Experimental and Numerical Study of A/C Outletsand Its Impact on Room Airflow Characteristics
This paper investigates experimental and numerical study of the airflow characteristics for vortex, round and square ceiling diffusers and its effect on the thermal comfort in a ventilated room. Three different thermal comfort criteria namely; Mean Age of the Air (MAA), ventilation effectiveness (E), and Effective Draft Temperature (EDT) have been used to predict the thermal comfort zone inside the room. In experimental work, a sub-scale room is set-up to measure the temperature field in the room. In numerical analysis, unstructured grids have been used to discretize the numerical domain. Conservation equations are solved using FLUENT commercial flow solver. The code is validated by comparing the numerical results obtained from three different turbulence models with the available experimental data. The comparison between the various numerical models shows that the standard k-ε turbulence model can be used to simulate these cases successfully. After validation of the code, effect of supply air velocity on the flow and thermal field could be investigated and hence the thermal comfort. The results show that the pressure coefficient created by the square diffuser is 1.5 times greater than that created by the vortex diffuser. The velocity decay coefficient is nearly the same for square and round diffusers and is 2.6 times greater than that for the vortex diffuser.
[1] A. F. Alfahaid, Effects of ventilation on human thermal comfort in rooms, Ph. D Thesis, old dominion university, Norfolk, Virginia, 2000.
[2] A. H. Al-Hamed, Determining Velocity, Temperature and Occupancy Comfort within a 3-D. Room, M.A. Thesis, King Fand University, Saudi Arabia, 1990.
[3] S. A. Al-Sanea, M. F. Zedan, and M. B. Al-Harbi, "Effect of supply Reynolds number and room aspect ratio on flow and ceiling heat transfer coefficient for mixing ventilation", International Journal of Thermal Sciences, vol. 54, pp. 176-187, 2012.
[4] H. B. Awbi, Ventilation of Buildings, Second edition, Spon Press, 2003.
[5] ASHRAE Handbook. Fundamentals, 2008.
[6] ASHRAE Standards, Standard 55, 1992.
[7] J. Abanto, D. Barrero, M. Reggioa, and B. Ozell, "Airflow modeling in a computer room", Building and Environment, Vol. 39, pp. 1393-1402, 2004.
[8] M. Bartak, M. Cermak, J. A. Clarke, J. Denev, F. Drkal, M. Lain, I. A. Macdonald, M. Majer, and P. Stankov, "Experimental and numerical study of local mean age of air", seventh International IBPSA Conference, Rio de Janeiro, Brazil, August 13-15, 2001.
[9] G. Gan, "Evaluation of room air distribution systems using computational fluid dynamics", Energy and Buildings, Vol. 23, pp. 83¬93, 1995.
[10] J. D. Spitler, An experimental investigation of air flow and convective heat transfer in enclosures having large ventilative flow rates, Ph.D. Thesis, University of Illinois at Urbana-Champaign, 1990.
[11] P. V. Nielsen., "Velocity distribution in a room ventilated by displacement ventilation and wall-mounted air terminal devices", Energy and Buildings, Vol. 31, no. 3, pp. 179-187, 2000.
[12] E. Lobutova, C. Resagk, and T. Putze, “Investigation of large scale
circulations in room airflows using three-dimensional particle tracking
velocimetry”, Building and Environment, Vol. 45, pp. 1653-1662, 2010.
[13] J. D. Posner, C. R. Buchanan, and D. Dunn-Rankin, “Measurement and
prediction of indoor air flow in a model room”, Energy and Building,
Vol. 35, pp. 515-526, 2003.
[14] J. Srebric, and Q. Chen, “Simplified numerical models for complex air
supply diffusers”, HVAC&R Research, Vol. 8(3), pp. 277-294, 2002.
[15] L. Zhou, and F. Haghighat, “simplified method for modeling swirl
diffusers”, Department of Building, Civil and Environmental
Engineering Concordia University, Montreal, Canada, 2007.
[16] G. Einberga, and Hagstrom K.,” CFD modeling of an industrial air
diffuser predicting velocity and temperature in the near zone”, Building
and Environment, Vol. 40, pp.601–615, 2005.
[17] Fluent Inc., User’s Guide for Fluent/UNS, Release 6.3, Lebanon, USA,
2006.
[18] S. C. Hu, “Airflow characteristics in the outlet region of a vortex room
air diffuser, Building and Environment, Vol. 38, pp.553-561, 2003.
[19] J. L. Lumley, and Tennekes H., A First Course in Turbulence, MIT
Press, London, England, 1972.
[20] T. B. Gatski, Hussaini M. Y., and Lumley J. L., Simulation and
Modeling of Turbulent Flows”, New York, Oxford, Oxford University
Press, 1996.
[21] J. H. Ferziger, and Peric M., Computational Methods for Fluid
Dynamics. Springer Verlag, Berlin, Germany, 1996.
[22] Shakerin S., and Miller P. L., “Experimental study of vortex diffusers,
University of the Pacifica”, November 1995.
[1] A. F. Alfahaid, Effects of ventilation on human thermal comfort in rooms, Ph. D Thesis, old dominion university, Norfolk, Virginia, 2000.
