GB2581487A

GB2581487A - Stove

Info

Publication number: GB2581487A
Application number: GB1902146.8A
Authority: GB
Inventors: Archer James
Original assignee: Efficiency People Trading Ltd
Current assignee: Efficiency People Trading Ltd
Priority date: 2019-02-15
Filing date: 2019-02-15
Publication date: 2020-08-26
Also published as: GB201902146D0

Abstract

A stove 100 for heating a room comprises a solid fuel combustion chamber 120 and a heat exchanger 110 comprising a conduit 111 is positioned between the combustion chamber and exhaust opening 130. Heat is transferred to ambient air as it flows from the inlet 114 to the higher outlet 112. The conduit may be at least partly sloped. The conduit’s surface may be grooved or curved. The stove may comprise a first baffle 140 defining an emission chamber 150 in which the exchanger is located. The stove may comprise a second baffle 160 in the emission chamber to direct heated gas towards the exchanger, the second baffle may be U shaped. The stove may comprise fire bricks 190. The exchanger may comprise a plurality of conduits. The stove (300, figure 2) may be double sided with a first (312a-e, figure 2) and second (312f-j, figure 2) group of conduits on opposing sides. The heat exchanger may be removable. An installable heat exchanger comprising connector plates is also claimed.

Description

The present invention relates to a stove for heating a room by burning solid fuel such as wood or coal. The stove may be single sided for providing heat to a single room or double sided for providing heat to two rooms. The stove may be a multi-fuel stove, e.g. able to burn both wood and coal.

Stoves are used to combust solid fuel such as coal or wood to emit heat energy for heating a space such as a room in a building. Important parameters for measuring a performance of a stove include the efficiency of the stove (i.e. how much fuel is used versus how much heat energy is produced) and an emissions rating of the stove (i.e. how many unwanted emissions are generated when using the stove). Stoves may be subject to regulatory tests such as efficiency tests and/or emissions tests before the stoves are approved for use. The regulatory tests may be set by environmental government bodies tasked with ensuring that stoves are sufficiently efficient and do not produce more than a threshold amount of unwanted emissions. Unwanted emissions may, for example, include carbon monoxide, NOx gases, particulate matter such as carbon, etc. Conventional stoves comprise a fuel chamber for combusting fuel and an opening for conveying combustion emissions from the fuel chamber to atmosphere. Conventional stoves may be too inefficient and/or produce too many unwanted emissions to pass regulatory tests. Conventional double sided stoves in particular may be too inefficient and/or produce too many unwanted emissions. It is desirable to provide a stove that overcomes or mitigates one or more problems of the prior art whether identified herein or elsewhere.

According to a first aspect of the invention there is provided a stove for heating a room comprising a fuel chamber for combusting solid fuel, an opening for conveying heated gas from the fuel chamber to a flue, and a heat exchanger located in a pathway of the heated gas between the fuel chamber and the opening, the heat exchanger being configured to transfer heat from the heated gas to ambient air, wherein the heat exchanger comprises a conduit configured to convey the ambient air, and wherein an outlet of the conduit is higher than an inlet of the conduit.

The stove according to the first aspect of the invention advantageously achieves greater efficiency, reduces the extent of incomplete burning and reduces the production of unwanted emissions compared to conventional stoves. Rather than heat energy carried by the heated gas escaping to atmosphere via the opening, the heat energy is transferred to ambient air in the space to be heated (e.g. a room of a building) via the heat exchanger before the heated gas exits the stove via the opening. The stove according to the first aspect of the invention has successfully passed emissions and efficiency tests in the UK.

It will be understood that a stove has a normal operating orientation in which legs of the stove are in contact with a surface such as flooring or the ground so as to support the stove. In the normal operating orientation the outlet of the conduit is further from the ground than the inlet of the conduit (i.e. the outlet is higher than the inlet). Having the outlets of the conduits higher than the inlets of the conduits advantageously promotes a flow of ambient air through the conduit due to heated ambient air being allowed to rise as the heated ambient air travels through the conduit. The promotion of the flow of ambient air through the conduit improves the rate of heat exchange between the heated gas and the ambient air. This in turn advantageously reduces heat loss via the opening of the stove and thereby improves an efficiency of the stove.

The flow of ambient air through the conduits may be thought of as a self-replenishing heat sink of the heat exchanger. The heat exchanger may be described as being a passive heat exchanger because it does not require its own source of power separate from the stove to operate. The opening may be connected to a flue collar, which in turn may be connected to a flue.

At least part of the conduit may be sloped between the inlet and the outlet.

