Performance analysis of solar-biomass hybrid heat pump batch-type horizontal fluidized bed dryer using multi-stage heat exchanger for paddy drying

The paddy drying performance of a solar-biomass hybrid heat pump batch-type horizontal fluidized bed dryer (FBD) using a multi-stage heat exchanger was investigated. Drying experiments were performed under two different operating modes: the drying system with heat recovery (FBD-WHR mode) and the drying system without heat recovery (FBD-NHR mode). The FBD-NHR and FBD-WHR reduced the paddy moisture content from 28.52% dry basis (db) to 16.28% db with a mass flow rate of 0.10328 kg/s in 26.76 and 23.68 min, at average temperatures of 69.8 and 70.3 degrees C, respectively. The average specific energy consumption, specific thermal energy consumption, and specific electrical energy consumption were 8.85, 5.81, and 3.04 kWh/kg, respectively, for FBD-NHR and 7.43, 4.22, and 3.21 kWh/kg, respectively, for FBD-WHR. The average specific moisture extraction rates were 0.19 and 0.24 kg/kWh for FBD-NHR and FBD-WHR, respectively. The average pick-up and exergy efficiencies were 41.3% and 51.0%, respectively, for FBD-NHR and 40.4% and 57.7%, respectively, for FBD-WHR. The improvement potential ranged from 199.5 to 628.7 W for FBD-NHR and from 113.1 to 669.1 W for FBD-WHR, with average values of 295.6 and 247.7 W, respectively. The thermal dryer efficiencies varied from 3.5% to 29.6% and from 3.7% to 40.8% for FBD-NHR and FBD-WHR, respectively, with average values of 16.5% and 21.8%, respectively. Thermal energy savings of approximately 46.7% were achieved by using the FBD-WHR mode. (C) 2022 Elsevier Ltd. All rights reserved.