Ventilation Design Research Articles

Harnessing the power of computational fluid dynamics for flow coefficient and rain resistance improvement of Type 1 Natural Ventilators

Type 1 Natural Ventilators act like a shield protecting the building from rain intrusion while allowing air to flow from outside. Despite their wide applications, they are far from the ideal design, mainly due to a lack of data on their air discharge coefficient and rain defense effectiveness under different climatic conditions. According to ventilation standards, since experimental testing of different geometries and configurations of these ventilators are complex, difficult, and costly, this study aims to implement Computational Fluid Dynamics (CFD) tools to investigate their performance. To do this, a combination of 9 various louvre panels was designed with 1, 2, and 3 blades and 5, 10, and 12 cm pitches following type 1 Natural Ventilator design standards. Accordingly, a geometrical model including the louvre panel and the wind tunnel is created, meshed, and tested under different climatic conditions. A mesh independency study and a validation analysis were also done to confirm the validity of the data. The pressure loss and signs of water penetration were monitored while the louvre panel was subjected to an air stream into which water is introduced using an array of nozzles to simulate the wind-blown rain. The results showed that the CFD tool was a strong technique in determining the louvre panels' performance. Accordingly, four categories were defined to separate louvers’ performance in case of their air discharge coefficient and rain defense effectiveness. Namely, category #1 included the 2-blade louvre with 10 and 15 cm pitch and the 3-blade louvre with 15 cm pitch with a relatively high discharge coefficient and rain defense. The result demonstrated that the discharge coefficients of all louvres were not sensitive to wind velocity in the range of 5–10 m/s compared to those in the velocities less than 5 m/s and higher than 10 m/s. In addition, the discharge coefficient decreases dramatically as the number of blades over the pitch ratio increases. Finally, according to the results of this study, it was understood that the choice of a louvre configuration is application specific; for instance for applications in which high airflow is the dominant requirement, louvres configuration in category 3, efficient for airflow only, are the best choices.

Experimental analysis of airborne contaminant distribution in an operating room with different ventilation schemes

Experimental and numerical investigations were performed in a research operating room to compare laminar air flow and turbulent mixing ventilation systems in reducing the concentrations of airborne germs and surgical smoke in operating room air. In addition, measurements at scattered positions were conducted to find positions that are suited best for airborne monitoring in real-time during surgeries. In the experiments, particle counters were used to sample tracer aerosols originating from the wound area and the facial area of the thermal manikins representing surgical staff. The results showed that it is important to perform monitoring close to the areas with high hygiene requirements. Increasing the air change rate with turbulent mixing ventilation significantly reduced the number of airborne particles, however, not in the surgical microenvironment. Our findings show varying results considering the particle concentration using laminar air flow compared to turbulent mixing ventilation. With laminar air flow, higher contaminant levels are obtained in the areas with a high demand for contamination reduction. In contrast, laminar air flow was more effective in reducing the concentration of surgical smoke in the facial areas of the surgical staff. Regarding airborne germs, monitoring should be performed at the instrument tables and close to the wound area to evaluate the risk for surgical side infections. These results can support the development of guidelines and best practices for operating room ventilation design and maintenance to improve patient safety and reduce the risk of healthcare-associated infections.

Research on Gravity Energy Saving Reconstruction Technology of Circulating Cooling Water in Mechanical Ventilation Cooling Tower of a Steel Plant

