The present invention relates to improvements in tA heat exchange fluid coil assembly of a thermal stc . apparatus particularly as described in United Stat_._.

Patent No. 5,143,148, a method and apparatus for winding the coil assembly and arrangements for distributing the heat exchange fluid t the coil assembly.

BACKGROUND OF THE INVENTION

As described in United States Patent 5,143,148, a thermal storage apparatus is comprised of a stack of individual modules. Each module has a base, a peripheral wall, a path defined by channels or raceways which can circulate a fluid storage medium when in its fluid state between an inlet and an outlet of the module and a heat exchange fluid circuit circulating a heat exchange fluid across the base of the module. The heat exchange fluid coils, are also referred to as refrigerant coils in said patent (since storage is of a refrigerated medium rather than a heated medium which is also possible in such apparatus), and extend in a pattern substantially conforming to that of the channels defining the path for the phase change medium fluid. This promotes efficient heat transfer.

The fluid storage medium may include a phase change medium fluid, for example water, or other medium such as a glycol-water mixture or similar.

As described in United States Patent 5,143,148, thermal storage occurs firstly by cooling of the fluid storage medium and principally, in the case of a phase change medium fluid, by conversion of the fluid to its solid form (water to ice), which involves a large

energy change due to the latent heat of fusion.

The storage medium is kept in a partially fluid (liquid) state to allow utilisation thereof by circulation of the fluid externally of the module to a load requiring cooling. This is preferred as when the phase change medium is solidified to the point preventing its circulation, the apparatus cannot be utilised until circulation is restored or unless the "refrigerant" circuit is employed for this purpose.

This latter requirement would involve a heat exchange fluid circuit allowing switching between these modes of operation.

Apparatus and method for preventing blockage of storage medium circulation and allowing the heat exchange fluid circuit to be switched between various circuits and modes of operation is described in PCT application PCT/AU93/00538.

The path of the storage medium fluid can be spiral, serpentine, zig zag, each of which can be considered to be a serial path across the base, or can be a number of parallel paths extending from one side of the base to the other. Examples of these forms are described in said US patent. Hence the coil may be spiral, serpentine, zig zag or parallel.

In United States Patent 5,143,148 the coil is shown as a single element in each channel either fixed to the top or bottom of the base or formed between the top and bottom of the base. The present invention provides an improvement in that construction.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a thermal storage module including a

substantially planar base;

a heat exchange fluid conduit for circulating a heat exchange fluid (HEF) from a HEF inlet to a HEF outlet along a path extending across and parallel to said base,

a perimeter wall extending substantially vertically from said base around the perimeter of said base;

a plurality of channels, each channel defined by a pair of internal walls each having an axis substantially normal to the plane of said base, each channel extending along and aligned substantially parallel with said path, for containing a phase change medium (PCM) fluid in contact with said HEF conduit; and

wherein said heat exchange fluid means includes a coil assembly having a plurality of coils following said path accommodated within said channels supported by a bracket arrangement. Preferably the coil assembly has a plurality of coils and the coils are connected in parallel within e module to reduce the pressure required to driv-_ the refrigerant therethrough.

In addition the invention provides for an inlet liquid distributor for the heat exchange fluid which distributes the refrigerant fluid evenly to each coil of said plurality of coils when connected in parallel.

According to a second aspect of the present invention there is provided a thermal storage module including a substantially planar base;

a heat exchange fluid conduit for circulating a heat exchange fluid (HEF) from a HEF inlet to a HEF outlet

along a path extending across and parallel to said base,

a perimeter wall extending substantially vertically from said base around the perimeter of said base;

a plurality of channels, each channel defined by a pair of internal walls each having an axis substantially normal to the plane of said base, each channel extending along and aligned substantially parallel with said path, for containing a phase change medium (PCM) fluid in contact with said HEF conduit; the improvement comprising,

wherein said heat exchange fluid means includes a coil assembly having a plurality of coils following said path wherein the coils are in parallel circuits within said module, each coil being accommodated within said channels supported by a bracket arrangement and an inlet liquid distributor for the heat exchange fluid which distributes the refrigerant fluid substantially evenly to each of said coil circuits.

