Patent Description:
In the past, devices for exchanging or recapturing heat between two fluids have been well known for many years and widely used throughout various industries and in commercial and residential environments. In general, these type of fluid heat exchanging or recovery devices involve two fluids passing in separate conduits and having at least one surface in thermal contract therebetween to exchange heat between the respective fluids without intermixing the fluids.

There is also need for practical, efficient and economical heat exchange units which meet applicable plumbing standards and building codes in order to be legally permitted and widely installed. Many such plumbing standards and building codes require some type of mechanism to prevent intermixing of the fluids and/or detect potential leaks.

Thus, there is a need for an economical and efficient heat exchanging device which permits the exchange of heat between fluids, such as waste water and clean water, which can also detect a potential breach by either of the two fluids before an undesirable and potentially unsanitary mixing of the fluids.

Accordingly, it is an object of this invention to at least partially overcome some of the disadvantages of the prior art. Also, it is an object of this invention to provide an improved type of heat exchange device to recover heat from waste water. In one aspect, it is also an object of the invention to provide an improved type of heat exchange device which can exchange heat between fluids and detect potential breaches by the fluids.

Accordingly, in one aspect of the present invention, there is provided a heat exchanging device according to claim <NUM>.

Accordingly, in one aspect of the present invention, there is provided a heat exchange device having a first conduit including a double wall construction having an inner wall and an outer wall, the outer wall positioned concentrically radially outwardly from the inner wall and fixed thereto defining a plurality of leak channels therebetween. In a preferred embodiment, the double wall construction of the first conduit may be accomplished with a copper "pipe in pipe" design. The plurality of leak channels may be formed by creating grooves on the outside surface of the inner wall, and/or, the inside surface of the outer wall. In this way, fluid which may have breached the inner wall or outer wall will be conveyed through the leak channels and be detected before breaching the other wall and causing contamination of the fluids.

In a further advantage of the present invention, the heat exchange device acts as a heat recovery device and is oriented vertically, such that the first fluid, which may generally be warm drain water or grey water, is conveyed through gravity flow. Similarly, any leak fluid in one or more of the plurality of leak channels, whether from the first fluid or the second fluid, may also be conveyed through gravity flow and be detected. This involves a simpler and more robust design which does not rely on external power sources or water pressure to detect leaks. In particular, by having any leak fluid conveyed in the leak channels though gravity flow, a potential leak may be detected even if other utilities, such as electrical power or water pressure, are non-operational.

In a further preferred embodiment, a baffle is used to create turbulence inside the heat exchange unit. Typically, the baffle would be used for the clean water which is under pressure in the second conduit. The baffle increases the turbulent flow, and therefore heat exchange, between the first fluid and the second fluid across the double walled first conduit.

O-rings may be used for positioning and sealing the second conduit with respect to the first conduit. This permits efficient retrofitting of the heat exchanging device to existing drain water lines. Furthermore, this avoids the need for manual welding operations which can increase the cost of installation.

A further advantage of the present invention is that the double wall construction, and/or, at least one wall, of the first conduit may extend axially beyond the second conduit, to permit simple coupling to existing drain pipes. This permits mechanical joint couplings to be used rather than more complicated and expensive couplings. Furthermore, the inner wall of the double wall first conduit may be similar in construction to a drain waste vent (dwv) copper pipe, meaning that it has a similar diameter and structure, to decrease any interference on the flow of the waste fluid, which in a preferred embodiment is gravity fed drain water.

A further advantage of the present invention is that the second fluid, which in a preferred embodiment is clean or fresh water under pressure, may travel in an upward direction from the lower end of the device to the upper end of the device such that the flow of the second fluid or fresh water is in an opposite direction to the downward gravity flow direction of the first fluid or waste water. Having cross flow of the fluids may improve the heat transfer between the fluids.

An advantage of a further preferred embodiment of the invention involves tangential inlets and outlets for the second fluid, which is typically under pressure. This assists in maintaining the pressure in the second fluid while entering and exiting the second conduit to avoid excessive pressure loss in the system. Furthermore, the tangential inlet and outlet create a spiral path in the inlet and outlet cavities and the second conduit which improves the heat exchange.

In a further preferred embodiment, the second conduit is concentric with the first conduit and radially separated therefrom by a predetermined distance. The second conduit has an external tube which is preferably not highly heat conductive. In a preferred embodiment, the outer wall of the second conduit may be constructed of a plastic material, such as a polyvinyl chloride (PVC), which may be considered a thermally insulating material. The inner conduit and the leak channels preferably extends in a longitudinal direction a distance below the outer wall of the second conduit to permit any fluid in the leak channels to be detected. In a preferred embodiment, the leak channels extend axially beyond the second conduit such that the leak fluid may be detected.

