BACKGROUND TO THE INVENTION Heat exchangers are well known in the prior art. Typically they consist of a coil through which water to be heated is pumped. The coil is located within a jacket through which heated water is pumped in an opposite direction to the flow through the coil.

Heat exchangers of sufficient capacity to warm a swimming pool are typically quite bulky and accordingly expensive It is an object of the present invention to provide an improved heat exchange unit which more efficiently provides for the exchange of heat and so which may be provided in a more compact form than heat exchangers which have hitherto been available.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a heat exchanger including: a housing including first and second inlet ports in respective communication with corresponding first and second outlet ports; a first fluid circuit connecting the first inlet port to the first outlet port, the first fluid circuit including a number of internal pipes located within the housing, and one or more obstacles to laminar flow disposed to produce turbulent flow through the internal pipes in use; the second fluid circuit connecting the second inlet port to the second outlet port and including a number of baffles arranged to direct fluid through the second fluid circuit about the number of pipes.

Preferably the one or more obstacles to laminar flow comprise one or more deflectors arranged to interconnect at least two of the internal pipes.

In a preferred embodiment the deflectors comprise a number of plates each located at ends of the internal pipes and configured to deflect fluid from a first pipe to a second pipe.

The internal pipes may be mounted in rows across an internal volume defined by the housing and wherein the baffles are located between the rows.

In one embodiment each deflector interconnects a number of internal pipes in parallel.

The deflectors may be arranged on opposing outer sides of the housing.

Preferably the baffles are arranged to leave gaps alternately between opposing internal walls of the housing.

Further preferred features of the present invention will be described in the following detailed description which will refer to a number of figures as follows.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a heat exchanger according to a first embodiment of the present invention.

Figure 2 is a front, and somewhat schematic, view of the heat exchanger of Figure 2.

Figure 3 is a side, and somewhat schematic, view of the heat exchanger of Figure 1.

Figure 4 is a multi-sectional perspective view of the heat-exchanger of Figure 1.

Figure 5 is a front, and somewhat schematic, view of the heat exchanger of Figure 1 in use.

Figure 6 is a perspective view of a heat exchanger according to a second, and preferred, embodiment of the present invention.

Figure 7 is a perspective and exploded view of the upperside of the heat exchanger of Figure 6.

Figure 8 is a perspective and exploded view of the underside of the heat exchanger of Figure 6.

Figure 9A is a plan view of the upperside of the heat exchanger of Figure 6 depicting the flow of working fluid through the heat exchanger's upper deflectors.

Figure 9B is a perspective stylised view of the heat exchanger of Figure 6 depicting the heat exchanger's internal baffles.

Figure 9C is a plan view of the underside of the heat exchanger of Figure 6 depicting the flow of working fluid through the heat exchanger's lower deflectors.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS A heat exchanger 2 according to a first embodiment of the present invention is depicted in Figure 1. Heat exchanger 2 includes a housing 4 which defines an internal volume and from which extends a hot water inlet pipe 6 that communicates with a hot water outlet pipe 8. In the presently explained embodiment the working fluid of the heat exchanger is intended to be hot water however other working fluids might also be applied.

An unheated water inlet pipe 10 also extends from housing 4 and communicates with a heated water outlet pipe 12. Four fluid deflectors 14,16, 18,20 are located across the top of housing 4 and three deflectors across the bottom. Each of the deflectors comprises a plate formed with slot or recess for conveying fluid. As will be explained, the deflectors form portions of a first fluid circuit between unheated water inlet pipe 10 and heated water outlet pipe 12.

Figures 2 and 3 are partial cross-sectional views of the front and side of heat exchanger 2 while Figure 4 is an exploded view of the heat exchanger showing it cut horizontally into five sections in order to reveal its internal structure. The internal path through exchanger 2, between unheated water inlet pipe 10 and heated water outlet pipe 12 will now be described. Inlet pipe 10 feeds into deflector 20. Deflector 20 in turn communicates with a first circulation leg comprising four pipes 32A-32D.

