GB2484539A

GB2484539A - Thermal energy store for use with a heating or cooling system

Info

Publication number: GB2484539A
Application number: GB1017471.2A
Authority: GB
Inventors: Thomas Lipinski
Original assignee: GREEN STRUCTURES Ltd
Current assignee: GREEN STRUCTURES Ltd
Priority date: 2010-10-15
Filing date: 2010-10-15
Publication date: 2012-04-18
Also published as: GB201017471D0

Abstract

The thermal store comprises a vessel 2 and a heat exchanger 10. The heat exchanger is mounted within the vessel and includes first and second fluid flow paths that are separate from one another. The vessel is adapted to receive a liquid phase change material and may include a lid 3 that forms a hermetic seal with the vessel. The heat exchanger may be removable from the vessel and comprise a plurality of laminar plates 11, wherein each plate includes a first and a second conduit on either side of the plate, the conduits being arranged in a spiral pattern and forming part of the first and second fluid flow paths. The plates may include connection elements 12 to interconnect the plates to form a modular heat exchanger. The heat exchanger may be submerged in the phase change material. The thermal store may be incorporated in a heating or cooling system, in which the first fluid flow path is used to charge the thermal store and the second fluid flow path to discharge the thermal store. A modular heat exchanger plate and method of installing a thermal energy store are also claimed.

Description

THERMAL STORE

This invention relates to a thermal store. In particular, it relates to a modular thermal store for receiving phase change material. Further, it relates to a heating or cooling system incorporating the thermal store. It also relates to a modular heat exchanger plate for a thermal store. The invention also relates to a method of installing and maintaining a thermal store.

Heating and cooling systems that use phase change materials (PCM) are known. A phase change material is one that is able to store relatively large amounts of energy as latent heat during a phase transition. The use of PCMs improve the thermal capacity of a heating or cooling system. A range of PCMs are available with different transition temperatures. For example, using a PCM having a transition temperature of around 50°C, heat could be stored during the day for use in space heating at night. Alternatively, using a PCM having a transition temperature of around 10°C, the PCM could be cooled at night, when the ambient temperature is lower, which can be used to provide cool air during the day. The use of PCM can substantially improve the efficiency of heating and cooling systems.

Known energy stores comprise large tanks that are typically buried underground. Many discrete containers that house the PCM are stacked inside the tanks. Air or other working fluid can then be flowed through the tank to "charge" the PCM and also to "discharge" the PCM.

Depending on the required use, "charging" the PCM may comprise heating the PCM and therefore "discharging" will involve removing the heat from the PCM for use in space heating or hot water, for example.

Alternatively, "charging" may involve cooling the PCM and therefore "discharging" will involve using the PCM to cool air or working fluid, for use in air conditioning, for example. The installation of such large tanks is cumbersome and expensive, especially when retrofitting. Further, maintenance of the system is problematic as the tank may need to be excavated. For instance, if the PCM has separated out of solution it is a major job to remove the containers from the tank.

According to a first aspect of the invention we provide a thermal energy store comprising a vessel and a heat exchanger mounted within the vessel, the vessel adapted to receive a liquid phase change material, wherein the heat exchanger includes a first fluid flow path and a second fluid flow path separate from the first fluid flow path.

This is advantageous as it provides a flexible arrangement for storing heat. As the thermal energy store includes two fluid flow paths it can charge the liquid PCM and discharge it at the same time, as well as exchange heat between the flow paths. Further, the use of a liquid PCM such as a eutectic salts solution ensures that the fluid flow paths are in contact with the PCM as it can flow around them. Thus, the system is particularly suited to retrofit applications where the vessel can be installed in dwelling and installed with relative ease.

Preferably the vessel includes a removable lid, which preferably makes a hermetic seal with the vessel. This is advantageous as the vessel can easily be filled with PCM and then the lid can seal the vessel.

Further, maintenance is simplified as the user need only remove the lid to service the PCM or the heat exchanger.

Preferably the heat exchanger is removable from the vessel. This makes the heat exchanger easily serviceably.

