• Food Engineering Progress
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• v.13 no.4
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• pp.308-313
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• 2009

This study was conducted to design and fabricate a heat pump that can produce some weather conditions similar to those of the dry season of the rough rice in Korea, and to investigate basic performances of the apparatus. During the drying test, the amount of energy consumption and drying characteristics were measured at four different temperature levels ranging between 20$^{\circ}C$ and 50${^{\circ}C}$. In the psychrometric chart, the freezing capacity and refrigerant circulation ratio of the heat pump were 173 kJ/kg and 49.6 kg/hr, respectively. Therefore, coefficient of performance was 5.5, which was superior to that of refrigerant R-22 (4.0) in standard refrigeration cycle. In addition, the time to reach target drying temperature (30${^{\circ}C}$) and relative humidity (40%) were 6 minutes and 7 minutes, respectively. Temperature differences between the drying temperature and the rice were 1.5${^{\circ}C}$ and 8.5${^{\circ}C}$ at the drying temperatures of 21.9${^{\circ}C}$ and 48.7${^{\circ}C}$, respectively. This result demonstrated that the increased temperature of the rice in the drying section decreased sufficiently in the tempering section. At the drying temperatures of 21.9, 30.7 38.8, and 48.7${^{\circ}C}$, drying rates were 0.29, 0.61, 0.85, and 1.26%/hr, respectively, which were similar to those of commercial dryer. In addition, the amounts of energy consumption were 325, 667, 692, and 776 kJ/kg, respectively. These results showed that this dryer saved up to 86% of energy consumption compared with the commercial dryer, which uses 4,000-5,000 kJ/kg of fossil fuel.