Capillary pumped heat transfer loop

Details Capillary pumped heat transfer loop Capillary pumped heat transfer loop

1998-01-28

1999-08-31

Atkinson, Christopher

Heat exchange

Intermediate fluent heat exchange material receiving and...

Liquid fluent heat exchange material

16510427, 16510724, F28D 1500

Patent

active

059440929

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a capillary pumped heat transfer loop comprising at least one evaporator, at least one condenser and a reservoir for storing a heat transfer fluid, said evaporator comprising an output connected by a vapour line to an input of the condenser, an output of the condenser being connected to the reservoir, said evaporator comprising an evaporator body and being provided with a porous material provided for producing a capillary pumping pressure inside the loop and applying that pressure on the heat transfer fluid starting from the surface of the material in contact with the evaporator body, said evaporator being also provided for evaporating the heat transfer fluid by heat absorption.
Such a capillary pumped loop is known from the publication "Computer model of satellite Thermal Control System Using a controlled capillary pumped loop" of K. A. Goncharov, E. Yu Kotlyarov and G. P. Serov published in SAE Technical Paper Series n.degree. 932306. Such loops are for example used in satellites and enable a thermal transfer from one heat source, for example an electronic equipment, towards the condenser where the collected heat is dissipated. The loop is of course not limited to applications in weightlessness because it also operates in the presence of gravity. The porous material present in the evaporator comprises an axial channel which enables to feed the porous material with heat transfer fluid. The saturation with liquid of the porous material enables the creation of a capillary pressure. It is that capillary pressure which will enable the circulation of the vapour from the evaporator towards the condenser as well as the flow-back of the condensed fluid towards the evaporator without using mechanical pumping means. The loop configuration enables a circulation from the evaporator towards the condenser and then towards the reservoir, which feeds on his turn the evaporator in heat transfer fluid. The capillary material of the evaporator is in such a manner fed with heat transfer fluid and is thus permanently saturated with fluid. In such a manner the capillary material enables to develop capillary pumping pressures which are able to compensate the loss of charges inside the loop. The obtained capillary pressure with the actually known capillary materials enables to pump heat transfer fluid from the condenser towards the evaporator even at a height of several meters under the influence of gravity.
If before the circulation of the vapour, the loop is at rest with the evaporator over the condenser, the heat transfer fluid completely fills the fluid line, the vapour line, and the condenser, and partially the whole evaporator. The fluid of the vapour line and the condenser will be pushed up by the vapour produced by the evaporator to the reservoir. That pushing force originates from the pressure difference between the evaporator and the reservoir caused by the external heat flux applied to the evaporator, which flux causes in first instance an increase of the temperature of the evaporator. The volume of liquid vis-a-vis the volume of vapour comprised within the reservoir thus depends on the volume of vapour vis-a-vis the volume of liquid which is in the vapour line and the condenser. That loop with phase change and capillary pumping is qualified as "auto-start", because it doesn't require an annex device nor a special start up procedure. It is indeed the thermal flux applied at the level of the evaporator which provokes the start of the loop.
A drawback of the known loop is that the evaporator and the reservoir are linked for forming an inseparable whole. The temperature of the reservoir is essentially determined by the parasitic thermal flux circulating from the evaporator towards the reservoir. The pressure applied within the reservoir depends on the temperature and so the pressure and vaporisation and condensation temperature at which the heat transfer occurs inside the loop is equal to the temperature of the reservoir. The temperature of the heat source is thus not sufficiently regulat

REFERENCES:
patent: 4312402 (1982-01-01), Basiulis
patent: 4516631 (1985-05-01), Russell
patent: 4523636 (1985-06-01), Meijer et al.
patent: 4957157 (1990-09-01), Dowdy et al.
patent: 5103897 (1992-04-01), Cullimore et al.
patent: 5117901 (1992-06-01), Cullimore
patent: 5303768 (1994-04-01), Alario et al.

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