Further aspects of the invention will become apparent upon reading the following detailed description and drawings, which illustrate the invention and preferred embodiments of the invention.

In the drawings, which illustrate embodiments of the invention:.

The present invention relates to a heat exchanging device which can exchange heat from a first fluid to a second fluid. In preferred embodiments, the heat exchanging device is used to exchange heat from a waste water fluid at a first inlet temperature to a fresh water fluid at a second inlet temperature, lower than the first temperature, thereby recovering heat from the waste water fluid before it is expelled from the plumbing system.

In a preferred embodiment, the heat exchanging device has a first conduit for conveying the first fluid, and, a second conduit, concentrically located about the first conduit, for conveying the second fluid between the outer surface of the first conduit and the inner surface of an external tube. The first conduit includes a double wall construction with an inner wall and an outer wall. The first fluid is in thermal contact with the second fluid through the double wall of the first conduit to transfer heat from the first fluid to the second fluid. The double wall construction of the first conduit ensures that there is no shared boundary between the first fluid and the second fluid, and in particular, between the waste water fluid and the fresh water fluid in this preferred embodiment.

To detect a potential breach between the first and second fluids, the first conduit has a plurality of leak channels between the outer wall and the inner wall. In a preferred embodiment, the leak channels extend axially beyond the second conduit so that the leak fluid may be detected. Leak fluid, constituting first fluid breaching the inner wall of the double wall first conduit and/or second fluid breaching the outer wall of the double wall first conduit will be conveyed in the leak channels to be detected.

A baffle system located in the second conduit promotes turbulent flow and therefore heat exchange between the first fluid and the second fluid. This may decrease the length of the heat exchanging device to obtain comparable heat transfer. In a preferred embodiment, the first end of the second conduit is in fluid communication with a fresh water inlet vortex inducer and the second end of the second conduit is in fluid communication with a fresh water outlet vortex reducer for streamlining the flow to decrease the pressure loss of the second fluid (which is preferably under pressure) as it enters and exits the second conduit. This may also facilitate the flow of the second fluid through the baffle system.

Preferred embodiments of the invention and its advantages can be understood by referring to the present drawings. In the present drawings, like numerals are used for like and corresponding parts of the accompanying drawings.

As shown in <FIG> and <FIG>, one embodiment of the present invention relates to a heat exchanging device, shown generally by reference numeral <NUM>. As shown in <FIG> and <FIG>, the device <NUM> comprises a first conduit, shown generally by reference numeral <NUM>, and a second conduit, shown generally by reference numeral <NUM>.

In a preferred embodiment, the first conduit <NUM> may convey a first fluid <NUM> in a first direction FD from a first end <NUM> to a second end <NUM>, longitudinally opposed from the first end <NUM>, of the conduit <NUM>. It is understood that in a preferred embodiment, the first fluid <NUM> may be waste water fluid W which is gravity fed through the conduit <NUM>. In this preferred embodiment, the first direction will be a first downward direction FD, as shown for instance in <FIG>, from a waste fluid inlet <NUM> at the first end <NUM> of the first conduit <NUM> to a waste fluid outlet <NUM> at the second end <NUM> of the first conduit <NUM>. Accordingly, in this preferred embodiment, the first end <NUM> will be at an upper or higher end than the opposed second end <NUM> which will be at a lower position than the first end <NUM> to facilitate the gravity flow. It is understood that other arrangements are possible where the first end <NUM> is opposed from the second end <NUM>, but not necessarily higher or lower.

The second conduit <NUM> (shown in <FIG>) may convey a second fluid <NUM> in a second direction FU as shown in <FIG>. The second direction FU, in a preferred embodiment, is preferably opposite to the first direction FD of the first fluid <NUM> to improve heat transfer from the first fluid <NUM> to the second fluid <NUM>. The second conduit <NUM> is defined by, at least a portion of, an outer surface <NUM> of an outer wall <NUM> of the conduit <NUM>, and an inner surface <NUM> of the external tube <NUM> which is concentrically radially outwardly fixed from the outer wall <NUM> of the first conduit <NUM> as shown for instance in <FIG>.

