AU2006203413A1

AU2006203413A1 - A heat sink and a heat exchanger

Info

Publication number: AU2006203413A1
Application number: AU2006203413A
Authority: AU
Inventors: Marko Pintar; Jing Jing Zheng
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-10-17
Filing date: 2006-08-08
Publication date: 2007-05-03
Anticipated expiration: 2026-08-08
Also published as: AU2006203413B2

Description

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AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION STANDARD PATENT A HEATSINK AND A HEAT EXCHANGER The following statement is a full description of this invention including the best method of performing it known to me: A HEATSINK AND A HEAT EXCHANGER FIELD OF THE INVENTION The present invention generally relates to hot water systems. The present invention has particular, although not exclusive application to solar hot water systems.

BACKGROUND TO THE INVENTION f Overheating is a problem in hot water systems, and occurs when hot water is heated above an acceptable limit which can result in equipment damage. Solar hot water systems have become more popular when compared with traditional gas and electric hot water systems over recent years as consumers develop a greater environmental consciousness.

Commonly, solar hot water systems are of an active type in which water is pumped between a solar collector and a storage tank in a closed-loop system. In this way, cooler water is circulated from the storage tank and through the solar collector where the water is heated before being returned to the storage tank. On hot days, the water temperature can be heated by the collector in excess of boiling point which has the potential to damage elements in the hot water system, such as the solar collector, if the water temperature is not regulated correctly.

In an attempt to address this problem, over-temperature regulators are incorporated into solar hot water systems for regulating the maximum temperature of the hot water. These regulators typically comprise a thermostat for monitoring the water temperature and a control system for regulating the water temperature once it exceeds a threshold. Some control systems retard the overheating of the hot water system by increasing the rate of flow of the water in the system. Such systems cannot operate in the event of disruption to the power source or if the system pump breaks down. Other control systems dump hot water from the system and replace it with cold water from a secondary source. The dumping of hot water from the system is wasteful.

C An example of an over-temperature regulator for a solar collector is described in GB

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C 2 047 878. The regulator comprises a thermal sensor for sensing the water

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tb temperature within the collector, a radiator located externally to the solar collector, S and a thermally actuated valve which is opened and places the collector in fluid OO communication with the radiator when the water temperature exceeds a predetermined threshold. In use, hot water passes through the open valve and into the radiator where heat is dissipated from the water and thereby regulates the water temperature.

It is an object of the present invention to provide an alternative means for retarding C overheating of heated water in a hot water system.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a heatsink for retarding overheating of heated water, the heatsink including: a body defining a chamber for containing a fluid, the body including lower and upper portions through which the chamber extends so that fluid can move from the lower portion to the upper portion when the lower portion is thermally coupled to the heated water and the upper portion is thermally coupled to a cooler medium, heat thereby being transferred from the heated water to the cooler medium via the fluid.

According to a further aspect of the present invention, there is provided a heat exchanger for retarding overheating of heated water, the heat exchanger including: a vessel into which heated water or water to be heated can be provided; and a heatsink fast with respect to the vessel and for thermally coupling to heated water, the heatsink including a body defining a chamber for containing a fluid, the body including lower and upper portions through which the chamber extends so that fluid can move from the lower portion to the upper portion when the lower portion is thermally coupled to the heated water and the upper portion is thermally coupled to a cooler medium, heat thereby being transferred from the heated water to the cooler medium via the fluid.

According to another aspect of the present invention, there is provided a heatsink for retarding overheating of water which is being heated, the heatsink including: I a body defining a chamber containing a fluid; the body including first and

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C second portions through which the chamber extends so that fluid can move from the first portion to the second portion; the fluid and internal pressure of the chamber being selected so as to enable movement of the fluid from the first portion to the oo second portion when: the body is located so that the first portion is thermally coupled to the water and the second portion is thermally coupled to a medium which is cooler than the water, the second portion is located above the first portion, and fluid in the first portion is heated above a threshold temperature; whereby heat can be transferred from the water to fluid located in first portion, whereafter at least some of the fluid can move from the first portion to the second 0 portion when fluid in the first portion is heated above the threshold temperature, and heat can be transferred from fluid located in the second portion to the medium, thereby retarding overheating of the water.

