CA1329587C - Wastewater heat recovery apparatus - Google Patents
Wastewater heat recovery apparatusInfo
- Publication number
- CA1329587C CA1329587C CA 591530 CA591530A CA1329587C CA 1329587 C CA1329587 C CA 1329587C CA 591530 CA591530 CA 591530 CA 591530 A CA591530 A CA 591530A CA 1329587 C CA1329587 C CA 1329587C
- Authority
- CA
- Canada
- Prior art keywords
- heat
- waste water
- heat exchange
- exchange means
- reservoir
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E03—WATER SUPPLY; SEWERAGE
- E03D—WATER-CLOSETS OR URINALS WITH FLUSHING DEVICES; FLUSHING VALVES THEREFOR
- E03D5/00—Special constructions of flushing devices, e.g. closed flushing system
Landscapes
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Public Health (AREA)
- Water Supply & Treatment (AREA)
- Heat-Pump Type And Storage Water Heaters (AREA)
Abstract
Abstract This invention automatically reclaims heat from residential wastewater, onsite. The apparatus is simple, inexpensive, has no moving parts and requires no maintenance in its operation.
Recovered heat preheats feedwater of the normal hot water tank-year round. Passage of cold wastewater has no adverse effect.
Lowers overall energy consumption for short payback period.
Provides buffer to energy peak-demand periods. Its design includes:
a simple non-pressurized vessel adaptable for thermal storage;
positive safeguard against fresh-water contamination.; low in cost; fittable to existing houses, multi-dwelling buildings, laundromats, restaurants, hotels, etc.
Recovered heat preheats feedwater of the normal hot water tank-year round. Passage of cold wastewater has no adverse effect.
Lowers overall energy consumption for short payback period.
Provides buffer to energy peak-demand periods. Its design includes:
a simple non-pressurized vessel adaptable for thermal storage;
positive safeguard against fresh-water contamination.; low in cost; fittable to existing houses, multi-dwelling buildings, laundromats, restaurants, hotels, etc.
Description
~ 1 ` 1 329587 SPECIF~CATIONS
Wastewater heat recovery for residential use are not commercially available even in this time of energy conservation and environmental concern. Hot water for cleaning of bodies, laundry and kitchenware, consumes approximately one half of the total residential energy consumption (from s Canadian Electrical Association Project Report number: 913 U 160 Chapter 14, pp. 14). This energy laden waste water is then fed into a sewer system where it's Yaluable heat is lost into the earth.
Heat recovery has thus far proven intractable primarily because:
0 (A) the temperature of waste water from human activity in any building, can never be predicted. It may be very cold or very hot at any given moment, and, (B) it is necessary to store recovered heat for a time such as over night. The combination of waste water of indeterminate temperature and the necessity of heat storage, is why a commercially viable waste water heat recovery apparatus has not yet been invented, in spite of efforts over long periods of time by many skilled in this field.
The present invention solves this problem with a unique, low cost hea~ exchanger where the stored heat from previous recovery is not lost to cold waste water flowing at any time therea~ter.
The heat reclaimed from the waste water may be used effectively to preheat the fresh feedwater of a normal hot-water tank. To prevent contarnination of such fresh water, both the waste water and the colder fluid to be pre-heated, pass through their own separate heat exchanger elements both of which are submerged in a non-pressurized heat transfer I storage tank filled with a fluid such as plain water.
In the present invention, a reservoir is filled wirh a fluid such as water. Natural strati~ication 2s automatically arranges the water into demperature-dependant strata. The waste water heat exchange element lays at the bottom of the reservoir in the coldest possible strata of the watsr, while the second heat exchange element passing the coolder fluid to be heated, is submerged in the warmest, top most strata.
The temperature of the fresh feedwater establishes the base or bottom temperature of the apparatus since it will cool it's surrounding liquid which then sinks to the bottom. The temperature of the passing waste water is usually always at least marginally higher than the temperature of the fresh feedwater because it is somewhat heated by it's passage through the building's plumbing system. Therefore, virtually all waste water arriving at the apparatus will give up heat energy into the cold lower strata of liquid which tnen must rise. This reclaimed heat is thereby made available 3s to preheat t'ne always colder feedwater. The apparatus operates entirely under the physical principle of convection- it does not require any moving parts, controls or valves that add to it's cost.
Moreover no maintenance is normally required. This impor~ant 'simplicity of design' and resultant short 'pay back' period will ensure widespread acceptance.
