Optimization of air inlet features of an active indirect mode solar dryer: A response surface approach

Abstract

The effect of air flowing into an in an active indirect mode solar dryer was studied. The study aimed at optimizing the airflow features of a solar dryer of active indirect feature using Response Surface Methodology (RSM). The factors of the experiment included the product slice thickness of the experimental product and the air vent of the dryer. The two factors were considered at five levels and a total of 13 experimental runs derived. The air vent was based on the following shape orientations: square, rectangular, circular, and triangular. The thickness of the product was considered at five levels of 4, 8, 12, 16 and 20 mm. The responses from the experimental set up were the air flow rate and drag force, which were determined using established equations. The optimum values for the air flow rate and drag force were 0.0275 m3/s and 0.0476N, respectively. The corresponding optimal conditions which gave the optimum responses were 100 cm2 - square inlet and product slice thickness of 20 mm for air flow rate and 80 cm2 -rectangular inlet and product slice thickness of 20 mm for drag force, respectively. The models for predicting the responses were adequate, with r-square values 0.9463 and 0.9376 and desirabilities of 99.2 and 95.0% for air flow rate and drag force respectively. The experiment was repeated using the optimal conditions to validate the optimum responses. The variation between the predicted and experimental data was less than 8%.