Ceiling personalized ventilation combined with desk fans for reduced direct and indirect cross-contamination and efficient use of office space Carine Habchi a , Kamel Ghali a , Nesreen Ghaddar a,⇑ , Walid Chakroun b , Sorour Alotaibi b a Mechanical Engineering Department, Faculty of Engineering and Architecture, American University of Beirut, P.O. Box 11-0236, Beirut 1107-2020, Lebanon b Mechanical Engineering Department, College of Engineering & Petroleum, Kuwait University, Khaldiya, P.O. Box 5969, Safat 13060, Kuwait article info Article history: Received 6 August 2015 Accepted 24 December 2015 Available online 7 January 2016 Keywords: Ceiling personalized ventilation Indoor air quality Direct and indirect cross-contamination Space occupancy density Energy savings abstract Crowded offices with short distances separating workers’ stations increase the probability of respiratory cross-infection via two different paths. One path is the contaminant transmission through air by direct inhalation and the other is through the body contact of contaminated surfaces and walls. Mixed ventila- tion principles used today reduces the probability of cross contamination by increasing the distance between the stations challenging the efficient use of the space or by supplying more fresh air in the space which is energy inefficient. In this work, new cooling and ventilation configuration is studied by modeling using computational fluid dynamics with consideration of space occupancy density while providing good indoor air quality. The configuration considers a ceiling personalized ventilation system equipped with desk fans. The abil- ity of the computational fluid dynamics model in computing the thermal, velocity and concentration fields was validated by experiments and published data. The main objective of the performed experi- ments was to ensure that the developed computational fluid dynamics model can capture the effect of the desk fan flow rate on particle behavior. The studied system is found to provide acceptable indoor air quality at shorter distance between the occupants compared to the mixing system at considerable energy savings. By optimizing the design of the proposed personalized ventilation system, the occupancy density in an office is enhanced to 8 m 2 per occupant compared to 12 m 2 per occupant for conventional mixing system while maintaining better indoor air quality at significant decrease in the energy consumption. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Suspended aerosol particles may present risks to the human health [1] and are regarded as an essential contaminant in the air [2,3]. Epidemiological studies revealed significant relation between dangerous human diseases and particle pollution where increased particle concentration increased the risk of cardiovascular prob- lems [4], lung cancer [5], asthma and a variety of respiratory infec- tions [6]. Literature studies have mainly focused on outdoor air pollution, but more attention has recently been directed to indoor particles’ exposure [7,8] where people spend the majority of their time [9]. Offices in particular are one of the critical indoor spaces where the likelihood of their exposure to airborne pathogens is very high [10]. With the increase of energy consumption for indoor environmental quality enhancement [11,12], there is a need to use ventilation configurations that are effective [13,14] while main- taining good IAQ. Cross-infection between workers can take place via different paths: direct inhalation and by contact of contaminated surfaces. Infected persons release droplets that probably contain viruses or bacteria that expose healthy persons to infection by either direct inhalation [15] or indirectly via a contaminated surface- to-hand-to-mouth contact [16]. Researchers’ studies on cross- contamination investigated mainly the probability of infection due to the direct inhalation. However, few studies considered the indirect path via the contact of contaminated surfaces. Reducing locally contaminants’ concentration within the air inhaled by occu- pants does not necessarily indicate a clean non-infectious environ- ment for the office occupants. Pathogens such as bacteria and viruses are able to survive on surfaces for long periods [17] resulting in a higher probability of being transmitted to susceptible occupants [18,19]. In designing a multi-station office space, the distance between the work-stations constitutes one of the main factors affecting http://dx.doi.org/10.1016/j.enconman.2015.12.067 0196-8904/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +961 1 350000x3594. E-mail address: farah@aub.edu.lb (N. Ghaddar). Energy Conversion and Management 111 (2016) 158–173 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman