G. Berckman, U.S. Army, Fort George G. Meade, MD; J. Forsythe, Battelle, Aberdeen, MD.
We evaluated potential health hazards associated with industrial electroplating operations at an Army Maintenance Depot. The subject electroplating shop is a newly designed, cyanide-free facility capable of fulfilling many mission requirements from stainless steel to copper plating. Of the 153 open surface tanks, 63 contain potentially hazardous materials and are ventilated using push-pull technology. Push-pull ventilation systems operate by forcing air through small nozzles or holes in a manifold at one end of an open surface tank, entraining contaminants generated, and then using slotted exhaust collection hoods on the other end of the tank. Evaluations were based on personal exposures of electroplaters (N=17), ventilation measurements, and work practice observations. These indicated that although control measures were adequate to reduce airborne breathing zone levels of the measured contaminants to within regulatory limits, cadmium, chromic acid, hydrochloric acid, and sulfuric acid general area sample analyses suggested that the potential to exceed these standards exists. Personal protective equipment was recommended as an interim measure for controlling exposures while the engineering controls are being reassessed and/or upgraded.
L. Tseng, R. Huang, C. Chen, H. Chen, National Taiwan University, Taipei, Taiwan Republic of China; C. Chang, Council of Labor Affairs, Taipei, Taiwan Republic of China.
Studies on flow structures and tracer gas leakage of the chemical fume hood are conducted experimentally to unveil the correlation between the global/local flow patterns and the hood containment. A full-size, transparent, commercial grade chemical fume hood is constructed for experimental study. The flow characteristics and the contaminant leakage properties are diagnosed by using the laser-light-sheet-assisted smoke flow visualization method and the SF6 tracer gas concentration measurement, respectively. The results show that the smoke issued from the smoke ejector could leak or disperse out of the sash opening most drastically around several critical regions due to some inherent flow physics. These critical regions include the doorsill, the side poles, and the wake behind the manikin. From the point of view of aerodynamics, flow recirculation areas would inevitably be induced due to the geometric arrangement of the fume hood because the non-streamwise design could induce significant flow separation and subsequently lead to flow recirculation. From the flow visualization results, these local flow recirculations obviously bring large amount of in-hood smoke out to the atmosphere through the mechanism of turbulent dispersion. Examination of contaminant leakage by employing the tracer-gas (SF6) concentration measurement of the ANSI/ASHRAE 110-1995 code shows low leakage around the breath area of the manikin because the measurements are taken around the area far from the critical regions of leakage. However, more rigorous tests by using the Invent/UK method and the prEN14175-3 standard all show serious contaminant leakage around the doorsill, side poles, and the manikin wake. Particularly, the robustness tests by simulating the moment of an object or a draft current across the sash opening show very low resistance to the environmental interference. These results indicate that the point-by-point or region-by-region measurement is a necessary method for detection of the fume hood leakage.
J. Kosner, V. Krejci, M. Kaplan, T. Peciva, Brno University of Technology, Brno, Czech Republic.
The article focuses on a radial jet investigation. The radial jet is one of the most important features of a reinforced exhaust system known as the Aaberg exhaust hood. In order to describe a radial jet flow pattern, measurements of radial jet characteristics, such as velocity decay, spreading rate, and turbulence intensity profiles across the jet are needed. An experimental setup has been built that allows the measurements to be taken under various geometrical (jet width and orifice diameter) and initial conditions (turbulence intensity, air speed, and temperature at the inlet). The setup consists of an air terminal that creates the radial jet, a ductwork with a fan unit, and a heat exchanger. The basic dimensions of the air terminal are 200 mm in diameter and the width of the terminal nozzle is 4 mm; both of them are adjustable. The flow rate can be varied from 50 to 1200 m3/h. Data acquisition system is based on a computer and it enables the storage and evaluation of data from all measuring devices and sensors in real time. For the basic arrangement, a set of measurements were undertaken and results of that were compared with available literature. The radial jet was also simulated numerically by means of a commercial CFD code with the aim of using this tool for further development and optimisation of radial jet reinforced exhaust system. Comparison of the results, both experimental and numerical, with available expressions and data for velocity decay shows as much as 30% discrepancy.
