Performance Enhancement of Natural Convection Indirect Solar Dryer by Integrating Reflectors

Abstract

Natural convection indirect type solar dryer integrated with reflectors that can be used for drying fruits and vegetables was designed, constructed, and evaluated. The study mainly tried to improve the performance of a prototype natural convection indirect solar dryer. The solar dryer was integrated with reflectors and its thermal performance was experimentally analyzed and results were compared with the same dryer without reflectors. The experiments conducted included a no-load test to determine the stagnation temperature that can be reached and drying tests using tomato slices. During the drying test, moisture content at the initial and final stages was measured using a moisture balance instrument. The mass of the tomato slices was measured every two hours to find the drying efficiency. Temperatures were measured using thermocouples located at the absorber plate and at the trays inside the drying cabinet. Solar radiation was also measured using a pyranometer located near the dryer. During no load experiments, the maximum temperature reached the collector was around 98oC for the dryer without reflectors. The maximum temperature was improved to around 154oC during the test with reflectors. Similar temperature improvement was obtained during the drying tests as well. Due to the improvement in the temperature in the collector, the drying rate was also improved by 8% for 10 kg and 14% for 5 kg load. The experimental results indicate that the dryer performance was improved when the reflectors were added.