The flow of refrigerant through the coil assembly may be unidirectional or bidirectional depending upon the number of coils employed. The number of coils within each channel or raceway of a module will depend upon the cooling desired or on spatial restrictions within the channels but from 1-8 coils per module are contemplated. Each coil circuit may comprise a single coil extending the length of the channels or a pair of such coils joined together, although a coil circuit may also include more than 2 coils.

In a unidirectional arrangement the flow of the heat exchange fluid will be in the same sense within each coil circuit and within each channel, for example, in

the case of a spiral path a number of coils will extend from the centre to the periphery of the module with a liquid distributor joined to the inlet ends and a manifold to the outlet ends of the coils at these respective locations.

In a bidirectional spiral flow arrangement, a coil circuit may extend from the periphery to the centre where it would reverse and unwind outward to the periphery along each channel . The outward spiral path could be placed alongside or on top of or otherwise spaced from the associated inwardly spiralling coil. A number of such inward and outward coils may then be combined in each channel as desired. Preferably, the lengths of the inward and outward coil paths would be substantially equal to ensure equal fluid distribution between them.

The coil assembly may be made up of a number of such inward and outward coils joined in pairs, or an equal number of inward and outward coils may be made into one piece. The latter arrangement is not preferred as it results in a large pressure gradient across the coil assembly requiring a more powerful pump to drive the heat exchange fluid through the circuit.

It is preferred that in a bidirectional arrangement the coils be in a number of separate single pairs only, viz. an inward and an outward return, rather than a single continuous circuit.

In a bidirectional coil arrangement the inlet and outlet points will be in the same regions of the module and may be either at the periphery or the centre as the case may be. For the reason of limited space at the centre of a module the inlet and outlet liquid distributors and collectors will preferably be

at the periphery for such a bidirectional flow circuit but not necessarily.

Raceways or channels for the phase change medium can vary in width depending on the capacity of the apparatus comprising a module or a stack of modules. In a small system the raceways are typically 80-100mm wide whereas in larger systems the channels are from 160-185mm wide. The smaller systems would normally carry a number of coils stacked one above the other and typically 1-8 coils can be used. In larger systems, the number of coils can be increased and can be arranged side by side as well as vertically. These aspects are matters of design.

Preferably, the refrigerant liquid distributor includes an inlet port ahead of a conical fluid separator with the base of the cone having a plurality of outlet ports spaced thereabout and to each of which is connected a distributor line at the end of which fluid at a substantially equal pressure is provided for connection to each coil circuit of a coil arrangement.

The invention also relates to improvement in the method and apparatus for winding the refrigerant coil assembly for the above coil arrangement.

According to a further aspect of the invention there is provided an apparatus and method for winding a spiral coil arrangement for a thermal storage module as described above. The coil winding apparatus includes a rotor disc fixed to which is a pair of spiral forms extending between the centre and the periphery of said disc and separated from each other by a radial gap for later accommodating internal walls forming the channels of a module, an array of

upstanding arms or posts fixed to said spiral forms and facing each other in pairs at intervals therealong, said arms or posts being shaped to support elements of said bracket arrangement to which coils of said coil arrangement are to be secured, and means to rotate said disc.

The method for winding a coil arrangement using said aforesaid apparatus includes:

a) placing said supporting elements in each of said posts;

b) winding coil from a drum along one of said spiral forms by rotating said disc while securing the coil to said elements starting from the centre of said disc and working outwards;

c) repeating step (b) for the other spiral form;

d) repeating step (b) and (c) for the number of coils in the arrangement desired; and

e) removing said completed coil arrangement from said disc.

Preferably, the alternate coil windings are clipped into slots of a pair of bracket arms. Preferably, the bracket arms are linked top and bottom by respective cross arms with the lower cross arm fixed to the bracket arm pair at step (a) and with the upper arm fixed to the bracket arm pair before or after step (e).