The present invention provides a passive technique for retarding overheating of the heated water by transferring heat from the heated water to the cooler medium. The heatsink has no active components and therefore does not require a power supply.

Preferably, the body further includes: one or more intermediate portions located between the first and second portions, the intermediate portions having lower thermal conductivity than the first and second portions. Even more preferably, the intermediate portions are interconnection portions which interconnect the first and second portions to provide fluid communication between the first and second portions. Even more preferably, the body comprises two interconnection portions on opposing sides of the body.

In this embodiment, as the water is heated, the first portion and fluid located in the first portion are also heated, and the intermediate portions act as a thermal break and thereby retard heat being transferred from the first portion to the second portion by conduction through the intermediate portions. The heatsink does not significantly cool sink heat from) the water being heated when the fluid is below the threshold temperature. When the fluid is heated above the threshold temperature, heat is transferred from the water to fluid located in the first portion, whereafter at least some of the fluid moves from the first portion to the second portion, and heat is transferred from fluid located in the second portion to the cooler medium, thereby retarding

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C overheating of the heated water. Hence, the heatsink sinks heat from the heated

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water when the temperature of the fluid (and the water) exceeds the threshold temperature and does not substantially sink heat from the water when the 0 temperature of the fluid (and the water) is below the threshold temperature.

Preferably, the internal pressure of the chamber and the type of fluid are selected such that the fluid is in a liquid state before being heated and will boil when heated above the threshold temperature. That is, the threshold temperature corresponds to Sthe boiling point of the fluid at that pressure. In use, heat is transferred from the 0 heated water to the liquid in the first portion (via the first portion) and the liquid is heated to its boiling point. Some of the liquid consequently changes into a gaseous state, thereby absorbing latent heat, and moves into the second portion where some of the gas contacts the second portion and transfers heat to the cooler medium (via the second portion). Typically, some of the gas will condense to liquid as it cools in the second portion and thereby releases latent heat.

In one embodiment, the fluid is water and the internal pressure in the chamber is below atmospheric pressure before use. Even more preferably, the internal pressure Sof the chamber and the type of fluid are selected such that the fluid boils at between to 90 0 C. Even more preferably, the fluid boils at about 75 0

C.

Preferably, the first portion, second portion and intermediate portions form a closedloop structure containing the fluid. Even more preferably, the closed-loop structure is tubular. Even more preferably, the first portion comprises an elongate portion which is substantially horizontal in use, for containing the fluid in a liquid state. Even more preferably, the second portion is located relative to the first portion so that, in use, condensed fluid in the second portion returns to the first portion under the force of gravity.

Even more preferably, the body includes two opposing side portions with one side being of greater length than the other side to define a return path for fluid.

Preferably, the chamber is sealed with the fluid inside.

C Preferably, the heatsink is used for retarding overheating of hot water in a hot water N system, the heated water being the hot water and the cooler medium being air. Most preferably, the hot water system is a solar hot water system.

00 According to a further aspect of the present invention, there is provided a heat exchanger for retarding overheating of heated water, the heat exchanger including: a vessel into which heated water or water to be heated can be provided; and a heatsink for thermally coupling to heated water; the heatsink including a S body defining a chamber containing a fluid; the body including first and second 0 portions through which the chamber extends so that fluid can move from the first portion to the second portion; the fluid and internal pressure of the chamber being selected so as to enable movement of the fluid from the first portion to the second portion when: the body is located so that the first portion is thermally coupled to the heated water and the second portion is thermally coupled to a medium which is cooler than the heated water, the second portion is located above the first portion, and fluid in the first portion is heated above a threshold temperature; whereby heat can be transferred from the heated water to fluid located in first portion, whereafter at least some of the fluid can move from the first portion to the second portion when fluid in the first portion is heated above the threshold temperature, and heat can be transferred from fluid located in the second portion to the medium, thereby retarding overheating of the heated water.

Preferably, the heat exchanger is provided in a hot water system, with a first medium being the hot water and the cooler medium being air. This embodiment of the invention provides a passive technique for retarding overheating of hot water in a hot water system. That is, there is no need for active parts such as valves, sensors, thermostats, solenoids, pumps and other like control system equipment which is used in conventional over-temperature regulators. The operation of the heat exchanger is unaffected by electrical power or hot water system pump failures, and does not require periodic maintenance.

