HEAT RECOVERY UNIT FROM GRAY WATER

Abstract

A heat recovery unit for recovering heat from gray water while protecting the fresh water source from contamination is disclosed. The unit comprises an inner tube and an outer tube being larger than the inner tube for enclosing the inner tube creating a conduit between the inner and outer tubes. As such, the unit indirectly transfers the heat from a hot gray water source to a cold fresh water source that supplies fresh water to baths, showers or a water heater. The heat recovery unit further comprises an intermediate annular space between the inner wall of the outer tube and the outer wall of the inner tube. The intermediate annular space contains a third liquid, preferably a food grade liquid, such as distilled water, for providing a protective barrier between the inner and outer tubes.

Claims

1. A heat recovery unit comprising: an inner tube; an outer tube being larger than the inner tube, the outer tube externally enclosing the inner tube so as to create a conduit between the inner tube and the outer tube; a first end-piece configured to seal a first end of the inner tube, and a first end of the outer tube, wherein the first-end piece comprises two nozzles, one for the inner tube configured for input of a first liquid, and one for the outer tube configured for output of a second liquid; and a second end-piece configured to seal both a second end of the inner tube, and a second end of the outer tube, wherein the second end-piece comprises two nozzles, one for the inner tube configured for the output of the first liquid, and one for the outer tube configured for the input of the second liquid, wherein: the heat recovery unit further comprises an intermediate annular space within the conduit and between the inner wall of the outer tube and the outer wall of the inner tube, the intermediate annular space being configured to contain a third liquid for providing a protective barrier between the inner and outer tubes.

2. The heat recovery unit according to claim 1, wherein: the heat recovery unit is used in a counter-current mode; the first end-piece inner tube nozzle is used for inlet of the first liquid, the first end-piece outer tube nozzle is used for outlet of the second liquid, and the first end-piece intermediate annular space nozzle is used for outlet of the third liquid; and the second end-piece inner tube nozzle is used for output of the first liquid, the second end-piece outer tube nozzle is used for inlet of the second liquid, and the second end-piece intermediate annular space nozzle is used for inlet of the third liquid.

3. The heat recovery unit according to claim 2, wherein the second end-piece intermediate annular space nozzle further comprises a non-return valve configured to: prevent evaporation of the third liquid; and detect leaks between the inner tube and the outer tube.

4. The heat recovery unit according to claim 1, wherein the first liquid is fresh water from a public network system or from a well.

5. The heat recovery unit according to claim 1, wherein the second liquid is gray water.

6. The heat recovery unit according to claim 5, wherein the gray water is from a sanitary drain.

7. The heat recovery unit according to claim 3, wherein the first liquid is fresh water from a public network system or from a well.

8. The heat recovery unit according to claim 3, wherein the second liquid is gray water.

9. The heat recovery unit according to claim 8, wherein the gray water is from a sanitary drain.

10. The heat recovery unit according to claim 1, wherein the third liquid is a heat transfer liquid.

11. The heat recovery unit according to claim 1, wherein the third liquid is a food grade transfer liquid.

12. The heat recovery unit according to claim 1, wherein the third liquid is distilled water.

13. The heat recovery unit according to claim 3, wherein the third liquid is a heat transfer liquid.

14. The heat recovery unit according to claim 3, wherein the third liquid is a food grade transfer liquid.

15. The heat recovery unit according to claim 3, wherein the third liquid is distilled water.

16. The heat recovery unit according to claim 1, wherein the inner tube is configured to be always maintained full with the first liquid or with fresh water.

17. The heat recovery unit according to claim 1, wherein the intermediate annular space is configured to be always maintained full with the third liquid.

18. The heat recovery unit according to claim 1, wherein the outer tube is configured to be always maintained full with the second liquid or with gray water.

19. The heat recovery unit according to claim 1, wherein the heat recovery unit is configured to be installed substantially vertically.

20. The heat recovery unit according to claim 1, wherein the heat recovery unit further comprises an anode located in the inner tube, the anode serving to limit the accumulation of limestone and other mineral deposits in the heat recovery unit inner tube in addition to protecting the steel pipe against corrosion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawings in which:

[0027] FIG. 1 is a schematic illustration of a shower system and associated plumbing that integrates the drain water heat recovery (DWHR) unit in accordance with the present disclosure.

[0028] FIG. 2 is a schematic illustration of inner tube, outer tube and the intermediate annular space as well as the nozzles on the first end of the heat recovery unit in accordance with an embodiment of the present disclosure.

