Solar chimney under three heating modes

Solar chimneys under heating modes are much more complicated than those under cooling modes, as their performance should consider both airflow rate and temperature rise. Their heating performance and optimization designs are still unclear under various heating modes. This study then addressed the impacts of typical design factors on their heating performance numerically and empirically under three heating modes, including two fresh-air heating modes (i.e., through inlet and window) and a sealed heating mode. Similar to the cooling mode, the impacts of the analyzed design factors on the temperature rise and airflow rate can be expressed by the exponential function. Differently, the cavity gap under the three heating modes shows negative exponentials (−0.18 to −0.088), while the cooling model is between 0.652 and 0.756. Solar radiation shows positive exponential under both heating and cooling modes, and its impacts on airflow rate are relatively higher under cooling mode. Also, the temperature rises within both the chimney cavity and the attached room along the height show natural exponential functions. A lower window (or even closing it and replacing it with a bottom vent near the floor for fresh air supply) is suggested for the two heating modes with fresh air supply to avoid vertical temperature differences inside the room. Compared to the fresh air through inlet, sealed heating offers a 292.8% higher air temperature rise and 3.9% lower airflow rate, whereas fresh air through window offers a 19.3% higher airflow rate and 44.5% higher air temperature rise. Therefore the modes of fresh air through inlet and window can be applied to those locations under cool and cold climates, respectively; sealed heating is only applicable to those scenarios without or with limited occupants (i.e., storage) as no fresh air is supplied.