Preferably, the vessel comprises: a tube; and two opposing walls at either end of the tube through which the body extends, the first portion being located between the two walls inside the vessel) and being immersed in the hot water in the vessel when in use.

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Z Preferably, the first portion is located in an upper portion of the vessel as the water temperature in the upper portion of the vessel is generally of a higher temperature in use.

S In one embodiment, the vessel is connected in fluid communication with the hot water system at a separate location to the solar collector. Even more preferably, the p vessel is a manifold for being connected in the fluid path of water circulating in the hot water system.

In an embodiment, the water is heated within the vessel by one or more heating elements. Even more preferably, each heating element is powered by one or more photo-voltaic cells. Even more preferably, the first portion is located proximal to the heating elements where the water is of higher temperature.

In another embodiment, the vessel is a water storage tank which is located distal to the solar collector.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described in relation to the accompanying drawings, wherein: Figure 1 is a schematic diagram showing a solar hot water system installed in a house; Figure 2 is a schematic diagram showing a solar collector comprising photo-voltaic cells and for use in a solar hot water system; Figure 3 is a side view showing a heat exchanger which includes a heatsink according to a first embodiment of the present invention; o Figure 4 is a graph of water temperature versus time for a first example of the 0 C heatsink of the first embodiment; tb3 Figure 5 is a graph of water temperature versus time for the first and further 00oo examples of the heatsink of the first embodiment; and C Figure 6 is a cross-sectional view showing a heatsink according to a second S embodiment of the present invention.

(Ni \O DESCRIPTION OF PREFERRED EMBODIMENTS C Figure la shows a solar hot water system 10 that is installed in a house 20. The hot water system 10 comprises: a flat-plate solar collector 12a for heating water; a storage tank 14 for storing the heated water; pipes 18 through which the water is circulated around the hot water system 10 (in a clockwise direction); and a pump 16 for pumping the water from the storage tank 14 to the solar collector 12a and visa versa. In use, cooler water is pumped from the bottom of the storage tank 14, using the pump 16 and via an uptake pipe 18, and through the solar collector 12a mounted on the roof of the house 20. The water is then heated within the collector 12a before being returned to the top of the storage tank 14 via a down-pipe 18.

Flat-plate solar collectors 12a typically comprise a winding pipe 18 within a glass faced box. An alternative type of solar collector 12b is shown in figure 2 which can be used in the hot water system 10. The solar collector 12b comprises: a heating tank 22 into which the water is provided; a bank of photo-voltaic cells 24 for collecting sunlight; and a number of heating elements 26 which are electrically connected to the photo-voltaic cells 24.

In use, each heating element 26 is powered by one or more photo-voltaic cells 24 which, in turn, heat the water passing through the heating tank 22.

According to a first embodiment of the present invention, there is provided a heat exchanger 32 shown in figure 3 for retarding overheating of hot water first medium) in the hot water system 10. The heat exchanger 32 comprises a manifold 34 for being connected in and maintaining the fluid path of water 40 circulating in the IND hot water system 10, and a heatsink 30 for contacting and transferring heat from the 0 C hot water 40 to air 54 second medium). The manifold 34 can be interconnected

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in fluid communication with a pipe 18 in the hot water system 10, at a separate location to the solar collector 12. The manifold 34 is preferably installed down stream from the solar collector (at point A shown in Fig. between the outlet of the solar collector 12 and the inlet of the storage tank 14, where the water 40 is generally of a higher temperature.

The manifold 34 comprises a tube 46 having two opposing walls 48 at either end of S the tube 46. In use, hot water 40 flows from the solar collector 12 through an inlet 42 in a wall 48 and into the tube 46. The tube 46 fills with hot water 40 which, in turn, flows out of an outlet 44 in an opposing wall 48 and into the storage tank 14. A layer of insulation material 35 can surround the manifold 34 for containing heat therein, as it is desirable to minimise heat loss from the manifold 34.

