AU2011349100B2 - A thermal expansion joint or conduit - Google Patents

Abstract

In order to provide a compact thermal expansion joint or conduit for a solar collector panel array, the expansion joint or conduit (2.002) includes a tube formed into one or more curves (2.024, 2.026, 2.028), to adsorb movement of the collector headers due to thermal expansion, the tube being a helical or corrugated tube enabling the curves to be compact and smaller than the minimum bending radius of a smooth tube.

Description

WO 2012/083337 PCT/AU2011/000717 1 A Thermal Expansion Joint or Conduit Field of the invention [001] This invention relates to thermal expansion joints or conduits for pipes and the like. [002] The invention is particularly suited for joining heat transfer fluid circuits in multiple solar collector arrays. Background of the invention [003] In commercial solar water heating systems, solar thermal collectors can be arranged in groups. A large system may typically comprise rows of collectors forming a sub-array (for example, up to eight collectors), connected to an adjacent sub-array, forming a system array (say 24 collectors), in a single row of a large multiple row solar thennal system. These sub-arrays are fixed to rooves or frames with limited or no means of moving laterally relative to an adjacent sub-array. Solar hot water system collectors typically have header tubes along the top and bottom of a header/riser solar thermal collector. The header pipes of each sub-array are connected to the header pipe of the sub-array beside it. [004] The solar collectors can reach temperatures of the order of 150 0 C due to stagnation temperatures in the collectors. Due to thermal expansion, each eight collector sub-array can expand and contract by about 30mm measured across the outlets of the combined headers. This is a cycling change in length as the solar energy increases and decreases during the day and night. [0051 In known systems, the connections between the arrays have been made with flexible hoses made of an elastomeric plastic with a metallic braided pressure restraining sleeve. Due to the pressures and high temperatures of solar hot water, these hoses can be problematic. [0061 An alternative is an "omega" or lyre shaped thermal expansion compensation tube, usually in copper. These tubes must be long and bent through a large radius (typically 370mm for 20mm diameter tube subject to 30mm deflection) to avoid cyclic load induced fatigue failures. This is discussed, for example, in the standard AS/NZS 3500.4:2003 Fig.4.4. This large layout requires that the arrays be spaced further apart, taking up roof area. [007] Larger full loop alternatives can contain air-locks.

WO 2012/083337 PCT/AU2011/000717 2 Summary of the invention [008] According to an embodiment of the invention, there is provided a thermal expansion joint or conduit using a curved tube, wherein at least the curved portion of the tube has a concertina-like profile, the profile having a component transverse to the axis of the tube. [009] The profile can be corrugated. [010] The profile can include one or more helices. [011] The tube can have a shape adapted to facilitate bending of the curve to take up relative movement between the ends of the tube. [012] The tube can have one or more curves. [013] The curves can be arranged to facilitate uptake of relative movement of the ends of the tube by at least one of the curves. [014] The tube can be omega shaped. The axes of the omega tube inlet and outlet pipes can be co-planar. [015] The tube can be formed in a loop. [016] The tube can be formed in a "U" shape. [017] The expansion joint or conduit can include end tube extensions. [018] The end tune extensions can be integral with the helical tube. [019] The extension tubes can be of circular cross section. [020] In an alternative embodiment, the pipe can have discrete annular ridges spaced and dimensioned to provide the required minimum bending radius. Brief description of the drawings [021] An embodiment or embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. [022] Figure 1 is a schematic illustration of expansion connections between solar collector panels. [023] Figure 2 illustrates an expansion joint or conduit according to an embodiment of the invention. [024] Figure 3 illustrates a modification of the expansion joint or conduit of Figure 2. [025] Figure 4 is a section view illustrating the depth of the helices.

