Commenced in January 2007
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Thermal Comfort and Energy Saving Evaluation of a Combined System in an Office Room Using Displacement Ventilation

Authors: A. Q. Ahmed, S. Gao


In this paper, the energy saving and human thermal comfort in a typical office room are investigated. The impact of a combined system of exhaust inlet air with light slots located at the ceiling level in a room served by displacement ventilation system is numerically modelled. Previous experimental data are used to validate the Computational Fluid Dynamic (CFD) model. A case study of simulated office room includes two seating occupants, two computers, two data loggers and four lamps. The combined system is located at the ceiling level above the heat sources. A new method of calculation for the cooling coil load in Stratified Air Distribution (STRAD) system is used in this study. The results show that 47.4% energy saving of space cooling load can be achieved by combing the exhaust inlet air with light slots at the ceiling level above the heat sources.

Keywords: Air conditioning, Displacement ventilation, Energy saving, Thermal comfort.

Digital Object Identifier (DOI):

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[1] S. Riffat, X. Zhao, P. Doherty, Review of research into and application of chilled ceilings and displacement ventilation systems in Europe, International Journal of Energy Research, 28 (2004) 257-286.
[2] H. Skistad, Displacement ventilation, Research Studies Press, 1994.
[3] K. J. Loudermilk, Underfloor air distribution solutions for open office applications, Transactions-American Society of Heating Refrigerating and Air Conditioning Engineers, 105 (1999) 605-613.
[4] H.-J. Park, D. Holland, The effect of location of a convective heat source on displacement ventilation: CFD study, Building and environment, 36 (2001) 883-889.
[5] L. Tian, Z. Lin, Q. Wang, Comparison of gaseous contaminant diffusion under stratum ventilation and under displacement ventilation, Building and Environment, 45 (2010) 2035-2046.
[6] J.B. Olivieri, T. Singh, effect of supply and return air outlets on stratification / energy consumption ASHRAE Transaction 1, 188 (1982).
[7] R. L. Gorton, H. M. Bagheri, "Determination of Performance Characteristics of a System Designed for Stratified Cooling in Operation during the Heating Season, (1986).
[8] J. C. Lam, A. L. Chan, CFD analysis and energy simulation of a gymnasium, Building and Environment, 36 (2001) 351-358.
[9] A. Awad, R. Calay, O. Badran, A. Holdo, An experimental study of stratified flow in enclosures, Applied Thermal Engineering, 28 (2008) 2150-2158.
[10] M. Filler, Best practices for underfloor air systems, ASHRAE journal, 46 (2004) 39-46.
[11] G. Hunt, P. Linden, The fluid mechanics of natural ventilation— displacement ventilation by buoyancy-driven flows assisted by wind, Building and Environment, 34 (1999) 707-720.
[12] R. Calay, B. Borresen, A. Holdø, Selective ventilation in large enclosures, Energy and buildings, 32 (2000) 281-289.
[13] J. Zheng, Q. Chen, K. Lee, Establishment of design procedures to predict room airflow requirements in partially mixed room air distribution systems, ASHRAE Research Project (RP-1522) Final Report, (2012).
[14] S. Holmberg, Q. Chen, Air flow and particle control with different ventilation systems in a classroom, Indoor air, 13 (2003) 200-204.
[15] X. Hongtao, G. Naiping, N. Jianlei, A method to generate effective cooling load factors for stratified air distribution systems using a floorlevel air supply, HVAC&R Research, 15 (2009) 915-930.
[16] Y. Cheng, J. Niu, N. Gao, Stratified air distribution systems in a large lecture theatre: A numerical method to optimize thermal comfort and maximize energy saving, Energy and Buildings, 55 (2012) 515-525.
[17] FLUENT, A. Theory Guide, 2011.
[18] A. Makhoul, K. Ghali, N. Ghaddar, Desk fans for the control of the convection flow around occupants using ceiling mounted personalized ventilation, Building and Environment, 59 (2013) 336-348.