Hood Capture Research Articles

Improved aerodynamic performance of the exhaust hood with triple-faced flange

For a local exhaust ventilation system to trap contaminants effectively, it is highly important to minimize its energy consumption without forgoing efficiency. Energy savings can be achieved by reducing the aerodynamic drag of non-straight elements of local ventilation systems. Goal of the study is to minimize the drag of an exhaust with a triple-faced flange by varying shelves lengths and tilt angles by the method of coordinated descent. Study conducted numerically and experimentally. For the first time a pattern of changes in LDC value depending on the size of the shelves was revealed. The minimum value of LDC is reached when the length of the first shelf adjacent to the exhaust channel is 0.5l (l -half width of the slot or radius of round exhaust hood), the angle of its inclination is 30°; the length of the second shelf is 0.7l with an angle of inclination of 90°; the length of the third shelf is 0.2l with an angle of inclination of 120°. The found velocity distribution shows the effectiveness of the exhaust hood capture. The reduction of the LDC, when compared with the typical exhaust hood with the flange inclined on 90° was 76 %, and compared with a real industrial exhaust hood from the welding table – 65.7 %. The outline of vortex zones at the entrance to the exhaust hood was determined by different methods. The findings can be used for the design and development of energy-saving slotted and round exhaust hoods.

Welding Fume: A Comparison Study of Industry Used Control Methods

Welding fume is generated during welding activities and is a known cancer-causing hazard for those working in the welding industry. Worker exposure has been shown to regularly exceed the applicable workplace exposure standard, and control measures are required to reduce worker exposure. The aim of this study is to compare the effectiveness of control measures to prevent welding fume exposure to workers. To achieve this aim, three common welding fume control measures (local exhaust ventilation (LEV), powered air purifying respirators (PAPRs) and on-gun extraction) were used during four different welding tasks. Compared to using no controls, LEV hood capture is likely to reduce welding fume concentrations in the breathing zone of a welder by up to a factor of 9. The use of on-gun LEV is likely to reduce welding fume concentrations in the breathing zone of a welder by up to a factor of 12. The 5th percentile effective protection factors of the PAPR for all sampled welding activities were considerably greater than the required minimum protection factor of 50 specified in AS/NZS 1715:2009 for powered air purifying respirators (PAPRs) with class PAPR-P3 particulate filters with any head covering.

Performance of combination of local exhaust system and floor‐supply displacement ventilation system as prevention measure of infection in consulting room

AbstractDroplet nuclei and tiny enough droplets to move as an aerosol are regarded as one of the modes of infection transmission SARS‐CoV‐2. Various measures have been taken to prevent it worldwide. Nevertheless, many scenarios cannot be avoided close‐distance conversations, for example, in a consulting room, restaurant, or crowded train. A consulting room has significant potential for doctors to contact infected patients. Therefore, this study proposes a novel approach combining a local exhaust ventilation (LEV) and floor‐supply displacement ventilation system (FSDV) in a consulting room. This study assumes that two persons (doctor and patient) are sitting face to face and talking without a mask in a simple room regarded as a consulting room. The velocity and volume of exhaled air from talking were acquired through field measurements. Then, computational fluid dynamics (CFD) steady analysis was carried out, using the results of exhaled air measurement with various parameters (hood height, hood flow rate, horizontal hood position, and air flow rate). The capture efficiency for tracer gas and contribution distribution for the hood (SVE5: scale for ventilation efficiency 5) have been calculated to reveal the hood's capture performance. In addition, infection risk for the doctor was also calculated using the Wells–Riley model to estimate the infection performance of this ventilation system. By measuring exhaled air from talking, a speed of 0.30 m/s, a volume of 5.21 L/min, and a vertical angle of 11.9° were obtained, and these values were installed into CFD. The CFD results showed that hood flow rate significantly impacts capture efficiency at SA 120 m3/h (6 ACH), and horizontal hood position significantly impacts at SA 1000 m3/h (50 ACH). SVE5 also showed hood's effective area is greatly influenced by the flow rate balance between the hood and the other exhaust routes. Under high air supply conditions: SA 1000 m3/h (50 ACH), there was almost no airborne transmission risk for a doctor with or without a hood. However, under 120 m3/h (6 ACH) conditions, the combination of the hood and FSDV system could reduce an infection risk sufficiently. The hood should be located above the infected person's head to keep the counter person's infectious risk low, indicating that the introduction of the hood is reasonable in the consulting room, where it is easy to find where the infected person is.

