HEAT TRANSFER IN A THIN LIQUID LAYER UNDER CONDITIONS CHARACTERISTIC FOR THE LOWER COVER OF A THERMOSYPHON
| Autor: | Dmitry V. Feoktistov, Konstantin O. Ponomarev |
|---|---|
| Jazyk: | ruština |
| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Известия Томского политехнического университета: Инжиниринг георесурсов, Vol 332, Iss 4, Pp 57-69 (2021) |
| Druh dokumentu: | article |
| ISSN: | 24131830 2500-1019 2413-1830 78072727 |
| DOI: | 10.18799/24131830/2021/4/3148 |
| Popis: | The relevance. It is impossible to create new technologies for utilizing the heat of flue gases generated in various metallurgical processes and during the combustion of organic fuels in thermal power plants without the development of fundamental knowledge of heat transfer in energy-efficient, reliable thermodynamic systems based on thermosyphons. The relevance of the heat transfer study in a relatively thin liquid layer (no more than 10 mm) in a thermosyphon evaporator is justified by the necessity to develop mathematical models. These models are simpler than the ones based on Navier–Stokes equations or taking into account only the heat conduction mechanism. The purpose is to evaluate the contribution of thermogravitational convection to the heat transfer in a thin liquid layer under conditions characteristic of the thermosyphon lower cover, when the layer lower boundary is heated and there is evaporation from the upper boundary. Objects: liquid layer on the thermosyphon lower cover. Methods. The tracers trajectories in the liquid layer were determined using the shadow method. Tracer displacements were recorded using the Particle Tracking Velocimetry method using a special visualization system. The problem of thermal conductivity in a liquid layer is solved by the finite difference method. Results. Based on the experimental studies of heat transfer in a thin liquid layer, the effect of the heat flux density, the liquid layer thickness, and the properties of the coolant on the temperatures and velocities in this layer has been established. The conditions corresponded in terms of the main significant factors to the heating of the coolant on the thermosyphon lower cover. The increase in the heat flow and the coolant layer thickness was found to lead to intensification of circulation flows. It was shown that in the laminar flow regime (Ra=103÷5·105), the heat transfer intensity in the ethanol layer was higher than that of water. In addition, in a thin liquid layer (from 3,2 to 7,4 mm), the thermogravitational convection was much more intense than heat conduction. |
| Databáze: | Directory of Open Access Journals |
| Externí odkaz: |
|