Widespread acceptance will have a unexpected cascade effect: a net reduction in the amount of money required for heating water leads to a significandy lower demand for energy to heat water and frees up rnonies for other needs; this lower demand also leads to a lower demand for energy for water heating; that leads to less fuel to be burnt and to conservation of fossil fuels; which leads to a reduction in smokestack emissions; which leads to a reduction in the amounts of acid rain falling; which leads to an overall benefit to the environment--our health, our lakes, our forests and 4s our buildings.
The operation of the invention is based on the cornmon physics of fluids wherein heated fluid becomes less dense and therefore will rise and remain as a upper-most layer in the reservoir, while cooled fluid becomes more dense and therefore sinks and 'puddles' at the bottomof the reservoir.
This is well known and defined as 'stratificationl. Since tne two heat exchanger coils are displaced so vertically wherein one is in the upper-most region, and the second in the lower-most, any fluid passing through either exchanger element will be bathed in the hea~ transfer fluid snost appropriate ~or said exchangers purpose, i.e. the fresh feedwater to which the recovered heat is to be transferred is bathed in the accumulated warmest fluid while the fluid from which heat is to be reclaimed, is ba~ed in the coolest fluid.
The four operational conditions of the present invention are:
1. Cold fresh water is passing through the upper element and into the hot water tank when hot water is being demanded somewhere in the building, but no waste water is flowing, e.g.
filling a bathtub or washing machine. Here the cold ~eedwater will pick up the stored heat and will thus appear at the entrance to the hot water tank as somewhat warmer than the ground water temperature.
Wastewater heat recovery for residential use are not commercially available even in this time of energy conservation and environmental concern. Hot water for cleaning of bodies, laundry and kitchenware, consumes approximately one half of the total residential energy consumption (from s Canadian Electrical Association Project Report number: 913 U 160 Chapter 14, pp. 14). This energy laden waste water is then fed into a sewer system where it's Yaluable heat is lost into the earth.
Heat recovery has thus far proven intractable primarily because:
0 (A) the temperature of waste water from human activity in any building, can never be predicted. It may be very cold or very hot at any given moment, and, (B) it is necessary to store recovered heat for a time such as over night. The combination of waste water of indeterminate temperature and the necessity of heat storage, is why a commercially viable waste water heat recovery apparatus has not yet been invented, in spite of efforts over long periods of time by many skilled in this field.
The present invention solves this problem with a unique, low cost hea~ exchanger where the stored heat from previous recovery is not lost to cold waste water flowing at any time therea~ter.
The heat reclaimed from the waste water may be used effectively to preheat the fresh feedwater of a normal hot-water tank. To prevent contarnination of such fresh water, both the waste water and the colder fluid to be pre-heated, pass through their own separate heat exchanger elements both of which are submerged in a non-pressurized heat transfer I storage tank filled with a fluid such as plain water.
In the present invention, a reservoir is filled wirh a fluid such as water. Natural strati~ication 2s automatically arranges the water into demperature-dependant strata. The waste water heat exchange element lays at the bottom of the reservoir in the coldest possible strata of the watsr, while the second heat exchange element passing the coolder fluid to be heated, is submerged in the warmest, top most strata.
The temperature of the fresh feedwater establishes the base or bottom temperature of the apparatus since it will cool it's surrounding liquid which then sinks to the bottom. The temperature of the passing waste water is usually always at least marginally higher than the temperature of the fresh feedwater because it is somewhat heated by it's passage through the building's plumbing system. Therefore, virtually all waste water arriving at the apparatus will give up heat energy into the cold lower strata of liquid which tnen must rise. This reclaimed heat is thereby made available 3s to preheat t'ne always colder feedwater. The apparatus operates entirely under the physical principle of convection- it does not require any moving parts, controls or valves that add to it's cost.
Moreover no maintenance is normally required. This impor~ant 'simplicity of design' and resultant short 'pay back' period will ensure widespread acceptance.
Widespread acceptance will have a unexpected cascade effect: a net reduction in the amount of money required for heating water leads to a significandy lower demand for energy to heat water and frees up rnonies for other needs; this lower demand also leads to a lower demand for energy for water heating; that leads to less fuel to be burnt and to conservation of fossil fuels; which leads to a reduction in smokestack emissions; which leads to a reduction in the amounts of acid rain falling; which leads to an overall benefit to the environment--our health, our lakes, our forests and 4s our buildings.
The operation of the invention is based on the cornmon physics of fluids wherein heated fluid becomes less dense and therefore will rise and remain as a upper-most layer in the reservoir, while cooled fluid becomes more dense and therefore sinks and 'puddles' at the bottomof the reservoir.
