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This paper links the geometric design of most classical configurations of solar air heaters (SAHs), their thermal performances, and their appropriate application. The optimization concerns mainly the absorber shape and the airflow direction. Therefore, single pass and counter flow double pass SAHs with flat plate, finned, and V-corrugated absorbers and SAH with an external recycle were investigated. The overall aim is to single out the most suitable configurations for the drying process and habitation heating. Modeling of the SAHs was based on solving the energy balance equations of the SAH's components. The numerical results showed that the thermal efficiency was significantly improved by the counter flow double pass mode by about 17.01% for SAHs with a flat plate absorber and 9.03% for SAHs with a V-corrugated absorber. Furthermore, the V-corrugated shape of the absorber increases the thermal and exergy efficiencies compared to the flat plate shape, e.g., by 8.66% and 1.27% at ṁ = 0.025 kg s−1, respectively. In addition, the present study highlighted that the outlet air temperature and the thermal and exergy efficiencies could be enhanced by increasing the number of fins, and the optimal number of fins was found to be 24 per meter width of the SAH. Experimental studies were carried on a modular SAH. They showed the good capability of the developed model in predicting the thermal performances of the studied solar collectors. Finally, the SAHs were assigned to three appropriate uses, namely, aromatic and medicinal plant drying, agri-food product drying, and habitat heating.

A Takagi Sugeno fuzzy (TSF) modeling of an indirect hybrid solar-electrical dryer operated in forced convection (0.027 kg/s) was developed. The hybrid dryer was considered as a nonlinear and uncertain system where the operating point varies with weather conditions and airflow. The proposed TSF model was used to predict the drying temperature in no load conditions. Different experimental measurements were set up and used for evaluating the reliability of this model. At first and before applying this method to hybrid solar-electrical dryer, the TSF modeling was tested on solar mode and electrical mode where only one energy source was considered in each mode. The proposed model was experimentally validated in two main modes of the dryer operation: solar mode and electrical mode. The predicted behavior was closed to the experimental data with Root Mean Square Error (RMSE) of 2.34 and 2.21 in solar mode and electrical mode, respectively. The obtained predicted behavior confirms the pertinence of the identified model. The TSF model of the dryer leads to predict the drying temperature instantly with a huge reduction in simulation time in comparison with other modeling techniques. Thus, it is useful for synthesizing a control system of the drying parameters.

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