In a preferred embodiment, the second fluid <NUM> is fresh water fluid F conveyed under pressure in the second upward flow direction FU while it is in thermal contact with the first fluid <NUM>. In this preferred embodiment, the waste water fluid W is conveyed through gravity G in the first conduit <NUM> in the first downward direction FD opposite to the second upward direction FU of the fresh water fluid F to facilitate the transfer heat from the first fluid <NUM> to the second fluid <NUM> in this particular preferred embodiment being waste water fluid W and fresh water fluid F, respectively.

In a preferred embodiment, the first fluid <NUM> will generally be at a first inlet temperature T1i at the inlet <NUM> and at a first outlet temperature T1o at the outlet <NUM>, as shown in <FIG>. Similarly, in a preferred embodiment, the second fluid <NUM> will enter the device <NUM> at a second inlet temperature T2i, which will typically be lower than the first inlet temperature T1i of the first fluid <NUM>, and exit the device <NUM> at a second outlet temperature T2o which will typically be higher than the second inlet temperature T2i of the second fluid <NUM> representing the heat transferred from the first fluid <NUM> to the second fluid <NUM> through the device <NUM>. In this way, heat will be exchanged generally from the first fluid <NUM> to the second fluid <NUM> through the thermally conductive first conduit <NUM>. In a preferred embodiment, heat will be recovered from waste water fluid W at a first inlet temperature T1i to the colder fresh water fluid F at a second inlet temperature T2i which is lower than the first inlet temperature T1i of the waste water fluid W.

More preferably, the device <NUM> comprises a tangential fresh water inlet <NUM> in fluid communication with a fresh water inlet vortex inducer <NUM>, shown for instance in <FIG> and <FIG>, to receive the second fluid <NUM>, in a preferred embodiment fresh water F under pressure, substantially tangentially to an inlet fluid cavity <NUM> of the first water inlet vortex inducer <NUM> to streamline the flow of the fresh water F and decrease pressure loss. The fresh water inlet vortex inducer <NUM> is in communication with a first end <NUM> of the second conduit <NUM> for receiving the fresh water fluid F from the tangential fresh water inlet <NUM> and directing the fresh water fluid F to the second conduit <NUM>. Similarly, the device <NUM> preferably comprises a fresh water outlet vortex reducer <NUM> in fluid communication with a second end <NUM> of the second conduit <NUM>, the second end <NUM> being longitudinally opposed to the first end <NUM>, for expelling the fresh water fluid F substantially tangentially to an outlet fluid cavity <NUM> of the fresh water outlet vortex reducer <NUM>, through the tangential fresh water outlet <NUM> to decrease potential pressure loss, and also to decrease any potential spiral vortex flow of the fresh water fluid F in the second conduit <NUM>. The fresh water outlet vortex reducer <NUM> is in fluid communication with the tangential fresh water outlet <NUM> to expel the second fluid <NUM>, in a preferred embodiment fresh water fluid F, at the second outlet temperature T2o.

The first conduit <NUM> is preferably formed of a material having a relatively high degree of thermal conductivity in order to facilitate thermal contact of the second fluid <NUM> conveyed in the second conduit <NUM> and the first fluid <NUM> conveyed through the first conduit <NUM>. These materials could be most types of metals as is known in the art such as copper, copper alloy, or copper-plated aluminium or other materials with relatively high degree of thermal conductivity. Conversely, it is preferred if the external tube <NUM> is made of a material which preferably has a relatively low heat conductivity. For example, the external tube <NUM> and one or more of the fresh water inlet vortex inducer <NUM> and fresh water outlet vortex reducer <NUM> may be made of plastics, such as PVC or ABS, or other types of plastic materials to insulate the heat being transferred from the environment. Similarly, it is understood that the conduits <NUM>, <NUM> should also be manufactured from materials able to withstand the corresponding pressure, temperature and in some cases chemical properties of the fluids <NUM>, <NUM> that they are designed to carry.

In a further preferred embodiment, the first conduit <NUM> includes a double wall construction, shown generally by reference numeral <NUM>, with an inner wall <NUM> and an outer wall <NUM>. <FIG> illustrates the conduit <NUM> including the double wall construction <NUM> with a portion of the outer wall <NUM> removed for illustrative purposes. As illustrated in <FIG>, in a preferred embodiment, the first conduit <NUM> includes the double wall construction <NUM> with the outer wall <NUM> being positioned concentrically radially outwardly from the inner wall <NUM> and abutting thereto.

