RESEARCH OF THE PROCESSES OF HEAT AND MASS TRANSFER DURING HEATING OF WOOD IN AN UNSATURATED ENVIRONMENT

UDC 674.04.047.3

  • Rudak Oksana Gennadievna − Master of Engineering, Senior Lecturer, the Department of Technology and Design of Wooden Articles. Belarusian State Technological University (13a, Sverdlova str., Minsk, 220006, Republic of Belarus). E-mail: oksrudak@mail.ru

DOI: https://doi.org/10.52065/2519-402X-2021-246-35-277–283

Key words: heating, thermal and moisture conductivity, heat and mass transfer, temperature gradient, equation, thermal conductivity.

For citation: Rudak О. G. Research of the processes of heat and mass transfer during heating of wood in an unsaturated environment. Proceedings of BSTU, issue 1, Forestry. Nature management. Processing of Renewable Resources, 2021, no. 2 (246), pp. 277–283 (In Russian).DOI: https://doi.org/10.52065/2519-402X-2021-246-35-277–283.

Abstract

The article describes the results of a study of the heating mechanism in an unsaturated environment. It is noted that during the initial heating, both the temperature and the moisture content of the wood on the sample surface change. It is concluded that in the process of heating in wood, two jointly occurring processes of heat transfer occur: thermal conductivity directed from the surface layers of the assortment to the inner ones, and moisture conductivity in the opposite direction. In this work, attention is drawn to the fact that the initial heating of wood refers to a non-stationary regime, since there is a time-varying and cross-sectional temperature of the sample itself (surface – inner layer), as well as the temperature of the treatment agent. The process of initial heating of wood in an unsaturated environment is characterized by the formation of three zones along the thickness of the sample: diffuse with a moisture content below Wlg; zone of evaporation of free moisture (the average moisture content of wood here is higher than Wlg); capillary zone with approximately the same moisture content throughout the thickness above Wlg. Since both a temperature difference and a humidity difference are formed over the cross section (thickness) of the sample during the heating period, the total moisture flow takes into account the total effect of the moisture content and temperature gradients. From the basic law of moisture movement and the law of thermal conductivity for wood, a system of equations was obtained that allows simulating the movement of heat and moisture during heating in an unsaturated environment.

Download

References

  1. Rudak O. G., Korob A. Yu. Investigation of the nature of changes in the humidity of the surface and inner layers of pine wood during heating in an unsaturated environment. Trudy BGTU [Proceedings of BSTU], 2021, issue 1 (240): Forestry. Nature Management. Processing of Rrenewable Resources, pp. 162–169 (In Russian).
  2. Rudak O. G., Snopkov V. B. Changes in the thermal properties of wood during heating in an unsaturated environment. Trudy BGTU [Proceedings of BSTU], 2012, no. 2 (149): Forest and Woodworking Industry, pp. 161–164 (In Russian).
  3. Rudak O. G. Investigation of the phenomenon of thermal and moisture conductivity during the heating of wood in an unsaturated environment. Trudy BGTU [Proceedings of BSTU], 2020, no. 2 (234): Forestry. Nature Management. Processing of Renewable Resources, pp. 233–238 (In Russian).
  4. Rudak O. G. Change in the moisture content of lumber by thickness when heated in an unsaturated environment. Trudy BGTU [Proceedings of BSTU], 2012, no. 2: Forest and Woodworking Industry, pp. 165–167 (In Russian)
  5. Rudak O. G., Guz Yu. A., Snopkov V. B. Study of the stress-strain state of wood when heated in an unsaturated environment. Energo- i materialosberegayushchiye ekologicheski chistyye tekhnologii: tez. dokl. IX Mezhdunar. nauch.-tekhn. konf. [Energy-and material-saving, environmentally friendly technologies. IX international scientific and technical conference]. Grodno, 2011, pp. 30–31 (In Russian).
  6. Lykov A. V. Teplo- i massoobmen v protsessakh sushki [Heat and mass transfer in drying processes]. Moscow, GosEnergoIzdat Publ., 1956. 463 p.
  7. Shubin G. S. On the coefficients of heat and moisture transfer in wood Derevoobrabatyvayushaya promyshlennost’ [Woodworking industry], 1989, no. 8, pp. 10–13 (In Russian).
  8. Chudinov B. S. Teoriya teplovoy obrabotki drevesiny [Theory of wood heat treatment]. Moscow, Nayka Publ., 1968. 255 p.
  9. Sergovsky P. S., Rasev A. I. Gidrotermicheskaya obrabotka i konservirovaniye drevesiny [Hydrothermal processing and preservation of wood] Moscow, Lesnaya promyshlennost’ Publ. 1987. 360 p.
  10. Shubin G. S. Sushka i teplovaya obrabotka drevesiny [Drying and heat treatment of wood]. Moscow, Lesnaya promyshlennost’ Publ., 1990. 335 p.
  11. Lykov A. V. Teplo- i massoobmen v protsessakh sushki [Methods of determining thermal conductivity and thermal conductivity]. Moscow, Energia Publ., 1973. 413 p.
  12. Shubin G. S. On Thermal Conductivity of Colloidal Capillary-Porous Bodies. Materialy VI Vsesoyuznoy konferentsii po teplomassoobmenu [Materials of the VI All-Union Conference on Heat and Mass Exchange]. Minsk, 1980, vol. 7, pp. 18–25 (In Russian).
22.03.2021