Characterizing the induced flow through the cavity of a wall solar chimney under the effects of the opening heights

Abstract

Using solar chimneys in buildings can enhance the thermal insulation of the building envelope and provide sufficient ventilation and cooling. The performance of a solar chimney is strongly affected by its configurational factors. This work examines the effects of the opening heights on the flow field in the cavity of a wall solar chimney with a Computational Fluid Dynamics (CFD) model. Both cases of equal and unequal opening areas were considered. The results show that the induced flow rate increases with the opening height and gradually becomes constant as the opening height is about 2.0–3.0 and 5.0–6.0 times the air gap for heating the left wall (HLW) and the right wall (HRW) of the air cavity, respectively. Particularly, using equal inlet and outlet heights that are equal to the air gap reduces the flow rate of 27% for HLW and 85% for HRW compared to the maximum ones. The optimal design of a wall solar chimney to achieve maximum flow rate is proposed for two cases of heating, that is, (a) for HLW, equal opening heights which are twice the air gap, and (b) for RHW, the inlet height equal to the air gap, and the outlet height equal to five times the air gap.

Evaluating the Performance of a Combined Vertical Wall–Horizontal Roof Solar Chimney for the Natural Ventilation of Buildings

“…Increasing L t from 1.0 m to 1.5 m (G = 0.075 m) results in an increase in the flow rate by 1.3 times, from 0.0335 to 0.0448 kg/s. In the experiment by Burek and Habeb [27] on a stand-alone vertical solar chimney, the flow rate also increased 3.4 times as the gap increased from 0.02 m to 0.1 m. For a wall-embedded solar chimney, Nguyen and Nguyen [10] reported an increase of 1.35 times as the height increased from 1.0 m to 1.5 m. Increasing the gap and the height results in increases in the effective flow area and the stack height, respectively, hence enhancing the flow rate [5].…”

“…The opening size also significantly influences their performance. In general, the flow rate increases with the opening size until it becomes constant when the opening height is larger than 3.0-6.0 times the air gap of a wall solar chimney [10]. For roof solar chimneys, Al-Kayiem et al [11] claimed that the highest flow rate was achieved with a horizontal inlet flow direction.…”

Comparison of the induced flow obtained with 2D and 3D CFD simulations of a solar chimney at different width-to-gap ratios

“…Among the green technologies for buildings are solar chimneys, which utilize solar thermal energy for ventilation, heating, or cooling. A typical solar chimney configuration consists of an air channel and a surface absorbing solar energy to induce air flow for ventilation (Chen et al, 2003; Nguyen and Nguyen, 2023; Tan and Wong, 2012). Other forms of solar chimney are Trombe wall (Wu et al, 2023) or double-skin facades (Arabi et al, 2023).…”

“…The main chimney dimensions include the height, gap, and width of the cavity whose effects are dominant over the environmental factor (Zhang et al, 2022b). Among the configurational parameters, the opening size and shape are crucial (Bassiouny and Koura, 2008; Nguyen and Nguyen, 2023; Nguyen and Wells, 2020a).…”

“…The 2D models simulate the flow and heat transfer in the central plane of G × H of a solar chimney, therefore, are suitable for investigating the effects of the two-dimensional factors, such as the height, gap, and opening configurations. It is reported that the induced flow rate increases with the height and the gap (Bassiouny and Koura, 2008; Nguyen and Nguyen, 2023; Nguyen and Wells, 2020a; Zavala-Guillén et al, 2018; Zhang and Yang, 2019) and the opening size (Bassiouny and Koura, 2008; Nguyen and Nguyen, 2023; Nguyen and Wells, 2020a). The highest ventilation rate of a room-attached solar chimney is obtained with a parallel arrangement of the air cavities (Nguyen et al, 2022).…”