IE86663B1

IE86663B1 - Hot water storage cylinder

Info

Publication number: IE86663B1
Application number: IE20110386A
Authority: IE
Inventors: Bern Costello Cassells Jason
Original assignee: Warmflow Eng Company Ltd
Priority date: 2010-08-31
Filing date: 2011-08-30
Publication date: 2016-06-15
Also published as: GB2483228A; IE20110386A1; GB201014370D0; GB2483228B

Abstract

The present invention relates to a hot water storage cylinder comprising a single-piece plastic cylinder and one or more circumferential heating coils, the single-piece cylinder being formed without internal welds such that it is internally crevice-free. In one embodiment, the thickness of one or more parts of the cylinder body may be different to the thickness of one or more other parts of the cylinder body. In another embodiment, on or more of the heating coils is helically wound around a circumference of the cylinder body. In another embodiment, the cylinder body includes or more tracks in its outer surface to locate or help locate the or each heating coil around its circumference. <Figure 2>

Description

Hot Water Storage Cylinder The present invention relates to a hot water storage cylinder, particularly but not exclusively a pressurised hot water cylinder, and to a process for making same.

Currently, pressurised hot water cylinders, designed to heat up and store a body of water for local domestic or small commercial use, are formed by welding the body of a metal cylinder with a base and top plate around one or more internal heating coils to form a closed cylinder. The cylinder is formed of metal and welded in order to have sufficient strength to withstand the expected pressure and pressure changes therein. However, this requires a certain amount of welding and finishing to form, and the welding leaves possible weak spots for any corrosion to start. As much of the welding is internal, any defect cannot be seen within the closed or sealed cylinder once formed. Any such corrosion will naturally affect product lifetime, and lead to potentially catastrophic leakage without warning once the corrosion is sufficiently advanced.

It is an object of the present invention to provide an improved hot water storage cylinder that overcomes one or more of the above disadvantages.

Thus, according to one aspect of the present invention, there is provided a hot water storage cylinder comprising: a single-piece plastic cylinder body, and one or more circumferential heating coils; wherein the cylinder body includes one or more tracks in its outer surface to locate or help locate a heating coil around its circumference.

In this way, a single piece plastic cylinder body does not comprise any welds or welding with their potential weak spots for corrosion start, in particular internally within the cylinder body, such that it is internally 'crevice-free’.

The avoidance of welds or welding also reduces the time and costs for making such a cylinder body, as well as only requiring a plastics material to be shaped in a single processing step, rather than metals and metal pieces to be formed and joined. Furthermore, with the heating coils located circumferentially, any weakness therein can be more easily viewed and/or accessed for repair or replacement.

The cylinder is generally intended for use in a pressure or pressurised internal environment, generally a pressure above ambient pressure, such as in the range 3-15 bar.

The cylinder body is preferably a closed cylinder body. The cylinder may include one or more ports, for example for servicing and for the entry and exit of one or more fluids.

The cylinder body may have any suitable shape, size and dimensions. Generally, the cylinder body is cylindrical and/or has a cylindrical portion, although the present invention is not limited thereto, and may have a cross-sectional radius of several millimetres up to hundreds or thousands of millimetres. Generally, the cylinder body has a defined end at each end of the cylindrical portion, optionally being a ‘top’ or ’cap’ and a ‘base’. Such end portions may be flat or curved or have a particular desired shape, and are formed integrally with the cylindrical portion to form the cylinder body in a single processing step. The general shapes, sizes and designs of hot water storage cylinders are known in the art, and are well known domestically and for industrial use where a local source of hot water is desired to be stored for local use.

The thickness of one or more parts of the cylinder body may be different to the thickness of one or more other parts of the cylinder body. In particular, the thickness of the cylindrical portion may vary in line with the location of a heating coil therearound. For example, the wall thickness of the cylindrical portion may be thinner such as 1-3mm where heat transfer is intended from a heating coil to the content of the cylinder body, and thicker such as 3-1 Omm where not, and/or where the outer surface of the cylindrical portion is adapted to assist location/support/insulation of a heating coil.

Other thickness variations may be required or desired to provide strength, rigidity, must fit or match portions with other items in use, etc.

The cylinder body may be formed by a number of processes able to form a single-piece body. These include various moulding processes including injection moulding and rotational moulding.

Rotational moulding is a process that is mainly used for making hollow plastic products. It can be used to produce a wide range of products with highly desirable characteristics and shape, and is relatively inexpensive when compared to other thermoplastic moulding processes. The process was developed in the 1940s, and since then it has been shown that a wide range of thermoplastics can be moulded in this way. Polyethylene (PE) is the main polymer used in rotational moulding, accounting for about 90% of products made by the process.

The plastic of the cylinder body may be one or more polymers, plastics or plastic-based materials known in the art, including but not limited to one or more of the group comprising: polyolefins. The term “polyolefin” is well known in the art, and includes polyethylene (PE), polypropylene (PP), polybutylene, etc.

The cylinder body can have at least two different layers. The process allows the multi-layering to be any number of layers as desired or necessary. The depth of each layer depends upon the desired properties of the final product. ‘Standard’ PE is an inexpensive raw material, such that the PE would generally form the majority of the thickness of rotomoulded products. It is known that the stiffness of a layer is proportional to the thickness of material cubed, so doubling the wall thickness increases the stiffness by a factor of 8.

The or each heating coil may be formed of any suitable material, including metal and heat-resistant plastics or a combination of same, preferably metals such as cooper or steel.

According to one embodiment of the present invention, there are 2, 3 or 4, preferably 2, heating coils circumferentially located around the plastic cylinder body. In this way, heat energy to heat the liquid, generally water, inside the cylinder body can be provided from 2 or more sources being the same or different. Such sources include but are not limited to the group comprising: boilers such as oil-fired boilers and gas-fired boilers, solar panels, fires, heating systems, heat recovery systems, cookers, or a combination of same. For example, a hot water cylinder may be heated by one heating coil connected to a solar panel, and by another heating coil connected to an oil or gas-fired boiler.

Two or more heating coils may be operated or operable independently, or in a coordinated manner, particularly to most efficiently and/or economically compliment each other in heating liquid within the cylinder to the desired temperature.

Two or more such heating coils may be separately located around the plastic cylinder body, or may overlap at one or more portions or locations thereof.

The heating coil(s) may be located in any suitable pattern or direction around the circumference of the plastic cylinder body so as to transfer heat therefrom through the plastic cylinder body to the liquid therein. The shape and circular path of one or more of the heating coils may be irregular; preferably they are regular.

According to one embodiment of the present invention, one or more of the heating coils is helically wound around a circumference of the plastic cylinder body.

The helical winding of a coil around a generally cylindrical cylinder may also allow such a heating coil to provide some degree of strength and/or rigidity to the plastic cylinder body, especially where the cylinder is for use in a pressure or pressurised internal environment. This may also allow the thickness of the cylinder body to be reduced in one or more locations.

A portion of the outer surface of the cylindrical body could include one or more ridges, grooves, ruts or furrows, within which a portion of a heating coil could be located.

The inclusion of one or more recesses may also assist contact between the heating coil and the cylinder body to improve heat transfer between them.

Either as part of the inclusion of one or more recesses, or otherwise, the thickness of the cylinder body may vary along its length, particularly to best locate and arrange each transfer with the one or more heating coils.

The or each heating coil may be located wholly or substantially around the outer surface of a portion of the cylinder body.

Alternatively and/or additionally, one or more heating coils may be located wholly or substantially within the outer wall of the cylinder body, such that the term “circumferential as used herein includes passing around the circumference of the cylinder body, whether such circumference is within or beyond the wall and/or outer surface of the cylinder body, but still with the or each heating coil adjoining the cylinder body for best heat transfer between them.

The inner surface of the wall of the cylinder body may be based or adapted on the basis of the shape of the outer surface, but is preferably flat and/or smooth. The outer surface of the wall of the cylinder body may be adapted to wholly or substantially cover the or each heating coil to secure best heat transfer.

The cylinder of the present invention may also include one or more insulators around the cylinder body and heating coil(s), optionally an insulated outer housing, preferably providing a reduction or restriction of heat energy from the or each heating coil away from the cylinder body.

Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a side view of a first cylinder body and outer coil of the present invention; Figure 2 is a perspective view of Figure 1; and Figure 3 is a perspective view of Figure 2 with the addition of an outer insulated jacket.

Referring to the drawings, Figure 1 shows a hot water storage cylinder 2. Generally, the cylinder 2 is elongate, having a possible but non-limiting diameter in the range 400-500mm, and a possible but non-limiting height of 500-2000mm. Cylinders formed with such a cylindrical body are known in the art to have a capacity of tens, hundreds or possibly even thousands of litres.

The cylinder 2 comprises a single-piece plastic cylinder body 4 and two circumferential heating coils 6, 8.

The example of the plastic cylinder 4 shown in Figure 1 is formed to be elongate and of a generally regular cylindrical body portion, having a rounded base 10 and a top or cap 12 integrally formed with the intervening cylindrical body portion to form the overall cylinder body 4. The base 10 and cap 12 may have other shapes or designs.

The cylinder body 4 is formable by a number of processes, generally moulding processes, and a formation of the cylinder body 4 by rotational moulding is particularly described.

Rotational moulding can be a relatively high temperature and low pressure forming process that uses heat and one or mould rotations to form usually hollow, single or one-piece products. Generally, a measured quantity or ‘shot’ of polymer, usually in powder form, is added into the mould, and the mould is heated in an oven while it rotates, generally through two axes, which can be at different speeds, in order to avoid the accumulation of the polymer powder in any one particular location in the mould. With this evenness of distribution and the heating, the polymer grains melt and coalesce around the internal surfaces or walls of the mould so as to take the internal mould shape. After this processing step, the mould is usually cooled such that the polymer then solidifies and usually at least partially shrinks so as to be separate from the mould. The final product is then removed from the mould interior once the cooling has concluded.

Each stage of the moulding process, in particular the ramp times and dwell times for heating and cooling, as well as the speeds of rotation, can affect the moulding process, and the person skilled in the art is aware of such variables which are not further described herein.

As mentioned above, polyethylene (PE) is the most common material used in rotational moulding. There are many grades or types of polyethylene, and one or more additives can be provided to the polymer material to assist the moulding process and/or final product properties or parameters. Again, the skilled person is aware of the types of plastics and plastic recipes that can be used in rotational moulding, and the variations provided thereby.

A particular advantage of rotational moulding is the ability to vary wall thicknesses, and/or achieve an outer surface of a finished product exactly as desired.

Figure 1 shows the cylinder body 4 having a service port 14 and entry and exit ports 16 positioned in the cap 12, and integrally formed with the remainder of the cylinder body 4.

Thus, a single-piece plastic cylinder body 4 is formable having no joins, in particular welds, which can be a potential weakness to start corrosion.

The two heating coils 6, 8 shown in Figure 1 may be made of the same material such as copper or steel, or may be formed of two different materials, in particular where they are provided for different purposes.

Figure 1 shows a first or top heating coil 6 located around an upper part of the cylinder body 4, and second or lower heating coil 8, being longer but having the same circumferential dimension as the top heating coil 6.

Each of the heating coils 6, 8 are helical around and preferably helically wound around the cylinder body 4. The helical winding allows ease of locating each coil 6, 8 around the cylinder body 4, optionally in a screw fashion.

The helical winding also provides an evenness of strength from the coils 6, 8 to the cylinder body 4. Thus, the overall integrity of the cylinder of the present invention can be achieved by at least some of the strength required of the walls of the cylinder 2 being provided or supported by the heating coils 6,8. In this way, the thickness of the wall of the cylinder body 4 can be adapted, such as shaped and/or thinned, on the basis that some of the strength required of the cylinder wall to withstand any internal pressure, particularly in a pressurised water system, can be borne by the heating coils 6, 8.

Figure 1 also shows the wall of the cylinder body 4 having a regular helical groove 18, which can be easily formed in the outer surface of the wall during forming of the cylinder body 4. The groove 18 has a complimentary cross section to the cross section of the heating coils 6, 8 for several reasons. Firstly, to provide a particularly convenient housing or nesting of the heating coils 6, 8 around the cylinder wall. Secondly, to increase the efficiency and/or amount of heat transfer from the heating coils 6, 8 to the cylinder body 4, and hence to the content of the cylinder 2. Thirdly, to provide an easy fitting arrangement for the heating coils 6, 8, by their helical addition into the grooves 18 from one end of the cylinder body 4.

