AU2019385711A1

AU2019385711A1 - An improved liquid heater

Info

Publication number: AU2019385711A1
Application number: AU2019385711A
Authority: AU
Inventors: Brendan Bourke; Alan Law
Original assignee: Rheem Australia Pty Ltd
Current assignee: Rheem Australia Pty Ltd
Priority date: 2018-11-22
Filing date: 2019-10-18
Publication date: 2021-05-27
Also published as: WO2020102847A1

Abstract

A natural draft liquid heater including: a liquid chamber, for receiving liquid to be heated; a burner chamber, for housing a fuel burner; and a flue extending from the burner chamber into the liquid chamber, the flue having an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber, wherein the flue has a single loop form.

Description

AN IMPROVED LIQUID HEATER

Field of the invention

[001 ] The present invention relates to liquid heaters, and, in particular, to natural draft liquid heaters.

Background of the invention

[002] Often liquid heaters, such as domestic gas water heaters, are assigned an energy rating in accordance with their performance. In Australia, for example, the energy rating (known as the Energy Star rating) for a water storage heater is based on a combination of thermal efficiency and standing heat loss. For continuous flow type heaters, the energy rating is based on thermal efficiency and start-up heat capacity.

[003] Typically, the highest performance domestic gas water heater appliances are continuous flow type heaters (in Australia, for example, they are currently able to achieve a 6 Energy Star rating).

[004] Nevertheless, water storage heaters, and in particular natural draft water storage heaters, have some advantages over continuous flow type heaters. Generally, for a natural draft water storage heater, no power connection is required, and smaller gas pipe fittings may be used.

[005] With respect to performance, natural draft water storage heaters have typically had lower energy ratings than continuous flow alternatives. For example, in Australia, they have typically only been able to achieve a 5 Energy Star rating.

[006] Typical natural draft water heaters have a central flue that directs combustion products for heat exchange centrally through the water tank to exit at the top of the heater. An example of a modified natural draft water heater is shown in PCT publication WO/2000/Q19153. The heater described therein provides a central and external flue path such that combustion gases are redirected from the top of the central flue down the outside of the water tank. Whilst this version has the advantage of a larger heat exchange area, the external flue path limits the options available for effective standing heat loss reduction. This therefore limits the performance (and energy rating) of the heater. [007] The present invention seeks to provide an improved liquid heater, with improved performance, that may be implemented as a domestic gas water heater.

[008] Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.

Summary of the invention

[009] In a first broad form, the present invention provides a natural draft liquid heater including: a liquid chamber, for receiving liquid to be heated; a burner chamber, for housing a fuel burner; and a flue extending from the burner chamber into the liquid chamber, the flue having an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber, wherein the flue has a single loop form.

[010] In one form, the single loop form is an open single loop form that includes a substantially U-shaped bend.

[011 ] In one form, the burner chamber is located below the liquid chamber, and the flue extends upwardly therefrom, into the liquid chamber.

[012] In one form, the single loop from of the flue is such that combustion products received therein are directed in a generally upward direction, toward a top portion of the liquid chamber, before being directed in a generally downward direction, toward a bottom portion of the liquid chamber, to a terminal portion of the flue.

[013] In one form, the terminal portion of the flue exits a side wall of the liquid chamber.

[014] In one form, the terminal portion of the flue protrudes from a side wall of the heater.

[015] In one form, substantially the entire outer surface area of the flue, between the inlet and the outlet, is located within the liquid chamber.

[016] In one form, the flue includes a base pipe portion and looping pipe portion extending therefrom, wherein an inlet end of base pipe portion opens into the burner chamber and an outlet end of the base pipe portion leads into an inlet end of the looping pipe portion.

[017] In one form, the base pipe portion is a pipe with internally projecting fins. [018] In one form, the looping pipe portion includes an internal baffle.

[019] In one form, the outlet of the flue opens to the external environment, outside the liquid heater.

[020] In one form, the liquid chamber and burner chamber are formed within a cylindrical tank.

[021 ] In one form, the liquid to be heated is water.

[022] In one form, the heater is configured to receive gas as fuel.

[023] In a further broad form, the present invention provides, a natural draft liquid heater including: a liquid chamber, for receiving liquid to be heated; a burner chamber, for housing a fuel burner; and a flue extending from the burner chamber into the liquid chamber, the flue having an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber, wherein the flue includes: a base pipe portion comprising internally projecting fins; and a looping pipe portion extending from the base pipe portion, the looping pipe portion having a single loop form.

[024] In one form, the looping pipe portion is internally baffled.

[025] In one form, an inlet end of base pipe portion opens into the burner chamber and an outlet end of the base pipe portion leads into an inlet end of the looping pipe portion.