Preferably the heat exchanger comprises at least one heat exchanger plate, the plate including a first conduit that forms part of the first fluid flow path and a second, separate, conduit that forms part of the second fluid flow path. By having two distinct fluid flow paths through the thermal store, the system in which the thermal store is installed can operate more efficiently as the thermal store can be charged and discharged simultaneously.

Preferably the plate comprises a laminar member having the first conduit and the second conduit extending in the plane of the laminar member. This is advantageous as the first conduit and second conduit extend alongside one another, which makes the heat exchanger plates easy to assemble.

Preferably the first conduit is arranged in a substantially spiral pattern on the plate and/or the second conduit is arranged in a substantially spiral pattern on the plate. If both the conduits are arranged in a spiral pattern, the spirals may run between one another. Alternatively, the first conduit may be arranged to follow a substantially meandering path on one side of the plate and the second conduit may be arranged to follow a substantially meandering path on the opposed side of the plate.

Preferably the first conduit and/or the second conduit extend in the same plane as the plate and the width of the conduit is greater than the thickness of the plate such that the plate forms webs between parts of the conduit.

Preferably the heat exchanger comprises a plurality of heat exchanger plates, each heat exchanger plate including connection elements at each end of the first conduit and at each end of the second conduit, the connection elements arranged at predetermined locations such that the plates can be connected together to form a modular heat exchanger.

Preferably the plates are adapted to be connected together in series.

This is advantageous as a series of heat exchanger plates can be connected together to fill the vessel at increase the length of the first fluid flow path and second fluid flow path. Preferably the connection elements extend perpendicular to the plane of the plate. Alternatively, the heat exchanger could include a manifold adapted to connect the plates together in parallel.

Preferably the first and second conduits are arranged such that a first end of each conduit is located at the periphery of the plate and a second end of each conduit is located substantially at the centre of the plate and therefore the plates of the modular heat exchanger are connected together alternately at their peripheries and then at their centres. Alternatively, the first end and second end of the first conduit may be located adjacent an edge of the plate. The first end and second end of the second conduit may also be located adjacent an edge of the plate, which may be the same edge as the first end and second end of the first conduit.

Preferably the thermal energy store includes first and second supply ports and first and second return ports, the heat exchanger arranged such that the first fluid flow path connects the first supply port and first return port and the second fluid flow path connects the second supply port and second return port. This is advantageous as the thermal energy store provides an easy connection to a charge circuit and a discharge circuit.

According to a second aspect of the invention, we provide a heating or cooling system including the thermal energy store of the first aspect of the invention.

Preferably the first fluid flow path connects to a primary loop that is adapted to charge the thermal store. Preferably the second fluid flow path connects to a secondary loop that is adapted to discharge the thermal store. This is advantageous as the system can charge and discharge the thermal store at the same time, which improves its flexibility. Thus, the thermal store provides 3-way heat transfer; primary loop to secondary ioop through the each plate, primary ioop to PCM and PCM to secondary loop.

According to a third aspect of the invention, we provide a modular heat exchanger plate for use with the thermal energy store of the first aspect of the invention.

Preferably the heat exchanger plate includes a first conduit that forms a first fluid flow path and a second, separate, conduit that forms part of a second fluid flow path.

Preferably the plate comprises a laminar member having the first conduit and the second conduit extending in the plane of the laminar member. This is advantageous as the first conduit and second conduit extend alongside one another, which makes the heat exchanger plates easy to connect together.

Preferably the first conduit is arranged in a substantially spiral pattern on the plate and/or the second conduit is arranged in a substantially spiral pattern on the plate.

Preferably the modular heat exchanger plate forms part of a kit of parts comprising a second heat exchanger plate and two connection elements arranged to connect the first conduit of the first plate to the first conduit of the second plate and to connect the second conduit of the first plate to the second conduit of the second plate.

According to a fourth aspect of the invention we provide a method of installing a thermal energy store for a heating or cooling system, comprising the steps of; a) mounting a vessel in a desired location; b) inserting at least one heat exchanger plate into the vessel; c) at least partially liquid filling the vessel with phase change material to form the thermal store; and d) connecting the thermal store to the heating or cooling system.

