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Research Papers

Development of a Predictive Equation for Ventilation in a Wall-Solar Chimney System

[+] Author and Article Information
David Park

Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: dpark89@vt.edu

Francine Battaglia

Fellow ASME
Department of Mechanical Engineering,
Virginia Tech,
Blacksburg, VA 24061
e-mail: fbattaglia@vt.edu

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received May 17, 2016; final manuscript received December 11, 2016; published online January 16, 2017. Assoc. Editor: Jorge E. Gonzalez.

J. Sol. Energy Eng 139(3), 031001 (Jan 16, 2017) (9 pages) Paper No: SOL-16-1227; doi: 10.1115/1.4035516 History: Received May 17, 2016; Revised December 11, 2016

A solar chimney is a natural ventilation technique that has potential to save energy consumption as well as to maintain the air quality in a building. However, studies of buildings are often challenging due to their large sizes. The objective of this study was to determine the relationships between small- and full-scale solar chimney system models. Computational fluid dynamics (CFD) was employed to model different building sizes with a wall-solar chimney utilizing a validated model. The window, which controls entrainment of ambient air for ventilation, was also studied to determine the effects of window position. A set of nondimensional parameters were identified to describe the important features of the chimney configuration, window configuration, temperature changes, and solar radiation. Regression analysis was employed to develop a mathematical model to predict velocity and air changes per hour, where the model agreed well with CFD results yielding a maximum relative error of 1.2% and with experiments for a maximum error of 3.1%. Additional wall-solar chimney data were tested using the mathematical model based on random conditions (e.g., geometry, solar intensity), and the overall relative error was less than 6%. The study demonstrated that the flow and thermal conditions in larger buildings can be predicted from the small-scale model, and that the newly developed mathematical equation can be used to predict ventilation conditions for a wall-solar chimney.

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References

Figures

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Fig. 1

Geometry of wall-solar chimney and room with absorber and window positioned at middle of the northern wall: (a) 3D view and (b) front view

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Fig. 2

Comparison of domain sizes between (a) small-scale (1 m3) and (b) full-scale (27 m3) rooms

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Fig. 3

Average velocity ratio versus d for window position and absorbed solar intensity

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Fig. 4

Effect of room size d on (a) average room temperature, (b) average absorber temperature, and (c) nondimensional temperature. Symbols represent window position and absorbed solar intensity.

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Fig. 5

Nondimensional temperature versus absorbed solar intensity for window position and room size

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Fig. 6

Velocity (left) and temperature (right) contours at the room centerplane for room volumes of (a) 1 m3 and (b) 27 m3 for both window positions

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Fig. 7

Relationships for π terms for the window positioned at top (filled) and middle (hollow) with solar intensities

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Fig. 8

Comparison between predicted π1 using Eq. (14) and simulated π1 for model B: cases for the window positioned at top (filled, red), middle (hollow, blue), and turbulent cases from Ref. [16] (triangle, green)

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Fig. 9

Comparison between predicted π1 using Eq. (14) and simulated π1 for model B for test cases in Table 3

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