GB2117110A - Apparatus and method for avoiding bursting of conduits - Google Patents

Abstract

A solar energy collector, particularly one which uses water as a working fluid, has top and bottom header tubes 14, 16 provided with flanges 22, 24 of tapering width along the lengths of the tubes. This allows for differential dissipation of heat from the header tubes so that at night water in the header tubes freezes in a controlled manner out of the ends of the header tubes. If the header tubes have an increasing internal cross- sectional area of flow corresponding to the wide end to the narrow end of the flange the control of the direction of freezing may be enhanced. The invention may be applied to other heat exchangers in which the working fluid may freeze, such as car radiators. <IMAGE>

Description

SPECIFICATION Apparatus and method for avoiding bursting of conduits This invention reiates to an apparatus and method 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. Known methods for overcoming this problem involve either providing expensive insulation or else draining of the collector at night when bursting, owing to freezing, usually occurs.

In my United Kingdom Patent Specification 2,084,31 2A there is described and claimed an apparatus which goes some way toward overcoming this disadvantage. The present invention is an improvement on that of 2,084,31 2A as it seeks to provide a collector which is closer in construction to conventional panels but which offers the same advantages of the collector of the earlier invention.

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

Accordingly the invention may be said broadly to consist in an apparatus for avoiding the bursting of a conduit under freezing, which apparatus comprises a solar heat collecting panel having differential heat extracting means associated in heat conducting relationship with header pipes at either end of the said panel, which heat extracting means allows dissipation of heat from a first end of each said header pipe faster than from a second end thereof and cross-flow pipes in heat conducting relationship with a collector plate, the arrangement being such that in use freezing occurs progressively from said first end to said second end of each said header pipe and expansion due to freezing occurs out of said second end of each said header pipe.

Preferably said header pipes are circular and each said heat extracting means comprises a flange extending radially outwardly from each said header pipe, said flange being tapered with respect to the longitudinal axis of said pipe and being widest at said first end of said pipe, the flange being in heat conducting relationship with said cross-flow pipes passing thereby into each said header tube.

Preferably said heat extracting means includes means progressively increasing the internal crosssectional area of each said header pipe from said first and the said second end..

Alternatively said differential heat extracting means comprises a flange extending along one edge of each said header pipe in heat conducting relationship therewith and with each said crossflow pipe leading into each said header pipe, and heat insulating means providing progressively increased heat insulation over each said header pipes from said first end to said second end thereof.

The invention will now be described further, by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of a single solar heat collecting panel according to the invention in an insulating casing, Figure 2 is the view Il-Il shown in Figure 1, Figure 3 is the sectional view Ill-Ill shown in Figure 1, Figure 4 is a fragmentary sectional view of a lower header pipe and a cross-flow tube and flange according to a second embodiment of the invention.

Figure 5 is a connecting joint for use in joining pairs of solar panels, Figure 6 is a view of a portion of an alternative to the embodiment illustrated in Figure 1.

In United Kingdom Patent Specification 2,084,31 2A there is described a solar heat collecting panel which employs the principle of the differential dissipation of heat in order to control freezing in solar panel collectors. In that specification a solar heat collecting panel is shown in which each of the cross-flow pipes has associated therewith a flange which tapers in width to allow the differential dissipation of heat along each cross-flow pipe. I have now found that a solar heat collecting panel which has differential heat dissipating flanges on each of the header pipes only can control freezing to avoid bursting of pipes in solar heat collectors even though the cross-flow pipes are provided with a single heat collecting sheet.It will be seen that this allows the manufacture of solar heat collectors embodying the differential heat dissipation principle to be simplified resulting in reduced costs.

The solar water heating collecting apparatus is given the general designation 10. The apparatus comprises a side frame 12 on a backing 13.

Conventional insulation 11 is provided inside of backing 13 if backing t3 does not provide sufficient insulation. Preferably backing 1 3 is of an insulating material.

The solar collecting panel itself consists of upper and lower header tubes 14 and 1 6 respectively of, for example, 32 mm tubing and cross-flow tubes 30 of, for example, 13 mm tubing. Tapered flanges 22 and 24 are affixed to header tubes 1 4 and 1 6 respectively. Preferably these flanges are soldered along their length but any suitable fixing in heat conducting relationship to the header tube will enable the practice of the invention. Similarly flanges 22 and 24 are soldered or otherwise joined in heat conducting relationship to crossflow pipe 30. Preferably the flanges are constructed of 20 gauge copper. Each of flanges 22 and 24 has a width of 75 mm at the narrow end of the taper and 1 50 mm at the broad end.

The left hand ends of header tubes 14 and 1 6 respectively are held down by retaining pieces 1 8 and 20. The right hand ends are held in position by ends 32 and 34 passing through side 33.

A copper sheet 26 which is a preferred embodiment is 1100 mm by 1140 mm has pressed out a series of bulges 28 which have an inner diameter to receive each of the cross-flow pipes 30. The cross-flow tubes 30 are preferably continuously soldered onto the plate 26 as may be seen from Figure 3. The copper plate 26 is preferably 34 gauge. It will be seen that the difference between the collector illustrated Figure 1 and a conventional collector is that the collector 26 is somewhat shorter than a conventional collector while flanges 22 and 24 are present.

