GB2227542A - Flue pipe - Google Patents

Abstract

A miniature flue pipe for use in a flue into which combustion products from a gas-fired appliance are forcably discharged and in which condensation forms. The pipe 1 comprises a longitudinally extending pathway 2 along which the condensate can drain and partition walls 3 extending along the pipe above the pathway. The condensate can drain into the pathway via gap 4 between the partition walls. The partition at least partially shelters the pathway from the forces of a gas or vapour flowing through the pipe 1 above the partition walls. The partition (n) may take several forms eg a mesh (Figs 7a, 7b), a C or U section (Figs 5a-6b) or a approximately trapezoidal section (Figs 4a, 10). The pipe may have a triangular, trapezoidal or stadium cross-section (Figs 2a, 8a, 9a). An insulation layer (35, Fig 10) may be provided. <IMAGE>

Description

} FLUE PIPE AND FLUE The present invention relates to flue pipes and flues comprising such pipes.

Condensation is known to form in flues into which combustion products are discharged from high efficiency appliances, for example, gas-fired appliances, i.e. gasfired appliances having an efficiency of about 88% or more or where the flue gas inlet temperature is about 60 degrees Centrigrade or less.

Such condensation should not be allowed to collect in the flue but should be expelled, for example, at a terminal or returned to the appliance where it can be disposed of down a drain.

Where substantial amounts of condensate are produced, usually from high efficiency appliances of more than a few kilo-watt rating, it is preferable to return the condensate back to the appliance.

The development of small high pressure fans such as toroidal fans has allowed high efficiency appliances to operate with so-called miniature flues. At the present time, the internal diameter of these miniature flues when used with domestic appliances, eg. of up to 20Kw output, are of the order of 30mm or less, for example 22mm. It is envisaged that with the development of more powerful fans, the miniature flue may be somewhat greater than 30mm when used with commercial appliances. Unlike natural draught flues, miniature flues assisted by high pressure fans can operate not only with vertically disposed sections of flue but also with approximately horizontally disposed sections of flue.

The miniature flues are relatively easy to install and are less obtrusive. An horizontal section or run of the flue may, for example, be routed around part of the skirting board.

In flues where the runs of flue pipe are either generally or substantially vertical, the condensate may readily return to the appliance for disposal. However, where a flue has nominally horizontal pipe runs or sections (in practice inclined a few degrees, up to say about 7 degrees, in the preferred direction of gravitational flow, for the condensate i.e. back to the appliance) experiments carried out by the Applicants have shown that the flue may become blocked with condensate at or adjacent to a bend between a nominally horizontal section and an upwardly extending vertical section.

Applicants have determined that such blockage develops because the flow of condensate back to the appliance is irestrained or inhibited by the force of the flow of the flue gas acting in the opposite direction and away from the appliance.

Such condensate blockages may reduce the flow of flue gas away from the appliance sufficiently to cause any backpressure-sensing safety system associated with the appliance to shut the appliance down.

An object of the invention is to provide a flue pipe for use in a flue to reduce the likelihood of condensate blockage occurring as described above.

To this end, from one aspect of the invention a pipe for use in a flue comprises at least one pathway extending along the inside of the pipe into and along which pathway condensate formed inside the pipe can drain and means along the inside of the pipe capable of at least partially sheltering the pathway from the forces of a gas or vapour flowing through the pipe on the side of the sheltering means remote from the pathway.

From another aspect of the invention, a flue system comprises a pipe, as defined above, arranged so that condensate which forms in the pipe can drain into the pathway and down the pathway in one direction whilst flue gas can flow through the pipe in the opposite direction.

The sheltering means may comprise at least one partition extending part way across the bore of the pipe and extending along the pipe above the pathway. For example, the partition may at least in part define one or more slots or apertures therealong via which condensate may drain into the pathway. The partition may be formed of two parts which extend towards each other and define a slot therebetween. The pathway may at least in part be provided by the internal surface of the pipe wall. The pipe may comprise substantially parallel opposing side walls with the corresponding ends of the side walls being joined by end portions which at least in part define respective pathways. For example, such end portions may form channel-like sections which, may for example be substantially arcuate or V-shaped.The side walls may be substantially equal in length or, alternatively may be of unequal length such that, for example, the pipe is generally trapezium shaped in cross section. The opposite end portions of such parallel sided pipe forms together with associated partitions may be substantially mirror images of each other.

Preferably, the or each partition is integral with the pipe wall.

The, or each, partition may be connected to the pipe wall by a, member extending transversely from the partition.

The or each pathway may be provided by a or a respective channel extending through the pipe. The or each channel may be formed between longitudinally extending walls projecting inwardly of the pipe from the pipe wall. The thickness of the walls may increase in a direction inwardly of the pipe wall such that the mouth of the or each channel is of restricted width, in which case the "top" or inner surfaces of the walls form the sheltering means.

