Research Article

Effects of roof angle, inlet gap size and dryer height on temperature and relative humidity in a chimney-dependent solar crop dryer

¹ Department of Mechanical Engineering, College of Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
² Department of Mechanical Engineering, Kumasi Technical University, Kumasi, Ghana

^* e-mail: tonyagyemang@yahoo.com

Received: 3 February 2022
Received in final form: 9 April 2022
Accepted: 9 April 2022

Abstract

A chimney dependent solar crop dryer (CDSCD) was developed and studied. Design of Experiment (DOE) was employed using statistical three level non randomized factorial experimental design in Minitab statistical software version 19.0. The study of effects of roof angle, inlet gap size and dryer height on dryer temperature revealed that the height at which the drying tray is positioned (A) and the inlet gap (C) influences the highest temperature difference, 30.4 °C. It was concluded that dryer temperature is high when the inlet gap is small (range of inlet area to exit area ratio of 1.8128:1 to 1.0877:1) and the maximum ratio of height of dryer to drying tray’s position is 2.18. Optimal values for achieving high temperature difference response greater than or equal to 32.6 °C are minimum roof height of 84 cm, inlet to outlet area ratio of 1.0877:1 and minimum roof angle of 81°. The effect of the three parameters on relative humidity revealed that the combined effect of roof angle and inlet gap (AB) attained the highest standardized effect of 6.6. The optimal values for achieving low dryer relative humidity (when loaded with 1 kg of cassava) were roof angle of 64°, inlet to outlet area ratio of 2.5379:1 and minimum time of 19 hours. This could serve as effective tool for comparing different designs of CDSCD dryers for optimum humidity and drying performances and be used to subsequently refine solar crop dryer design.