There is a height drop in the rain area of the circulating cooling water in mechanical ventilation circulating cooling towers, resulting in the ineffective use of gravitational potential energy. High-level water collection is an effective way to reduce the energy consumption of the cooling tower. Based on this, aiming to solve the gravity energy waste problem of circulating water in the cooling tower of a steel plant, this paper innovatively puts forward the high-level water tank to utilize the energy-saving transformation technology of turbine power generation and pump power saving. Additionally, this paper explores the energy-saving effects of the two methods under different height drops. The results show that the maximum utilizable rain area height of the cooling tower is 5 m, while the annual electric energy output of turbine technology can reach 4.704 million kW·h. The high water collection technology can reduce pump power consumption and save up to 7.35 million kW·h per year of electric energy, maintaining a more significant energy-saving ability compared with the turbine power generation technology. In terms of performance, the design of a high-level water tank is to help eliminate rain areas and improve the heat exchange efficiency of water and gas, so that the water temperature of the outgoing tower is 0.13 °C lower than that of the conventional cooling tower. Meanwhile, the ventilation resistance in the rain area is weakened, the resistance coefficient can be reduced by about 40–50%, and the noise can be reduced by about 10 dB (A) under the action of the water collection device. According to the economic evaluation, the total cost of turbine power generation technology is 0.563 million dollars and the total cost of high-level water collection technology is 0.446 million dollars. The cost can be realized within two years, but the high-level water collection technology avoids additional pump maintenance costs and has better economy. This study provides a theoretical basis for the transformation and optimization design of mechanical ventilation cooling towers, and has important reference value.

Research on Ventilation and Heat Insulation Layer Design of Split-Type Roof Greening Based on Topological Interlocking Principle

In this paper, the roof ventilation and heat insulation layer modules are combined with the roof greening, and each module is assembled and combined through the principle of topological interlocking. The assembly of these modules does not require any rivets or cement mortar, and the structural stability of the overall assembled roof can be achieved only through the interlocking and limiting of the specific geometric shapes between the modules. Due to the modular design, this kind of green roof has strong applicability and can be applied to roofs of different shapes. Such a roof can not only meet the aesthetic needs, but also beautify the urban environment and reduce carbon emissions.

Estimation of airborne infection risk in a school classroom according to operation of a floor-standing type ventilation system

Horizontal airflow, typically from floor-standing type ventilation systems used in school classrooms in some countries including Korea, may increase the risk of airborne infection. To estimate such risk, we conducted experiments in a classroom using simulated particles (DEHS) following the ventilation system discharge angles [upward (+45°), straight (0°), and downward (−45°)] and airflow rate (200 and 400 m3/h), along with desk partitions and simulated human heat release in a classroom. Calculations using the revised Wells–Riley equation showed that horizontal air supply potentially increases the infection risk by transporting particles [coarse (3.0–5.0 μm) and fine (0.5–3.0 μm)] over extended distances, from the air inlet to the back of the classroom. In comparison, downward air supply reduced the overall average infection risk by 30.1% compared with horizontal direction. Desk partitions yielded inconsistent effects, with short-term (5 min) and long-term (20 min) reductions in infection risk. However, when the internal heat gain increased, the average estimated infection risk decreased by 24.0%. Therefore, the risk of airborne infection could be reduced by changing the discharge angle of ventilation systems. Our findings could be useful in developing operating guidelines for existing ventilation systems or designing ventilation systems that reduce infection risk in classrooms.

The Effect of Ventilation on the Hazards of Hydrogen Release in Enclosed Areas of Hydrogen-Fueled Ship

This paper presents a systematic investigation that encompasses the safety assessment of a fuel preparation room (FPR) intended for a hydrogen-fueled ship. The primary objective is to determine the appropriate ventilation strategy to mitigate the risks associated with potential hydrogen leakage. The study focuses on a case involving an FPR measuring 10.2 m × 5.3 m × 2.65 m, which is part of a 750 DWT hydrogen-powered fishing vessel. To identify the potential events leading to hydrogen dispersion, an event tree analysis is conducted. Additionally, existing regulations and guidelines related to the safety assessments of hydrogen leakage in enclosed areas are summarized and analyzed. Computational fluid dynamics, FLACS-CFD, are utilized for the consequence analysis in order to evaluate the impact of ventilation on hydrogen dispersion and concentration within the FPR. The research findings indicate significant effects of ventilation on the hazards and safety assessments of FPRs and high-pressure fuel gas supply systems. The study highlights that hydrogen vapor tends to accumulate at the ceiling and in the corners and spaces created by the equipment. The position and size of ventilation openings greatly influence the dispersion of hydrogen leakage. Proper ventilation design, including top inlet ventilation and outlet ventilation on the opposite side, helps to maintain a safe FPR by facilitating the efficient dispersion of hydrogen vapor. Moreover, locating inlet ventilation on the same side as the outlet ventilation is found to hinder dispersion, while the cross-ventilation achieved by placing inlets and outlets on opposite sides enhances airflow and dispersion. Consequently, it is recommended to prioritize the structural design of FPRs and implement enhanced safety measures. Additionally, updating the relevant regulations to address these concerns is strongly advised.