As also illustrated in <FIG>, the first conduit <NUM> preferably comprises a plurality of leak channels, shown generally by reference numeral <NUM>, which are defined by the inner wall <NUM> and the outer wall <NUM>. The leak channels <NUM> extend along the first conduit <NUM> in the first downward direction FD towards the lower end <NUM> of the first conduit <NUM>.

During operation, any of the first fluid <NUM> which may breach the inner wall <NUM> without necessarily breaching the outer wall <NUM> of the first conduit <NUM>, as well as any of the second fluid <NUM> which may breach the outer wall <NUM> without necessarily breaching the inner wall <NUM>, results in leak fluid <NUM> entering the plurality of leak channels <NUM>. It is understood the leak fluid <NUM> may constitute any of the first fluid <NUM> which has breached the inner wall <NUM> and/or any of the second fluid <NUM> which has breached the outer wall <NUM> of the first conduit <NUM>. The leak fluid <NUM> entering one or more of the plurality of leak channels <NUM> is conveyed axially along the first conduit <NUM> facilitating detection of the leak fluid <NUM> and indicating of a corresponding potential breach which may have caused the leak fluid <NUM>.

<FIG> illustrates the leak channels <NUM> being exposed at the second end <NUM> of the first conduit <NUM>. The plurality of leak channels <NUM> extend axially beyond the second conduit <NUM> to convey the leak fluid <NUM> outside of the device <NUM> so that the leak fluid <NUM>, indicative of a potential breach, may be detected. The leak fluid <NUM> is shown in <FIG> emanating from the leak channels <NUM> on the outer surface <NUM> of the inner wall <NUM> as the outer wall <NUM> has terminated exposing the leak channels <NUM> and permitting detection of the leak fluid <NUM>.

In a preferred embodiment, the outer wall <NUM> and the leak channels <NUM> will terminate axially beyond the second conduit <NUM>. This permits the leak fluid <NUM> to be conveyed beyond the second conduit <NUM> and be exposed for detection. This also permits the inner wall <NUM> to optionally continue axially beyond the second conduit <NUM> for connection to a plumbing system <NUM> to convey and expel the first fluid <NUM> which in a preferred embodiment is waste water fluid W.

Once the leak fluid <NUM> has been exposed or expelled from the leak channels <NUM>, the leak fluid <NUM> may be detected in a number of ways. For example, the leak fluid <NUM> may be detected visually as it may drip onto objects directly below the device <NUM>, including but not limited to a waste water pipe (not shown) of the plumbing system <NUM>. Alternatively, the leak fluid <NUM> may accumulate on the floor and become detectable by most leak detection devices (not shown) which may be commonly found and are known in the art. Such leak detection devices may alert a user by setting off a visual and/or audible alarm or other visual and audible effects. The leak detection devices could also trigger a shut off valve of the plumbing system <NUM> which automatically prevents any further leakage and/or potential contamination of the fresh water fluid F with waste water fluid W. In any event, detection of the leak fluid <NUM> indicates a potential breach of the first fluid <NUM> and the second fluid <NUM> in the device <NUM> such that it may be attended to and further investigated, and if necessary, corrected such as through maintenance or service of the device <NUM> or replacement of the device <NUM>.

In a preferred embodiment, the leak channels <NUM> are formed by a plurality of grooves, shown generally by reference numeral <NUM> in <FIG>, made on the outer surface <NUM> of the inner wall <NUM> and/or an inner surface <NUM> of the outer wall <NUM>. It is understood that the grooves <NUM> may be on one of, or both of, the outer surface <NUM> of the inner wall <NUM> and the inner surface <NUM> of the outer wall <NUM> provided the grooves <NUM> in this preferred embodiment is on at least one of the surfaces <NUM>,<NUM>. For economy of manufacture, in most cases, it is preferable if the grooves <NUM> are on the outer surface <NUM> of the inner wall <NUM>, but it is understood this is merely one preferred embodiment.

In a preferred embodiment, the grooves <NUM> have a depth of about one half (½) an average thickness T of the inner wall <NUM> or outer wall <NUM> depending upon which wall <NUM>, <NUM> (or both) the grooves <NUM> have been made. After the plurality of grooves <NUM> have been formed, the outer surface <NUM> of the inner wall <NUM> is fixed in abutting relation to an inner surface <NUM> of the outer wall <NUM> such that the grooves <NUM> define the plurality of leak channels <NUM> therebetween as illustrated in <FIG>. Preferably, the leak channels <NUM> extend longitudinally along the conduit <NUM> so that the leak fluid <NUM> will have a shortest distance possible to be exposed so that any leak fluid <NUM> may be detected.

