Background of the Invention The present invention relates to a device and a connector for supplying fluid to a heat exchanger cavity, and in particular to an auto-filling device and a side connector for a heat exchanger such as the Rotex Sanicube™. The present invention also relates to a heat storage element, and in particular to a heat storage element for use in heat storage vessels such as the Rotex Sanicube™.

Description of the Prior Art

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge.

An example of a Rotex SC500 heat exchanger or equivalent, which is also referred to as a "Rotex Sanicube™", is shown in Figure 1.

In this example, the heat exchanger is formed from a housing 1, which contains a primary water circuit 2, an optional electric heating element 3, and a hot water supply 4. In use, the housing 1 defines a cavity 5, which is typically filled with water 5 A to help retain and distribute heat.

The primary water circuit is usually the main source of heating of the water 5 A, and is typically formed from a copper or metal pipe 2A, having an inlet 2B and outlet 2C to allow the pipe 2A to be interconnected with sources of waste heat. The electric element 3 provides additional heating of the water 5A if required, and may for example include an Incalloy 800 element or equivalent. The hot water supply 4 is typically formed from a PE-X heat exchange pipe 4 having an inlet 4A and an outlet 4B.

hi use, the water 5A in the cavity 5 is heated either by recirculating hot water from heat sources via the primary water circuit 2, or through use of the heating element 3. The water 5 A operates to retain heat and to provide heating of the water in the hot water supply 4. A number of side connectors 6 are also typically provided to allow the water 5A to be recirculated to provide additional heating. However, such systems currently suffer from a number of drawbacks.

For example, in order to ensure the system has the required level of water 5 A, it is necessary to remove a lid IA and fill the housing 1 manually using a hose. Furthermore, the water levels in the housing 1 must be periodically checked, and replenished in a similar manner to ensure efficient operation. As these operations require removal of the lid IA which includes the inlets 2B, 4B, the outlets 2C, 4D and the heating element 3, this must be performed by an engineer. This in turn results in high service costs, particularly in remote regions.

This problem is exacerbated when additional heating sources are used. In particular, constant recirculation of the water requires that water levels are checked more frequently. Furthermore current plastic side connections 6 limit the fluid flow causing balance and overflowing problems. Finally, the current connections have a problem of "free spinning", which loosens the connections and causes leaking which in turn results in damage and major cost for rectification.

Thus, in many cases it is not suitable to use the side connections for additional heat sources.

Additionally, such systems utilising water only to store heat only have a limited storage capacity.

Summary of the Present Invention In a first broad form the present invention provides a device for supplying fluid to a heat exchanger cavity, the device including: a) a housing defining a cavity; b) an inlet coupled to an external fluid source; c) a pipe for connecting the cavity to the inlet; d) a valve for selectively opening the inlet; e) a float; f) a coupling for connecting the float to the valve to thereby actuate the valve in accordance with the level of fluid in the heat exchanger cavity. Typically, in use, the inlet is aerially disconnected from fluid in the heat exchanger cavity.

Typically, in use, an air cavity is formed in the housing between the inlet and the float.

Typically the coupling includes a push rod.

Typically an end of the push rod forms a valve head which cooperates with a valve seat provided in the inlet.

Typically the push rod is positioned within the pipe.

Typically the pipe includes an inner pipe defining a flow path between the inlet and the cavity.

Typically the device is formed at least in part from heat insulating material.

In a second broad form the present invention provides a heat exchanger incorporating a fluid supply according to the first broad form of the invention.

The heat exchanger is typically a Rotex heat exchanger.

hi a third broad form the present invention provides a connector for providing fluid communication with a heat exchanger cavity, the connector including: a) a pipe extending through a wall into the heat exchanger cavity for connecting the cavity to a flow path; b) an end piece coupled to the pipe and positioned within the cavity, the end piece including at least one lug and a gasket; and, c) a coupling wherein in use the coupling is adapted to urge the end piece against an inner surface of the cavity thereby causing the lug to be embedded in the wall, and the gasket to rest against the inner surface, thereby creating a seal.

Typically the coupling is formed from a locking nut which cooperates with a threaded portion of the pipe.

Typically, in use, the threaded portion couples the pipe to an external pipe defining the flow path.

