GB2530660A

GB2530660A - Heat recovery for grey water systems

Info

Publication number: GB2530660A
Application number: GB1515604.5A
Authority: GB
Inventors: Harry Ranford
Original assignee: ECO TRAY Ltd
Current assignee: ECO TRAY Ltd
Priority date: 2014-09-05
Filing date: 2015-09-03
Publication date: 2016-03-30
Also published as: GB201515604D0; WO2016034838A1; GB201415707D0

Abstract

A heat recovery system recovering heat from waste water comprises a waste water receptacle 4 receiving waste water. The receptacle is connected to a waste water drainage pipe (34, fig 3) and functions as a heat exchanger comprising an input port connected to mains conduit for incoming (fresh) water, and an output port for removing water from the exchanger that has been heated. At least two conduits extends between the input and output ports whereby heat energy from the waste water is transferred to the incoming water. The conduits have a cumulative / combined cross sectional area equal to or greater than the mains conduit and having a greater heat exchange surface area than the mains conduit. The receptacle may be a bath, sink or shower tray and incoming water is pre-heated before delivery to a shower head 8. The receptacle may comprise a plurality of parallel and adjoining welded pipes (20, fig 2) having a non-circular cross-section, i.e. flattened, oval, or v-shaped cross section (fig 9) whereby an upper flat sheet (42) is connected to a lower undulating sheet (44). A thermostat may monitor temperature of the preheated water and regulate / reduce power to an electric heater 10.

Description

Heat Recovery from Grey Water Systems

TECHNICAL FIELD

The present invention relates to the recovery of heat from grey water systems, particularly but not exclusively to the recovery of heat from the waste water of shower systems.

BACKGROUND

A recurring dilemma of modern times is how to improve energy efficiency in the home. It is well known that a significant amount of household energy is wasted, for example in the form of central heating being lost from poorly sealed windows or through the roof of a building or lights being left on when they are no longer required. Another significant contributor to energy loss in households is the large volume of hot water that is washed down the drain, for example from sinks, showers, baths, dishwashers and washing machines. A shower is particularly wasteful because the water is used for only a few seconds before it is dispensed of down the drain, taking a significant amount of heat energy with it.

A high proportion of hot water consumption in a domestic household is used for showering resulting in the shower being a major contributor to low energy efficiency within the home.

Shower systems have been adapted to try to recover at least some of the heat energy that is normally lost down the drain. For example, the Recoh-trayTM comprises a heat exchanger in the form of spherical copper shell that is placed beneath and coupled to the shower tray and waste water flows across the shell from the centre to the outside.

Copper pipes are provided underneath the shell through which incoming mains water can flow to be preheated by the waste water thereby reducing the amount of energy input required to operate the shower at a satisfactory temperature. An alternative system is supplied by Recoup Energy Solutions Ltd where hot water flows through the shower drain and is directed to a pipe exchanger remote from the shower. The exchanger has a cold waterfeed on the other side, allowing heat to be transferred from the outgoing hot water to the incoming cold water to pre-heat the water that is then fed to the shower mixer, boiler or cylinder.

These systems aid heat recovery in the home but it is always desirable to increase the proportion of heat that is recovered from grey water waste thereby further minimizing the amount of heat energy lost.

It is an object of the present invention to provide an improved heat recovery system that aims to overcome, or at least alleviate, at least one of the aforementioned drawbacks.

A further object of the present invention is to provide an improved shower system that aims to overcome, or at least alleviate, at least one of the aforementioned drawbacks.

SUMMARY OF THE INVENTION

Accordingly, one aspect of the present invention provides a heat recovery system for the recovery of heat from waste water, the system comprising a waste water receptacle for receiving waste water, the receptacle being adapted for connection to a waste water drainage pipe, the waste water receptacle consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water, and an output port for removing water from the exchanger, wherein the mains conduit is in fluid communication with at least two subsidiary conduits extending at least partially between the input and output ports, the at least two subsidiary conduits having a cumulative internal cross-sectional area substantially equal to or greater than that of the mains conduit but having a greater heat exchange contacting surface area thereto, whereby heat energy from the waste water received on the receptacle transfers heat energy directly to the incoming water in the conduits

I

The waste water receptacle may be any form of receptacle that receives warm water, such as a shower tray, bath or sink. The present invention is particularly suitable for the recovery of heat energy from shower water waste. To this end, a second aspect of the present invention provides a shower system comprising a heater for increasing the temperature of incoming water, a shower head for the delivery of heated water to a shower tray, the shower tray being adapted for connection to a waste water drainage pipe, the shower tray consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water, an output port for removing water from the exchanger, wherein the mains conduit is in fluid communication with at least two subsidiary conduits extending at least partially between the input and output ports, the at least two subsidiary conduits having a cumulative internal cross-sectional area substantially equal to or greater than that of the mains conduit but having a greater heat exchange contacting surface area thereto, whereby heat energy from the waste shower water is received on the shower tray and transfers heat energy directly to incoming water in the conduits.

