Ventilation Design Research Articles

Impact of Diffuser Location on Thermal Comfort Inside a Hospital Isolation Room

Thermal comfort is increasingly recognized as vital in healthcare facilities, where patients spend 80–90% of their time indoors. Sensing, controlling, and predicting indoor air quality should be monitored for thermal comfort. This study examines the effects of ventilation design on thermal comfort in hospital rooms, proposing four distinct ventilation configurations, each with three airflow rates of 9, 12, and 15 Air Changes per Hour (ACH). The study conducted various ventilation simulation scenarios for a hospital room. The objective is to determine the effect of airflow and the diffuser location distribution on thermal comfort. The Reynolds-Averaged Navier–Stokes (RANS) equations, along with the k–ε turbulence model, were used as the underlying mathematical representation for the airflow. The boundary conditions for the simulations were derived from the ventilation standards set by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and insights from previous studies. Thermal comfort and temperature distribution were assessed using indices like Predicted Percentage Dissatisfaction (PPD), Predicted Mean Vote (PMV), and Air Diffusion Performance Index (ADPI). Although most of the twelve scenarios failed to attain thermal comfort, two of those instances were optimal in this simulation. Those instances involved the return diffuser behind the patient and airflow of 9 ACH, the minimum recommended by previous studies. It should be noted that the ADPI remained unmet in these cases, revealing complexities in achieving ideal thermal conditions in healthcare environments. This study extends the insights from our prior research, advancing our understanding of ventilation impacts on thermal comfort in healthcare facilities. It underscores the need for comprehensive approaches to environmental control, setting the stage for future research to refine these findings further.

A comprehensive review of variable refrigerant flow (VRF) and ventilation designs for thermal comfort in commercial buildings

A comprehensive review of variable refrigerant flow (VRF) and ventilation designs for thermal comfort in commercial buildings

Characterization of the deflagration behavior of the lithium-ion battery module within a confined space under different ventilation conditions

Lithium-ion batteries (LIBs) have been widely used in the modern society, such as electric vehicle and energy storage system. The most common application scenario of LIB is in the confined space. LIBs were prone to release flammable gases (such as carbon monoxide, hydrogen, and hydrocarbons) under abuse conditions, and the gas accumulation deflagrated with catastrophic power especially in the confined space. The ventilation condition and cathode materials of the LIB influence the destructive power of deflagration. In this study, thermal runaway (TR) tests on the Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) and Li(Ni0.6Co0.2Mn0.2)O2 (NCM622) cells with different states of charge (SOCs) were conducted in a confined box under different ventilation conditions. The location of peak pressure, gas temperature, deflagration pressure, and the effects of ventilation were analyzed. Based on the measured values of the pressure at different locations, the peak pressure was generally located at the top of the confined space. The gas temperature and pressure of NCM811 batteries were generally higher than those of NCM622 batteries. NCM811 cells not only had a lower trigger temperature of thermal runaway (TR), but also a high destructive power of deflagration. The impact of ventilation condition on deflagration was studied, and the result of dimensionless analysis indicated that the deflagration pressure was influenced by opening factor, explosion gas volume, explosion heat, and explosion temperature. With the increasing of the opening angle of the window, the peak deflagration pressure firstly increased (from 30° to 60°) then decreased, indicating that there was an competitive mechanism between the combustion and pressure relief with the improvement of ventilation condition. This work helps us understand the hazards of LIB deflagration under different ventilation conditions and provides a reference for ventilation design in battery application scenarios which ensure the process safety through fire protection design.

