Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
  • F24D17/00—Domestic hot-water supply systems
  • F24D17/0005—Domestic hot-water supply systems using recuperation of waste heat
• • E—FIXED CONSTRUCTIONS
  • E03—WATER SUPPLY; SEWERAGE
  • E03C—DOMESTIC PLUMBING INSTALLATIONS FOR FRESH WATER OR WASTE WATER; SINKS
  • E03C1/00—Domestic plumbing installations for fresh water or waste water; Sinks
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
  • F28D21/0001—Recuperative heat exchangers
  • F28D21/0012—Recuperative heat exchangers the heat being recuperated from waste water or from condensates
• • E—FIXED CONSTRUCTIONS
  • E03—WATER SUPPLY; SEWERAGE
  • E03C—DOMESTIC PLUMBING INSTALLATIONS FOR FRESH WATER OR WASTE WATER; SINKS
  • E03C1/00—Domestic plumbing installations for fresh water or waste water; Sinks
  • E03C2001/005—Installations allowing recovery of heat from waste water for warming up fresh water
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
  • Y02B30/18—Domestic hot-water supply systems using recuperated or waste heat
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
  • Y02B30/56—Heat recovery units

Definitions

• This invention relates to a drain water heat recovery device comprising a counterflow, tube heat exchanger enclosed by a platform and a base section.
• the goal of drain water heat recovery is to reduce the costs of supplying hot or warm water to the home either via heating of the cold water just before entering the hot water tank (centralized), or just before being used by an appliance, shower, etc. (localized). This is done by recovering heat energy from the drain using a heat exchanger.
• hot and cold water are typically mixed to obtain a desired temperature and flow rate in some type of blending or mixing valve.
• Many modern blending valves used in showers and bath stalls are temperature-regulated such that a constant output temperature is achieved despite fluctuations in the cold or hot water supply lines. Therefore preheating the cold water supply will equate to less hot water needed to maintain a given outlet temperature and flow rate.
• waste water recovery heat exchangers will simply be called heat exchangers herein.
• a Heat Exchanging Mat has been patented (US 4821793) which lies over the existing bathtub (or shower) floor. Drain water is trapped between the mat and the bathtub (or shower stall) surface and is guided through channels before it reaches the drain. No retaining wall keeps the drain water from spilling over the edge, since the existing bathtub prevents water from escaping already.
• the solution has very little plumbing or installation work required. This known prior art is poor in the aspect that not all wasted water will make contact with entire heat exchange surface and also the mat gets in the way for those who sit or lie in the bath.
• a Platform Surface Heat exchanger has been patented which lies over the existing shower floor. Drain water flows towards the center of horizontal metal plate (forming the platform). A coil/spiral of cold water pipe is bonded to the lower surface. A retaining wall keeps the drain water from spilling over the edge, and an outer housing encapsulates the platform. The platform can be removed for cleaning if necessary though it is not likely required since water does not enter the inside of the device. The solution has very little plumbing or installation work required. This known prior art is poor in the aspect that drain water does not stay in contact with coil/spiral for a suitable length of time. Flow is likely laminar, not enough heat exchange area. Water will likely not come in contact with entire surface and concerns about getting cold feet while showering.
• Basin Heat Exchangers have been patented which lie over the existing shower floor. Examples are GB 2420973 and FR 2868796. Drain water collects on the platform which has retaining walls to prevent overspill. In GB 2420973, drain water is channeled horizontally and then downwards into a chamber called the basin where water collects and must pass through a series of channels while exchanging heat with the submerged tube and then overflows past a dam into the second drain, hi FR 2868796 drain water collects in a bowl where the submerged tube is wrapped in a coil. In both examples, water then flows towards the final drain.
• the solutions have some plumbing and installation work required.
• GB 2835785 describes an Under Bath Tub Heat Exchanger, which exchanger is located under an existing bathtub.
• the inventor limits his claims only for application where the heat exchanger is used to preheat cold water entering an electric "heat-on-demand" or “combi-boiler” type of system, not for use in installations which have a centralized hot water heater. Regardless, this is still a viable alternative for preheating cold water in a typical installation as well. Drain water leaves the bathtub and enters a canister or shell inside of which a coil of cold water picks up the heat. Some plumbing work is required, probably best handled by a professional. This known prior art is poor in the aspect that the design is complex and therefore rather expensive.
• AU2004212549 describes a Drain Pipe Coil Heat Exchanger which fits into or below the floor. Drain water passes through a metal drain section which is wrapped in a coil of cold water pipe. The two pipes are bonded together to increase the heat transfer rate. If installed locally, (near the shower or bathtub) the solution requires extensive plumbing work and possibly removal of a section of floor or wall in order to install. A professional would be needed. If installed centrally, a considerable length of piping would likely be needed depending on how far away the main drain is from the cold water pipes entering the home. This known prior art is poor in the aspect that the unit itself is entirely copper and the installation costs can be large.
• D 0.02 m diameter on the inside cold water tube
• A is the 1 m 2 from above.
• drain water will tend to back up into the tray if the drain length is too long. This is because friction losses in the drain channel will need to be overcome by a certain pressure. The longer the drain channel, the higher this pressure will need to be in order to meet the flow requirements. Since the drain water is open to the atmosphere, the only source of pressure to force the drain water along is head. The head is the difference in water level between the upstream and downstream water. If the head is insufficient, the water will back up causing the water level to rise until the head is sufficient to drive the flow along the channel. This problem is also addressed in the preferred embodiment by offering an overflow path to the drain water.
• FIGS. 5A, 5B, 6 show different views of a preferred embodiment of the invention
• Fig. 7 shows a further embodiment
• Fig. 8 shows a number of different embodiments of tubes according to the invention
• FIGS. 9 A, 9B show a further embodiment according to the invention
• Fig. 10 shows different embodiments of sluices for self drainage
• a Multi-Purpose Heat Exchanger has been envisioned, in accordance with claim 1, which can be installed in one of many places. It can be installed in a shower either above the floor or below it. It can also be installed under a bathtub. It can also be installed in the ceiling of a room below the bathroom if this is a more suitable location. It may even be installed in a centralized location in the cellar for example.
• the aim of the preferred embodiment is to be commercially viable to as many customers as possible.
• the key factors have been identified as
• the adaptability of the embodiment should attract a wider range of buyers, since the solution can be adapted to the specific needs of each customer, and can be re-installed as the customer's preferences or economic situation changes. It can be installed in any of the following locations: • On the shower floor, or on top of an existing shower tray (Figure 1)
• the heat exchanger will maximize efficiency:
• the platform will have surface channels or grooves (Figs. 5 A, 11) to minimize the free surface area where evaporation losses remove energy before the water even makes it to the first drain intake.
• the heat exchanger base (Fig.5B) may be insulated with a polystyrene (or equivalent) foam
• a cross linked polyethylene PEX tube length would need to be approximately 21 m in length to achieve a 1.25 square meter heat transfer area.
• the actual tube length may in fact fall anywhere between 15 m and 100 m with the specified diameter of between 12 and 50 mm.
• the wall thickness is determined by the tube diameter and the rated operating pressure.
• a 20 mm tube has a 2 mm wall thickness on standard domestic PEX tubes (even thinner for copper). However, if possible, the wall thickness would be preferably even thinner to increase the heat transfer rate. o It should be noted that using the PEX plastic instead of copper only marginally decreases the heat transfer rate, while significantly reducing costs. Because of the large cost reduction, a greater amount of tubing can be used, thereby surpassing the original efficiency, with a reduced cost, o It should also be noted that this length of tube is difficult to fit into a shower tray with approximate dimensions of (65 cm x 65 cm x 15 cm), mainly because the 20 mm diam. tubes do not have a tight bend radius
• FIG. 5B A concentric, overlapping coil/spiral arrangement, (Figs. 5B, 6) or alternately a flattened helix arrangement (Figs. 9 A, 9B) are considered ideal to fit as much tube as possible into the shower tray. Industrial-scale applications would require larger tubes, and a larger box, of course.