This is well known and defined as 'stratificationl. Since tne two heat exchanger coils are displaced so vertically wherein one is in the upper-most region, and the second in the lower-most, any fluid passing through either exchanger element will be bathed in the hea~ transfer fluid snost appropriate ~or said exchangers purpose, i.e. the fresh feedwater to which the recovered heat is to be transferred is bathed in the accumulated warmest fluid while the fluid from which heat is to be reclaimed, is ba~ed in the coolest fluid.
The four operational conditions of the present invention are:
1. Cold fresh water is passing through the upper element and into the hot water tank when hot water is being demanded somewhere in the building, but no waste water is flowing, e.g.
filling a bathtub or washing machine. Here the cold ~eedwater will pick up the stored heat and will thus appear at the entrance to the hot water tank as somewhat warmer than the ground water temperature.
2. Waste water only, is draining through the apparatus. Here the water temperature at the bottom of the reservoir is cooler than the waste water in most all occasions and heat will he transferred to the storage fluid, which rises as this occurs, to the top. Thus any waste heat will continually be given up until all the storage fluid reaches the waste water temperature.
3. Both warm waste water and cold fresh water are flowing through this apparatus, for example, a shower is being taken or a sink is being used. Here, a toroidal flow is established and transfer of heat from the warm draining waste water is transfe~red to the cold water rais;ng it's temperature considerably, reducing water heating expense.
4. Only cold waste water is passing through the apparatus, as when rins;ng with cold water.
Here upwards convection stops and the net result is a thin layer of cold water up to the level E f the lower element's upper surface-a small percentage of the reservoir's volume, so .
2 t 329587 virtually none of the stored heat is lost under this, the worst of conditions, for thermal storage heat exchangers and for wsate water heat recovery devices described in the prior art.
In drawings which illustrate embodiments of the invention;
s Figure 1 is a three dimensional view, partially in section, showing a preferred embodiment but with the cover and the insulation removed for clarity;
Figure 2 is a three dimensional view of the simplest embodiment where the reservoir and submerging fluid are omitted and the toroidal convection current are shown clearly;
Figure 3 is the same embodiment partially in section with the reservoir and submerging fluid 0 shown;
Figure 4 is the same embodiment partially in section with the duct added for convection énhancement;
Figure S shows the manner in which the invention can be plumbed into a residential system.
Reservoir 1 is made of a plastic (for low thermal conduction) with a fitted cover ~not shown) to eliminate evaporation, and wrapped in insulation (not shown) to reduce heat loss, and is mostly filled with a Fluid 2, such as water, which must naturally and autornatically stratify into temperature dependent strata, the coldest stratum at the bottom of the reservoir and the warmest stratum floating at the top. The reservoir is filled to a Level 2a such that Convection Curr~nts 15, 20 20 can easily move about the colder fluid Upper Element 3 which is plumbed to the colder fluid, such as the feed water for a hot water tank, via Fittings 9 and 10 the cold fluid entry and exit indicated by Flow Arrows 21. The upper end of Duct 5 is encircled by the upper heat exchanger element. At the lower end of the duct, and enclosed by it, is the Waste Water Element 4 through which the waste water liquid, from which heat is to be recovered, passes through via plumbing 25 Fittings 7 and 8 and indicated by Flow Arrows 21. When the bottom most stratum of fluid is heated by the waste water element, Rising Convection Currents 14 in Fig. l, form and due to their reduced density, must rise. The duct improves the temperature spread between the top and bottom of the fluid since the rising convection currents, are kept separate from Downwards Convection Currents 12 in Fig. 1, so that they both arrive at their respective strata as quickly and with as little 30 ternperature change as possible. Lower Convection CulTents 13, in Fig. 1, is fluid passing under the duct to meet up with the waste water element to repeat the cycle.
Should the lower stratum of the reservoir fluid be warmer than waste water element, then no upwards convection takes place, and, no significant amount of previously recovered heat is lost to the waste water. Should no fluid flow through the upper element but warm liquid pass through the 35 waste water element then warmed fluid moving in the direction of 11 and 14, accumulates as a heated layer at the top of the reservoir. When the upper element is passing a cooler fluid it will absorb the accumulated heat and exit at fitting 9 wanner than it entered at fitting 10.
In this way the invention produces net temperature gain ul the colder fluid virtually all the time.
If cooler fluid passes through the upper element while no waste water passes through the waste 40 water element, then a layer of dense cool fluid seffles in the bottom of the reservoir which is then ready to absorb heat as soon as waste water is flowing. When the upper element is passing cool liquid and the waste water element is passing warm liquid, then a toroidal convection takes place as indicated by the path described by 14, 11, 15, 12 and 13, in Fig. 1, and 20 in Figs. 2, 3, and 4, providing an efficient flow of fluid over and between both upper and lower heat exchanger 45 e~ments.
