Kinetika konvektivnog sušenja tankog sloja iverja drva topole (Populus Deltoides)

Abstract

Drying of poplar wood (Populus Deltoides) particles was carried out at different drying conditions using a laboratory convective thin layer dryer. Drying curves were plotted and in order to analyze the drying behavior, the curves were fi tted to different semi-theoretical drying kinetics models. The effective moisture diffusivity was also determined from the integrated Fick’s second law equation and correlated with temperature using an Arrhenius- type model to calculate activation energy of diffusion. The results showed that Midilli et al. model was found to satisfactorily describe the drying characteristics of poplar wood particles dried at all temperatures and air flow velocities. In general, the drying rate increases with increasing air temperature and air fl ow velocity. A short constant drying rate period was observed and drying frequently took place at falling rate period in all cases. The effective moisture diffusivity of poplar wood particles increased from 1.01E-10 to 2.53E-10 m2·s-1 as the drying air temperature increased from 65 to 85 °C. The activation energy of diffusion for 1 m·s-1 and 1.5 m·s-1 air flow velocities were calculated as 27.8 kJ·mol-1 and 50.8 kJ·mol-1, respectively.Pri različitim uvjetima sušenja provedeno je sušenje iverja drva topole (Populus deltoides) uporabom konvektivne sušionice za tanki sloj iverja. Iscrtane su krivulje sušenja, a da bi se analizirao proces sušenja, krivulje su prilagođene različitim teorijskim kinetičkim modelima sušenja. Određena je i efektivna difuznost vode u drvu prema Fickovu drugom zakonu te je primjenom Arrheniusova modela za izračun aktivacijske energije difuzije korelirana s temperaturom. Rezultati su pokazali da model Midillija i suradnika zadovoljavajuće opisuje obilježja sušenja iverja drva topole pri svim temperaturama i brzinama strujanja zraka. U načelu, brzina sušenja povećava se s povećanjem temperature zraka i brzine strujanja zraka. Zabilježeno je kratko razdoblje konstantne brzine sušenja, a sušenje se najčešće postiže u razdoblju pada brzine sušenja. Efektivna difuzivnost vode u iverju drva topole povećana je s 1,01E-10 na 2,53E-10 m2·s-1 s povećanjem temperature zraka sa 65 na 85 °C. Izračunana je aktivacijska energija difuzije za 1 m·s-1 i 1,5 m·s-1 brzine strujanja zraka i iznosi 27,8 kJ·mol-1 i 50,8 kJ·mol-1