I. Fukuhara, K. Tsuji, Osaka Prefecture University, Sakai, Japan.
A disturbance of flow greatly influences a diffusion of contaminants in a push-pull flow. The diffusion can be restrained by decreasing the disturbance of the push-pull flow. We showed in the previous paper that it was possible to make the exhaust flow rate decrease by decreasing the disturbance of the flow. Decreasing the disturbance of the flow requires a lessening of turbulent intensity of the flow at the supply opening, and raising the uniformity of the supply flow. Then, sizes of supply and exhaust openings are considered as factors that influence the push-pull flow. In this report, when supply flow rate in the push-pull ventilation system is equal to exhaust one, and sizes of supply and exhaust opening are changed, respectively, we investigated the capture efficiency of contaminants in the push-pull ventilation systems.
L. Ricciardi, C. Prevost, L. Bouilioux, J. Lacan, R. Sestier-Carlin, IRSN, Gif-sur-Yvette, France.
Within the framework of Internal Emergency Plans analysis of nuclear facilities, IRSN has to assess accidental scenarios, as well as their consequences in environment. Some of these plants involve the risk of accidental release of uranium hexafluoride (UF6), heavy gas (density equal to 12), whose behavior is badly known. Assessment of such a gas release consequences first requires the knowledge of the space-time gas concentration in the ventilated room where the release occurs. An experimental and numerical study has thus been carried out at IRSN in order to characterize heavy gas dispersion in ventilated rooms. This study relies on vertical injection experiments of an heavy tracer gas (SF6, density equal to 6) inside two ventilated rooms of 36 m3 and 1,500 m3 volume. About 20 experimental configurations have been performed while varying the injection conditions (diameter, speed and time) and the room ventilation conditions (air exchange rate, continuous/discontinuous mode). The time evolution of SF6 concentrations has been measured in various locations inside each room. A stratification is highlighted in most cases, due to an accumulation of SF6 in the lower part of the room. These experiments have been simulated thereafter using the computational fluid dynamics (CFD) code CFX-5, in order to contribute to the interpretation of experimental results and to qualify this code for future simulations of UF6 dispersion. We propose to present a summary of the numerical results, compared with the experimental ones, by illustrating the influence of the various studied parameters. The levels of concentrations are overall in good agreement with experience, especially during the injection phase. This comparison between simulation and experience is all the more satisfactory as flow velocities are high in each ventilated room. However, complementary studies remain to be carried out in order to explain some phenomena, such as sudden concentration decreases.
Y. Kubota, K. Kimura, KOKEN-LTD, Hanno,Saitama, Japan; Y. Fujishiro, KOKEN-LTD,
Chiyodau-ku,Tokyo, Japan;
K. Kamifukumoto, T. Iwasaki, KOKEN-LTD, Chiyoda-ku,Tokyo, Japan; H. Sasaki,
Tokyo Women’s Medical University, Shinjuku-ku,Tokyo, Japan.
The Ministry of Health, Labour and Welfare of Japan formulated a guideline to maintain formaldehyde level of special purpose work areas that use formaldehyde at 0.25 ppm or lower. In dissection laboratories of medical schools, students may be exposed to highly concentrated formaldehyde. We developed two types of a push-pull ventilation system and successfully lowered the formaldehyde exposure level. One of these two types is a horizontal-flowing system and the other is a downward-flowing system. For each type, optimum air volume is determined based on the results of CFD analysis and airflow visualization experiment. We found that the horizontal-flowing system requires 5.4 m3/min or more of push airflow and 12 m3/min or more of pull airflow. That push airflow of the downward-flowing system hits the dissection table and then flows near-horizontally. Based on these findings, we were able to determine optimum positions of pull hoods. We also found that push airflow is 11.5 m3/min and pull airflow is approximately 40 m3/min when pull hoods are in the optimum position. Furthermore, we embedded a high-performance filter that is intended exclusively for formaldehyde protection in each pull hood in order to enable indoor ventilation. Next, we examined the effect of the horizontal-flowing push-pull ventilation system in an actual laboratory. Measurement was carried out using DNPH-HPLC method. While the system was turned off, formaldehyde level in the respiration area (1,200 mm from floor surface) was 0.18– 0.31 ppm, which was higher than the level specified by the guideline by the Ministry of Health, Labour and Welfare. After the system was turned on, the formaldehyde level dropped to 0.04–0.08 ppm, which was well below the level specified by the guideline. Based on the results of this study, we found that protection against formaldehyde exposure in dissection laboratories, which has been considered difficult, can be effectively improved by use of the push-pull ventilation system.