Alternatively, the or each channel may be formed by a channel section having one side portion or its base connected with the pipe wall.

The sheltering means may be in the form of netting or mesh. The netting may be so disposed that it is spaced from the pipe wall above the pathway. The netting may be made up of interconnected longitudinal and transverse strands or lengths of material, with the cross-sectional dimension of the longitudinal lengths of material being greater than the cross-sectional dimension of the transverse lengths of material. In this case it may be arranged that the longitudinal lengths of the netting extend along and contact the pipe wall such that pathways for the condensate are formed at or adjacent the regions of contact between the longitunal lengths and the pipe wall.

In use, the flue pipe would be exposed to flue product temperatures which in the case of high efficiency appliances would typically be 100 0C or lower, and also exposed to mildly corrosive condensate, typically with a pH of between 3 and 4.

Materials from which the flue pipe may be made are, for example, suitable plastics such as chlorinated polyvinyl chloride, polyethylene or polyproylene, or a suitable stainless steel or aluminium alloy. The material should have adequate corrosion resistance to the condensate.

The flue pipe may conveniently be made of a flexible material such that the pipe may be flexed to form an integral bend. For example, the pipe may comprise inner and outer tubular layers or skins of suitable plastics material between which is sandwiched a bendable tubular layer metal or metal alloy, such as aluminium.

Where one or more separate bend pieces are fitted to the flue pipe to enable the flue to run, for example, both substantially horizontally and vertically, the bend pieces may be adapted to provide for a continuation of the sheltered pathway or pathways of the flue pipe to facilitate the flow of condensate at the bends.

Alternatively, the bend piece may be formed of spaced inner and outer tubular skins with the space therebetween being for condensate flow through the bend.

In order to reduce the rate at which condensation may occur in the flue pipe, suitable lagging may be provided around the pipe. In one form the flue pipe may comprise inner and outer skins between which is a thermally insulating material such as an insulating foam.

The flue pipe may, for example, be formed by extrusion.

Inner and outer pipe skins may be co-extruded. Insulating material may be incorporated between such inner and outer skins to provide the insulated pipe construction.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which : Figures la, 2a, 3a, 4a, 5a, 6a, 7a, 8a and 9a are end or cross-sectional views of different embodiments of flue pipe according to the invention, Figures lb, 2b, 3b, 4b, 5b, 6b, 7b, 8b and 9b are sectional views taken along the lines I-I, 11-11, 111-111, IV-IV, V-V, VI-VI, and VII-VII, VIII-VIII and IX-IX, respectively, in Figures la, 2a, 3a, 4a, 5a, 6a, 7a, 8a and 9a, Figure 10 is an end view of a further embodiment of pipe similar to that shown in Figures 4a and 4b but provided with thermal insulation, and Figure 11 shows in schematic form a flue system according to the invention, leading from a high efficiency gas-fired appliance.

Referring to Figures la and lb, a pipe 1 of circular cross-section for use in a flue comprises a pathway 2 into and along which condensate can drain, when the pipe is incorporated in a flue system, as will be described below.

Sheltering means is in the form of a partition having two wall parts 3, each extending along the pipe and part way across the bore of the pipe above the pathway 2 with a longitudinal slot or gap 4 therebetween to allow condensate to drain into the pathway 2. The pathway is provided by the internal surface of the pipe wall. In a modified embodiment a plurality of pairs of such wall parts 3 may be provided around the interior of the pipe as shown in dotted lines in Figure 1.

The embodiment shown in Figures 2a and 2b is similar to the one shown in Figures la and lb except that the pipe 1 is of triangular cross-section. The two wall parts 3 with the longitudinal slot 4 extending therebetween form the partition and are disposed above a pathway 2 which is formed by the intersection of two adjoining side walls of the pipe. In a preferred modification, as shown in dotted lines, respective two wall parts 3 are also provided in both the remaining angles of the triangular pipe. In this preferred modification, with any of the three points of the angles pointing downwardly a sheltered pathway extends along the bottom of the pipe.

In Figures 3a and 3b, the sheltering means is formed by the cross-piece 6 of a "T" shaped member 5 extending along the pipe 1. The depending limb 7 of the "T" is integral with the pipe wall and pathways 8 for the condensate are provided at or adjacent the regions of contact between the depending limb 7 and the internal surface of the pipe wall on each side of the depending limb 7. In this embodiment condensate can drain into the pathways 8 via the gaps 9 between the side edges of the partition 6 and the pipe walls.

As indicated in dotted lines in Figure 3, in a modified embodiment a plurality of "T" pieces may be disposed around the interior of the pipe with adjacent pairs of depending limbs 7, which extend transversely from the cross-pieces or partitions 6, constituting walls defining therebetween respective channels 10. In this case, condensate drains into the channels 10 via the gaps 11 between the opposed side edges of adjacent cross-pieces 6.

