Solar Collector Exergetic Optimization for a Multi Effect Humidification Desalination Prototype

Venezuela is a country with a great deal of water sources, as a consequence of its location in the Amazon Basin. In spite of this, about 1.6 million inhabitants are dispersed in remote regions throughout the nation, where water distribution is problematic due to the lack of this resource. Since 2007, The Institute of Energy of the Simon Bolivar University has been focused on the development of a 25 liters per day single stage solar Multi-effect Humidification (MEH) desalination plant using a flat plate solar collector. Once the construction of the prototype plant was completed, the characterization of its different components was performed. The one related to the solar collector unit was done on a testing rig designed and constructed according to the ANSI/ASHRAE 93-2003 standard requirements. In order to optimize the operation of this equipment is necessary to maximize the exergetic change of the working fluid across the solar collector, to achieve this objective a numerical simulation using a predictive algorithm and an available yearlong meteorological data was performed. The prediction algorithm was validated against experimental data obtained from the characterization tests. The numerical results obtained were in good agreement with previous related researches. It was found that the best way to operate the solar collector in remote areas and ensure the maximum exergetic gain of the working fluid was to maintain a fix mass flow rate of 0.006 kg/s (0.36 LPM). This corresponds with the climate conditions at Simon Bolivar University and an admission temperature of 54°C, which is the design value of the desalination plant.