• Clogging The heat exchanger designs against clogging by allowing an internal overflow path, whereby drain water can simply move over the baffles (Fig. 6) and bypass the clog.
• the internal drainage path will be large to help prevent clogging from occurring in the first place. The reason for this is to prevent backup into the platform so that the end user is not standing in a puddle.
• Fouling/Cleaning The heat exchanger can be easily cleaned by lifting off the drain trap/screen and inserting a 2 foot long coil brush into the drain and simply scrub away any deposits. However, prevention is best. This is why the Drain intake is protected with a fine screen ( Figure 5A, 6, 9B item 5)
• the actual costs must be minimized. This includes installation costs as well as manufacturing costs.
• the energy savings earned from using the heat exchanger should then save money for the users and the heat exchanger would eventually "pay for itself in a short number of years.
• the key factor to achieving this aim is not efficiency but rather the ratio of efficiency with respect to the overall product cost.
• the efficiency to cost ratio must be maximized. Manufacturing costs of the heat exchanger will be minimized.
• the heat exchanging surface will likely be a plastic tube, certified for about 10 bar of pressure. This would preferably be a cross-linked Polyethylene (PEX) plastic commonly used for domestic water lines.
• the diameter could be between 10 and 40 mm, but preferably either 20 or 22 mm because these are common standards and because this size is large enough so as to not introduce too much pressure drop, but can still be bent easily enough to fit a 21 -m length inside the embodiment.
• the tube dimensions can be approximately 10 to 12 mm in diameter (approximately half the diameter) but having double the length (40 - 45 m). This has the effect that the tubes contain approximately half the volume of water as the preferred embodiment, which means the water can heat up more quickly, and that the tubes are easier to bend, which may mean that even more tube can be fit into the embodiment (perhaps up to 100 m).
• the base, platform and outer walls will preferably be molded from plastic as well, but may also be formed from a fiberglass-epoxy composite, or acrylic.
• the Installation costs of the heat exchanger will be minimized.
• the product will preferably be packaged with some tools/accessories to aid in installation and cleaning such as simple punch out drain intake and outlets, bulkhead caps to plug punched out holes, adjustable feet to level the heat exchanger, a specialized brush for cleaning the tubes, and possibly fittings to adapt to different standards of plumbing in various countries.
• the preferred embodiment shall preferably be made from recycled materials, or from new materials which are recyclable.
• the preferred embodiment should be self-draining to minimize build up of fouling agents, and also to prevent possible damage due to freezing.
• the excess drain water will be automatically drained from the exchanger after every use.
• Adjustable feet are used to stabilize the embodiment on an uneven shower floor. These could also take the form of compressible foam or rubber pads (supplied in a variety of thicknesses).
• 5; Intake Drain Screen this is an integrated screen and trap together. This part would sit over the mouth of the drain intake and can be lifted out when it needs to be cleaned out. This helps to prevent fouling.
• the Plastic PEX Tube carries the cold water to be warmed up.
• the tubes are supported by brackets (22).
• the direction of water flow in the pipe would ideally be in the opposite direction to the drain water flow (counter flow). This greatly improves the efficiency of the embodiment compared to if the flow were parallel flow.
• the tubes in the preferred embodiment would be arranged in a multilayer spiral/coil pattern as shown in Figures 5B and 6, or alternatively in a flattened helix as shown in Figures 9A and 9B.
• the number of layers in the spiral/coil or the number of turns in the helix may be greater than that shown in the figures.
• the tubes could alternately have some kind of heat transfer augmentation, such as longitudinal fins, etc. See Figure 8.
• the Tubes could alternately be made of copper or other metal. The required length of tube would therefore be shorter, but the manufacturing cost would increase dramatically.
• Platform is a non-slip surface for standing on. It is slightly sloped to bring water towards the primary drain intake.
• the platform features surface channels or grooves (18).
• Drain Outlet Options allow the embodiment to be mounted in various locations.