With respect to Figures la, Ib; 2a, 2b and 3a, 3b, it is easier to arrange the modified embodiments (as shown in dotted lines) of pipe in a flue system since with the embodiments shown in full lines in the Figures having one sheltering means, the pipe has to be oriented substantially as shown in Figures la, 2a and 3a, i.e. for the pathway or pathways to be substantially along the bottom of the pipe. With the modifications the pipe can be oriented in a number of ways so that a pathway extends along the bottom of the pipe.

Figures 4a and 4b also show an embodiment in which a plurality of channels 12 are provided around the pipe, each pathway extending along or being defined by the channels. The channels are formed between longitudinally extending walls 13 which are integral with the pipe wall and project inwardly of the pipe. The thickness of these walls increase in a direction inwardly of the pipe wall such that the mouths 12a of the channels are of restricted width. The "top" or innermost surfaces 13a of the walls form the sheltering means.

In Figures 5a and 5b, channel sections 14 of generally "C" or "U" section are disposed around the wall of the pipe and are integrally connected to the pipe wall at their bases. Pathways 15a 15b for condensate extend along the inside of the channel sections and in the spacing between adjacent channel sections, respectively. The walls of the channel sections partially shelter the pathways.

The embodiment of pipe shown in Figures 6a and 6b also has channel sections 16 but with one of their side portions integrally connected to the pipe wall. Again, the walls of the channel sections provide partial shelter for condensate pathways 17a extending along the inside of the channel sections 16 and pathways 17b located between adjacent channel sections.

Figures 7a and 7b show an embodiment in which the sheltering means is in the form of netting or mesh 18 made up of interconnected longitudinal and transverse strands or lengths 18a, 18b of, for example, plastics material.

The cross-sectional dimension of the longitudinal lengths 18a of material is greater than the cross-sectional dimension of the transverse lengths 18b. The crosssectional dimension of the latter is desired to be small to reduce opposition to the flow of condensate along the pipe.

The netting 18 is arranged within the pipe such that the longitudinal lengths 18a which extend along the pipe contact the pipe wall. The pathways 19 for the condensate are formed at or adjacent the regions of contact between the longitudinal lengths 18a and the pipe wall.

Figures 8a and 8b show an embodiment of pipe which in cross-section is of substantially symmetrical trapezium shape. The pipe has longer and shorter parallel sides 20,21 disposed symmetrically to each other with the respective corresponding ends of the sides being joined to each other by sloping ends 22,23.

In the lower half of the trapezium shaped pipe, as viewed in Figure 8a, the adjoining sloping end 23 and the lower portion of longer side 20 define therebetween a pathway 24 for condensate. The sheltering means comprises a partition wall 25 extending downwardly from the longer side 20 generally towards but terminating short of the sloping end 23 to leave a slot or gap 26 via which condensate can drain into the pathway 24. The construction of the upper half of the embodiment is a mirror image of the above described lower half. Thus, this embodiment can be employed either as viewed in Figure 8a or upside down. Moreover either the longer side or the shorter side may be the side which is located adjacent a wall or the like along which the pipe is to run.

In Figures 9a and 9b the embodiment of pipe is a substantially symmetrical "stadium" shape in crosssection, that is it has two parallel side walls 27,28 of equal length whose corresponding ends are joined by concave curved or arcuate channel end portions 29.

As viewed with respect to the lower half of the pipe embodiment in Figure 9a, the sheltering means is formed by a partition having two wall parts 30 extending along the pipe and from opposite sides 27,28 of the pipe above the pathway 31 and towards each other to define therebetween a longitudinally extending slot or gap 32 via which condensate can drain into the pathway 31. The pathway is provided by the internal surface of the bottom of the channel portion. The upper half of the embodiment is a mirror image of the lower half. As will be appreciated from Figure 9a this embodiment of pipe is symmetrical about both a vertical plane and a horizontal plane, so it can be used as viewed or upside down with either of the two side walls 27,28 being locatable adjacent a wall or the like along which the pipe is to run.

With reference to Figure 10, the pipe comprises inner and outer co-axial skins 33,34 respectively. The inner pipe skin 33 is formed with longitudinally extending walls defining channels therebetween in the same manner as the embodiment shown in Figures 4a and 4b and as described above. Thermally insulating material 35 in the form of a foam, for example, is incorporated in the space between the inner and outer pipe skins 33,34 to provide a lagged pipe.

In Figure 11, which is not to scale, a flue system 36 is connected to a high efficiency appliance 37 of say 10kw output rating. The flue system comprises a flue pipe 38 which extends along a wall from the outlet of the appliance and slopes slightly downwardly, for example, 0.1 - 7 degrees in a direction back towards the appliance.

