GB2279446A

GB2279446A - Oil-fired boiler

Info

Publication number: GB2279446A
Application number: GB9410975A
Authority: GB
Inventors: Andrew John Robertson; Simon Travis Smart
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-06-17
Filing date: 1994-06-01
Publication date: 1995-01-04
Anticipated expiration: 2014-06-01
Also published as: GB2279446B; GB9410975D0; GB9312469D0

Abstract

An oil-fired boiler having a heat exchanger unit therein which comprises outer tubes (22) around which water passes from a water inlet 36 to a water outlet 38 and baffle tubes (28) suspended within the outer tubes 22 for the passage of hot gases between said outer tubes 22 and said baffle tubes 28. The boiler includes a hot gas chamber 12 into which hot gases enter from an oil burner 14. The gases then pass up through tubes 22 around baffle tubes 28 to exit into a gas outlet chamber 32 having an outlet 24 to a flue. <IMAGE>

Description

Oil-Fired Boiler This invention relates to an oil-fired boiler and more especially to a heat exchanger in or for use in an oilfired boiler (domestic or commercial).

According to one aspect of the invention, there is provided an oil-fired boiler having a hot gas inlet chamber in use supplied with hot gases from a burner and a gas outlet chamber from which in use gases exit to a flue, heat exchanger means defining a plurality of separate passages for the passage of hot gases from the inlet chamber to the outlet chamber, and a water enclosure having a cold water inlet and hot water outlet, said enclosure comprising a water jacket surrounding the heat exchanger means and providing for passage of water from the water inlet to the water outlet in heat exchange relationship with the gas passages.

Preferably, in use, the boiler is mounted upright with both the hot gas inlet chamber and the cold water inlet at the bottom and the gas outlet chamber and hot water outlet at the top. For convenience, although without limitative effect, the boiler will be further described with reference to this preferred orientation.

Preferably, therefore, the gas passages extend vertically in spaced parallel relationship, distributed over the horizontal cross-sectional area of the heat exchanger means, and in use the water flows upwardly over the entire cross-sectional area of the exchanger means outside the gas passages.

The gas passages are preferably annular, being defined by inner and outer tubes. The inner tubes are preferably baffle tubes, closed at their bottom ends. These baffle tubes are preferably removably suspended within the outer tubes, and are open at their upper ends to the gas outlet chamber.

In a preferred arrangement, the inner and outer tubes and a means of supporting the same constitute a heat exchanger unit.

Thus, according to another aspect of the invention, there is provided a heat exchanger unit for an oil-fired boiler comprising lower and upper plates (in the preferred orientation of the boiler), said plates having vertically aligned apertures between which are fixedly connected outer tubes in use providing for passage of hot gases upwardly through said outer tubes, and baffle tubes with closed lower ends suspended from the top plate to depend substantially centrally in the outer tubes substantially to the bottom of said outer tubes.

In use, the above-described heat exchanger unit is mounted in a water jacket which provides for passage of water from a water inlet to a water outlet over the entire crosssectional area of the unit outside the outer tubes. Hot gases flow upwardly through the annular passages between the outer tubes and the interior baffle tubes, and are effectively scrubbed to ensure highly efficient transfer of heat to the surrounding water.

As the water inlet and water outlet necessarily have to be located at particular positions around the boiler (although alternative positions and multiple positions for water heating and for central heating may be provided), it is highly preferable to ensure that water does not flow through the jacket directly from the water inlet to the water outlet primarily around the outside of the heat exchanger unit. For preventing this, the lower plate may serve to prevent upward flow of water on the side of the jacket where the water inlet is provided, and be cut with a channel means enabling upward flow of water only on the side of the jacket remote from the water inlet.

A practical arrangement of oil-fired boiler in accordance with the invention will now be described by way of example, making reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cross-sectional elevational view of the boiler; Figures 2 and 3 are diagrammatic horizontal cross-sectional views immediately above and through the heat exchanger unit within the boiler; Figure 4a shows the heat exchanger unit in underplan view, Figure 4b in top view and Figure 4c in elevational view; and Figure 5a shows a baffle tube in plan view, whilst Figures 5b and Sc show the tube in side elevational views at right angles with one another.

The illustrated boiler comprises a cylindrically shaped water jacket 10, mounted with its axis vertical. The lower part of the jacket 10 defines a hot gas chamber 12 into which hot gases enter from an oil burner 14. Above the gas inlet chamber 12 the water jacket 10 has only a single outer wall, so that water can flow into its interior volume 16.

Within this volume 16 is mounted a heat exchanger unit shown separately in Figure 4.