In a preferred embodiment of the invention, in header pipe 14 there is provided a conical solid element 1 5 while in header tube 1 6 there is a conical solid element 17. Each of these elements reduces the cross-sectional area available for water flow in each of the header tubes from the left hand end to the right hand end as viewed in Figure 1. It will be seen that the narrowest crosssectional area is at the same end as the end of the flange having the greatest area thus providing for maximum dissipation of heat with minimum volume of water to assist in ensuring that freezing occurs from the left hand to the right hand end of header tubes 14 and 16. Elements 1 5 and 1 7 are helpful but not essential to the invention.

Referring to Figure 2 the header tubes 14 and 16 rest in rubber bungs 36 and 42 at either end thereof to avoid contact with the casing. A glazing of poly-carbonate 38 is provided. In extreme climates double glazing may be provided. A spacer piece 40 is also provided across the centre of the panel to space the glazing from the collector plates. Preferably this spacer 40 is insulated.

Referring to Figure 4 header tube 1 6A is provided with a tapered pressed in portion 19 extending progressively from one end of header tube 1 6A to the other. This achieves the same object as the provision of the conical element 1 7 shown in the portion of the Figure 1 in which header tube 1 6A has been broken away.

In Figure 5 there is shown a connector joint having arms 44 and 46 leading to a common tube 48. Tube 44 may be joined to either threaded end 32 or threaded end 34 of header tubes 1 6 and 14 respectively. The radiused corners of tubes 44 and 46 allow for expansion owing to freezing out of ends 34 and 32 and corresponding tubes in another collector which is the mirror image of that shown in Figure 1.

In operation the panel 10 illustrated in Figure 1 is mounted to face the sun in the manner of conventional solar panel heaters. Cold water or other working fluid enters end 32, passes along header tube 16 and rises up tubes 30. The heated water passes out end 34. This panel can be used in a conventional thermosphon or in a conventional pump assisted system. When the panel is not receiving radiation and temperatures fall to below the freezing point of the working fluid freezing working fluid out of the two header pipes end to the right hand end of header tubes 14 and 1 6. Freezing in cross-flow tubes 30 will progress into either of the header tubes but it has been observed that there is sufficient flow of the freezing working fluid our of the two header pipes 16 and 14 that bursting of the cross-flow tubes 30 is avoided.

In the embodiment illustrated in Figure 6 the differential dissipation of heat is achieved through the use of insulation of varying effectiveness. The embodiment illustrated is the bottom portion of the panel of Figure 1 with flange 24 replaced by a flange 25 of constant width. Flange 25 is in heat conducting relationship with header pipe 16 and with cross-flow pipes 30 by means of a continuous solder or the like. Insulation 27 in the form of, for example, an insulating foam is provided within casing 12 of tapering width from the side of casing 12 partially encasing header pipe 1 6. The right hand end of header pipe 1 6 is fully encased with the maximum insulation while the left hand end is uncovered. The provision of flange 25 assists in the dissipation and freezing process. The direction of freezing corresponds to the direction of increased insulation.

In each of the embodiments it is preferred to have the flange constructed of metal of the same guage 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 fluids may be a problem -- for example, car radiators.

Claims (7)

1. An apparatus for avoiding the bursting of a conduit under freezing, which apparatus comprises a solar heat collecting panel having differential heat extracting means associated in heat conducting relationship with header pipes at either end of the said panel, which heat extracting means allows dissipation of heat from a first end of each said header pipe faster than from a second end thereof and cross flow pipes in heat conducting relationship with a collector plate, the arrangement being such that in use freezing occurs progressively from said first end to said second end of each said header pipe and expansion due to freezing occurs out of said second end of each said header pipe.

2. The apparatus according to claim 1 wherein each said header pipe is circular and said heat extracting means comprises a flange extending readially outwardly from each said header pipe, said flange being tapered with respect to the longitudinal axis of said pipe and being widest at said first end of said pipe, the flange being in heat conducting relationship with said cross-flow pipes passing thereby into each said header tube.

3. The apparatus according to claim 2 wherein said heat extracting means progressively increasing the internal cross-sectional area of each header pipe from said first end to said second end.

4. Apparatus according to claim 3 wherein said means progressively increasing the internal crosssectional area of each said header pipe comprises a conical insert in said header.

5. Apparatus according to claim 3 wherein said means progressively increasing the internal crosssectional area of each said header pipe comprises shaping each said header pipe to have an increasing cross-sectional area.

6. Apparatus according to claim 1 wherein said differential heat extracting means comprises a flange extending along one edge of each said header pipe in heat conducting relationship therewith and with each said cross-flow pipe leading into each said header pipe, and heat insulating means providing progressively increasing heat insulation over each said header pipe from said first end to said second end thereof.

7. A solar heat collecting panel substantially as herein described with reference to and as illustrated in the accompanying drawings.