In a preferred embodiment, the leak channels <NUM> are each spaced by less than <NUM> (<NUM> inches) and more preferably less than <NUM> (<NUM> inches) along the circumference C<NUM> of the first conduit <NUM>. Still more preferably, in cases where the diameter D<NUM> of the first conduit <NUM> is about <NUM> inches, there will be at least <NUM> and more likely <NUM> about leak channels <NUM> along the circumference C<NUM> of the conduit <NUM>. Experimentation has shown that having this ratio of leak channels <NUM> will maintain a minimum of <NUM> percent thermal contact surface to provide for heat transfer between the first fluid <NUM> and the second fluid <NUM>, while at the same time permitting a relatively large number of leak channels <NUM> along the circumference C<NUM> of the first conduit <NUM> to detect a breach of the first fluid <NUM> through the inner wall <NUM> or a breach of the second fluid <NUM> through the outer wall <NUM>.

The inner wall <NUM> may be preferably formed of a first metal inner pipe <NUM> and the outer wall <NUM> may be preferably formed of a second metal outer pipe <NUM>. In this preferred embodiment, the double wall construction <NUM> of the conduit <NUM> may be formed by locating the first metal inner pipe <NUM> within the second metal outer pipe <NUM> and evenly applying an expansion force (not shown) radially on the inner surface <NUM> of the first metal inner pipe <NUM> to radially stretch the first metal inner pipe <NUM> and the second metal outer pipe <NUM> forming a mechanical bond therebetween with the second metal outer pipe <NUM> positioned concentrically radially outwardly from the first metal inner pipe <NUM> and abutting thereto, defining the leak channels <NUM> therebetween.

In a further preferred embodiment, the first metal inner pipe <NUM> forming the inner wall <NUM> is a drain waste vent (DWV) copper pipe with the grooves <NUM> extending along the outer surface <NUM> thereof. In this way, the DWV copper pipe may be more easily installed into an existing plumbing system <NUM>. In this case, the second metal outer pipe <NUM> may be a standard Type L or light copper pipe.

In the preferred embodiment where the first fluid <NUM> is waste water fluid W and the first metal inner pipe <NUM> forming the inner wall <NUM> is a drain waste vent (DWV) copper pipe, it will generally have a diameter D<NUM> of <NUM> to <NUM> (<NUM> to <NUM> inches) and more likely <NUM> (<NUM> inches). In the case where the DWV pipe is <NUM> (<NUM> inches), the circumference C1 will be: <MAT>.

In this situation, if the leak channels <NUM> formed by the grooves <NUM> are spaced less than <NUM> (<NUM>. 2inches) along the circumference C<NUM> of the first conduit <NUM>, then this provides roughly the following number of grooves: <MAT>.

Accordingly, in this preferred embodiment, where the first metal inner pipe <NUM> is a DWV copper pipe of <NUM> inches diameter, there will be about <NUM> to <NUM> leak channels along the circumference C<NUM> for conveying leak fluid <NUM>. Experimentation has shown that leak channels of this type and having a depth of about <NUM> (<NUM> inches) representing one half (½) the thickness T of the DWV pipe, would present <NUM> to <NUM>% heat recovery from the waste water fluid W to the fresh water fluid F. Typically, the DWV pipe may have a diameter of <NUM> to <NUM> (<NUM> to <NUM> inches) and, extrapolating equations (<NUM>) and (<NUM>) above, there would be about <MAT> or <NUM> grooves <NUM> or leak channels <NUM> along the circumference C<NUM> per inch of diameter D<NUM> of the inner pipe <NUM>.

As discussed above, the second conduit <NUM> is defined by the outer surface <NUM> of the outer wall <NUM> of the first conduit <NUM> and an inner surface <NUM> of the external tube <NUM>. In a preferred embodiment, the external tube <NUM> of the second conduit <NUM> is fixed a predetermined distance PD from the outer wall <NUM> of the first conduit <NUM> and the external tube <NUM> has a substantially constant diameter D<NUM>, as shown in <FIG>. Preferably, the predetermined distance PD from the outer wall <NUM> of the first conduit <NUM> to the inner surface <NUM> of the external tube <NUM> is about equal to a diameter D<NUM> of the first conduit <NUM> shown in <FIG>. In this way, the thermal contact of the second fluid <NUM> with the first fluid <NUM> while the second fluid <NUM> is conveyed in the second conduit <NUM> and the first fluid <NUM> is conveyed in the first conduit <NUM> is facilitated.

