Experimental analysis of hybrid dryer combined with spiral solar air heater and auxiliary heating system: Energy, exergy and economic analysis

Abstract

The simultaneous energy and food resources management can be a challenging problem for researchers working in this field. Solar dryers are equipment that can employ solar energy in order to dry degradable food for long-term storage. However, these systems should also utilize an auxiliary energy source because of non-availability of continuous access to the solar radiation. In this paper, a cabin solar dryer equipped with a heating element as an auxiliary heat source has been used to dry four types of products. The tested products consist of apple, kiwi, banana slices, as well as quince julienne strips. The experiments were performed in four days during autumn, when the solar energy had a low level intensity and the heating element was employed for aiding the energy supply. Temperature and humidity have been measured using temperature and humidity sensors mounted at the inlet and outlet of the collector and dryer cabin. Then the thermal efficiency of the collector and the cabin is investigated via the energy and exergy analysis, and the thermal performance of the system is analyzed. Lastly, an economic analysis is presented to calculate the production cost of per kilogram of products. The results show that thermal efficiency, drying process exergy, produced exergy and specific moisture evaporation rate (SMER) of julienne strips of quince are higher than those of other products. Although banana slices have better conditions in terms of these parameters among the sliced products. Due to the results, it was found that the quince julienne strips have the highest cost about 1.137 $/kg and the lowest drying rate about 0.188 kg/h. On the contrary, the minimum cost belongs to the apple slices about 0.478 $/kg and the maximum drying rate about 0.3224 kg/h.