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Multizone Age-of-Air Analysis

Description: Age of air is a technique for evaluating ventilation that has been actively used for over 20 years. Age of air quantifies the time it takes for outdoor air to reach a particular location or zone within then indoor environment. Age of air is often also used to quantify the ventilation effectiveness with respect to indoor air quality. In a purely single zone situation this use of age of air is straightforward, but application of age of air techniques in the general multizone environment has not been fully developed. This article looks at expanding those single-zone techniques to the more complicated environment of multizone buildings and in doing so develops further the general concept of age of air. The results of this analysis shows that the nominal age of air as often used cannot be directly used for determining ventilation effectiveness unless specific assumptions are made regarding source distributions.
Date: July 1, 2007
Creator: Sherman, Max H.
Partner: UNT Libraries Government Documents Department

Optical People Counting for Demand Controlled Ventilation: A Pilot Study of Counter Performance

Description: This pilot scale study evaluated the counting accuracy of two people counting systems that could be used in demand controlled ventilation systems to provide control signals for modulating outdoor air ventilation rates. The evaluations included controlled challenges of the people counting systems using pre-planned movements of occupants through doorways and evaluations of counting accuracies when naive occupants (i.e., occupants unaware of the counting systems) passed through the entrance doors of the building or room. The two people counting systems had high counting accuracy accuracies, with errors typically less than 10percent, for typical non-demanding counting events. However, counting errors were high in some highly challenging situations, such as multiple people passing simultaneously through a door. Counting errors, for at least one system, can be very high if people stand in the field of view of the sensor. Both counting system have limitations and would need to be used only at appropriate sites and where the demanding situations that led to counting errors were rare.
Date: December 26, 2009
Creator: Fisk, William J. & Sullivan, Douglas
Partner: UNT Libraries Government Documents Department

New Methods of Energy Efficient Radon Mitigation

Description: Two new radon mitigation techniques are introduced and their evaluation in a field study complemented by numerical model predictions is described. Based on numerical predictions, installation of a sub gravel membrane at the study site resulted in a factor of two reduction in indoor radon concentrations. Experimental data indicated that installation of 'short-circuit' pipes extending between the subslab gravel and outdoors, caused an additional factor of two decrease in the radon concentration. Consequently, the combination of these two passive radon mitigation features, called the membrane and short-circuit (MASC) technique, was associated with a factor of four reduction in indoor radon concentration. The energy-efficient active radon mitigation method, called efficient active subslab pressurization (EASP), required only 20% of the fan energy of conventional active subslab depressurization and reduced the indoor radon concentration by approximately a factor of 15, including the numerically-predicted impact of the sub-gravel membrane.
Date: May 1, 1994
Creator: Fisk, W.J.; Prill, R.J.; Wooley, J.; Bonnefous, Y.C.; Gadgil, A.J. & Riley, W.J.
Partner: UNT Libraries Government Documents Department

Changing ventilation rates in U.S. offices: Implications for health, work performance, energy, and associated economics

Description: This paper provides quantitative estimates of benefits and costs of providing different amounts of outdoor air ventilation in U.S. offices. For four scenarios that modify ventilation rates, we estimated changes in sick building syndrome (SBS) symptoms, work performance, short-term absence, and building energy consumption. The estimated annual economic benefits were $13 billion from increasing minimum ventilation rates (VRs) from 8 to 10 L/s per person, $38 billion from increasing minimum VRs from 8 to 15 L/s per person, and $33 billion from increasing VRs by adding outdoor air economizers for the 50% of the office floor area that currently lacks economizers. The estimated $0.04 billion in annual energy-related benefits of decreasing minimum VRs from 8 to 6.5 L/s per person are very small compared to the projected annual costs of $12 billion. Benefits of increasing minimum VRs far exceeded energy costs while adding economizers yielded health, performance, and absence benefits with energy savings.
Date: July 1, 2011
Creator: Fisk, William; Black, Douglas & Brunner, Gregory
Partner: UNT Libraries Government Documents Department

