Application of CFD for Air Flow Analysis underneath Natural Ventilation with Forced Convection in Roof Attic

In research on natural ventilation, and passive cooling with forced convection, is essential to know how heat flows in a solid object and the pattern of temperature distribution on their surfaces, and eventually how air flows through and convects heat from the surfaces of steel under roof. This paper presents some results from running the computational fluid dynamic program (CFD) by comparison between natural ventilation and forced convection within roof attic that is received directly from solar radiation. The CFD program for modeling air flow inside roof attic has been modified to allow as two cases. First case, the analysis under natural ventilation, is closed area in roof attic and second case, the analysis under forced convection, is opened area in roof attic. These extend of all cases to available predictions of variations such as temperature, pressure, and mass flow rate distributions in each case within roof attic. The comparison shows that this CFD program is an effective model for predicting air flow of temperature and heat transfer coefficient distribution within roof attic. The result shows that forced convection can help to reduce heat transfer through roof attic and an around area of steel core has temperature inner zone lower than natural ventilation type. The different temperature on the steel core of roof attic of two cases was 10-15 oK.

Authors:

• C. Nutphuang
• S. Chirarattananon
• V.D. Hien

Keywords:

• CFD program
• natural ventilation
• forcedconvection
• heat transfer
• air flow.

References:

[1] Cezar O.R. Negriio., "Integration of computational fluid dynamics with
building thermal and mass flow simulation", Energy and
Buildings,1998;27: 155-165.
[2] Feustel Helmut E., "COMIS-an international multizone air-flow and
contaminant transport mode", Energy and Buildings, 30(1999):3-18..
[3] Helmut E. Feustel., "COMISÔÇöan international multizone air-flow and
contaminant transport model",Energy and Buildings ,30(1999):3-18.
[4] Ren Zhen, Stewart John., "Simulating air flow and temperature
distribution inside buildings using a modified version of COMIS with
sub-zonal divisions", Energy and Buildings, 2003;35:257-271
[5] Zhengen Ren, John, "Stewart.Simulating air flow and temperature
distribution inside buildings using a modified version of COMIS with
sub-zonal division", Energy and Buildings ,35,(2003):257-271.
[6] Christian Inard , Hassan Bouia , Pascal Dalicieux., "Prediction of air
temperature distribution in buildings with a zonal model", Energy and
Buildings 1996;24:125-132.
[7] John Stewart, Zhengen Ren., "COwZÔÇöA subzonal indoor airflow,
temperature and contaminant dispersion model", Building and
Environment, 41, (2006): 1631-1648.
[8] Meir Teitel and Josef Tanny., "Heat Fluxes and Airflow Patterns T
hrough Roof Windows in a Naturally Ventilated Enclosure", Flow,
Turbulence and Combustion ,2005;74:21-47.
[9] L. Susanti a, H. Hommab, H. Matsumoto b, Y. Suzuki c, M. Shimizu.
"A laboratory experiment on natural ventilation through a roof cavity
for reduction of solar heat gain", Energy and Buildings, 2008;40:2196-
2206.
[10] Sunwoo Lee, Sang Hoon Park, Myong Souk Yeo, Kwang Woo Kim.
"An experimental study on airflow in the cavity of a ventilated roof",
Building and Environment ,2009;44:1431-1439.
[11] Omar S. Asfour, Mohamed B. Gadi.," Using CFD to investigate
ventilation characteristics of vaults as wind-inducing devices in
buildings", Applied Energy 85 (2008):1126-1140.
[12] Vu Duc Hien and Surapong Chirarattananon,(2006). Building Energy
Simulation Program-BESim. "A presentation published in the
Proceedings of the training workshop on Daylight under Tropical Sky",
17-19 May 2006, AIT Conference Center, Asian Institute of
Technology(AIT), Bangkok, Thailand.