In Drawing S a typical setup is shown where Hot Water Outlet 30 to the building, is plumbed as normal from Hot Water Tank 32 which is an electrically heated device connected to the mains wiring by Wire 43. Of course it could also be a ga~s- or oil- fired water heater.
Feedwater Supply Pipe 31 is intercepted from being connected to the hot water tank and instead sû connects to the reclaiming element in the Present Invention 33. The water bea~ng the reclaimed heat is then fed to the hot water tank via Outlet Pipe 40. Stand 34 ensures that the present invention is at an appropriate height off the Ground Level 39. Basement Ceiling 37 has, emerging from the va~ous drains above, the Main Drain 38 through which all the waste water flows on the way to Sewer Connection 42. A Non-Blocking Separator 35 allows solids to pass through while liquids 55 are conducted via Connection Pipe 41 into the reclaiming element in the present invention where the heat is reclaimed and the the waste water then passes out, back into main drain via Connecting Pipe 36. Thus feedwater entering the present invention from the feed water swpply pipe is preheated by waste water from the main drain and then enters the hot water tank at an elevated temperature.
r~1~
Here upwards convection stops and the net result is a thin layer of cold water up to the level E f the lower element's upper surface-a small percentage of the reservoir's volume, so .
2 t 329587 virtually none of the stored heat is lost under this, the worst of conditions, for thermal storage heat exchangers and for wsate water heat recovery devices described in the prior art.
In drawings which illustrate embodiments of the invention;
s Figure 1 is a three dimensional view, partially in section, showing a preferred embodiment but with the cover and the insulation removed for clarity;
Figure 2 is a three dimensional view of the simplest embodiment where the reservoir and submerging fluid are omitted and the toroidal convection current are shown clearly;
Figure 3 is the same embodiment partially in section with the reservoir and submerging fluid 0 shown;
Figure 4 is the same embodiment partially in section with the duct added for convection énhancement;
Figure S shows the manner in which the invention can be plumbed into a residential system.
Reservoir 1 is made of a plastic (for low thermal conduction) with a fitted cover ~not shown) to eliminate evaporation, and wrapped in insulation (not shown) to reduce heat loss, and is mostly filled with a Fluid 2, such as water, which must naturally and autornatically stratify into temperature dependent strata, the coldest stratum at the bottom of the reservoir and the warmest stratum floating at the top. The reservoir is filled to a Level 2a such that Convection Curr~nts 15, 20 20 can easily move about the colder fluid Upper Element 3 which is plumbed to the colder fluid, such as the feed water for a hot water tank, via Fittings 9 and 10 the cold fluid entry and exit indicated by Flow Arrows 21. The upper end of Duct 5 is encircled by the upper heat exchanger element. At the lower end of the duct, and enclosed by it, is the Waste Water Element 4 through which the waste water liquid, from which heat is to be recovered, passes through via plumbing 25 Fittings 7 and 8 and indicated by Flow Arrows 21. When the bottom most stratum of fluid is heated by the waste water element, Rising Convection Currents 14 in Fig. l, form and due to their reduced density, must rise. The duct improves the temperature spread between the top and bottom of the fluid since the rising convection currents, are kept separate from Downwards Convection Currents 12 in Fig. 1, so that they both arrive at their respective strata as quickly and with as little 30 ternperature change as possible. Lower Convection CulTents 13, in Fig. 1, is fluid passing under the duct to meet up with the waste water element to repeat the cycle.
Should the lower stratum of the reservoir fluid be warmer than waste water element, then no upwards convection takes place, and, no significant amount of previously recovered heat is lost to the waste water. Should no fluid flow through the upper element but warm liquid pass through the 35 waste water element then warmed fluid moving in the direction of 11 and 14, accumulates as a heated layer at the top of the reservoir. When the upper element is passing a cooler fluid it will absorb the accumulated heat and exit at fitting 9 wanner than it entered at fitting 10.
In this way the invention produces net temperature gain ul the colder fluid virtually all the time.
If cooler fluid passes through the upper element while no waste water passes through the waste 40 water element, then a layer of dense cool fluid seffles in the bottom of the reservoir which is then ready to absorb heat as soon as waste water is flowing. When the upper element is passing cool liquid and the waste water element is passing warm liquid, then a toroidal convection takes place as indicated by the path described by 14, 11, 15, 12 and 13, in Fig. 1, and 20 in Figs. 2, 3, and 4, providing an efficient flow of fluid over and between both upper and lower heat exchanger 45 e~ments.
