Drying characteristics of peppercorns in a rectangular fluidized-bed with triangular wavy walls

Abstract

An experimental study on drying kinetics of peppercorns has been conducted in two different drying fluidized-bed configurations: rectangular fluidized-bed ( RFB) and rectangular fluidized-bed with wavy walls ( RFBW). In the RFBW, two opposite triangular wavy walls with three blockage ratios ( e/ H) are formed to produce vortex/swirl flows leading to stronger turbulence and longer residence time of the flow in the bed. For each bed, three inlet hot airs ( T in) at 60 °C, 80 °C and 100 °C and two superficial air velocity, U* of 1.2 and 2.0 ( U* = U/ U mf) are introduced. The experimental results reveal that the air temperature and air velocity show significant effects on the drying rate of both beds, especially at T in = 100 °C and U* = 2.0. The RFBW performs much better than the RFB due to shorter drying time. The average drying time of the RFBW with e/ H = 0.3125, 0.3750 and 0.4375 is, respectively, around 29%, 36% and 43% less than that of the RFB. In addition, three mathematical drying models are offered for both the beds and the effect of the air temperature and velocity on the drying model constants was determined by fitting the experimental data using regression analysis techniques. The three models satisfactorily described the drying characteristics of peppercorns especially for the Henderson and Pabis model. The RFBW with e/ H = 0.4375 is preferable in the study.