S. Soares, L. Ricciardi, IRSN, Gif sur Yvette, France.
In order to achieve a satisfactory level of hygiene in industrial workplaces and to assess pollutant transfers, it is necessary to control the airflow distribution. Two different approaches are presented for evaluating air distribution in a real ventilated room of 2,300 m3 volume: the first one uses Computational Fluid Dynamics tools (CFX, FLOVENT); these codes are based on the resolution of Navier-stokes equations and are widely used in many fields but suffer from a lack of qualification, especially in the field of ventilated rooms. The second approach is an intermediate one between predictive numerical simulation and experimental determination of aerodynamic parameter; it is the systemic approach. The main features of the IDTS code developed and based on the principles of the systemic approach are presented. A model is built from a combination of elementary systems representing basic flows as piston, mixing flow, recirculation, short circuiting; each elementary system is characterized by specific parameters, such as the residence time and the volume of the unitary system. The adjustment of the model is derived from the comparison of the responses to a signal injected into the model with a tracer emission realized at the room inlet. This response depends on the internal fluid flow patterns and is called the residence time distribution (RTD). The difficulty is in finding the most representative adjustment and the associated parameters. The experimental results obtained on the ventilated enclosure (particularly the RTD curve) are compared with the CFD simulations and the IDTS identification, and are overall in good agreement. Finally, the objective of this presentation is to increase public awareness of the potentialities of both approaches but also of their limits, especially about the gaseous transfers in a ventilated indoor space.
T. Oshima, Y. Kondo, Y. Abe, Musashi Institute of Technology, Tokyo, Japan; Y. Aizawa, Tokyo Gas Co., Ltd, Tokyo, Japan.
The indoor environment in home kitchens, such as temperature, humidity and air quality, is influenced by the capture efficiency of an exhaust hood. When thermal plume over a cooking range is captured well by a hood, indoor environment can be kept in comfortable condition. However, in actual home kitchens, there is air disturbance due to air supply from the ventilation system or air-conditioning system, and a part of thermal plume flows into living areas. Therefore, a ventilation system should be designed appropriately to keep capture efficiency of an exhaust hood high. In this study, the relationship between position of air supply and indoor environment is studied by experiments and CFD simulation. Four typical air supplies at different positions are supposed in the experiment, and indoor environment is examined by the flow visualization and measurement of distributions of temperature and humidity. CFD simulated results show that the position of air supply influences the capture efficiency of heat from gas range by the exhaust hood, which then influences the indoor air temperature. The direct capture efficiency of the exhaust hood is evaluated on the basis of the contaminant distribution calculated by the CFD simulations, and an appropriate air supply position is examined in this study. The airflow patterns given by the CFD simulations are also compared with the flow visualization observed in the experiments.
Y. Abe, Y. Kondo, Y. Nagasawa, Musashi Institute of Technology, Tokyo, Japan.
Problems in indoor air quality (IAQ) are considered to be the cause of “Sick House Syndrome” in Japan. As such, the building standard was revised to improve IAQ in rooms in Japan in 2003. It is very important to ventilate indoor spaces efficiently to reduce energy and CO2 consumption. Ventilation efficiency indexes have been proposed as a means to evaluate the efficiency of ventilation systems, and these indexes have been taken into account in ventilation design. This paper proposes the effective ventilated volume as a ventilation efficiency index and gives a definition for the equation of the effective ventilated volume based on the volume integral with a weighting function. The meaning of the effective ventilated volume depends on the selected weighting function; therefore, different forms of the weighting function are examined. Three functions are chosen to express the effective ventilated volume for a volume in a well-ventilated zone compared with that in a perfect mixing condition. The weighting functions are described with the local age of air, and the volume of the zone is either neglected or reduced in evaluating the effective ventilated volume when the local age of air is larger than the nominal time constant, i.e., the age of air under the perfect mixing condition. 2-D case studies on the effective ventilated volume based on computation fluid dynamics (CFD) are demonstrated.