The heat exchanger may comprise an entire upper surface of the waste water receptacle or may only form part thereof, for example being embedded in a conventional waste water receptacle such that an upper surface of the heat exchanger is arranged for direct contact with the waste water. More preferably, the entire heat exchanger forms the waste water receptacle.

In an embodiment, the waste water receptacle is comprised of a plurality of substantially parallel and adjoining conduits or pipes, one end of each of the conduits being in fluid communication with a pipe or conduit that is in fluid communication with the input port and the opposite end of each conduit being in fluid communication with a pipe or conduit that is in fluid communication with the output port. More preferably still, the parallel pipes that form the heat exchange region of the receptacle comprise non-circular pipes, especially being flattened or oval-shaped pipes in cross-section.

The dimensions of the pipes are optimized such that the flow of incoming water is substantially maintained throughout its passage through the tray. Preferably, this is achieved by the total internal cross-sectional area of the multiple pipes being substantially equal to the internal cross-sectional area of the mains input pipe or conduit. For example, a large diameter mains pipe preferably separates into multiple flattened pipes, the cumulative internal cross-sectional area being substantially the same as the internal cross-sectional area of the single mains pipe but the flattened multiple pipes providing a larger heat exchange contacting surface area.

The waste water receptacle may comprise an upper, substantially flat sheet of material connected to a lower corrugated sheet wherein the peaks of the corrugation are joined to the upper sheet such that the waves of the corrugation form substantially V or U shaped pipes in cross section between the upper and lower sheets. Preferably, the pipes are V-shaped in cross-section. Reinforcement may be provided within the tray, for example in the form of ribbing provided at the regions of tray where the upper and lower sheets connect together. The sheets may be joined together to form a tight seal by any suitable means, such as welding or die casting.

The surface of the waste water receptacle which receives the waste water preferably includes a gentle gradient to direct waste water to the waste water drainage pipe while allowing the water sufficient contact time with the heat exchange surface.

In an alternative embodiment, the heat exchanger comprises a continuous convoluted pipe connected at one end to the input port and at the other end to the output port.

Preferably, each convolution doubles back such that each section of the pipe is in contact with its adjacent sections, thereby providing a solid waste water receptacle. A similar type of heat exchanger may be provided by the inclusion of appropriate partitions within a single casing that has an input and output port. Again, the internal conduits provided by the pipes and/or partitions are preferably of small cross-section and have a flattened upper surface.

It is to be appreciated that the heat exchange part of the waste water receptacle is formed of a conductive material to allow for an efficient transfer of heat from the waste water to the incoming water. Preferably, the heat exchanger comprises copper or aluminium pipes.

Anodised aluminium pipes or sheets may preferably be used. This could also be pigmented to provide receptacles, such as shower trays, of different colours or shades.

However, other suitably conductive materials may be used, such as plastics materials, provided they have the necessary conductive properties.

In a preferred embodiment, the heat exchanger comprises a series of multiple, preferably three, S-plan flattened subsidiary pipes or conduits running substantially parallel to one another from a mains conduit at the inlet port to a conduit at the outlet port. Preferably, the pipes are formed by a 3-layer sandwich comprising three sheets of a conductive material wherein the middle layer is relieved of material to provide the sides of the multiple pipes, the upper surface of the pipes is formed by the upper layer of the conductive material and the lower surface is formed by the lower layer. In this manner, a compact, solid receptacle is provided with the heat exchanger in direct contact with the waste water as it falls onto the receptacle. Thus, heat energy from the waste shower water is received on the shower tray and transfers heat energy directly to incoming water flowing through the parallel pipes. Alternatively, this arrangement may be formed from a single piece or two pieces, for example by pressing. Pressing the sheets to form the subsidiary conduits may be also used to provide protuberances extending upwardly from the upper surface of the heat exchanger, for example being in the form of a mirror image of the subsidiary channels or of a different design. These protuberances may aid grip on the upper surface of the receptacle and/or aid flow of the waste water over the receptacle for contact with the heat exchanger In this embodiment, the input port is preferably provided across the input ends of all the subsidiary pipes, and the output port is provided across the output ends of all the subsidiary pipes.

