Capture Efficiency of Local Exhaust Ventilation Systems

Temperate buildings are comfortable, safer and more productive places to work. Ensuring that extremes of cold and heat, and airborne diseases are mitigated is through effective design, function and management of ventilation systems. This book addresses the basics of ventilation systems and their use in building-based workplaces and how to ensure they are managed successfully. This book provides comprehensive technical information regarding the design and implementation of dilution and local exhaust ventilation systems to ensure safe and productive workplaces. It presents a simple and readable summary of how to design, install, and operate industrial ventilation systems, all highlighted through illustrations and tables. This title is written to international standards on the design of dilution and local exhaust ventilation systems, including ASHRAE and ACGIH standards. Design of Workplace Dilution and Local Ventilation Systems is an ideal reference for safety engineers, designers, specialists, engineers, architects, and contractors tasked with ventilation systems. It is also a useful reference for undergraduate and graduate students to master the complex fundamentals of designing dilution and local exhaust ventilation systems.

The vortex ventilator (VV) is a new concept of a local exhaust ventilation system that uses a vortex flow to improve the directional capture ability and thus overcomes the critical defects of the general local exhaust ventilation (LEV) system. The LEV has a rapid decrease of the capture velocity with distance from the exhaust inlet, resulting in a very poor capture efficiency when contaminants are generated far away from the exhaust inlet. In this study, the capture characteristics of the VV are evaluated with respect to the capture efficiency as well as the capture velocity. Three-dimensional computational fluid dynamics simulations are performed together with experiments using the tracer gas method with SF6. Compared with simple suction, the VV gives more than nine times as large a capture velocity and thus has a capture efficiency of higher than 70%. The larger capture velocity and the higher capture efficiency of the VV guarantee a more flexible layout of the equipment in the working area.

ВПЛИВ ОБРОБІТКУ ҐРУНТУ

This paper presents the results of a series of recent studies to investigate the improved optimal design and planning of the main ventilation systems of complex multi-level mine networks using a genetic algorithm (GA) routine. It is concluded that the method may be successfully used to investigate the benefits offered by alternative ventilation configurations and to determine the most practical and cost-effective ventilation system during the various mine planning stages (short-, medium- and long-term). In particular, the optimum number, location and duties of booster fans, and size and location of regulators may be evaluated and selected. The objective of the final ventilation design is to identify the ventilation system that operates in both a safe and energy-efficient manner. The method has been refined to include the selection of practical fan units that match the optimal fan operating duties determined by the GA routine. The paper also reviews general optimisation strategies that may be employed to enhance and maintain the performance of mine ventilation systems.

The design of tunnel ventilation system for a long vehicular tunnel

The ventilation performance of air shafts is important to the air quality of subway tunnels, but there is no unified evaluation index of ventilation performance. In this paper, the air shafts at different locations in subway tunnels were taken as research objects, and the wind speed as well as the particulate matter concentration of each air shaft was tested. The effective ventilation volume and PM2.5 discharge efficiency of the air shafts were defined to evaluate the ventilation performance. It was found that on average, during the subway train service, the station air shaft on the train-arriving side can discharge 2050 m3 of dirty air in the tunnels and inhale 218 m3 of fresh air from the outside environment, while the station air shaft on the train-leaving side can absorb 2430 m3 of fresh air but can hardly effectively discharge dirty air; meanwhile, the middle air shaft can not only effectively exhaust 1519 m3 of dirty air but can also absorb 7572 m3 of fresh air. In addition, the middle air shaft has better ventilation performance if its inner opening is set on the top rather than on the side of the tunnel. The PM2.5 discharge efficiency of the station air shaft on the train-arriving side is 52.0~62.8%, higher than that of the middle air shaft of which the value is 26.8~40.7%. This research can provide guidance for ventilation performance evaluation of subway air shafts and provide a reference for subway tunnel air shaft location design.

Natural ventilation is an energy saving system for the building to ensure occupant’s physical comfort. Wind-driven natural (WDN) and buoyancy-driven natural (BDN) ventilation systems for a one story single room building were investigated. The basic flow field of WDN ventilation system of the scaled model was analyzed by flow visualization, Particle Image Velocimetry (PIV), and Computational Fluid Dynamics (CFD) techniques for three different cross ventilation cases based on the number and location of windows. The satisfactory comparisons between the results obtained from the computation and three experiments were aimed to provide an effective guideline to the numerous CFD users for the validation of future numerical approaches. A novel and intelligent numerical technique was proposed and applied to provide the insight of the mixing level quantification in WDN ventilation system. In each case of WDN ventilation system, the location of window in lateral and vertical directions, wind speed, and wind angle were varied to check the sensitivity of the ventilation performance to the changed design and conditions. The precision of the numerical methodology for BDN ventilation system was established by comparing the computational results with two reputed experimental results from the literature satisfactorily. The governing equations subjected to the corresponding boundary conditions were solved using the package software, ANSYS CFX 12.0 in all computations. The power and the inclination angle of the heating passage (HP) were varied to check the sensitivity of the ventilation performance to those factors. Three dimensionality, turbulence and mixing level of the indoor fluid were visualized in WDN ventilation systems. The overall performance was significantly affected by the particular design of the cross ventilation system. It was found that higher volumetric flow rate didn’t always ensure higher mixing level or vice versa. It also emphasized the necessity of three-dimensional (3D) approach to predict the indoor air movement correctly in studying natural ventilation system. A better location for the windows in each case was proposed. The ventilation purpose was served quite well even if the wind angle was changed in a moderate range from the original design. It was found that ventilation performance was significantly influenced by the lateral and the vertical positions of window and the wall porosity of the building. Furthermore, the velocity components, surface pressure, ventilation rate, ventilation time, mixing level, Air Change per Hour (ACH), ventilation efficiency etc. in each case were investigated and compared extensively with those in other cases of WDN ventilation system. The BDN ventilation system was found capable to serve the ventilation purpose whereas the building only contributed to the increment of the friction force. A proportional relation between the flow rate and the power was obtained. The ventilation rate was found the maximum when HP was attached to the building at 45°. The relations among Ra, Nu, Re and Pr obtained from the present BDN ventilation system were reported.