E. Janotkova, M. Pavelek, Brno University of Technology, Brno, Czech Republic.
The article presents new trends in automobile air conditioning and their comparison. The attention is focused on a refrigeration and air circuit of the air-conditioning equipment, as well as the control system. The paper includes an analysis of a refrigeration system operating with R 134a, which is widely used in automobile air-conditioning systems. The emphasis is placed on the analysis of a perspective transcritical cycle with CO2 refrigerant, which seems to be a suitable candidate to replace R 134a in refrigeration equipment of automobile air-conditioning systems. The article also deals with the design of refrigeration system components operating with CO2, i.e., a compressor, gas cooler, evaporator, and an internal heat exchanger. These devices require a special design with regard to operating pressures in the refrigeration system. As far as control is concerned, attention is paid to physiologically controlled air conditioning. In order to reach an optimum microclimate, thermal comfort sensors or various sets of sensors are utilized to measure, constantly during the run, temperatures, velocities, and humidity of air, as well as a heat flow from solar radiation. Based on the obtained data, the control system evaluates optimum temperatures and adjusts them automatically. In addition, the control uses different sensors of outdoor air pollution and controls switching of outdoor and indoor air circulation according to the measured concentrations. The article also concerns zone air-conditioning systems enabling air conditioning in more zones. A perspective four zones air-conditioning system can ensure an optimum microclimate for every passenger in the automobile.
M. Pavelek, V. Krejci, M. Jicha, Brno University of Technology, Brno, Czech Republic.
The paper deals with CFD simulations of a reinforced exhaust system (the Aaberg exhaust hood in particular). The reinforced suction effect is achieved by means of radial jet release. The radial jet deforms the flow pattern in front of the hood to a directional flow pattern. Unfortunately, the presence of an obstacle, such as a welding bench, can lead to a defective operation of the hood. A number of CFD simulations have been undertaken in order to assess the effect of the obstacle size, its distance to the hood, and the hood declination from the normal of the obstacle surface, on the flow pattern and consequently capture efficiency of the hood. Capture efficiency of selected cases was evaluated. For the purpose of capture efficiency evaluation, a heat source was defined within the model that imitated a metal arc welding process and introduced similar heat input into the domain altogether with a release of a passive scalar. The scalar concentration was then evaluated at the hood opening, thus capture efficiency could be calculated. The results of simulations indicate that the hood operation depends on the spatial arrangement of the hood and the obstacle. The best performance was achieved when the hood axis was aligned with the obstacle surface normal or the misalignment was small. Greater misalignment can be tolerated when the obstacle size is smaller than the hood-to-obstacle distance only.
L. Malasek, E. Janotkova, Brno University of Technology, Brno, Czech Republic.
The contribution deals with research on capture efficiency of a slot reinforced exhaust system. A designed exhaust hood can work as traditional exhaust system or as reinforced exhaust system (well known as REEXS). Reinforced exhaust system is based on combination of exhaust air and radial supply air, which increases a size of an exhaust area. This exhaust hood was built into measuring setup that includes computer measurements of pressures, temperatures, and concentrations. Designed measuring set-up allows traditional exhausting or reinforced mode of investigated exhaust hood. A tracer gas method was used for capture efficiency measurement of the system. This method is based on supplying of tracer gas to the space in front of the exhaust hood, which is captured by exhaust hood. We can measure concentrations of captured tracer gas in the exhaust air by multi gas monitor, which is connected to the exhaust part of the entire measuring setup. We can calculate capture efficiency of the selected system (traditional or reinforced) from these concentrations. Information about shape and range of efficiency areas are very important for setting up the exhaust hood against the pollution source if we know behavior of the pollution. This contribution also presents a comparison of capture efficiencies measured with different working modes of slot exhaust hood with capture efficiencies of reinforced circular exhaust system at the same volume flow rates of exhaust air and the same values of the ratio of momentum flows of supply and exhaust air.
A. Cutz, B. Hailu, S. Yoon, T. Harris Environmental Management Inc., Toronto, ON, Canada.
The purpose of this paper is to get a better understanding of the potential health impacts associated with exposure to indoor air contaminants found in commercial buildings in Toronto, Canada. The growing proliferation of chemical pollutants in consumer and commercial products, and the tendency toward airtight buildings and reduced ventilation to save energy have caused indoor air quality problems to occur in many modern buildings. U.S. EPA studies on human exposures indicate that indoor air pollutants may be 2-5 times, and occasionally more than 100 times higher than outdoors. Through a review of current literature, the strength of the association between the identified contaminants and health effects will be examined, and any conditions that lead to high exposures will be noted. One of the emerging indoor air quality sources of pollution is the contribution of scented products such as perfumes and air-fresheners. Data from the U.S. EPA “Building Assessment Survey and Evaluation” (BASE) study will be compared with parameters measured during basic indoor air quality assessments conducted across the Greater Toronto Area. Correlation between outdoor environmental conditions (weather conditions, air pollution) and indoor environment will be explored in view of the Proposed New ASHRAE Standard 169, “Weather Data for Building Design Standards. Mitigation” measures used to improve indoor air quality from ventilation perspective including special purpose air filters will be discussed. It is expected that property managers and building operators as well as public health policy makers would have a better understanding of indoor air quality issues and practices aimed at securing a more comfortable indoor environment.