Typically the external pipe is coupled to the threaded portion using a sealing nut. Typically the connector is a side connector for a Rotex heat exchanger.

In a fourth broad form the present invention provides a heat exchanger incorporating a connector according to the third broad form.

Typically, the heat exchanger is a Rotex heat exchanger.

Typically the heat exchanger of the fourth broad form of the invention can include a device according to the first broad form of the invention.

Typically the heat exchanger includes at least two connectors for recirculating the fluid to at least one of: a) at least one external heat source; and, b) at least one other heat exchanger.

Typically the external heat source includes at least one of: a) waste heat from at least one of: i) a generator; ii) air conditioning equipment; and, iii) a boiler; and, b) solar collectors.

Typically the heat exchanger includes a heat storage element including: a) a housing defining an elongate cavity, the housing being formed from an elongate body and two end caps; and, b) a phase change material positioned in the cavity, the phase change material being selected in accordance with an intended operating temperature of the heat storage element.

In a fifth broad form the present invention provides a heat exchanger for using multiple heat sources, the heat exchanger including: a) a heat exchanger cavity: b) device for supplying fluid to the heat exchanger cavity, the device including: i) a housing defining a cavity; ii) an inlet coupled to an external fluid source; iii) a pipe for connecting the cavity to the inlet; iv) a valve for selectively opening the inlet; v) a float; vi) a coupling for connecting the float to the valve to thereby actuate the valve in accordance with the level of fluid in the heat exchanger cavity; and, c) a connector for providing fluid communication with a heat exchanger cavity, the connector including: i) a pipe extending through a wall into the heat exchanger cavity for connecting the cavity to a flow path; ii) an end piece coupled to the pipe and positioned within the cavity, the end piece including at least one lug and a gasket; and, iii) a coupling wherein in use the coupling is adapted to urge the end piece against an inner surface of the cavity thereby causing the lug to be embedded in the wall, and the gasket to rest against the inner surface, thereby creating a seal.

Typically the heat exchanger includes at least two connectors for recirculating the fluid to at least one external heat source.

In a sixth broad form the present invention provides a hot water supply system including: a) a number of heat exchangers, each heat exchanger including: i) a housing defining a cavity containing a fluid; ii) first and second side connectors for connecting the cavity to a heat source to allow for heating of the fluid; iii) a heat exchange pipe extending from an inlet to an outlet through the cavity, thereby allowing water flowing from the inlet to the outlet to be heated by fluid in the cavity; and, b) at least one heat source, the heat source being connected to each of the heat exchangers via the respective side connectors.

Typically the heat exchangers are connected to the heat source in parallel, although serial connections may be used. Typically the heat source includes a heat source outlet coupled to the first side connector of each heat exchanger and a heat source outlet coupled to the second side connector of each heat exchanger, the first side connector being positioned above the second side connector.

Typically the heat exchangers further include a third side connector, the third side connectors being interconnected via a pipe to form a balance line.

Typically the side connectors are connectors according to the third broad form of the present invention.

In a seventh broad form the present invention provides a heat storage element including: c) a housing defining an elongate cavity, the housing being formed from an elongate body and two end caps; and, d) a phase change material positioned in the cavity, the phase change material being selected in accordance with an intended operating temperature of the heat storage element.

Typically the housing is formed from at least one of: a) a thermoplastic; b) a polyolefine; c) polyethylene, and, d) polypropylene.

Typically the housing has a substantially cylindrical shape.

Typically the housing has a length in the region of 1200mm to 1300mm.

Typically the housing has a diameter in the region of 70mm to 80mm.

Typically the phase change material is at least one of: a) a hydrated salt; b) calcium chloride dihydrate; c) calcium chloride hexahydrate; d) sodium phosphate heptahydrate; e) sodium phosphate dodecahydrate; f) sodium acetate trihydrate; and, g) magnesium nitrate hexahydrate.

Typically the phase change material is selected dependent on the intended application.

Typically the end caps are heat sealed to the body to thereby seal the cavity.

Typically the apparatus is adapted to be incorporated into a Rotex Sanicube heat exchanger.