Pipes 32A-32D descend down through the internal volume of housing 4 and open out into deflector 26. Deflector 26 in turn communicates with a second circulation leg comprising four circulation pipes 34A-34D which rise up through housing 4 and out into deflector 18. A third circulation leg, comprising four internal pipes 36A-36D descends down through housing 4 and out into lower deflector 24. Deflector 24 in turn communicates with a fourth leg of four circulation pipes 38A-38D which rise up through housing 4 and out into upper deflector 16. Upper deflector 16 also

communicates with a fifth circulation leg comprising internal pipes 40A-40D which descend down through housing 4 and out into lower deflector 22. Lower deflector 22 in turn communicates with a final sixth circulation leg comprising four internal pipes 42A-42D which rise up through housing 4 and open into upper deflector 14. Upper deflector 14 in turn communicates with heated water outlet pipe 12.

It will be realised that the upper and lower deflectors and six circulation legs, each leg comprising a set of four internal pipes, provide a closed path through the internal volume defined by housing 4 between unheated water inlet pipe 10 and heated outlet pipe 12. The deflectors provide sharp transitions between the internal pipes in order to produce turbulent non-laminar flow of fluid through the pipes.

Furthermore, in the present embodiment the diameters of inlet pipe 10 and each of the internal pipes that constitute the various circulation legs are chosen so that the cross sectional area of inlet pipe 10 is slightly less than total cross-sectional area of the pipes making up each of the legs. In the presently described embodiment the cross-sectional area of inlet pipe 10 is approximately 1520 mm2 whereas the cross sectional area of each of pipes 32A-32D is 387 mm2 so that the cross sectional area of piping exiting deflector 20 is approximately 28 mm2 greater than the cross sectional area of piping entering deflector 20. As a result, in use water pumped into inlet 10 experiences a pressure drop on encountering deflector 20 which assists in producing a turbulent flow of water through each of pipes 32A-32D of the first circulation leg and indeed through each of the subsequent circulation legs.

It will be realised that other means for producing turbulent flow might be used apart from the deflectors. For example, the internal pipes might be formed with protrusions into their lumens in order to encourage non-laminar turbulent flow.

A second fluid circuit through housing 4 between hot water inlet pipe 6 and hot water outlet pipe 8 will now be described. Pipe 6 descends down through housing 4 and terminates in an angled opening 44 as best seen in Figure 2. A series of six internal baffles 46,48, 50,52, 54,56 separate angled opening 44 from hot water outlet pipe 8. Each of the baffles 46,50, 54 are disposed from front to back across the interior of the housing. A 10mm gap is left between, alternately, either the top of the baffle and the housing or the bottom of the baffle and the housing.

In use a hot water reservoir 60 is connected between inlet 6 and outlet 8.

Similarly a reservoir of water to be heated 62, for example a swimming pool or spa, is

connected between unheated inlet pipe 10 and heated water outlet pipe 12. Hot water is then pumped from the hot water reservoir, into hot water inlet pipe 6. The hot water flows out of angled opening 44 over and under baffles 46-56 and out through hot water outlet pipe 8 from whence it returns to the hot water reservoir.

The path of the hot water through the exchanger is shown as dashed line 58 in Figure 5. As the hot water flows through the baffle system it moves over the outer surfaces of each of the internal pipes 32A-32D to 42A-42D thereby heating them.

Water to be heated is pumped into unheated water inlet pipe 10 from which it enters deflector 20. The unheated water is distributed from deflector 20 into each of internal pipes 32A-32D which comprise the first circulation leg. As previously mentioned the deflectors provide a series of sharp transitions that act to produce a turbulent flow through the internal pipes. As a result the flow through the circulation legs is not laminar so that water progressing through the circulation legs makes good contact with the inner surfaces of the warmed pipes. The net effect is that water passing through the internal pipes is heated more rapidly than would be the case if the flow was non-turbulent.

The heat exchanger described with reference to the figures is intended to be used to heat a typical suburban swimming pool. The housing of the heat exchanger is 500mm wide by 200mm deep and 750mm high and is of stainless steel construction. Pipes 10 and 12 are 1. 5" diameter whereas the internal pipes and the hot water pipes 6 and 8 are 1"and are also stainless steel. The heat exchanger may be cut down so that the housing is 350mm if heating for a spa bath is required. A number of the heat exchangers may be required depending on the volume of the swimming pool or spa.