Wave pattern effect on the lifting of near-ground dust driven by shock waves after tunnel blasting

The key mechanical problem of dust lifting due to tunnel blasting is the interaction between shock waves and particle phases. Based on compressible flow numerical simulations, a gas–solid two-phase flow model was established to simulate the dust lifting characteristics under two typical wave patterns. The results show that both wave patterns undergo “rolling” + “lifting” during the dust lifting process. The difference is that the dust layer is first pressed and then lifted in the case of spherical waves, while the dust is immediately lifted diagonally upward in the case of plane waves. In the latter case, the dust lifting height and speed are higher. In this paper, theoretical guidance for ventilation and dust removal designs was provided based on the study of dust lifting by shock waves and wave pattern effect under a series of dust physical property parameters and shock wave pressure parameters.

The Predicted Performance of Natural Ventilation Strategies in Islamic Boarding School Design in Magelang

The importance issue in providing comfortable indoor air quality conflicts with the use of energy for mechanical cooling in tropics region such as Indonesia. Natural ventilation is seen as a potential to provide comfort through the change of air within the inside and outside of the space. Natural ventilation becomes a strategy to achieve building resilience towards climate change because it requires no energy consumption. Therefore, this research aims to justify the design of natural ventilation of low-income Islamic Boarding School in Magelang using steady state simulation. The results indicated that among three ventilation strategies simulated in this study, it can be concluded that stack effect is predicted to produce higher air flow rate which results to comfortable predicted observation on adaptive comfort.

Evaluation of the ventilation mode in an ISO class 6 electronic cleanroom by the AHP-entropy weight method

As ISO Class 6 electronic cleanrooms are required to meet stringent environmental control standards during production, an energy-efficient ventilation mode is required to maintain an appropriate thermal and humidity environment and a comfortable workplace. However, the optimum air supply distribution to ensure thermal comfort, energy efficiency and cleanliness is unclear. Therefore, numerical simulations were carried out to determine the workspace satisfaction, energy utilization coefficient satisfaction and contaminant-removal satisfaction with FFU-clean bench coverage(C) ranging from 25% to 100%. We use the AHP-entropy weight method to evaluate four different ventilation modes for different cleanroom design targets, and then select suitable ventilation modes to meet them. The results show that in the core work area, the temperature difference, relative humidity difference and air velocity difference increase with increasing coverage. Furthermore, when the C = 25%, the priority of thermal comfort and cleanliness of employees is satisfied. Moreover, when C = 50%, high energy efficiency of the ventilation system is achieved. The AHP-entropy weight method evaluation system provides a theoretical basis for the selection of cleanroom ventilation design solutions.

Clinical Issues - August 2023.

Respiratory protection against surgical smoke from liver tissue Key words: surgical N95 respirator, surgical smoke, liver tissue, fine and ultrafine particles, particulate matter concentrations. Local exhaust ventilation and surgical smoke safety Key words: local exhaust ventilation (LEV), surgical smoke evacuation, medical-surgical suction, hierarchy of controls, engineering control. Location of endoscopy storage cabinets Key words: endoscope; sterile storage; contamination; environmental conditions; heating, ventilation, and air-conditioning (HVAC) design parameters. Sterility of ultrasound transmission gel Key words: sterile gel, nonsterile gel, multidose container, ultrasound, outbreaks.

Study on Mine Ventilation Resistance Coefficient Inversion Based on Genetic Algorithm

The frictional resistance coefficient of ventilation of a roadway in a coal mine is a very important technical parameter in the design and renovation of mine ventilation. Calculations based on empirical formulae and field tests to calculate the resistance coefficient have limitations. An inversion method to calculate the mine ventilation resistance coefficient by using a few representative data of air flows and node pressures is proposed in this study. The mathematical model of the inversion method is developed based on the principle of least squares. The measured pressure and the calculated pressure deviation along with the measured flow and the calculated flow deviation are considered while defining the objective function, which also includes the node pressure, the air flow, and the ventilation resistance coefficient range constraints. The ventilation resistance coefficient inversion problem was converted to a nonlinear optimisation problem through the development of the model. A genetic algorithm (GA) was adopted to solve the ventilation resistance coefficient inversion problem. The GA was improved to enhance the global and the local search abilities of the algorithm for the ventilation resistance coefficient inversion problem.

CFD model for airflow in a subway station compared to on-site measurements: The challenges of as-built environment

Understanding the contribution of piston effect and train-induced airflow to the ventilation of underground subway stations is essential to design efficient ventilation systems. To this aim, numerical models using computational fluid dynamics (CFD) have been used to recreate existing stations with a number of simplifying assumptions. However, the large variety of station configurations as well as types of sources influencing the airflow makes the generalization to other cases difficult. This study intends to predict numerically the train-induced wind affecting the climate of subway stations perceived on the platforms, and a comparison of these numerical predictions with field tests in an actual station is provided and extensively discussed.A simplified geometry of a station, where the ventilation is mainly realized by the piston effect caused by the train movement, is used to implement a scenario of a train passing through the station, with dynamic meshing techniques, and background wind is included in one configuration. Experimental measurements at 9 locations along the station's platform, repeated in order to improve statistical accuracy and the reproducibility of the results, provide data that can be compared with the corresponding numerical simulation. Numerical to experimental comparison is based on quantification of the peaks due to ingoing and outgoing trains through parameters like peak value, skewness and kurtosis. It is found that the main features of the airflow are well captured by the model, but the differences observed also highlight the challenges of simulating the as-build environment. Several non-dimensional metrics proposed in this paper can be used for comparison with other papers, so that a validated numerical model can be a relevant tool to calculate different velocity scenarios for trains and within different station architectures, supporting the design of ventilation systems to improve the comfort and safety of passengers.

Enhancing solar chimney performance in urban tunnels: Investigating the impact factors through experimental and theoretical model analysis

Efficient and sustainable ventilation in urban tunnels is crucial for combating air pollution and safeguarding human health. This study investigates the design factors impacting solar chimney performance in urban tunnels to optimize ventilation efficiency. Experimental trials analyzed the effects of blockage ratio, chimney height, and solar radiation on temperature distribution and ventilation rate. The results demonstrate that increased chimney height and solar radiation positively influence airflow velocity at the chimney outlet, enhancing ventilation. The temperature rise near absorber is higher than that closed to glazing wall. Temperature distribution within the chimney follows a distinctive horizontal two-piecewise semi-parabolic decay pattern, enabling accurate prediction of temperature profiles along the cavity depth. Novel analytical models predict temperature distribution, airflow velocity, and ventilation rate within the solar chimney system, aiding precise design and optimization. Remarkably, the blockage ratio has limited impact on ventilation rate, allowing for disregarding vehicle blockage effects in solar chimney design for urban tunnels. Matching chimney width to tunnel width and ensuring a relatively high chimney height are emphasized for optimal functionality. The study holds substantial implications for ventilation system design in urban environments, promoting healthier and more sustainable cities.

