Application of Passive Technique to Cocoa Beans Batch Dryer and Assessment of Thin Layer Models

Abstract

The objective of this work was to develop a hot air production system using twisted tapes (TT) for the specific purpose of drying cocoa. The study also aimed to analyze the drying characteristics and kinetics of cocoa beans under the specific conditions that were investigated. TTs were inserted into the pipes of the shell and tube heat exchanger with multiple tube passes (STHEX). A modified rocket stove was used to burn biomass. Insertion levels of typical TT are 0%, 17.24%, 34.48%, and 60.63%, representing A (plain tube), B, C, and D, respectively.TT with a higher insertion level results in increased heat transfer. However, this also leads to an increase in pressure loss, which in turn affects the fan power consumption required to maintain the desired flow rate. The insertion level of D was the best in this work. It was used to produce a hot air supply to the drying room. After fermentation, the initial moisture content (MC) of 5 kilograms of the cocoa beans was 56.48% (wet basis; wb). The cocoa beans were dried in a drying room at an airflow rate of 4.5 m³/min. The MC declined from 56.48% to 5.13% (wb) within 14 hours. The present study only detected a falling rate period in cocoa bean drying. The Overhult model is the most effective model for this drying process. It has the potential to serve as a useful tool for engineering applications.