Investigation of efficient air pollutant removal using active flow control Lupita D. Montoya * , Denise C. Mauney, Wil V. Srubar III Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, 4001 Discovery Drive, SEEC S286A, UCB 607, Boulder, CO 80303-0607 USA article info Article history: Received 19 January 2017 Received in revised form 10 May 2017 Accepted 5 June 2017 Available online 7 June 2017 Keywords: Indoor air quality Synthetic jet actuator Titanium dioxide Nitrogen dioxide abstract Efficiency in maintaining indoor air quality is central to the operation of high-performance buildings. The purpose of this work was to investigate the effect of airflow velocities generated by a low-power annular, multi-orifice synthetic jet actuator (SJA) on the degradation rate of a model air pollutant, nitrogen di- oxide (NO 2 ), by a photocatalytic surface. In this study, the active flow fields generated by the SJA were first characterized, and the effect of SJA-to-wall distance was analyzed as the airflow impinged on a wall of varying surface textures. Second, the impact of flow characteristics, namely surface velocity and ve- locity distribution, on the removal rates of NO 2 by the photocatalytic surface was investigated in a closed chamber. Results showed that a SJA-to-wall (L) distance of 315 mm had the greatest reduction (damp- ening) on peak airflow velocities. Also, the surface with the highest roughness used in this study resulted in increased turbulence at the wall surface. The use of the SJA enhanced the removal rate of NO 2 compared to passive (control) conditions. Increases in air velocity, however, did not monotonically enhance the removal rate of NO 2 . The highest removal rate (k ¼ 0.0013 min 1 ) was measured at L ¼ 315 mm, where the highest velocity dampening was observed. It also corresponded to an average surface velocity of approximately 0.1 m/s across the photocatalytic surface. © 2017 Published by Elsevier Ltd. 1. Introduction High performance buildings require greater air tightness and, thus, increased need for indoor ventilation, which can lead to an overall increase in heating and cooling loads [1e4] especially as climate change effects increase [5]. Some modern building mate- rials and furnishings have also introduced a variety of pollutants, including volatile organic compounds (VOCs) as well as highly reactive molecules and radicals such as ozone, nitrous oxides, hy- droxyl radicals, and sulfur dioxides [6,7] into the indoor environ- ment. Reducing pollutant emissions from materials increases both actual and perceived indoor air quality [8,9]. Sick Building Syn- drome (SBS) is a term used to diagnose buildings where occupant exposure to indoor pollutants has led to negative health effects [10,11] and productivity losses. Studies have shown that improving indoor air quality in U.S. buildings can save $30 billion annually by reducing occupant sick days [12]. Traditionally, indoor air quality has been improved by increasing ventilation using energy-intensive central Heating Ventilation and Air Conditioning (HVAC) systems. Thus, methods and means to achieve acceptable building air quality without costly energy usage have become increasingly attractive. Task/ambient conditioning (TAC) systems, such as individually controlled under-floor air dis- tribution and desk-level supply air diffusers, have been proposed as alternatives for improving indoor air quality in buildings [13e17]. Sorptive and photocatalytic building materials have also been proposed as pollutant sinks that can alleviate energy demand on large-scale central systems particularly in geometrically complex interiors [14,18]. The use of low-energy devices like synthetic jet actuators for indoor air quality applications have also been pro- posed in the past [19,20]. 1.1. Synthetic jet actuators Considered zero net mass flux devices, synthetic jet actuators (SJAs) are mechanical devices used to generate air flows that require zero mass input and produce non-zero momentum output [21]. Additional advantages of SJAs over conventional fans are that they can be mounted to surfaces, require less space, and provide * Corresponding author. E-mail address: lupita.montoya@colorado.edu (L.D. Montoya). Contents lists available at ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv http://dx.doi.org/10.1016/j.buildenv.2017.06.012 0360-1323/© 2017 Published by Elsevier Ltd. Building and Environment 122 (2017) 134e144