A Comprehensive Index for Evaluating the Effectiveness of Ventilation-Related Infection Prevention Measures with Energy Considerations: Development and Application Perspectives

In the wake of the COVID-19 pandemic, prioritizing indoor air quality has emerged as a crucial measure for preventing infections. Effective ventilation is vital in mitigating airborne pathogen transmission and maintaining a healthy indoor environment by diluting and removing infectious particles from enclosed spaces. However, increasing the supply of pathogen-free air to enhance infection control can lead to a rise in energy consumption. Nevertheless, evaluating the overall efficacy of ventilation-based infection prevention strategies while considering their energy requirements has posed challenges. This scientific paper introduces the ICEE (Infection Control’s Energy Efficiency) index, a newly developed simple integrated index to assess the effectiveness of ventilation strategies in reducing infection risks while accounting for associated energy demands. The paper reviews the current understanding of ventilation strategies, their impact on infection prevention, and their corresponding energy consumption. By employing a straightforward analytical approach, this metric offers a comprehensive framework to optimize ventilation systems for both infection prevention and energy efficiency. To quantify infection risk, a simplified equation model is utilized, incorporating factors such as ventilation effectiveness and filter efficiency, in case of recirculation. Energy demand is determined using approximations and relevant values from existing literature. Reference cases are defined, distinguishing between natural and mechanically ventilated scenarios, as these reference situations influence the energy-related effects of any implemented measures. The paper outlines the methodology employed to develop the index and illustrates its applicability through exemplary measures. The proposed index yields valuable insights for the design, operation, and retrofitting of ventilation systems, enabling informed decision-making towards fostering a healthier and more sustainable built environment.

Modeling Environmental Conditions in Poultry Production: Computational Fluid Dynamics Approach

In recent years, computational fluid dynamics (CFD) has become increasingly important and has proven to be an effective method for assessing environmental conditions in poultry houses. CFD offers simplicity, efficiency, and rapidity in assessing and optimizing poultry house environments, thereby fueling greater interest in its application. This article aims to facilitate researchers in their search for relevant CFD studies in poultry housing environmental conditions by providing an in-depth review of the latest advancements in this field. It has been found that CFD has been widely employed to study and analyze various aspects of poultry house ventilation and air quality under the following five main headings: inlet and fan configuration, ventilation system design, air temperature–humidity distribution, airflow distribution, and particle matter and gas emission. The most commonly used turbulence models in poultry buildings are the standard k-ε, renormalization group (RNG) k-ε, and realizable k-ε models. Additionally, this article presents key solutions with a summary and visualization of fundamental approaches employed in addressing path planning problems within the CFD process. Furthermore, potential challenges, such as data acquisition, validation, computational resource requirements, meshing, and the selection of a proper turbulence model, are discussed, and avenues for future research (the integration of machine learning, building information modeling, and feedback control systems with CFD) are explored.

Rapid Design of an ICU Ventilator: An Approach Based on Smart Switching of Compressed Air-Oxygen.

Breathing support is provided by regulating volume or pressure of lungs using ventilators. Due to COVID-19 pandemic, there was a sudden shortage of resuscitating devices such as ventilators. Additionally, ventilators being one of the primary critical care devices are also very costly. In order to address this situation, a number of low-cost designs have been proposed, however, many of these lack either an efficient control system or a hardware comparable to a standard ICU ventilator. In this regard, this article presents a comprehensive cost-effective solution that covers all aspects of the ventilator design (named as NED-Vent) such as hardware/pneumatic assembly, electronic design, user interface and control system. The proposed design works on compressed air-oxygen switching via proportional valves to produce basic volume and pressure modes as well as their derivatives such as assist ventilation, intermittent ventilation and spontaneous modes. The NED-Vent also features an interactive single-knob-single-touch user interface along with an automated mechanism for adjusting air-oxygen ratio in breathing gas mixture as an improvement on existing designs. The pressure regulated control is based on two mathematical models of human lungs with dynamic lung parameters estimated using machine learning approach. Additionally, the controller is tuned to optimized stability using Jury's Test and Ziegler-Nichols methods. The obtained results of breath profile are validated for the employed mathematical models (SLSC & SLMC) as well as the tuning methods in compliance with the tolerances provided by international standards.

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.

