AU2005250502B2

AU2005250502B2 - A frost protection device for a conduit system

Info

Publication number: AU2005250502B2
Application number: AU2005250502A
Authority: AU
Inventors: Paul W m Bartsch; Andrew D Marsh
Original assignee: Rinnai Australia Pty Ltd
Current assignee: Rinnai Australia Pty Ltd
Priority date: 2004-06-03
Filing date: 2005-04-07
Publication date: 2010-05-13
Anticipated expiration: 2025-04-07
Also published as: AU2005250502A1

Description

WO 2005/119135 PCT/AU2005/000503 A FROST PROTECTION DEVICE FOR A CONDUIT SYSTEM Field of the Invention The present invention relates to a frost protection device 5 for a conduit system. In particular, the invention relates to a frost protection device for a conduit system of the type found in conventional solar hot water collectors. 10 Background of the Invention Solar hot water collectors generally comprise an assembly that includes a matrix of tubes (often made of copper), the matrix further including riser and header tubes. Water is circulated through these tubes where it is heated 15 by sunlight; once heated the water is passed to an insulated tank where it is stored in readiness for use. Solar collectors are generally mounted in exposed locations (such as roof tops), where they are subject to 20 extremes of temperature, unfortunately these extremes include sub zero temperatures. It is known that water expands by approximately 9% when it freezes, this expansion can damage solar hot water systems by rupturing the matrix of tubes, resulting in irreparable leakage. 25 It is an object of the present invention therefore to provide a frost protection device for a conduit system. Summary of the Invention 30 The invention provides a frost protection device for a conduit system including at least one means for initiating freezing of the fluid at a first point in the system, means for controlling the propagation of freezing of a fluid in the conduit away from this first point and 35 towards a second point, such that expansion of the fluid is concentrated at the second point in the conduit, and at least one means for absorbing any fluid expansion due to WO 2005/119135 PCT/AU2005/000503 -2 freezing located at this second point in the conduit. Preferably the conduit system is a matrix of tubes in a solar hot water collector. 5 Preferably the matrix of tubes includes risers and headers. Preferably the means for absorbing expansion is positioned 10 in at least one header. Preferably the means for initiating freezing of the fluid includes means for locally reducing the cross-sectional area of the conduit. 15 Preferably the means for controlling the fluid freezing propagation includes graduated insulation on the outside of the conduits. 20 Preferably the means for locally reducing the cross sectional area of the conduit is positioned in the risers. Preferably the means for absorbing expansion includes an expansion chamber connected to the conduit, a piston which 25 seals against the internal walls of the chamber, and biasing means for the piston, wherein in use, the last of the fluid to freeze will expand from the conduit and into the chamber, and this expansion will displace the piston against the biasing means. 30 Preferably the biasing means is a spring. However, other devices such as resilient members or the like could be used. 35 Preferably the graduated insulation is on the header tubes and the expansion chamber.

WO 2005/119135 PCT/AU2005/000503 -3 Preferably the insulation increases toward the expansion chamber. In a further form the means for initiating freezing may be 5 positioned proximate to a coupling point between two collectors. Preferably the coupling point connects the respective header pipes of a pair of collectors. 10 Preferably the coupling point between the respective header pipes is not insulated. Preferably freezing is then propagating from the coupling 15 point towards the collectors, at least one of which will incorporate means for absorbing expansion. The invention also provides a solar hot water collector comprising: 20 at least one header; at least one riser connected to the at least one header; a coaxial tube within the at least one riser; a frost protection device connected to the header 25 and comprising: a chamber; a piston located within the chamber for movement within the chamber; and biasing means for biasing the piston to a first 30 location, so that upon freezing of water in the coaxial tube, expansion of the water due to freezing will move the piston in the chamber against the bias of the biasing means away from the first location, and upon thawing of the 35 water, the biasing means biases the piston back to the first location.

