| Abstrakt: |
ASHRAE Standard 90.1 provides a useful guideline for the Window-to-Wall Ratio (WWR), stating that "the total vertical fenestration area shall be less than 40% of the gross wall area" However, different window configurations with the same WWR can perform thermally differently. In this paper, the effect of window configurations on the convective heat transfer rate of a window and downdraft velocity is investigated numerically at different Rayleigh numbers ranging from 1.7 × 106 to 1.7 × 1011. Parameters investigated in this study include window shape, heater location, and heater temperature. A convective heat transfer rate of each of the window models is evaluated using high-resolution 3-D steady Reynolds Averaged Navier-Stokes (RANS) based computational fluid dynamics (CFD) simulations. The heater and the window are modeled as isothermal plane boundaries, where the window possesses a cold temperature, and the natural convective heater is hotter than room temperature. The sensitivity of the window Nusselt number and downdraft velocity of the windows have been examined. The thermal performance ranking, from higher to lower, is horizontal rectangular, square, circular, and vertical rectangular window configuration, respectively. This implies that proper window geometry configuration selection can be used as one of the passive strategies for saving energy in buildings. • The effectiveness of SST k-w turbulence model to predict temperature distribution is validated. • Window configuration affects thermal comfort and energy consumption of a room. • Variations in convective heat transfer rate are independent of window configuration at lower Rayleigh number values. • Variations in convective heat transfer rate are dependent on window configuration at higher Rayleigh number values. • Performance ranking from high to low is horizontal rectangular, square, circular and vertical rectangular window. [ABSTRACT FROM AUTHOR] |
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