THERMOHYDRODYNAMIC PROCESSES IN A SPRAYING CHAMBER WITH COUNTER-CURRENT HEAT FLOWS

The article deals with the results of thermohydrodynamic processes in a spraying chamber with direct gas flow and counter-current flows. The upper gas distribution device in a spraying chamber is shaped as a grid system, while the bottom device represents a branch pipe with a swirler pointing upwards. The chamber features counter-current flow interactions, and the bottom flow is introduced as a swirling jet. The experimental calculations of gas axial flow rates, temperature and thermal conductivity distribution in different chamber sections are provided. The thermal conductivity properties were determined with the normal mode method. The study was performed with ball-shaped sensors made of materials with high thermal conductivity (copper, brass) with centered thermocouples. The upper gas distribution system in the form of two grids (if no bottom gas inlet was involved) was found to build up an axisymmetric thermal conductivity model, and, consequently, the model-specific gas distribution in the spraying chamber. Referring to the study device, a hole (nozzle) near the burner results in asymmetric pattern, irregular gas distribution and generation of low-activity areas. Thermal conductivity values in the chamber central area turn to be higher than at the peripheral areas due to gas jet flow. Besides, heat exchange intensity in the chamber central area decreases significantly upon distance from the chamber floor. An extra bottom inlet of heat medium and creation of counter flows was shown to result in substantial increase in thermal conductivity (1.5–2 times) in the chamber central paraxial area and lower section, thus evidencing the hydrodynamic activation and heat and mass exchange intensification, which benefits to more effective use of chamber capacity and improved drying performance.

spray drying, heat exchange, hydrodynamics, drying kinetics, temperature distribution, normal mode, counter flows

1. Akulich P. V. Calculations of drying and heat exchange installations. Minsk, Belaruskaya navuka Publ., 2010. 443 p. (in Russian).

2. Akulich P. V. Thermohydrodynamic processes in drying techniques. Minsk, A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, 2002. 268 p. (in Russian).

3. Kudra T., Mujumdar A. S. Advanced Drying Technologies. New York, Marcel Dekker Inc., 2002. 459 p. Doi: 10.1201/9781420073898

4. Akulich P. V., Dragun V. L., Akulich A. V. Simulation and experimental study of spray drying thermohydrodynamic processes. Trudy tret’ei mezhdunar. nauch.-prakt. konf. «Sovremennye energosberegayushchie teplovye tekhnologii (sushka i termovlazhnostnaya obrabotka materialov) SETT−2008», 16−20 sent. 2008 g. T. 1 [Works of the 3rd International Scientific and Practical Conftrence “Modern power saving heat technologies (drying and thermo-moisturizing treatment of materials), SETT–2008”, September 16−20, 2008. Volume 1]. Moskow, 2008, pp. 124−129 (in Russian).

5. Mujumdar A. S. Handbook of Industrial Drying. Fourth Edition. CRC Press, 2014. 1348 p. Doi: 10.1201/b17208

6. Dolinskii A. A., Maletskaya K. D. Spray drying. Volume 1. Thermophysical basics. Methods of intensification and power saving technologies. Kiev, Akademperiodika Publ., 2011. 376 p. (in Russian).

7. Dolinskii A. A., Maletskaya K. D. Spray drying. Volume 2. Heat engineering and equipment for the production of powder materials. Kiev, Akademperiodika Publ., 2015. 390 p. (in Russian).

8. Rudobashta S. P. New Russian studies in drying and thermo-moisturizing processes. Trudy tret’ei mezhdunar. nauch.- prakt. konf. «Sovremennye energosberegayushchie teplovye tekhnologii (sushka i termovlazhnostnaya obrabotka materialov) SETT−2008», 16−20 sent. 2008 g. T. 1 [Works of the 3rd International Scientific and Practical Conftrence “Modern power saving heat technologies (drying and thermo-moisturizing treatment of materials), SETT-2008”, September 16−20, 2008. Volume 1]. Moskow, 2008, pp. 4−15 (in Russian).

9. Kuts P. S., Samsonyuk V. K. Enhancement of spray drying of thermosensitive materials. Drying Technology, 1989, vol. 1, no. 7, pp. 35–45. Doi: 10.1080/07373938908916573

10. Tutova E. G., Kuts P. S. Drying of microbiological products. Moskow, Agropromizdat Publ., 1987. 303 p. (in Russian).

11. Akulich P. V., Slizhuk D. S., Makarova O. D., Chizhik K. G. Thermohydrodynamic processes and technologies of fine materials manufacture with spray method. XV Minskii mezhdunarodnyi forum po teplo- i massoobmenu, 23–26 maya 2016 g.: tezisy dokladov i soobshchenii [XV Minsk International Forum on Heat and Mass Exchange: Theses of reports and announcements, May 23−26, 2016. Volume 3]. Minsk, Institute of Heat and Mass Transfer. A. V. Lykov, National Academy of Sciences of Belarus, 2016, pp. 87−90 (in Russian).

12. Isachenko V. P., Osipova V. A., Sukomel A. S. Heat transfer. Minsk, Energoatomizdat Publ., 1981. 416 p. (in Russian).

13. Wawrzyniak P., Podyma M., Zbicinski I., Bartczak Z., Polanczyk A., Rabaeva J. Model of Heat and Mass Transfer in an Industrial Counter-Current Spray-Drying Tower. Drying Technology, September 2012, vol. 30, no. 11−12, pp. 1274−1282. Doi: 10.1080/07373937.2012.704604