WO 2012/083337 PCT/AU2011/000717 3 [026] Figure 5 illustrates a side view of an inclined expansion joint or conduit. [027] Figure 6 illustrates a tube with a plurality of spitals. [028] Figure 7 illustrates an expansion joint or conduit in the form of a loop. [029] Figure 8 illustrates a "U" shaped expansion joint or conduit. [030] Figure 9 illustrates a corrugated tube suitable for use in a further embodiment of the invention. [031] The numbering convention used in the drawings is that the digits in front of the full stop indicate the drawing number, and the digits after the full stop are the element reference numbers. Where possible, the same element reference number is used in different drawings to indicate corresponding elements. [032] It is understood that, unless indicated otherwise, the drawings are intended to be illustrative rather than exact representations, and are not necessarily drawn to scale. The orientation of the drawings is chosen to illustrate the features of the objects shown, and does not necessarily represent the orientation of the objects in use. Detailed description of the embodiment or embodiments [033] Figure 1 shows a pair of solar collector panels 1.004, 1.012 having heat transfer fluid risers 1.010, 1.018 connecting upper headers 1.006, 1.014 and lower headers 1.016 and 1.008. The upper header 1.006 of collector 1.004 is connected to the upper header 1.014 of collector 1.012 by an upper expansion joint or conduit 1.020 and the lower header 1.008 of collector 1.004 is connected to the lower header 1.016 of collector 1.012 by lower expansion joint or conduit 1.022. The expansion joints have an omega" shape, and, in use, are installed with the major plane of the connector slightly below the horizontal to avoid air entrapment. [034] While only two solar collectors are shown in Figure 1, these can be the last and first solar collectors of adjacent arrays of collectors which will produce a significant thermal expansion of the combined headers of each array. [035] The expansion joints or conduits can be of copper, stainless steel, or other suitable material. In the embodiment of Figure 1, the expansion joints or conduits have an "omega" or lyre shape. As illustrated in Figure 2, the omega shape includes three curves, the inner radius 2.024, and two outer radii, 2.026, 2.028. This WO 2012/083337 PCT/AU2011/000717 4 shape is one of a number of shapes which are suitable for absorbing mechanical movement, such as that resulting from thermal expansion of the headers. [036] Prior art systems have used such a system with a copper pipe. The Australian & New Zealand Standard ASINZS 3500.4:2003 specifies the dimensions for various tube diameters and expansion joint or conduit configurations. In this standard, for the omega or lyre shape, the inner radius is specified as equal to the two outer radii. The minimum radius varies, depending on pipe size, between 300 mm for DN15 to 910 mm for DN 125. (DN = Diameter Nominal) The minimum bending radii specified for a 25 mm pipe used in such an arrangement with 30 mm expansion is 430 mm. The overall width is specified as 2.83*R, where R is the minimum radius. This means that the expansion joint or conduit requires significant space for mounting solar collector arrays. [037] We have found that by using a helical grooved pipe or tube 2.020, the bending radii of the curves as shown in Figure 2 can be as follows; interior radius 2.024 = 40 mm; exterior radius 2.026, 2.028 = 30 mm. [038] This results in an outer diameter 2.038 of the loop of the omega of about 130 mm or slightly more depending on the projection of the helices beyond the nominal diameter of the tube. The "feet" of the omega extends the overall width 2.040 to about 220 to 230 mm. This is a width which is substantially smaller than the smooth tube arrangements specified in the standard AS 3500. [0391 For the expansion joint or conduit according to an embodiment of the invention, using DN 25 pipe to absorb 30 mm expansion, the outer diameter 2.038 can be 130 mm or more, the gap 2.042 can be 30 mm or more, and the overall width of the helical portion of the omega can be 210 mm or more. The connection extensions can add a further width of the order of 45 mm each. [040] In the embodiment shown in Figure 2 separate connection extension tubes 2.030, 2.032 can be connected to the ends of the feet of the omega. The extension tubes can have a diameter of about 20 mm. The connection between the extension tubes and the helical tube can be by soldering, brazing, swaging, or other suitable connection method. The diameter of the extension tubes 2.030, 2.032 in this embodiment, with the helical tube having a nominal diameter of 25 mm, is about 20 mm as the "valleys" of the helical project into the tube to define an interior radius WO 2012/083337 PCT/AU2011/000717 5 4.046, while the peaks" project outward to define an external diameter 4.048 beyond the nominal diameter 4.044 of 25 mm as shown in Figure 4. [041] The extension tubes can be attached to the headers of the adjacent solar collector arrays by, for example, cone-tite compression fittings, flare and flare nut connection or other suitable connection means. [042] The gap 2.042 is sufficient to take up the expected linear thermal expansion of the headers of the associated arrays without exceeding the bending limit of the helical tube. As distinct from the arrangement specified in the above standard, where the inner and outer radii are equal, the inner radius 2.024 of the present invention can be larger-than the outer radius 2.026, 2.028 while still producing a more compact expansion joint or conduit than that of the standard. This allows the inner radius to contract to take up the expansion. The arc of the inner radius can be greater than 180* as distinct from the embodiment of Figure 8 discussed below. [043] In one embodiment, the helical tube has four helices 900 apart with a pitch of about 28 mm for an individual helical, so that the adjacent helices have about 7mm axial separation. The wall thickness of the helical tube can be of the order of 1 mm, and the nominal diameter of the tube before formation of the helices can be about 25 mm. [044] The prior art bending radius for an omega expansion joint or conduit using 25 mm tube was specified as R = 430 mm, and overall width is of the order of 2.83*R, which is more than 1200 mm. As discussed above, the bending radius of an expansion tube according to an embodiment of this invention can be of the order of 30 to 40 mm, and overall width for the 25 mm omega can be less than about 230 mm. Thus, in practice, a gap of 360 mm between solar collector arrays can be used to provide adequate working space for installation of the expansion joint or conduit, while the prior art smooth tube requires in excess of 1200 mm. [045] The expansion joint or conduit of the present invention has a substantially smaller bending radius and overall width than that of the prior art. The substantial reduction in permissible bending radius is due to the. helices facilitating a "concertina" effect, the helical sections on the inside of the curve being compressed to less than the nominal pitch of the helices, while the helical segments on the outer side of the curve expand beyond the nominal helical pitch. A limit to the bending radius occurs when the walls of adjacent helices on the inside of a bend abut. The helical fluting allows the tube to change shape while minimizing strain on the walls.