The heatsink 30 comprises a body 31 which defines a chamber 33 containing heat transfer fluid 50. In use, the heat exchanger 32 is disposed in the orientation shown in figure 3 and the body 31 thereby has a lower first) portion 36 and an upper second) portion 38. The body 31 also comprises two intermediate portions 52 which are located between the lower and upper portions 36, 38. The lower and upper portions 36, 38 are formed from tubular metal having a relatively high thermal conductivity copper or brass) whereas the intermediate portions 52 are formed from tubular material having a relatively low thermal conductivity plastic or polymer).

The intermediate portions 52 are interconnection portions which serve to interconnect the lower and upper portions 36, 38 together. The chamber 33 extends through the lower, upper and intermediate portions 36, 38, 52 so that fluid 50 can move from the lower portion 36 to the upper portion 38. The two intermediate portions 52 are located on opposing sides 60 of the body 31.

The heatsink 30 is attached to the manifold 34 whereby the lower portion 36 of the heatsink 30 extends through the tube 46 of the manifold 34 and is located between the two walls 48 inside the manifold 34). The lower portion 36 is immersed in and surrounded by the hot water 40 in the tube 46 when in use. It is preferable that the lower portion 36 is located in an upper portion of the manifold 34, as the water b temperature in the upper portion of the manifold 34 is generally of a higher temperature than the water temperature in a lower portion of the manifold 34.

00 The body 31 of the heatsink 30 contains the heat transfer fluid 50 within the chamber 33. The fluid 50 is typically sealed within the chamber 33 during manufacturing and S prior to the sale of the heat exchanger 32, although, could alternatively be introduced C into the heat exchanger after sale and replaced as necessary. The fluid 50 in the

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present embodiment is water and the internal pressure in the chamber 33 is below C atmospheric pressure under a partial vacuum) before use. The internal pressure of the chamber 33 is about 38kPa absolute which causes the water in the chamber to boil at about 75°C. Under these conditions, the fluid 50 water) is in a liquid state when below its threshold temperature prior to use.

The lower portion 36, upper portion 38 and intermediate portions 52 form a tubular closed-loop structure containing the fluid 50. Prior to use, the liquid 50a accumulates on (and covers) the floor of the lower portion 36 in the elongate and substantially horizontal section extending between the two walls 48 of the manifold 34. The liquid is filled to a level such that there is gas communication around the complete closed-loop structure. That is, the liquid 50a covers the floor of the lower portion 36 but does not touch the ceiling of the substantially horizontal section of the lower portion 36.

The body 31 has two opposing sides 60 which are substantially vertical in use. A first side portion 60a is of a first length and a second side portion 60b is of a second length which is greater than the first length. The upper portion 38 comprises an elongate portion which extends between the two sides 60 and has a floor 58 which is tilted with respect to the horizontal section of the lower portion 36 to thereby define a return path for gas 50b that condenses to liquid 50a. The heatsink 30 further comprises a plurality of fins 56 which extend from the upper portion 38 of the body 31 and into the air 54. The fins 56 are integrally formed with the upper portion 38 and serve to increase the surface area of contact between the upper portion 38 and the air 54 to thereby facilitate with heat transfer.

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The operation of the heat exchanger 32 in the hot water system 10 will now be described when in use. As the hot water 40 in the manifold 34 is heated (upstream) by the solar collector 12, the lower portion 36 of the heatsink 30 and the liquid 00 located in the lower portion 36 are also heated. The intermediate portions 52 act as a thermal break and thereby retard heat from being transferred from the lower portion 36 to the upper portion 38 by conduction through the intermediate portions 52. The heatsink 30 does not significantly cool sink heat from) the hot water 40 until the 7 liquid 50a is heated above a threshold temperature. The threshold temperature of the S fluid 50 for the present embodiment corresponds to the boiling of the fluid 50 when the fluid 50 changes from a liquid state 50a to a gaseous state 50b and evaporation occurs.

The internal pressure of the chamber 33 and the type of fluid water) are selected so as to yield a desirable threshold temperature. In the present embodiment, the internal pressure of the chamber 33 was selected to be about 38kPa absolute which causes the water fluid 50) in the chamber 33 to boil at about 75 0 C. The internal pressure P of the chamber 33 can be estimated using the well established ideal gas law: P= nRT

V

where: n is a ratio of the mass of the fluid 50 in the chamber 33 to the molecular weight of the fluid R is a gas e. fluid) constant; T is the threshold temperature of the fluid 50; and V is the internal volume of the chamber 33.