Accuracy of CO2 sensors in commercial buildings: a pilotstudy

Description: Carbon dioxide (CO{sub 2}) sensors are often deployed in commercial buildings to obtain CO{sub 2} data that are used to automatically modulate rates of outdoor air supply. The goal is to keep ventilation rates at or above code requirements, but to also to save energy by avoiding over ventilation relative to code requirements. However, there have been many anecdotal reports of poor CO{sub 2} sensor performance in actual commercial building applications. This study evaluated the accuracy of 44 CO{sub 2} sensors located in nine commercial buildings to determine if CO{sub 2} sensor performance, in practice, is generally acceptable or problematic. CO{sub 2} measurement errors varied widely and were sometimes hundreds of parts per million. Despite its small size, this study provides a strong indication that the accuracy of CO{sub 2} sensors used in commercial buildings is frequently less than is needed to measure peak indoor-outdoor CO{sub 2} concentration differences with less than a 20% error. Thus, we conclude that there is a need for more accurate CO{sub 2} sensors and/or better sensor maintenance or calibration procedures.
Date: October 1, 2006
Creator: Fisk, William J.; Faulkner, David & Sullivan, Douglas P.
Partner: UNT Libraries Government Documents Department

Air Distribution Effectiveness for Different MechanicalVentilation Systems

Description: The purpose of ventilation is to dilute indoor contaminants that an occupant is exposed to. In a multi-zone environment such as a house, there will be different dilution rates and different source strengths in every zone. Most US homes have central HVAC systems, which tend to mix conditions between zones. Different types of ventilation systems will provide different amounts of dilution depending on the effectiveness of their air distribution systems and the location of sources and occupants. This paper will report on work being done to both model the impact of different systems and measurements using a new multi-tracer measurement system that has the capacity to measure not only the flow of outdoor air to each zone, but zone-to-zone transport. The ultimate objective of this project is to determine the effectiveness of different systems so that appropriate adjustments can be made in residential ventilation standards such as ASHRAE Standard 62.2.
Date: August 1, 2007
Creator: Sherman, Max H. & Walker, Iain S.
Partner: UNT Libraries Government Documents Department

Performance of underfloor air distribution in a fieldsetting

Description: Underfloor air distribution (UFAD) is a new method of supplying heated or cooled air throughout a building. Reported advantages of UFAD include energy savings and improved indoor air quality (IAQ). We measured several aspects of the performance of an UFAD system installed in a medium-size office building. The measured air change effectiveness was very close to unity, which is comparable to that measured in buildings with typical overhead air distribution. The pollutant removal efficiency for carbon dioxide was 13% higher than expected in a space with well-mixed air, suggesting a 13% reduction in exposures to occupant generated pollutants. The increase in indoor air temperatures with height above the floor was only 1 to 2 C. This amount of thermal stratification could reduce the sensible energy requirements for cooling of outdoor air by approximately 10%. The occupant's level of satisfaction with thermal conditions was well above average and this high satisfaction rating could possibly be due, in all or part, to the use of a UFAD system. The results of this study provide some evidence of moderate energy and IAQ-related benefits of UFAD. Before general conclusions are drawn, the benefits need to be confirmed in other studies.
Date: October 1, 2005
Creator: Fisk, W.J.; Faulkner, D.; Sullivan, D.P.; Chao, C.; Wan, M.P.; Zagreus, L. et al.
Partner: UNT Libraries Government Documents Department

Measuring Outdoor Airflow into HVAC Systems

Description: The rate of outdoor air (OA) supply affects building energy consumption, occupant health, and work performance; however, minimum ventilation rates are often poorly controlled. Real-time measurements of OA flow rates into HVAC systems would enable improved flow control. This article demonstrates that at least some of the available technologies for real-time measurement of OA air intake rate are reasonably accurate and provides guidance on how these technologies should be used.
Date: August 1, 2005
Creator: Fisk, William J.; Faulkner, David & Sullivan, Douglas P.
Partner: UNT Libraries Government Documents Department

Real-Time Measurement of Rates of Outdoor Airflow into HVACSystems: A Field Study of Three Technologies

Description: Technologies for real-time continuous measurement of the flow rates of outdoor air (OA) into HVAC systems are now available commercially. Our prior papers reported on laboratory-based evaluations of these measurement technologies and this document describes the methods and results of a field study of the accuracy of three of these technologies. From the field study data, we determined that neither wind speed nor wind direction have an important adverse impact on measurement accuracy. The field study confirmed that these three measurement technologies can provide reasonably accurate measurements of outdoor air intake rates in field settings, if the pressure signals are measured with high accuracy. Some of the pressure transducers marketed for use with commercial HVAC systems were determined to be sufficiently accurate for this application. Given the significant impact of OA flow rates on both energy use and occupant health, more widespread use of technologies that provide for real time measurements of OA flow rates seems warranted.
Date: September 1, 2005
Creator: Fisk, William J.; Sullivan, Douglas P. & Faulkner, David
Partner: UNT Libraries Government Documents Department

Advanced Electrical, Optical and Data Communication Infrastructure Development

Description: The implementation of electrical and IT infrastructure systems at the North Carolina Center for Automotive Research , Inc. (NCCAR) has achieved several key objectives in terms of system functionality, operational safety and potential for ongoing research and development. Key conclusions include: (1) The proven ability to operate a high speed wireless data network over a large 155 acre area; (2) Node to node wireless transfers from access points are possible at speeds of more than 50 mph while maintaining high volume bandwidth; (3) Triangulation of electronic devices/users is possible in areas with overlapping multiple access points, outdoor areas with reduced overlap of access point coverage considerably reduces triangulation accuracy; (4) Wireless networks can be adversely affected by tree foliage, pine needles are a particular challenge due to the needle length relative to the transmission frequency/wavelength; and (5) Future research will use the project video surveillance and wireless systems to further develop automated image tracking functionality for the benefit of advanced vehicle safety monitoring and autonomous vehicle control through 'vehicle-to-vehicle' and 'vehicle-to-infrastructure' communications. A specific advantage realized from this IT implementation at NCCAR is that NC State University is implementing a similar wireless network across Centennial Campus, Raleigh, NC in 2011 and has benefited from lessons learned during this project. Consequently, students, researchers and members of the public will be able to benefit from a large scale IT implementation with features and improvements derived from this NCCAR project.
Date: April 30, 2011
Creator: Cobb, Simon
Partner: UNT Libraries Government Documents Department

Providing better indoor environmental quality brings economicbenefits

Description: This paper summarizes the current scientific evidence that improved indoor environmental quality can improve work performance and health. The review indicates that work and school work performance is affected by indoor temperature and ventilation rate. Pollutant source removal can sometimes improve work performance. Based on formal statistical analyses of existing research results, quantitative relationships are provided for the linkages of work performance with indoor temperature and outdoor air ventilation rate. The review also indicates that improved health and related financial savings are obtainable from reduced indoor tobacco smoking, prevention and remediation of building dampness, and increased ventilation. Example cost-benefit analyses indicate that many measures to improve indoor temperature control and increase ventilation rates will be highly cost effective, with benefit-cost ratios as high as 80 and annual economic benefits as high as $700 per person.
Date: June 1, 2007
Creator: Fisk, William & Seppanen, Olli
Partner: UNT Libraries Government Documents Department

JV Task 86 - Identifying the Source of Benzene in Indoor Air Using Different Compound Classes from TO-15 Data

Description: Volatile organic compound (VOC) data that had already been collected using EPA method TO-15 at four different sites under regulatory scrutiny (a school, strip mall, apartment complex, and business/residential neighborhood) were evaluated to determine whether the source of indoor air benzene was outdoor air or vapor intrusion from contaminated soil. Both the use of tracer organics characteristic of different sources and principal component statistical analysis demonstrated that the source of indoor air at virtually all indoor sampling locations was a result of outdoor air, and not contaminated soil in and near the indoor air-sampling locations. These results show that proposed remediation activities to remove benzene-contaminated soil are highly unlikely to reduce indoor air benzene concentrations. A manuscript describing these results is presently being prepared for submission to a peer-reviewed journal.
Date: April 15, 2007
Creator: Hawthorne, Steven B.
Partner: UNT Libraries Government Documents Department

Modeling particle loss in ventilation ducts

Description: Empirical equations were developed and applied to predict losses of 0.01-100 {micro}m airborne particles making a single pass through 120 different ventilation duct runs typical of those found in mid-sized office buildings. For all duct runs, losses were negligible for submicron particles and nearly complete for particles larger than 50 {micro}m. The 50th percentile cut-point diameters were 15 {micro}m in supply runs and 25 {micro}m in return runs. Losses in supply duct runs were higher than in return duct runs, mostly because internal insulation was present in portions of supply duct runs, but absent from return duct runs. Single-pass equations for particle loss in duct runs were combined with models for predicting ventilation system filtration efficiency and particle deposition to indoor surfaces to evaluate the fates of particles of indoor and outdoor origin in an archetypal mechanically ventilated building. Results suggest that duct losses are a minor influence for determining indoor concentrations for most particle sizes. Losses in ducts were of a comparable magnitude to indoor surface losses for most particle sizes. For outdoor air drawn into an unfiltered ventilation system, most particles smaller than 1 {micro}m are exhausted from the building. Large particles deposit within the building, mostly in supply ducts or on indoor surfaces. When filters are present, most particles are either filtered or exhausted. The fates of particles generated indoors follow similar trends as outdoor particles drawn into the building.
Date: April 1, 2003
Creator: Sippola, Mark R. & Nazaroff, William W.
Partner: UNT Libraries Government Documents Department

