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Helium-air counter flow through a rectangular channel

Pubblicazione


Autore: H. Zhao, M. Hishida, G. Tanaka

Collana: BT - 34 - Mag 06 - Energy: production, distribution and conservation

Note:
Helium-air counter flow in a round channel, a vertical and a horizontal rectangular channel were investigated experimentally focusing on investigation of the relationship between net mass inflow rate and tilted angle of the channels. The following conclusions were derived.
(1) The net mass inflow rate through the vertical rectangular channel was the highest and that thorough the horizontal rectangular channel was the next and that through the round channel was the lowest.
(2) Stratified counter flow was established in the vertical and horizontal rectangular channels for the whole range of the tilted angle (0 ≤ θ ≤ 90°).
Distributions of velocity and mole fraction of the helium-air counter flow as well as the net mass inflow rate through the vertical rectangular channel were numerically analyzed. The following conclusions were derived.
(3) Because of molecular diffusion of helium and air the helium-rich up-stream contained air and air-rich down-stream contained helium.
(4) Flow-area width of the helium-rich up-stream increased with the tilted angle of the vertical rectangular channel and flow-area width of the air-rich down-stream decreased
(5) Maximum axial velocity of the up-stream increased with increasing the tilted angle from 0 to 45°, whereas it remained almost the same in a titled angle range from 45° to 75°. It started to decrease with further increase in the tilted angle from 75° to 90°. On the other hand maximum axial velocity of the down-stream continued to increase with increasing the tilted angle from 0 to 90°.
(6) In accordance with the velocity distribution, the y-position where the mole fractions of helium and air were equal (=0.5) moved towards the bottom wall of the channel with increasing the tilted angle.
(7) The net mass inflow rate increased with the tilted angle and it reached the maximum value at the tilted angle of 60-75°. It started to decrease with further increase in the tilted angle beyond 60-75°. This was resulted from the fact that the width of flow-area of the air-rich down-stream decreased with the tilted angle.


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