[0029] FIG. 3 is an example of the heat recovery unit in accordance with a preferred embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] The function of the heat recovery unit of the present invention is to indirectly transfer the heat from a hot gray water source to a cold fresh water source that supplies fresh water to baths, showers or a water heater.

[0031] In one preferred embodiment of the present invention, the heat recovery unit is integrated into the plumbing system of a building. Preheating the cold water in the shower or a bath significantly reduces the amount of energy required to heat the cold water to be consumed. The heat recovery unit device results in energy and cost savings. The use of a heat recovery unit may also increase the ability to heat up a larger volume of water when the capacity of the existing system is limited. The present invention is suitable for installation in domestic, commercial, industrial and institutional buildings including but not limited to residential buildings such as single-family homes, hotels and motels, health care facilities, senior citizens'residences, sports centers, businesses or industries that use a lot of hot water, ships and other locations where two liquids can make a heat transfer.

[0032] In one preferred embodiment of the present invention, the drinking water system is protected by a simple method and a reliable device which is based on the following principle: in the event of a leak in the heat exchanger, it is impossible to contaminate the drinking water of the network as long as the network is pressurized. Contaminated water cannot travel from a low-pressure to a high-pressure network. Contamination becomes possible only if the hydrostatic pressure of the drinking water system becomes equal to or less than the hydrostatic pressure in the heat recovery unit. In this event, the non-return valve, also known as a check-valve, installed on the drinking water inlet conduit prevents any possibility of contamination of the drinking water network through siphoning or backflow of the gray water.

[0033] Advantageously, the heat recovery unit of the present invention is simple and easy to assemble using standard equipment available from a hardware store or plumbing supplier.

[0034] The heat recovery unit may be small but still efficient and safe. The heat recovery unit may be manufactured using simple manufacturing methods with the use of high-quality standard materials and components used in plumbing. This feature makes it easier to comply with building standards, whether for an existing building installation or a new construction.

[0035] The performance of the invention is proportional to the quantity and the temperature of the water used. The heat recovery unit may preheat fresh cold water before it is used or be linked to a boiler system or hot water heater.

[0036] An improved drain water heat recovery unit, DWHR, for gray water will be described hereinafter. Although the technology is described in terms of specific illustrative embodiment(s), it is to be understood that the embodiment(s) described herein are by way of example only and that the scope of the disclose is not intended to be limited thereby.

[0037] In the application, reference to clean or fresh water includes potable water that is suitable for drinking. Gray water refers to all wastewater generated in households or office buildings from streams except for the wastewater from toilets. Sources of graywater include, sinks, showers, baths, clothes washing machines and dish washers.

[0038] An example of a drain water heat recovery, DWHR, integrated with a shower system is shown in FIG. 1. The new shower system (100) comprises two separate pipelines that eventually join together and provide warm water through the shower head (130). The first pipeline is the hot water pipeline (110) originating from a typical water heater (120). The second pipeline is the preheated water pipeline (101) that originating from the DWHR. The preheated water in the preheated water pipeline (101) is the result of a heat exchange between the hot gray water drained from the shower in the gray water drain pipeline (102) and fresh water in the fresh water line (104) both entering counter-currently in the drain water heat recovery. As can be appreciated from FIG. 1, the preheated water in the preheated water pipeline (101) may be branched with a fraction of a first branch being recycled toward the water heater (120) and a second fraction being eventually mixed with the hot water in the hot water pipeline (110) and flows toward the shower head (130). The system also has a main pipeline (109) for drain water.

[0039] In one preferred embodiment of the present invention, and with reference to FIGS. 2 and 3, the heat recovery unit includes a concentric arrangement (200) which comprises: [0040] a. an inner tube (210) as shown by inner solid circle line; [0041] b. an outer tube (230) as shown by outer solid circle line and having a larger diameter than the inner tube, the outer tube externally enclosing the inner tube in a concentric manner so as to create a conduit between the inner tube (210) and the outer tube (230); [0042] c. an intermediate annular space (250) as shown by dashed circle line within the conduit and between the inner wall of the outer tube (230) and the outer wall of the inner tube (210); [0043] d. a first end-piece configured to seal (i) a first end of the inner tube, (ii) a first end of the outer tube and (iii) a first end of the intermediate annular space, wherein the first-end piece comprises three nozzles: one for the inner tube (220), one for the outer tube (240), and one for the intermediate annular space (260); and [0044] e. a second end-piece configured to seal a second end of the outer tube, a second end of the inner tube, and a second end of the intermediate annular space wherein the second end-piece comprises three nozzles (not shown), one for the inner tube, one for the outer tube and one for the intermediate annular space, respectively.

