Measurements of air temperatures close to a low-velocity diffuser in displacement ventilation using an infrared camera |
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| Affiliation: | 1. Division of Energy and Mechanical Engineering, Department of Technology, University of Gävle, S-801 76 Gävle, Sweden;2. Center for Built Environment, Division of Indoor Environment and Ventilation, Laboratory of Ventilation and Air Quality, University of Gävle, S-801 02 Gävle, Sweden;1. Texas A&M University, College Station, TX, United States;2. Price Industries, Winnipeg, Canada;1. Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, PR China;2. Key Laboratory for the Green Preparation and Application of Functional Materials, Ministry of Education, PR China;3. Faculty of Materials Science and Engineering, Hubei University, Wuhan 430062, PR China;1. National and Local Joint Engineering Research Center of Space Optoelectronics Technology, Changchun University of Science and Technology, Changchun, 130022, China;2. School of Electronics and Information Engineering, Changchun University of Science and Technology, Changchun, 130022, China;1. Toyota Central Research & Development Labs., Nagakute, Aichi 480 1192, Japan;2. Department of Electrical Engineering, Stanford University, Stanford, CA 94305, USA;1. Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas;2. Department of Physics and Astronomy, Rice University, Houston, Texas;3. Graduate School of Biomedical Sciences, The University of Texas, Houston, Texas;4. Department of Medical Physics, The Ottawa Hospital Cancer Centre, Ottawa, Ontario, Canada;5. Crystal Growth Division, Landauer, Inc, Stillwater, Oklahoma;1. Mechanical Engineering Department, Suez Canal University, Ismailia, Egypt;2. Mechanical Engineering Department, Alexandria University, Alexandria, Egypt;3. Mechanical Engineering Department, Arab Academy for Science, Technology and Maritime, Egypt |
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| Abstract: | The near zone of supply air diffusers is very critical for the indoor climate. Complaints of draft are often associated with low-velocity diffusers in displacement ventilation because the air is discharged directly into the occupied zone. Today, the knowledge of the near zone of these air supply diffusers is insufficient, causing an increased need for better measuring methods and representation of the occupied zone.A whole-field measuring technique has been developed by the authors for visualization of air temperatures and airflow patterns over a large cross-section. In this particular whole-field method, air temperatures are measured with an infrared camera and a measuring screen placed in the airflow. The technique is applicable to most laboratory and field test environments. It offers several advantages over traditional techniques; for example, it can record real-time images within large areas and capture transient events.The purpose of this study was to conduct a parameter and error analysis of the proposed whole-field measuring method applied to a flow from a low-velocity diffuser in displacement ventilation. A model of the energy balance, for a solid measuring screen, was used for analyzing the influence of different parameters on the accuracy of the method. The analysis was performed with respect to the convective heat transfer coefficient, emissivity, screen temperature and surrounding surface temperatures.Theoretically, the temperature difference between the screen and the ambient air was found to be 0.2–2.4 °C for the specific delimitation in the investigation. However, after applying correction the maximum uncertainty of the predicted air temperature was found to vary between 0.62 and 0.98 °C, due to uncertainties in estimating parameters used in the correction. The maximum uncertainty can be reduced to a great extent by estimating the convective heat transfer coefficient more accurately and using a screen with rather low emissivity. |
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