S. Ogita, H. Yoshino, TONETS Corporation, Ichikawa-city, Japan; Y. Kondo, S. Adachi, Musashi Institute of Technology, Tokyo, Japan.
In commercial kitchens, it is very important to remove contaminants and heat that are generated from cooking to keep air quality healthy in occupied zones. Displacement ventilation system is applied as an effective method in such conditions, therefore it has been widely used in Europe recently. However, the area of floor and walls is small in Japanese commercial kitchens, so it is difficult to apply this system. If the displacement ventilation system with supply opening installed in a ceiling is effective, it can be applied to Japanese commercial kitchens. In this paper, two types of displacement ventilation were investigated by measurements and CFD simulations: (1) Case A where a supply opening is installed in a wall, and (2) Case B where a supply opening is installed in the ceiling. The results of CFD simulation were compared to the experimental ones and ventilation efficiency was evaluated by two indexes. The first index was Direct Capture Efficiency (hereafter DCE) and second one was scale for Ventilation Efficiency 3 (hereafter SVE3). The application of DCE was shown in this paper. DCE is defined as how much contaminant is captured directly by a local exhaust device. DCE can be calculated from airflow and concentration distributions obtained by CFD simulation. The capture efficiency is always unity in a closed space with only one exhaust opening. In such situations, the performance of the local ventilation device cannot be evaluated by the usual capture efficiency. On the other hand, DCE can evaluate the performance of the exhaust device in such situations even in the case where the exhaust airflow is disturbed by other flow in an actual room, e.g., airflow supplied from an air-conditioning system.
H. Yoshino, S. Ogita, TONETS Corporation, Ichikawa-city, Japan; Y. Kondo, S. Adachi, Musashi Institute of Technology, Tokyo, Japan.
In the previous paper, two types of displacement ventilation were investigated using experiments and computational fluid dynamics (CFD) simulation. The first one was general displacement ventilation in which an air diffuser was installed on a wall. The second one was a new type of displacement ventilation in which an air diffuser was installed on the ceiling. The result of examination, good agreement between the experiment, and the CFD was obtained. In this paper, two types of ventilation system are compared by experiments and CFD. The first one is a conventional HVAC systems in which pan-type and adjustable bar grill-type air diffuser are installed on the ceiling. The second one is a new type of displacement ventilation in which an air diffuser is mounted in the ceiling. The CFD simulations were carried out with the same conditions as the experiments. In the CFD simulation, several ventilation efficiency indexes are used, i.e., Direct Capture Efficiency (hereafter DCE, Ogita et al., VENT 2006) and Scale for Ventilation Efficiency 3 (hereafter SVE3). The following results have been obtained: (1) there was no remarkable difference between the temperature distribution in the experiment and CFD, (2) the SVE3 in the occupied zone was almost same in two cases, and (3) in the displacement ventilation system, the thermal plumes over cooking ranges were not disturbed, and the DCE was larger than that in the conventional HVAC system.
S. Nobile, C. Cigna, S. Francese, M. Patrucco, Politecnico di Torino DITAG, Torino, Italy.
Where dust exhaust systems are considered, both design and effectiveness evaluation problems can arise; the latter requiring user friendly techniques regarding maintenance procedures’ requirements in industrial workplaces and auditing by public administration inspectors. The dimensioning of the ducts, fans, and collectors does not usually involve special difficulties, using a redundant flow rate that optimize pressure losses and precludes dust sedimentation, whereas the definition of the necessary hood flow rate is quite critical. In fact, the input data to be considered (on which lays the capture efficiency) are the particle capture velocity directly connected with the particle source emission characteristics, and the shape, cross area, and position of the hood. The capture velocity is strictly bound to the pollutant particles aerodynamic behavior, and, usually, empirical relationships are used for a rough estimate. The paper deals with a mathematical approach developed in order to evaluate the influence of a number of aerodynamic parameters conditioning the particle movements and trajectories in different emission and environmental patterns in order to identify a relationship on which to develop a numerical model of several industrial situations. The result can be useful both at the plant design stage and, in case of adjustments where the dust nature or size distribution varies due to production or maintenance reasons, can provide information for the exhaust system effectiveness evaluation on the basis of direct measurements of dust size distribution and of traverse velocities in the system ducts. Some examples of computer model results are provided and discussed in comparison with the exhaust efficiency evaluation as drawn in some laboratory tests. Where the particle shape is far from spherical, a number of additional difficulties arise where the mathematical approach is involved, and the results of some experimental tests are discussed to also pinpoint the practical limits of the numerical approach.
