This research aims to determine the primary thermofluidic correlations describing the thermosiphon effect under idealized steady-state conditions, considering water-in-glass evacuated-tube geometry, tilt angle, and heat flux. A numerical model based on Computational Fluid Dynamics (CFD) was developed to obtain these correlations for water-in-glass evacuated-tube solar collectors. Initial validation against experimental velocity and temperature profiles was necessary. With a validated CFD model, thermofluidic correlations were determined, expressed as dimensionless parameters such as Re, Gr, and Pr, water-in-glass evacuated-tube dimensions, and tilt angle. Symmetry was exploited in the water-in-glass evacuated-tube geometry for both validation simulations and the development of thermofluidic correlations. Contrary to correlations recorded in the literature, the correlations obtained in this study indicate an increase in water flow and a decrease in mean temperature with increasing tilt angle. These correlations are crucial for the energy–exergy balance formulations used in the analysis and design of such thermal systems.

This study presents a detailed experimental and analytical investigation of a solar greenhouse dryer, specifically designed and evaluated for its energy, economic and environmental performance in coffee processing. The dryer has a semi-cylindrical structure, a transparent polycarbonate cover, a galvanised steel frame and a concrete floor. Forced convection is facilitated by humidity extractors powered by photovoltaic panels, which improve air circulation and moisture removal. The performance of the system was evaluated by drying parchment coffee beans from an initial moisture content of 53.5% (wet basis) to a final moisture content of 11.1% (wet basis) over a period of four days. During this period, the air temperature inside the dryer reached a maximum of 52° C. The dryer achieved a maximum thermal efficiency of 33% during periods of maximum solar radiation. An exergetic efficiency value of $\mathbf{4 0 \%}$, in addition comprehensive economic analysis projects a payback period of 5.48 years based on an operational lifetime of $\mathbf{1 0}$ years. The energy production factor was determined to be 1.197; meaning that the system generates more energy than is required for operation, which supports its viability for sustainable coffee processing. In addition, an environmental impact assessment was carried out, evaluating the embodied energy of the construction materials and the potential reduction of CO2 emissions compared to conventional drying methods. The results demonstrate that the solar dryer was realised using a combination of Microsoft Excel and MATLAB programs to validate the performance of the dryer.