospital rooms. The survey results indicate that AGMPs commonly occur in trauma, ICU, or general ward rooms with positive or negative pressure ventilation systems. Statistical tests, with room type (trauma, ICU, or general), room pressure (positive or negative), and/or time as independent variables, show that variables relating to ventilation (number of supply vents, supply and exhaust vent location, ventilation rate, and supply and exhaust area) and room layout (congestion score, room volume, light area, and number of lights) vary with room type but not with room pressure. Occupant activity variables (number of workers, number of moving workers, and speed score) also vary with room type, although to differing extent with room pressure and time. The survey and drawing review data presented in this study can help guide systematic comparisons of mitigative technologies as well as parametric investigations on how room layout, ventilation, and operational parameters influence airborne disease spread. This is a crucial first step in achieving quantitative and clinically relevant recommendations for mitigating airborne disease transmission in healthcare settings.

A Calculation Method of Heat Release Rate Based on Flame Spread Rate: Applied in a High-Speed Train Carriage Fire

ABSTRACT Heat release rate (HRR) is an important parameter for the fire safety assessment of high-speed trains and the design of tunnel ventilation systems. However, the existing theoretical calculation methods of the HRR do not consider the fire development process and can not accurately obtain the HRR of high-speed trains. This paper uses a combination of theoretical analysis and numerical simulation to study the HRR of high-speed train fires. Firstly, based on the flame spread rate, a calculation method of the HRR is established, called the spatial time-series superimposed method. The accuracy of the calculation method is verified through a small-scale combustion experiment. Then, the calculation model of the HRR of the high-speed train fire is obtained according to the heat release rate per unit area (HRRPUA) of the carriage material, the flame spread rate in the carriage, and the spatial time-series superimposed method. Afterward, the calculation model is modified according to the change in combustion intensity during the flame spread in the high-speed train carriage. Finally, the calculation method of the HRR established in this paper is compared with several existing calculation methods. The results show that the HRR curve obtained by the calculation model is consistent with that obtained by the FDS simulation. The maximum relative error is less than 25%, and the relative error of the peak heat release rate (PHRR) is 7.4%. Therefore, this study can provide a reference for the fast and accurate calculation of the HRR of the high-speed train carriage fire.

A prediction model for smoke exhaust efficiency of rescue stations in railway tunnels with semi-transverse ventilation

This study analyzes the effects of heat release rate (HRR), fire position, smoke exhaust velocity, shaft diameter, and ambient pressure on the smoke exhaust efficiency in a rescue station with semi-transverse ventilation. The results demonstrate that the shaft close to the fire source has higher smoke exhaust efficiency, but the fire location has little effect on the overall smoke exhaust efficiency. The smoke exhaust efficiency decreases with the increase of HRR and is proportional to the -1/3 power of the dimensionless HRR. Before the smoke is overall controlled in the rescue station, increasing the smoke exhaust velocity can improve smoke exhaust efficiency, and the smoke exhaust efficiency is proportional to the 2/3 power of the dimensionless smoke exhaust velocity. When the smoke in the rescue station is overall controlled, increasing the exhaust velocity can reduce the smoke spread distance. Moreover, the smoke exhaust efficiency is proportional to the 9/5 power of the dimensionless shaft diameter and 0.3 power of the pressure ratio. Finally, combined with theoretical analysis, a prediction model of the smoke exhaust efficiency is obtained. Therefore, this study can guide the design of the semi-transverse ventilation system in extra-long railway tunnel rescue stations at different altitudes.

Buckling analysis of thin plates with circular cut-outs for sustainable ventilated food packaging design

Thin plates with circular cut-outs are widely used in engineering structures such as bridges, construction, and ventilated corrugated paperboard boxes in food packaging. This study investigates the critical buckling loads of thin elastic plates comprised of a single circular hole at different locations and with different sizes. To determine the critical loads, experimental tests and finite element method simulations are conducted. The vertical location and the diameter of the hole impact the buckling results significantly. The results indicate a significant correlation between the experimental and finite element data. The study develops second and third order polynomial formulas that predict buckling loads. In this study, corrugated paperboard plates were used as samples to gain insights into ventilated food packaging designs, aiming to enhance their buckling strength while reducing packaging material consumption for packaging sustainability purposes. The solution proposed in this study can be applied to predict the buckling of other elastic thin plate structures with a circular hole, relevant to industries such as construction and aerospace.