W. de Gids, TNO Built Environment, Delft, The Netherlands.
In two classrooms, tests have been carried out to study the effect of poor IAQ on the performance of schoolchildren. One classroom was fully under control in terms of ventilation and IAQ, the other was fully uncontrolled in terms of ventilation. The IAQ parameter CO2 was measured in both classrooms. Different types of tests were carried out to show the effect of poor indoor air quality on the learning performance of schoolchildren. The paper describes the setup of the project and gives the first analyses of the test results.
T. Lee, S. Moon, J. Heo, J. Lee, Hanyang University, Seoul, Republic of Korea; H. Yoo, Soongsil University, Seoul, Republic of Korea.
In this paper, the distributions of airflow and the concentrations of odor in the waste bunker of a municipal waste incinerator plant were investigated by numerical method. Waste vehicles enter the vehicle entrance and dump the waste into the waste pit, the lower part of bunker. To remove the odor generated from the dumped waste, a ventilation system with two air supply fans, two main exhaust fans, and an auxiliary exhaust fan has been installed in the middle of the bunker. In the period when waste is burned, the air is discharged horizontally from the two supply fans and is exhausted by the two main exhaust fans. During the incinerator shutdown, however, the air from the same supply fans is exhausted by the auxiliary exhaust fan instead of the main exhaust fans. At this time, odor can spread outward through the vehicle entrance. In order to prevent the spreading, some changes of discharge angle were tested by numerical experiments. As a result, the 45° upward angle was found to be good for stopping the odor from spreading.
S. Wang, C. Chen, Taiwan University, Taipei, Taiwan Republic of China; S. Wu, St. John’s University, Taipei County, Taiwan Republic of China; D. Lin, C. Chang, Institute of Occupational Safety and Health, Taipei County, Taiwan Republic of China.
In many indoor workplaces, wall-mounted receiving hoods have been mistakenly deployed as exterior hoods. It seems to be convenient and safe to have a large-scale, wall-mounted receiving hood installed above a table or workbench, but low face velocity, long vertical distance from contaminating source and unstable indoor cross draft make these hoods unsatisfactory because airborne contaminants can easily reach users’ breathing zone. To offer better user protection and higher capture efficiency of a wall-mounted receiving hood, a three-piece air curtain design is proposed to enclose the contaminating source and to cut off the dispersion of airborne contaminants generated inside the enclosed space. CFD simulation and smoke pencil tests show that, with the aid of air curtains, airborne contaminants can be kept from users’ breathing zone and pulled into the receiving hood if the contaminating source is located beneath a dividing plane. To make sure the improvement for capturing gaseous contaminants, tracer gas concentration measurement is done to compare with the results of CFD simulation and smoke pencil tests. It is found that tracer gas concentration in users’ breathing zone can be evidently reduced, and the capture efficiency of the wall-mounted receiving hood can be higher and more stable.
A. Jansson, Stockholm University, Stockholm, Sweden; L. Olander, Royal Institute of Technology, Stockholm, Sweden.
An exhaust hood with supply air had been preliminarily designed by a manufacturer. The hood is intended for manual soldering of electronic components. The basic idea is to design an exhaust cabinet with the interior airflow supported by an air curtain across the opening and a plane air jet along the back wall. The airflow is exhausted through two exhaust slots in cabinet ceiling. The air curtain aims to separate the interior of the cabinet from the outside environment, while the air jet assists in an orderly air movement inside the cabinet. Laboratory studies of airflow and movements were performed for the dimensioning of airflow rates, supply air slot design and size, and supply air directions. For the studies, heat from soldering was simulated by a 60 W light bulb placed in the cabinet. The interior airflow was determined by smoke studies and velocity measurements. Also, some tracer gas studies were performed. The results led to a redesign of the supply air terminals and to the leakage in the cabinet walls being stopped. Renewed studies with smoke showed a better flow pattern, and tracer gas studies showed that leakage at the opening sides had decreased. Tracer gas measurements documented leakage from the cabinet, which was significantly lower for a higher exhaust flow rate than for a lower exhaust flow. However, there was no difference when work in the cabinet was simulated by a person. Passage of a person behind the back of someone working in the cabinet did not affect leakage. It may be noted that the combination of methods for velocities, smoke, and tracer gas and their results constitutes a good tool for this kind of work.