[026] In one form, an outlet end of the looping pipe portion forms a terminal portion of the flue that exits a side wall of the liquid chamber.

[027] In a further broad form, the present invention provides a flue for a natural draft liquid heater the flue including: a base pipe portion comprising internally projecting fins; and a looping pipe portion extending from the base pipe portion, the looping pipe portion having a single loop form.

[028] In one form, the looping pipe portion is internally baffled.

[029] In one form, the looping pipe portion is internally corrosion resistant.

Brief description of the drawings

[030] A detailed description of a preferred embodiment will follow, by way of example only, with reference to the accompanying figures of the drawings, in which: Figure 1 is a cross sectional rear view of one example of a liquid heater according to the invention;

Figure 2 is a cross sectional side view of the liquid heater of figure 1 ;

Figure 3 is a perspective view of the liquid heater of figure 1 , with housing and tank transparent and separating wall between liquid chamber and burner chamber not shown;

Figure 4 is a perspective view of flue from the liquid heater of figure 1 ;

Figure 5 is a front view of the flue shown in figure 4 with base pipe portion transparent to show internal fins;

Figure 6 is a perspective view of the flue of figure 4 with base pipe portion transparent to show internal fins;

Figure 7 is a side view of the flue of figure 4;

Figure 8 is a front view of the flue of figure 4;

Figure 9 is a top view of the flue of figure 4; and

Figure 10 is a front view of the liquid heater of figure 1 (only water chamber and flue shown).

Detailed description of the embodiment or embodiments

[031 ] Embodiments of the present invention provide improved liquid heaters, and, in particular, improved natural draft liquid heaters that generally include a liquid chamber, for receiving liquid to be heated, and a burner chamber, for housing a fuel burner. To allow for heat transfer to liquid stored in the liquid chamber, a flue extends from the burner chamber into the liquid chamber. The flue includes an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber.

[032] The flue has a single loop form. The term‘single loop form’ may refer to an open loop form, such as that provided by a“U” shape, and also to a closed loop form, wherein there is crossing of the leading (i.e. upstream) and trailing (i.e. downstream) arms of the loop. It will be appreciated that the term“single” is intended to distinguish from flues that have multiple loops. [033] The burner chamber is typically located below the liquid chamber, and the flue extends upwardly therefrom, into the liquid chamber. The single loop form of the flue provides that combustion products received therein are directed in a generally upward direction, towards a upper/top portion of the liquid chamber, before being directed in a generally downward direction, toward a lower/bottom portion of the liquid chamber, to a terminal portion of the flue.

[034] The terminal portion of the flue typically exits a side wall of the liquid chamber. In some instances the terminal portion protrudes from the side wall of the heater. Generally, the outlet of the flue opens to the external environment or into an exhaust system.

[035] Generally, substantially the entire outer surface area of the flue assembly, between the inlet and the outlet, is located within the liquid chamber. This provides that heat transfer from combustion products in the flue to liquid in the liquid chamber is maximised.

[036] The flue may include a base pipe portion and a looping pipe portion extending therefrom. In such forms, an inlet end of base pipe portion opens into the burner chamber and an outlet end of the base pipe portion leads into an inlet end of the looping pipe portion. It will be appreciated that the term‘inlet end’ refers to the end of the flue or pipe portion thereof where combustion products are initially received, and, conversely, the term‘outlet end’ refers to the ends where combustion products typically exit.

[037] The base pipe portion is usually a straight pipe with internally projecting fins (sometimes known in the art as a‘Bock’ flue). The internally projecting fins improve the efficiency of heat transfer by increasing the internal surface area of the flue at the base pipe portion. Typically, in these examples, the fins are formed of mild steel. In seeking to avoid corrosion, the flue is typically configured such that condensation does not occur at the base pipe portion.

[038] Generally, the looping pipe portion extends from the outlet end of base pipe portion, and follows a looping path within the liquid chamber. The looping pipe portion typically has a single loop form extending to a upper/top portion of the liquid chamber before extending to a terminal portion of the flue at a lower/bottom portion of the container. It will be appreciated that looping pipe portion may not extend all the way to the top or bottom of the liquid chamber, but may extend generally to a top or bottom half of the chamber. In one aspect, the looping pipe portion may act as a heat trap with hotter combustion products tending to top part thereof.

[039] The terminal portion of the flue, which may or may not be part of the looping pipe portion, typically directs combustion products out of a side wall of the liquid chamber. The terminal portion of the flue typically meets the side wall of the liquid chamber at a height lower than where the looping pipe potion extends from the base pipe portion.

[040] The looping portion may be baffled internally. The single loop nature of the looping pipe portion permits ease of baffle manufacture. The looping pipe portion may also be corrosion resistant so as to accommodate any condensation that may occur in this part of the flue. For example, the internal surface of the looping portion may be protected from corrosion by enamelling.

