AU2005201519A1

AU2005201519A1 - Heat exchange tubes

Info

Publication number: AU2005201519A1
Application number: AU2005201519A
Authority: AU
Original assignee: Brivis Australia Pty Ltd
Current assignee: Brivis Australia Pty Ltd
Priority date: 1999-03-24
Filing date: 2005-04-11
Publication date: 2005-05-05
Also published as: AUPP938699A0; AU2008201297A1; AU2011201517A1; AU2256600A

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): BRIVIS AUSTRALIA PTY LTD A.C.N. 004 783 493 Invention Title: HEAT EXCHANGE TUBES The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 HEAT EXCHANGE TUBES The present invention relates to a heat exchange tube and to a method of forming the heat exchange tube.

The present invention relates particularly, although by no means exclusively, to a heat exchange tube for a heater of the type which heats a stream of air flowing through the heater by heat exchange between the air and heat generated by a burner assembly.

More particularly, although by no means exclusively, the present invention relates to a heat exchange tube for a heater of the type described in the preceding paragraph which forms part of a ducted space heating system for a domestic home. Heaters of this type generally include: a heat exchange chamber which has an inlet and an outlet for a stream of air to be heated; a burner assembly; and a heat exchange assembly which includes a plurality of heat exchange tubes coupled to the burner assembly and positioned in the heat exchange chamber so that hot combustion products from the burner assembly flow through the tubes and heat air flowing through the heat exchange chamber by heat exchange via the walls of the tubes.

The heat exchange assembly may include a series of relatively large diameter primary heat exchange tubes.

H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBE.doc 11/04/05 -3- The heat exchange assembly may also include a manifold connected to outlet ends of the primary heat exchange tubes and a series of smaller diameter secondary heat exchange tubes connected to the manifold. With this arrangement hot combustion products from the burner assembly flow through the primary heat exchange tubes into the manifold and from the manifold through the secondary heat exchange tubes.

Generally, heat exchange tubes (primary and secondary) are formed either by bending round tubes or by pressing round tubes and then bending the tubes into various shapes that are selected to optimise heat transfer from hot combustion products to the tubes and heat transfer from the tubes to air flowing through the heat exchange chamber within the constraints of the available space in the chamber and other factors.

An object of the present invention is to provide an alternative configuration of a heat exchange tube.

Another object of the present invention is to provide an alternative method of forming the heat exchange tube.

According to the present invention there is provided a heat exchange tube which includes an inlet end, an outlet end, and a section between the inlet and outlet ends, which section includes two opposed longer sides and two opposed shorter sides and a series of spaced-apart parallel indentations in the longer sides that are transverse to the longitudinal dimension of the tube and are positioned so that adjacent indentations are in opposite longer sides, whereby the section defines a tortuous flow path.

Preferably the tortuous flow path section is a H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBE.doc 11/04/05 r 4 substantial part of the length of the tube.

Preferably the tortuous flow path section is at least 80% of the length of the tube.

The heat exchange tube may be a primary heat exchange tube and/or a secondary heat exchange tube for a heater of the type described above.

According to the present invention there is also provided a method of forming a heat exchange tube which includes a step of pressing a section of a tube between opposed faces of a press, which faces have parallel ridges that are positioned so that the ridges on one face are parallel to but offset laterally from the ridges of the other face, and forming a flattened pressed section that has two opposed longer sides and two opposed shorter sides and a series of transverse parallel indentations formed in the opposed longer sides which cause the pressed section to define a tortuous flow path through the pressed section.

Accordingly to the present invention there is also provided a heater, more preferably a heater for a ducted space heating system, which includes a plurality of the above-described heat exchange tube.

The present invention is described further with reference to the accompanying drawings, of which: Figure 1 is a top plan view of a preferred embodiment of a heat exchange tube in accordance with the present invention; and Figure 2 is a side elevation of the heat exchange tube shown in Figure i.