• the outlet desired can possibly be punched out of the plastic mold and fitted with a bulkhead type fitting.
• the fitting could be screwed into place at the time of installation.
• Caps could be provided which would allow a punched out hole to be plugged if a different drain option is required.
• the unused outlets could thereby also be removed if needed, for cleaning, etc.
• Base is the bottom of the unit. It is slightly sloped to bring water towards the primary drain outlets 8, 9, 10, or 11.
• Baffles are used to guide the drain water through a spiral (Fig. 6) or helical/serpentine (Fig. 9A) course through the embodiment to roughly simulate a concentric tube heat exchanger. The flow is guided downstream towards one of the drain outlets. The channels thus formed help to raise the heat transfer rate, which in turn helps to improve the efficiency.
• the baffles do not always join with the platform, but instead there is clearance so that if there is a clog somewhere in the embodiment, the drain water will overflow a baffle upstream and bypass the clog. Some baffles may however join with the platform in order to support it. Channel walls/baffles may also allow insertion of a cleaning brush over them in order to access the tubes for cleaning.
• the Weir (see Figure 10a) is essentially a wall, slightly lower than the baffles, used to hold back the flow of water to cause the water level to rise inside the embodiment thereby submerging the tubes to allow heat transfer.
• the Weir has a small sluice (or opening) at the bottom to allow a small flow to bypass the weir.
• the purpose of the sluice is to allow all the drain water to exit the Embodiment when not in use. The reason for this is threefold. Firstly it keeps the tubes relatively dry to reduce corrosion, secondly, to reduce fouling, and thirdly, to reduce damage that may be caused by freezing in homes located in colder climates. Alternately, the weir may lack a draining opening and keep the tubes permanently submerged. The heat exchanger itself would then act like a trap.
• Platform Channels are essentially deep grooves in the platform (7)
• the depth of the channels would gradually increase towards the drain inlet (1).
• the purpose of the channels is to reduce the amount of time drain water is flowing over the platform, where it will rapidly lose heat due to convection and evaporation to the room.
• the platform's channel water will have a smaller surface area exposed to room temperature, and therefore retain more heat energy.
• the channels also help to reduce slipping while standing on the platform.
• Peripheral Flanges are used to seal the platform and base together. This can be accomplished with a gasket and a series of C-section fasteners (23). The flange would preferably have a small groove or a lip around the perimeter to keep the fasteners from slipping outwards and falling off.
• Tube supporting brackets are 22; Tube supporting brackets. These brackets hold the tubes in place.
• C-section fasteners are essentially tubes with a slit down the side forming a "C".
• the fasteners are slid over all 4 of the peripheral flanges (19) to hold the base to the platform so that the C shape clamps the flanges together.
• An alternate method is to use several nuts and bolts.
• the C-section is preferred since they can be easily removed for cleaning purposes.
• increased area can be achieved using ribs, fins, multiple tubes in a bundle, knurling (not shown), or other protuberances.
• baffles Fig. 8e
• Fig. 8e could also be used to move the flow in an 'S' pattern.
• the tube could also be wound in an overlapping (flattened) helix tight spiral, coaxial with the channel, similar to a telephone cord (see figure 9A and 9B).
• the first and second weir in the preferred embodiment shall be weirs with fixed sluices of the type shown in figure 10 a) but can alternatively be of type b) or c)
• the platform channels could be arranged in a grid shape instead of radially.
• the grid- shaped design is shown in Figure 11.
• Another possible method is to have the platform smooth (without channels) if it is too expensive to manufacture with the channels.
• the platform channels may be either arranged in a grid (Figure 11), or radially (Figure 5A).

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Hydrology & Water Resources (AREA)
• Public Health (AREA)
• Water Supply & Treatment (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

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• 2008
  • 2008-07-08 EP EP08779426A patent/EP2179225A1/de not_active Withdrawn
  • 2008-07-08 WO PCT/SE2008/050849 patent/WO2009008826A1/en active Application Filing

Non-Patent Citations (1)

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