Preferred embodiments of the invention will now be described with respect to the following drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the cross section of a module employing a unidirectional fluid circuit according to the invention;

Figure 2 shows a cross section of a module employing a bidirectional circuit flow according to the invention;

Figure 3 shows in greater detail the coil support arrangement for the coils as shown in Figures 1 and 2;

Figures 4 and 5 show respectively the inlet liquid distributor and inlet arrangement for the embodiment of Figure 1;

Figure 6 shows a plan view of an insulated lid for covering a stack of modules of the embodiment of Figure 1; and

Figure 7 shows a partial plan view of the rotor of winding apparatus for forming the coil arrangement according to the invention.

PREFERRED EMBODIMENTS OF THE INVENTION The preferred embodiments will be described with respect to a cylindrical module having a spiral path for circulating the phase change medium and for the coils . Other module shapes or forms for circulation of these media are contemplated as readily described in United States Patent No.5, 143, 148.

The module can be made of varying diameters but preferably has a depth of 100-330 millimetres.

As shown in Figure 1, the module 10 has a number of raceways or channels 12 for circulating the storage

medium fluid (wate: _: . in a spiral path. Along this path is accommodated a heat exchange fluid coil assembly 14 of similar (i.e. spiral) shape comprising a number of separate coil circuits 16, 16', 18, 18', 20, 20' and 22, 22'. The coil circuits 16-22 and 16'-22' are arranged at the outer and inner radii respectively within the channels 12 supported by the brackets 24 at suitable intervals along the length of the coils.

The brackets 24 can simply rest upon the base 7 of the module but are preferably secured in place such as by adhesive bonding to prevent movement of the coils during a thermal cycle of the module, during transport and to aid circulation of fluid around the coils and brackets. In addition, the brackets are secured to the base since ice formed about the refrigerant coils (and being less dense than in its liquid state) exerts an upward buoyant force on the coils which the secured brackets can better resist.

The coils 16-22 and 16 '-22' are snap fit into the apertures 26 of each support bracket 24, as described below.

The refrigerant, or in general terms the heat exchange fluid (HEF) flows in at the centre 9 of the module 10 and thence along the spiral as shown by the path 1 for the unidirectional flow arrangement illustrated in Figure 1. The refrigerant exits the module 10 at the periphery 13 with the coils passing through the peripheral wall 15 of the module .10.

As well as the HEF, the phase change medium (PCM) can follow the direction of path 1, flowing in at the centre 9 and out at the periphery 13, although, in general, (PCM and HEF) need not be in the same sense.

Equally, the flow of either the PCM or the HEF may commence at the periphery 13 and exit at the centre 9 (the reverse of that shown in Figure 1). These factors are matters of design. For example, in a stack of modules of this type, it may be convenient to have the PCM path in alternate modules reversed (as described in US 5,143,148,) while the HEF path is the same in each (such as path 1 in Figure 1) entering at centre 9 and exiting at periphery 13. Whether the modules have unidirectional or bidirectional coil assemblies, the heat exchange fluid coil can be connected from the centre to the periphery of a module (or vice versa) by traversing the top of a module with the coil being accommodated in slots cut radially in the top of the channel walls . The coil would be sealed to the channel walls to prevent leakage of phase change medium between channels.

The bracket 24 is made to, at least, accommodate the number of coils required. Extra apertures may be provided so that some of the apertures may not be initially occupied allowing a later increase in the capacity of the module as required. The inlets for the coils are connected to an inlet liquid distributor (as described below) and the outlets to a liquid/gas collector manifold.

