Experimental testing of mixed-mode double pass solar air heater integrated with aluminium cans for red pepper drying

Abstract

A solar air heater that operates in the mixed-mode double pass and an absorber plate has aluminum cans at the top and bottom of the absorber for red pepper drying experiments was conducted in Bahir Dar, Ethiopia climatic conditions. A total dying period of red pepper in a mixed-mode solar greenhouse dryer takes less time than an open solar drying system. From the experiment, the average daily dryer chamber temperature ranges between 39.93 0C and 47.02 0C and the average daily ambient temperature ranges between 24.890C and 27.530C. Solar insolation reached 973 W/m2 when the sun was at mid-day and minimum solar insolation was 220 W/m2 and 0.0383 kg per second of air are expelled. A newly designed mixed-mode double pass, integrated with an Aluminum can dryer and the traditional open sun dryer, achieves an efficiency of 46% and 28%, respectively. In the open sun dryer system and the mixed-mode solar dryer, the drying rates are 0.0003395 kg/s and 0.0000365 kg/s respectively. On eleven mathematical models, Microsoft Excel was used to perform the statistical analysis. Logarithmic models were found to be the best explanation of red pepper behavior in both mixed-mode and open-sun solar dryer systems. These models were tested by comparing the maximum value of the coefficient of determination R2 and the minimum value of reduced chi-square X2 and root mean square error RMSE between experimental and predicted moisture ratios.