Design and development of a parabolic trough solar collector for pasteurization of milk†

Milk, regardless of its end use, is required by law to be pasteurized to kill spoilage microorganisms and deactivate enzymes. Conventional methods of pasteurization use fossil fuels, which have a harmful effect on the environment. This study presents the design, optimization, fabrication, and experimental evaluation of a solar-powered milk pasteurization system using a parabolic trough collector (PTC) integrated with a single-axis solar tracking mechanism. The design parameters of the PTC including length (3 m), width (1 m), and rim angle (90°) were optimized using a combination of SolidWorks flow simulations and SolTrace, respectively. A single-axis solar tracking device was also developed to increase the efficiency of PTC, and this allowed the PTC to align with the direction of the Sun. The developed PTC was tested to determine whether it could achieve the temperature normally used for milk pasteurization. Milk and water temperature increased from an initial value of 33.03 ± 2.73 °C to 76.03 ± 1.35 °C, and 29.67 ± 2.86 °C to 80.85 ± 2.06 °C in 1 hour, respectively. Temperature increases of 12.43 ± 1.59 °C and 17.90 ± 2.42 °C were found for milk and water at a flow rate of 30 L h⁻¹ in a single pass, respectively. This temperature increase suggests that the developed system has the potential to be used for the pasteurization of milk and similar liquid products utilizing solar energy.