Figure 2 illustrates a bidirectional circuit. The coil 30 supported by arm 25 of bracket 24 moves in the inward direction of arrow 31 of the spiral. Once at the centre of the module the coil reverses direction and spirals outward following the direction of arrow 33 and forming the outward coil 32 which passes alongside but spaced from the inward coil 30 upon arm 25' of bracket 24. The support bracket 24 as shown has two arms 25, 25' which support respectively each inward and outward turn of the spiral separately. In

this embodiment the entry and exit for the coils 30, 32 are at the periphery of the module. The bracket 24 as shown can accommodate 4 pairs of such coils 30, 32 although other arrangements of coils are contemplated.

In place of a pair of bracket arms 25, 25' a single bracket arm may be employed to which the separate inward and outward spirals are attached one atop the other.

The unidirectional coil assembly of Figure 1, or the bidirectional coil of Figure 2 can be made in separate coil segments (extending one spiral circuit across the base), or may be made in discrete pairs or the pairs joined as a single piece, that is the "reversals" of the spirals at the periphery and at the centre being joined to make the multiple coils continuous. The latter makes the need for a liquid distributor unnecessary. However, it is preferred that separate coil segments are employed with the segments in parallel, for the reason stated above, with refrigerant liquid distributors or connectors required to connect respective ends of adjacent coil segments.

In the unidirectional coil ...ssembly of Figure 1, the separate inner and outer spirals within a channel are of different radii for the bracket shown (with spaced arms 25, 25'. The coils are therefore of different lengths. To equalise the lengths of these coils (and equalise the pressure drop experienced in each) these coils may be crossed-over at their midpoints so that half of the inner coil is connected to half of the outer coil and vice versa. This factor may also be applied to other coil assemblies as required.

In a bidirectional coil arrangement the inlet and outlet for the h^at exchange fluid will both be at the

same region of the module, for example at the periphery as compared to the unidirectional arrangement where these are at the periphery and at the centre of the module.

Referring to Figure 3 the bracket 24 comprises a pair of upright T-shaped support bars 40, 40' each having a number of arcuate slots or apertures 44, 44' along the leg of the T, the caps 41, 41' of the Ts forming the outer edges of the bracket 24. The upright bars 40, 40' are joined by horizontal spacer bars 42, 43 at their top and bottom. The spacer bars 42, 43 are of a slotted T-shape with the legs of the upright bars 40, 40' accommodated in the slots 45, 45'. The length of the upper spacer bar 42 may also be extended (as shown in dotted line 42') to the full width of a channel. This provides support between channel walls and, when modules are superposed, transfers the applied weight more evenly to the base of a module. The bracket upright bars 40, 40' in the latter case would extend the height of the channel walls 11.

The entrance 46 to the apertures 44, 44' narrows from a wider portion 47 to a portion 49 slightly smaller than the diameter of the coil to be accommodated. This aids insertion and subsequent retention of a coil in aperture 44, 44', the coil being pressed into the apertures 44, 44' and held with a snap fit. This aids their retention against the induced buoyancy when ice is formed.

The elements 40, 40' 42, 43 of bracket 24 are made of a plastics material and the apertures 44, 44' are approximately 50 mm. apart with the outermost apertures 25 mm. from the spacer bars 42, 43. This spacing is typical for a 300 mm. deep channel but is

chosen, in general, to optimise solid phase buildup while still allowing adequate circulation of the thermal storage medium (water) even when there is substantial solid phase buildup.

The bracket may also be formed as a single bar of inverted T shape, with the cross bar or cap of the T resting on or preferably glued to the base 7 of the module and the upstanding leg of the T having a number of arcuate slots (of the form 44, 44' described above) to accommodate the heat exchange fluid coils. These slots may be on one side only of the leg or may be on both sides. With this form of bracket a channel may carry a single or dual circuit.

The coils can be accommodated one on top of the other or side by side whether the flow is unidirectional or bidirectional.

The material for the heat exchange fluid coils can be any material well known in the art depending upon the refrigerant employed and other relevant factors such as availability, cost and durability for the purpose envisaged. Typically the coils may be made of copper, stainless steel, brass, steel or plastics material.

