Heat Transfer Kinetics and Temperature During the Drying Process of Thin, Wet Materials

The article presents a study of the kinetics of heat transfer using experimental data on the moisture exchange of thin flat ceramic, asbestos and felt wet plates based on the drying kinetics equation. The drying process was studied at a temperature of 90, 120, 150 °C and an air speed of 3, 5, 10 m/s. The relationships between moisture and heat exchange were established based on the drying kinetics equation, the Rehbinder number and the drying temperature coefficient. Based on the relative drying rate, equations for the heat flux density for the second drying period are established. Equations for the heat flux density for the second drying period based on the relative drying rate, equations for calculating average temperatures in the period of decreasing drying rate based on the drying temperature coefficient and the ratio of drying time by drying periods are determined. Relationships were established between complex variables, between the ratios of drying time by periods and the current moisture content to the critical one. It is demonstrated that cross-processing of experimental data on drying of specific materials allows to determine the critical moisture content of materials. A method for processing experimental data is presented for determining the critical moisture content of the material, experimental drying curves for ceramics, asbestos, and felt under different drying conditions. A formula is presented for determining the relative drying rate as a function of the ratio of the current moisture content to the critical one. The results of calculating heat flux densities, relative drying rates and average integral temperatures for the period of decreasing drying rate in the drying processes of ceramics, asbestos, and felt are presented, and a comparison of the calculated values with experimental data is provided. The error in the values lies within the error zone of the experimental data processing.

1. Lykov A. V. (1968) Drying Theory. Moscow, Energiya Publ. 472 (in Russian).

2. Akulich P. V. (2010) Calculations of Drying and Heat Exchange Installations. Minsk, Belaruskaya Navuka Publ. 443 (in Russian).

3. Krasnikov V. V. (1973) Conductive Drying. Moscow, Energiya Publ. 288 (in Russian).

4. Sazhin B. S. (1997) Scientific Fundamentals of Drying Techniques. Moscow, Nauka Publ. 447 (in Russian).

5. Rudobashta S. P. (1980) Mass Transfer in Systems with Solid Phase. Moscow, Khimiya Publ. 248 (in Russian).

6. Ol’shanskii A. I. (2013) Heat Transfer Kinetics and Experimental Methods for Calculating the Material Temperature in the Drying Process. Journal of Engineering Physics and Thermophysics, 86 (3), 584–594. https://doi.org/10.1007/s10891-013-0876-1

7. Lykov A. V., Kuts P. S., Ol’shanskii A. I. (1972) Kinetics of Heat Transfer in the Process of Drying Wet Materials. Inzhenerno-Fizichesky Zhurnal = Journal of Engineering Physics and Thermophysics, 23 (3), 401–406 (in Russian).

8. Zhuravleva V. P. (1972) Mass Transfer During Heat Treatment and Drying of Capillary-Porous Construсtion Materials. Minsk, Nauka i Tekhnika Publ. 189 (in Russian).

9. Ol’shanskii A. I., Gusarov A. M. (2017) Experimental Study of the Kinetics of Drying of Thin Plane Moist Materials by the Regular-Regime Method Using Generalized Complex Variables. Journal of Engineering Physics and Thermophysics, 90 (3), 665–678. https://doi.org/10.1007/s10891-017-1614-x

10. Ol’shanskii A. I., Zhernosek S. V., Gusarov A. M. (2018) Experimental Studies of Heat and Moisture Exchange in the Process of Convective Drying of Thin Wet Materials. Energetika. Izvestiya Vysshikh Uchebnykh Zavedenii i Energeticheskikh Ob’edinenii SNG = Energetika. Proceedings of CIS Higher Education Institutions and Power Engineering Associations, 61 (6), 564–578 (in Russian). https://doi.org/10.21122/1029-7448-2018-61-6-564-578

11. Filonenko G. K., Lebedev P. D. (1952) Drying Plants. Moscow, Leningrad, Gosenergoizdat Publ. 263 (in Russian).

12. Ol’shanskii A. I., Golubev A. N. (2024) Kinetics of Moisture Exchange During Convection Drying of thin Flat Wet Materials. Proceedings of the National Academy of Sciences of Belarus. Physical-Technical Series, 69 (3), 206–214 (in Russian). https://doi.org/10.29235/1561-8358-2024-69-3-206-214

13. Ol’shansky A. I., Kutz P. S. (1977) Some Patterns of Food Drying Kinetics. Izvestiya Vuzov. Pishchevaya Tekhnologiya = Izvestiya Vuzov. Food Technology, (5), 97–101 (in Russian).

14. Lykov A. V. (1956) Heat and Mass Transfer in Drying Processes. Moscow, Gosenergoizdat Publ. 464 (in Russian).

15. Kavkazov Yu. L. (1973) Heat and Mass Transfer in Leather and Footwear Technology. Moscow, Lyogkaya Promyshlennost Publ. 272 (in Russian).

16. Ol’shanskii A. I. (2013) Investigation of the Processes of Drying of Porous Ceramics by the Dokuchaev–Smirnov Method. Journal of Engineering Physics and Thermophysics, 86 (1), 80–87. https://doi.org/10.1007/s10891-013-0807-1