"Defense-in-Depth" Laser Safety and the National Ignition Facility

Description: The National Ignition Facility (NIF) is the largest and most energetic laser in the world contained in a complex the size of a football stadium. From the initial laser pulse, provided by telecommunication style infrared nanoJoule pulsed lasers, to the final 192 laser beams (1.8 Mega Joules total energy in the ultraviolet) converging on a target the size of a pencil eraser, laser safety is of paramount concern. In addition to this, there are numerous high-powered (Class 3B and 4) diagnostic lasers in use that can potentially send their laser radiation travelling throughout the facility. With individual beam paths of up to 1500 meters and a workforce of more than one thousand, the potential for exposure is significant. Simple laser safety practices utilized in typical laser labs just don't apply. To mitigate these hazards, NIF incorporates a multi layered approach to laser safety or 'Defense in Depth.' Most typical high-powered laser operations are contained and controlled within a single room using relatively simplistic controls to protect both the worker and the public. Laser workers are trained, use a standard operating procedure, and are required to wear Personal Protective Equipment (PPE) such as Laser Protective Eyewear (LPE) if the system is not fully enclosed. Non-workers are protected by means of posting the room with a warning sign and a flashing light. In the best of cases, a Safety Interlock System (SIS) will be employed which will 'safe' the laser in the case of unauthorized access. This type of laser operation is relatively easy to employ and manage. As the operation becomes more complex, higher levels of control are required to ensure personnel safety. Examples requiring enhanced controls are outdoor and multi-room laser operations. At the NIF there are 192 beam lines and numerous other Class 4 diagnostic lasers that can potentially ...
Date: December 2, 2010
Creator: King, J J
Partner: UNT Libraries Government Documents Department

Evaluation of surface sampling method performance for Bacillus Spores on clean and dirty outdoor surfaces.

Description: Recovery of Bacillus atrophaeous spores from grime-treated and clean surfaces was measured in a controlled chamber study to assess sampling method performance. Outdoor surfaces investigated by wipe and vacuum sampling methods included stainless steel, glass, marble and concrete. Bacillus atrophaeous spores were used as a surrogate for Bacillus anthracis spores in this study designed to assess whether grime-coated surfaces significantly affected surface sampling method performance when compared to clean surfaces. A series of chamber tests were carried out in which known amounts of spores were allowed to gravitationally settle onto both clean and dirty surfaces. Reference coupons were co-located with test coupons in all chamber experiments to provide a quantitative measure of initial surface concentrations of spores on all surfaces, thereby allowing sampling recovery calculations. Results from these tests, carried out under both low and high humidity conditions, show that spore recovery from grime-coated surfaces is the same as or better than spore recovery from clean surfaces. Statistically significant differences between method performance for grime-coated and clean surfaces were observed in only about half of the chamber tests conducted.
Date: June 1, 2011
Creator: Wilson, Mollye C.; Einfeld, Wayne; Boucher, Raymond M.; Brown, Gary Stephen & Tezak, Matthew Stephen
Partner: UNT Libraries Government Documents Department

Factors affecting the indoor concentrations of carbonaceous aerosols of outdoor origin

