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Research Papers

3D Numerical Simulation of the Transient Thermal Behavior of a Simplified Building Envelope Under External Flow

[+] Author and Article Information
F. Barmpas, N. Moussiopoulos

Department of Mechanical Engineering, Laboratory of Heat Transfer and Environmental Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece

D. Bouris1

Department of Engineering and Management of Energy Resources, University of Western Macedonia, Bakola and Sialvera, 50100 Kozani, Greecedmpouris@uowm.gr

1

Corresponding author.

J. Sol. Energy Eng 131(3), 031001 (Jun 10, 2009) (12 pages) doi:10.1115/1.3139137 History: Received April 22, 2008; Revised July 29, 2008; Published June 10, 2009

Understanding building envelope performance and thermal mass effects is becoming increasingly important under the scope of low energy building construction and energy conservation. In the present paper, a three-dimensional computational fluid dynamics methodology is presented for the numerical simulation of the flow and heat transfer that determine the thermal behavior of simplified building envelopes. This is dominated by a conjugate heat transfer approach, which involves conduction, convection, solar heat gains, ambient temperature variation, and the effects of thermal radiation losses to the sky. Validation results include comparison both with measurements from fundamental laboratory studies of heat transfer from surface mounted cubes and with numerical results from well established commercial building energy simulation software. Numerical issues, such as temporal and spatial discretization, are addressed, and parametric studies are performed with regard to the effect of external flow Reynolds number and temperature variation in the building envelope, depending on the individual orientation of the external walls with respect to the flow and on the thermal properties of the building materials. Results from the parametric studies performed indicate that the transient three-dimensional calculations provide important information regarding the effect of external flow properties, such as the approaching flow temperature, velocity, and direction on the thermal behavior of the building envelope. In addition, it has been clearly demonstrated that the methodology is also capable of taking into account the complex effects of parameters such as the building material properties.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) General view of grid in three directions and (b) Cartesian grid and coordinate system near the cubicle (dH=H/29)

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Figure 2

Surface pressure distribution on the upstream (a) and downstream (b) face of a surface mounted cube

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Figure 3

Nondimensional surface heat transfer coefficient on the top (a) and side (b) face of a heated surface mounted cube

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Figure 4

(a) Parametric effects of spatial and temporal discretization on mean temperature variation in enclosure and comparison with TRNSYS calculations. (b) Variation in ambient temperature and normal incidence of total solar radiation (Envelope 1).

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Figure 5

Temperature distribution in and around the building envelope in the morning (a), early (b), and late afternoon (c). Sun position and orientation are also indicated (Envelope 1).

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Figure 6

Variation in combined convective and radiative heat transfer coefficient on the outer surfaces of the enclosure for Re=2×105 (Envelope 1, dw=Wth/12, dt=1 h)

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Figure 7

Effect of ambient conditions (Re, run initiation time to) on the variation in enclosure mean temperature (Envelope 1)

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Figure 8

(a) Variation in inner surface mean temperatures for Re=2×105 and (b) difference in inner surface mean temperature variation ΔT=(TRe=2×105−TRe=1×106) (Envelope 1)

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Figure 9

Variation in enclosure mean temperature for different envelope properties (to=06:00, Re=2×105)

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