Optimization research based on local exhaust of oil mist particles in cutting machine tool

Oil particles generated from metalworking fluids(MWFs) in machining process can lead serious health problem to operator. Local exhaust hood is an effective engineering method to capture oil particles and other contamination which is wildly used in manufacture workshop. In this paper, exhaust hood capture efficiency with various height, air volume and particle size was gotten by Computational Fluid Dynamic(CFD) technology. Though further analysis of the CFD result, feature air velocity was introduced. Then an equation of feature velocity and capture efficiency was established by multi regression method. According to this equation one improvement solution was studied: Set to flexible enclosure for up exhaust hood. The solution raised particle capture efficiency on each size significant, the result is equivalent to low down up exhaust hood for 60cm.

The effects of cook-top temperature on range hood capture efficiency

In this study a test procedure for determining capture efficiency (CE) of wall-mounted range hoods, namely ASTM-E3087.18, was used to investigate how the temperature of the simulated cook-top influences CE. ASTM-E3087.18 was initially released in 2017 and revised within one year to modify the temperature requirements of the cook-top from 200 °C to 160 °C; however, there is no evidence of a detailed study being performed to quantify the effects of this temperature change on CE. The study reported herein performed testing at 200 °C, 160 °C and 130 °C for five range hoods with three different design types. CE ranged from 60.3–92.9%CE with CE variations as high as 9.2%CE when varying temperature, and uncertainty (δ) always varying by less than 1.0%CE. The influence of cook-top temperature on CE repeatability, reproducibility and variability was also investigated, with each metric varying by a maximum of 1.2%CE, 1.5%CE and 1.1%, respectively, with varying temperatures. Range hoods with poor burner coverage (i.e. over-the-range microwaves) showed higher variability/uncertainty, indicating temperature effects are more dominant when range hoods have less burner coverage. It is possible that future HVI/ASHRAE certifications specify different acceptability/test requirements for CE, as well as the CE uncertainty/repeatability, of range hoods with poor burner coverage.

An effective ventilation system for preventing indoor PM2.5 dispersion

Korean public housing ventilation systems mainly use natural ventilation and local exhausts. When a local exhaust is operated in a narrow space such as a kitchen, the air pressure loss can lack balance. A decrease in hood capture efficiency and ventilation effectiveness causes the problem that people in the living room can be exposed to PM2.5 generated by cooking. Therefore, it is necessary to develop an effective ventilation strategy for the local exhaust, considering the make-up air supply. In this study, a ventilation system that integrates the range hood and ventilation systems (e.g., heat recovery equipment and auxiliary air supply) was developed to resolve this issue. Multi point measurement was conducted using five low-cost sensors to determine the location of the sensors in the kitchen and living room. TSI-DustTrak 8532 and OPS3330 were performed with different ventilation system operating types. When the range hood was operated for one hour, the concentrations in the kitchen and living room were significantly high; 676 μg/m3 and 373 μg/m3, respectively. After the integrated operating algorithm was installed, the kitchen concentration was 185 μg/m3, and the living room concentration was 68 μg/m3. With an additional flow rate of 50 CMH through Heat recovery ventilator (HRV) the reduction in the concentration of PM2.5 was more effective. As a result, this advanced system was able to remove up to 60% of PM2.5 generated by cooking. The integrated system of the auxiliary air supply and range hood was evaluated to be effective in preventing the distribution of kitchen pollutants.

