Abstract
As most existing office buildings in China lack fresh air systems for ventilation, natural ventilation with windows remains the main means of improving indoor air quality and adjusting indoor thermal comfort. However, knowledge of the ventilation characteristics of various window-opening forms in actual buildings is limited and current methods for evaluating ventilation performance lack a comprehensive consideration of ventilation rate and thermal comfort. In this study, the ventilation characteristics of different window-opening forms were systematically compared by conducting computational fluid dynamics (CFD) simulations. A full-scale experiment was conducted in a typical office room in a university in Tianjin to validate the CFD simulation. Two ventilation modes (wind-driven cross-ventilation and temperature-driven single-sided ventilation), three window-opening angles, and seven window types were investigated. Additionally, the ratio of the ventilation rate to the absolute value of thermal sensation was used to quantify the indoor natural-ventilation performance. The results showed that a sliding window with a full opening has the highest discharge coefficients of 0.68 and 0.52 under wind-driven cross-ventilation and temperature-driven single-sided ventilation, respectively, and top-hung windows opening both inwards and outwards have better ventilation performance than other window types under the two ventilation modes. This study is applicable to the design and practice of natural ventilation.
Highlights
Natural ventilation can help adjust indoor thermal comfort [1,2,3], improve indoor air quality [4,5], and reduce the energy consumption of mechanical ventilation systems [6,7,8]
According to the left and right symmetry, the seven window types were divided into two types: symmetrical windows, namely top-hung window opening inwards (THWI), THWO, bottom-hung window opening inwards (BHWI), bottom-hung window ope8noinf g20 outwards (BHWO), and sliding window (SW), and asymmetric windows, namely casement window opening inwards (CWI) and casement window opening outwards (CWO)
(1) For CV, on the windward side, the maximum value of the wind pressure coefficient of different window types does not appear at 0◦ (360◦), but under the symmetrical condition of 22.5◦ (337.5◦); there is a similar situation on the leeward side, where the minimum value of the coefficient appears in the symmetrical conditions of 157.5◦ (202.5◦)
Summary
Natural ventilation can help adjust indoor thermal comfort [1,2,3], improve indoor air quality [4,5], and reduce the energy consumption of mechanical ventilation systems [6,7,8]. In the design and practice of window ventilation, the window configuration, window-opening form, and opening angle are three important influencing factors [16]. The occupants usually control the window-opening angle to adjust the ventilation rate [19]. The influence of these three factors on the discharge coefficient and ventilation performance has been studied by the research community. Many studies have been conducted on the design, practice, and assessment of window ventilation, the ventilation characteristics of various window-opening forms and opening angles in actual buildings are rarely systematically and quantitatively compared. To address this research gap, in this study, natural ventilation characteristics and performance were quantified and assessed under different window-opening forms and ventilation modes. The window ventilation performance was comprehensively evaluated by combining the ventilation rate and thermal comfort
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