The end of the flue pipe 38 remote from the appliance is connected by a bend piece 39 to a vertical section of flue pipe 40. A high pressure fan such as a toroidal fan 41 drives combustion products produced in the appliance through the flue system.

The flue pipe 38 is in the form as shown in Figures la and lb and arranged such that condensate which forms in the pipe can drain into the pathway and down the pathway back to the appliance to a disposal point (not shown), that is with the pipe 38 so oriented that the pathway extends along the bottom of the pipe.

The flue pipes 38 and 40 may have an internal diameter of 25 mm, whilst the length of the overall pipe 38,40 may be 5m. The width of each partition wall 3 (as shown in Figure 1) forming the sheltering means may be 6mm whilst the longitudinal slot betweeen the walls 3 may be 3'nm wide.

When the appliance and toroidal fan are operating, the rate of. flow of combustion product gases and vapour through the flue system is about lOm/sec.

These combustion products flow away from the appliance through the pipe 38 on the side of the partition 3 remote from the pathway for condensate. The flow of condensate back along the pathway is relatively slow, for example 5 ml/minute.

The point at which condensate flows out of the pipe 38 for disposal may need to be shielded from the flow of combustion products into the pipe to prevent or reduce the likelihood of condensate flow from that point being inhibited by the force of the combustion product flow.

It will be appreciated that one or more further flue pipe sections similar to pipe 38 may be incorporated into the flue system and oriented in a similar fashion as pipe 38.

Again, any such further pipe sections are arranged so as to slope such that condensate can drain down back in the direction of the appliance.

It will also be appreciated that whilst in the accompanying figures the external cross-sectional shapes of the flue pipe embodiments are shown as corresponding generally to the basic forms of the internal crosssectional shapes, the external cross-sectional shapes may be of any desired form. For example, a pipe having an internal trapezium shape may have an external "stadium" shape or a rectangular shape.

Claims (20)

1. A pipe for use in a flue, said pipe comprising at least one pathway extending along the inside of the pipe into and along which pathway condensate formed inside the pipe can drain and means along the inside of the pipe capable of at least partially sheltering the pathway from the forces of a gas or vapour flowing through the pipe on the side of the sheltering means remote from the pathway.

2. A pipe as claimed in claim 1, wherein the sheltering means comprises at least one partition extending part way across the bore of the pipe and extending along the pipe above the pathway.

3. A pipe as claimed in claim 2 wherein the partition has one or more slots or apertures therein.

4. A pipe as claimed in claim 2 or 3, wherein the partition is formed of two parts which extend towards each other and define a slot therebetween.

5. A pipe as claimed in any of claim 2 3 or 4, wherein when viewed in cross-section the pipe comprises substantially parallel opposing side walls, the corresponding ends of the side walls being joined by end portions which at least in part define respective pathways.

6. A pipe as claimed in claim 5, wherein the end portions are substantially arcuate and form channel-like sections.

7. A pipe as claimed in claim 5, wherein the pipe is trapezium shaped in cross-section.

8. A pipe as claimed in claim 6 or 7, wherein the opposite end portions and associated partitions are substantially mirror images of each other.

9. A pipe as claimed in claim 2 or claim 3, wherein the partition is connected to the pipe wall by a member extending transversely from the partition.

10. A pipe as claimed in any of the preceding claims, wherein the or each partition is integral with the pipe wall.

11. A pipe as claimed in claim 1, wherein the sheltering means is in the form of netting or mesh.

12. A pipe as claimed in claim 1, wherein the at least one pathway is defined by a channel extending through the pipe.

13. A pipe as claimed in claim 12, wherein the channel is formed between longitudinally extending walls projecting inwardly of the pipe from the pipe wall.

14. A pipe as claimed in claim 13, wherein the thickness of the walls increase in a direction inward of the pipe wall such that the mouth of the channel is of restricted width.

15. A pipe as claimed in claim 13, wherein the channel is formed by a channel section having one side portion or its base connected with the pipe wall.

16. A pipe as claimed in any of claims 12 to 15, comprising a plurality of channels around the interior of the pipe.

17. A pipe as claimed in any of claims 1 to 14, wherein the at least one pathway is provided- at least in part by the internal surface of the pipe wall.

18. A flue system comprising a pipe as claimed in claim 1 arranged so that condensate which forms in the pipe can drain into the pathway and along the pathway in one direction whilst flue gas can flow upwardly through the pipe in the opposite direction.

19. A pipe for use in a flue substantially as hereinbefore described with reference to Figures la and lb, Figures 2a and 2b, Figures 3a and 3b, Figures 4a and 4b, Figures 5a and 5b, Figures 6a and 6b, Figures 7a and 7b, Figures 8a and 8b, Figures 9a and 9b, or Figure 10 of the accompanying drawings.

20. A flue system substantially as hereinbefore described with reference to Figure 11 of the accompanying drawings.