In an eighth-broad form the present invention provides a hot water supply apparatus including: a) a heat storage vessel including: i) a vessel housing defining a fluid filled vessel cavity; ii) at least one heat source for heating fluid in the vessel cavity; and, iii) at least one heat exchange pipe extending through the vessel cavity, the heat exchange pipe having an inlet coupled to a water source and an output for supplying hot water; and, g) at least one heat storage element including: i) a housing defining an elongate cavity, the housing being formed from an elongate body and two end caps; and, ii) a phase change material positioned in the cavity, the phase change material being selected in accordance with an intended operating temperature of the heat storage element.

Typically the at least one heat source includes at least one of: a) a heating element; and, b) a second heat exchanger coupled to a source of hot fluid.

Typically the hot fluid is heated by at least one: a) waste heat from equipment; and, b) solar heating.

Typically the heat storage vessel is a Rotex™ SC500.

Brief Description of the Drawings An example of the present invention will now be described with reference to the accompanying drawings, in which: - Figure 1 is a schematic side view of an example of a heat exchanger; Figure 2A is a schematic side view of an auto-filling device; Figure 2B plan view of the auto-filling device of Figure 2A; Figure 2C is a schematic cross-sectional view of the auto-filling device of Figure 2 A; Figure 3 A is a schematic cross-sectional view of an example if a side connector; Figure 3B plan view of the side connector of Figure 2 A; Figure 3 C is a schematic side view of the side connector of Figure 3 A; Figure 3D is a schematic side view of the back nut of Figure 3C; Figure 3E is a schematic plan view of the back nut of Figure 3C; Figures 4A to 4D are schematic views of a number of interconnected heat exchangers; Figure 5 is a schematic cross section view of an example of a heat storage element; Figure 6 is a schematic plan view of a number of heat storage elements arranged in the heat exchanger of Figure 1; and, Figure 7 is a schematic plan view of a number of heat storage elements arranged in the heat exchanger of Figure 1.

Detailed Description of the Preferred Embodiments An example of an auto-filling device will now be described with reference to Figures 2A to 2C.

In this example, the auto-filling device is formed from a mounting 10 fitted in the lid IA of a heat exchanger such as the Rotex Sanicube™ shown in Figure 1. A pipe 11 is provided in the mounting to couple a housing 12 to an inlet 13. The inlet 13 includes a connector 14 to allow an external water source to be coupled thereto.

As shown in more detail in Figure 2C, the housing 12 includes a float 15 coupled to a valve head 17 via a push rod 16, provided within an inner pipe 18. The valve head 17 cooperates with a valve seat 19 provided in the inlet 13.

In use, the float 15 floats in the water 5 A as shown. If the water level is sufficiently high, the valve head 17 is pushed against the valve seat 19 and the inlet 13 remains closed. In the event that the level of the water 5A falls, then the level of the float will fall, thereby releasing the valve head 17. This in turn causes the inlet 13 to be opened, such that water from the external water supply passes through the inner pipe 18, and into the housing 12. As a result the water 5 A in the housing 1 is replenished automatically.

It will be appreciated that the relative buoyancy of the float 15, will control the force used to urge the valve head 17 against the valve seat 19 for a particular water level 5 A within the housing 1. This will be counteracted by the pressure of the external water supply, and as a result, the relative buoyancy of the float 15, and the pressure of the external water supply can be adjusted to control the ultimate level of water 5 A in the housing 1.

In use, the device aerially disconnects the external water supply from the contents of the housing 12 due to the presence of an air cavity 21, which separates the inlet 13 from the water 5A. This prevents heat loss through fluid communication between the external water source and the water 5 A via the inlet 13. Furthermore, the restricted diameter of the inner pipe 18 prevents heat loss by convection of the air in the cavity 21.

By ensuring that the housing 12 extends below the water level 5 A, this also ensures that there is no flow of air 20 into the air cavity 21 once the housing has been initially filled.

It will be appreciated that this therefore minimises heat loss from the heat exchanger, and by aerially disconnecting the supply, also satisfies legal requirements, such as the AS3500, as well as assisting to reduce service requirements.

Finally by forming the device from suitable insulating materials, such as thermosetting plastics, or the like this can further prevent heat loss.

An example of an improved side connection will now be described, with reference to Figures 3 A to 3F.

In this example, the side connection 25 is formed from a pipe 26 have an external threaded portion 27, and an end piece 28. The end piece 28 includes four lugs 29 which project from the end piece 28 in a direction parallel to the pipe 26. A sealing gasket 30 is also provided.

