Ventilation Arrangements Research Articles

Ventilation arrangement evaluation and proactive goaf inertisation for spontaneous combustion and gas explosion management during longwall panel sealing-off process.

When a longwall face approaches the finish-off line, 1month is normally required to relocate the longwall equipment and seal the longwall panel, during which time the goaf gas atmosphere changes and the risk of spontaneous combustion and gas explosion considerably increases. To minimise the occurrence of these hazards, an improved insight into gas flow dynamics within the longwall panel is essential during the panel sealing-off process. Based on mining conditions of an Australian underground coal mine, three-dimensional computational models were developed and calibrated with onsite gas monitoring data, allowing for evaluating ventilation arrangements and understanding methane dispersion in the longwall workings during the six-stage panel sealing-off process with confidence. The simulation results indicate that nitrogen should be injected on the travel road side at a distance of 120m behind the longwall face at a rate of 0.75 m3/s and the rear of the travel road should be tightly sealed at the final sealing-off stage, resulting in oxygen levels lowering than 5% in the longwall workings and producing desired panel sealing-off performance. In addition, gas sensors should be employed and positioned at the appropriate locations to reliably monitor goaf atmosphere change. This study sheds improved insights into evaluating ventilation arrangements and understanding gas flow dynamics during the panel sealing-off process and provides critical knowledge of effective proactive goaf inertisation strategies, thus minimising the risk of spontaneous heating and gas explosion and reducing environmental pollution induced by these hazards.

Predicting the thermal comfort of occupants in an indoor auditorium space with different UFAD ventilation arrangements

An “Underfloor Air Distribution” (UFAD) system employs the open area underneath a raised floor system to drive conditioned air to the supply outlets situated in the floor. To understand a UFAD, think of it as an “upside-down version” of an overhead (OH) system. The idea behind it is to increase both energy efficiency as well as the quality of air in a home. In this paper, an auditorium model has been simulated for analysing the temperature distribution as well as thermal comfort of human occupants provided with 4 different cases of ventilation. The auditorium has two AC inlets ducts, each 2.50 m wide further branched into a number of small diffusers over the auditorium ceiling in order to distribute the inlet air evenly throughout the theatre space. The first case involves an upward ceiling outlet at the front of the theatre near the screen area while the second case has a downward outlet on the floor in the screen area. The third case is similar to the second one with human occupants designed as cuboids on every staircase while for the fourth case, the outlets have been provided under every seat on the staircase. It has been observed in the analysis that the downward outlets in case 2 provide better temperature distribution than the upward outlets of case 1. But the position of outlets below every seat, as in case 4, in the auditorium provides the best thermal comfort for the occupants than all the other cases. Hence, for the “maximum thermal comfort” of the human occupants, the outlets are advised to be installed downward on the floor under every seat.

Strategies to Enhance Contamination Control Performance through Ventilation Improvement in a Biosafety Laboratory Building

A biosafety level (BSL) laboratory is a set of biocontainment preventative measures used to prevent and isolate hazardous biological agents or their accidental release in a laboratory. It is vital to provide a negative-pressurized environment for disease infection control. The experimental equipment layout may affect the personnel’s exposure to infection. However, the equipment layout and exhaust air grilles were in a fixed position in this investigated BSL. Due to retrofitting, the layout arrangement of HEPA as supply air is investigated numerically. Computational Fluid Dynamics (CFD) simulation is conducted to analyze and determine a better design for contamination control. This study proposes three ventilation arrangements as an alternative design, including vertical arrangement, horizontal arrangement, and L-shaped ventilation arrangements (instead of the supply being arranged in a single line). In addition, the airflow distribution, concentration decay, air of age, ventilation, and removal effectiveness are all examined in the study. The numerical simulation results were verified by a field measurement test. The results revealed that the L-shaped ventilation arrangement for supply air diffusers would achieve better ventilation and removal efficiency. The local mean age of air was also identified as the most satisfactory ventilation performance measure, as it shows the level of contaminant control. It also indicated that ventilation could be improved by arranging the supply air layout with less expenditure through CFD-aided simulation in identifying strategies for best practices for the design stage to reduce the running cost at full operation.