Development of a standard capture efficiency test method for residential kitchen ventilation

Cooking activities are a major source of indoor air pollutants. To control pollutants generated from cooking activities, a range hood is commonly used in residential kitchens. Several building codes require that a range hood be installed in new homes to control pollutants from cooking, and the required airflow rates for range hoods are specified by indoor air quality standards. However, airflow alone does not show how much of the cooking pollutants are exhausted by the range hood. A better metric to evaluate range hood indoor air quality performance is capture efficiency—the fraction of contaminants emitted during cooking that are exhausted directly to the outside via the range hood. The current article summarizes the development of a range hood capture efficiency test method for use in laboratory testing and equipment rating.

空調擾乱などがある状態での排気フードの捕集率測定法に関する研究 (その2) 数値実験と実大実験による捕集率測定法の検証

空調擾乱などがある状態での排気フードの捕集率測定法に関する研究 (その2) 数値実験と実大実験による捕集率測定法の検証

初期分配率に基づく排気フードの捕集率の推定方法 第1報 実験による捕集率に対応する分配率の検討

初期分配率に基づく排気フードの捕集率の推定方法 第1報 実験による捕集率に対応する分配率の検討

Life-cycle cost and benefit analysis of utilizing hoods for light-duty cooking appliances in commercial kitchens (RP-1631, part 2)

The objective of this study was to compare the life-cycle cost of using a dedicated hood exhaust and replacement air system versus the cost of removing heat and moisture by the kitchen's general HVAC system. With measured sensible and latent heat generation data from Part I of the RP-1631, whole-building energy performance simulations and cost–benefit analysis were conducted for a generic prototype model of restaurants/cafeteria that included a dining and kitchen zone. Simulations were performed for 12 climate zones in the United States and different amounts of transfer air from the dining to the cooking zone. For most of the climates simulated, the hooded cases resulted in an increase in energy consumption, particularly for the heating-dominated regions, since the heat from the appliance was not used for space heating. In the cooling dominated regions, the hooded cases had about the same or less energy consumption due to reduced cooling loads. However, after integrating the initial cost, maintenance cost, and operating cost in a 10-year lifespan, utilizing a hood with 100% TR always gave the lowest life-cycle cost. This is a result of the lower operating cost compared to the unhooded case and no need for a makeup air system, saving in both equipment and operating cost, compared to the other hooded cases. The study fills a knowledge gap on the impact of commercial kitchen HVAC system design on the energy consumption and life-cycle-cost with realistically measured data of heat and moisture generation from electric counter-top cooking appliances. Also, the potential impact of the hood's capture efficiency on the thermal comfort and indoor air quality was analyzed.

Moving Speed and Frequency of Panel to Simulate Air Turbulence Caused by Cooking Operations in Hood Capture Efficiency Test for Commercial Kitchens

Moving Speed and Frequency of Panel to Simulate Air Turbulence Caused by Cooking Operations in Hood Capture Efficiency Test for Commercial Kitchens

空調擾乱などがある状態での排気フードの捕集率測定法に関する研究 (その1) 捕集率測定のための実験室の概要と捕集率算出式

空調擾乱などがある状態での排気フードの捕集率測定法に関する研究 (その1) 捕集率測定のための実験室の概要と捕集率算出式

The impact of various hood shapes, and side panel and exhaust duct arrangements, on the performance of typical Chinese style cooking hoods

In Chinese commercial kitchens, a large amount of moisture and heat is produced and must be removed, which can require ventilation rates resulting in huge levels of energy consumption. Excessive airflow rates can increase unnecessary energy consumption and system life-cycle costs. For many middle and small scale commercial kitchens in China, the indoor, thermal environment is far worse than acceptable levels. The use of an efficient kitchen hood is essential to ensure a comfortable working environment and better energy conservation. In this study, many types of hood shapes and side panels were developed to improve the capture efficiency of traditional Chinese style cooking hoods. The arrangement of the exhaust ducts was also investigated. Basic site tests and computational fluid dynamics (CFD) analysis were conducted. The simulated results showed that increasing hood volume did not improve capture performance. However, side panels did improve the capture efficiency, especially at higher positions. In addition, when the exhaust opening was located at the rear of the hood, the hood capture efficiency improvement was enhanced.

