Design and experimental studies of an indirect-mode natural convection solar dryer for henna leaves (Lawsonia inermis)

摘要

Solar drying system is an important solution for the preservation of agricultural crops. In this research work, an indirect type natural convection solar dryer is designed, fabricated and tested under the Sahara weather conditions of Algeria. Experimental tests are performed in different seasons in order to study the thermal behaviour of the solar dryer. The temperature distributions in different parts of the dryer, ambient temperature, solar irradiance and relative humidity in the dryer have been recorded. The results show that the use of a vertical absorber will bring more quantity of energy in winter; consequently causes an increase of the dried air temperature. The drying time during the winter period is reduced approximately by 50% compared with the open sun drying; most of the quality henna leaves is perfectly preserved.