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Heat Pipe Science and Technology, An International Journal

Publicou 4 edições por ano

ISSN Imprimir: 2151-7975

ISSN On-line: 2151-7991

INVESTIGATION OF THERMOGRAVITY/THERMOCAPILLARY EFFECTS IN ROTATING HEAT PIPES: PREDICTION OF INSTABILITIES AT THE LIQUID FILM

Volume 5, Edição 1-4, 2014, pp. 221-229
DOI: 10.1615/HeatPipeScieTech.v5.i1-4.230
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RESUMO

Heat transfer and flow fields inside a high-speed-smooth-rotating heat pipe (RHP) - partly filled with liquid - are considered. The objective is to understand and quantify the influence of rotational speed on heat performance of such a device. In contrast with the classical and usual lubrication theory, the full Navier-Stokes equations are used in this survey to model the liquid flow in order to take into consideration the buoyancy effect under centrifugal effects. The Arbitrary Lagrangian-Eulerian (ALE) method was used in order to describe the moving liquid-vapor interface where capillary and thermocapillary forces are considered. So, two main phenomena may compete: the stabilizing centrifugal effect, which tends to maintain the liquid phase farther away from the axis of rotation than the vapor phase and therefore flattens the liquid-vapor interface, on the one hand, and the destabilizing buoyancy and thermocapillary effects, which tend to induce Rayleigh-Bénard/Marangoni instabilities, on the other hand. It is found that mainly Rayleigh-Bénard destabilizing effect significantly affects the system for moderate rotational speeds (~4000 rpm), where convective rolls appear at the evaporator and both: i) disturb the drainage of the liquid from the condenser zone to the evaporator zone and, ii) enhance liquid mixing. An analysis of dependence of the RHP conductance on the rotational speed is also performed.

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