Experimental Research of Drying Characteristics of Red Banana in a Single Slope Solar Dryer Based on Natural and Forced Convection
Department of Mechanical Engineering, National Institute of Technology Puducherry, 609609 Karaikal, U.T of Puducherry, India
Received: 4 July 2020
Accepted: 16 March 2021
single slope solar dryer, red banana drying, drying kinetics, moisture ratio correlation, moisture diffusivity, activation energy
Research background. Traditionally, open sun drying method is used to dry the products for long time preservation. For the same products, solar drying technology is being employed to minimize the drying time for achieving the required moisture content. This solar drying technology, which inherently contains complex heat and mass transfer mechanism, which makes difficult to describe drying kinetics at the micro level.
Experimental approach. In this present paper, research work is carried out to investigate the drying of 5 mm thickness of red banana (Musa acuminata “Red Dacca”) in a single slope solar dryer based on natural and forced convection. Based on the experiments, development of new semi-empirical thin layer drying kinetics correlation for red banana is proposed. The proposed correlation is also compared with other existing models. The proposed model is in very good agreement with well-known other models and the correlation coefficient (R2) of 0.997 is obtained. Based on the model, the moisture diffusivity and activation energy of the red banana are also obtained.
Results and conclusions. It is found that, the moisture diffusivity of the red banana samples is in the range of 8.74·10-10-1.56·10-9 m2/s for natural convection solar drying and 8.43·10-9
-2.61·10-8 m2/s for forced convection solar drying. The activation energy of the red banana is varied from 24.58 to 45.20 kJ/mol for passive mode and 22.56 to 35.49 kJ/mol for active mode. Besides, energy and exergy analysis of red banana in a dryer are also carried out. It is found that the average exergy losses for the forced and natural convections are obtained as 16.1 kJ/kg and 6.63 kJ/kg and the average exergic efficiency for the natural and forced convection dryer was obtained as 57.7 and 70.9 %, respectively.
Novelty and scientific contribution. A single slope direct type solar dryer was designed and fabricated to maintain the desired temperature for a specified period in both natural and forced convection phenomena. A novel drying kinetics model is proposed to preserve red banana. The proposed model given a superior correlation coefficient (R2) when compared to other drying kinetics models.