In use, the side connection is provided in a heat exchanger, such as the heat exchanger shown in Figure 1, by inserting the side connector 25 through an aperture provided in housing 1, such that the pipe 26 projects outwardly from the housing 1, with the lugs resting against an inner surface IB as shown. A back nut 31 is threaded onto the external threaded portion 27, and tightened, so that a back plate 32 rests against an outer surface 1C of the housing 1. A nut portion 33 can then be used to further tighten the back nut 31 , using a wrench or the like. Tightening the back nut 31 urges the lugs 29 against the housing 1. The housing 1 is typically formed from polypropylene, so the lugs 29 become embedded within the housing 1, thereby preventing rotation, or free spinning, of the side connector 25. The gasket 30 also cooperates with the inner surface IB, to thereby provide a seal which prevents leakage of water from within the housing 1.

In use, a connecting pipe 34 can then be attached to the side connection using sealing nut 35 and copper olive 36, or the like as will be appreciated by persons skilled in the art.

In one example, the side connector pipe 26 is a 25mm diameter pipe, which can therefore provide free flow, eliminating balance and overflow problems. The side connector 25 also eliminates "freespinning", and hence leakage. It will be appreciated that the tighter the back nut 31 is tensioned the more the lugs 29 secure the side connector 25 and gasket 30 to the housing 1, thereby improving the sealing effect provided. Accordingly, the side connectors 25 form a strong seal, which in turn allows multiple manifolding without restriction to volume the flow volume.

It will be appreciated that the auto-fill device and the side connectors can advantageously be used in combination when it is desired to recirculate the water 5 A within the housing 1, for example to provide additional heating from multiple external heat sources. In this regard, the improved side connectors ensure that minimal leakage occurs, even with high recirculation volumes and hence high recirculation rates. Furthermore, a loss in water, for example as may occur during the external heating of the water 5 is automatically compensated for as a result of the action of the auto-fill device.

It will be appreciated that this allows heat exchangers, such as the Rotex Sanicube™, to maximise the degree of additional external heating that may be achieved. As any number of side connectors can be provided this allows heat from multiple sources, such as solar collectors, or waste heat from air conditioning units, to be collected via independent circuits, thereby maximising the efficiency of operation of the unit. An example of a further use of the side connectors is to allow a number of heat exchangers to be interconnected, in series, or in parallel, to allow additional heat storage capabilities to be provided. A first example of this will now be described with reference to Figure 4A.

In particular as shown in Figure 4A, two Rotex™ type heat exchange devices 4OA, 4OB are provided each having two side connectors 25A, 25B, and an inlet 4A and an outlet 4B, connected to a pipe 4 to provide a hot water supply, as shown. It will be appreciated that in this example, the heat exchangers 4OA, 4OB are therefore similar to those shown in Figure 1, and will not therefore be described in any further detail.

In any event, in use, the heat exchangers 4OA, 4OB, are connected to a heat source 41, having an inlet 42 A and an outlet 42B. The heat source could be any suitable heat source, but in this example is a boiler, such as a Rinnai HD200 boiler.

The boiler outlet 42B is coupled, via a pipe 43, to the side connectors 25A of the heat exchangers 4OA, 4OB, with the side connectors 25B being connected to the inlet 42A, via a pipe 44 and a flow controller 45. Additionally a water inlet pipe 46 is coupled to the inlets 4A, with a hot water outlet pipe 47 being coupled to the outlets 4B as shown.

In use, hot water from the boiler 41 is supplied to the heat exchangers 4OA, 4OB, via the side connectors 25A. This water is recirculated through the cavity 5 and returned via the side connectors 25B, the pipe 44 and the flow controller 45 to the inlet 42 A of the boiler 41. Thus, it will be appreciated from this that the boiler 41 operates to allow the water 5 A within the heat exchangers to be heated in use.

This in turn ensures that the water 5A within the heat exchangers is sufficiently hot to provide heating of water within the heat exchange pipe 4. This, in turn allows supplied via the inlet pipe 46 to be heated within the heat exchangers 4OA, 4OB, before being provided via the outlet pipe 47.