For the present embodiment, the fluid 50 being used is water and the relationship between the internal pressure of the chamber 33 and the threshold boiling) temperature of the fluid 50 is well known by those in the art. That is, it is well known that water which is pressurised to about 38kPa absolute will boil at about 75 0

C

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S As the temperature of the hot water 40 increases beyond the threshold temperature,

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tb3 heat is transferred from the hot water 40 to the liquid 50a in the lower portion 36 via the lower portion 36. This heat transfer causes the liquid 50a to be heated to its oo boiling point which, in turn, causes some of the liquid 50a to change into a gaseous state 50b and evaporate. The gas 50b then moves up and into the upper portion 38, which is at a cooler temperature and thereby results in some of the gas condensing on the inner wall of the upper portion 38. The gas 50b therefore returns to a liquid state 50a as heat is transferred from the fluid 50 to the air 54 via the upper portion 38.

Hence, the heatsink 30 sinks heat from the hot water 40 when the water temperature exceeds the threshold temperature of 75 0 C, and does not does not substantially sink heat from the hot water 40 when the water temperature is below the threshold temperature. A fan can be provided for circulating air 54 over the fins 56 to thereby increase the rate of heat transfer (by forced convection) between the fluid 50 in the upper portion 38 and the air 54. As the size or number of fins are increased, the surface area of the upper portion 38 contacting the air 54 also increases which, in turn, results in a greater the rate of heat transfer between the fluid 50 in the upper portion 38 and the air 54.

The sides 60 of the body 31 are substantially vertical with one side 60b being of greater length than the other side 60a and thereby defining a return path for condensed fluid 50a in the upper portion 38. The fluid 50 evaporates into a gaseous state 50b in the lower portion 36 and passes into the cooler upper portion 38 (via the side portions 60) where it condenses. As the fluid 50 condenses back into a liquid state 50a, the condensed liquid 50a forms on the inner wall of the upper portion 38 and trickles to the tilted floor 58 of the upper portion 38. The liquid 50a then runs along the tilted floor 58 before draining down the first side portion 60a and back into the lower portion 36 under the force of gravity.

A first example which demonstrates the operation of the heatsink 30 of the first embodiment will now be described. The results of the first example is shown in the graph of Figure 4.

Initially, there was provided an open vessel containing water and having a heating Selement submerged in the water. The ambient temperature of the water and air was about 16 0 C. The heating element was activated so as to dissipate a power of 400W i in the water. The change in water temperature was measured over time and is shown as a substantially linear reference characteristic 80 in Figure 4.

S Subsequently, the water was allowed to cool to the ambient air temperature of about 160C. The heatsink 30 was immersed in the water such that the horizontal section of the lower portion 36 of the heatsink 30 was completely surrounded by the water. As S previously described, the fluid 50 and internal pressure of the chamber 33 was selected so as to give a threshold temperature of the fluid of about 750C. Once again, the heating element was activated so as to dissipate a power of 400W in the water.

The change in water temperature was measured over time and is shown as a nonlinear test characteristic 90 in Figure 4.

Figure 4 shows that the reference and test characteristics water temperatures) 90 were coincident until the water temperature exceeded the threshold temperature of about 750C at about 22 minutes. That is, the heatsink 30 did not substantially sink heat from the hot water when the temperature of the fluid 50 (and therefore the hot water) was below the threshold temperature of 750C. Beyond 22 minutes, the temperature of the fluid 50 exceeded the threshold temperature, and the heatsink 30 began to sink heat from the water which caused the rate of increase in water temperature to decline and then stabilise at about 30 minutes.

The temperature of the hot water then remained at about 800C until the test was halted at 40 minutes. Immediately prior to halting the test, an equilibrium was established whereby the rate of evaporation and condensation of the fluid 50 in the chamber 33 had equalised become the same), thus stabilising the hot water temperature and thereby retarding overheating of the hot water 40 and the system.

At this equilibrium point, the power dissipated in the water by the heating elements was comparable to the power being dissipated by the heatsink S Figure 5 shows the test characteristic of the first example 400W) and shows C further test characteristics when the same test was performed by dissipating 800W N 92 and 1000W 94 into the water through the heating elements. For each test characteristic 90,92,94, it is apparent that the heatsink 30 sinks heat from the hot 0 water when the temperature of the fluid 50 exceeds the threshold temperature of 750C and does not substantially sink heat from the hot water when the temperature t of the fluid 50 is below the threshold temperature of 750C. Accordingly, the temperature of the hot water for each test characteristic 90,92,94 stabilised at about minutes: the 400W test characteristic 90 stabilising at about 800C; the 800W test \O characteristic 90 stabilising at about 1000C and the 1000W test characteristic C stabilising at about 1100C.

The internal pressure of the chamber 33 and the type of fluid 50 was selected so as to boil at about 750C at the threshold temperature), although, will typically be selected such that the fluid 50 boils at between 60 to 900C. In practice, this threshold temperature is selected to be high enough such that a significant amount of heat is not sunk from the hot water 40 when the hot water is below the threshold temperature (and at normal operating temperature), and low enough such that the temperature of the hot water 40 will stabilise saturate) at a temperature below the point at which overheating of both the hot water 40 and the hot water system will occur. Hence, a compromise may be required when selecting the threshold temperature.

According to a second embodiment of the present invention, there is provided a heatsink 30 as shown in figure 6. The body 31 of the heatsink 30 is integrally formed from metal. The body 31 defines a chamber 33 which contains heat transfer fluid The body 31 comprises lower and upper portions 36, 38 through which the chamber 33 extends so that fluid 50 can move from the lower portion 36 to the upper portion 38. The fluid 50 and internal pressure of the chamber 33 are selected so as enable movement of the fluid 50 from the lower portion 36 to the upper portion 38 when: the body 31 is located so that the lower portion 36 contacts hot water and the upper portion 38 contacts air which is cooler than the hot water; the upper portion 38 is located above the lower portion 36; and the fluid 50 in the lower portion 36 is heated above a threshold temperature.

In use, heat can be transferred from the hot water to fluid 50 located in the lower portion 36, whereafter at least some of the fluid 50 can move from the lower portion 36 to the upper portion 38 when fluid 50 in the lower portion 36 is heated above the Sthreshold temperature and heat can be transferred from fluid 50 located in the upper portion 38 to the air, thereby retarding overheating of the hot water.

The heatsink 30 of the present embodiment is relatively simpler in construction than that described in the first embodiment whereby intermediate portions 52 are not provided. In contrast to the operation of the heatsink 30 of the first embodiment, a greater amount of heat may be transferred from the first medium to the lower portion 36 and then, in turn, from the lower portion 36 to the upper portion 38 by conduction through the side walls of the body 31 when the temperature of the fluid 50 is below the threshold temperature. Consequently, this embodiment may be less suitable for use in hot water systems when it is desirable to minimise the sinking of heat from hot water prior to the threshold temperature of the fluid 50 being exceeded. However, as before, a tubular intermediate portion (not shown) may be provided between the upper portion 38 and lower portion 36 in other embodiments.

The upper portion 38 forms a ceiling of the chamber 33 having an inverted apex 62.

Condensed fluid 50 in the upper portion 38 can accumulate on the ceiling and run down to the point of the apex 62 where it can drip back into the lower portion 36. That is, the upper portion 38 is located relative to the lower portion 36 and defines a return path so that, in use, condensed fluid in the upper portion 38 returns to the lower portion 36.

Additional variations and embodiments of the present invention will be apparent to a person skilled in the art.

In the first embodiment, the chamber contained water and had an internal pressure of about 38kPa absolute before use. In other embodiments, the internal pressure in the chamber 33 and/or type of fluid 50 can be varied, before use, so as to yield a different threshold temperature.

ID According to the first embodiment, the manifold was connected in fluid 0 communication with the hot water system 10 at a separate downstream location to the solar collector 12. In another embodiment, the water 40 can be heated within an ;Z alternative type of vessel forming part of a solar collector 12b and the heatsink oo can be attached to that vessel. For example, the solar collector 12a may comprise a heating tank 22 inside which one or more heating elements 26 are provided for heating the water. Each heating element can be powered by one or more photovoltaic cells which form part of the solar collector 12b. Preferably, the heatsink 30 is attached to the vessel so that a lower portion of the heatsink 30 is located proximal to the heating elements 26 where the water is of higher temperature.