FEASIBILITY TEKNIS PEMBANGUNAN KANDANG AYAM CLOSED HOUSE BPU

ABSTRACT
 BPU closed house system cages are closed cages that ensure the safety of livestock in contact with other organisms, 
 with good ventilation arrangements available air and a conducive climate for livestock so as to minimize stress 
 levels. In order to support the planning for the construction of the chicken coop, a geological engineering 
 investigation is needed.
 Technical Feasibility of Closed House Chicken Coop Development at BPU Jenderal Soedirman University aims to 
 identify soil and rock types, analyze soil strength, potential for soil movement, analyze soil physical and mechanical 
 properties as a result of sondir testing, engineering geological drilling at the location of the development plan as 
 well as recommendations for the right type of foundation.
 The results of the investigation obtained that the geomorphology of the planned location was included in the 
 Denudational Ridge/Sloping Hills unit, the slope angle was 8-13%, the height difference was 20 meters. Rock types 
 consist of claystone and sandstone as inserts, interludes. Soil strength is included in the very stiff-stiff category (UCS 
 Classification), but still has a fairly good bearing capacity, there is a lot of hard and dry soil. Hard soil layers from 
 the results of the six CPT test points (sondir) were found to vary at a depth of 5.40-9.60 meters. The results of the 
 N-SPT test at two engineering geological drilling points show the depth of the hard soil layer at intervals of 5-6 
 meters. The results of laboratory tests on the physical and mechanical properties of the soil at a depth of 3 meters 
 resulted in the shear angle numbers: 26.05o (point B1) and 26.79o (point B2); cohesion: 0.2499 kg/cm2 (point B1) 
 and 0.2387 kg/cm2 (point B2), the type of soil that can be interpreted is sandy soil with dense conditions. 
 Recommended depth of foundation to be adapted to the design and analysis of building capacity. The depth of the 
 foundation is 5-6 meters, the result of N-SPT >30 can be constructed with a maximum bearing capacity of 20 tf/m2. 
 The recommended types of foundations that can be proposed are river stone foundations and foot plate foundations.
 Key words : Technical Feasibility, geomorphology, engineering geology,

Study of smoke movement characteristics in tunnel fires in high‐altitude areas

SummaryUnderstanding smoke temperature distributions and transport characteristics is of great importance to control and exhaust thermal‐driven smoke. However, previous studies have focused on this problem in plain areas, whereas ambient pressure decreases as elevation increases. This study investigates the influence of ambient pressure on the hot gas temperature distribution and movement characteristics in a tunnel fire. A series of numerical simulations are carried out in a vehicle tunnel with various heat release rates (HRRs) and ambient pressures. The results show that the maximum temperature and longitudinal temperature distribution under the tunnel ceiling increase with decreasing ambient pressure due to less heat loss caused by lower air density. In addition, the vertical temperatures of the smoke are slightly higher under lower ambient pressure, and this phenomenon makes the smoke spread slightly faster while the smoke layer thickness remains nearly the same under different ambient pressures. The results can provide a reference for tunnel lining design and ventilation arrangements in high‐altitude areas.

Ventilation Optimization for Reduction of Indoor Air Temperature of Main Transformer Room in Urban Indoor Substation by the Variational Method

Urban indoor substations are widely used for electrical power distribution in urban networks. However, they have the problems of heat dissipation and ventilation in main transformer room, which not only influence the thermal behavior of main transformer, but also decrease the lifetime, reliability, and precision of other electronic equipment. In this contribution, we developed a new ventilation optimization method based on the variational method to solve the aforementioned problems. First, we applied the minimum average temperature of indoor air as the optimization objective combined with some constrains to establish a Lagrange function, and employed the variational method to deduce some optimized governing equations that the optimum indoor patterns should meet the minimum indoor air average temperature. Finally, a typical main transformer room model was taken as an example to demonstrate the applications of the newly developed ventilation optimization method. It was concluded that the inflowing fresh air needed to sweep more area of heating walls to take away more heat, and reduce the average temperature of indoor air. Furthermore, based on the optimized air velocity distribution, we redesigned the ventilation arrangements and reduced the indoor average temperature prominently (from 337.44 K to 314.82 K), which can provide the guidance to design the ventilation of main transformer room to improve the reliability of electronic equipment in main transformer room.