Fume Hood Performance: Using a Bypass in Variable Air Volume Systems

Abstract Variable air volume (VAV) exhaust systems provide sophisticated engineering controls for maintaining laboratory ventilation. Depending on how they are installed, they may be very responsive to changes in air flows and air pressures. Some of these changes are a consequence of natural phenomena and some are induced by the transit and actions of laboratory occupants. While the responsiveness of VAV controls can provide tight regulation, the dynamic nature of the VAV system may also introduce undesirable air flow fluctuations. Further-more, since the volumes of air being exhausted vary, the amount of air available for fume hood capture and containment will also vary. These studies examine the responsiveness and consequences of ventilation system perturbations, as well as the effect of fume hood exhaust being reduced to very low air volumes. Face velocity and air volumes were measured at different sash heights and in response to rapid sash movements. In addition, capture of contaminants was evaluated ...

Hood Efficiencies of Vapor Degreasers Under Operating Conditions

The objective of this research was to measure capture efficiency of local exhaust hoods used to control vapor degreasing tanks during normal operations and to compare the observed capture efficiencies to the American Conference of Governmental Industrial Hygienists (ACGIH) design criteria. Solvent emission rates and local exhaust hood capture efficiencies were measured at 15 vapor degreasers. The degreasers were located in 12 private industrial settings and studied under normal operating conditions. Where possible, hourly concentration data were collected during two 8-h shifts for each degreaser. Site-average fugitive emissions to the workspace (mean = 0.173 g/m{sup 2}/s, range = 0.001 {minus} 1.08 g/m{sup 2}/s) were in excellent agreement with previously reported tests for vapor degreasers under operating conditions. The ACGIH recommended flow of 0.25 m{sup 3}/s/m{sup 2} (50 cu ft/min/sq ft) of tank surface appears to be adequate for some conditions but inadequate for other conditions. An increase in flow, above design recommendations, did not necessarily improve hood performance. Hood capture efficiency was slightly correlated with hood face velocity, although there is significant variability in the data. Emissions of solvent to the workspace were only slightly correlated with duct emissions. This suggests that fugitive emissions are as strongly related to workmore » practices as they are to control device design.« less

The design of local exhaust ventilation hoods for grinding wheels

The simplest method of controlling airborne contaminants produced during grinding is the free-standing local exhaust ventilation hood. However design data are sparse and not related to individual applications, for example neither extract rate nor hood size is related to the wheel size. Hoods for use with grinding wheels are usually designed as captor hoods but it is shown in this study that such hoods act as receptors and should be designed on that basis. Flow visualization, using both smoke pellets and a heated oil-impregnated wire, showed the air flow patterns which are induced by a rapidly rotating wheel. Air speeds around the wheels were measured using omnidirectional probes whilst hood capture efficiencies were measured using tracer gas techniques. These observations and measurements identified several key parameters which should lead to a more effective and efficient design of control systems for use with surface grinders.

Computer Simulation in the Design of Local Exhaust Hoods for Shielded Metal Arc Welding

Computer simulations were used to examine competing exhaust hood configurations for shielded metal arc welding. The welder's breathing zone concentration appears to be an inverse linear function of the computer-predicted hood capture efficiency. Hood aspect ratio, hood flow, and the welder's position relative to the hood all have a significant effect on the breathing zone concentration. The height of the hood above the welding surface showed no significant effect in reducing breathing zone concentration. Further examination of breathing zone concentration as a function of capture efficiency is needed before reliable design methods can be developed using this parameter.

Computer Simulation in the Design of Local Exhaust Hoods for Shielded Metal Arc Welding

Computer simulations were used to examine competing exhaust hood configurations for shielded metal arc welding. The welder's breathing zone concentration appears to be an inverse linear function of the computer-predicted hood capture efficiency. Hood aspect ratio, hood flow, and the welder's position relative to the hood all have a significant effect on the breathing zone concentration. The height of the hood above the welding surface showed no significant effect in reducing breathing zone concentration. Further examination of breathing zone concentration as a function of capture efficiency is needed before reliable design methods can be developed using this parameter.