Evaluation of vertical solar-air collectors for natural ventilation using integral and CFD models

Vertical solar-air collectors that are used for providing natural ventilation can be a viable solution in buildings where higher ventilation rate requirements for better indoor air quality cannot be met by traditional natural ventilation methods. Indoor air quality problems have been experienced in Portuguese school buildings where a study revealed that the CO2 concentrations in classrooms in winter were higher than the recommended health limits. To improve the environment in these classrooms, solar-induced ventilation has been suggested. In the design of these solar ventilators, simple models can only predict the main features of the flow but they can be useful tools in the first stages of the design process. However, CFD models can produce microscopic information about the state of all flow parameters and thus are recommended when a high degree of accuracy is needed. In this paper, a simplified model based on the integral equations of motion and heat transfer is developed for a vertical solar-air collector and applied to different boundary conditions. The results are compared and discussed with those computed from a CFD code specially designed for room ventilation.