Heat exchanger and condensing boiler incorporating a heat exchanger

Abstract

 A heat exchanger (20) for a condensing boiler (100) including a coil (50) formed about a body (40), the heat exchanger (20) including gas direction means to direct the passage of gas passing through the heat exchanger (20) to pass over the body (40) and between the coils of the coil (50).

Description

Field of the Invention

[0001] The present invention relates to a heat exchanger that is particularly applicable for use in condensing boilers.

Background to the Invention

[0002] Condensing boilers (and indeed most other fuel burning systems) use heat exchangers to recover at least some of the heat from hot gasses produced when the fuel is burnt.

[0003] The heat exchangers increase the efficiency of the condensing boiler and are a contributor to the claims of many manufacturers that their domestic condensing boilers are up to 97% efficient.

[0004] An example conventional heat exchanger used in a condensing boiler is illustrated in Figure 1 a and 1 b.

[0005] In Figure 1a and 1b, hot gasses pass through the tubes 10 of the heat exchanger and heat is conducted away via the walls of the tubes 10.

[0006] Whilst heat exchangers do indeed improve fuel efficiency of condensing boilers, they also introduce added complexity, further points of failure and additional components requiring servicing.

[0007] In the heat exchanger of Figure 1 a and 1 b, soot and other deposits will build up in the tubes 10 over time reducing its efficiency. Additionally, it is difficult to improve the efficiency of such a heat exchanger further. Whilst the introduction of more would tubes result in more surface area for conducting heat away, the necessary narrowing of the tubes to fit more within the same volume would mean it would take much less amounts of deposits to block one or more of the tubes.

[0008] In order to service a heat exchanger such as that illustrated in Figure 1, an engineer must remove all of the individual tubes from their housing and wash away any deposits. This is a messy and time consuming job resulting in higher servicing costs.

Statement of Invention

[0009] According to an aspect of the present invention, there is provided a heat exchanger according to claim 1.

[0010] The present invention seeks to provide a heat exchanger which is simpler, is more easily serviceable, and has improved efficiency over known heat exchangers.

[0011] In preferred embodiments, the heat exchanger includes a coil formed about a body, the heat exchanger including gas direction means to direct the passage of gas passing through the heat exchanger to pass over the body and between the coils of the coil.

[0012] The body is preferably elongated, having a greater length than circumference, the coil circumscribing the body along its length.

[0013] The body is preferably substantially cylindrical, the coil being formed along the length of the cylinder.

[0014] Preferably, the coil is hollow and has water passed there-through.

[0015] Preferably, the heat exchanger is used in a heating system, the water passed through the body and coil being subsequently passed to a primary heat exchanger of the heating system for further heating.

[0016] Preferably, the coil is formed from a ribbed tube.

[0017] According to another aspect of the present invention, there is provided a condensing boiler according to claim 7.

Brief Description of the Drawings

[0018] Embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings in which:

Figures 1 a and 1b are schematic diagrams illustrating selected aspects of a conventional heat exchanger used in a condensing boiler;

Figure 2 is a sectional view of a heat exchanger according to an embodiment of the present invention;

Figure 3 is a schematic diagram of a condensing boiler according to an embodiment of the present invention; and,

Figure 4 is a sectional view illustrating aspects of the boiler of Figure 3 in more detail.

Detailed Description

[0019] Figure 2 is a sectional view of a heat exchanger according to an embodiment of the present invention.

[0020] The heat exchanger 20 includes a housing 30 (parts of which have been omitted to enable illustration of the interior of the housing 30), a body 40, a coil 50 formed about the body 40, a gas inlet 60 and a gas outlet 65.

[0021] Hot gasses (marked by arrows labelled 70) enter the housing 30 via gas inlet 60. The body 40 and coil 50 are positioned in the housing 30 immediately in the path of the gasses 70. The gasses therefore pass over the body and between the coils of the coil 50 before escaping the heat exchanger via gas outlet 65. Escaping gasses moving around the body 40 and out of the housing 30 via the gas outlet 65 are marked by arrows labelled 80.

[0022] The coil 50 is preferably hollow and water is pumped or otherwise passed there-through from water inlet 90 to water outlet 95.

[0023] It will be appreciated that although the body 40 is illustrated as a cylinder, it could be of any form. Preferably the body 40 is elongated to present sufficient surface area for the gasses to pass around. The body and/or the coil may be ribbed or otherwise include gas passage prevention means such as cavities or textures to increase the time and/or surface area of contact with the gasses and thereby improve efficiency.

[0024] Figure 3 is a schematic diagram of a condensing boiler according to an embodiment of the present invention. Figure 4 is a sectional diagram illustrating aspects of the boiler of Figure 3 in more detail.

[0025] In this embodiment of the present invention, the heat exchanger 20 is mounted on a condensing boiler 100 so as to act as a secondary heat exchanger.

[0026] A burner 110 fires a fuel/air mixture into the boiler 100 through a hole 111 in a primary heat exchanger 120. The resultant hot gasses from the firing of the fuel/air mixture follow the direction of the arrows 130 around baffles 140 up into the secondary heat exchanger 20. The gasses pass through the secondary heat exchanger in the same manner as discussed in Figure 2 and exit via the gas outlet 65 into a flue discharge.

[0027] Cool water is preferably passed through the coil 50. This is heated via the heat conducted/scrubbed away from the hot gasses. Water outlet 95 is connected to the boiler for further heating before passing into a heating system via outlet 150. Preferably, water that has passed through the heating system (radiators, hot water cylinder etc) is passed back into the secondary heat exchanger via water inlet 90 resulting in a closed system.

[0028] Cold air used by burner 110 is preferably drawn around the outside of the housing 30 of the secondary heat exchanger 120 to further assist in cooling the flue gasses in the boiler 100. By warming air used by the burner, efficiency improvements may be experienced over conventional arrangements.

[0029] It will be appreciated that the secondary heat exchanger is removable and serviceable in its entirety should the need arise. Similarly, the body 40 is removable for cleaning and servicing. Given the reduced number of parts and the fact that there are no narrow tubes to become blocked, it is expected that the heat exchanger 20 of the present invention will be significantly cheaper and easier to service and experience much fewer failures than known heat exchangers.

Claims

1. A heat exchanger including a coil formed about a body, the heat exchanger including gas direction means to direct the passage of gas passing through the heat exchanger to pass over the body and between the coils of the coil.

2. A heat exchanger according to claim 1, wherein the body is preferably elongated, having a greater length than circumference, the coil circumscribing the body along its length.

3. A heat exchanger according to claim 2, wherein the body is substantially cylindrical, the coil being formed along the length of the cylinder.

4. A heat exchanger according to any preceding claim, wherein the coil is hollow and is arranged to pass water there-through.

5. A heat exchanger according to any preceding claim, wherein the coil is formed from a ribbed tube.

6. A heat exchanger as claimed in any preceding claim, further comprising means for drawings cold air used by a burner around the outside of the body to thereby cooling flue gasses.

7. A condensing boiler including a heat exchanger as claimed in any preceding claim.

8. A condensing boiler as claimed in claim 7, wherein the heat exchanger comprises a secondary heat exchanger.

9. A condensing boiler as claimed in claim 8, wherein the body and coil are arranged to be separately removeable from the boiler.

Drawing