Heat Transfer and Natural Ventilation Airflow Rates from Single-sided Heated Solar Chimney for Buildings

Abstract

Heat transfer process and natural ventilation driven by a solar chimney attached to a sidewall of building are investigated with CFD technique (MITFLOW) in detail. In this paper, conditions and parameters studied in the modelling study are the cavity width of the solar chimney, the wall temperature, the height and breadth of the solar chimney, the ratio of outlet area to inlet area as well as the outlet location of the solar chimney. The ranges of calculation parameters focused on a solar chimney with single-sided solar collector (single-sided heated wall) cover following conditions: solar chimney length L = 0.5m~5.0m, breadth B=0.1m~0.5m, height H=2.0m~5.0m, and B/H=0.05~0.25. Heated wall surface temperature Tw is changed in the range of 30˚C~70˚C; the ratio of the outlet area to inlet area A r is changed in the range of 0.6~1.0. It is found that for given building geometry and inlet areas, there is an optimum cavity width at which a maximum airflow rate can be achieved. Based on the prediction, the airflow rate reaches maximum when B/H is approximately 1/10. It is also found that for given chimney geometry, solar chimney ventilation flow rate can be increased with the enhancement of chimney height only the cross sectional area no more than the critical area, because cross section area has a strong effect on the transitional and/or turbulent convective heat transfer in an enclosure. From the view of economy technology, the optimized height of a solar chimney can be determined according to the optimized section ratio of breadth to height and available breadth in practice. On the analysis of CFD prediction, it is noted that optimized ventilation flow rate can be obtained when the outlet area takes the same area as the inlet area. Generally, there is good agreement among the numerical results, available experimental data from literature and theoretical analysis of natural ventilation from the solar chimney.

Enhancement of stack ventilation in hot and humid climate using a combination of roof solar collector and vertical stack

“…The cavity width of 0.2 m was chosen as most of previous studies suggested on that size as the effective width [27e29]. Meanwhile, the ratio of 1:10 (cavity width:height) is suggested by Bouchair [27] and Li et al [30] for the vertical solar induced ventilation configuration, namely solar chimney and Trombe wall.…”

The Effect of Geometric Parameters on the Performance of Solar Chimney: A Numerical and Experimental Study

“…The effect of the slope on the flow out of the stack was studied by authors in [15], which showed that the absorption is optimal, for an angle of inclination varying between 40° and 60°. The processes of heat transfer and efficiency of natural ventilation driven by a solar chimney have been studied in [16]. Authors in [17] published a review of the main characteristics of chimney solar power plants.…”

An Investigation of Natural Convection of Air Flow through A Vertical Duct with Rectangular Cross-Section Heated from A Singled-Side.

“…Hirunlabh et al( 1999). Li, et al (2004),investigated heat transfer process and natural ventilation driven by a solar chimney attached to a sidewall of building ,with CFD technique in detail. They studied the chimney cavity width, wall temperature, height and breadth, the ratio of outlet area to inlet area as well as the outlet location of the solar chimney.…”