D. Walters, KCP,Inc, Raleigh, NC; S. Kotha, R. Ryan, Flowsciences, Inc, Leland, NC.
The handling of potent materials in laboratories has changed significantly in recent years. Sophisticated computer and high-throughput robotic technology now perform synthesis-based research and development processes. Novel compounds of unknown potency are being used more and more in laboratories. As the use of such materials is rapidly expanding, and requires flexible task-specific containment solutions to minimize environmental impact, protect operators, and optimize process efficiency. Many laboratory operations can still be safely performed only in large, traditional, chemical fume hoods, or biological safety cabinets. But limitations often arise because containment in these fume hoods is not always effective. Traditional fume hoods are not task-specific and are not designed for high-throughput automated and robotic equipment. In addition, relocation of traditional hoods is difficult and their purchase, installation, and operation is expensive. Often, unique, process-specific containment solutions must be developed to provide safe, adaptable, and energy efficient enclosures in the rapidly changing laboratory environment. This presentation describes several custom designed vented enclosures that were developed for the pharmaceutical and biomedical industry. This project had three distinct phases. Each was critical for the project’s successful completion. First, specific robotic equipment and processes such as, liquid handling, incubators, and powder handling equipment were identified. Second, ventilated enclosure designs were optimized with computational fluid dynamics (CFD) to maximize containment and energy efficiency, to resolve ergonomic issues, and to provide easy access to the enclosed equipment. Finally, the enclosures were commissioned with on-site testing to ensure effective containment. This project emphasizes the importance of task-specific containment solutions for use with high-throughput and robotic equipment.
P. Mosconi, J. Vazquez, CEAH, Facultad de Arquitectura, Plan. y Diseño. Universidad Nacional de Rosario, Rosario, Argentina.
Heritage buildings are seldom related with quali-quantitative features like thermal, lighting and acoustical comfort. Critics of architecture focus on composition aspects, styles, symbols and values, and rarely refer to the comfort aspects in relation with building systems. In Argentina, especially at Rosario City, at the beginning of the 20th century, many representative buildings (public and private ones) were influenced by European architecture. For Rosario City, which has a temperate climate, some examples of this architecture respond to comfort requirements with massive walls, considerable volumes of interior spaces, and properly designed windows for lighting and ventilation issues as well as air conditioning. A 2-storied historical building located in downtown for commercial and office activities is presented: Pam Passage. From urban and architectonic consideration, it represents a valuable heritage of the 19th century, maintaining its original use. The passage is composed of two parts, one built in 1899 and the other in 1914. The passage connects two streets: Córdoba and Santa Fe. Both parts have a different treatment under a spatial point of view, though they present a unique architecture. It is a covered passage, in which the interior has a relevant spatiality because of natural light from skylights and small patios that connect the offices. A sequence of offices and patios form this public corridor and can be considered thermal regulators, providing lighting and ventilation. In the articulation of both parts of the building a huge skylight is located. In the upper floor, the offices are on the perimeter. Nowadays, these spaces are preferred by artists and book sellers, as well as office workers and private companies. This work tries to explain the building’s performance through the exploration of these patios that act as “lighting and ventilation pockets,” in terms of human comfort without the assistance of heating and refrigeration systems.
C. Porter, Air Science & Engineering, LLC, Dayville, CT.
Employees at a printing facility were reporting objectionable solvent odors from a process exhaust re-entering through the building HVAC systems. To solve the problem, calculations were performed using ASHRAE’s revised stack height and exhaust-to-intake dilution methods. As a secondary check, a CFD model was developed and intake concentrations determined with the proposed new stack in place. Consistent results were found between the various methods. The new stack was installed and the problem was resolved.
L. Conroy, L. Chen, T. Schoonover, S. Dorevitch, J. Artwohl, J. Fortman, University of Illinois at Chicago, Chicago, IL; T. Ooms, Tulane National Primate Center, New Orleans, LA.
More than 2 million workers in the United States are exposed to animals or animal products. Laboratory animal workers are exposed to many airborne contaminants produced by animals, bedding, and food. Studies show that 14-44% of animal workers report work-related allergic symptoms. The consequences of rat and mouse allergen exposure have been documented in the literature. Two studies, presented elsewhere, were conducted to determine emission factors for rabbits (ammonia, endotoxin, allergen, particulate matter [PM]) and mice (endotoxin, allergen, PM) in an animal research facility (ARF). The objective of this paper is to illustrate the use of emission factors to determine necessary ventilation rates to control airborne contaminants. A mass balance model was used to predict room concentrations for the ARF. The predictions compared favorably with concentrations measured in the facility, with the ratio of predicted to measured ranging from 0.72 to 3.9 for PM in rabbit and mouse rooms, respectively. The same model was used to determine necessary airflow rates to control airborne contaminants for a variety of environmental conditions (room sizes, mixing conditions, animal density). An example of the results shows that a room with 30 rabbits and a mixing factor of 0.6 would require 37 m3/min to control ammonia to 1 ppm (odor threshold). To control PM to the facility background of 30 µg/m3 requires 9 m3/min, while controlling endotoxin to the occupational exposure limit of 50 EU/m3 requires 2 m3/min. A mouse room with 700 mice requires 21 m3/min to control PM to 30 µg/m3 and 12 m3/min to control endotoxin to 50 EU/m3. These examples demonstrate controlling ammonia odor in rabbit rooms requires the highest airflow rates, whereas for mice that are housed with contact bedding, controlling PM requires the highest airflows. Emission factors allow efficient evaluation of control options for a wide variety of environmental conditions.
P. Tjelflaat, NTNU, Trondheim, Norway.
In large indoor swimming pools in cold climates, a substantial stack effect is formed. Swimming pools are commonly ventilated by mixing ventilation. The indoor air set value is normally 30ºC and 55% relative humidity. To avoid accumulation of water in the roof construction, a different room ventilation strategy is suggested. Supplying warm dry air at low velocity below the ceiling, combined with ventilation extract at the floor level, results in a layer of dry air below the ceiling. When punctures in the moisture membrane occur, only dry air enters the roof construction. This ventilation strategy has been investigated by performing CFD-simulations for a simplified case with an indoor swimming pool in the shape of a box. The winter design temperature considered is -19ºC. The width of the building is 50 m and the height is 17 m. Two opposing walls are glazed from floor to ceiling. The U-value of the windows and the roof are 1.4 and 0.15 W/(m2·K), respectively. The pool is 16 m wide. One scenario simulated has a supply of 1 air change per hour of outdoor air heated to 40ºC and supplied at ceiling level. The results show that no condensation occurs on windows and that thermal comfort is acceptable. At a level 0.5 m below the ceiling, the humidity of the air is 0.004 kg H2O per kg of dry air, whereas the value in the case of mixing ventilation would be 0.014. The strategy of using displacement ventilation from above in large indoor swimming pools is investigated and found to be satisfying for indoor thermal comfort. The concept is found very promising with respect to avoiding moisture damages to roof constructions for pool buildings in cold climates compared with the use of mixing ventilation.
S. Adachi, Y. Kondo, Musashi Institute of Technology, Tokyo, Japan; S. Ogita, Tonets Corporation, Chiba, Japan.
This paper is based on a study to make a ventilation system for electric commercial kitchens. No ventilation system has been constructed for use in electric kitchens. In the past, the only consideration for electric commercial kitchens was the evaluation of heat environment. There have been few studies on oily smoke and steam in commercial kitchens. An electric kitchen has good heat efficiency that does not disturb the airflow. So, there is no clear conclusion about a ventilation system. This experiment examined the behavior of oily smoke from fryers.
S. Crooks, RTI International, Research Triangle Park, NC.
The importance of “selecting the right tool for the job” could hardly be criticized as being understated. The field of exposure control design is no exception with this message being espoused in nearly every credible and usual reference made available to design professionals and industrial hygienists. Despite this, the number of encounters between cognizant professionals and poor “tool” selections seems to never end. This study seeks to look closely at the existence of the problem in one specific instance and identifies possible root causes. A review of the exposure control achieved is then put up against the less directly measurable effects on musculoskeletal health, productivity, and worker job satisfaction. The consequences of this one page out of the book on design detail are presented as yet another case for why detail, programming, and front loading CANNOT be overstated. A means of improving the design process is shown being implemented following lessons learned.
Posted May 30, 2006