WO2009077966A2

WO2009077966A2 - Heater tank

Info

Publication number: WO2009077966A2
Application number: PCT/IB2008/055292
Authority: WO
Inventors: Zvi Shtilerman
Original assignee: Activehome Ltd.
Priority date: 2007-12-14
Filing date: 2008-12-15
Publication date: 2009-06-25
Also published as: WO2009077966A3; WO2009077966A4

Abstract

A heater tank comprising a generally cylindrical shell; an upper and a lower end cap positioned at upper and lower ends, respectively, of the cylindrical shell; one or more heat exchanger tubes substantially disposed within the tank; a heating mechanism; and at least one set of heat exchanger tube introduction and exit apertures, one set for each helical heat exchanger tubes. The apertures are adapted for the helical water heater tube(s) to pass therethrough. The inlet and outlet apertures respectively enter and exit the tank substantially parallel to the wall of the cylindrical shell. The heater tank is preferably made of a plastic and more preferably via an extrusion blow molding process.

Description

HEATER TANK

FIELD OF THE INVENTION

The present invention relates to a heater tank or boiler.

BACKGROUND OF THE INVENTION

Water heater storage tanks, whether pressurized or non-pressurized, are commonly made of carbon steel. However, such tanks are prone to corrosion and are relatively expensive. To combat the corrosion, various methods are used; for example, coatings, cathodic protection such as a sacrificial anode and the like. Despite the protective methods applied, water heater tank life span is typically about 15 years. Another material often used is stainless steel, which is more expensive and still remains sensitive to water containing chlorides. In addition, metal is a relatively good thermal conductor and so a considerable amount of insulation is required.

For heater tanks of the type having a heat exchanger therein, prior to welding on the end-caps the heat exchanger is placed therein.

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide a heater tank that avoids or at least reduces some or all of the aforementioned issues.

It is another object of the present invention to provide a heater tank with good insulation properties and a long life span.

It is another object of the present invention to provide a heater tank that can be manufactured relatively easily and inexpensively.

It is another object of the present invention to provide a heater tank that is made of plastic and further that can be manufactured by an extrusion blow molding process, thus wherein the tank is an essentially closed vessel.

It is another object of the invention to provide a heater tank designed so that a corresponding heat exchanger or helical water tube can be introduced into and exit from the tank even though the tank is an essentially closed vessel. SUMMARY OF THE INVENTION

The present invention relates to a generally barrel- shaped water heater tank, a method of manufacturing the tank and assembly thereof. The tank typically has one or two heat exchanger tubes or helical water tubes (these terms may be used interchangeably herein) each of which are introduced into the tank via respective apertures in respective recesses in (or projections projecting from) the tank. The recesses/projection where the heat exchanger tube(s) are introduced abut or are adjacent to one of the end caps of the tank. It should be understood that in some embodiments, the tube introduction recess/projection could be part of the end cap. The helical heat exchanger tube(s) exit the tank via aperture(s) in similar recess(es) inboard of the end caps.

According to one embodiment of the invention, the tank is made of a non- plastic material, for example, a metal such as carbon steel; however, according to preferred embodiments, at least the cylindrical shell and end caps of the tank are made of a plastic material and according to particularly preferred embodiments, the cylindrical shell and end caps of the tank are made by an extrusion blow molding process.

Accordingly, the present invention provides a heater tank comprising a shell (generally cylindrical); an upper and a lower end cap positioned at upper and lower ends, respectively, of the shell; one or more heat exchanger tubes substantially disposed within the tank; a heating mechanism; and at least one set of heat exchanger tube introduction and exit apertures, one set for each helical heat exchanger tubes. The apertures are adapted for the helical water heater tube(s) to pass therethrough. The inlet and outlet apertures respectively enter and exit the tank substantially parallel to the wall of the cylindrical shell. The heater tank is preferably made of a plastic and more preferably via an extrusion blow molding process.

The present invention further provides a method of producing a heater tank comprising: providing a generally barrel-shaped tank with: a shell; an upper and a lower end cap positioned at upper and lower ends, respectively, of the shell; at least one helical heat exchanger tube disposed in the tank and entering and exiting from the tank; and a pair of apertures for each helical heat exchanger tube, to pass in and out there-through, the apertures being generally perpendicular to the walls of the shell and one aperture of each pair of apertures being adjacent one of the upper or lower end caps; and spirally inserting the helical heat exchanger tube through the aperture(s) at or adjacent one of the upper or lower end caps and out the other aperture of the pair of apertures.

According to some embodiments, the cylindrical shell and end caps of the tank are produced using other plastic processing processes, for example, injection molding, however, blow molding is believed to be a preferable process as it tends to be inexpensive and/or involve a shorter processing time, and/or require less energy, and/or produce thinner walls (thereby saving material and producing a lighter weight tank) whereas injection molding typically results in an "open" tank (for example, with an opening the size/diameter of the tank, in order to remove a core used in this process). Another plastic processing technique that can be used is rotational molding, which would produce a "closed" tank, however this process also tends to be relatively expensive and produces thick walls.

According to particular embodiments, some of which may be combined, the tank comprises the following properties and/or materials and/or designs (in no particular order):

1) It is predominantly made of a plastic material.

2) It comprises a narrower profile at its top portion relative to its bottom portion thus reducing the conduction heat loss of relatively hot water at the top of the tank to the relatively cold water at the bottom and conveniently allowing room for insulation around the top portion.

3) It comprises one or more helical heat exchangers (helical tubes) inside the tank disposed generally adjacent the inner walls of the tank. A helical heat exchanger is located toward the bottom of the tank for heating cool water in the tank; or a helical heat exchanger is located toward the top of the tank so that fluid in the heat exchanger tube is heated by hot water in the tank; or both. 4) It is made by extrusion blow molding, which is a simple and inexpensive production method.

5) It is formed as an essentially closed unit with only small openings.

6) It is light weight, corrosion resistant and provides relatively good insulation.

7) One or two metal helical or coiled water heating tubes can be installed in the tank, even though the tank is an essentially closed tank. This installation can be installed via an opening in or adjacent an end cap of the tank and by threading the helical tube until its end exits the tank' s cylindrical shell via an aperture therein.

8) When it is used in conjunction with a solar collector, a lower heat exchanger (helical tube) in the tank can be used to heat the water stored in the tank. Such a design is useful for climates where the tank is susceptible to freezing. 9) Fresh water is heated in the upper heat exchanger thereby separating this hot water for consumption from water in the tank. Thus, the hot water can be used for drinking or cooking since this water is not contaminated with substances dissolved in the tank water.

10) It typically includes a generally cylindrical or sleeve-like partition (typically also plastic) disposed therein, slightly inboard of the heat exchanger tube(s) and spaced apart from the bottom and top of the tank to allow for water circulation. The partition helps define an annular space where the heat exchanger tube(s) are located. This configuration produces convective flow (hot water rises in the annular space and cold water descends within the inner volume of the partition), thereby improving the heat transfer between the heat exchanger helical tube(s) and water in the tank, resulting in a better thermal performance of the heat exchanger (and a solar collector if associated therewith). The heated water will flow directly to the upper portion of the tank without mixing with the water in the tank that is located within the partition, producing a thermo-siphon flow where the cold water flows down the center of the tank. Moreover, there will be a relatively limited cross- sectional annular space thereby increasing the water flow rate which improves the heat transfer efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood upon reading of the following detailed description of non-limiting exemplary embodiments thereof, with reference to the following drawings, in which:

Fig. IA is an isometric side view of a typical prior art water heater tank ; and Fig. IB shows a top view of the tank of Fig. IA with the tank's top end cap removed;

Fig. 2 is a schematic side sectional view of an embodiment of a heater tank of the present invention;

Fig. 3 is an enlarged view of area B of Fig. 2 to show better detail of a tank recess designed to provide easy installation of a heat exchanger tube; and

Fig. 4 is a schematic side sectional view of additional embodiment of the present.

DESCRIPTION OF EMBODIMENTS THE INVENTION Fig. IA depicts an isometric side view of a typical prior art barrel- shaped water heater tank 100 (shown without insulation for clarity); and Fig. IB shows a top view of the tank with the tank's top end cap removed, whereby the tank's helical water heater tube 112 is visible. Water heated by liquid in tank 100, typically also water, flows through helical tube 112. Water flowing through helical tube 112, which is commonly made of copper or a copper alloy, can be used for domestic or commercial use.

Tank 110 has a cylindrical shell 114 and top and bottom end caps 116 and

118, respectively. During assembly of tank 110, helical tube 112 is disposed within cylindrical shell 116 and end-caps 116, 118 are then welded to the shell to close the tank. Helical tube 112 is coiled essentially parallel to the walls of cylindrical shell 114 and is connected (e.g. by an elbow, welded, etc.) at one end to an inlet pipe 120 and to an outlet pipe 122 at the helical tube's other end. Pipes 120 and 122 typically are attached perpendicularly to helical tube 112 and thus the inlet and outlet pipes exit/enter tank 110 essentially perpendicularly to the wall of cylindrical shell 114. Tank 110 may comprise a heating means such as an electric heating element 124.

Fig. 2 shows an embodiment of a heater tank 10 of the present invention comprising upper and lower helical heat exchanger tubes 12a and 12b. Tank 10 is preferably made of a plastic material and more preferably the tank is formed via an extrusion blow molding process. As such, the tank's cylindrical shell 14 and upper end cap 16 and lower end cap 18 can all be integrally formed.

Tank 10 further comprises a top helical tube introduction recess 30a and a bottom helical tube introduction recess 30b comprising apertures 32a and 32b, respectively, via which a helical tube 12a and a helical tube 12b, for carrying a fluid (e.g. water) to be heated or to heat a fluid (e.g. water) in the tank, can be inserted into the tank 10 upon assembly. According to some embodiments, tank 10 includes, instead of or in addition to heater tubes 12a or 12b, a heating mechanism typically an electrical heating element 33 (Fig. 4), preferably disposed within a heating element sleeve 24.

According to other embodiments, additional features of the tank include a hot water passage 56 for upwardly leading water heated by electrical heater 33 (if any); and/or a cold water passage 60 for directing cold water downward into heating element sleeve 24.

Fig. 3 provides an enlarged view of top inlet recess 30a, which is exemplary of recess 30b as well, and for simplicity, only recess 30a will be described. Although recess 30a can be configured in a variety of ways, according to the present embodiment, this recess is defined by a first essentially vertical surface 34, generally perpendicular to both cylindrical shell 14 and end cap 16, and having a lower edge 36; a second essentially vertical surface 38 generally parallel to cylindrical shell 14, and having a lower edge 40; and an essentially horizontal surface 42 having a first edge 44 meeting with lower edge 36 and a second edge 46 meeting with lower edge 40. Thus, the three surfaces 34, 38 and 42 are essentially mutually orthogonal to each other. Vertical surface 34 has inlet aperture 32a therein.

Reverting to Fig. 2, for each inlet recess 30a and/or 30b, tank 10 also includes an outlet recess 48a and/or 48b, respectively. These outlet recesses 48a, 48b can be designed analogously to inlet recesses 30a, 30b, however, further including an upper horizontal surface 50a and/or a lower horizontal surface 50b, respectively. According to some preferred embodiments, tank 10 further comprises a partition 52, typically cylindrical, which, together with cylindrical shell 14, defines an annular space 54 where helical tubes 12a and/or 12b reside. The existence and design of the recess(es) 30a, 30b (each with an aperture

32a, 32b in first essentially vertical surface 34, allows helical heat exchanger tubes 12a, 12b to be installed from the outside of tank 10 via those aperture(s) by spiraling the tubes into annular space 54 defined by partition 52 and the shell.

Fig. 4 illustrates further embodiments of the tank wherein it comprises a relatively small profile upper portion 62a and a relatively large profile lower portion 62b. Surrounding upper portion 62a is a relatively thick insulation layer 64a and surrounding lower portion 62b is a relatively thin insulation layer 64b. The tank 10 is housed by an outer housing 66, for outdoor protection. Such a dual diameter tank can be relatively conveniently produced using extrusion blow molding. The smaller profile of the tank's upper portion 62a results in a reduced surface area for heat loss and more space for insulation layer 64a around the hotter water which would tend to otherwise be more rapidly cooled by the environment. The tank also typically includes a thermostat 68. Further shown is a tank water inlet leg 70, for example, for carrying hot water from an associated solar collector (not shown); and a tank water outlet leg 72 for returning water to the solar collector.

It should be understood that the above description is merely exemplary and that there are various embodiments of the present invention that may be devised, mutatis mutandis. For example, any or all of recesses 30a, 30b, 48a and 48b can be designed as projections rather than recesses, mutatis mutandis. Thus, features described in the above-described embodiments may be used separately or in any suitable combination; or the invention can be devised in accordance with embodiments not necessarily described above.

Claims

1. A heater tank comprising: a shell; an upper and a lower end cap positioned at upper and lower ends, respectively, of said shell; one or more helical heat exchanger tubes substantially disposed within said tank; a heating mechanism; and at least one set of heat exchanger tube introduction and exit apertures, one set for each helical heat exchanger tubes, the apertures adapted for the helical heat exchanger tube(s) to pass therethrough, wherein introduction and exit apertures are substantially parallel to the wall of the shell.

2. A heater tank according to claim 1, wherein its shell and end caps are integrally formed of a plastic material.

3. A heater tank according to claim 2, wherein the shell and end caps are made using an extrusion blow molding process.

4. A heater tank according to claim 1, wherein each tube introduction and exit aperture is disposed in a recess in, or projection projecting from, the tank and the recess with the introduction aperture abuts or is adjacent an upper or lower end cap of the tank.

5. A heater tank according to claim 4, wherein the recess or projection abutting or adjacent an end cap is defined by: a first essentially vertical surface having said aperture therein; an essentially horizontal lower surface; and a second essentially vertical surface, the surfaces abutting or intersecting each other.

6. A heater tank according to claim 1, further comprising a generally cylindrical partition fitted within the shell and substantially parallel thereto the partition being spaced apart from the bottom and top of the tank to allow for water circulation whereby a space is defined between said partition and the shell within which the helical heat exchanger tube(s) are disposed.

7. A heater tank according to claim 1, wherein the heating mechanism comprises an electric heating element.

8. A heater tank according to claim 1, wherein the heating mechanism comprises a heat exchanger tube for carrying a hot fluid.

9. A method of producing a heater tank comprising: providing a generally barrel-shaped tank with: a shell; an upper and a lower end cap positioned at upper and lower ends, respectively, of said shell; at least one helical heat exchanger tube disposed in the tank and entering and exiting from the tank; and a pair of apertures for each helical heat exchanger tube, to pass in and out there-through, said apertures being generally perpendicular to the walls of said shell and one aperture of each pair of apertures being adjacent one of said upper or lower end caps; and spirally inserting said helical heat exchanger tube through said aperture(s) at or adjacent one of said upper or lower end caps and out the other aperture of said pair of apertures.

10. A method of producing a heater tank according to claim 9, wherein providing a generally barrel-shaped tank entails using an extrusion blow molding process.