ASHRAE Journal - ACMA Supplement - Fall 2013 - 23

Engineering of Concordia University, Montreal, Canada. Dr. Wang compared the energy performance of an air curtain mounted over a single-entry door versus a vestibule using an integration of three types of modeling software. Using ANSYS Fluent CFD software, Dr. Wang found that an air curtain reduced air infiltration significantly across a building entrance door under various pressure conditions. The entire building annual energy usage then was determined using TRNSYS energy modeling software and CONTAM software for modeling building air pressure and infiltration. The results verified that the air curtain allowed less infiltration than a vestibule for a given building. The study found that in all of the climate zones where the IECC currently requires vestibules, an air curtain was equally effective or better at energy savings. To model the air curtain in a whole-building simulation, two steps were necessary: First, three door setups were used to determine the amount of air infiltration through the building entrance: 1. Single door without a vestibule or air curtain (hereafter, a single door) 2. Single door equipped with an air curtain (hereafter, an air curtain door) 3. A vestibule with two sets of doors (hereafter, a vestibule door) 1,146 kWh – 18,986 kWh in energy savings, with greater performance achieved in colder climate zones. The study illustrated that heating efficiency accounted for the air curtain door’s major savings. Because no changes were made to the operating characteristics of the air curtain, total savings in Zones 1 and 2 were marginal, or 0.0% – 0.1% (81 kWh ~ 132 kWh) when compared to the single door. The study also found that building entrance orientation, building pressure, and frequency of door usage all affect air infiltration/ exfiltration, and the resultant energy performance of the air curtain door. In particular, the effects of building entrance orientation and the balance of the HVAC system were shown to be as important as the frequency of door usage. Dr. Wang’s final report can be downloaded at no charge at: www. amca.org/publications/air_curtain_study.aspx. RefeRences 1. 2. 3. Second, research determined the impact of air infiltrations on the whole building and annual energy use for the three different door setups. Infiltration through the single door and vestibule door setups was calculated by a commonly used orifice equation model, which considers the amount of infiltration to depend linearly on a power law function of the pressure difference across the door. Yuill (1996)2 conducted extensive experimental studies to provide the orifice equation models for both single and vestibule doors based on door usage frequency, geometry, and pressure difference across a door. The infiltration model for the air curtain door was determined using the method similar to that in Yuill’s study, in conjunction with the multi-model CFD program described above. findings For the modeled DOE3 medium office building, the major conclusions demonstrated the annual energy use of the whole building with the air curtain installed is less in all of the climate zones. Energy use is less than the single door in Climate Zones 1 – 2, and less than the vestibule door in Climate Zones 3 – 8. Additionally, the modeled air curtain door reduces air infiltration significantly under the same conditions when compared to either the single door or the vestibule door. The modeled air curtain door also provided comparable performance to the modeled vestibule door for climate Zones 3–8. Compared to the vestibule door, the air curtain door can reduce energy use by 0.3% to 2.2% for Zones 3 – 8, corresponding to w w w. a m c a . o r g a m c a I n t e r nat I o na l Wang, L. 2013. “Investigation of the Impact of Building Entrance Air Curtain on Whole Building Energy Use.” http:// www.amca.org/feg/research-and-whitepapers.aspx. Yuill, G. K. 1996. “Impact of High Use Automatic Doors on Infiltration.” ASHRAE RP-763. Cho, H., K. Gowri, and B. Liu. 2010. “Energy saving impact of ASHRAE 90.1 vestibule requirements: modeling of air infiltration through door openings.” Oak Ridge, Tenn., Pacific Northwest National Laboratory: 47. Benefits of air curtains Approved as an alternative to vestibules in the 2012 IgCC, air curtains make egress in an emergency exit situation safer and faster by providing clear, uninhibited flow to the traffic passing through it, while still saving energy during heating and cooling seasons. Alternatively, with vestibules, building occupants would need to pass through two sets of doors instead of one. An additional benefit of using an air curtain is a cleaner indoor air environment. Air curtains can reduce the infiltration of dirt, fumes, and debris, and repel flying insects. As recognized by ANSI/NSF Standard 37: Air Curtains for Entranceways in Food and Food Service Establishments, they are approved for the food service industry to control insects at customer entry doors, service windows, and delivery doors. Numerous studies have evaluated the effectiveness of air curtains in terms of providing a separation between spaces. Air curtains consistently meet the performance of or outperform vestibules in energy savings. Recent studies take advantage of modern technology to evaluate air curtains’ efficiency and effectiveness, while considering installation, operating costs, and maintenance costs. inmotion Fall 2013 23 http://www.amca.org/publications/air_curtain_study.aspx http://www.amca.org/publications/air_curtain_study.aspx http://www.amca.org/feg/research-and-whitepapers.aspx http://www.amca.org/feg/research-and-whitepapers.aspx http://WWW.AMCA.ORG

ASHRAE Journal - ACMA Supplement - Fall 2013

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