The installation of the thermal store is straightforward as the relatively lightweight parts can be assembled and connected and then the vessel can be filled with PCM salts in solution. It will be appreciated that the steps do not have to be performed in that order.

Preferably step d) includes connecting a charging supply and return conduit to the thermal store and connecting a discharging supply and return to the thermal store.

Preferably step b) includes connecting a number of heat exchanger plates together to form a modular heat exchanger and inserting the connected plates into the vessel.

Preferably step c) includes at least partially liquid filling the vessel with eutectic salts solution. Thus, the eutectic salts solution will flow around the heat exchanger and into contact with the at least one heat exchanger plate.

Preferably step a) includes mounting a further vessel in the desired location and connecting the vessel and further vessel in parallel or series, and steps b) and c) are performed on both the vessel and further vessel.

There now follows by way of example only a detailed description of the present invention with reference to the accompanying drawings, in wh i ch; Figure 1 shows a first embodiment of a thermal store; Figure 2 shows a cross-section through the thermal store and the lid removed; Figure 3 shows a plan view of a modular heat exchanger plate; Figure 4 shows a plurality of modular heat exchanger plates connected together to form a modular heat exchanger; Figure 5 shows a flow chart illustrating a method of installing the thermal store; Figure 6a and 6b show a modification to the heat exchanger and heat exchanger plates; and Figures 7a and 7b show a second modification to the heat exchanger and heat exchanger plates.

Figure 1 shows a thermal store I comprising a vessel 2, closed by a lid 3. The vessel 2 and lid 3 are of plastics and are well insulated to minimise heat transfer. The lid 3 is adapted to form a hermetic seal with the vessel 2 to minimise evaporation from the vessel. The thermal store I of this embodiment is for use in a solar heating system.

However, it will be appreciated that the thermal store could be integrated into a hot water system, an air cooling systems or a space heating system or the like. The thermal store has utility in any system where heat or "cold" needs to be used at a different time to when it is created.

The vessel 2 includes a primary loop supply port 4 and a primary loop return port (not visible) on an opposite side of the vessel 2. The vessel 2 also includes a secondary loop supply port 6 and a secondary loop return port (not visible) on an opposite side of the vessel 2. The lid 3 also includes a filling port 8 that provides access to the interior of the vessel 3 for at least partially filling it with phase change material. In this embodiment the phase change material comprises a solution of eutectic salts. The eutectic salts are preferably sufficiently liquid that they can be poured into the vessel 2 through the filling port 8.

Figure 2 shows a section through the vessel 2. The same reference numbers have been used for the same parts. The lid 3 is shown spaced from the vessel 2. The vessel 2 also includes a drain 9 adjacent its base for removing liquid PCM from the vessel. The vessel 2 contains a heat exchanger 10 comprising a plurality of heat exchanger plates 11.

The fifteen heat exchanger plates 11 shown in this embodiment are connected together by connection elements 12. It will be appreciated that any number of heat exchanger plates could be used depending on the heat transfer required for a particular application. As the plates are modular, it is easy for the heat exchanger to be constructed of any number of plates. In use, the vessel 2 is adapted to be filled with phase change material, which is shown filled to the dashed line 13, such that it covers the heat exchanger 10 but is spaced from the rim 14 of the vessel 2 to allow for expansion.

The heat exchanger 10 is connected to the vessel by transfer conduits 16, 17, 18, 19. The transfer conduits extend into the walls of the vessel 2 and project from the rim 14. The transfer conduit 16 terminates with the primary loop supply port 4 and the transfer conduit 17 terminates in the primary loop return port 5. Similarly, the transfer conduit 18 terminates with the secondary loop supply port 6 and the transfer conduit 19 terminates with the secondary loop return port 7. It will be appreciated that the ports 4 and 5 are shown offset from the ports 6 and 7 for clarity and that they are actually directly behind the ports 6 and 7 in this view. The ports 4, 5, 6, 7 are arranged to project through a corresponding aperture 20 in the lid 3.

