Heat transfer simulation for re-design of tray dryer to reduce the energy consumption in the cocoa bean drying process

Abstract

The tray dryer for the cocoa bean drying process is a solution to overcome conventional drying methods that rely on solar heat. The tray dryer is expected to facilitate the cocoa farmers to dry cocoa beans because it is faster and does not depend on weather conditions. However, even though the current condition of the tray dryer can reduce the energy consumption of drying cocoa beans (from Gunung Kidul, Yogyakarta, Indonesia) compared to the solar heat method, it remains unknown whether the cocoa beans drying quality is good enough. Therefore, this research analyzed the heat transfer phenomena of the cocoa drying process using the computational simulation method to re-design the current tray dryer design so that the new design can fit the drying characteristic of the cocoa bean and reduce energy consumption. As a result, for the air velocity of 25.91 m/s and the ½ opening of the gas valve in 10 minutes, which is already at steady-state conditions, the temperature distribution in the existing tray dryer is not suitable with the characteristics of the cocoa beans drying process. The temperature can be increased by reducing the airflow velocity or increasing the heating value by opening the valve. However, with a new design, the temperature can be increased by up to 37.00% at a velocity of 25.91 m/s with a ½ gas valve opening. Furthermore, the new design can achieve the same conditions as the existing design by only using an opening for a 1/8 gas valve. Thus, using the new design, the tray dryer can achieve the drying characteristics of cocoa beans and reduce energy consumption.