Improved dust management at a longwall top coal caving (LTCC) face – A CFD modelling approach

Dust management at longwall faces has always been a concern for mine operators. Recent respirable dust monitoring at a longwall top coal caving (LTCC) face indicated that extremely high dust exposure levels have been experienced at the face. Dust contamination from intake ventilation and the incorrect use of ventilation arrangements (i.e. curtains) at maingate (MG) area were identified as the main cause of this issue. Computational Fluid Dynamics (CFD) modelling studies were therefore conducted to investigate the impact of different ventilation arrangements on the dispersion behaviour of respirable dust at the LTCC face, with a special focus on the airflow patterns and the aerodynamics of fugitive dust at the intersection of MG and face. Field investigation was first carried out to observe the dust issue and obtain essential data for the development and validation of base model. Then parametric studies were conducted to evaluate the effectiveness of two different curtain configurations at MG considering the worst scenario of intake dust contamination to face (dust from travel road and beam stage loader (BSL) discharge point flows towards face) with the shearer cutting into the MG. Model results demonstrate that the occurrence of flow separation and incorrect use of curtains account for the main reasons of high dust exposure level at the intersection of MG and face, especially when the shearer is cutting into the MG. Ventilation arrangements at the MG and face entry are critical to minimise the impact of flow separation on the dust flow patterns at the intersection. Based on model results, new ventilation arrangements at the MG and face entry have been proposed and evaluated through which significant dust mitigation effect can be achieved at face entry, contributing to the overall reduction of dust exposure levels along the face.

Combined Free and Forced Convection in an Enclosure with different Ventilation Arrangements

The objective of this study is to unveil the effect of different ventilation arrangements in a rectangular enclosure subjected to combined free and forced convection. A heat source is flush mounted at the bottom of the enclosure. The equations of mass, momentum and energy conservation are solved using a control-volume-based technique utilized by Ansys Fluent. A pressure based solver and second order upwind scheme is used for the solution purpose. The non-dimensional variables Richardson number (Ri) and Reynolds number (Re) were varied in the course of parametric study. It is observed that increasing the number of ventilation ports complicates the flow structure inside the enclosure and hence a justified provision of exit openings should be provided. The average heat source surface temperatures in the case of three ventilation ports are higher than the case of two ventilation ports beyond the Ri values of 2.0.

Influence of ventilation arrangements on particle removal in industrial cleanrooms with various tool coverage

This paper aims to investigate the influence of comparative ventilation arrangements (wall-return, locally balanced ceiling-return, and four-way ceiling-return) on the airflow distribution and particle fates within cleanrooms of ISO cleanliness class 7 with various tool coverage ratios (0%, 38%, and 60%). Computational fluid dynamics (CFD) was employed to analyze and compare the influence of the three ventilation arrangements on concentrations for particles of various sizes (diameters ranging from 0.01 to 100 μm) in the cleanrooms. The techniques of Eulerian and Lagrangian in CFD were employed for solving the continuous fluid and tracking the particle trajectory, respectively. The outcomes from this study suggested that particle removal rates for the given cleanrooms were significantly affected by the tool coverage ratios, the design of ventilation, and the particle sizes of concerns. In the cases of heavy tool coverage, the locally balanced ceiling-return ventilation arrangements can minimize the need for the relocation of the production lines and layouts of the production tools in cleanrooms, and may provide viable solutions to effective contamination without compromising contamination effectiveness or efficiency.

Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators

Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (7 l s −1 per person) and cold infiltration air (−5 °C) typical of a winter day in Stockholm. Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as much as 7.8 °C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.

Fundamental Factors Affecting Upper-Room Ultraviolet Germicidal Irradiation—Part I. Experimental

The objective of this research was to study the factors that relate to the effectiveness of upper-room ultraviolet germicidal irradiation for inactivating airborne microorganisms. The work was conducted in a room-sized chamber designed and furnished for investigations of this nature. Nebulized Serratia marcescens, Bacillus subtilis spores, and vaccinia virus were used as test aerosols. Most data were collected from steady-state experiments comparing the number of viable organisms in the chamber air remaining with UV lamps turned on to the number with UV lamps turned off, but some decay experiments were conducted to compare the two methods. UV power level had a strong influence but was fully effective only in the presence of air mixing that produced vigorous vertical air currents. A conclusion of the study is that an upper-room ultraviolet installation is a complex system that requires careful integration of UV luminaires, UV power, and room ventilation arrangements.

Modeling and analysis of a fan–pad ventilated floricultural greenhouse

The application of greenhouse technology in the field of floriculture is rapidly expanding worldwide. In India solar radiation is abundant and the climate in the plains are rather hot and dry in summer months while the coastal parts witness a hot and humid climate. For greenhouses in such climates, cooling and ventilation are major factors influencing the production of quality flowers. In the present paper a thermal model of a greenhouse is presented based on fan–pad evaporative cooling. Thermal performance of the greenhouse, as predicted by the model under different climatic conditions is analyzed and compared with a reference study available in the literature. The analysis reveals that a suitable combination of evaporative cooling, shading and ventilation arrangements can effectively maintain the inside microclimate of the greenhouse within permissible limits throughout the year.

Virus diffusion in isolation rooms

In hospitals, the ventilation of isolation rooms operating under closed-door conditions is vital if the spread of viruses and infection is to be contained. Engineering simulation, which employs computational fluid dynamics, provides a convenient means of investigating airflow behaviour in isolation rooms for various ventilation arrangements. A cough model was constructed to permit the numerical simulation of virus diffusion inside an isolation room for different ventilation system configurations. An analysis of the region of droplet fallout and the dilution time of virus diffusion of coughed gas in the isolation room was also performed for each ventilation arrangement. The numerical results presented in this paper indicate that the parallel-directional airflow pattern is the most effective means of controlling flows containing virus droplets. Additionally, staggering the positions of the supply vents at the door end of the room relative to the exhaust vents on the wall behind the bed head provides effective infection control and containment. These results suggest that this particular ventilation arrangement enhances the safety of staff when performing medical treatments within isolation rooms.

A Network Fire Model for the Simulation of Fire Growth and Smoke Spread in Multiple Compartments with Complex Ventilation

There is a need for fire modeling tools capable of rapid simulation of fire growth and smoke spread in multiple compartments with complex ventilation. Currently available tools are not capable of simulation of complex ventilation arrangements in a timely manner. To address this problem, a new fire model called Fire and Smoke SIMulator (FSSIM) has been developed. FSSIM is a network model whose core thermal hydraulic routines are based on MELCOR. FSSIM capabilities include remote ignition, multilayer heat conduction, radiation streaming, arbitrarily complex HVAC systems, detection, suppression, oxygen-limited combustion, and simple control systems.

Validation Of A Network Fire Model Using The Ex-shadwell Submarine Ventilation Doctrine Tests

There is a need for fire modeling tools capable of rapid simulation of fire growth and smoke spread with complex ventilation in multiple compartments. Currently available tools are not capable of either the speed, the simulation of complex ventilation arrangements, and/or the ability to participate as a federate in a simulation environment. To address this, a new fire model was developed called FSSIM (Fire and Smoke SIMulator) [1]. FSSIM is a network model whose core thermal hydraulic routines are based on MELCOR [2]. FSSIM capabilities include remote ignition, multi-layer heat conduction, radiation streaming, HVAC systems, detection, suppression, oxygen and fuel limited combustion, and simple control systems. FSSIM was used to simulate four tests from the ex-Shadwell Submarine Ventilation Doctrine Tests. Excellent results are obtained in predicting the time-dependent temperature, visibility, and velocities.