In practice, the first heating coil 6 could be connected to a first source of heating fluid, such as heated water from a boiler or heating panel or the like, and the second heating coil 8 could be connected to a separate or associated or the same heating source, such as a separate boiler. Each heating coil 6, 8 transfers heat energy from a heating fluid, such as water, therein, through the cylinder wall, and into the content of the cylinder 2.

The entry and exit ports for each of the heating coils 6, 8 may be in an aligned fashion on one side on the cylinder body 4 for convenience of fitting.

Figure 2 shows a perspective view of the cylinder 2 of Figure 1.

Figure 3 shows an insulating outer body 22 around the cylinder body 4 and heating coils 6, 8, in particular an insulated outer housing, able to reduce undesired flow of heat energy from the heating coils away from the cylinder body.

As well as an insulating outer body 22, one or more other covers or covering layers could be added around the heating coils 6, 8 to increase their insulation, and/or strength in relation to the overall cylinder 2. Where further layers are added, particularly covering the heating coils 6, 8, the skilled man can see how the cylinder wall can be adapted to wholly or substantially surround the heating coils, such that the heating coils 6, 8 can be seen as being more than around the outer wall of the cylinder, and progressing to being within the outer wall of the cylinder.

Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined in the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments.

Claims

1. A hot water storage cylinder comprising: a single-piece plastic cylinder body, and one or more circumferential heating coils; wherein the cylinder body includes one or more tracks in its outer surface to locate or help locate a heating coil around its circumference.

2. A cylinder as claimed in claim 1 wherein the cylinder body is inherently crevice free.

3. A cylinder as claimed in claim 1 or claim 2 being a pressure or pressurised cylinder.

4. A cylinder as claimed in claim 3, for a pressure in the range 3-15 bar.

5. A cylinder as claimed in any one of the preceding claims wherein the cylinder body includes one or more ports.

6. A cylinder as claimed in any one of the preceding claims wherein the cylinder body is formed in a single processing step.

7. A cylinder as claimed in any one of the preceding claims wherein the thickness of one or more parts of the cylinder body is different to the thickness of one or more other parts of the cylinder body such that the thickness of the cylindrical portion varies in line with the location of a heating coil therearound.

8. A cylinder as claimed in any one of the preceding claims wherein the cylinder body is formed by injection moulding.

9. A cylinder as claimed in any one of claims 1-7 wherein the cylinder body is formed by rotational moulding.

10. A cylinder as claimed in any one of the preceding claims wherein the plastic of the cylinder body is a polyolefin.

11. A cylinder as claimed in claim 10, wherein the polyolefin is polyethylene.

12. A cylinder as claimed in any one of the preceding claims wherein comprising 2, 3 or 4 heating coils circumferentially located around the plastic cylinder body.

13. A cylinder as claimed in any one of the preceding claims wherein one or more of the heating coils is helically wound around a circumference of the plastic cylinder body.

14. A cylinder as claimed in any one of the preceding claims .wherein a portion of the outer surface of the cylindrical body includes one or more ridges, grooves, ruts or furrows.

15. A cylinder as claimed in any one of the preceding claims wherein the thickness of the cylinder body varies along its length.

16. A cylinder as claimed in any one of the preceding claims wherein the or each heating coil are located wholly or substantially around the outer surface of a portion of the cylinder body.

17. A cylinder as claimed in any one of the preceding claims wherein one or more heating coils are located within the outer wall of the cylinder body.

18. A cylinder as claimed in any one of the preceding claims wherein the inner surface of the cylinder body is flat and/or smooth.

19. A cylinder as claimed in any one of the preceding claims wherein 10 the cylinder includes one or more insulators around the cylinder body and heating coil(s).

20. A cylinder as claimed in claim 19, one or more insulators is an insulated outer housing.

21. A cylinder as claimed in any one of the preceding claims being elongate and having a diameter in the range 400-500mm, and a height in the range 500-2000mm.