Hot water from the boiler 41 is supplied to the side connectors 25 A, which are located substantially towards the top of the heat exchangers 40. As the water 5A cools, convection within the heat exchanger cavity 5 will cause the cooler water to move towards the bottom of the cavity 5, thereby allowing it to be extracted via the lower side connectors 25B, for reheating. It will therefore be appreciated that it is preferable for the side connectors 25A to be used as inlet s, with the side connectors 25B being used as outlets. This helps to ensure maximal heating with water with the pipe 4.

In this example, the heat exchangers 4OA, 4OB are coupled to the heat source 41 in parallel so that each of the heat exchangers 4OA, 4OB will be provided with water directly from the boiler 41, which helps ensure each heat exchanger 40 is provided with a similar degree of heating.

However, it is also possible for the heat exchangers to be connected in series, with for example, the side connector 25B of the heat exchanger 4OA being coupled to the side connector 25 A of the heat exchanger 4OB. This may be desirable, for example, when there are restrictions on space for the pipes 43, 44.

Similarly, the outlets 4B are coupled to the outlet pipe 47 in parallel, and again this ensures that the hot water supplied via the outlet pipe 47 is provided equally from the heat exchangers 4OA, 4OB.

It will therefore be appreciated that this provides a mechanism to allow a number of heat exchangers to be interconnected to provide for additional heat storage capacity.

A second example of this is shown in Figure 4B. In particular, in this example two boilers 41 A, 41B are provided thereby allowing an additional degree of heating to be provided to the heat exchangers 41A, 41B. Operation will be substantially as described above.

A further example is shown in Figure 4C. In this particular example, four heat exchangers 4OA, 4OB, 40C, 4OD are provided, together with three boilers 41 A, 41B , 41C as shown. In this particular instance the connections are substantially as described above with respect to Figure 4B and these will therefore not be described in any further details.

However, in addition to the connections described above, a further side connection 25C is provided in each heat exchanger, m this instance the side connections 25C are interconnected via a pipe 48 so that each of the heat exchangers 4OA ... 4OD are interconnected as shown. The pipe 48 operates as a balance line, to help ensure that the volume of water 5A in each heat exchanger 4OA, ... 4OD is substantially equal. This helps reduce the chance of any of the heat exchangers overflowing, or running out of water 5A, should there be an uneven inflow or outflow of water through the side connectors 25 A, 25B. In this regard, it will be noted that the side connectors 25 C are provided in the lower half of the housing of the heat exchangers 40. The height difference between the side connector 25C and the normal water level inside the heat exchanger ensures that there is sufficient pressure within the pipe 48 to allow water to flow into a heat exchanger which has a low water level.

An example of a heat storage element for use in a heat exchanger will now be described with reference to Figure 5.

As shown, the element 51 includes a housing formed from a generally cylindrical tube 52, having two end caps 53, so as to define an element cavity 54. In use, the element cavity 54 is filled with a phase change material 55, typically leaving an air gap 54A at one end of the element cavity 54, as shown.

In use, a number of elements can be arranged internally within a heat exchanger to provide improved heat storage capabilities. In particular, when the phase change material is heated to above its melting point, it retains the energy required to melt the material as latent heat, with this energy being subsequently released as the material cools and solidifies.

Accordingly, the particular phase change material used within the element 51 can be selected based on the temperature at which the water is to be stored, so that the material will undergo a phase change at approximately the desired storage temperature.

Examples, of suitable phase change materials include hydrated salts, such as calcium chloride dihydrate, calcium chloride hexahydrate, sodium phosphate heptahydrate, sodium phosphate dodecahydrate, sodium acetate trihydrate, and magnesium nitrate hexahydrate, each of which have a respective melting point.

In Australia for example, regulations require that domestic hot water is stored at 620C. Accordingly, a suitable phase change material would be one that undergoes a phase change at 580C, such as sodium acetate trihydrate.

It will be appreciated that materials of this form can store a large amount of energy as latent heat, and as a result tend to be able to store up to thirteen times more energy than water over a suitable operating range, thereby leading to a vast increase in heat storage capabilities for a device such as the Rotex Sanicube. It is important to ensure that the heat storage elements can be relied upon to operate for a significant amount of time to thereby reduce maintenance costs. It is also preferable to ensure that the material, and the seal with the end caps, will be unaffected by immersion in temperatures encountered in hot water supply systems, otherwise contamination may occur, hi particular, water may enter the element and contaminate the phase change material, thereby rendering it ineffective, as well as causing phase change material to contaminate water in the housing 1, which in turn can damage the heat exchanger.

