GB2083209A - Water heaters - Google Patents

Abstract

A water heater is constituted by a fire basket which has a grate 14 formed by spaced hollow tubes 11, which are interconnected to define a water passage. The upper arms 18 of the tubes are bent to extend across a flue opening. Tubes 11 may be connected in series or in parallel. <IMAGE>

Description

SPECIFICATION A water heater This invention relates to water heaters and in particular, but not exclusively, to domestic water heaters.

In houses and other buildings where fuel is burnt in an open hearth, or fire, considerable heat is wasted. A number of proposals have been made for using this heat to heat water, and the resultant devices are frequently referred to as 'back' boilers.

These boilers have panels in the fire back or sides of the hearth, which incorporate heat exchangers.

These back boilers are both difficult and expensive to instal and maintain.

It is an object of the invention to at least partly overcome or minimise these disadvantages.

According to one aspect the present invention consists in a water heater including a heat exchanger having a first part for supporting solid fuel for combustion and a second part, which is disposed to extract heat from the combustion gases resulting from the combustion of the fuel or air heated by the combustion.

The heat exchanger may be constituted by a plurality of spaced parallel interconnected hollow tubes. The tubes may be connected in parallel or in series and may be generally C-shaped or G-shaped, in which case the lower arms of the tubes may form the first part of the heat exchanger and the upper arms may form the second part.

According to another aspect the invention consists in a firegrate having a grating, at least part of which constitutes at least part of a heat exchanger.

Preferably the heat exchanger extends upwardly and outwardly over at least a part of the grating.

The grating may include a number of spaced hollow tubes. The tubes may be interconnected, in series, or parallel, to define a fluid passage of the heat exchanger. The tubes may define the upwardly and outwardly extending part of the heat exchanger.

The tubes may be generally C-shaped or generally G-shaped. The lower arms of the tubes may be arranged to support solid fuel for combustion.

In a preferred embodiment the fire grate constitutes a part of a fire basket.

The invention also consists in a water heating system including a firegrate or fire basket as hereinbefore defined.

The invention may be performed in a number of ways, specific embodiments of which will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a fire basket; Figure 2 is a side view of the basket of Figure 1 disposed in a hearth; Figure 3 is a diagram showing a fluid path through the fire basket; Figure 4 is a partial front view of an alternative form of grating for a fire basket of the invention; and Figure 5 is a section along the line IV-IV of Figure 4.

The tubes 11 are held apart by 1/2" spacers (not shown) so that there are sufficient gaps to allow the circulation of air and combustion gas between the tubes 11.

The lower arms 14 of the tubes 11 form the grating 15 ofthefire basket 10 and their uprights 16 constitute a fire back 17. The upper arms 18, which are shorter than the lower arms 14, project partly across a flue opening 19 (see Figure 2).

The fire basket 10 is provided with a fluid inlet 20 and a fluid outlet 21, which are interconnected by a fluid passage 22. Fluid passage 22 comprises the hollow interiors 23 of the tubes 11, which are interconnected, in series, at alternate ends by the connectors 24 (see Figure 3), and a return pipe 25, which extends along the front of the basket 10, to connect the last tube 11 to the outlet 21.

In use, a fire is made on the grating 15 and water or other suitable fluid is circulated through the fluid passage 22. The fire heats the tubes 11 by direct conduction, by radiation and by convection of heated air and combustion gases through the upper arms 18. Typically the fluid will be water and the inlet 20 and the outlet 21 will be connected in a hot water or central heating circuit as indicated at 26.

Preferably approximately 50% of the inward facing surface area of the tubes 11 should be in direct contact with the fire.

In the described embodiment the fire basket is for use with solid fuels, but it will be appreciated that baskets of this type can be usefully used with other types of fire, for example with imitation log-burning gas fires.

In the embodiment of Figures 1 to 3 the tubes 11 are interconnected in series and hence provided a long fluid passage 22 over which heat exchange can take place, whereby high water temperatures can be achieved. However in many uses it may be necessary to have a high throughput. In the series arrangement this can only be achieved by using high water pressures and hence an expensive pump and high grade joints.

Figures 4 and 5 show an alternative construction for the grating 15 wherein the tubes 11 are connected in parallel; at their lower ends by an inlet pipe 27 and at their upper ends by an outlet pipe 28. The water enters the pipe 27 at its right end (not shown) and leaves the pipe 28 at an outlet 29 at its lefthand end. As can be best seen in Figure 4 the lower ends 16 of the tubes 11 are bent upwardly (at 30) to enhance the material retaining aspect of the grating and to lengthen the heat transfer path in each tube.

It will further be appreciated that different shaped tubes may be used and that, for example, the upper arms 18 may be omitted. In addition the fence or fender could be incorporated in the fluid passage.

The tubes 11 may be provided with fins or otherwise shaped to increase their effective surface area.

In some circumstances it may be found desirable to limit the size of the heat exchanging part of the tubes, for instance to the upper part of the tubes.

One such circumstance might be if the heat exchanger had the effect of lowering the temperature of the fire below the combustion temperature of the fuel.

Equally it may be desirable to prevent circulation of the water or other fluid until such time as a particular fluid temperature has been achieved.

Claims (16)

1. Awater heater including a heat exchanger having a first part for supporting solid fuel for combustion and a second part, which is disposed to extract heat from the combustion gases resulting from the combustion of the fuel or air heated by the combustion.

2. A water heater as claimed in claim 1, wherein the second part at least partly overhangs or overlies the first part.

3. A water heater as claimed in claim 1 or claim 2, wherein the heat exchanger comprises a plurality of spaced interconnected hollow tubes.

4. A water heater as claimed in any one of the preceding claims, wherein the tubes are connected in parallel or in series.

5. A water heater as claimed in any one of the preceding claims, wherein the tubes are generally C-shaped or generally G-shaped.

6. Awater heater as claimed in claim 5, wherein the lower arms of the tube constitute the first part.

7. A firegrate having a grating, at least part of which constitutes at least part of a heat exchanger.

8. Afiregate as claimed in claim 7, wherein the heat exchanger extends upwardly and outwardly over a portion of the grating.

9. A firegrate as claimed in claim 7 or claim 8, wherein the grating includes a number of spaced hollow tubes.

10. A firegrate as claimed in claim 9, wherein the tubes are interconnected to define a fluid passage of the heat exchanger.

11. A firegrate as claimed in claim 10, wherein the tubes are interconnected in series or in parallel.

12. A firegrate as claimed in any one of claims 9 to 11, wherein the tubes are generally C-shaped or generally G-shaped.

13. A firegrate as claimed in claim 12, wherein the lower arms of the tubes are arranged to support solid fuel for combustion.

14. A water heating system, including a firegrate as claimed in any one of claims 7 to 13.

15. A water heating system substantially as hereinbefore described with reference to the accompanying drawings.

16. A firegrate substantially as hereinbefore described with reference to the accompanying drawings.