Analysis of irreversibility on nanofluid flow through porous medium considering shape, dispersion and melting effects

This study is conducted to explore the impact of thermal dispersion and melting on the natural convective nanofluid (nickel zinc ferrite + SAE 20W-40 motor oil) flow over a stretching sheet in a Darcy porous medium. An irreversibility analysis has also been performed using the second law of thermodynamics. The fundamental nonlinear partial differential equations (PDEs) are converted into a system of dimensionless nonlinear ordinary differential equations (ODEs) through Lie group similarity transformations and then solved by employing the spectral local linearization method implemented in MATLAB software. It is noteworthy to highlight that the validation results indicate a strong concurrence with existing findings in previously published literature. After simulation, it is specified that the thermal dispersion disrupts the entropy (by 63.7%) and enhances the surface friction. Likewise, the heat transfer rate improves by 1.5% with the melting effect and 58.7% with the Darcy number. The results indicate that the brick-shaped particles exhibit a higher rate of heat transfer and lower entropy production. Further, this work has many uses such as, core, microwave, and biomedical applications like tumor treatments, bone plate surgeries, EMI (electromagnetic interfaces), electronics cooling, and aerodynamic extrusion processes, in the design of passive ventilation systems.

Average surface wind pressure surrounding tall buildings with cruciform shapes

Abstract Building shape affects wind pressure on building surfaces, while limited studies have examined how building shape affects the wind pressure on cruciform-shaped tall buildings. This article investigated the variation of the average wind pressure coefficient (AWPC) on cruciform-shaped tall buildings with the height–width ratio (HWR) and height–thickness ratio (HTR). The results demonstrated the occurrence of building blockage, wind separation, wind re-circulation, and wind re-attachment on building surfaces. The frontal surface of the main building was always the windward surface with positive wind pressure. At 2/3 of the building height (H), the peak AWPCs in all scenarios were ~0.70. However, in the case with an HWR of 3.66, the side surfaces of the main building and the frontal surfaces of the branch building, wind pressure was all negative. With the HWR reduction by building width increase, wind pressure on these surfaces became positive, where the AWPCs in the HWR = 1.41 case were 0.60–0.63 and 0.64–0.69 on side and frontal surface, respectively. With the HWR decrease, both positive and negative wind pressure intensified. Along the central axis (M1) in the vertical direction, wider buildings had stronger positive wind pressure on the frontal surfaces below 0.10H, while narrower buildings had stronger positive wind pressure above 0.82H. In comparison, HTR made limited differences to the wind pressure on the frontal surface. Overall, vertical results showed that scenarios with smaller HWR underwent stronger positive and negative wind pressures. On the HTR cases, wind pressure on top surfaces showed complicated results, while thicker buildings had weaker negative wind pressure on the back surface. Overall, this study is important to understand the characteristics of wind load on cruciform-shaped tall buildings and generate implications for wind resistance, natural ventilation design, and wind electricity generation over tall buildings.

The airflow characteristics and thermal comfort evaluation in high-speed train cabin with mixing ventilation: An experimental and numerical study

The airflow characteristics and distribution in high-speed train (HST) cabins have been of great significance for the travel comfort of passengers, while the indoor dynamic airflow characteristics and overall thermal comfort are still unclear. This study first conducted a transient experiment in a real train cabin with the mixing ventilation mode. Measurements showed that the turbulence intensity of the whole airflow is between 20% and 60%. The center zone airflow has a higher turbulence kinetic energy, while the spectral characteristics are closer to the natural wind with the β value between 1.2 and 1.8. Moreover, considering the limitations of the experiment, a corresponding numerical study was carried out. To be closer to the actual situation, the numerical simulation adopted a partitioned heat transfer wall setting, the average deviation of the airflow velocity and temperature from the experimental comparison was 0.057 m/s and 0.25 °C, respectively. Numerical results revealed two vortices in the seating area, a significant longitudinal airflow and an increasing temperature near the carriage ends. Then, to further analyze the compartment's thermal environment and the acceptance of airflow, thermal comfort indicators based on the airflow parameters were used. The predicted mean vote (PMV) showed the thermal comfort of the cabin is slightly cold. Predicted percentage dissatisfaction (PPD) and draught rate (DR) in the center area are barely satisfactory, more than 25% and 20%, respectively. The results of this study can provide an essential reference for the optimization design of ventilation systems in public transport.

Smoke exhaust characteristics under stack effect of natural ventilation by shaft in high-altitude tunnel

The number of high-altitude tunnels is increasing year by year and natural ventilation of shafts is widely used as a critical component of the ventilation system. For the design of ventilation systems, it is particularly crucial to consider the smoke exhaust performance of shafts in low-pressure environment. Therefore, this study simulates tunnel fires with natural ventilation by shaft in high-altitude areas, aiming to analyze the impact of atmospheric pressure on smoke exhaust performance and smoke exhaust capacity by natural ventilated shafts at 50 to 100 kPa atmospheric pressure. It appears from the results that the increasing of ambient pressure can enhance the ability of air entrainment and natural smoke exhaust, and thus plug-holing is more likely. In which condition, fresh air can be expelled straight from the shaft, reducing smoke exhaust efficiency. As ambient pressure increases, the critical shaft height for plug-holing decreases. By analyzing the smoke exhausting process by shaft and smoke flow, smoke exhaust capacity can be evaluated by obtaining the mass flow rate of exhausted smoke and fresh air from the shaft under various atmospheric pressures and fire source power and. It could be said that increasing ambient pressure and shaft height can improve the smoke expulsion performance before plug-holing. However, once plug-holing happens, the increase of shaft height can no longer expel more smoke but much more air is exhausted by shaft. It is hoped that this work will serve as a guideline for ventilation systems design in high-altitude tunnels.

Aerodynamic performance comparison of wind-driven turbine ventilators: A numerical investigation

Wind-driven roof ventilator is a cost-effective and environmentally sustainable solution for improving indoor ventilation and reducing energy use. This study aims to compare the ventilation performance of turbine ventilators with curved and straight blades of various sizes, utilizing both computational fluid dynamics (CFD) methods and experimental validation. Additionally, a mathematical expression is derived based on the aerodynamic principles of turbomachinery. The results indicate that both types of ventilators exhibit two streams of rotating airflow and an upward airflow. The angular velocity and ventilation rate demonstrate an approximately linear increase with higher wind speeds, and ventilators with smaller outer diameters experience a greater rate of increase in angular velocity. Larger-sized ventilators, despite having lower angular velocities, achieve higher ventilation rates for geometries of similar proportions. However, it should be noted that reducing the throat diameter may result in inadequate ventilation rates. In general, straight blade ventilators outperform curved blade ventilators, yielding 10%–38% higher ventilation rates due to their lower flow resistance. The discharge coefficients for the former and the latter are 0.32–0.37 and 0.25–0.32, respectively. The derived mathematical expression based on aerodynamics agrees well with the simulation results, providing a means for predicting ventilator performance. The objectives of this study are to enhance understanding of the ventilation performance of two types of turbine ventilators, aid in the selection and design of wind-driven roof ventilators, and promote improved indoor ventilation and energy efficiency.

Study on the effect of width and slope of large cross-section tunnel on critical velocity of fire

When a tunnel fire occurs, due to the difference of tunnel width and slope, both smoke countercurrent length distribution law and critical velocity will become different, and these two are very important parameters in tunnel longitudinal ventilation design. Therefore, for the design of smoke control and longitudinal ventilation of the tunnel, based on actual highway tunnel size, this paper established and ran a series of numerical simulations through FDS simulation software to study tunnel width and slope?s effect on smoke countercurrent length and critical velocity. The results of this paper show that smoke countercurrent length decreases with tunnel slope?s increase and increases with tunnel width?s increase. Through dimensionless analysis, the prediction formulas of smoke countercurrent length and critical wind speed of large cross-section tunnel about tunnel width, slope and height are modified and established. The research conclusions can provide a theoretical basis for the longitudinal ventilation design, smoke prevention and exhaust measures and personnel evacuation in large cross-section tunnel fires.

