Heat transfer in two and three-dimensional single span greenhouses

Abstract: The purpose of this paper is to investigate the heat transfer in two-dimensional and three-dimensional cavities representing a single span greenhouse. This investigation is conducted numerically using Computational Fluid Dynamics (CFD). The heat transfer and temperature fields driven by buoyancy forces are investigated. The research commences with the validation of a few fundamental geometries used as the building blocks for a large commercial greenhouse. The first fundamental geometry is a square filled with air. The CFD results for a square cavity are first evaluated against experimental results found in the literature for both two and three dimensional cavities. The heat transfer inside the cavities is then investigated and compared to those found in the literature. A reasonably good comparison between the numerical CFD results and the experimental results was found for both the two- and three-dimensional cavities. Based on the validated CFD models, two three-dimensional single span greenhouses containing a pitched roof were investigated to determine the effect of design alterations on the heat transfer within the cavity. The results were also compared to two-dimensional greenhouses with a 30 and 45 degree roof angle respectively. Results found that there are significant differences between the two and three-dimensional cases when the average Nusselt number is considered, especially for a greenhouse containing a roof angle of 45 degrees. Temperature distributions were also found to vary significantly throughout the three-dimensional greenhouses