Numerical Investigation of Indoor Air Quality and Thermal Comfort in a Ventilated Room

Authors: Ramy H. Mohammed

Abstract:

Understanding the behavior of airflow in a room is essential for building designers to provide the most efficient design of ventilation system, and having acceptable indoor air quality. This trend is the motive to solve the relationship between airflow parameters and thermal comfort. This paper investigates airflow characteristics, indoor air quality (IAQ), and the thermal comfort (TC) in a ventilated room with a displacement ventilation system using three dimensional CFD code [AirPak 2.0.6]. After validation of the code, a numerical study is executed for a typical room with dimensions of 5m by 3m by 3m height according to a variety of supply air velocities, supply air temperature and supply air relative humidity. The finite volume method and the indoor zero equation turbulence models are employed for solving the governing equations numerically. The temperature field and the mean age of air (MAA) in the modeled room for a displacement ventilation system are determined according to a variety of the above parameters. The variable air volume (VAV) systems with different supply air velocity are applicable to control room air temperature for a displacement ventilation system.

Keywords: Displacement ventilation, AirPak, Indoor zero equation, MAA.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1089513

References:

[1] Cehlin M, Moshfegh B, Sandberg M. "Measurements of air temperatures close to a low velocity diffuser in displacement ventilation using infrared camera”. Energy and Buildings; vol.34; p 687-98, 2002.
[2] Cehlin M, Sandberg, M. "Monitoring of a low-velocity air jet using computed tomography”. In: Proceedings of the eight international conference on air distribution in rooms; p 361-4, 2002.
[3] Hassani V, Stetz M. "Application of infrared thermography to room air temperature measurements”. Proceedings ASHRAE Transactions; Part 2, p. 1238-47, 1994.
[4] Linden E, Todde V, Sandberg, M. "Indoor Low Speed Air Jet Flow: 3-dimensional Particle Streak Velocimetry”. Proceedings of the sixth international conference on air distribution in rooms, vol.2; p. 56-76, 1998.
[5] Müller D, Renz U. "A low cost particle streak tracking system (PST) and a new approach to three dimensional airflow velocity measurements”. Roomvent’98, vol.2; p.593-600, 1998.
[6] Price P, Fischer M, GadgilA,Sextro R. "Algorithm for rapid gas concentration tomography”. Lawrence Berkeley National Laboratory; LBNL Report 46236, 2000.
[7] Todd L, Farhat S, Mottus K, Mihlan G. "Experimental evaluation of an environmental CAT scanning system for mapping chemicals in air in real-time”. Applied Occupational and Environmental Hygiene, vol; 16, p.45-55, 2001.
[8] Sun Y, Zhang Y. "An overview of room air motion measurement”, technology and application. HVAC & R Research, vol; 13, p.929-50, 2007.
[9] Sandberg M. "Whole-field measuring methods in ventilated rooms”. HVAC & R Researchl, vol; 13, p.951-70, 2007.
[10] Cehlin, M. Moshfegh, B. "Numerical modeling of a complex diffuser in a room with displacement ventilation”. Building and Environment, vol; 45, p. 2240 – 2252, 2010.
[11] Huizenga, C., Abbaszadeh, S., Zagreus L., and Arens, E. "Air quality and thermal comfort in office buildings: Results of a large indoor environmental quality survey”. Proceedings of Healthy Buildings, June 4-8, University of Porto, Lisbon, p. 393-397, 2006.
[12] Ye, X.J., Zhu. Z.P., Lian. Z.W, Liu. H.M, Li, C.Z., and Liu, Y.M. "Field study of a thermal environment and adaptive model in Shanghai”. Indoor Air, vol 16, p. 320-326, 2006.
[13] ASHRAE Handbook: Applications, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA, 2003.
[14] Hashimoto, Y. "Numerical study on airflow of n office room with displacement ventilation system”. Ninth international IBPSA conference, Montreal, Canada, 2005
[15] ASHRAE standard 55-2004: ASHRAE thermal environmental conditions for human occupancy. Atlanta, GA, USA: American Society of Heating, Refrigerating and Air Conditioning Engineers; 2004.
[16] ISO.ISO7730: moderate thermal environments determination of the PMV and PPD indices and specification of the conditions for thermal comfort. Geneva: International Organization for Standardization, 1994.
[17] Sandberg, M. Sjöberg, M. "The use of moments for assessing air quality in ventilated rooms”. Building and Environment, vol 18; p.181–197, 1983.
[18] Federspiel, C.C. "Air change effectiveness: theory and calculation methods”. Indoor Air, vol 9; p. 47–56, 1999.
[19] Vivian C, Pierre-Sylvain M. "Computational fluid dynamics (CFD) modeling of local mean age of air Distribution in forced-ventilation food plants”. Journal of Food Engineering, vol 90; p. 90–10, 2009.
[20] Simons, M.W., Waters, J.R. "Ventilation effectiveness parameters resulting from mechanical ventilation with recirculation”. International Journal of ventilation 1(2), 119–126, 2002.
[21] Spitler, J. D. "An Experimental Investigation of Airflow and Convective Transfer in Enclosures Having Large Ventilative Flow Rates”. Ph.D. Thesis, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA, 1990.
[22] Nielsen, P.V., "Flow in Air Conditioned Rooms”. Ph.D. Thesis, Nordberg Denmark, 1974.
[23] Baker, A.J., Williams, P.T. and Kelso, R.M., "Numerical Calculation of Room Air Motion - part 1: Math, Physics and CFD Modeling," ASHRAE Transactions. Vol.100; Part1, p.514-530.
[24] Ahmed f. Alfahaid, "Effects of ventilation on human Thermal comfort in rooms”, Ph.D. Thesis, Old Dominion University, December 2000.
[25] Chen, Q. "Indoor Airflow. Air Quality and Energy Consumption of Buildings”, Ph.D. Thesis, Delft University of Technology, Delft, the Netherlands, 1988.
[26] Niu, J. "Modeling of Cooled-Ceiling Air Conditioning Systems”. Ph.D. Thesis, Delft University of Technology, Delft, Netherlands, 1994.
[27] Peng. X. "Modeling of Indoor Thermal Conditions for Comfort Control in Buildings”. Ph.D. Thesis, Delft University of Technology, Delft, the Netherlands, 1996.
[28] Nielsen, P.V. "Description of supply openings in numerical models for room air distribution”. ASHRAE Transactions, Vol. 98; pp. 963–71, 1992.
[29] Weiran, X. "New turbulence models for indoor airflow simulation”. Ph.D.thesis, Massachusetts Institute of Technology, USA, 1998.
[30] Chaoqun, L. "Multi grid method and application in computational fluid dynamics”. Beijing: Tsinghua University Press, 1995.
[31] Fluent Inc. 2001 "Getting Started with Airpak 2”.
[32] Chen, Q., Xu, W. "A zero-equation turbulence model for indoor airflow simulation”. Energy and Buildings, Vol. 28; pp.137-144, 1998.
[33] Etheridge D, Sandberg M. "Building ventilation, theory and measurement”. England: John Wiley and Sons Ltd., 1996.