Preferably, the input ends and output ends of the pipes are provided within the boundaries of the receptacle and extend substantially upwardly or downwardly in relation to the upper surface of the receptacle, as opposed to laterally. Optionally, a swivel connector may be provided to attach the mains conduit to the input and/or output ports.

In a preferred embodiment of the present invention, an insulating layer is provided beneath the heat exchanger More preferably, the insulating layer also provides support for the waste water receptacle.

Conduits for transferring the heated mains water that has passed through the heat exchanger to the shower head are preferably insulated or insulating to retain as much of the heat as possible.

In a further embodiment, the heat exchange pipes may be cast to form a tile-like structure.

Such an arrangement is particularly applicable for installation in wet rooms.

The waste water receptacle of the present invention may be provided as a stand-alone product for installing in an existing waste water system. To this end, a third aspect of the present invention provides a waste water receptacle being adapted for connection to a waste water drainage pipe, the waste water receptacle consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water, an output port for removing water from the exchanger, and multiple conduits between the input and output ports wherein the multiple conduits have a cumulative internal cross-sectional area substantially equal to, or greater than, the mains conduit connectable to the input port but having a greater heat exchange contacting surface area thereto.

More preferably, the waste water receptacle comprises a shower tray.

A kits of parts for installing a heat recovery system according to the present invention may also be provided. Suitable control means may also be included to optimize the energy input into the system depending upon the amount of heat transferred to the incoming water For example, in the case of an electric shower system, a thermostat may monitor the temperature of the incoming water and reduce the power input to the heater upon detection of a predetermined temperature, such as by switching off one or more heating elements of an electric shower heater.

It is to be appreciated that a cushioning and/or anti-slip mat may be provided on top of the heat exchanging upper surface but this would reduce the efficiency of heat transfer.

Ribbing may be provided on the mat to aid the flow of water over the tray into the input port.

It is preferable for substantially all water from the shower to be directed into the waste water receptacle for maximum heat transfer To this end, it is preferable for surfaces surrounding the shower to include a hydrophobic coating to repel water from the surface.

For example, surrounding tile surfaces and shower doors are preferably provided with such a coating on their surface.

The relative dimensions of the conduits within the heat exchanger, the overall surface area of the heat exchanger and the shower output are important for providing a satisfactory flow of water through the heat exchanger so that satisfactory heat recovery is provided by the system. In particular, the mains conduit connected to a conventional mains input communicates with a plurality of flattened conduits or pipes thereby providing a greater surface area for heat exchange whilst maintaining the overall internal capacity to minimise any reduction in flow through the pipes comprising the heat exchanger Preferably, the internal diameter of the input mains conduit is 15mm with the conduit being in fluid communication with at least three flattened tubes having an internal depth of 0.5 -2mm, preferably 1.2mm and a width of 30-50mm, preferably 40mm. However, it is to be

S

appreciated that these parameters may be scaled up or down as appropriate.

Furthermore, the overall power output may be dictated by the overall dimensions of the receptacle. For example, a larger shower tray will provide for a greater heat exchange than a smaller tray comprised of the same layout/configuration of multiple conduits between the input and output ports.

The hot water system may be provided with a single or multiple heating elements for heating of the water. Preferably, the hot water system, such as a shower, is provided with two or more heating elements which are of a lower power output than conventional heating elements. Preferably, the heating elements have a power output of 1.2 kW -5.2 kW per element. More preferably, the power to the or each heating element may be switched on or off or increased or decreased in response to the temperature of the incoming water, for example by suitable switching means, TRIACs or a microprocessor In one embodiment, each heating element is operably connected to a switch with each switch set to a different temperature such that as in the inlet water temperature rises the elements are progressively switched out.

A suitable valve system may also be provided to alter the amount of hot water being added to the incoming hot water mains system following its passage through the heat exchanger and prior to its delivery to the shower head.