The impact of heatwaves on human perceived thermal comfort and thermal resilience potential in urban public open spaces

Climate change increases the likelihood of heatwave events, causing human thermal discomfort and even mortality. However, it is not clear to what extent humans with long-term and short-term experience of hot-summer exposure can adapt to thermal comfort in urban public open spaces when both experience their heatwave periods. Therefore, this study aims to investigate outdoor perceived thermal comfort in urban public open spaces during heatwave periods between two groups of people who have long-term and short-term experience of hot-summer exposure. Field surveys were conducted in public squares and parks during the heatwaves in Chongqing, China and Reading, the UK. Chongqing is known as a ‘furnace city’ and people have been living in a hot summer for a long time, while in Reading the summer is warm and people unusually experience the heatwave. The main results show that Chongqing respondents living in a hot climate for a longer period can endure more heat than Reading respondents during the heatwaves, indicating that Chongqing respondents have more thermal resilience. Besides, different behavioural adaptation measures show that people are active participants to choose their thermal preferences, rather than passive recipients of the thermal environments. The research implication contributes that protective measures against heatwaves need to be taken for pedestrians, including more shaded places with efficient ventilation design for sheltering and handy facilities such as drinking fountains and water spray. The research has novelty in deepening the dynamic theory of human thermal comfort and providing empirical evidence of thermal adaptation in extreme-high temperature events.

Maintaining an acceptable indoor air quality of spaces by intentional natural ventilation or intermittent mechanical ventilation with minimum energy use

Ventilation is essential for maintaining good indoor air quality (IAQ). However, many buildings continue to suffer from inadequate ventilation due to a lack of either sufficient natural ventilation or proper operation of mechanical ventilation. During the pandemic of COVID-19, several Chinese guidelines have suggested that the household rooms for isolating infected persons and the classrooms that are not equipped with mechanical ventilation should open the windows for at least 30 min twice a day. This study first investigated whether this way of natural ventilation could ensure an acceptable IAQ. Then, the relationships between ventilation duration, ventilation frequency, and IAQ under different air change rates per hour (ACH) were examined to understand how to optimize ventilation design and operation in an efficient manner. When the ACH is ≥ 6 h−1, an acceptable IAQ can be achieved under the recommended ventilation frequency. An increase in ACH would improve the IAQ and reduce the IAQ difference caused by different CO2 generation rate per unit volume (Gr/V) values. Furthermore, simply increasing single ventilation duration while maintaining constant ventilation frequency is not an effective way to improve IAQ, as the improvement decreases as the ventilation duration is increased. Finally, when total ventilation duration is constant, increasing ventilation frequency can significantly improve the ventilation efficiency and thus IAQ, laying the groundwork for ventilation design that balances IAQ and energy use. The findings provide feasible and economical solutions for ventilation of buildings where conventional mechanical ventilation systems are not affordable.

Design and research of tunnel ventilation system based on STM32

Tunnel ventilation system has always been an important field in tunnel construction, with the main purpose of ensuring air circulation inside the tunnel and ensuring the safety of personnel and equipment inside the tunnel. This article introduces the concept and working principle of tunnel ventilation system. In addition, in terms of operation, this article proposes comprehensive management measures and discusses the measures that should be taken in different situations and emergency response methods.In summary, this paper focuses on the design and operation of tunnel ventilation systems, which has certain reference value for practical applications.

Low-Cost Ventilator With Variable BPM and Oximeter

Abstract: This paper considers a low-cost ventilator that is based on a manual resuscitator bag (Ambu bag) to pump air into the lung of a patient who is physically unable to breathe. To maintain the pressure of oxygen level to improve the patients breathing by regulating the flow of oxygen in the lungs as an intensive therapy. A contradictory motion is used by a ventilator to inflate the lungs by pumping type motion. The ventilator functions while not a human operator because it delivers breaths through the compression of an associate degree orthodox bag-valve mask. It satisfies its energy wants from an electrical motor having a battery power of three to twelve volts DC. Different functions got to be performed for the aim of ventilation i.e. pressure and needed range of breaths per minute are managed by a simple-to-use input board comprising of buttons. Adjust the time duration for inhalation to exhalation ratio. The low-cost ventilator design oxygen sensor and pressure sensor controlled by the microcontroller. This project work on a mechanical method to provide oxygen to the patient. This project gives comfortable treatment to the patient, and monitors and controls the pressure of oxygen level.

