GB1496327A - Two-phase thermosyphons - Google Patents

Abstract

1496327 Heat pipes INDUSTRY SECRETARY OF STATE FOR 11 Oct 1974 [11 Oct 1973 25 June 1974] 47497/73 and 28209/74 Heading F4U [Also in Division F1] A two-phase thermosyphon comprises a closed vessel 1 containing a liquid in equilibrium with its vapour and having an evaporator portion 4 adjacent a heat source 32 and a condenser portion 5 adjacent a heat sink, and a vapour lift pump for returning condensed liquid to the evaporator portion. As shown, the liquid drains into a sump 8 comprising a funnel portion 11 and an open-bottom cylindrical portion 23, which, together with the wall of the vessel 1 defines an annular heating compartment 10. A riser tube 12 having a T-shaped upper portion 22 connects the heating compartment 10 to an annular evaporator reservoir 7. In operation, on applying supplementary heat 9 to the heating compartment 10, from an external source or from an internal electrical heater, Fig. 2 (not shown), vapour bubbles are created in the compartment 10 producing a difference in density between the vapour/liquid mixture therein and the head of liquid in the sump 8 and thereby causing the lighter vapour/liquid mixture to flow up the tube 12. At the upper end of the tube 12, the vapour separates from the liquid, which falls into the evaporator reservoir 7, and passes, together with vapour from the reservoir, down the annular passage 24 between the tube 12 and the reservoir 7 to the condenser portion 5 where heat is given up by condensation of the vapour and the condensate 6 flows down into the sump 8. The tube 12 and compartment 10 may be located outside the vessel 1 and the evaporator surfaces may be provided with wicks to ensure satisfactory wetting. The vapour lift pump may be a multi-stage pump, and several different arrangements of alternative vapour lift pumps are described and illustrated.