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Wood Science and Technology

, 43:43 | Cite as

Introducing an overall mass-transfer coefficient for prediction of drying curves at low-temperature drying rates

  • Rubén A. AnaniasEmail author
  • Eric Mougel
  • André Zoulalian
Original

Abstract

The aim of this study is to justify that the drying rate of wood can be represented by a phenomenological model defining a driving force expressed as the difference between the average wood moisture content and the equilibrium wood moisture content. The results show that the mathematical relation proposed is valid when introducing an overall mass transfer coefficient, K, at low temperature wood-drying rates.

Keywords

Transfer Coefficient Heat Transfer Coefficient Wood Sample Average Relative Error External Resistance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

a

Wood width (m)

ab

Stickers width (m)

ao, bo, co, n

Model constants

CP

Specific heat (J/kg K)

Dh

Hydraulic diameter (m)

e

Wood thickness (m)

eb

Stickers thickness (m)

E

Error (%)

G

Air flow rate (kg/s)

h

Overall heat-transfer coefficient (W/m2 K)

K

Overall mass-transfer coefficient (kg/m2 s)

kG

Mass-transfer coefficient (kg/m2 s Pa)

l

Wood length (m)

MO

Wood dry mass (kg)

Nu

Nusselt number

Pi

Partial pressure at the interface (Pa)

P

Partial pressure (Pa)

Pr

Prandt number

Re

Reynolds number

RH

Relative humidity (kg/kg)

S

Wood surface (m2)

t

Drying time (h)

T

Air temperature (°C)

TK

Air temperature (K)

Tw

Wet-bulb temperature (°C)

v

Air velocity (m/s)

\( \overline{x} \)

Moisture content (kg/kg)

\( \bar{x}_{\text{C}} \)

Critical moisture content (kg/kg)

xi

Initial moisture content (kg/kg)

\( \bar{x}_{\text{PSF}} \)

Fiber saturation point (kg/kg)

x*

Equilibrium moisture content (kg/kg)

λ

Air thermal conductivity (W/m K)

ρ

Air density (kg/m3)

μ

Air viscosity (kg/m s)

Ω

Heat of vaporization (J/kg)

Φ

Drying rate (kg/m2 s)

ΦMAX

Maximum drying rate (kg/m2 s)

Φ+

Reduced drying rate

φ

Non-dimensional parameters

Notes

Acknowledgments

The authors wish to thank Dr. Laurent Chrusciel (Université Henri Poincaré, France) and Professor Roger B. Keey (University of Canterbury, New Zealand) for their valuable advice and scientific assistance.

References

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Rubén A. Ananias
    • 1
    Email author
  • Eric Mougel
    • 2
  • André Zoulalian
    • 3
  1. 1.Departamento de Ingeniería en Maderas, Facultad de IngenieríaUniversidad del Bío-BíoConcepciónChile
  2. 2.ENSTIB-LERMABUniversité Henri PoincaréEpinalFrance
  3. 3.LERMABUniversité Henri PoincaréNancyFrance

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