The inlet port may also be provided with a suitable filter to prevent debris entering the heat exchange pipes. Additionally, or alternatively, a cleaning agent may be provided in the input port, for example in the form of a soluble cleaning tablet, for intermittent or continuous cleaning of the heat exchange pipes.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: Figure 1 is a schematic diagram of a shower system incorporating a heat recovery system according to one embodiment of the present invention; Figure 2 is a plan view of a heat recovery system according to an embodiment of the present invention; Figure 3 is cross-sectional view along line A-A of Figure 2; Figure 4 is a cross-sectional view along line B-B of Figure 2; Figure 5 is an expanded view of section C of Figure 4; Figure 6 is a plan view of the heat exchanger for a heat recovery system according to the present invention; Figure 7 a cross-sectional view of the heat exchanger shown in Figure 6; Figure 8 is an example of an alternative configuration for a heat exchanger for use in a heat recovery system according to the present invention; Figure 9 is yet another example of a heat exchanger for use in a heat recovery system according to the present invention; Figures 1OA and lOB are respectively plan and cross-sectional views of a preferred heat exchanger for use in a heat recovery system according to the present invention; Figures hA is a plan view with sections separated of a modular heat exchanger according to another embodiment of the present invention; Figure lb B is, a sectional view along B-B of Figure 1 IA; Figure 11 C is a sectional view along A-A of Figure 11 A; Figure liD is a schematic view illustrating mains water flow through the joined sections of the heat exchanger shown in Figure hA; Figures l2A and l2B are schematic views of an alternative vertical heat exchangerfor use in a heat recovery system according to the present invention; Figures 13A and 13B illustrate one embodiment of a heat exchanger incorporating the alternative vertical heat exchanger schematically shown in Figures 12A and 12B; and Figures 14A and 14B are schematic diagrams illustrating modes of operation of a valve for controlling cold water feed flow during start up and established flow through the heat recovery system of the present invention.

DETAILED DESCRIPTION

The present invention provides a heat recovery system that is in direct contact with heated waste water thereby increasing the efficiency of the recovery due to there being minimal heat loss through heating of other component parts of the recovery system. This is achieved by forming the waste water receptacle itself at least partially of the heat exchanger whereby heated water has direct contact with the heat exchanger forming the receptacle. This provides clear advantages with regard to prior art devices that have metal or ceramic shower trays or other components that absorb a significant amount of the waste water heat prior to it reaching the heat exchanger that carries incoming cold water for pre-heating. The system according to the present invention is also low maintenance.

Figure 1 of the accompanying drawings illustrates a schematic diagram of a shower system fitted with a heat recovery system according to an embodiment of the present invention. An electric shower 2 comprises a shower tray 4 and shower pipe 6 leading to a shower head 8. An electric heater 10 heats up the incoming water so that it exits the shower head at a desired temperature, such as 40°C. The water falls on the shower tray at a temperature of approximately 36°C if the shower is occupied or 38°C if unoccupied.

Normally, this hot water simply runs down the shower drain and to the main grey water drainage system of the property resulting in a substantial loss of heat energy. In the present invention, the shower tray 4 is in the form of a heat exchanger comprising a series of adjoining and abutting pipes (not shown in Figure 1) through which incoming mains water is directed prior to delivery to the shower pipe 6. The incoming mains water is at a temperature of 10°C but as it passes through the pipes of the shower tray, hot waste water released from the shower head 8 lands on the heat exchanger and heats up the mains water. The waste water then exits the base of the shower tray at a much cooler temperature (around 10°C) with the preheated incoming water requiring less energy from the heater 10 to reach the desired showering temperature. A thermostat 12 may be provided to monitor the temperature of the incoming water to reduce the power input from the electric heater once a predetermined incoming water temperature is achieved. For example, one of the heating elements may be switched oft to reduce the power input required to heat the shower The heat exchanger of the present invention must be configured such that it is suitable for use as a shower tray or other water receptacle while allowing the incoming water flowing therethrough to make sufficient contact with the hot waste water to ensure satisfactory transfer of the heat energy to pre-heat the incoming water. For example, in one embodiment of a heat recovery system of the present invention the shower tray comprises a flattened tube or pipe, preferably made out of copper or aluminium, which repeatedly sinuates from one side of the shower tray to the other. Adjacent stretches of the pipe are in contact with each other to form a flat solid tray whereby an individual may be supported on the tray and waste water from the shower head may be received and flow along the tray to the outlet port.

Figures 2 to 7 illustrate a preferred embodiment of a heat recovery system according to the present invention. A shower tray 4 comprises a series of parallel and contacting pipes 20 in fluid communication with both an inlet pipe 22 for delivering incoming mains water to the pipes and an outlet pipe 24 for delivering pre-heated water that has travelled through the pipes 20 away from the tray 4 to the shower head. The pipes 20 are preferably welded together. The tray is installed such that a gentle gradient (for example, 1mm in 286mm fall) directs water to the shower drain 30 connected to trap 32 for delivering waste shower water that has travelled over the tray to the drainage pipe 34 connected to the mains grey water drainage system. The shower tray comprising the heat exchanger is embedded in an insulating material 40 which may also act as a support for the tray, such as an acrylic capped high density foamed resin.