[0045] In one embodiment of the present invention, the DWHR may be installed vertically.

[0046] It will be apparent to the person skilled in the art that in the context of the present disclosure, the term nozzle, as an element through which a fluid flows in or out of a system, can be used interchangeably with the terms opening, inlet and outlet without departing from the spirit of the disclosure.

[0047] According to a preferred embodiment, and as described in FIG. 3, the gray water (GW) from the bath or shower enters the drain water heat recovery unit (300) through inlet conduit, collector or pipeline (102) which is located at the top of the heat recovery unit (300) which may be of the same diameter as the gray water pipe connected to the bath/shower or any other commercial, industrial, institutional and naval gray water systems. This concept allows the free circular flow of gray water inside the outer tube (230) of the heat recovery unit around the intermediate annular space (250) in which a heat-transfer medium flows. In some embodiments the heat transfer medium is a heat transfer liquid. Preferably, the heat transfer liquid is a food grade liquid, such as distilled water. The intermediate annular space (250) on its inner side surrounds the inner tube (210) in which the fresh water flows. The intermediate annular space (250) is configured to receive heat from the warmer gray water flowing through the outer tube and transfer it to cooler fresh water flowing through the inner tube (210) thereby heating up the fresh water leaving the drain water heat treating unit for ultimate consumption.

[0048] Advantageously, this mode of indirect heat exchange between the hot gray water and cold fresh water, through an annular space that contains the heat-transfer medium, improves the safety aspect of the heat recovery unit and reduces potential damages through any gray water or fresh water breakthrough.

[0049] Moreover, the heat recovery unit according to the present invention may further comprise a check-valve (270) installed on the nozzle (260) for the intermediate annular space. Advantageously, the check-valve (270) is configured to detect leakage in the heat recovery unit of the present invention. Specifically, in the event that a leakage occurs on the fresh water or the gray water reservoirs, the leaked water will exit the check-valve (270) thereby indicating a an internal leakage as the check-valve (270) is designed to open to atmosphere. Being open to atmosphere brings another advantage to the check-valve (270) in that evaporation of the heat transfer medium within the intermediate annular space is prevented.

[0050] It is noteworthy that the person skilled in the art would appreciate that fluids other than distilled water could be used as heat-transfer medium in the intermediate annular space without departing from the spirit of the present disclosure.

[0051] According to a preferred embodiment, the gray water in the gray water outlet pipe (312) may rise to reach the same level as the upper level of the outer tube or tank (313) comprising the gray water to keep the tank full to maximize the heat transfer.

[0052] According to a preferred embodiment, the fresh cold water is supplied from a public aqueduct (104) and passes through the non-return valve (305) before entering the base of the heat recovery unit into the fresh water tank or inner tube (210) through the fresh water inlet opening or nozzle (220) into the cold water section where it is heated as it flows through the inner tube until it exits the top of the inner tube (210). The hot fresh water (HFW) being lighter than the cold fresh water rises in the hot zone and comes out at the top of the heat recovery unit and exits through the fresh water outlet (101) to supply the cold tap of the bath/shower or the heater. This has the effect of significantly reducing the hot water consumption of the bath/shower, boiler system or hot water heater by increasing the temperature of the cold fresh water supply.

[0053] According to a preferred embodiment, the pipe coming from the bath/shower feeds the outer gray water tank (230) or tube (102), while the fresh water (FW) from the public network pipe (104) feeds the fresh water tank (210) through the fresh water inlet opening or nozzle (not shown). The preheated fresh water exits the fresh water inner tube (210) through the fresh water outlet (101) to the cold tap of the bath/shower or the water heater. The gray water flows from the outer tube outlet (314) from the gray water tank (230) to the main drain (109). The pressurized fresh water reservoir wall is separated from the gray water reservoir wall by the intermediate annular space (250) that contains the heat-transfer medium. The main drain (109) directs the gray water exiting the gray water tank to a sewage system or a septic tank, or even any gray water collection system for another use prior to being directed to the sewage system or the septic tank.

[0054] According to a preferred embodiment, a vent duct (311) is installed between a pipe (102) feeding the gray water inlet (240) into the outer tube (4) and the gray water outlet pipe (312). This vent duct (311) allows good ventilation of the grey water pipes and acts as an overflow in the event of the heat recovery unit being obstructed.

[0055] According to a preferred embodiment, the heat recovery unit may further comprise a gray water drain valve (308) to drain the gray water tank and/or a preheated fresh water drain valve (306) to drain the fresh water inner tube (210).

[0056] According to a preferred embodiment, the heat recovery unit inner tube (210) may further comprise an anode (not shown), the anode being further attached to a first and a second end inside the inner tube. The anode serves to limit the accumulation of limestone and other mineral deposits in the heat recovery unit inner tube (210) in addition to protecting the steel pipe against corrosion.

[0057] According to a preferred embodiment, the fresh water pipe (104) is fed from a public fresh water pressurized network and enters the heat recovery unit through the fresh water inlet pipe (315) and exits the unit through the fresh water outlet pipe (101) after being preheated.

[0058] According to a preferred embodiment, the gray water pipe (102) is fed from the gray water pipe originating from the used shower or bath and enters the outer tube or gray water tank. The gray water then exits said tank through the gray water outlet pipe (314) and is directed to the main drain (109).

[0059] According to a preferred embodiment, both end-pieces of the heat recovery unit may further have rounded (or convex) surfaces. The round (or convex) shape facing the exterior is to avoid a deformation during the hydraulic pressure test for the inner tube that will hold the pressurized fresh water. The heat recovery unit further comprises nozzles at both end-pieces which are made before assembling the heat recovery unit. The unit may further comprise connecting pipes that may be welded to the first and second end-pieces.

[0060] According to a preferred embodiment, the outer tube or tank has a volume of about 20 gallons with a hydrostatic test pressure of about 5 psi. The fresh water inner tube or tank has a volume of about 10 gallons with a hydrostatic test pressure of about 300 psi. The intermediate annular space between the inner and outer tubes or tanks has a volume of about 5 gallons with a hydrostatic test pressure of about 5 psi.

[0061] While the check-valve (270) is configured to detect leakage in the heat recovery unit, the hydrostatic test pressure of the annular space and the gray water outer tube being the same, it should not be possible for the heat-transfer medium to leak into gray water outer tank.

[0062] If a leak is eventually detected, as explained above and through the function of check-valve (270), the unit may be removed from operation for repair to prevent contamination of the fresh water feeding the heat recovery unit in case pressure fluctuations in the fresh water network occur. When a leak is detected, the presence of the non-return valve in the fresh water inlet conduit prevents contamination of the public fresh water network system. In this case, while the leak may affect the heat recovery unit, it will not contaminate the fresh water system.

[0063] According to a preferred embodiment, an insulating jacket may be installed around the heat recovery unit. The insulating jacket may comprise three sections, one for each end and one for the cylindrical section of the heat recovery unit. The insulating jacket may be made of a flexible material or a rigid material such as urethane.

[0064] According to a preferred embodiment, the heat recovery unit outer tank or tube wall may be of high-quality stainless steel or any other heat transfer promoter that is thick enough to last a long time.

[0065] According to a preferred embodiment, the pressurized inner tank (210) may be made of high-quality stainless steel or any other material that promotes heat transfer. Both end-pieces of the heat recovery unit inner tube (210) may further comprise a linear section facing the interior ends and may also be made of stainless steel. The gray water inlet and outlet nozzles are made of stainless steel, as well as any adapters or fittings that are connected to any plumbing parts.

[0066] According to a preferred embodiment, other types of fluids may be used to feed the heat recovery unit in order to transfer heat from a hot stream to a cold stream. The heat recovery unit may be used not only to recover heat from gray water streams but also to heat or cool down systems that need to be heated or cooled. In another embodiment, water from a well may also be used as a source of cold water to be heated up using the heat recovery unit.

[0067] According to a preferred embodiment, the heat recovery unit may be configured to integrate a device provided with an application that allows a continuous monitoring of the unit and its operating efficiency. The heat recovery unit may be further configured to operate in a network of devices or Internet of Things (IoT).

[0068] According to a preferred embodiment, the heat recovery unit may be of any geometrical shape. The heat recovery unit may be of different sizes or may be further elongated or narrower depending on space restrictions. Space changes may impact the heat transfer and consequently the thermal efficiency of the heat recovery unit.

[0069] According to a preferred embodiment, the heat recovery unit may be configured to comply with local regulations as well as any fittings, piping or any other required plumbing equipment.

[0070] The features of the present invention which are believed to be novel are set forth with particularity in the appended claims.

[0071] While illustrative and presently preferred embodiment(s) of the instant disclosure have been described in detail hereinabove, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations.