Heat exchange – Casing or tank enclosed conduit assembly – Conduit coiled within casing
Patent
1990-01-02
1992-05-05
Flanigan, Allen J.
Heat exchange
Casing or tank enclosed conduit assembly
Conduit coiled within casing
2989003, 165162, 126400, F28D 104
Patent
active
051099209
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates, in a first aspect, to an improved method of manufacturing a heat exchanger element. Such elements are employed in heat exchangers, for instance of the kind used in cooling and heating systems for buildings. In a second aspect this invention concerns such a heat exchanger element itself, and a heat exchanger employing the heat exchange element. In a third aspect this invention concerns a reservoir suitable for housing the heat exchanger element to form a heat exchanger.
BACKGROUND ART
Known heat exchangers, of the kind used in cooling and heating systems for buildings, generally comprise a reservoir filled with a phase-change medium through which a plurality of parallel heat exchange circuit pass. The phase-change medium is usually aqueous-based and changes between water and ice in order to store and release coldness. Typically the tubes which comprise the heat exchanger element are disposed in coiled formations extending between an inlet manifold and an exhaust manifold.
A known heat exchanger element includes vertically disposed spacer elements which maintain the relative positions of the coils one above the other. The tubes are spaced closely together and their forward flow portions are interspersed with their return flow portions in order to minimise the temperature gradient throughout the phase-change medium. In this way ice is intended to form simultaneously throughout the phase-change medium and displace water upwards, thus preventing any build-up of pressure against the walls of the reservoir. However, in practice reservoirs are often constructed from flexible materials in order to accommodate some degree of expansion.
Heat exchange elements have customarily been made by winding plastics tubing into coils. This is a slow and cumbersome operation and it is almost impossible to wind coils with even spacing and without crushing or kinking the tubing. Uneven spacing leads to the appearance of temperature gradients in the phase-change medium, and kinking causes unacceptable pressure drops through the coils. In addition, the plastic tubing is taken from spools, each of which may hold, say, a 100 meters of tubing, and the tubing has a memory set into it which causes a tendency for it to resume the coiled shape in which it was wound on the spool. This tendency makes it even more difficult to wind the tubing into the coils required for the heat exchanger element, and also makes it very difficult to maintain the tubing coiled in the required configuration.
A further problem encountered in the manufacture of heat exchangers is that the elements are required to be rigidly restrained within the reservoirs in order to prevent movement resulting from their buoyancy. The restraint has to be sufficiently strong to survive the commissioning of the heat exchangers, when water is often pumped into the reservoirs without close supervision.
There are many other problems associated with known heat exchangers and heat exchanger elements and their manufacture. For instance it has proven difficult to pressure test the parts of the assembly during construction which has led to the need for expensive pre-commissioning testing.
DISCLOSURE OF INVENTION
According to a first aspect of the present invention, there is provided a method of manufacturing a heat exchanger element comprising the steps of:
(a) extruding a tube of deformable plastics material;
(b) winding the tube prior to curing to form a continuous spiral of tubing lying substantially in a plane;
(c) engaging the spiral of tubing along the length of at least one spacer bar in order to maintain the tubing in the spiral configuration;
(d) disposing a plurality of spirals of tubing one above the other; and
(e) arranging one end of each spiral in communication with an inlet manifold and the other end in communication with an outlet manifold.
The tube may be made of PVC or nylon or any other suitable material, but is preferably extruded from polyethylene pellets.
The tube is quenched before being wound, and the winding preferabl
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Flanigan Allen J.
Ice-Cel Pty. Limited
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