WO 2005/119135 PCT/AU2005/000503 -4 Preferably the biasing means comprises a spring. Preferably the chamber is an elongate chamber. 5 Preferably the chamber and the header are surrounded by insulating material. Brief Description of the Drawing A preferred embodiment of the invention will be described, 10 with reference to the accompanying drawing, in which: Figure 1 is a cross-sectional view through a frost protection device and a portion of tubing in a solar hot water collector. 15 Detailed Description of the Preferred Embodiment Now referring to the illustrations and, in particular to Figure 1, there is a frost protection device 1 connected to a conduit system 2. These conduits are a part of a matrix of tubes found in a solar hot water collector. In 20 this portion of the matrix there is a header 4, with a pair of risers 6 connected to it. By way of example, the portion illustrated is from a collector that has two headers, each 3/4 of an inch in diameter, one at the top of the collector, and one at the bottom, which run 25 parallel to one and other. There are 10 risers, each 3/8 of an inch in diameter equally spaced along the length of the headers, connecting them. The frost protection device 1 is connected to the header 4, approximately half way between two risers 6. 30 Each of the risers has a coaxial tube 10 located within them at their approximate midpoint A, which locally reduce the diameter of the conduit to 5/16 of an inch, thereby reducing the cross-sectional area of the conduit. 35 The frost protection device 1 includes an expansion chamber 12 connected to the header, a piston 14 that seals WO 2005/119135 PCT/AU2005/000503 -5 against the internal walls of the chamber, and a spring 16 for biasing the piston against water that might try to enter the expansion chamber. The expansion chamber is elongate, and the tubing is in this case, 1 inch in 5 diameter. It is to be understood by a person skilled in the relevant art that the dimensions given for the tubes of both the collector and the expansion chamber are for the purposes 10 of providing an example only, and that it would be possible to produce a functional collector and expansion chamber of different dimensions and proportions to those mentioned. 15 The header tube is covered by insulating material 18, this insulation is thickest in the region surrounding the junction C between the expansion chamber and the header tube, and the insulation becomes progressively thinner out towards the junction B between the risers and the header 20 tube. The risers themselves are not covered by any insulating material at all. In use then, any freezing of water in the system will initiate in the coaxial tubes 10 inside the risers 6, 25 where the diameter of the water column is thinnest (i.e. in the vicinity of point A), and propagate upwardly toward the junction between the riser and the header B. The freezing will then propagate away from the junction where the insulation is thinner, toward the point at which the 30 expansion chamber is positioned C, where the insulation is thicker. The freezing will then propagate into the expansion chamber 12, and the piston 14 in the expansion chamber 35 will be forced downward by the expansion due to freezing, against the bias of the spring 16. The expansion chamber then has absorbed the expansion of the water due to WO 2005/119135 PCT/AU2005/000503 -6 freezing, thereby preventing any damage to the tubes. When the water thaws, the spring 16 will again force the piston 14 upwardly so as to displace the water from the 5 expansion chamber 12. In practice, in a hot water collector there might be a number of these devices 1 located throughout the system. The expansion chambers 12 of these devices would be sized 10 to accept at least the volume due to expansion that would be expected from the volume of water in the vicinity of the chamber. It is a common practice to couple a plurality of 15 collectors together via their respective header pipes to form an array of collectors. Standard practice then is to insulate this connection point to prevent freezing initiating at this coupling point. 20 In a further form of the invention therefore, it is desirable to initiate the freezing of the water proximate to the point at which the two header pipes connect by using coaxial tubes located within the pipes as before, and leaving this connecting pipe un-insulated. Freezing 25 then can be initiated in the connecting pipe and propagated into the collector and towards the expansion chamber. It is considered that the frost protection device for a 30 conduit system according to the present invention will be of particular benefit to those who wish to prevent damage to their hot water collector due the expansion of the water due to freezing. 35 Throughout this specification, the purpose has been to illustrate the invention and not to limit this.

WO 2005/119135 PCT/AU2005/000503 -.7 In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise", or variations such as 5 "comprises" or "comprising", is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

1. A frost protection device for a conduit system including at least one means for initiating freezing of 5 the fluid at a first point in the system, means for controlling the propagation of freezing of a fluid in the conduit away from this first point and towards a second point, such that expansion of the fluid is concentrated at the second point in the conduit, and at least one means 10 for absorbing any fluid expansion due to freezing located at this second point in the conduit.

2. The device of claim 1 wherein the conduit system is a matrix of tubes in a solar hot water collector. 15

3. The device of claim 2 wherein the matrix of tubes includes risers and headers.

4. The device of claim 1 wherein the means for 20 absorbing expansion is positioned in at least one header.

5. The device of claim 1 wherein the means for initiating freezing of the fluid includes means for locally reducing the cross-sectional area of the conduit. 25

6. The device of claim 1 wherein the means for controlling the fluid freezing propagation includes graduated insulation on the outside of the conduits. 30

7. The device of claim 5 wherein the means for locally reducing the cross-sectional area of the conduit is positioned in the risers.

8. The device of claim 4 wherein the means for 35 absorbing expansion includes an expansion chamber connected to the conduit, a piston which seals against the internal walls of the chamber, and biasing means for the WO 2005/119135 PCT/AU2005/000503 -9 piston, wherein in use, the last of the fluid to freeze will expand from the conduit and into the chamber, and this expansion will displace the piston against the biasing means. 5

9. The device of claim 8 wherein the biasing means is a spring.

10. The device of claim 6 wherein the graduated 10 insulation is on the header tubes and the expansion chamber.

11. The device of claim 10 wherein the insulation increases toward the expansion chamber. 15

12. The device of claim 1 wherein the means for initiating freezing may be positioned proximate to a coupling point between two collectors. 20

13. The device of claim 12 wherein the coupling point connects the respective header pipes of a pair of collectors.

14. The device of claim 13 wherein the coupling point 25 between the respective header pipes is not insulated.

15. The device of claim 12 wherein freezing is then propagating from the coupling point towards the collectors, at least one of which will incorporate means 30 for absorbing expansion.

16. A solar hot water collector comprising: at least one header; at least one riser connected to the at least one 35 header; a coaxial tube within the at least one riser; a frost protection device connected to the header WO 2005/119135 PCT/AU2005/000503 - 10 and comprising: a chamber; a piston located within the chamber for movement within the chamber; and 5 biasing means for biasing the piston to a first location, so that upon freezing of water in the coaxial tube, expansion of the water due to freezing will move the piston in the chamber against the bias of the biasing means away from 10 the first location, and upon thawing of the water, the biasing means biases the piston back to the first location.

17. The collector of claim 16 wherein the biasing 15 means comprises a spring.

18. The collector of claim 16 wherein the chamber is an elongate chamber. 20

19. The collector of claim 16 wherein the chamber and the header are surrounded by insulating material.