Energy Use and Efficiency of Rice-Drying Systems II. Commercial, Cross-Flow Dryer Measurements

Abstract

<abstract> <bold><sc>Abstract. </sc></bold>Energy use and efficiency of a commercial, cross-flow dryer were measured when drying rough rice across a range of ambient conditions and drying air temperatures. Four tests were conducted during the 2011 harvest season using rice with initial moisture contents ranging from 19.0% to 21.7% wet basis and three tests were conducted during the 2012 harvest using rice with initial moisture contents from 15.4% to 18.3%. To obtain thermal energy requirements in terms of energy per unit mass water removed, the energy consumed by the burner was divided by the total amount of water removed. In addition, electrical energy requirements were determined by multiplying the average power draw of the fan motor by the fan operating duration. Thermal energy efficiency was calculated by dividing theoretical energy requirements by the measured thermal energy requirements. Thermal energy requirements to dry rice ranged from 6,900 to 9,670 kJ/kg water removed in 2011 and from 8,810 to 9,620 in 2012. Electrical energy use, which ranged from 300 to 400 kJ/kg water removed in 2011 and from 410 to 630 in 2012, accounted for ~4% to 5% of the total energy used to dry rice. Thermal energy requirements were linearly correlated to the difference between drying air temperature and ambient temperature and linearly and inversely correlated to the amount of water removed per mass dry matter. Thermal energy efficiency ranged from 26% to 36% in 2011 and from 27% to 29% in 2012.