Performance and economic analyses on solar-assisted heat pump fluidised bed dryer integrated with biomass furnace for rice drying

This study is concerned with the performance and economic analyses on solar-assisted heat pump fluidised bed dryer integrated with biomass furnace for rice drying. The dryer decreased the moisture content of rice from 32.85% (dry basis) to 16.29% (dry basis) in 22.95 min, with a mass flow rate of 0.1037 kg/s at an average temperature of 80.9 °C and average relative humidity of 8.14%. The specific moisture extraction rate varied from 0.13 kg/kWh to 0.40 kg/kWh, with an average value of 0.24 kg/kWh. The specific energy, specific thermal energy and specific electrical energy consumptions varied in the range of 2.50-2.62, 0.98-3.03 and 0.90-2.78 kWh/kg, with average values of 4.76, 1.86 and 1.71 kWh/kg, respectively. The thermal dryer, pickup and exergy efficiencies varied in the range of 8.4%-25.6%, 23.7%-73.4% and 13.6%-61.8%, with average values of 15.4%, 43.8% and 41.3%, respectively. Improvement potential varied from 223.3 W to 1391.2 W, with an average value of 630.6 W. The payback period of the dryer was approximately 1.6 years. Furthermore, the experimental dimensionless moisture content data fitted well with the Page's model.