A Method for Studying Natural Ventilation by Thermal Effects in a Tunnel Greenhouse using Laboratory-Scale Models

A laboratory method for the physical simulation of natural ventilation by thermal effects in greenhouses is presented. Scale models of a tunnel greenhouse were constructed and immersed in a water tank. A solution of salty water and black dye was injected to produce density differences that simulated the buoyancy flux due to the heating of the greenhouse air. Flow was visualized using a video camera and images were processed in order to relate pixel intensities and density increments. Scaling laws allowed the calculation of the temperature increments associated with relative density increments for each experiment.Experiments with Reynolds numbers Re ranging from 101 to 1350 were carried out in order to estimate the minimum Re necessary to neglect viscosity effects. For the type of greenhouse under study, this minimum value of Re was determined to be close to 900.The increments of temperature obtained from laboratory experiments were about 25% lower than those obtained by the theoretical model developed by Bruce. The method could be a useful tool for testing ventilation arrangements in greenhouse structures and for comparing results with those obtained by calculation based on models.

Using numerical simulation to predict ventilation efficiency in a model room

A computational fluid dynamics (CFD) code is used to simulate the air currents and the contaminant decay inside a small scale model room with forced ventilation through a simple supply and return. The numerical results are validated with flow visualization experiments and local clearance rate measurements by laser extinction. The comparisons show excellent agreement on the inlet side of the room and fair agreement on the outlet side. Based on the concept of local exponential tracer decay and mixing factor ( m), an arithmetic average of m is proposed as a measure of overall air ventilation efficiency η m. The proposed definition has practical benefit in numerical simulation because it reduces computational time without sacrificing the concept of air ventilation effectiveness. Examples of application are demonstrated by eviluating η m for different room configurations and ventilation arrangements. The calculated η m correlate well with the time required for evacuating the contaminants in different room configurations. The results show that, for the room geometry studied, a ventilation system performs better when the inlet and the outlet are perpendicular to each other than when they are parallel to each other, and that partitions in the room can have a significant influence on ventilation performance.

The Resistance to Air Flow of Farm Building Ventilation Components

The static air pressure change (pressure drop) across a variety of ventilation components used in agricultural buildings was measured. Twenty-one ventilated wall claddings and ten roof ventilation arrangements were tested. The pressure drops across these items were measured at air approach speeds between 0·05 and 1·7 m/s. Despite the low Reynolds number of the air flow involved, pressure drops varied with the square of air velocity. This allows the pressure drop characteristics of the items measured to be described by a pressure loss coefficient, k. The values of k for the various items tested are given. The use of k, which simplifies the calculation of pressure losses in complex ventilation paths, is described.

Comfort Temperatures in Classrooms

Low-mass, light structures, such as many school designs of recent times, can become uncomfortably warm in hot weather, and correction by mechanical air conditioning can be costly. The problem was studied some time ago by the Hungarian Institute for Building Science by means of computer calculations and model tests, described here. The results show the importance of careful design and of orientation, and the potential for adiabatic control, namely where heat entering the system is balanced by ventilation. The results of different directional ventilation arrangements are outlined.

BUOYANCY-AFFECTED FLOWS IN VENTILATED ROOMS

Calculations of velocity and temperature distributions in rooms with ventilation arrangements are reported. The method involves the solution, in finite-difference form, of two-dimensional equations for the conservation of mass, momentum, energy, turbulence energy, and dissipation rate, with algebraic expressions for the turbulent viscosity and heat diffusivity. The results are shown to be in reasonable agreement with available experimental data and the method is then applied to provide additional information useful for design purposes.