In a preferred embodiment where the inner wall <NUM> of the first conduit <NUM> is formed by a first metal inner pipe <NUM> comprising a DWV pipe, the diameter D<NUM> will likely be <NUM> inches at least pursuant to most current North American Copper DWV Tube Standards for sewage applications. The inner diameter D<NUM> of the external tube <NUM> is determined based on the amount of fresh water fluid F needed to pass through the device <NUM> and its corresponding effect on pressure loss. For example, in a preferred embodiment, if the amount of fresh water fluid F required may be about <NUM> litres per minute, the diameter D<NUM> of the external tube <NUM> may be selected to have a maximum pressure loss within the device <NUM> of less than <NUM> KPA. It is understood, the smaller the diameter D<NUM>, the greater the thermal contact which may result, however the greater the corresponding pressure loss.

In a preferred embodiment, the inlet vortex inducer <NUM> and outlet vortex reducer <NUM> fix the external tube <NUM> at the predetermined distance PD to the first conduit <NUM>. The inlet vortex inducer <NUM> and outlet vortex reducer <NUM>, in a preferred embodiment, have a similar construction and can actually be reciprocal components, meaning that they are identically made but connected to the external tube <NUM> in different orientation in order to decrease cost of manufacture and inventory. Accordingly, while the inlet vortex inducer <NUM> and outlet vortex reducer <NUM> will be discussed below separately, it is understood that preferably their structure is substantially identical.

<FIG> and <FIG> illustrate the outlet vortex reducer <NUM> according to a preferred embodiment. <FIG> is an enlarged fragmentary view of the device <NUM> shown in <FIG> focusing on the second end <NUM> of the conduit <NUM> with a portion of the external tube <NUM> and fresh water outlet vortex reducer <NUM> removed for illustration purposes. <FIG> is a perspective view of the fresh water outlet vortex reducer <NUM> with a top portion and connection to the first conduit <NUM> removed to illustrate the internal outlet fluid cavity <NUM>. It is understood that the internal features of the outlet fluid cavity <NUM> are similar to the internal features of the inlet fluid cavity <NUM>. The inlet vortex inducer <NUM> is also shown in <FIG>, but not in cut out.

As illustrated in these figures, in a preferred embodiment, the inlet vortex inducer <NUM> and the outlet vortex reducer <NUM> each have a substantially cylindrical shape and extend axially at least along a portion of the first conduit <NUM>. The fresh water inlet vortex inducer <NUM> defines an inlet fluid cavity <NUM> in fluid communication with the first end <NUM> of the second conduit <NUM> and also with the tangential inlet <NUM>. As illustrated in <FIG> and <FIG>, the outlet vortex reducer <NUM> also has a substantially cylindrical shape defining an outlet fluid cavity <NUM> with the tangential outlet <NUM> extending substantially tangentially from the circumference CR of the outlet vortex reducer <NUM>.

In this way, the second fluid <NUM>, which in a preferred embodiment is the fresh water fluid F under pressure, may enter the fresh water tangential inlet <NUM> and be received within the inlet fluid cavity <NUM> which is in fluid communication with the tangential inlet <NUM>. The fresh water fluid F may then be directed by the inlet fluid cavity <NUM> to the first end <NUM> of the second conduit <NUM> from the fresh water tangential inlet <NUM>. As the fresh water tangential inlet <NUM> extends substantially tangentially from the circumference C<NUM> of the inlet fluid cavity <NUM> of the fresh water inlet vortex inducer <NUM>, the fresh water fluid F may be tangentially directed under pressure from the tangential fresh water inlet <NUM> to the first end <NUM> of the second conduit <NUM> formed by the inner surface <NUM> of the external tube <NUM> and the outer surface <NUM> of the outer wall <NUM> of the first conduit <NUM>. This provides a preferred streamline flow of the fresh water fluid F into the device <NUM> and more specifically in the second conduit <NUM>. This also facilitates the generation of a vortex or spiral path of the fresh water fluid F within the inlet fluid cavity <NUM> of the fresh water inlet vortex inducer <NUM> which promotes the transfer of heat. In this preferred embodiment, a portion of the first conduit <NUM> is axially coincident with the inlet fluid cavity <NUM> and the fresh water fluid F under pressure to facilitate heat transfer.