WO 2012/083337 PCT/AU2011/000717 6 Thus work hardening is minimized, improving the fatigue strength of the connector tube. [046] Factors which can be used in designing the minimum bending radius include the pitch of the helices, the number of helices, the width of the helices, the profile of the helices, the inclination of the helices to the tube axis, the width of the "valleys" between the helices, the diameter of the pipe, the thickness of the pipe. [047] A suitable helical tube can be manufactured, for example, by the method described in published patent specification W09407071 "Manufacture of helically Corrugated Conduit", the contents of which are incorporated herein by reference. This process results in a copper helical flute tube suitable for use in manufacturing a heat transfer tube. This patent specification for W09407071 describes the manufacture of helical tube to increase surface area for use in heat exchangers. [048] The helical flutes can be applied over the whole length of the tube, or the ends of the tube can be left as the original circular cross section. The tube can be bent into the required shape, for example, on a suitable jig. [049] Figure 3 illustrates a modification of the expansion joint or conduit of Figure 2. In this embodiment, the connection extensions 3.034, 3.036 are formed integrally of the same pipe as the helical tube section. The connection extensions can be connected to the headers of adjacent solar collector arrays. [050] Figure 5 illustrates a side view of an expansion joint or conduit with its major plane at an incline angle 0 below the horizontal. 0 should not be above the horizontal to avoid entrapment of air. 0 should not exceed about 15* to avoid interference with natural convection within the collector array. [051] Figure 6- is an illustrative perspective of the expansion joint or conduit of Figure 2 illustrating a number of separate helixes 6.052, 6.054, 6.056. The expansion joint or conduit can have, for example, four separate helices. [052] Figure 7 illustrates an expansion joint or conduit according to alternative embodiment of the invention, in which the tube 7.002 is formed into a loop 7.060 with tangential extensions 7.062, 7.064. In this embodiment, expansion is accommodated by the extensions 7.062, 7.064 moving towards one another, with the result that the radius of the loop expands rather than contracts.

WO 2012/083337 PCT/AU2011/000717 7 [053] Figure 8 is a further embodiment to that of Figure 2 but with a larger gap -8.042 compared with the inner radius 8.024, and the arc of the inner radius is about 180*. [054] Figure 9 illustrates a tube 9.070 having discrete annular corrugations 9.072 and suitable for forming into an expansion joint or conduit in accordance with a further embodiment of the present invention. However, it is considered that the helical tube provides better stress distribution may thus have greater durability under fatigue loads. [055] The helical tube can be enclosed in flexible insulation, such as an artificial; rubber or the like. [056] While the conduit formation of Figure 4 shows a "sinusoidal" curved cross section, other cross sections such as square sinusoidal formations can also be utilised to a similar effect. [057] The curved shapes of the arrangements illustrated in Figures 2, 7, and 8 facilitate the uptake of relative movement between the ends of the tube, as the curves translate the movement into flexure of at least one of the curves. The profiled tube also has enhanced fatigue resistance compared with a round tube. The arrangements embodying the invention are cheaper than the braided plastic hoses. [058] In this specification, reference to a document, disclosure, or other publication or use is not an admission that the document, disclosure, publication or use forms part of the common general knowledge of the skilled worker in the field of this invention at the priority date of this specification, unless otherwise stated. [059] In this specification, terms indicating orientation or direction, such as upu, "down", "vertical", "horizontal", "left", "right" "upright", "transverse" etc. are not intended to be absolute terms unless the context requires or indicates otherwise. These terms will normally refer to orientations shown in the drawings. [060] Where ever it is used, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of". A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear. [061] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features WO 2012/083337 PCT/AU2011/000717 8 mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention. [062] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims (13)

1. A solar collector array thermal expansion joint or conduit using a curved tube, wherein at least the curved portion of the tube has a concertina-like profile, the profile having a component transverse to the axis of the tube.

2. A solar collector array thermal expansion joint or conduit as claimed in claim 1, wherein the tube is a helical tube.

3. An expansion joint or conduit as claimed in claim 2, wherein the tube has one or more helical flutes.

4. An expansion joint or conduit as claimed in any one of claims 1 to 3, wherein the tube has a shape adapted to facilitate bending of the curve to take up relative movement between the ends of the tube.

5. An expansion joint or conduit as claimed in any one of the preceding claims, wherein the tube has one or more curves.

6. An expansion joint or conduit as claimed in any one of the preceding claims, wherein the tubes are arranged to facilitate uptake of relative movement of the ends of the tube by at least one of the curves.

7. An expansion joint or conduit as claimed in any one of the preceding claims, wherein the tube is omega shaped.

8. An expansion joint or conduit as claimed in any one of claims 1 to 6, wherein the tube is formed in a loop.

9. An expansion joint or conduit as claimed in any one of claims 1 to 6, wherein the tube is formed in a "U" shape.

10. An expansion joint or conduit as claimed in any one of the preceding claims, including end tube extensions.

11. An expansion joint or conduit as claimed in claim 10, wherein the end tune extensions are integral with the helical tube.

12. An expansion joint or conduit as claimed in claim 10 or claim 11, wherein the extension tubes are of circular cross section.

13. An expansion joint or conduit as herein described with reference to the accompanying drawings.