Description: A field study was conducted in an unoccupied single story residence in Clovis, California to provide data to address issues important to assess the indoor exposure to particles of outdoor origin. Measurements of black and organic carbonaceous aerosols were performed using a variety of methods, resulting in both near real-time measurements as well as integrated filter based measurements. Comparisons of the different measurement methods show that it is crucial to account for gas phase adsorption artifacts when measuring organic carbon (OC). Measured concentrations affected by the emissions of organic compounds sorbed to indoor surfaces imply a higher degree of infiltration of outdoor organic carbon aerosols into the indoor environment for our unoccupied house. Analysis of the indoor and outdoor data for black carbon (BC) aerosols show that, on average, the indoor concentration of black carbon aerosols behaves in a similar manner to sulfate aerosols. In contrast, organic carbon aerosols are subject to chemical transformations indoors that, for our unoccupied home, resulted in lower indoor OC concentrations than would be expected by physical loss mechanisms alone. These results show that gas to particle partitioning of organic compounds, as well as gas to surface interactions within the residence, are an important process governing the indoor concentration to OC aerosols of outdoor origin.
Date: June 25, 2007
Creator: Lunden, Melissa M.; Kirchstetter, Thomas W.; Thatcher, Tracy L.; Hering, Susanne V. & Brown, Nancy J.
Partner: UNT Libraries Government Documents Department

ACCURACY OF CO2 SENSORS

Description: Are the carbon dioxide (CO2) sensors in your demand controlled ventilation systems sufficiently accurate? The data from these sensors are used to automatically modulate minimum rates of outdoor air ventilation. The goal is to keep ventilation rates at or above design requirements while adjusting the ventilation rate with changes in occupancy in order to save energy. Studies of energy savings from demand controlled ventilation and of the relationship of indoor CO2 concentrations with health and work performance provide a strong rationale for use of indoor CO2 data to control minimum ventilation rates1-7. However, this strategy will only be effective if, in practice, the CO2 sensors have a reasonable accuracy. The objective of this study was; therefore, to determine if CO2 sensor performance, in practice, is generally acceptable or problematic. This article provides a summary of study methods and findings ? additional details are available in a paper in the proceedings of the ASHRAE IAQ?2007 Conference8.
Date: October 1, 2008
Creator: Fisk, William J.; Faulkner, David & Sullivan, Douglas P.
Partner: UNT Libraries Government Documents Department

Minimizing Variation in Outdoor CPV Power Ratings

Description: Module data from NREL's CPV test bed is used to examine methods for calculating outdoor CPV power ratings. IEC 62670 and ASTM E2527 are used as a starting point for determining a module power rating on a monthly basis. Monthly power ratings vary by more than desired using existing methods. The presentation examines modifications to existing methods as well as spectral corrections to reduce variation in monthly module power ratings.
Date: February 1, 2011
Creator: Muller, M.
Partner: UNT Libraries Government Documents Department

Global Cooling: Policies to Cool the World and Offset Global Warming from CO2 Using Reflective Roofs and Pavements

Description: Increasing the solar reflectance of the urban surface reduce its solar heat gain, lowers its temperatures, and decreases its outflow of thermal infrared radiation into the atmosphere. This process of 'negative radiative forcing' can help counter the effects of global warming. In addition, cool roofs reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win-win-win activity that can be undertaken immediately, outside of international negotiations to cap CO{sub 2} emissions. We propose an international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions.
Date: August 28, 2009
Creator: Akbari, Hashem; Levinson, Ronnen; Rosenfeld, Arthur & Elliot, Matthew
Partner: UNT Libraries Government Documents Department

CO2 MONITORING FOR DEMAND CONTROLLED VENTILATION IN COMMERCIAL BUILDINGS

Description: Carbon dioxide (CO{sub 2}) sensors are often deployed in commercial buildings to obtain CO{sub 2} data that are used, in a process called demand-controlled ventilation, to automatically modulate rates of outdoor air ventilation. The objective is to keep ventilation rates at or above design specifications and code requirements and also to save energy by avoiding excessive ventilation rates. Demand controlled ventilation is most often used in spaces with highly variable and sometime dense occupancy. Reasonably accurate CO{sub 2} measurements are needed for successful demand controlled ventilation; however, prior research has suggested substantial measurement errors. Accordingly, this study evaluated: (a) the accuracy of 208 CO{sub 2} single-location sensors located in 34 commercial buildings, (b) the accuracy of four multi-location CO{sub 2} measurement systems that utilize tubing, valves, and pumps to measure at multiple locations with single CO{sub 2} sensors, and (c) the spatial variability of CO{sub 2} concentrations within meeting rooms. The field studies of the accuracy of single-location CO{sub 2} sensors included multi-concentration calibration checks of 90 sensors in which sensor accuracy was checked at multiple CO{sub 2} concentrations using primary standard calibration gases. From these evaluations, average errors were small, -26 ppm and -9 ppm at 760 and 1010 ppm, respectively; however, the averages of the absolute values of error were 118 ppm (16%) and 138 ppm (14%), at concentrations of 760 and 1010 ppm, respectively. The calibration data are generally well fit by a straight line as indicated by high values of R{sup 2}. The Title 24 standard specifies that sensor error must be certified as no greater than 75 ppm for a period of five years after sensor installation. At 1010 ppm, 40% of sensors had errors greater than {+-}75 ppm and 31% of sensors has errors greater than {+-}100 ppm. At 760 ppm, 47% of sensors ...
Date: March 17, 2010
Creator: Fisk, William J.; Sullivan, Douglas P.; Faulkner, David & Eliseeva, Ekaterina
Partner: UNT Libraries Government Documents Department