[2] A. H. Al-Hamed, Determining Velocity, Temperature and Occupancy Comfort within a 3-D. Room, M.A. Thesis, King Fand University, Saudi Arabia, 1990.
[3] S. A. Al-Sanea, M. F. Zedan, and M. B. Al-Harbi, "Effect of supply Reynolds number and room aspect ratio on flow and ceiling heat transfer coefficient for mixing ventilation", International Journal of Thermal Sciences, vol. 54, pp. 176-187, 2012.
[4] H. B. Awbi, Ventilation of Buildings, Second edition, Spon Press, 2003.
[5] ASHRAE Handbook. Fundamentals, 2008.
[6] ASHRAE Standards, Standard 55, 1992.
[7] J. Abanto, D. Barrero, M. Reggioa, and B. Ozell, "Airflow modeling in a computer room", Building and Environment, Vol. 39, pp. 1393-1402, 2004.
[8] M. Bartak, M. Cermak, J. A. Clarke, J. Denev, F. Drkal, M. Lain, I. A. Macdonald, M. Majer, and P. Stankov, "Experimental and numerical study of local mean age of air", seventh International IBPSA Conference, Rio de Janeiro, Brazil, August 13-15, 2001.
[9] G. Gan, "Evaluation of room air distribution systems using computational fluid dynamics", Energy and Buildings, Vol. 23, pp. 83¬93, 1995.
[10] J. D. Spitler, An experimental investigation of air flow and convective heat transfer in enclosures having large ventilative flow rates, Ph.D. Thesis, University of Illinois at Urbana-Champaign, 1990.
[11] P. V. Nielsen., "Velocity distribution in a room ventilated by displacement ventilation and wall-mounted air terminal devices", Energy and Buildings, Vol. 31, no. 3, pp. 179-187, 2000.
[12] E. Lobutova, C. Resagk, and T. Putze, “Investigation of large scale
circulations in room airflows using three-dimensional particle tracking
velocimetry”, Building and Environment, Vol. 45, pp. 1653-1662, 2010.
[13] J. D. Posner, C. R. Buchanan, and D. Dunn-Rankin, “Measurement and
prediction of indoor air flow in a model room”, Energy and Building,
Vol. 35, pp. 515-526, 2003.
[14] J. Srebric, and Q. Chen, “Simplified numerical models for complex air
supply diffusers”, HVAC&R Research, Vol. 8(3), pp. 277-294, 2002.
[15] L. Zhou, and F. Haghighat, “simplified method for modeling swirl
diffusers”, Department of Building, Civil and Environmental
Engineering Concordia University, Montreal, Canada, 2007.
[16] G. Einberga, and Hagstrom K.,” CFD modeling of an industrial air
diffuser predicting velocity and temperature in the near zone”, Building
and Environment, Vol. 40, pp.601–615, 2005.
[17] Fluent Inc., User’s Guide for Fluent/UNS, Release 6.3, Lebanon, USA,
2006.
[18] S. C. Hu, “Airflow characteristics in the outlet region of a vortex room
air diffuser, Building and Environment, Vol. 38, pp.553-561, 2003.
[19] J. L. Lumley, and Tennekes H., A First Course in Turbulence, MIT
Press, London, England, 1972.
[20] T. B. Gatski, Hussaini M. Y., and Lumley J. L., Simulation and
Modeling of Turbulent Flows”, New York, Oxford, Oxford University
Press, 1996.
[21] J. H. Ferziger, and Peric M., Computational Methods for Fluid
Dynamics. Springer Verlag, Berlin, Germany, 1996.
[22] Shakerin S., and Miller P. L., “Experimental study of vortex diffusers,
University of the Pacifica”, November 1995.
@article{"International Journal of Mechanical, Industrial and Aerospace Sciences:53675", author = "Mohammed A. Aziz and Ibrahim A. M. Gad and El Shahat F. A. Mohammed and Ramy H. Mohammed", title = "Experimental and Numerical Study of A/C Outletsand Its Impact on Room Airflow Characteristics", abstract = "This paper investigates experimental and numerical study of the airflow characteristics for vortex, round and square ceiling diffusers and its effect on the thermal comfort in a ventilated room. Three different thermal comfort criteria namely; Mean Age of the Air (MAA), ventilation effectiveness (E), and Effective Draft Temperature (EDT) have been used to predict the thermal comfort zone inside the room. In experimental work, a sub-scale room is set-up to measure the temperature field in the room. In numerical analysis, unstructured grids have been used to discretize the numerical domain. Conservation equations are solved using FLUENT commercial flow solver. The code is validated by comparing the numerical results obtained from three different turbulence models with the available experimental data. The comparison between the various numerical models shows that the standard k-ε turbulence model can be used to simulate these cases successfully. After validation of the code, effect of supply air velocity on the flow and thermal field could be investigated and hence the thermal comfort. The results show that the pressure coefficient created by the square diffuser is 1.5 times greater than that created by the vortex diffuser. The velocity decay coefficient is nearly the same for square and round diffusers and is 2.6 times greater than that for the vortex diffuser.
", keywords = "Ceiling diffuser, Thermal Comfort, MAA, EDT, Fluent, Turbulence model.", volume = "6", number = "11", pages = "2374-9", }