In one embodiment, the heating elements may be vacuum tube type solar collectors not including photo-voltaic cells).

In yet another embodiment, the heatsink could be attached to a water storage tank 14 which is located distal to the solar collector 12.

According to the first embodiment, the manifold was connected in a hot water system where the water first medium) to be used was circulated between the solar collector 12 and the storage tank 14. In an alternative embodiment, the first medium could be an alternative fluid having anti-freeze properties, which is circulated between the solar collector 12 and the storage tank 14 in a closed loop system. In this manner, the circulating fluid can be heated in the solar collector 12 and pass through a heat exchanger located in the storage tank 14, where heat is then transferred from the circulating fluid to the water to be used, which is in the storage tank 14.

In yet another embodiment, the second medium could be a fluid which is in contact with the upper portion 38.

The fluid level of the first embodiment was selected so as to cover the floor, whilst not contacting the ceiling, of the first portion 36 of the heatsink 30 before heating.

The fluid level can be varied so as to provide differing heatsinking properties of the heatsink 30. For example, if the body 31 is initially filled with an inadequate amount O of liquid 50a, such that the liquid 50a barely covers the floor of the lower portion 36, 0 C the heatsink 30 may function at a reduced level of performance owing to insufficient

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t evaporation of the liquid 50a. Filling the body 31 with liquid 50a such that there is no gas communication around the entire closed-loop may inhibit the speed of movement oO of the evaporated fluid 50b from the lower portion 36 to the upper portion 38. If the liquid 50a fills the lower portion 36 and intermediate portions 52, and contacts the t' upper portion 38, heat can be transferred by conduction from the lower portion 36 to the upper portion 38 via the liquid 50a which may undesirably result in the heatsink C 30 significantly cooling the hot water 40 when the water is below the threshold O temperature. The user should be mindful of these possibilities when initially filling the C body 31 with fluid The examples of the second embodiment demonstrated how the heatsink 30 could be used to retard overheating of water in which various amounts of power are being dissipated. If excessive power is dissipated in the water in excess of 1000 all of the fluid could potentially change into (and remain in a gaseous state), at which point the heat sinking effectiveness of the heatsink 30 may be reduced. Such undesirable effects could be countered by, for example, increasing the physical dimensions of the heatsink 30 so as to contain more fluid, increasing the number or size of the fins 56, providing for the forced convection of the second medium, or using more than one heats ink 30 in the system.

The heat exchanger 32 of the first embodiment comprised a heatsink 30 which was attached to a manifold 34. Accordingly to a further embodiment of the present invention, the heat exchanger has a manifold and a heatsink which are integrally formed together. In this manner, the lower portion of the heatsink and the tube of the manifold would share a common wall. In yet another embodiment, the heatsink may be thermally coupled to the outside of the manifold 34.

In the first embodiment, the sides 60a, 60b of the heatsink 34 were of different length so as to form a return path for condensed fluid. In another embodiment, the sides are of comparable length.

These and other modifications may be made without departing from the ambit of the invention, the nature of which is to be determined from the foregoing description.

S It is to be understood that, if any prior art publication is referred to herein, such 00 reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to C specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A heatsink for retarding overheating of heated water, the heatsink including: a body defining a chamber for containing a fluid, the body including lower and oo upper portions through which the chamber extends so that fluid can move from the lower portion to the upper portion when the lower portion is thermally coupled to the heated water and the upper portion is thermally coupled to a cooler medium, heat thereby being transferred from the heated water to the cooler medium via the fluid.

2. A heatsink as claimed in claim 1, wherein the body further includes: 110 0one or more intermediate portions located between the upper and lower portions, each intermediate portion having lower thermal conductivity than the upper and lower portions and providing fluid communication between the upper and lower portions.

3. A heatsink as claimed in claim 2, wherein the body includes two intermediate portions on opposing sides of the body.

4. A heatsink as claimed in any one or more of claims 2 or 3, wherein the lower portion, upper portion and intermediate portions form a tubular closed-loop structure containing the fluid.

A heatsink as claimed in any one or more of the preceding claims, wherein the lower portion includes an elongate portion which is substantially horizontal in use and collects the fluid in a liquid state.

