Published Date

First online: 18 February 2016

Factors affecting the moisture content (MC) measuring during radio-frequency/vacuum (RF/V) drying

• HongHai Liu 
• , Lin Yang
• , Zhihui Wu
• , Kazuo Hayashi
• , Xingchang Li

• 
  

• Abstract 

• 
  

Radio-frequency/vacuum (RF/V) drying has been widely used in modern wood industry, but the key technology and mechanism for moisture content measuring during RF/V are still unknown. In this study, the aim was to measure moisture content using temperature, pressure and equilibrium moisture content during RF/V drying. The effects of drying schedules, drying time, ambient conditions in the chamber etc. on moisture content measuring were investigated during RF/V drying. In total 14 runs with different conditions were tested. The results showed that the accuracy of the moisture content measured was highly consistent in all tests either with pre-vacuum treatment or without treatment. When the drying time during RF/V reaches a certain point, there is no significant difference in moisture content measuring between pre-vacuum treatment and non-treatment. However, moisture content measuring at locations close to surfaces or open end of the timber was significantly affected by the ambient temperature and pressure condition in the drying chamber.


References

1. Avramidis S, Zwick LR (1997) Commercial scale RFV drying of softwood lumber. Part 3 Energy consumption and economics. For Prod J 47(1):48–56
2. Cai YC, Hayashi K (2001) Pressure and temperature distribution in wood during RF/vacuum drying. In: 7th IUFRO International Wood Drying Conference, Tsukuba, Japan, pp 386–391
3. Cai YC, Hayashi K (2002) Contribution of evaporation from transverse sections to drying rate during radio-frequency/vacuum drying. Mokuzai Gakkaishi 48(2):73–79
4. Cai YC, Hayashi K (2007) New monitoring concept of moisture content distribution in wood during RF/vacuum drying. J Wood Sci 53(1):1–4CrossRef
5. Chen ZJ, Fred ML (2001) The primary driving force in wood vacuum drying. In: 7th IUFRO International Wood Drying Conference, Tsukuba, Japan, pp 386–391
6. Chen ZJ, Fred ML (2002) Theoretical equilibrium moisture content of wood under vacuum. Wood Fiber Sci 34(4):553–559
7. Goreshnev MA, Kazarin AN, Lopatin VV, Sekisov FG, Smerdov OV (2013) Combined timber drying method. J Eng Thermophys-Rus 86(2):336–339CrossRef
8. Gu LB (2009) Present situation of Chinese wood drying equipment and technology and the difference of international advanced level. Wood Process Mach (S), pp 22–28
9. Koumoutsakos A, Avramidis S, Hatzikiriakos SG (2001) Radio frequency vacuum drying of wood. II. Experimental model evaluation. Dry Technol 19(1):85–98CrossRef
10. Lazarescu C, Avramidis S (2012) Heating characteristics of western hemlock (Tsuga heterophylla) in a high frequency field. Eur J Wood Prod 70(4):489–496CrossRef
11. Lazarescu C, Bedelean B, Avramidis S (2012) Heating characteristics of softwood in a high frequency field. ProLigno 80(4):18–26
12. Lee NH, Li CY, Zhao XF, Park MJ (2010) Effect of pretreatment with high temperature and low humidity on drying time and prevention of checking during radio-frequency/vacuum drying of Japanese cedar pillar. J Wood Sci 56(1):19–24CrossRef
13. Li XJ, Wu QL, Jiang W, Zhang BG (2006) Mechanism of moisture movement in wood during microwave vacuum drying. J Beijing For Univ 28(3):150–153
14. Li XL, Gao RQ, Gou T, Zhang LB, Chen ZJ (2012) Radio frequency/vacuum drying for boxed-heart square timber of plantation larch. Sci Silv Sin 48(9):127–131
15. Liu HH, Yang L, Cai YC, Masatoshi S, Hayashi K (2010a) Effect of EMC and air in wood on the new in-process moisture content monitoring concept under radio-frequency/vacuum (RF/V) drying. J Wood Sci 56(2):95–99CrossRef
16. Liu HH, Yang L, Cai YC, Sugimor M, Hayashi KZ (2010b) Effects of ambient pressure on equilibrium moisture content of wood. Wood Fiber Sci 42(3):346–351
17. Liu HH, Yang L, Cai YC, Hayashi KZ, Li KF (2014) Distribution and variation of pressure and temperature in wood cross section during radio-frequency vacuum (RF/V) drying. Bioresources 9(2):3064–3076
18. Lopatin VV, Goreshnev MA, Sekisov FG (2014) Moisture transport in birch lumber at low radio-frequency and contact vacuum drying. Holz Roh Werkst 72(6):779–784CrossRef
19. Myojin MY, Yasujima M, Hayashi KZ (2006) Development of hot blow vacuum drying kiln (1). Full size dry kiln suitable for production of high quality hardwood lumber. Mokuzai Kogyo 61(3):105–109
20. Sasaki K, Kawabe J, Mori M (1987) Vacuum drying of wood with high frequency heating (II), the pressure within lumber during evacuation and drying. Bull Kyushu Univ For 57:245–265
21. Watanabe K, Abubakari A, Lazarescu C, Avramidis S (2011) Softwood heating in radio frequency fields. Eur J Wood Prod 69(2):295–301CrossRef
22. Xiao H, Cai YC (2009) Factors affecting relative humidity during wood vacuum drying. J For Res 20(2):165–167CrossRef
23. Yi SL, Zhou YD, Liu YR, Zhang BG, Feng XJ (2008) Experimental equilibrium moisture content of wood under vacuum. Wood Fiber Sci 40(3):321–324
24. Zhang L, Avramidis S, Hatzikiriakos SG (1997) Moisture flow characteristics during radio-frequency/vacuum drying of thick lumber. Wood Sci Technol 31(4):265–277CrossRef

For further details log on website :
http://link.springer.com/article/10.1007/s00107-016-1017-2