Design and optimization of intelligent ventilation system in coal mine

With the continuous development of the coal industry, coal mine safety and environmental protection have gradually become the focus of important attention. The design and optimization of mine ventilation systems is a key factor in ensuring air quality and safety in the working area. In order to improve the application level of automation and intelligent equipment of mine ventilation system, under the existing conditions of mine, the design significance and goal of mine intelligent ventilation system are taken as the starting point, and the design and application effects are analyzed. By optimizing the layout of ventilation routes, increasing the number of sensors, building an intelligent ventilation system, optimizing the ventilation scheme in the main production scenarios such as coal face, driving face and opening up main roadway in the daily production process of the mine, realizing rapid wind regulation and wind counteraction when disasters occur, and using air flow short circuit to form protective measures, effectively avoiding the expansion of disasters and accidents. At the same time, remote automatic control of ventilation facilities and equipment is carried out to effectively improve the optimal utilization of air supply, avoid the phenomenon of insufficient air supply and waste of air volume, and improve the intelligent level of mine ventilation system.

Design and Performance Evaluation of a Low-Cost Non-Invasive Electromechanical Ventilator With Feedback Mechanism

Design and Performance Evaluation of a Low-Cost Non-Invasive Electromechanical Ventilator With Feedback Mechanism

Heating, Ventilation, and Air Conditioning (HVAC) Engineering Design Methods and System Analysis

Heating, Ventilation, and Air Conditioning (HVAC) Engineering Design Methods and System Analysis

Dynamics of harmful factors in inclined road tunnels according to the results of numerical modeling of up to 50 MW fires in terms of natural ventilation

The present paper explores the change of the harmful factors by means of full-scale numerical models. In the numerical models, the tunnel length is 400 m; the slope gradient varies within 0-9%, with a 2% step; and the heat release rate is within 5-50 MW. The outdoor air temperature on the models was assumed to be 20℃, while the pressure difference between the portals on different models varied depending on the slope, and the variation range was 50-400 Pa. The modeling results show that the propagation of the harmful factors is characterized by stabilization as demonstrated by the fact that the distance of descending propagation of the harmful factors decreases for each specific tunnel gradient and eventually shows a pronounced asymmetry with respect to the seat of fire. This confirms the preferential and pronounced ascending movement of the ventilation flow with toxic products of combustion. Thus, the worst results during the natural ventilation are expected for ascending flows. Based on the isolines of temperature, as well as the concentrations of carbon monoxide and oxygen, the gradient factor can be calculated, which can be used to design ventilation systems for engine tunnels, ensure their safe operation and save human lives during the fire.

ExoventQ: A Novel Low-Cost Portable Negative Pressure Ventilator Design and Implementation

ExoventQ: A Novel Low-Cost Portable Negative Pressure Ventilator Design and Implementation

Numerical simulation for optimising of inlet and outlet positions for mechanical ventilation and heat dissipation: A case study to improve ventilation in an indoor 110kV substation

Efficient ventilation and heat dissipation in indoor substations are crucial for the stable operation of transformers. This study investigates the impact of inlet and outlet positions on ventilation and heat dissipation performance in a 110kV indoor substation using computational fluid dynamics. A model of the 110kV main transformer chamber is developed. Twelve combinations of inlet and outlet positions are analysed. Inlet positions include side walls parallel to radiators, side walls perpendicular to radiators and both side walls perpendicular to radiators. Outlet positions include the top of the chamber, the side of the inlet, adjacent to the inlet, and opposite inlet. Results demonstrate that locating outlets at the top of the chamber reduces transformer temperature by 0.5-1.6?C and increases energy utilization by8.6%-24.8% regardless of inlet position. Two opposite inlets perpendicular to radiators allows even air distribution between radiators. And this configuration reduces transformer temperature by 3.4?C when the outlet is located at the top of the chamber. Overall, the optimal ventilation design involves top chamber outlets and inlets on opposite walls perpendicular to radiators.

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.