Thermosiphon having improved efficiency

Abstract

The invention relates to an improved thermosiphon and to a method for transferring heat. The thermosiphon has a higher efficiency than existing thermosiphons because it does not rely on a pool-boiling evaporator but rather uses a forced-convection boiling evaporator. The inlet of the evaporator is located in its upper portion and is in fluid communication with a condenser. The fluid in its liquid phase enters the evaporator from its inlet in its upper portion and, by gravity, flows down the piping network of the evaporator, clinging on the inner surface of the tubes of the piping network. As the liquid flows down, it evaporates such that the fluid at the bottom of the evaporator is predominantly in a gaseous phase. The fluid in gaseous phase is then returned to the condenser.

Description

FIELD OF THE INVENTION [0001] The present invention generally relates to the field of heat exchangers. More particularly, the invention relates to an improved thermosiphon. BACKGROUND OF THE INVENTION [0002] A thermosiphon is a type of heat exchanger. The thermosiphon induces movement in a fluid by creating density gradients in the fluid through the exchange of heat. Currents are then generated by gravity as denser regions in the fluid tend to fall and the lighter ones tend to rise. [0003] A closed-loop thermosiphon is one that forms a closed circuit within which the fluid circulates. The fluid is heated in one part of the circuit. If the density of the fluid varies inversely with temperature—which is generally the case—the heating causes it to rise to another part of the circuit that is cooled. The heated fluid releases its heat in this cooled part of the circuit. The circulating fluid then falls back down to the heated part of the circuit to start the cycle once again. [0004] The ...

AI Technical Summary

Benefits of technology

[0017] Preferably, the inner surface of the pipe is textured to increase its surface roughness. Optionally, the piping network further comprises a wick located in contact with the inner surface of the pipe.

[0026] The present invention increases the heat transfer obtained by the thermosiphon to such a level that it becomes a viable alternative to costlier heat pipes, thermal wheels and direct air heat exchangers. Furthermore, the thermosiphon does not require geometrical constraints that may be inconvenient such as with heat pipes and thermal wheels that require the exhaust and intake ducts to be side-by-side. Since it operates with gravity, the thermosiphon only requires the exhaust duct to be at a lower elevation than the intake duct allowing for much greater liberty in the layout of a system of ducts. When that is not possible, a pump may be provided in the thermosiphon to move the fluid. The thermosiphon of the present invention may thus be used effectively in heat recovery schemes, considerably reducing the amount of heat required from the main heating systems.

Problems solved by technology

Hence, thermosiphons necessitate minimal maintenance, further contributing to their cost-effectiveness.

Although a very interesting product, existing thermosiphons are often overlooked for many applications because the heating they produced is not important enough to justify their use.

This is due to their inherent design limitations.

Unfortunately, for an application such as transferring heat from air evacuated from a building, pool boiling is not very effective.

Consequently, the rate of evaporation is relatively low, impairing the efficiency of the thermosiphon.

However, if either of the boiling or condensation processes is restricted or reduced, the other will be restricted or reduced as well.

Therefore, ineffective boiling in the evaporator prevents the condenser from functioning at full capacity.

Because the resulting heat transfer produced by thermosiphons is relatively low, their manufacturing and installation costs for heat recovery of evacuated air in buildings are not justified.

What are found on the market are more expensive alternatives such as heat pipes in which the flow is not driven by gravity but by capillary action.

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