As shown in detail in Figure 5, the parallel pipes are a series of flattened, non-circular pipes to enable sufficient heat transfer from water that falls onto the upper surFace of the pipes to the incoming water flowing through the pipes. The pipes also provide a substantially flat surface for an individual using the shower to stand on. However, the inlet and/or outlet pipes 22, 24 are substantially circular in cross-section (see Figures 3 and 7). Such an arrangement has been found to reduce pooling of the water and allow satisfactory heat exchange with the heated shower water that falls onto the tray. Each flattened pipe has a small internal cavity that allows water travelling through the pipe to be sufficiently heated during the minimal contact time with the waste shower water landing on the surface of the tray. However, it is important that the dimensions of the pipes are such as to maintain flow through the tray, ideally maintaining the flow at the rate that it enters the tray.

It is to be appreciated that alternative configurations may be provided for the shower tray that forms the heat exchanger but it is essential that the arrangement enables a sufficiently thin layer of shower water to travel across the surface of the tray with minimal pooling and that the pipes of the heat exchanger are such as to allow sufficient incoming water to be heated through heat exchange with the shower water. It is also important that the pipes are arranged such as to allow direct contact with the shower water For example, in an alternative embodiment, the pipes may be embedded into a shower tray such that the upper surface of the pipes can make direct contact with the shower water, with the remainder of the tray being of a standard shower tray material, such as stone resin or acrylic.

Figure 8 of the accompanying drawings illustrates another embodiment of a shower tray according to the present invention wherein the tray that comprises the heat exchanger is a flattened continuous pipe, each section of which is in the general shape of a S. This type of heat exchanger may be cast from a single sheet of metal, such as copper or aluminium.

Again, the actual conduits running throughout the tray (or a region of the tray) are of a small internal volume with the upper surface forming a substantially flat surface.

Figure 9 illustrates yet a further embodiment of a tray comprising a heat exchanger This embodiment may be particularly suitable for mass production. The tray 40 comprises an upper substantially flat sheet 42 and a lower undulating, or corrugated, sheet 44 comprising a series of peaks 46 and troughs 48. Preferably, the upper sheet is connected to the lower sheet at the peaks of the undulations with the troughs of the lower sheet defining the heat exchange pipes. In a preferred embodiment, the pipes are V-shaped in cross-section to maximize the amount of water in the pipe that contacts upper sheet comprising the heat transfer surface. Again each end of each pipe is connected to an input pipe and an output pipe (not shown). The inner dimensions of the pipe are optimized to minimize any change in flow of water from the input to the output pipe.

In this respect, the total cross-sectional area of the pipes that make up the heat exchange region of the receptacle should preferably be no less than the cross-sectional area of the mains input water pipe, thereby ensuring that the flow of water through the heat exchange region of the receptacle is maintained. A reduced cross-sectional area hinders the flow of water through the heat exchange region. For example, with a 15mm diameter input pipe, the total cross-sectional area of the pipes should be a minimum of 176.71mm2.

Alternatively, with a larger 22mm diameter input pipe, the total cross-sectional area of the pipes of the heat exchanger should be at least 380.13mm2.

The overall size of the actual shower tray may differ to the heat exchange part of the tray, i.e., the heat exchanger does not have to be co-terminus with the shower tray. The heat exchanger may be set within a larger tray but it is crucial that the top surface of the heat exchanger is exposed for direct contact with water falling from the shower head. It is to be appreciated that a thin coating of material may be provided over the surface of the shower tray (for example, being a maximum of 5mm, preferably less than 2mm.). Such a thin coating will have little impact of the amount of heat transferred from the hot water to the incoming mains water.

The relative dimension of the conduits within the heat exchanger, the overall surface area of the heat exchanger and the shower output are important for providing a satisfactory flow of water through the heat exchanger so that satisfactory heat recovery is provided by the system. For example, a larger heat exchanging area (i.e. larger tray) will provide greater heat transfer than a smaller area (i.e. smaller tray). A larger tray could be used with a shower system with higher flow rates and a smaller tray could be used with a shower system with lower flow rates, thereby ensuring that the waste water has sufficient time in contact with the heat exchanger The gradient of the shower tray is also important in ensuring that the shower water has sufficient contact time to exchange heat across the heat exchanger while preventing any pooling of the water which could create hot spots and reduce the efficiency of the heat transfer. The gradient will depend upon the total area of the shower tray but is preferably less than 20 degrees off horizontal. Additional features may be provided on or within the tray to minimize pooling, such a raised sides surrounding the centre of the shower tray and/or one or more dams that encourage water flow in the desired direction.