6. A heatsink as claimed in any one or more of the preceding claims, wherein the upper portion is located relative to the first portion so that, in use, condensed fluid in the upper portion returns to the lower portion under the force of gravity.

7. A heatsink as claimed in claim 6, wherein the body includes two opposing sides with one side being of greater length than the other side to define the return path for the fluid. ID

8. A heatsink as claimed in any one or more of the preceding claims, wherein the 0 C chamber is permanently sealed with the fluid inside. (N S

9. A heatsink as claimed in any one or more of the preceding claims, wherein the oo heatsink is used for retarding overheating of hot water in a hot water system and the medium is air.

A heatsink as claimed in any one or more of the preceding claims, wherein the C upper portion includes a plurality of cooling fins. (N

11. A heatsink as claimed in any one or more of the preceding claims, wherein the internal pressure of the chamber and the type of fluid are selected such that the fluid is in a liquid state before being heated and will boil when heated above a threshold temperature.

12. A heatsink as claimed in claim 11, wherein the internal pressure of the chamber and the type of fluid are selected such that the threshold temperature is between to

13. A heat exchanger for retarding overheating of heated water, the heat exchanger including: a vessel into which heated water or water to be heated can be provided; and a heatsink fast with respect to the vessel and for thermally coupling to heated water, the heatsink including a body defining a chamber for containing a fluid, the body including lower and upper portions through which the chamber extends so that fluid can move from the lower portion to the upper portion when the lower portion is thermally coupled to the heated water and the upper portion is thermally coupled to a cooler medium, heat thereby being transferred from the heated water to the cooler medium via the fluid.

14. A heat exchanger as claimed in claim 13, wherein the vessel defines an inlet through which heated water from an upstream water heater can be provided and an outlet through which cooler water can exit the vessel. I

15. A heat exchanger as claimed in any one or more of claims 13 and 14, wherein 0 C the vessel includes a tube and two opposing walls at either end of the tube through which the body extends, the lower portion being located between the two walls and being immersed in the hot water in the vessel when in use. 00 oo

16. A heat exchanger as claimed in claim 15 wherein, in use, the lower portion is located in an upper portion of the vessel.

17. A heat exchanger as claimed in claim 13, further including a heater extending into the vessel and for heating the water to be heated within the vessel.

18. A heatsink for retarding overheating of water which is being heated, the heatsink including: a body defining a chamber containing a fluid; the body including first and second portions through which the chamber extends so that fluid can move from the first portion to the second portion; the fluid and internal pressure of the chamber being selected so as to enable movement of the fluid from the first portion to the second portion when: the body is located so that the first portion is thermally coupled to the water and the second portion is thermally coupled to a medium which is cooler than the water, the second portion is located above the first portion, and fluid in the first portion is heated above a threshold temperature; whereby heat can be transferred from the water to fluid located in first portion, whereafter at least some of the fluid can move from the first portion to the second portion when fluid in the first portion is heated above the threshold temperature, and heat can be transferred from fluid located in the second portion to the medium, thereby retarding overheating of the water.

19. A heat exchanger for retarding overheating of heated water, the heat exchanger including: a vessel into which heated water or water to be heated can be provided; and a heatsink for thermally coupling to heated water; the heatsink including a body defining a chamber containing a fluid; the body including first and second portions through which the chamber extends so that fluid can move from the first portion to the second portion; the fluid and internal pressure of the chamber being selected so as to enable movement of the fluid from the first portion to the second C portion when: the body is located so that the first portion is thermally coupled to the heated water and the second portion is thermally coupled to a medium which is cooler than the heated water, the second portion is located above the first portion, oO and fluid in the first portion is heated above a threshold temperature; whereby heat can be transferred from the heated water to fluid located in first C portion, whereafter at least some of the fluid can move from the first portion to the second portion when fluid in the first portion is heated above the threshold C temperature, and heat can be transferred from fluid located in the second portion to the medium, thereby retarding overheating of the heated water.

A heatsink substantially as herein described with reference to Figure 3.

21. A heat exchanger substantially as herein described with reference to Figure 3. Dated this 8' th day of August 2006 MARKO PINTAR AND JING JING ZHENG by our attorneys Eagar Buck Patent and Trade Mark Attorneys