Experimental evaluation of thermal comfort, ventilation performance indices and exposure to airborne contaminant in an airborne infection isolation room equipped with a displacement air distribution system

Impact of displacement ventilation and underfloor air distribution systems on concentrations of indoor particle in different seasons

Experimental study on the performance of hybrid ventilation system combining forced longitudinal flow and shaft natural ventilation in tunnels

The ventilation system is the basis to control the hazards in coal mine laneway. High reliability ventilation system can continuously convey fresh air into laneway , dilute the noxious gas, reduce disaster and ensure the mining productivity safe and effective. As we know that, many noxious gases in the coal mine laneway are compossible and their flowing states are complicated. In order to acquire the distribution characteristics of fluid movement, and evaluate the performance of ventilation system, a geometry and physical model of laneway was established in this paper with Fluent software, and the physical field of fluid such as velocity field, density field and temperature field were built and analyzed. A standard model was introduced to simulate the laneway fluid movement according to the turbulent kinetic energy equation and turbulent dissipation rate equation. The case study results showed that the CFD approach can effectively observe the performance of ventilation system and evaluate the safety and reliability of ventilation environment.

The removal of toxic gases leaking during excavation in infrastructure projects is crucial for both human health and environmental protection. In this process, Computational Fluid Dynamics (CFD) simulations are highly valuable for modeling and analyzing complex physical processes associated with the transport and dispersion of gases. During infrastructure projects in geothermal regions, various gases may leak from underground sources. These gases may include toxic and/or flammable substances such as hydrogen sulfide (H₂S), carbon dioxide (CO₂), and methane (CH₄). Designing an effective ventilation system is essential for the removal of toxic gases through ventilation. CFD simulations can be utilized to evaluate the design and performance of ventilation systems. Modeling gas leaks from sources encountered during excavation using CFD simulations can help understand how gases move throughout infrastructure projects and their environmental impacts. CFD simulations can assist in optimizing factors such as the placement of ventilation systems, duct design, air flow rates, and filtration efficiency. This optimization ensures the effective removal of toxic gases and minimizes environmental impacts. CFD simulations can also be used to assess the efficiency and safety of ventilation systems designed for the mitigation of toxic gases. Additionally, simulating the operation of ventilation systems during potential emergency situations can help in evaluating associated risks.

Mining is a continuous process of continuous change and development, and mine ventilation systems are an important part of the process. Mining is a continuous process of continuous change and development, and mine ventilation systems are an important part of the process. Additionally, the mining process is constantly evolving and innovating. Despite the improvements in technology, there are still some problems with the current mine ventilation system, including its hardware structure and design control. It is necessary to improve and solve these problems. An approximate optimization algorithm is used to improve the ventilation pipes and air network in the mine ventilation system to solve the problem of the unreasonable ventilation system design. It is also designed to meet the corresponding requirements in terms of return air section resistance and air supply route resistance. Efforts are made to improve the mine ventilation system's performance, and the system's main air supply branches are optimized to increase their efficiency.

A numerical study on the performance of a hybrid ventilation and power generation system

Cost reduction through improvement in energy efficiency is a determining factor for the optimization of operational processes and the economic sustainability of organizations. One opportunity for achieving significant levels is by designing energy-efficient heating, ventilation, and air conditioning systems for new industrial facilities. Cleanrooms, used in biopharmaceutical companies, require high air change rates to maintain cleanliness, which are particularly energy intensive. This paper analyzed data collected from third-party sources, demonstrating a method used in a biopharmaceutical facility in Ireland. The study’s objective was to compute the parameters related to energy efficiency before and after fresh air volume control implementation, aiming to ascertain the effectiveness of this approach in optimizing energy consumption and ventilation performance. This case study analyzed 185 cleanrooms of different sizes and classifications; it was observed that all rooms exceeded the recommended air change per hour. The data indicated that rooms with higher volumes had greater energy waste, underscoring the importance of optimizing airflow management in large cleanroom environments. The implementation of fresh air volume control showed a reduction of 8.87% in fan energy consumption, equivalent to a decrease of 46,666 units of air change per hour annually. This decrease in units was accompanied by a substantial reduction in fan waste, amounting to 203,399.1 kWh, and saving more than €49,055.8 per year using pressure gradient control strategies in the ventilation system. Overall, the present work provides insights into improving energy efficiency in the biopharmaceutical industry and highlights the economic and energy-saving benefits associated with implementing the proposed method. Furthermore, it offers a practical solution to reduce operational costs and environmental impact while maintaining stringent cleanliness standards, essential for cleanroom operations.