Figures IOA and lOB illustrate a preferred embodiment of the heat exchanger shower receptacle for use with the present invention. The receptacle 4 comprising the shower tray forms the heat exchanger and is made up of three sheets of conductive material, an upper sheet 50(omitted in Figure 1OA to show middle sheet), a lower sheet 70 with a middle sheet 60 provided with piercings or etchings to form pipes 62 running through the receptacle from an input end to an output end. A series of 3 S-plan parallel pipes 62 are provided running from the input end to the output end. The upper sheet is provided with an opening extending over the input ends of all three pipes to provide an input port for receiving mains water and the lower sheet is provided with an opening over the output ends of all three pipes to provide an output port for the heated mains water that is then delivered to the shower head. The pipes are preferably anodised aluminium but other conductive materials may be used, such as copper In this embodiment, the mains input pipe has a diameter of 15mm and each of the three subsidiary pipes 62 has an internal depth Di of 1.2mm and an internal width WI of 40mm.

This arrangement has been found to provide efficient flow of water through the heat exchanger at a satisfactory rate for heating by the waste heated shower water that falls onto the upper sheet 50 of the receptacle. However, it is to be appreciated that these parameters may be scaled up or down as appropriate, depending upon the diameter of the input pipe, the number of subsidiary pipes and the length of the fall of the shower tray.

However, as previously noted, the cumulative internal cross-sectional area of the subsidiary pipes should be substantially the same as the internal cross-sectional area of the mains input pipe but with the heat exchange contacting surface area maximized.

The arrangement comprising three planar flat sheets of material provides a suitable surface for fitting as an entire waste water receptacle, particularly a shower tray, with the whole receptacle acting as a conductor to increase the efficiency of heat transfer from the waste water landing on the upper sheet 50. The arrangement is such that hot waste water falling on the upper layer directly transfers energy to the incoming mains water that travels through the flattened pipes formed between the upper and lower sheets, significantly increasing the efficiency of heat transfer. The upper sheet may be provided with ribbing to aid flow of water across the surface of the receptacle. A mat may be provided on top of the upper sheet, such as one having an anti-slip surface, but it is to be appreciated that this would result in a slight reduction in the efficiency of the heat transfer. Again ribbing may be provided on the mat to assist in flow of the waste water across the tray to the waste water outlet.

This arrangement may also be provided in the form of a large tile to enable the heat recovery system to be provided within a wet room. Preferably, the heat exchanging tile is formed by a three pipe S-plan arrangement as described in relation to Figures IOA and lOB, albeit alternative arrangements may be used. An insulating layer may be secured to the floor of the wet room to provide a level surface and to minimize heat loss from the heat exchanger The heat exchanging tile is then placed over the insulating layer and the necessary gradient then pressed into the tile. Optionally a mat may be included over the tile, preferably having one or more ribs to direct water flow of the heat exchanger Preferably, a single rib is provided on the mat (or tile surface).

The heat recovery system of the present invention also provides an additional advantage in that after shutting off of the shower (or other water system), the receptacle remains heated and acts as a radiator to warm the surrounding area.

It is to be appreciated that the heat exchanger of the present invention may be formed by a variety of manufacturing methods, such as by bonding separate pieces together (in which case a conductive adhesive must be used), extrusion methods, one-piece fabrication and hydroforming.

Figures hA to liD illustrate another embodiment of a heat exchanger for use in a heat recovery system of the present invention. The heat exchanger is provided in sections which may be joined together. An input manifold 70 directs water into a plurality of adjoining parallel flattened pipes 72 leading to an opposing manifold 74 that passes the water to another manifold 80 that serves to change the direction of flow to an adjacent series of adjoining parallel flattened pipes 82 leading to another manifold 84 which may lead to the exit or to another section, as appropriate (arrows in pipes 72, 82 of Figure liD indicate direction of flow). Multiple sections may be fastened together using suitable fastening means 90 to provide a receptacle of a desired length.

Figures 12A to 13E illustrate another example of a heat exchanger according to the present invention wherein the plurality of pipes are arranged vertically as well as horizontally. This enables the horizontal area of the tray to be reduced by increasing the vertical area of the heat exchanger and is particularly applicable for installation in a shower waste. A series of stacked horizontal flattened pipes 102, 104, 106 are provided in a staggered arrangement to provide a vertical conduit 90 for the flow of waste water.

Figure 12A shows schematically the flow of waste water around the stacked flattened pipes 102, 104, 106 and Figure 12B illustrates the flow of incoming water through the pipes.