Contam airflow models of three large buildings: Model descriptions and validation

Description: Airflow and pollutant transport models are useful for several reasons, including protection from or response to biological terrorism. In recent years they have been used for deciding how many biological agent samplers are needed in a given building to detect the release of an agent; to figure out where those samplers should be located; to predict the number of people at risk in the event of a release of a given size and location; to devise response strategies in the event of a release; to determine optimal trade-offs between sampler characteristics (such as detection limit and response time); and so on. For some of these purposes it is necessary to model a specific building of interest: if you are trying to determine optimal sampling locations, you must have a model of your building and not some different building. But for many purposes generic or 'prototypical' building models would suffice. For example, for determining trade-offs between sampler characteristics, results from one building will carry over other, similar buildings. Prototypical building models are also useful for comparing or testing different algorithms or computational pproaches: different researchers can use the same models, thus allowing direct comparison of results in a way that is not otherwise possible. This document discusses prototypical building models developed by the Airflow and Pollutant Transport Group at Lawrence Berkeley National Laboratory. The models are implemented in the Contam v2.4c modeling program, available from the National Institutes for Standards and Technology. We present Contam airflow models of three virtual buildings: a convention center, an airport terminal, and a multi-story office building. All of the models are based to some extent on specific real buildings. Our goal is to produce models that are realistic, in terms of approximate magnitudes, directions, and speeds of airflow and pollutant transport. The three models vary ...
Date: September 30, 2009
Creator: Black, Douglas R. & Price, Phillip N.
Partner: UNT Libraries Government Documents Department

Frequency agile laser safety & hazard analysis for the Sandia Remote Sensing System LIDAR.

Description: A laser safety and hazard analysis was performed for the Raytheon Frequency Agile Laser (FAL) to be used with the Sandia Remote Sensing System (SRSS) B-70 Trailer based on the 2007 version of the American National Standards Institute's (ANSI) Standard 136.1, for Safe Use of Lasers and the 2005 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. The B-70 SRSS LIDAR system is a portable platform, which is used to perform laser interaction experiments and tests at various national test sites.
Date: May 1, 2009
Creator: Augustoni, Arnold L.
Partner: UNT Libraries Government Documents Department

Measuring Outdoor Air Intake Rates into Existing Building

Description: Practical and accurate technologies are needed for continuously measuring and controlling outdoor air (OA) intake rates in commercial building heating, ventilating, and air conditioning (HVAC) systems. This project evaluated two new measurement approaches. Laboratory experiments determined that OA flow rates were measurable with errors generally less than 10 percent using electronic air velocity probes installed between OA intake louver blades or at the outlet face of louvers. High accuracy was maintained with OA flow rates as low as 15 percent of the maximum for the louvers. Thus, with this measurement approach HVAC systems do not need separate OA intakes for minimum OA supply. System calibration parameters are required for each unique combination of louver type and velocity sensor location but calibrations are not necessary for each system installation. The research also determined that the accuracy of measuring OA flow rates with velocity probes located in the duct downstream of the intake louver was not improved by installing honeycomb airflow straighteners upstream of the probes. Errors varied with type of upstream louver, were as high as 100 percent, and were often greater than 25 percent. In conclusion, use of electronic air velocity probes between the blades of OA intake louvers or at the outlet face of louvers is a highly promising means of accurately measuring rates of OA flow into HVAC systems. The use of electronic velocity probes downstream of airflow straighteners is less promising, at least with the relatively small OA HVAC inlet systems employed in this research.
Date: April 16, 2009
Creator: Fisk, William; Sullivan, Douglas; Cohen, Sebastian & Han, Hwataik
Partner: UNT Libraries Government Documents Department