The spiral coil assembly described above is made on a windir machine as shown in Figure 7. A rotor disc 90 has welded thereto a pair of metal spiral forms 92, 94 which are separated by a radial gap 96 of sufficient width to represent and allow subsequent accommodation of the internal walls defining the channels or raceways of a module, as discussed above. An array of upstanding arms or posts 100 are welded to these spiral forms 92, 94, facing each other at regular angular intervals therealong (for example, along radials). The posts 100 are C-shaped and act as

slotted guides for the bracket upright bars 40, 40' (with the lower spacer bar 43 joining and holding the upright bars 40, 40' in place). The posts 100 aid in the guiding and forming of the coil tubing into the required spiral form.

Rotor 90 on its underside has a geared cog wheel driven by an infinitely variable speed motor having a speed range of 0.5-6.0 rpm which can be adjusted by an operator with a hand or foot control. As the rotor is rotated in the direction of the arrow 105, the coil tubing 101 is fed from a horizontal axis feed drum from the periphery toward the centre of the rotor. The winding of a coil 101 starts from the centre 103 with the tubing curved and bent to fit past the slotted guide posts 100 as rotor 90 rotates. A spring bender may be used to help form each coil to the required curvature as it reels from the supply drum. Spacing elements (6mm. thick blocks) may also be used for this purpose midway between the guide posts 100.

The upright bars 40, 40' are raised to the top of the guide posts 100 for the first coil circuit to make it easier to mate and press the coil into the apertures 44, 44'. The innermost winding is done first, followed by the outermost. Then as subsequent layers of coils are added the upright bars 40, 40' are lowered down the guide posts 100 by the operator and in part by the coil tension and weight.

In an alternative embodiment, the rotor has angularly arranged slotted radial plates to grip and to wind the coil in the required form. Slots are cut at positions corresponding to the desired coil curve. Posts precede the slots and align the coil with the slot as the coil tubing is fed from the outside inwardly towards the centre of the carousel rotor. With the

bracket in place in a post the separate turns are manually pressed into place.

Once the desired number of turns have been added the top cross members are added to the columns and glued in place. The coil assembly is then removed from the winding machine and can then be inserted into the module which has previously been assembled with base, peripheral wall and spiral channel wall (forming the raceways) in place.

The necessary connections to the coil assembly at the periphery and centre of the module can then be made. Depending upon the coil circuitry the separate coil elements are connected to the peripheral outlet liquid collector or inlet liquid distributor.

An apparatus comprising a stack of modules is provided with a lid. Referring to Figure 6 the lid 118 has a number (6) of radial reinforcing arms 120 comprising two pairs forming the shape of a twisted X shape and a pair of linear form, each arm being made of inverted (closed) channel section and secured to a level recessed portion 119 at the periphery of the lid 118 by bolts or rods 121.

The heat exchange fluid is conducted from inlet 122 at the periphery 124 of the apparatus along and within one such radial arm 128 to the centre 126. There the fluid connects to the coils in each module via the inlet distributor 150 as shown by arrow 130. The fluid exits from each module (not shown) into the bulbous housing 132 where it connects to other of the refrigeration circuitry, for example including a suction accumulator, heat exchanger or surge drum represented diagrammatically by numeral 186. The operation of the latter is described in our

application PCT/AU93/00538. The heat exchange fluid circuit would also include a liquid refrigerant pump 188 to drive the refrigerant through the modules, a thermostatic valve 190 to control the liquid level, and a compressor/condenser (not shown) to liquify gaseous refrigerant produced from the passage of the liquid refrigerant through the modules.

The inlet and outlet connections for the phase change medium can be either at the periphery or at the centre of a module. In the latter case the inlet or outlet flow may also use a radial arm 128' to connect to or from the centre. A pump 192 is also provided for circulating the phase change medium (water) , when a fluid, through the modules of the apparatus and/or externally thereof as required under the control of valves (see, for example, PCT/AU93/00538) .

