tailieunhanh - Mass Transfer in Multiphase Systems and its Applications Part 9

Tham khảo tài liệu 'mass transfer in multiphase systems and its applications part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Overall Mass-Transfer Coefficient for Wood Drying Curves Predictions 309 Fig. 3. Kiln drying curves of Spruce wood After Ananias et al. 2009a Fig. 4. Kiln drying curves of Beech wood After Ananias et al 2009a Wood Species e mm T C Tw C m s kg Reference Spruce 18 70 50 3 Ananias et al. 2009a Spruce 27 70 50 3 Spruce 41 70 50 3 Beech 30 70 50 2 Beech 30 70 50 5 Coigue 38 60 44 Ananias et al. 2009b Table 1. Overall-mass transfer coefficient 310 Mass Transfer in Multiphase Systems and its Applications 5. Conclusion Many low-temperature conventional wood drying curves can be predicted by a constant overall mass-transfer coefficient. The model presented has been tested on different wood drying schedules and the results obtained are very satisfactory. For these reasons it is suggested that it can be successfully used for drying schedule optimization at industrial scale. 6. List of symbols A a ab ao bo co n Cpa CpL Cpv dH e G H h K Ks Kg k kG l Mo Transfer surface m2 Wood width m stickers width m Model constants Air specific heat J kg. C Water-Liquid specific heat J kg. C Water-Vapor specific heat J kg. C Hydraulic diameter m Wood thickness mm Air flow rate kg s Specific humidity kg kg Overall heat-transfer coefficient W Overall mass-transfer coefficient kg Partial mass-transfer coefficient in air-phase kg Partial mass-transfer coefficient in solid-phase kg Mass-transfer coefficient non-dimensional Mass-transfer coefficient kg Wood length m Wood dry mass kg Overall Mass-Transfer Coefficient for Wood Drying Curves Predictions 311 Pi Pv PS RH S t T TK Tw TKw v Wp x XC Partial pressure at the interface Pa Partial pressure Pa Saturation pressure Pa Relative humidity kg kg Wood surface m2 Drying time h Air temperature C Air temperature K Wet-bulb temperature C Wet-bulb temperature K Air velocity m s Wetted perimeter m Moisture content kg kg Critical moisture content kg kg Xi XPSF X z Ah0 Ahv TiAX o V u u p