[041 ] Generally, the liquid chamber and burner chamber are formed within a cylindrical tank which itself is located within an insulating housing. A separating wall member typically extends as a flange from the inlet end of the base pipe portion to meet the internal side walls of the liquid chamber. The separating wall member thus separating the liquid chamber from the burner chamber.

[042] It will be appreciated that the liquid heaters as described herein may be used to heat a range of liquids, although typically, are used to heat water and are embodied as gas water storage heaters that are natural draft. It would be appreciated that in such embodiments, they would typically include the basic components for operation e.g. burner, thermostat, gas inlet, water inlets/outlets etc. Also, in such embodiments, the liquid heaters are typically configured to receive natural gas as fuel with combustion products being predominantly carbon dioxide and water vapour. Other forms may utilise Liquid Petroleum or Hydrogen gas. Additionally, in such embodiments, the liquid heaters are typically configured to operate with mains water pressure.

[043] One particular example of a liquid heater according to the invention is shown in figures 1 to 10. Figure 1 shows a natural draft water heater (1 ) embodied as a domestic gas water storage heater. The natural draft water heater (1 ) includes a substantially cylindrical tank (2) located within an outer housing (3). The tank (2) includes a water chamber (4), for receiving water to be heated, and a burner chamber (5) for receiving a burner (6) therein.

[044] A flue (7) extends from the burner chamber (5) into the water chamber (4). A base pipe portion (9) of the flue (7) includes an inlet (8) that opens into the burner chamber (5) to receive combustion products (e.g. carbon dioxide, water vapour) therefrom. It will be appreciated that combustion products produced at the burner (6) are received into the flue (7), and flow therethrough to provide heat to water in the water chamber (4).

[045] The base pipe portion (9) of the flue (7) is an internally finned flue pipe (sometimes referred to in the art as a‘Bock flue’). The finned flue pipe (9) is centrally located within the tank (2), and a curved flange (10) extends radially from the inlet end (9a) thereof to the meet the internal side wall of the water tank (2). The curved flange (10) provides a substantially funnel or cup shaped extension at the inlet end (9a) of the finned flue pipe (9). The flange (1 ) thus provides separation between the water chamber (4) and the burner chamber (5). It will be appreciated the flange (10) may take a variety of forms and may not be curved.

[046] The internally projecting fins of the base pipe portion improve the efficiency of heat transfer by increasing the internal surface area of the flue (7). A large portion of heat transfer occurs at the base pipe portion (9). However, as the fins are formed of mild steel that are at risk of corrosion if any condensate forms. The flue (7) is thus configured such that condensation does not occur at the base pipe portion (9). Generally, to avoid condensate forming in the base pipe portion (9), heat transfer from the combustion products in the base pipe portion is limited to about 80%.

[047] A looping pipe portion (1 1 ) having a single loop form extends from the top or outlet end (9b) of the internally finned flue pipe (9). The looping flue pipe (1 1 ) extends in a generally upward direction (upward flow portion (1 1 a)), to an upper/top portion of the water chamber (4), before looping or turning back, to extend in a generally downward direction (downward flow portion (1 1 b)), to a terminal portion (1 1 c) at a lower/bottom portion of the water chamber (4). The looping pipe portion (1 1 ) thus acts in one aspect as a heat trap with hotter combustion products tending to the top portion (i.e. U bend area (1 1 ab)) of the looping pipe portion (1 1 ).

[048] The upward flow portion (1 1 a) of the looping pipe portion (1 1 ) includes an S-bend (1 1 aa) that leads into a U-bend portion (1 1 ab) of the pipe (1 1 ). It will be appreciated that the U-bend portion (1 1 ab) forms part of both the upward flow portion (1 1 a) and the downward flow portion (1 1 b) of the pipe (1 1 ).

[049] The S-bend (1 1 aa) brings the upward flow portion (1 1 a) closer to the side wall of the water chamber (4) when compared with the more centrally located portion of the upward flow portion (11 a) that extends initially from the finned/base pipe portion (9). The U-bend portion (11 ab) of the pipe (11 ) spans substantially the entire internal diameter of the water chamber (4), without contacting the side wall thereof.

[050] After the U-bend portion (11 ab), the downward flow portion 11 (b) extends downward with a generally straight section (11 bb), before a terminal portion (11 c) thereof turns to exit the side wall of the tank (2). The exit height of the terminal portion is a height about halfway up, or slightly above halfway up the internally finned/base pipe portion (9). It will be appreciated that the exit height of the terminal portion (11 c) may vary but is typically in a bottom portion of the tank.

[051 ] The looping pipe portion (11 ) is also corrosion resistant internally, which is typically achieved by enamelling. This part of flue is thus able to accommodate condensation of water vapour that may occur.

