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- Title
Modeling of heat transfer in free down flowing laminar liquid films with development wavy structure at the regime of evaporation from the interface.
- Authors
Petrenko, Valentyn; Pryadko, Mykola; Zasyadko, Yaroslav; Miroshnyk, Mariya
- Abstract
Introduction. Within long vertical boiling tubes thermohydrodynamic processes in liquid film take place at a regime with cycling mixing of the film by the powerful waves. The existing Heat Transfer models of such phenomena do not take info account such processes. Materials and methods. The heat transfer and hydrodynamic processes that take place in down flowing film of water and sugar solutions at the regimes of evaporation from the interface have been studied. There were developed mathematical models, which then were compared with the result of direct experimentation of heat transfer in tubes at the regimes of solutions concentrations. Results and discussion.A mathematical model of heat transfer in laminar, heated to the saturation temperatures liquid films with the developed wavy structures on the free interface have been developed. The model takes into consideration cyclic relaxation of transient temperature field which happens right after the passage of a powerful big wave. The developed mathematical model describes the time history of the two dimensional temperature fields as a function of the Peclet number and the core characteristic of the wavy motion (the length of big waves). Based upon the proposed model a set of correlations have been obtained. These are proposed as a means for the generalization of heat transfer experimental data, obtained within the experimental studies of liquid films, heated to the saturation temperatures and evaporating from the interface. A generalized equation has been derived, which can be used for the calculations of Heat Transfer Coefficients (HTC) to the saturated sugar solutions liquid films. This equation contains wavy characteristics of down flowing films and valid within the range of parameters characteristic for the sugar industry evaporators, namely: concentrations - 0...70% dry matter; liquid mass flow rate density-0.01×10-3...0.6×10-3 m²/sec, the Peclet number range - 400...25000. The mathematical model of the temperature field cyclic relaxation turned out efficient for generalization of heat transfer experimental data not only laminar, but turbulent liquid films either, despite of the fact that the transport equations do not contain turbulent characteristics. Conclusions. A correlation between the liquid film wavy structure with the heat transfer has been established. The correlation is based upon the model of temperature field cyclic relaxation after passage of big waves. The respective correlations have been presented.
- Subjects
HEAT transfer
- Publication
Ukrainian Food Journal, 2016, Vol 5, Issue 1, p162
- ISSN
2304-974X
- Publication type
Article