Studying Control Parameters Effects on Performance of Drying Cocoa Bean with Heat Pump Dryer
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Abstract
The objective of this research was to study the effects of controlled parameters on the performance of drying cocoa beans with a heat pump dryer. The drying rate, the coefficient of heat pump performance, the specific moisture extraction rate, and color quality were analyzed to indicate the drying performance of cocoa beans. The controlled parameters included temperatures of 40, 50, and 60 ºC and velocities of 1.5, 3.5, and 5.5 m/s using a small heat pump dryer. A closed air system with 60% of the air passing across the evaporator was used in all tests. One kilogram of fermented cocoa beans was used as the raw material. It had an initial moisture content of 142.42±0.52 % (dry basis) and it was dried until the final moisture content of 6.09±0.56 % (dry basis). The results showed that at the same temperature, the drying rate and the coefficient of heat pump performance increased as the velocity increased, but the specific moisture extraction rate decreased. In the case of constant velocity and then increasing the temperature, the drying rate and the coefficient of heat pump performance increased but the specific moisture extraction rate decreased. For the color quality, when the temperature and velocity increased, it was found that the brightness value (L) and yellowness value (b*) decreased, but the redness value (a*) increased. Finally, the condition of 40 °C and 1.5 m/s should be used because it gave the highest specific moisture extraction rate and the quality of dried cocoa beans met the needs of professional groups.
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