Vortex intensification of heat exchange in rectangular section channel by the rotating disk on its wall

Аuthors

Usachov A. E.^1*, Isayev S. A.^2**, Usachov S. A.^3***

1. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia
2. Saint-Petersburg State University of Civil Aviation, 38, Pilotov str., St. Petersburg, 196210, Russia
3. Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), Zhukovsky, Moscow region, Russia

*e-mail: usachov_a@mail.ru
**e-mail: isaev3612@yandex.ru
***e-mail: sergeyech@mail.ru

Abstract

One of ways of an intensification of heat exchange at a current of gas or a liquid near to a solid surface is creation of a vortex-induced flow which essentially raises convective a component of a thermal stream. For this purpose, various generators of whirlwinds near to a surface, for example are widely used: dimples, trenches, ribs etc. Thus there is a question on power efficiency of a way of an intensification of heat transfer, namely: in how many time increases heat exchange in the channel with artificial obstacles in comparison with growth of hydraulic losses. However, there are cases when it is necessary to raise considerably intensity of heat exchange, without reckoning with power expenses. They arise aviation, space vehicles, in power cars etc. at in rigid restrictions on useful volume. In the given work possibility of a considerable intensification of heat exchange near to a firm wall is analyzed at small power expenses for creation of a vortex current by means of a rotating disk.

In the presented research the turbulent three-dimensional noisothermal current of water and heat exchange in the channel with the rectangular cross-section section numerically is modelled, one of which walls is exposed to constant heating. On bottom hot to a channel wall the rotating disk which surface coincides with a channel wall is located. At disk rotation in the channel there is an intensive vortex flow which raises heat transfer from hot walls in a liquid stream.

As a result of research it is shown that installation of a rotating disk on a wall of the channel of rectangular section leads to occurrence of a large-scale eddy flow and, as consequence, a heat exchange intensification closes the bottom hot wall approximately in 2.5 times in comparison with the channel without a disk.

One of the heat exchange intensification ways while gas or liquid flow near the solid surface consists in vortex flow creating, which increases significantly the convective component of a heat flow. Various vortex generators near the surface, such as dimples, trenches, ribs etc., are widely used for this purpose. A question of energy efficiency of the heat exchange intensification arises herewith, namely, how many times the heat exchange increases in the channel with artificial obstacles compared to the hydraulic losses growth. However, there are certain cases when considerable heat exchange increase is necessary regardless of energy consumption. They arise in aviation and space vehicles, energy machines etc. at strict limitations the effective volume. The presented work analyses the possibility of considerable heat exchange intensification near the solid wall at low energy consumption on the vortex flow creation by the rotating disk. The presented study numerically models turbulent 3D non-isothermal water flow and heat exchange in the rectangular cross-section channel, one of which walls is being exposed to the constant heating. A rotating disk, which surface coincides with the channel wall, is located on the lower heated wall of the channel. The intensive vortex flow, which increases the heat drainage from the heated wall into the fluid flow, occurs while the disk rotation. The results of the study revealed that the rotating disk setting on the wall of the rectangular cross-section channel led to occurrence of a large-scale eddy, and, as a consequence, to the heat exchange intensification near the heated lower wall approximately by 2.5 times compared to the channel without a disk.

Keywords:

Nnumerical simulation, vortex intensification, heat transfer, turbulence, SST turbulence model, pack VP2/3.

References

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