A detailed representation of a shower waste incorporating the heat exchanger of Figures 12 A and 12 B is shown in Figures 1 3A to 1 3E wherein identical features are provided with the same reference numerals. This embodiment is particularly suitable for installation in a shower waste wherein the waste water exits through a central outlet pipe 110.

The heat recovery system of the present invention is particularly applicable for electric showers wherein the electric energy input can be automatically reduced once the incoming water is sufficiently pre-heated by waste heat water from an earlier shower operation. However, the system may also be applied to other types of showers, such as boiler-fed showers.

As mentioned above in relation to Figure 1, a thermostat 12 may be provided to monitor the temperature of the incoming water to reduce the power input from the electric heater once a predetermined incoming water temperature is achieved. For example, one of the heating elements may be switched off to reduce the power input required to heat the shower However, in a preferred example three or more smaller heating elements (3.75 kW -5.2 kW per element in place of the standard 7.5 -10.5 kW heating elements) are used to enable the power input into the shower to be adjusted in smaller increments. A transistor or other appropriate means, such as TRIACs or microprocessor, may be used to adjust the amount of heat provided by the elements dependent upon the temperature of the incoming water that has passed through the heat exchanging shower tray. The use of multiple heating elements with a lower power output allows for more accurate adjustment of the power output and reduces the noise caused by switching of the elements.

Furthermore, the heating elements may also be mounted in a heat sink whereby the incoming water is also heated via this waste heat also, thereby further improving the efficiency of the system.

Additionally, a valve system may be included to vary the amount of hot water added to the incoming water. This is the reverse of a conventional mixer shower that introduces hot water and adds cold water to the incoming water. Figures 14A and 14B illustrate an example of such a valve mechanism. During start up (Figure 14A) the mixer valve 100 is closed so that minimal water from the heat exchanger passes to the shower head to allow for effective heating of the shower water prior to its release from the shower head. As the water from the heat exchanger becomes hotter, the mixer valve 100 opens to allow more water to flow to the shower from the heat exchanger (see Figure 14B, wherein additional arrows indicate greater water flow Optionally, a pump may also be employed to aid sufficient flow of water through the system.

Furthermore, the heat recovery system of the present invention may be adapted for other types of grey water systems to recover heat from the waste water. For example, a part of a sink basin may be formed of a heat exchanger that can directly contact hot water within the sink and transfer this heat to incoming cold water that passes through the pipes of the heat exchanger so that less hot water needs to be fed to a mixer tap that feeds the sink.

A similar type of arrangement may also be applied to a bath. The heated incoming water that has passed through the heat exchanger may be directed to any appropriate facility in a property where hot water is desired.

The amount of heat recovered by the system may be monitored by suitable means to inform the user of energy savings being made as a result of using the system. Such a monitoring system may also serve as a diagnostic tool to enable maintenance of the system when required.