Similarly, at the second end <NUM> of the second conduit <NUM>, the fresh water outlet vortex reducer <NUM> having a substantially cylindrical shape and defining the outlet fluid cavity <NUM> is in fluid communication with the second end <NUM> of the second conduit <NUM> and receives the fresh water fluid F from the second end <NUM> of the second conduit <NUM> after it has come into thermal contact though the first conduit <NUM> conveying the waste water fluid W. The fresh water outlet vortex reducer <NUM> will then expel the fresh water fluid F substantially tangentially to the circumference CR of the outlet fluid cavity <NUM> to the fresh water outlet vortex reducer <NUM> and in so doing decrease the vortex spiral flow of the fresh water fluid F being expelled from the second end <NUM> of the second conduit <NUM> and provide streamline flow to decrease any potential loss of pressure.

The fresh water inlet vortex inducer <NUM> also includes a first connection <NUM> and a second connection <NUM> on opposite sides of the inlet fluid cavity <NUM>. Similarly, the fresh water outlet vortex reducer <NUM> includes a first connection <NUM> and a second connection <NUM> on opposite sides of the outlet fluid cavity <NUM>. As illustrated in <FIG> and <FIG>, the first connections <NUM>, <NUM> are adapted to connect the inlet vortex inducer <NUM> and outlet vortex reducer <NUM> to the external tube <NUM> at the first end <NUM> of the first conduit <NUM> and at the second end <NUM> of the second conduit <NUM>, respectively. The second connection <NUM>, <NUM> of the fresh water inlet vortex inducer <NUM> and fresh water outlet vortex reducer <NUM> are adapted to connect the fresh water inlet vortex inducer <NUM> and fresh water outlet vortex reducer <NUM>, respectively, to an exterior surface <NUM> of the outer wall <NUM> of the first conduit <NUM> axially near the waste water outlet <NUM> and the waste water inlet <NUM>, respectively. As indicated above, the inlet fluid cavity <NUM> and the outlet fluid cavity <NUM> extend longitudinally along at least a portion of the outer wall <NUM> of the first conduit <NUM> from their respective first connection <NUM>, <NUM> to their respective second connection <NUM>, <NUM> to further facilitate thermal contact and heat transfer from between the fluids <NUM>, <NUM>.

In a preferred embodiment, as also illustrated in the figures, the second connections <NUM>, <NUM> of the fresh water inlet vortex inducer <NUM> and fresh water outlet vortex reducer <NUM>, respectively, may also comprise O-rings, shown generally by reference numeral <NUM> for example in <FIG> and <FIG>. The O-rings <NUM> facilitate positioning and sealing of the vortex inducer <NUM> and the vortex reducer <NUM> and therefore the external tube <NUM> and the second conduit <NUM> with respect to the first conduit <NUM>. This permits efficient retro fitting of the heat exchanging device <NUM> to existing drain water lines. Furthermore, this avoids the need for manual welding operations for the device <NUM> which can increase the cost of installation. Furthermore, the inlet fluid cavity <NUM> and the outlet fluid cavity <NUM> preferably have a slanted surface leading towards their respective first connections <NUM>,<NUM>. This slanted surface assists in gradually directing the fresh water fluid F into the first end <NUM> and out of the second end <NUM>, respectively, of the second conduit <NUM>.

<FIG> is a schematic drawing of a portion of a plumbing system, shown generally by reference numeral <NUM>, including a hot water tank <NUM> to illustrate the connection of the heat exchanging device <NUM> to the plumbing system <NUM> according to one preferred embodiment of the present invention. As illustrated in <FIG>, a portion of the existing drain water vent pipe, shown partially by reference numeral <NUM>, is connected through a mechanical joint connection <NUM> to the first conduit <NUM> at the first end <NUM>. There is a corresponding connection back to the drain water vent pipe <NUM> of the system <NUM> at the second end <NUM> of the first conduit <NUM>. In a preferred embodiment where the first fluid <NUM> is waste water fluid W, it will enter through the existing DWV pipe <NUM> and exit through the continuation of the DWV pipe <NUM> at the second end <NUM> after being expelled from the waste water fluid outlet <NUM>. <FIG> illustrates a fragmentary view of the lower end <NUM> of the device <NUM> and the mechanical joint (MJ) coupling <NUM> between the first conduit <NUM>, (and in a preferred embodiment the inner wall <NUM> of the first conduit <NUM>) to the DWV drain pipe <NUM> of the plumbing system <NUM>.