Figure 3 shows a single heat exchanger plate 11 in plan view. The plate 11 includes a first conduit 21 which forms a first fluid flow path and a second conduit 22 which forms a second fluid flow path separate from the first fluid flow path. The first and second conduits have a circular cross-section. The first conduit 21 follows a spiral path between the periphery 23 of the plate and substantially a centre 24 of the plate 11. The second conduit 22 also follows a spiral path between the periphery 23 and substantially the centre 24 but the spiral extends in the opposite direction. The spiral paths are intertwined such that one of the spiral paths extends between the spiral paths of the other. The plate 11 comprises a substantially rectangular laminar member 25. The laminar member 25 is thinner than the width of the conduits 21, 22.

Thus, the plate 11 can be considered to comprise the two conduits 21, 22 connected by webs therebetween. The plates 11 in this embodiment are of aluminium.

The first conduit 21 includes a connector at each end. The first connector 26 extends out of the page. The second connector 27, at the other end of the conduit 21, is located on the opposite side of the plate 11 and is therefore not visible, although it extends in the opposite direction to the first (into the page). Likewise, the second conduit 22 includes a connector at each end. A first connector 28 extends out of the page. The second connector 29, at the other end of the conduit 22, is located on the opposite side of the plate 11 and is therefore not visible, although it extends in an opposite direction to the first element 28 (into the page). The connectors 26, 27, 28, 29 comprise tubular members having screw threaded outer surface. The connection element 12 comprises a body having an internal screw threaded sleeve at each end. The sleeves are rotatable relative to the body. The screw thread on each sleeve is complimentary to the screw thread on the connectors. The connection elements 12 are thus arranged to connect the adjacent connectors together to form the heat exchanger 10 from a plurality of heat exchanger plates 11.

Figure 4 shows a perspective view of the modular heat exchanger 10 comprising the fifteen plates 11 (as shown in Figure 2), but with the vessel 2 and lid 3 removed for clarity. The plates 11 are shown connected together via the connection elements 24, 25, 26, 27 such that the first fluid flow path extends through one of the first or second conduits of each and every plate 11. Similarly, the second fluid flow path 22 extends through the other of the first or second conduits of each and every plate 11. The thermal store is arranged to connect to a primary and secondary loops of a heating or cooling system.

The primary loop connects to the primary loop supply port 4, which, in turn, connects to the transfer conduit 16 and then to the first conduit 21 on the first heat exchanger plate ha. The first conduit spirals to the centre 24 of the plate and a connection element 12 connects the first conduit 21 on plate ha to a first conduit 21 on the adjacent plate lib. The first conduit 21 on the second plate lib then spirals outwards to the periphery 23. A further connection element 12 connects the first conduit 21 on plate lib to a first conduit 21 on the adjacent plate lic. This continues through each plate 11, wherein the first fluid flow path is formed by a plurality of first conduits that are connected alternately at their periphery and their centre. At the fifteenth plate ho, the first conduit 21 of the fifteenth plate connects to the transfer conduit 17 which links it to the primary loop return port 5.

The primary loop therefore continues.

The secondary loop follows a similar arrangement to the primary loop.

The secondary loop connects to the secondary loop supply port 6, which connects it via transfer conduit 18 to the second conduit 22 on the first plate ha. The second conduit 22 spirals outward on the first plate ha and then via a connection element 12 spirals inward on the second plate 11 b. This continues through each plate 11, wherein the second fluid flow path is formed by a plurality of second conduits that are connected alternately at their periphery and their centre. At the fifteenth plate ho, the second conduit 22 of the fifteenth plate connects to the transfer conduit 19 which links it to the secondary loop return port 7. The secondary loop therefore continues.

In use, the primary loop may comprise a "charge" loop, which is adapted to transfer thermal energy using a heat transfer fluid from a solar panel (not shown) to the eutectic salts. The eutectic salts store the thermal energy as latent heat. The secondary loop thus comprises a "discharge" loop, which takes heat from the thermal store 1, using a heat transfer fluid, and supplies it to an under-floor heating system (not shown). The primary and secondary loops typically include a pump to move the heat transfer fluid around the loop. As the thermal store includes two fluid flow paths, it can be charged and discharged at the same time.

Figure 5 shows a flow chart that illustrates the method of installing the thermal store. In particular step 50 comprises mounting the vessel 2 at a desired location. This may be in a loft adjacent so that it is near the roof mounted solar panels. Step 51 comprises assembling the modular heat exchanger 10 from the heat exchanger plates 11. The number of heat exchanger plates 11 used may depend on the size of the vessel, the temperature of the PCM or the amount of heat transfer required for the particular installation. Step 52 comprises inserting the assembled heat exchanger 10 into the vessel and connecting the first and second conduits 21 and 22 of the two "end plates" to their respective transfer conduit 16, 17, 18, 19. The lid 3 can now be placed on the vessel 2.

Step 53 comprises connecting the primary and secondary loops to the primary and secondary supply and return ports 4,5,6,7. Step 54 comprises filling the vessel 3 to the line 13 via the filling aperture 8.

The system is now ready to operate.

If the system requires servicing, the lid 3 can be removed from the vessel and the components and PCM checked. The thermal store I is therefore very easy to install and service.

Figures 6a and 6b show a first modification to the heat exchanger 10. A heat exchanger plate 11 is shown in Figure 6a and comprises a laminar member 60 having a first conduit 61 secured to one side and a second conduit 62 secured to an opposite side. The first conduit 61 forms the first fluid flow path and the second conduit 62 forms the second fluid flow path. The first and second conduits 61, 62 follow a winding or convoluted path on their respective sides of the laminar member. The first and second conduits 61, 62 and laminar member 60 are typically of metal and thus the conduits are braised to either side of the laminar member 60.

Figure 6b shows the heat exchanger plates 11 connected together to form a modular heat exchanger 10. In this modification the connection elements 12 comprise semi-circular tubes that connect the first conduit 61 of a first plate to the first conduit 61 of a subsequent plate.

Similarly, further connection elements 20 are provided to connect the second conduits of adjacent or subsequent heat exchanger plates 11.

This is advantageous as the first and second conduits 60 and 61 can be arranged so that the first and second ends of the conduits terminate at the same edge of the laminar member. This makes connecting the heat exchanger plates 11 easier.

Figures 7a and 7b shows a further modification to the heat exchanger plate 11. In this embodiment, the plate comprises a hollow flat body 70 having the first or second fluid flow paths formed therein.

The plates 11 include a plurality of fins 71 thereon. Further, the plates are arranged alternately with gaskets 72 therebetween. The plates are arranged in groups of three. The first fluid flow path is provided by the first and second plates in the group. The second fluid flow path is provided by the second and third plates in the group. The next group is spaced from the first group to allow the PCM fluid to flow between them and is of a similar arrangement. Heat transfer directly between the first fluid flow path and the second fluid flow path therefore occurs at the second plate in the group.

