The study of condensable vapour vortex flow in short low temperature heat pipes
Annotation
The results of computer studies of the vortex formation and the rotation direction changes of the vapour vortex inside short linear heat pipes (HP) with a Laval nozzle-shaped vapour channel are presented. For the first time it was found that a vapour toroidal vortex arising as an interaction result of the moist vapour flow with a normally oriented flat upper cover of HP can change the rotational motion direction. With a small temperature head on the evaporator, the direction of the toroidal vapour vortex rotation due to the Coanda effect and the sticking moving vapour jets to the channel’s walls comes from the periphery to the longitudinal axis of the channel. In this case, the radial flow of the condensate film along the upper cover to the capillary-porous insert located on the channel walls and the direction of motion of the adjacent layers of the vapour vortex are counterclockwise. The vapour vortex due to surface friction slows down the flow of the condensate film along the HP upper cover and thereby increases its effective thickness. With increasing the evaporator temperature head, the vapour vortex rotation direction changes to the opposite, from the longitudinal axis to the periphery of the vapour channel, and the direction of rotation of the adjacent layers of vapour and the of the liquid condensate film flow becomes tangled, which results in a sharp decrease of effective film thickness. The experimental results of the liquid condensate film thickness measurements obtained by capacitive sensors also show a sharp decrease in its thickness with an increase in the temperature head on the HP’s evaporator, which can be an indirect confirmation of the vapour vortex rotation direction change.
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