Because the PCM (water) of a module, or a stack of modules, is connected to an external load there is a need to provide in the modules an additional water reservoir so that, when the flow is started, a quantity of the PCM is available for priming the pump or the tubing of the external load. This is especially true if the pump and external load are periodically disconnected and cleaned as may be required for hygienic purposes (for example, if the cooled water from a thermal storage apparatus is used to cool milk at a dairy) . For this purpose additional PCM volume can be provided at the periphery at the end of the outermost channel in a region where there are no HEF coils.

Lid 118 has a transparent viewing port 134 to observe the ice buildup in the apparatus or to inspect the water level during filling or operation of the apparatus.

At the centre, the refrigerant has to be equally distributed so that the pressure drop in each coil of the assembly is substantially the same. This is to ensure that there is an equal fluid flow, and hence cooling effect, in each coil of a module and each module of the whole apparatus . This is effected by arranging the length of the piping within the inlet liquid distributor to be equal . A typical inlet liquid distributor is shown in Figure 4.

The inlet distributor 150 comprises a central pipe 151 feeding refrigerant to a distribution point 148 midway along an outer containing cylinder 152. Distribution point 148 comprises a venturi 140 which narrows the flow of refrigerant liquid coming from the pipe 151. The flow is then expanded into the bulbous body 142 while impinging on conical separator 144 to be thence directed through the outlet ports 146.

Cylinder 152 is slit along approximately 90% of its length to allow exit of the required number of capillary tubes 154 to supply refrigerant to the coils for each of the modules of an apparatus. As stated above this number per module may vary from 1-8 but is typically 4-8 per module.

The length of each connection 156 from the distribution point 148 to the associated capillary tube 154 is made the same so that the refrigerant flow does not vary depending upon where it is located in the apparatus. Hence to feed a capillary close to the distribution point 148 the connection 156' extends half the length of the furthermost module and folds back before joining to the associated capillary 154'.

The capillary tubes 154 project 100-200 mm. through

the wall of the containing cylinder 152 to allow connection to the refrigerant (heat exchange fluid) coils, for example by silver soldering, by which method the connections 156 are also connected to the distribution point 148. Typically capillary tubes 154 are from 6.15mm (5/32") to 14.76mm (3/8") depending on the total number of capillaries in an apparatus, their length, the thermal capacity of the apparatus, the desired operating temperature for the apparatus, the refrigerant employed and its temperature and pressure of operation.

In place of a single distributor several separate distributors of the above construction may be used for a large apparatus. Typically the above construction is contemplated for use with apparatus with 8-12 modules. Smaller apparatus may employ a variation of the above construction with the distribution point 148 at the top of the containing cylinder 152 rather than midway therealong as shown.

The components 148, 151 of the distributor 150 are typically made of brass and plastics material respectively with the capillary tubes 154 and connections 156 made of copper. Once these components are assembled the containing cylinder 152 is filled with an insulating material 184 (see Figure 5) , for example gel coated polyurethane foam to minimise any thermal losses and to water proof the assembly.

Referring to Figure 5, which shows the central region of a module of the type described with respect to Figure 1, viz. with a unidirectional flow circuit for refrigerant, the distributor 150 is located to one side before the start of the spiral, as shown. Alternatively, it may be located in region 185, at the start of the spiral channel 12 formed by channel wall

11. An aperture 180 allows for ingress or egress (depending on the circulation pattern employed) of the phase change storage medium between superposed modules. Capillary tubing 154 connects from the distribution point 148 (as described above) to the coils 16, 16' at the start of the coil circuits. With the distributor 150 located in alternate region 185 the connection path for the capillaries 154 to coils 16, 16' is more direct.

The distributor 150 is accommodated through holes in the base of each module and then bonded thereto with the join to the base of each module being made leak proof.

The invention is contemplated for use with primary or secondary refrigerants for the heat exchange fluid. Examples of primary refrigerants are R22, R502, R717, R414, AZ50 and of secondary refrigerants are brine or water/glycol mixtures.

Though the invention has been described above with respect to preferred embodiments above thereof, variations are contemplated within the knowledge of a person skilled in the art.