Claims

CLAIMS1. A thermal energy store comprising a vessel and a heat exchanger mounted within the vessel, the vessel adapted to receive a liquid phase change material, wherein the heat exchanger includes a first fluid flow path and a second fluid flow path separate from the first fluid flow path.
2. A thermal energy store according to claim 1, in which the vessel includes a removable lid, which preferably makes a hermetic seal with the vessel.
3. A thermal energy store according to claim I or claim 2, in which the heat exchanger is removable from the vessel.
4. A thermal energy store according to any preceding claim, in which the heat exchanger comprises at least one heat exchanger plate, the plate including a first conduit that forms part of the first fluid flow path and a second, separate, conduit that forms part of the second fluid flow path.
5. A thermal energy store according to claim 4, in which the plate comprises a laminar member having the first conduit and the second conduit extending in the plane of the laminar member.
6. A thermal energy store according to claim 4 or claim 5, in which the first conduit is arranged in a substantially spiral pattern on the plate and/or the second conduit is arranged in a substantially spiral pattern on the plate.
7. A thermal energy store according to claim 4 or claim 5, in which or the first conduit follows a convoluted path on one side of the plate and the second conduit follows a convoluted path on the opposed side of the plate.
8. A thermal energy store according to any of claims 4 to 7 in which the first conduit and/or the second conduit extend in the same plane as the plate and the width of the conduit is greater than the thickness of the plate such that the plate forms webs between parts of the conduit.
9. A thermal energy store according to any preceding claim, in which the heat exchanger comprises a plurality of heat exchanger plates, each heat exchanger plate including connection elements at each end of the first conduit and at each end of the second conduit, the connection elements arranged at predetermined locations for removably connecting the plates together to form a modular heat exchanger.
10. A thermal energy store according to claim 9, in which the plates are adapted to be connected together in series.
11. A thermal energy store according to claim 9 or claim 10, in which the connection elements extend perpendicular to the plane of the plate.
12. A thermal energy store according to any of claims 4 to 11, in which the first and second conduits are arranged such that a first end of each conduit is located at the periphery of the plate and a second end of each conduit is located substantially at the centre of the plate and therefore the plates of the modular heat exchanger are connected together alternately at their peripheries and then at their centres.
13. A thermal energy store according to any preceding claim, in which the thermal energy store includes first and second supply ports and first and second return ports, the heat exchanger arranged such that the first fluid flow path connects the first supply port and first return port and the second fluid flow path connects the second supply port and second return port.
14. A thermal energy store according to claim 4 or claim 5, in which the first conduit is arranged to follow a substantially meandering path on one side of the plate and the second conduit is arranged to follow a substantially meandering path on the opposed side of the plate.
15. A thermal energy store according to claim 14, in which the first end and second end of the first conduit are located adjacent an edge of the plate and the first end and second end of the second conduit may also be located adjacent an edge of the plate, which may be the same edge as the first end and second end of the first conduit.
16. A heating or cooling system including the thermal energy store of claim 1.
17. A heating or cooling system according to claim 16, in which the first fluid flow path connects to a primary loop that is adapted to charge the thermal store.
18. A heating or cooling system according to claim 16, in which the second fluid flow path connects to a secondary loop that is adapted to discharge the thermal store.
19. A modular heat exchanger plate for use with the thermal energy store of claim 1, the heat exchanger plate adapted to removably connect to other heat exchanger plates to form the heat exchanger.
20. A modular heat exchanger plate according to claim 19, in which the heat exchanger plate includes a first conduit that forms the first fluid flow path and a second, separate, conduit that forms part of the second fluid flow path.
21. A modular heat exchanger plate according to claim 19 or claim 20, in which the plate comprises a laminar member having the 1? first conduit and the second conduit extending in the plane of the laminar member.
22. A modular heat exchanger plate according to claim 20, in which the first conduit is arranged in a substantially spiral pattern on the plate and/or the second conduit is arranged in a substantially spiral pattern on the plate.
23. A modular heat exchanger plate according to claim 20 or claim 22, in which the first conduit and/or the second conduit extend in the same plane as the plate and the width of the conduit is greater than the thickness of the plate such that the plate forms webs between parts of the conduit.
24. A modular heat exchanger plate according to claim 19, in which the modular heat exchanger plate forms part of a kit of parts comprising a second heat exchanger plate and two connection elements arranged to connect the first conduit of the first plate to the first conduit of the second plate and to connect the second conduit of the first plate to the second conduit of the second plate.
25. A method of installing a thermal energy store for a heating or cooling system, comprising the steps of; a) mounting a vessel in a desired location; b) inserting at least one heat exchanger plate into the vessel; c) at least partially liquid filling the vessel with phase change material to form the thermal store; and d) connecting the thermal store to the heating or cooling system.
26. A method according to claim 25, in which step d) includes connecting a charging supply and return conduit to the thermal store and connecting a discharging supply and return to the thermal store.
27. A method according to claim 25 or claim 26, in which step b) includes connecting a number of heat exchanger plates together to form a modular heat exchanger and inserting the connected plates into the vessel.
28. A method according to any of claims 25 to 27, in which step c) includes at least partially liquid filling the vessel with eutectic salts solution.
29. A method according to any of claims 25 to 28, in which step a) includes mounting a further vessel in the desired location and connecting the vessel and further vessel in parallel or series, and steps b) and c) are performed on both the vessel and further vessel.
30. A thermal energy store of the kind set forth substantially as described herein with reference to and as illustrated in the accompanying drawings.
31. A modular heat exchanger plate of the kind set forth substantially as described herein with reference to and as illustrated in Figures 2-4 and 6a-7b of the accompanying drawings.