Figure 6 is an external view of a heat exchanger 64 according to a further, and preferred, embodiment of the present invention. Heat exchanger 64 includes a housing 66 which defines an internal volume and from which extends a hot water inlet pipe 68 that communicates with a hot water outlet pipe 78. In the presently explained embodiment the working fluid of the heat exchanger is intended to be hot water however other working fluids might also be applied.

An unheated water inlet pipe 76 also extends from housing 64 and communicates with a heated water outlet pipe 74. Eleven deflectors 81-91 are located across the top of housing 4 and twelve deflectors 92-93 across the underside

as best seen in Figure 7. As will be explained, the deflectors interconnect internal pipes to form a path between hot water inlet pipe 68 and hot water outlet pipe 78.

Figures 7 and 8 are perspective exploded views of heat exchanger 64 revealing twenty-four internal pipes A1-F4. The internal pipes extend the height of housing 66. At their upper limits pipes A1 and F1 communicate with hot water inlet pipe 68 and hot water outlet pipe 78 respectively. A first fluid circuit, between hot water inlet pipe 68 and hot water outlet pipe 78 is as follows, (with the direction of fluid flow through the deflectors being indicated by the arrows of figures 9A and 9C): Inlet pipe 68 to internal pipe A1 to underside deflector 92 to internal pipe A2 to upperside deflector 81 to internal pipe A3 to underside deflector 93 to internal pipe A4 to upperside deflector 82 to internal pipe B4 to underside deflector 95 to internal pipe B3 to upperside deflector 83 to internal pipe B2 to underside deflector 94 to internal pipe B1 to upperside deflector 84 to internal pipe C1 to underside deflector 96 to internal pipe C2 to upperside deflector 85 to internal pipe C3 to underside deflector 97 to internal pipe C4 to upperside deflector 86 to internal pipe D4 to underside deflector 99 to internal pipe D3 to upperside deflector 87 to internal pipe D2 to underside deflector 98 to internal pipe D1 to upperside deflector 88 to internal pipe E1 to underside deflector 100 to internal pipe E2 to upperside deflector 89 to internal pipe E3 to underside deflector 101 to internal pipe E4 to upperside deflector 90 to internal pipe F4 to underside deflector 103 to internal pipe F3 to upperside deflector 91 to internal pipe F2 to underside deflector 102 to internal pipe F1 to hot water outlet pipe 78.

It will be realised that the upper and lower deflectors and the internal pipes provide a closed path through the internal volume defined by housing 66 between hot water inlet pipe 68 and hot water outlet pipe 78. The deflectors provide a series of sharp angles or"discontinuities"in order to produce a turbulent flow of fluid through each of pipes A1-F4 in use.

A second fluid circuit through housing 4 between unheated water inlet pipe 76 and heated water outlet pipe 74 will now be described with reference to Figure 9B.

Internally housing 66 is partitioned into eight compartments by seven baffles 103- 109. Baffles 109,107, 105,103 are connected across the top and sides of the inside of housing 66 with a gap, typically 10mm, left between their lowermost edge and the inside of the casing. Baffles 108,106 and 104 are connected across the bottom and internal walls of housing 66 with a gap left between their uppermost edge and the inside of the housing. In use, water to be heated, for example from a swimming pool, flows into inlet 76 and under the first baffle 109. It then flows up and around pipes A1-A4 and over the top of baffle 108 and down around pipes B1 to B4. This pattern of flowing over and under baffles and around the internal pipes repeats until the water finally flows under baffle 103 and up and out of heated water outlet 74 by which time it has been heated by contact with the internal pipes.

In contrast to the firstly described embodiment, it is intended that a fluid to be heated be connected to the fluid circuit that passes over and under the baffles and that the fluid providing the heat be passed through the internal pipes. For example, a swimming pool to be heated might be connected between inlet 76 and outlet 74 and a source of heated water passed between inlet 68 and outlet 78.

As previously mentioned in relation to the first embodiment, the heat exchanger provides improved efficiency by producing turbulent, i. e. non-laminar, flow through the internal pipes. The non-laminar flow in turn has been found to increase the efficiency of the heat transfer from one fluid to the other.

The embodiments of the invention described herein are provided for purposes of explaining the principles thereof, and are not to be considered as limiting or restricting the invention since many modifications may be made by the exercise of skill in the art without departing from the scope of the invention as defined in the following claims.