Similarly, the tangential fresh water inlet <NUM> will receive the fresh water fluid F which will pass though the device <NUM> and exit through the fresh water outlet <NUM> where the fresh water fluid F is shown as continuing through the plumbing system <NUM> to the hot water tank <NUM>. It is understood that the second outlet temperature T2o will be higher than the second inlet temperature T2i representing the heat transferred from the waste water fluid W to the fresh water fluid F. This transfer of heat represents an effective cost savings because the hot water tank <NUM> would not need to heat the fresh water fluid F by that temperature difference. Similarly, if the device <NUM> is operational, it is likely that there is a user of the plumbing system <NUM> drawing fresh water fluid F from the hot water tank <NUM>. In other words, fresh water fluid F will be entering the tangential inlet <NUM> precisely because hot water is being used and therefore warmer waste water fluid W will be entering the drain water inlet <NUM>.

In a further preferred embodiment, the device <NUM> comprises a baffle system shown generally by reference numeral <NUM> in <FIG>, <FIG> and in enlarged and fragmentary views in <FIG>, <FIG>. The baffle system <NUM> is located within the second conduit <NUM> and extends from the fresh water inlet vortex inducer <NUM> (see <FIG> and <FIG>) to the fresh water outlet vortex reducer <NUM>. The baffle system <NUM> preferably has a plurality of interleaved cylindrical hoops <NUM> and longitudinal bars <NUM> forming a cylindrical mesh, shown generally by reference <NUM> in <FIG>. The cylindrical mesh <NUM> has a number of baffle channel slots <NUM> formed by the plurality of interleaved cylindrical hoops <NUM> and longitudinal bars <NUM> with the hoops <NUM> being alternatingly connected to a radial outer surface <NUM> and a radial inner surface <NUM> of the longitudinal bars <NUM> as shown in <FIG>. This forms a zig zag flow path, shown generally by reference numeral Z in <FIG>, extending longitudinally within the second conduit <NUM> from the first end <NUM> to the second end <NUM> and between the outer surface <NUM> of the outer wall <NUM> of the first conduit <NUM> and the inner surface <NUM> of the external tube <NUM>.

<FIG> illustrates a top view of the baffle system <NUM> according to one preferred embodiment and <FIG> shows a partial enlarged side view of a few baffle channel slots <NUM> of the baffle system <NUM>. The baffle channel slots <NUM> are preferably about <NUM> to <NUM> (<NUM> inches to <NUM> inches) in length and may have a width of <NUM> to <NUM> (<NUM> inches to <NUM> inches). Preferably, the slots <NUM> have a width that is about twice the width of the hoops <NUM> which is about <NUM> to <NUM> (<NUM> to <NUM> inches). This facilitates the zig zag flow Z of the second fluid <NUM>.

As illustrated in <FIG>, the slots <NUM> are preferably separated by an angle α which can be <NUM> degrees to <NUM> degrees and more preferably <NUM> degrees. This permits about <NUM> baffle channel slots <NUM> to be oriented about the mesh <NUM> to facilitate the zig-zag Z flow path and corresponding heat transfer from the first fluid <NUM> to the second fluid <NUM> through the double wall <NUM> of the first conduit <NUM>. In particular, the use of the baffle system <NUM> increases the heat transfer between the first fluid <NUM> and the second fluid <NUM> over the same longitudinal length of the device <NUM>. In this way, the overall longitudinal length of the device <NUM> may be lessened with the use of a baffle system <NUM> as illustrated and described herein.

Claim 1:
A heat exchanging device for exchanging heat from a first fluid to a second fluid, said heat exchange device comprising:
a first conduit for conveying the first fluid in a first flow direction, said first conduit including a double wall construction with an inner wall and outer wall, said outer wall positioned concentrically radially outwardly from the inner wall and fixed thereto defining a plurality of leak channels there between;
a second conduit for conveying the second fluid in a second flow direction, said second conduit including at least a portion of an outer surface of the outer wall of the first conduit providing thermal contact between the second fluid in the second conduit and the first fluid in the first conduit to exchange heat between the first fluid in the first conduit and the second fluid in the second conduit;
the heat exchange device being characterized by said channels extending longitudinally along the first conduit in the first flow direction and by one or more of the plurality of leak channels extending beyond the second conduit so that in case of the first fluid breaching the inner wall without necessarily breaching the outer wall, and, the second fluid breaching the outer wall without necessarily breaching the inner wall, results in leak fluid, constituted by any first fluid that has breached the inner wall, or, any second fluid that has breached the outer wall, entering one or more of the plurality of leak channels, said leak fluid will be conveyed axially along the first conduit in said one or more of the plurality of leak channels axially beyond the second conduit to facilitate detection.