Accordingly, the tube 52 and end caps 53 are typically formed from a suitably resilient material, such as a thermoplastic, such as a polyolefme, which is both inert with respect to the phase change material and which demonstrates good heat and water resistant properties. Thus, the housing can be formed from polyethylene, polypropylene or the like.

The use of a suitable thermosetting plastic allows the seal between the end caps 53 and tube 52 to be achieved using a heat seal, hi this process, one of the end caps 53 and a corresponding end of the tube 52 are heated to approximately 2000C using a metal plate to melt the plastic. The end cap 53 and tube 52 are then urged together to form a seal.

This helps ensure that the join between the end caps 53 and the tube 52 remains water tight, and does not degrade as could occur if adhesive is used, for example.

In constructing the elements 51, the process used, is generally to form seal one of the end caps 53 to the tube 52. The phase change material is heated to cause it to melt, allowing it to be poured into the open end of the tube. Even when melted the phase change material can be relatively viscous. Accordingly, when filling the tube 52, it is preferable to pour the material in slowly in a number of stages, thereby allowing bubbles formed during the pouring process to dissipate. This avoids the presence of air cavities within the phase change material, which can cause problems as the element is repeatedly heated by repeatedly expanding and stressing the material 55 and the housing.

Once the phase change material has been provided in the element cavity 54, the element is allowed to cool so the material solidifies, before the second end cap 53 is attached to the tube 52, thereby sealing the phase change material in the element cavity. During the filling process, it is also important to ensure that the material does not become wet, which can also lead to diminished effectiveness.

Once completed, as mentioned above, a number of elements can be arranged within a heat exchanger, or other hot water storage system, to thereby improve the efficiency thereof.

Ail example of this is shown in Figure 6, in which seven elements 51, are arranged in the cavity 5 of a Rotex Sanicube. In order to ensure suitable mounting, the elements 51 are generally constructed to be between 1200mm and 1300 in length, with a diameter of approximately 75mm. This allows the arrangement shown to be used, which in turn allows the elements to be held in place using a relatively weak restraining force. This allows cable ties to be used to position and hold the elements in place. Thus, elements can easily be retrofitted to existing systems, as well as allowing elements to be easily removed for maintenance.

It will be noted that a number of additional benefits of the described arrangement when compared, for example to spherical packaging which is often used for phase change materials. Firstly, a spherical arrangement is difficult to install and fix in position within the hot water storage vessel. Secondly, the spherical arrangement is difficult to pack, thereby reducing the volume of material that can be incorporated into the hot water storage system. Thirdly, the spherical housing is generally difficult to seal, leading to leaks and hence damage to the hot water storage system.

A further issue is the relative surface area to volume ratio. In particular, the use of multiple small spheres as opposed to a single larger heat storage element results in an overall greater surface area to volume, which leads to rapid heat transfer between the phase change material and the water in the storage vessel. As a result, the use of small spheres of phase change material tends to lead to rapid dispersion of the stored heat, thereby reducing the benefits provided, hi contrast the use of the described elements can provide heating over a far longer duration, thereby reducing the frequency at which external heating is required. This in turn allows the hot water storage system to remain at the required operating temperature for a long duration, such that external heating, for example through the use of the electric heating element, is only required once a day. As a result, the heat storage system can be operated solely using cheap overnight electricity, or solar power, thereby vastly reducing operating costs. It will be appreciated that a number of different arrangements could be used. For example, elements 51 could be positioned between the housing 1 and the heat exchanger 4 in the corners of the housing. Additionally, elements can be clustered in the centre of the housing 1, as shown in Figure 6, or leaving an aperture in the centre, as shown in Figure 7, to allow an electric heating element 3 to be positioned as shown.

It will be appreciated that the larger the number of elements 51 used, the greater the increase in heat storage achievable. This allows heat exchangers, such as the Rotex Sanicube™, to maximise the degree of heat storage that may be achieved, thereby maximising the efficiency of operation of the unit.

Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art should be considered to fall within the spirit and scope that the invention broadly appearing before described.