[052] The terminal portion (11 c) includes a downward slope (11 d) leading to the outlet (11 e), such that water vapour that may condense in the downward flow portion (11 b), does not pool in the terminal portion (11 c). In this example, the terminal portion (11 c) protrudes slightly beyond the housing of the liquid chamber, to facilitate drainage of any condensate.

[053] The looping pipe portion (11 ) is also internally baffled. It will be appreciated that the baffle construction may take a variety of forms. Having a single loop form, provides advantages in that the flue is less complex to manufacture and in that it allows more flexibility with internal baffle construction.

[054] It will be appreciated that the flue as described herein may be formed as single piece or may comprise multiple elements joined together (e.g. by welding). It will also be appreciated that, in one form, that present invention may relate generally to flues as described herein for use with liquid heaters (e.g. natural draft liquid heaters).

[055] 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.

[056] It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text. All of these different combinations constitute various alternative aspects of the invention.

[057] 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

1. A natural draft liquid heater including:

a liquid chamber, for receiving liquid to be heated;

a burner chamber, for housing a fuel burner; and

a flue extending from the burner chamber into the liquid chamber, the flue having an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber, wherein the flue has a single loop form.

2. A natural draft liquid heater as claimed in claim 1 , wherein the single loop form is an open single loop form that includes a substantially U-shaped bend.

3. A natural draft liquid heater as claimed in claim 1 or 2, wherein the burner chamber is located below the liquid chamber, and the flue extends upwardly therefrom, into the liquid chamber.

4. A natural draft liquid heater as claimed in any one of the preceding claims, wherein the single loop from of the flue is such that combustion products received therein are directed in a generally upward direction, toward a top portion of the liquid chamber, before being directed in a generally downward direction, toward a bottom portion of the liquid chamber, to a terminal portion of the flue.

5. A natural draft liquid heater as claimed in claim 4, wherein the terminal portion of the flue exits a side wall of the liquid chamber.

6. A natural draft liquid heater as claimed in claim 4 or 5, wherein the terminal portion of the flue protrudes from a side wall of the heater.

7. A natural draft liquid heater as claimed in any one of the preceding claims, wherein substantially the entire outer surface area of the flue, between the inlet and the outlet, is located within the liquid chamber.

8. A natural draft liquid heater as claimed in any one of the preceding claims, wherein the flue includes a base pipe portion and looping pipe portion extending therefrom, wherein an inlet end of base pipe portion opens into the burner chamber and an outlet end of the base pipe portion leads into an inlet end of the looping pipe portion.

9. A natural draft liquid heater as claimed in claim 8, wherein the base pipe portion is a pipe with internally projecting fins.

10. A natural draft liquid heater as claimed in claim 8 or 9, wherein the looping pipe portion includes an internal baffle.

1 1 . A natural draft liquid heater as claimed in any one of the preceding claims, wherein the outlet of the flue opens to the external environment, outside the liquid heater.

12. A natural draft liquid heater as claimed in any one of the preceding claims, wherein the liquid chamber and burner chamber are formed within a cylindrical tank.

13. A natural draft liquid heater as claimed in any one of the preceding claims, wherein the liquid to be heated is water.

14. A natural draft liquid heater as claimed in any one of the preceding claims wherein the heater is configured to receive gas as fuel.

15. A natural draft liquid heater including: a liquid chamber, for receiving liquid to be heated; a burner chamber, for housing a fuel burner; and a flue extending from the burner chamber into the liquid chamber, the flue having an inlet that opens into the burner chamber, for receiving combustion products therefrom, and an outlet that opens external to the liquid chamber, wherein the flue includes: a base pipe portion comprising internally projecting fins; and a looping pipe portion extending from the base pipe portion, the looping pipe portion having a single loop form.

16. A natural draft liquid heater as claimed in claim 15, wherein the looping pipe portion is internally baffled.

17. A natural draft liquid heater as claimed in claim 15 or 16, wherein an inlet end of base pipe portion opens into the burner chamber and an outlet end of the base pipe portion leads into an inlet end of the looping pipe portion.

18. A natural draft liquid heater as claim in any one of claims 15 to 17, wherein an outlet end of the looping pipe portion forms a terminal portion of the flue that exits a side wall of the liquid chamber.

19. A flue for a natural draft liquid heater the flue including: a base pipe portion comprising internally projecting fins; and a looping pipe portion extending from the base pipe portion, the looping pipe portion having a single loop form.

20. A flue for a natural draft liquid heater as claimed in claim 19, wherein the looping pipe portion is internally baffled.

21. A flue for a natural draft liquid heater as claim in claim 19 or 20, wherein the looping pipe portion is internally corrosion resistant.