Heat-transfer modeling as a design tool for improving solar water disinfection (SODIS) containers

A simplified heat-transfer model has been developed to effectively simulate thermal performance of water containers used in solar water disinfection (SODIS) applications. The purpose of the model is to facilitate accurate, fast, and uncomplicated prediction of thermal performance of different SODIS-container designs and configurations, enabling developers to analyze new design ideas without the needs for field experiments, which are typically cumbersome and difficult to compare. The model utilizes electromagnetic absorption coefficients and other thermal properties of container materials, and water to establish control-volume heat-transfer equations that can predict the water temperature. The model’s simulated results of basic container designs agreed reasonably well with experimental results. Preliminary enhancements to the water container design were implemented—namely painting the container’s underside black and covering the container with a clear plastic bag—with the aim to achieve higher disinfection efficacy through higher water temperatures, in accordance with the fundamentals of SODIS mechanisms. The heat-transfer model predicted that both design enhancements would significantly increase the water temperature, with the black coating being more effective. Subsequent field experiments confirmed the model’s predictions.