The effect of weather on temperature variation inside a solar dryer in Ahvaz‐Iran using computational fluid dynamics method

Abstract

AbstractIn subtropical hot desert climates, the high temperature inside the chamber of the solar dryers spoils heat‐sensitive bioactive ingredients of agricultural products. In this article, the annular temperature variation inside the dryer chamber and collector thermal efficiency of a naturally ventilated indirect solar dryer in Ahvaz‐Iran was evaluated using computational fluid dynamics models. Time variable boundary conditions based on the regional meteorological reports and Universal Time Coordinated for automatic consideration of solar heat radiation, were applied in the models. The results were validated against the physical experiments by accuracy evaluation of the chamber temperature (root mean squared error [RMSE] of 3.14°C), product moisture ratio (RMSE of 0.26), and solar heat flux (RMSE of 84.26 W/m2). The efficiency of the collector was shown to be minimal during the warm months from April to September with a higher level around the solar noon. Daily variation of the temperature inside the chamber from sunrise to sunset and the annual interval of each temperature lasts during a day were presented which can be used for defining the tolerable period of drying. The possibility of drying medicinal plants was presented as a sample. The results can provide a viable estimate for similar climates in the Middle East.Practical ApplicationsIn this study, many details of preprocessing procedure of solar drying computational fluid dynamics (CFD) simulation has been presented which is practical for related studies about the dryers or any process affected by variable weather and solar radiation. Graphical results are comparable and useful for numerical research studies on heat and mass transfer phenomena. The accuracy of the CFD model that was validated against the physical experiments, is promising for CFD‐based drying process optimization research studies. The results of physical experiments which have been expressed in good detail can be used as a reference for future research studies. The tolerable period of drying of agricultural products in Ahvaz‐Iran can be extracted from the results of this study which is a viable estimation for similar climates in the Middle East.