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Energy-Saving Measures in a Classroom Using Low Pressure Drop Ceiling Supply Device: A Field Study
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.ORCID iD: 0000-0003-2023-689x
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.ORCID iD: 0000-0003-3472-4210
2016 (English)In: 2016 ASHRAE Winter Conference Papers, ASHRAE, 2016Conference paper, Published paper (Refereed)
Abstract [en]

Between 1990 and 2006 the energy use by ventilation systems in Swedish schools doubled. This is explained by high airflows in schools because of the high occupant density. Studies show that 87% of Swedish schools use constant air volume (CAV), and it is estimated that a change to variable air volume (VAV) could save 0.12-0.33 TWh (4.1*10(12) - 1.1*10(13) Btu) per year. Therefore the aim of this study is to investigate whether it is possible to replace displacement ventilation (DV) with mixing ventilation (MV) to create a comfortable indoor climate in a typical classroom and at the same time decrease the energy use by using VAV and Low Pressure Drop Ceiling Supply Device (LPDCSD). The study used two LPDCSDs which consist of circular channels with 190/228 round jets placed in an interlocking pattern, with a horizontal one/two-way-direction. The field study was carried out in a school which is intended to be extensively renovated. The school currently has DV and CAV. The study was carried out by installing MV with LPDCSD in one of the typical classrooms. Several different air-flow rates were investigated using tracer-gas technology to measure the local mean age of the air in the occupied zone. Simultaneously, thermal comfort and vertical temperature gradients were measured in the room. The results show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low air-flow rates. Since the mixing of air is more or less the same in the entire occupied zone VAV can be used to reduce air-flow rate based on the desired CO2-level. Because of the number of students in each classroom and the fact that changes in air-flow rates have no significant effect on the degree of mixing, it is possible to reduce the air-flow rates for extended periods of time. Finally, since the LPDCSD has a lower pressure-drop than the currently used supply devices and it is possible to use VAV to lower the airflows in cases with reduced heat loads, it is possible to significantly reduce the energy usage in the school while maintaining the IAQ, increasing the thermal comfort and the available floor area of the occupied zone.

Place, publisher, year, edition, pages
ASHRAE, 2016.
Series
ASHRAE Conference Papers, ISSN 2378-2129
National Category
Energy Systems
Identifiers
URN: urn:nbn:se:hig:diva-27424ISI: 000427879200060ISBN: 978-1-939200-13-6 OAI: oai:DiVA.org:hig-27424DiVA, id: diva2:1225691
Conference
ASHRAE Winter Conference, 23-27 January 2016, Orlando, FL, USA
Available from: 2018-06-27 Created: 2018-06-27 Last updated: 2018-06-27Bibliographically approved

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Andersson, HaraldCehlin, MathiasMoshfegh, Bahram

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