Investigation of the Comparative okra drying performance of a geothermal and solar hybrid forced convection indirect type cabinet dryer

Abstract

This study investigated the okra drying performance of a dryer in which solar and geothermal energy are used together to ensure an uninterrupted operation in the drying processes. For this reason, the performance of the geothermal and solar hybrid forced convection indirect type cabinet dryer was compared with the solar forced convection indirect type cabinet dryer and traditional shade drying methods. In three different experiments, okras were dried from the initial moisture value of 7.735, 8.245, and 8.82 g water/g dry material (d.b.) to the final moisture value of 0.3 g water/g dry material (d.b.). These experiments were carried out in entirely cloudy, partly cloudy, and completely clear weather conditions. Geothermal energy contributed 58.4 % in completely cloudy weather and 49.5 % in completely clear weather. The first tray level of the hybrid dryer reached the final moisture value in 27 h at the earliest. Temperature and humidity changes in all main components of the dryers were analyzed. In addition, the energy analyses of the dryers are discussed. Afterward, aflatoxin and color analyses of dried okra were made.