Airflow Resistance of Solid-Separated Dairy Waste for Drying and Storage

The resistance of solid-separated solid wastes (SSDWs) to moderate airflow ranging from 0.05 to 0.30 m3/s-m2 was measured at various bed depths and moisture levels. The pressure drop across a loose-fill fixed bed column was observed to increase more rapidly with increasing airflow rates than with increasing bed depths. An increase in the moisture content (10 percentage points) caused a decrease in the pressure drop by an average of 13.2–17.0%, evaluated within a 10–40% moisture content (MC) range. A full-factorial model analysis using standard least squares was used to describe the main effects and interactions of the test parameters in predicting the pressure drop. The Hukill and Ives nonlinear model was able to accurately describe the airflow resistance data of SSDWs at various MCs. Empirical curves describing the SSDW resistance to airflow were developed to aid in the preliminary design of ventilation systems for drying and storage.

Pressure-volume mechanics of inflating and deflating intact whole organ porcine lungs

Pressure-volume curves of the lung are classical measurements of lung function and are impacted by changes in lung structure due to disease or shifts in air-delivery volume or cycling rate. Diseased and preterm infant lungs have been found to show heterogeneous behavior which is highly frequency dependent. This breathing rate dependency has motivated the exploration of multi-frequency oscillatory ventilators to deliver volume oscillation with optimal frequencies for various portions of the lung to provide more uniform air distribution. The design of these advanced ventilators requires the examination of lung function and mechanics, and an improved understanding of the pressure–volume response of the lung. Therefore, to comprehensively analyze whole lung organ mechanics, we investigate six combinations of varying applied volumes and frequencies using ex-vivo porcine specimens and our custom-designed electromechanical breathing apparatus. Lung responses were evaluated through measurements of inflation and deflation slopes, static compliance, peak pressure and volume, as well as hysteresis, energy loss, and pressure relaxation. Generally, we observed that the lungs were stiffer when subjected to faster breathing rates and lower inflation volumes. The lungs exhibited greater inflation volume dependencies compared to frequency dependencies. This study’s reported response of the lung to variations of inflation volume and breathing rate can help the optimization of conventional mechanical ventilators and inform the design of advanced ventilators. Although frequency dependency is found to be minimal in normal porcine lungs, this preliminary study lays a foundation for comparison with pathological lungs, which are known to demonstrate marked rate dependency.

Research on the Design and Construction of Inclined Shafts for Long Mountain Tunnels: A Review

In recent years, inclined shafts have been widely used in long mountain tunnels, but the corresponding design and construction technical specifications need to be improved. By means of literature statistics and actual cases, a comprehensive and systematic review is made on the tunnel profile, lining structure, construction and operation ventilation, construction methods, and machinery of inclined shafts for long mountain tunnels. The results show that: (1) The design of a gentle slope section of an inclined shaft with large longitudinal slope needs to be further improved; (2) When an inclined shaft is only used for ventilation in the operation stage, it is necessary to make full use of the natural wind and eliminate its adverse effects; (3) It is suggested to study the supporting parameters of an inclined shaft in order to realize the standardised design of the supporting parameters; (4) The space of an inclined shaft is narrow, and it has practical demand in improving the automation, intelligence, management, and dispatching level of transport vehicles. In the future, it is an inevitable trend for electric vehicles to replace fuel vehicles. It is necessary to carry out further research on inclined shaft longitudinal slope design, construction and operation ventilation design, and transportation mode.