The heat exchanger unit, made for example of mild steel or cast iron or other suitable non-combustible material, comprises lower and upper circular plates 18, 20, which, as will be clear from Figures 2, 3 and 4, have vertically aligned apertures between which are fixed, as by welding or integral casting, a number (as shown eleven) of vertical tubes 22 in spaced relationship distributed over the horizontal cross-sectional area of the unit, although conveniently in less density on the side 24 which would allow the escape of hot gases.

Suspended centrally within the tubes 22 from the upper plate 20, by means of cross-pins 26, are a corresponding number of baffle tubes 28, closed at their lower ends 30 level with the lower ends of the outer tubes 22, as indicated in Figure 1, wherein the lower and upper plates 18, 20 are omitted more clearly to show the flow paths of gases and of water. The baffle tubes 28 are omitted in Figure 4, but one such baffle tube is separately shown in Figure 5.

In Figure 5, a representative baffle tube 28 is shown with closed base 30, its top cross-pin 26 from which the tube depends, and its locating points 29 which ensure correct baffle positioning within the heat exchanger gas tubes 22.

Thus, when the heat exchanger unit is mounted within the boiler, hot gases can pass from the gas inlet chamber 12 up through the tubes 22 around the baffle tubes 28, to exit into a gas outlet chamber 32 having an outlet 34 to a flue. Water can circulate freely around the outside of the outer tubes 22 in passage from a cold water inlet 36 to a hot water outlet 38. Within the relatively narrow annular passage between the outer tubes 22 and baffle tubes 28, the hot gases are effectively scrubbed to ensure maximised heat transfer to the water.

In order to prevent flow of water substantially directly from the water inlet 36 to the water outlet 38 on the outside of the jacket 10, it is convenient, as indicated at 40 in Figure 1, for the lower plate 18 to close the top of the lower part of the jacket 10 on the side of the water inlet and, as indicated at 42 (see also Figure 4), to be provided with a channel which provides for upward flow of water into the upper part of the jacket on the side opposite to the water inlet. As indicated at 44 in Figure 3, it would alternatively be possible to provide a radial wall in the jacket 10.

In practice, the boiler is provided with two water inlets and water outlets, either for alternative use or for separate flow of hot water for hot water supply.

The boiler is also equipped, at the top of the jacket on the side of the burner, with pockets 46 (see Figure 4) for a temperature control thermostat and a high limit (prevention of boiling) thermostat.

Various modifications of the above-described arrangement are possible within the scope of the invention hereinbefore defined. It is important, however, to provide relatively narrow passages for gas flow through the exchanger in order to achieve maximised heat exchange.

Claims

1. An oil-fired boiler having a hot gas inlet chamber in use supplied with hot gases from a burner and a gas outlet chamber from which in use gases exit to a flue, heat exchanger means defining a plurality of separate passages for the passage of hot gases from the inlet chamber to the outlet chamber, and a water enclosure having a cold water inlet and hot water outlet, said enclosure comprising a water jacket surrounding the heat exchanger means and providing for passage of water from the water inlet to the water outlet in heat exchange relationship with the gas passages.

2. A boiler according to claim 1, the boiler being mounted upright with both the hot gas inlet chamber and the cold water inlet at the bottom and the gas outlet chamber and hot water outlet at the top.

3. A boiler according to claim 2, wherein the gas passages extend vertically in spaced parallel relationship, distributed over the horizontal cross-sectional area of the heat exchanger means, and in use the water flows upwardly over the entire cross-sectional area of the exchanger means outside the gas passages.

4. A boiler according to claim 3, wherein the gas passages are annular, being defined by inner and outer tubes.

5. A boiler according to claim 4, wherein the inner tubes are baffle tubes, closed at their bottom ends.

6. A boiler according to claim 5, wherein the baffle tubes are removably suspended within the outer tubes, and are open at their upper ends to the gas outlet chamber.

7. A heat exchanger unit for an oil-fired boiler comprising lower and upper plates (in the preferred orientation of the boiler), said plates having vertically aligned apertures between which are fixedly connected outer tubes in use providing for passage of hot gases upwardly through said outer tubes, and baffle tubes with closed lower ends suspended from the top plate to depend substantially centrally in the outer tubes substantially to the bottom of said outer tubes.

8. A heat exchanger unit according to claim 7, mounted in a water jacket which provides for passage of water from a water inlet to a water outlet over the entire crosssectional area of the unit outside the outer tubes.

9. A heat exchanger unit according to claim 8, wherein means are provided to ensure that water does not flow through the jacket directly from the water inlet to the water outlet primarily around the outside of the heat exchanger unit.

10. A heat exchanger unit according to claim 9, wherein the lower plate serves to prevent upward flow of water on the side of the jacket where the water inlet is provided, and is cut with a channel means enabling upward flow of water only on the side of the jacket remote from the water inlet.

11. An oil-fired boiler substantially as hereinbefore described with reference to the accompanying drawings.

12. A heat exchanger unit substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.