EXTREMAL INTENSIFICATION OF TURBULENT HEAT EXCHANGE IN A CHANNEL WITH AN INCLINED TRENCH OF OPTIMAL LENGTH

The extremal intensification of turbulent heat exchange in a narrow plane-parallel channel with an inclined trench
of optimal length, placed on its heated wall, as a result of the formation of a tornado-like vortex structure and
a transverse lumped pressure drop in the leading part of the trench was investigated. Correlation between the
increase in the indicated drop to a large value and the increases in the length of the trench to 0.1 in the case where
the trench shape is close to the shape of a spherical dimple and to 0.34 in the case of a long trench with a depth of
0.39, inclined to the channel wall at an angle of 45 ^o , has been established. It is shown that, as the length of a trench
in the channel increases, a detached turbulent flow in it is intensified, and the maximum velocities of the reverse
flow and of the secondary swirling flow reach 0.43 and 0.83, respectively, compared to 0.27 for a spherical dimple.
The minimum relative friction and the maximum relative heat transfer in the central cross section of the trench at
its inlet are stabilized at a level of –1.6 and 1.6 in the case where the trench has a length larger than 4. A maximum
relative heat transfer from the channel region of variable area with a long inclined trench, having spherical ends,
is attained in the case where the trench has a length of 3, and this maximum exceeds the maximum relative heat
transfer from the analogous channel region with a spherical dimple by 1.4–1.5 times

Author:  S. A. Isaev, D. V. Nikushchenko, A. A. Klyus, A. Yu. Chulyunin, Dechai Kon
Keywords:  detached flow, narrow channel, inclined trench, spherical dimple, tornado-like vortex, heat exchange, numerical simulation
Page:  1293