Claims

CLAIMS.1. A heat recovery system for the recovery of heat from waste water, the system comprising a waste water receptacle for receiving waste water, the receptacle being adapted for connection to a waste water drainage pipe, the waste water receptacle consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water, and an output port for removing water from the exchanger wherein the mains conduit is in fluid communication with at least two subsidiary conduits extending at least partially between the input and output ports, the at least two subsidiary conduits having a cumulative internal cross-sectional area substantially equal to or greater than that of the mains conduit but having a greater heat exchange contacting surFace area thereto whereby heat energy from the waste water received on the receptacle transfers heat energy directly to the incoming water in the at least one conduit.
2. A heat recovery system as claimed in claim I wherein the waste water receptacle is selected from the group consisting of a shower tray, bath or sink.
3. A heat recovery system as claimed in claim I or claim 2 wherein the heat exchanger comprises an entire upper surFace of the waste water receptacle, more preferably wherein the heat exchanger comprises the waste water receptacle in its entirety.
4. A heat recovery system as claimed in claim 1 or claim 2 wherein the heat exchanger forms a part of the waste water receptacle, an upper surface of the heat exchanger being arranged for direct contact with the waste water.
5. A heat recovery system as claimed in any one of the preceding claims wherein the waste water receptacle comprises a plurality of substantially parallel and adjoining conduits or pipes, one end of each of the conduits being in fluid communication with a pipe or conduit that is in fluid communication with the input port and the opposite end of each conduit being in fluid communication with a pipe or conduit that is in fluid communication with the output port.
6. A heat recovery system as claimed in claim 5 wherein the parallel pipes that form the heat exchange region of the receptacle comprise non-circular pipes in cross-section.
7. A heat recovery system as claimed in claim 6 wherein the pipes that form the heat exchange region comprise flattened or oval-shaped pipes in cross-section.
8. A heat recovery system as claimed in claim 6 wherein the pipes that form the heat exchange region are substantially V-shaped in cross-section.
9. A heat recovery system as claimed in claim 8 wherein the heat exchange region comprises an upper substantially flat sheet connected to a lower undulating sheet defining the substantially V-shaped pipes therebetween.
10. A heat recovery system as claimed in any one of the preceding claims wherein the cumulative cross-sectional area of the pipes of the heat exchanger is substantially equal to the cross-sectional area of the mains conduit.
11. A heat recovery system as claimed in any one of the preceding claims wherein an upper surface of the waste water receptacle which receives the waste water includes a gentle gradient to direct waste water to the waste water drainage pipe.
12. A heat recovery system as claimed in any one of claims 1 to 4 wherein the heat exchanger is provided with multiple conduits in fluid communication, the conduits being provided by the inclusion of appropriate partitions within a single casing that has an input and output port.
13. A heat recovery system as claimed in claim 12 wherein the internal conduits provided by the pipes and/or partitions are of small cross-section and have a flattened upper surface.
14. A heat recovery system as claimed in claims 10 or 11 when dependant from any one of claims I to 4 wherein the heat exchanger comprises a series of at least three S-plan flattened pipes running substantially parallel to one another from the mains conduit to the outlet port.
15. A heat recovery system as claimed in claim 14 wherein the heat exchanger comprises three layers, the upper and lower layers each being formed of a solid conductive sheet to form the upper and lower surfaces of the heat exchanger pipes and the middle layer being relieved of material to provide the sides of the pipes or is formed as a single or two-piece pressing.
16. A heat recovery system as claimed in claim 14 or claim 15 wherein the input port and/or output port spans openings forming the entrance and/or exit of all of the pipes.
17. A heat recovery system as claimed in any one of the preceding claims wherein the heat exchange part of the waste water receptacle is formed of a conductive material to allow for an efficient transfer of heat from the waste water to the incoming water.
18. A heat recovery system as claimed in any one of the preceding claims further comprising an insulating layer provided beneath the heat exchanger
19. A heat recovery system as claimed in any one of the preceding claims wherein the heat exchanger is configured to form a floor tile structure.
20. A heat recovery system as claimed in any one of the preceding claims wherein the multiple conduits for passage of the mains water are stacked vertically in a staggered arrangement in addition to horizontally, whereby waste water is directed around the stacked conduits.
21.A waste water receptacle being adapted for connection to a waste water drainage pipe, the waste water receptacle consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water] an output port for removing water from the exchanger and multiple conduits between the input and output ports wherein the multiple conduits have a cumulative internal cross-sectional area substantially equal to or greater than, preferably substantially equal to, the mains conduit connectable to the input port but having a greater heat exchange contacting surface area thereto..
22. A waste water receptacle as claimed in claim 21 comprising a shower tray.
23. A shower system comprising a heater for increasing the temperature of incoming water, a shower head for the delivery of heated water to a shower tray, the shower tray being adapted for connection to a waste water drainage pipe, the shower tray consisting at least partially of a heat exchanger comprising an input port connectable to a mains conduit for the flow of incoming water, an output port for removing water from the exchanger wherein the mains conduit is in fluid communication with at least two subsidiary conduits extending at least partially between the input and the output ports, the at least two subsidiary conduits having a cumulative internal cross-sectional area substantially equal to or greater than, preferably substantially equal to, that of the mains conduit but having a greater heat exchange contacting surface thereto whereby heat energy from the waste shower water is received on the shower tray and transfers heat energy directly to incoming water in the conduits.
24. A shower system as claimed in claim 23 wherein the output port carrying the preheated water is connected to the shower head.
25. A shower system as claimed in claim 23 or claim 24 wherein a thermostat monitors the temperature of the preheated water and reduces the power input into the heater upon detecting a predetermined water temperature.
26. A shower system as claimed in claim 25 wherein the shower system is heated by multiple heating elements, each element being independently operable depending upon the temperature of the input water
27. A shower system as claimed in any one of claims 23 to 26 further comprising a valve mechanism for adjusting the amount of hot water added to the input water following its passage through the heat exchanger
28. A shower system as claimed in any one of claims 23 to 27 further comprising a filter and/or cleaning agent within the heat exchanger
29. A shower system as claimed in in any one of claims 23 to 28 further comprising a trap between the shower tray and waste water drainage pipe.