Exergy and Energy Analyses for Solar Drying of Peppermint (Mentha piperita) With a Double-pass Collector

Document Type : Research Article


1 Young Researchers and Elite Club, Roudhen Branch, Islamic Azad University, Roudhen, Iran

2 Associate professor of Food Technology in University of Tehran, Karaj, Iran


Three methods of solar drying (I), sun drying (II) and shade drying (III) used to reduce the moisture content of peppermint from 87 to 7% (wet basis). The increase of air-drying temperature (∆T) for peppermint dehydration in method II reached up to 4oC after absorbing of daily solar energy (Iave=957 W/m2). However, in the method I, this parameter (∆T) reached to 18oC after the ambient air passed through a double-pass heat collector (with only 1.26 m2 area). Although the enthalpy of drying air in the method I reached to 35 kJ/kg (40% more than the other methods because of the high heat intensity of solar collector Iave=840 W/m2), only ~16% of accumulated solar heat used to increase the peppermint temperature and evaporate its extra moisture. This is the reason that exergy in the inlet and outlet of the method I during drying peppermint reached to 24 and 38%, respectively. Furthermore, the drying capacity of peppermint in the method I was 100% more than the ones dried in methods II and III at the similar conditions. The total heat loss (because of connecting pipes and drying chamber) in the method I during peppermint drying was < 4% of the total heat collected in solar drier, which is negligible.

Graphical Abstract

Exergy and Energy Analyses for Solar Drying of Peppermint (Mentha piperita) With a Double-pass Collector


  • Designing and fabricate a solar drier equipped with a double-pass collector.
  • Evaluating the thermodynamic conditions and processing time of this solar system and comparing with sun and shade driers for dehydration of fresh peppermint.
  • Analyzing exergy and energy of the designed solar dryer.


Main Subjects

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