The heat exchange tube shown in the figures is H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBEdoc 11/04/05 5 suitable particularly for use as a heat exchange tube in a heater that forms part of a ducted space heating system for a domestic home and the heat exchange tube is described in this context.

Australian patent applications 59452/98, 59454/98 and 59455/98 describe an example of such a heater and a space heating system, and the disclosure in the patent specifications of these patent applications is incorporated herein by cross-reference.

In such a space heating system, typically, the heater heats a stream of air as it flows through a heat exchange chamber in the heater. Typically, the air is drawn into the chamber by a return air duct in the home or from outside the home and the heated air generated in the heater is distributed through the home via a duct network.

Typically, the air is heated by heat exchange with hot combustion products that are generated by a gas-fired burner assembly of the heater and then flow through an assembly of primary and secondary heat exchange tubes arranged in the heat exchange chamber in the flow path of air through the chamber.

The heat exchange tube shown in the figures includes: an inlet end 3; an outlet end 5; and a central section 7 that forms a substantial part, typically at least 80%, of the length of the tube.

The inlet and outlet ends 3, 5 have circular cross-sections and the central section 7 has a non-circular H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBE.doc 11/04/05 6 cross-section with two longer sides 9 and two shorter sides 11.

In addition, the central section 7 has a series of spaced-apart parallel indentations 13 in the longer sides 9. The indentations 13 are perpendicular to the length dimension of the tube and are positioned so that adjacent indentations 13 are in opposite longer sides 9 of the central section 7. The arrangement of the indentations 13 is such that the central section 7 defines a tortuous flow path which promotes turbulent flow of combustion products through the tube and thereby optimises heat transfer from the hot combustion products to the walls of the tube.

In accordance with a preferred embodiment of the method of the present invention, the central section 7 of the heat exchange tube is formed by pressing a round tube between opposed faces of a press which has parallel ridges on the faces of the press so that, simultaneously, the tube is pressed along the length of the pressed section and is indented at spaced intervals along the length of the pressed section.

The press may be of any suitable construction and may be operated under any suitable operating conditions.

Many modifications may be made to the preferred embodiments of the heat exchange tube and the method of forming the heat exchange tube described above without departing from the spirit and scope of the present invention.

In this connection, whilst the preferred embodiment includes indentations 13 that are perpendicular to the length dimension of the tube, the present invention is not limited to this arrangement and extends to any H:\Bkrot\Keep\speci\BRIV1S HEAT EXCHANGE TUBEdoc 11/04/05 -7 arrangement in which the indentations are transverse to the length dimension of the tube.

H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBEdoc 11/04/05

Claims

1. A heat exchange tube which includes an inlet end, an outlet end, and a section between the inlet and outlet ends, which section includes two opposed longer sides and two opposed shorter sides and a series of spaced- apart parallel indentations in the longer sides that are transverse to the longitudinal dimension of the tube and are positioned so that adjacent indentations are in opposite longer sides, whereby the section defines a tortuous flow path.

2. The heat exchange tube defined in claim 1 wherein the tortuous flow path section is a substantial part of the length of the tube.

3. The heat exchange tube defined in claim 2 wherein the tortuous flow path section is at least 80% of the length of the tube.

4. A method of forming a heat exchange tube which includes a step of pressing a section of a tube between opposed faces of a press, which faces have parallel ridges that are positioned so that the ridges on one face are parallel to but offset laterally from the ridges of the other face, and forming a flattened pressed section that has two opposed longer sides and two opposed shorter sides and a series of transverse parallel indentations formed in the opposed longer sides which cause the pressed section to define a tortuous flow path through the pressed section. H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBE.doc 11/04/05 9 A heater for a ducted space heating system which includes a plurality of the heat exchange tube defined in any one of the preceding claims. Dated this llth day of April 2005 BRIVIS AUSTRALIA PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\Bkrot\Keep\speci\BRIVIS HEAT EXCHANGE TUBE.doc 11/04/05