In Drawing S a typical setup is shown where Hot Water Outlet 30 to the building, is plumbed as normal from Hot Water Tank 32 which is an electrically heated device connected to the mains wiring by Wire 43. Of course it could also be a ga~s- or oil- fired water heater.
Feedwater Supply Pipe 31 is intercepted from being connected to the hot water tank and instead sû connects to the reclaiming element in the Present Invention 33. The water bea~ng the reclaimed heat is then fed to the hot water tank via Outlet Pipe 40. Stand 34 ensures that the present invention is at an appropriate height off the Ground Level 39. Basement Ceiling 37 has, emerging from the va~ous drains above, the Main Drain 38 through which all the waste water flows on the way to Sewer Connection 42. A Non-Blocking Separator 35 allows solids to pass through while liquids 55 are conducted via Connection Pipe 41 into the reclaiming element in the present invention where the heat is reclaimed and the the waste water then passes out, back into main drain via Connecting Pipe 36. Thus feedwater entering the present invention from the feed water swpply pipe is preheated by waste water from the main drain and then enters the hot water tank at an elevated temperature.
r~1~
Claims (9)
1. An apparatus to recover heat from draining waste water of indeterminate temperature, comprising a reservoir, a liquid in said reservoir, said liquid naturally stratifying into temperature-dependent strata;
a heat exchange means, said heat exchange means having means for connection to the supply of the waste water;
said heat exchange means being positioned bottomwards and substantially parallel with said strata and thereby naturally and continuously submerged in coldest strata of said liquid;
the whole arranged to recover at least some heat from said draining waste water by heat transfer into said liquid which convects upwards to thereby prevent said recovered heat from heating colder waste water that may be draining thereafter.
a heat exchange means, said heat exchange means having means for connection to the supply of the waste water;
said heat exchange means being positioned bottomwards and substantially parallel with said strata and thereby naturally and continuously submerged in coldest strata of said liquid;
the whole arranged to recover at least some heat from said draining waste water by heat transfer into said liquid which convects upwards to thereby prevent said recovered heat from heating colder waste water that may be draining thereafter.
2. An apparatus as defined in Claim 1 where said heat exchange means is at least one flat spiral of tubing.
3. An apparatus to recover heat from draining waste water of indeterminate temperature and to transfer said recovered heat to a colder fluid, said apparatus comprising a reservoir, a liquid in said reservoir, said liquid naturally stratifying into temperature-dependent strata;
a first heat exchange means disposed bottomwards in said reservoir, said first heat exchange means having means for connection to the supply of the waste water;
a second heat exchange means disposed topwards in said reservoir, said second heat exchange means having means for connection to the colder fluid to be heated, andsaid second heat exchange means at least contacting said liquid;
the arrangement being such that at least some heat from said draining waste water heat is recovered by heating said liquid which rises by convection to heat said colder fluid.
a first heat exchange means disposed bottomwards in said reservoir, said first heat exchange means having means for connection to the supply of the waste water;
a second heat exchange means disposed topwards in said reservoir, said second heat exchange means having means for connection to the colder fluid to be heated, andsaid second heat exchange means at least contacting said liquid;
the arrangement being such that at least some heat from said draining waste water heat is recovered by heating said liquid which rises by convection to heat said colder fluid.
4. An apparatus as defined in Claim 3 including a member in said reservoir to separate rising and sinking convection currents.
5. An apparatus as defined in Claim 4 where said convection currents rise centrally and sink peripherally.
6. An apparatus as defined in Claim 3 where said first heat exchange means is substantially planar and positioned substantially parallel with said strata.
7. An apparatus as defined in Claim 6 where said first heat exchange means is at least one flat spiral of tubing.
8. An apparatus as defined in Claim 3 where said colder fluid is water.
9. An apparatus as defined in Claim 8 where said water is the feed water of a water heater.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 591530 CA1329587C (en) | 1989-02-20 | 1989-02-20 | Wastewater heat recovery apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 591530 CA1329587C (en) | 1989-02-20 | 1989-02-20 | Wastewater heat recovery apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1329587C true CA1329587C (en) | 1994-05-17 |
Family
ID=4139648
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 591530 Expired - Fee Related CA1329587C (en) | 1989-02-20 | 1989-02-20 | Wastewater heat recovery apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1329587C (en) |
-
1989
- 1989-02-20 CA CA 591530 patent/CA1329587C/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |