GB2084312A

GB2084312A - Apparatus and Method for Avoiding the Bursting of Conduits

Info

Publication number: GB2084312A
Application number: GB8128270A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-09-22
Filing date: 1981-09-18
Publication date: 1982-04-07
Also published as: AU7541281A; JPS5785434A

Abstract

A method and apparatus for avoiding burst conduits by freezing wherein flanges (26) are provided on pipes (24) as heat dissipating members. The flanges are tapered to provide a small heat dissipating gradient from the wide end to the narrow end. The preferred embodiment is used in a solar heat collector. When the pipe is subjected to freezing temperatures the working fluid freezes in the pipe from the point where the flange is the widest to the point where it is narrowed. Ice expands out of one end of the conduit instead of bursting it. In a solar panel ice can be allowed to expand out of the panel into insulated parts of the associated water system. <IMAGE>

Description

SPECIFICATION Apparatus and Method for Avoiding the Bursting of Conduits This invention relates to an apparatus and method for avoiding the bursting of conduits.

More particularly this invention relates to a method and apparatus for avoiding the bursting of pipes in solar energy collectors.

It is known that conventional solar water heaters are subject to damage when exposed to temperatures below the freezing point of the working fluid in the collector. Conventional methods for overcoming this probelm involve either providing expensive insulation or else draining of the collector at night when bursting, owing to freezing, usually occurs.

It is an object of this invention to go some way towards overcoming this disadvantage or at least to offer the public a useful choice.

Accordingly the invention may be said broadly to consist in a method of avoiding a burst conduit under freezing which method comprises providing said conduit with differential heat extracting means associated therewith in a heat conducting relationship, which heatr extracting means allows dissipation of hear from a first end of said conduit faster than from a second end thereof, whereby freezing occurs progressively from said first end to said second end and expansion due to freezing occurs out of said second end.

Preferably said liquid is water.

Preferably said conduit is a pipe.

Preferably said pipe is one in a solar water heat.

collector.

In another embodiment the invention may be said broadly to consist in apparatus for avoiding the bursting of a conduit under freezing, which apparatus comprises a conduit and differential heat extracting means associated therewith in heat conducting relationship, which heat extracting means allows dissipation of heat from a first end of said conduit faster than from a second end thereof, the arrangement being such that in use freezing occurs progressively from said first end to said second end and expansion due to freezing occurs out of said second end of said conduit.

Preferably said conduit is a circular pipe and said heat extracting means comprises a flange extending radially outwardly from said pipe, said flange being tapered with respect to the longitudinal axis of said pipe and being widest at said first end of said pipe.

Preferably said flange projects radially outwardly in the manner defined immediately above from the opposite sides of said pipe.

Preferably said pipes are arranged in parallel in a solar heat collector, alternative flanges having their wide ends at opposite ends.

Preferably said pipes are cross flow pipes arranged in parallel in a solar heat collector and said flanges all taper towards the same end of said collector.

Preferably the header pipes in a said solar water collector are also provided with flanges.

Preferably said flanges are out of contact with said header pipe and said cross flow pipes at the junction of each said header pipe with a said cross flow pipe.

The invention consists in the foregoing and also envisages constructions of which the following gives examples.

The invention may be more fully understood by having reference to the accompanying drawings in which Figure 1 is a top plan view of a solar collector employing pipes according to the present invention, Figure 2 is a top plan view of a solar collector which is another embodiment of the present invention, Figure 3 is a detailed view of a modified flange on an upper header pipe, Figure 4 is an alternative to the embodiment illustrated in figure 3.

The solar collector has a lower header pipe 10 and an upper header pipe 12. Lower header pipe 10 is fed by inlet pipe 14. Upper header pipe 12 discharges out discharge pipe 22.

Header 10 and inlet pipe 14 are fitted with tapered flange portions 1 6 and 1 8 respectively.

The length of the base of the flange 1 6 is 8 feet and that of flange 18 is 4 feet. The width of the flange 1 6 tapers from 6 inches to 2 inches and that of flange 18 from 2 inches to a point.

Similarly a flange 20 is provided on upper header pipe 12. The flanges may be soldered, brazed or welded or otherwise fitted provided a good heat conducting contact is made.

Crossing between header pipes 12 and 10 are a series of pipes 24 each provided with radially extending tapered flanges 26. In the embodiment of figure 1, the flanges are arranged to taper in opposite directions so as to provide a solar heat collecting surface. There is a space left between the edges of flanges 26 on separate pipes 24.

Although this gap is very narrow it provides sufficient insulation to preclude conduction between adjacent flanges.

When solar energy collector illustrated cools to below freezing at night and the water is not flowing through the header pipes or conduit freezing tends to occur. The purpose of this invention is not to avoid freezing but rather to control the direction of freezing so that expansion due to the change of phase of the water to ice occurs out of the ends of inlet 14 and outlet 22 where the expansion can be taken up without bursting the pipes. This is achieved by the provision of the tapered flanges which act as differential heat extractors. In particular the flow of heat from the water in pipe 24 occurs at a greater rate at the wide end of the flange than at the narrow end of the flange. Thus in the right hand pipe 24 of the figure freezing occurs progressively from top header pipe 22 down to bottom header pipe 10.Freezing occurs in alternative directions in each of the pipes 24 across the face of the collector.

Flanges 1 6 and 1 8 are tapered in the direction shown so that freezing occurs from the right hand end of lower header pipe 10 and up inlet pipe 14 into the source of water The expansion of the ice down pipe 14 creates a back pressure in the main feeding it but does not cause a bursting of the pipe. Similarly water freezes progressively from left to right in upper header pipe 12 and out the outlet 22 where the pressure created by the freezing can be taken out by increased pressure in the water in the pipe beyond outlet 22.

It will be appreciated that the principle of the invention lies in each individual pipe and flange sub-combination and not just in the main combination of the solar water collector.

A panel constructed as shown in figure 1 was tested in a blast freezing apparatus cooled down to --400C. It was observed that while the water froze solidly in the conduits there was no bursting or other distortion of the pipes but rather the ice emerged through outlet 22 and inlet 14 without any damage to the collector.

It has been found thatif the flanges 26 are all arranged to taper from the lower header pipe 10 to the upper header pipe 12 a more efficient operation of the invention can be effected. A gap 25 of increasing width is created by the placing of the flanges in this arrangement.

In operation, freezing in lower header pipe 10 begins at the right hand end and proceeds to the left and then upwardly up inlet pipe 14 in the direction of convergence of flange 16 towards flange 18 and the direction of convergence of flange 18 towards the upper end of inlet pipe 14.

Similarly freezing occurs in cross flow pipes 24 from lower header pipe 10 towards upper header pipe 12 and from the left hand end of upper header pipe 12 its the right hand end. Although the angle of the pipe is shown as a right angle it will be appreciated that a more curved angle provides for easier expansion of water to ice up pipe 22.

In the embodiment shown in figure 3 each of the cross flow pipes 24a, 24b, 24c, 24d and 24e flows from a bottom header pipe 10 (not illustrated) to the upper header pipe 12. Flanges 26a etc. taper towards upper header pipe 12 and a diverging gap 25a, etc. is left betweeen each of the pipes 24. It has been found that if flange 20 is simply soldered along the length of upper header pipe 22 premature freezing does tend to occur at the junction of each pipes 24a, etc. with header pipe 12. Freezing does not occur to the point of bursting but in order to counteract the problem in one preferred embodiment a cut out portion 34 as illustrate,d is provided to each side of each junction of a pipe 24 with the header pipe 12.A flange 20 is soldered along each edge 30 where it contacts header pipe 12 and is spot soldered to each pipe 24 at 32 so as to provide a thermal contact on the upper edge of pipes 24. It has been observed that the construction does allow for more even dissipation of heat so as to avoid unequal freezing at each of the junctions of each of the pipes 24 with the header pipe 12.

Shown in ghost at the right hand end of header pipe 22 is a polytetrafluoroethylene or other suitable insulating coating around a portion of the insider of the upper header tube.1 2. This coating acts as a differential insulator to further assist the cooling pattern so that heat is dissipated at the left hand end of insulator 40 quicker than at the right hand end, thus encouraging freezing to occur from left to right in figure 3.

An alternative to the flange 20 of figure 3 is the provision of a series of V shaped metal members 36. These are soldered to the edge of upper header pipe 12 and also soldered to the top edge of the junction of each of cross pipes 24 with header pipe 1 2. Their action is similar to that of flange 20 in figure 3 in that the heat is dissipated from pipes 24 out of the area of the junction with pipe 1 2 thus preventing freezing at the joint.

Shown in ghost is a wedge member 38 which cuts down on the cross-sectional area for flow of header pipe 12 thus encouraging freezing from left to right as shown in figure 4. The same effect can be achieved by providing a tapered indentation in pipe 1 2 providing an increasing cross-sectional area from left to right or alternatively by making pipe 12 conical.

In each of the embodiments it is preferred to have the flange constructed of metal of the same gauge as the piping. This again assists in the even dissipation of the heat.

While the invention has been described with particular reference to solar collectors it has application to other forms of heat exchangers where freezing of the working fluid may be a problem -- for example, car radiators.

Claims

1. A method of avoiding a burst conduit by freezing which method comprises providing said conduit with differential heat extracting means associated therewith in a heat conducting relationship, which heat extracting means allows dissipation of heat from a first end of said conduit faster than from a second end thereof, whereby freezing occurs progressively from said first end to said second end and expansion due to freezing occurs out of said second end.

2. A method as claimed in claim 1 wherein said liquid is water.

3. A method as claimed in claim 1 or 2 wherein said conduit is a pipe.

4. A method as claimed in claim 3 wherein said pipe is one in a solar water heat collector.

5. A method of avoiding a burst conduit by freezing substantially as herein described with reference to the accompanying drawings.

6. An apparatus for avoiding the bursting of a conduit under freezing, which apparatus comprises a conduit and differential heat extracting means associated therewith in heat conducting relationship, which heat extracting means allows dissipation of heat from a first end of said conduit faster than from a second end thereof, the arrangement being such that in use freezing occurs progressively from said first end to said second end and expansion due to freezing occurs out of said second end of said conduit.

7. An apparatus according to claim 6 wherein said conduit is a circular pipe and said heat extracting means comprises a flange extending radially outwardly from said pipe, said flange being tapered with respect to the longitudinal axis of said pipe and being widest at said first end of said pipe.

8. An apparatus according to claim 7 wherein said flange projects radially outwardly in the manner defined immediately above from opposite sides of said pipe.

9. An apparatus according to claim 7 or 8 wherein said pipes are cross flow pipes arranged in parallel in a solar heat collector, alternative flanges having their wide ends at opposite ends.

10. An apparatus according to claim 7 or 8 wherein said pipes are cross flow pipes arranged in parallel in a solar heat collector.and said flanges all taper towards the same end of said collector.

11. An apparatus according to claim 10 wherein said collector has an upper and a lower header pipe and said flanges taper from said lower to said upper header pipe.

12. An apparatus according to claim 11 wherein said header pipes are also provided with tapering flanges.

13. An apparatus according to claim 12 wherein said flanges are out of contact with said header pipes and said cross flow pipes at the junction of each said header pipe with a said cross flow pipe.

14. Apparatus for avoiding the bursting of a conduit under freezing substantially as herein described with reference to the accompanying drawings.