A sloped conduit advantageously encourages convection currents of ambient air through the conduit during use of the stove. The convection currents of ambient air act as a heat sink which encourages further transfer of heat energy from the heated gas to the ambient air. With more heat energy being transferred to the ambient air rather than being lost via the opening, an efficiency of the stove is increased. The conduit may be described as being sloped such that heated ambient air rises through the conduit. The conduit may have a constant non-zero gradient between the inlet and the outlet. The conduit may have a varying gradient between the inlet and the outlet. The conduit may be at least partially curved to encourage ambient air flow through the conduit. The conduit may not include any horizontal sections. The conduit may always have a nonzero gradient between the inlet and the outlet.

An angle of the slope of the conduit may be more than about 20°. An angle of the slope of the conduit may be less than about 500.

The slope of the conduit may be relative to a floor of the stove or relative to a flat surface on which the stove is located.

The angle of the slope of the conduit may be about 300.

A surface of the conduit may be grooved or curved.

Using a conduit having a grooved or curved surface advantageously improves the ability of the heat exchanger to transfer heat energy by increasing a surface area of the conduit. The surface of the conduit may be corrugated.

The stove may further comprise a first baffle extending across a portion of the fuel chamber so as to form an emissions chamber between the fuel chamber and the opening. The heat exchanger may be located within the emissions chamber.

The first baffle advantageously reduces turbulence within the fuel chamber and promotes air flow towards the heat exchanger. The first baffle may be generally U-shaped. The first baffle may be configured to reflect at least some combustion heat energy back into the fuel chamber thereby increasing a temperature of the fuel chamber, reducing the extent of incomplete burning and reducing the production of unwanted emissions.

The stove may further comprise a second baffle located in the emissions chamber. The second baffle may be configured to direct the heated gas towards the heat exchanger.

The second baffle advantageously encourages heat exchange between the conduit and the emissions, thereby further improving an efficiency of the stove. The first baffle and the second baffle advantageously provide a compact arrangement (e.g. the top of the stove may be no more than 10 cm above the top of an opening to the fuel chamber) which avoids the need for an additional bulky section on top of the stove to house the heat exchanger. This advantageously increases the installation freedom of a user of the stove allowing the stove to be installed in smaller spaces without comprising on efficiency and emissions performance of the stove.

The second baffle may be generally U shaped A U shaped second baffle advantageously guides heated gas to the heat exchanger whilst also catching particulate matter emitted form combustion of fuel in the fuel chamber. By catching particulate matter and removing the particulate matter from the emissions escaping the stove via the opening, fewer unwanted emission are allowed to escape to atmosphere, thereby improving an emissions rating of the stove.

The fuel chamber may comprise a fire brick that is between about 40 mm and about 100 mm thick.

Using thicker fire bricks (e.g. between 40 mm and 100 mm, e.g. 50 mm) in the fuel chamber raises the temperature of the fuel chamber during use which improves an emissions rating of the stove because less incomplete combustion takes place and fewer unwanted emissions are produced. Using thicker fire bricks (e.g. between 40 mm and 100 mm, e.g. 50 mm) in a conventional stove would reduce a thermal output of the stove because more heat is kept in the fuel chamber and eventually lost to the opening, thereby reducing the conventional stove's efficiency. However, the heat exchanger acts to transfer at least some of the heat (that would otherwise be lost to the opening) to the ambient air of the space that is to be heated. Thus, the heat exchanger enables thicker fire bricks to be used in the fuel chamber without negatively affecting an efficiency of the stove. The thicker fire bricks increase a temperature of the fuel chamber during use of the stove which advantageously results in a reduction of incomplete combustion of fuel. This in turn reduces the generation of unwanted emissions that may have a negative effect on the environment and/or the health of humans. Unwanted emissions may, for example, include carbon monoxide, NOx gases, and particulate matter such as carbon, etc. The heat exchanger may comprise a plurality of conduits.

Using a plurality of conduits advantageously increases a surface area of the heat exchanger and thereby encourages further heat exchange from the emissions to the stove. The heat exchanger may comprise sixteen conduits. The heat exchanger may comprise ten conduits. The heat exchanger may comprise five conduits The heat exchanger may comprise three conduits.

The stove may be a double sided stove. The heat exchanger may comprise a first group of conduits located at a first side of the stove and a second group of conduits located at an opposing side of the stove.

Using a heat exchanger comprising different groups of conduits located at opposing sides of the stove advantageously brings the emissions into thermal contact with a greater number of conduits, thereby improving heat exchange from the emissions to the stove. For example, the heat exchanger may comprise a first group of five conduits proximate a first side of the stove and a second group of five conduits proximate an opposing side of stove. Using a heat exchanger comprising different groups of conduits located at different parts of the stove may be particularly advantageous in a double-sided stove as turbulence of the flow of heated gas through the stove is reduced thereby improving an efficiency and emissions rating of the stove.

The heat exchanger may be removable.

Using a removable heat exchanger advantageously increases an operational lifetime of the stove because the heat exchanger can easily be removed for maintenance and/or replaced without affecting the rest of the stove.

According to a second aspect of the invention, there is provided a heat exchanger configured to be installed in a pathway of heated gas between a fuel chamber and an opening of a stove for burning solid fuel, the heat exchanger comprising a first connector plate, a second connector plate, and a plurality of conduits extending between the first and second connector plates. Each conduit comprises an inlet through the first connector plate and an outlet through the second connector plate. The first connector plate is substantially perpendicular to the second connector plate.

The heat exchanger may be retrofitted to existing stoves to improve their efficiency and emissions rating.

Surfaces of the conduits may be curved or grooved.

The surfaces of the conduits may be corrugated.

The first and second connector plates may comprise attachment means for removably attaching the heat exchanger to the stove.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying figures, in which: Figure 1 schematically depicts a cross sectional view from the side of a single sided stove comprising a heat exchanger according to an embodiment of the invention; Figure 2 is a perspective view of the front of a double sided stove according to an embodiment of the invention; Figure 3 is a perspective view of a portion of the double sided stove of Figure 2; Figure 4 is an alternative perspective view of part of the stove of Figure 2 and Figure 3; Figure 5 is another alternative perspective view of a portion of the stove of Figures 2-4; Figure 6 is a perspective view from beneath a portion of the stove of Figures 2-5; Figure 7, consisting of Figures 7A-7C, depicts three different views of a heat exchanger according to an embodiment of the invention installed on fire bricks of a fuel chamber; and, Figure 8 is a perspective view of the heat exchanger depicted in Figure 7.

Figure 1 schematically depicts a cross sectional view from the side of a single sided stove 100 comprising a heat exchanger 110 according to an embodiment of the invention. The stove 100 comprises a fuel chamber 120 for combusting fuel (not shown). The fuel chamber 120 may be referred to as a firebox. The fuel chamber 120 may comprise one or more fire resistant materials, e.g. steel, ceramic, firebricks, etc. The fuel chamber 120 is accessible via a door 180 comprising a handle 185. The door 185 may, for example, be formed from cast iron. The handle 185 may operate a lock 187 to lock and unlock the door 180 as desired. The door 180 may be opened to replace fuel, ignite fuel and/or remove surplus ash from the fuel chamber 120. The door 180 may comprise a transparent panel (not shown) for allowing visual inspection of the fuel chamber 120. The transparent panel may, for example, comprise glass. The door 180 may comprise a seal (not shown) for reducing leakage of emissions from the fuel chamber 120 to the surroundings of the stove 100.

The fuel chamber 120 may comprise thermal insulation 190. The thermal insulation may, for example, comprise one or more fire bricks. Conventional stoves use conventional fire bricks having thicknesses of no more than about 35 mm. The fire bricks 190 for use with the present invention may, for example, have a thickness of about 40 mm or more. The fire bricks 190 may, for example, have a thickness of about 100 mm or less. The fire bricks 190 may, for example, have a thickness of about 50 mm. The fire bricks 190 act to increase a temperature within the fuel chamber 120 during use. The fire bricks 190 may, for example, comprise vermiculite. Increasing the temperature of the fuel chamber 120 during use advantageously encourages more complete burning of fuel which in turn reduces the production of unwanted emissions.

The fuel chamber 120 further comprises a floor 200. The floor 200 may comprise a grating configured to support solid fuel whilst allowing air flow from beneath the grating into the fuel chamber 120. Gaps in the grating may, for example be about 15 mm wide. The fuel chamber 120 may further comprise a protrusion 210 extending from the floor 200 for retaining fuel within the fuel chamber 120. The grating may be removable for cleaning and maintenance. The fuel may comprise any suitable combustion material such as, for example, wood, paper, coal, kindling sticks, firelighters, etc. The stove 100 further comprises legs 240 for supporting the stove 100 on a surface such as a floor of a room in which the stove 100 is installed.

The stove 100 may comprise air flow control means configured to control the amount of oxygen available for combusting the fuel in the fuel chamber 120. The air flow control means may comprise one or more actuators 250 connected to one or more valves 252, 254. The actuator may be configured to move the valves 252, 254 (e.g. slide and/or rotate the valves) between a closed position in which oxygen cannot pass through one or more of the valves 252, 254 to the fuel chamber 120 and an open position in which oxygen can pass through one or more of the valves 252, 254 to the fuel chamber 120. When the one or more valves 252, 254 are in the open position the actuator 250 may be used to expand or contract an opening of the valves 252, 254 in order to control the amount of oxygen that is permitted through the valves 252, 254 to the fuel chamber 120. The stove 100 may further comprise one or more apertures 280 for allowing some heated air to escape the stove 100.

A top 188 of the stove 100 may be no more than 10 cm from a top 124 of an opening to the fuel chamber 120. The stove 100 may, for example, have a width of about 40 cm or more. The stove 100 may, for example, have a width of about 60 cm or less. For example, the stove 100 may have a width of between about 50 cm and about 58 cm, e.g. about 54 cm. The stove 100 may, for example, have a height 290 of about 50 cm or more (excluding the flue collar 132). The stove 100 may, for example, have a height 290 of about 70 cm or less (excluding the flue collar 132). For example, the stove 100 may have a height 290 of about 60 cm (excluding the flue collar 132). The flue collar 132 may, for example, have a height of between about 5 cm and about 6 cm, e.g. about 5.5 cm. The stove 100 may, for example, have a depth 295 of about 50 cm or more. The stove 100 may, for example, have a depth 295 of about 70 cm or less.

The stove 100 may, for example, have a depth 295 of about 60 cm.

The stove 100 may, for example, be configured to output 3 kW or more of heat. The stove 100 may, for example, be configured to output about 10 kW or less of heat. For example, the stove 100 may be configured to output about 7 kW of heat.

The stove 100 further comprises an opening 130 for conveying emissions (not shown) from the fuel chamber 120 to a flue (not shown). In the example of Figure 1, a flue collar 132 is attached to the opening 130. The flue collar 132 is configured to be attached to a flue.

The stove 100 further comprises a first baffle 140 extending across a portion of the fuel chamber 120 so as to form an emissions chamber 150 between the fuel chamber 120 and the opening 130. In the example of Figure 1, the heat exchanger 110 is at least partially located in the emissions chamber 150. The stove 100 further comprises a second baffle 160 located in the emissions chamber 150. The second baffle 160 is configured to direct heated gas towards the heat exchanger 110. The first baffle 140 and/or the second baffle 160 may be shaped and/or sloped so as to allow for positioning the heat exchanger 110 in a compact space within the emissions chamber 150. For example, the first baffle 140 may be substantially U-shaped. The first baffle 140 may sloped so as to promote a flow of heated gas towards a front of the stove 100, through a gap 123 between the front of the stove 100 and the first baffle 140 and into the emissions chamber 150. The second baffle 160 may be substantially U-shaped. A closed end of the second baffle 160 may face the gap 123 between the front of the stove 100 and the first baffle 140. Heated gas approaching the second baffle 160 from the gap 123 may be diverted around one or both sides of the second baffle 160 and thereby be blocked from immediately exiting the opening 130 thermally interacting with the heat exchanger 110. The second baffle 160 may cause the heated gas to be incident on the conduit of the heat exchanger from different directions. As the heated gas travels along the sides of the second baffle 160 the heat gas comes into thermal communication with the conduit 111 of the heat exchanger 110. The heated gas transfers at least some heat to the conduit 111 before exiting the stove 100 via the opening 130.

The heat exchanger 110 is located in a pathway 260 of the heated gas between the fuel chamber 120 and the opening 130. The heat exchanger 110 is suitable for transferring heat from the heated gas in the emissions chamber 150 to ambient air present within the heat exchanger 110. In the example of Figure 1, the heat exchanger 110 comprises a conduit 111. The conduit 111 is configured to convey ambient air through the stove 100. An outlet 112 of the conduit 111 is higher than an inlet of the conduit 111. The inlet 114 and the outlet 112 are open to the stove's surroundings (i.e. open to ambient air). In the example of the single sided stove 100 of Figure 1, the inlet 114 of the heat exchanger 110 is located proximate a back 183 of the stove 100 (i.e. proximate a surface of the stove 100 that opposes the door 180) whilst the outlet 112 of the heat exchanger 110 is located at a top 188 of the stove 100.

At least part of the conduit 111 may be sloped between the inlet 114 and the outlet 112. In the example of Figure 1, there is a constant gradient between the inlet 114 and the outlet 112 of the conduit 111. The gradient of the conduit 111 between the inlet 114 and the outlet 112 may vary. An angle of the slope of the conduit 111 (e.g. relative to the floor 200 of the stove 100) is greater than 0°. An angle of the slope of the conduit 111 (e.g. relative to the floor 200 of the stove 100) is less than 90°. Decreasing the angle of the slope of the conduit 111 may reduce a flow rate of ambient air through the conduit 111 because heated ambient air is less easily able to rise through the conduit 111. The flow rate of ambient air through the conduit 111 may at least partially determine a rate of heat exchange between the heat exchanger 110 and the ambient air. Reducing the flow rate of air though the conduit 111 by too much may negatively affect a rate of heat exchange between the heat exchanger 110 and the ambient air. If the stove 100 is installed proximate a surface (e.g. a wall) then increasing the angle of the conduit 111 may restrict air flow into the inlet 114 of the conduit 111 because heated air exiting the outlet 112 may interfere with the flow of air entering the inlet 114.

The angle of the slope of the conduit 111 may therefore be selected so as to achieve efficient heat exchange between the heat exchanger 110 and the ambient air. The angle of the slope of the conduit 111 (e.g. relative to the floor 200 of the stove 100) may, for example, be between about 20° and about 50°, e.g. about 30°.

A surface 113 of the conduit 111 may be grooved and/or curved so as to increase a surface area of the conduit 111. Increasing the surface area of the conduit 111 advantageously improves a heat exchange rate of the heat exchanger 110. For example, the conduit 111 may have a surface 113 having a generally sinusoidal curve and/or groove, a saw-tooth shape and/or groove, a square wave shape and/or groove, etc. The surface 113 of the conduit 111 may have a corrugated pattern so as to increase its surface area. The heat exchanger 110 may comprise a plurality of conduits 111. The heat exchanger may comprise three or more conduits 111. The heat exchanger may comprise eight or less conduits 111. The heat exchanger 110 may comprise five conduits 111. Increasing the number of conduits 111 increases a surface area of the heat exchanger 1110 which in turn promotes heat exchange between the heat exchanger 110 and ambient air in the conduits 111. However, increasing the number of conduits 111 may increase the cost of manufacturing the heat exchanger 110. The number of conduits 111 in the heat exchanger 110 may be selected so as to achieve a desired rate of heat exchange between the heat exchanger and ambient air whilst not surpassing a threshold cost of manufacturing the heat exchanger 110. Each of the plurality of conduits 111 may have a surface 113 that is curved or grooved or corrugated surface as discussed above.

Combusting fuel in the fuel chamber 120 generates heat. At least a portion of the generated heat is carried by a convection current of heated gas along the pathway 260. The heated gas may, for example, comprise heated air and combustion emissions. The heated gas generally rises within the fuel chamber 120. The heated gas generally travels along the pathway 260 through the fuel chamber 120 before being directed to the emissions chamber 150 by the first baffle 140. The heated gas is redirected towards the heat exchanger 110 by the second baffle 160. The heated gas heats the conduit 111 of the heat exchanger 110 as the heated gas passes around the conduit 111. As the conduit 111 gains heat energy from the heated gas the temperature of the conduit 111 increases. Ambient air present within the conduit 111 receives heat energy from the heated conduit 111 and becomes heated ambient air. The heated ambient air then rises through the conduit 111 and exits the conduit 111 via the outlet 112. A flow path of heated ambient air 117 passing through the conduit 111 is shown in Figure 1. The heated ambient air that exits the outlet 112 is replaced by ambient air entering the inlet 114 of the conduit 111. That is, the heated ambient air that escapes the outlet 112 is replaced by cooler ambient air entering the inlet 114. This results in a current of ambient air passing through the conduit 111. The conduit 111 is able to draw cooler ambient air into its inlet 114 by means of cooling the heated gas as the heated gas passes the conduit 111 in the emissions chamber 150.

Having the outlet 112 of the conduit 111 higher than the inlet 114 of the conduit 111 advantageously promotes the current of ambient air 117 passing through the conduit 111 due to the heated ambient air being allowed to rise through the conduit 111. The promotion of the current of ambient air passing through the conduit 111 improves the rate of heat exchange between the heated gas in the emissions chamber 150 and the ambient air in the conduit 111. This in turn advantageously reduces heat loss via the opening 130 and thereby improves an efficiency of the stove 100. The fire bricks 190 in the fuel chamber 120 act to thermally insulate the fuel chamber 120 and thereby increase a temperature within the fuel chamber 120 during combustion of solid fuel.

Increasing the temperature of the fuel chamber 120 during combustion of solid fuel reduces the extent of incomplete burning occurring in the fuel chamber 120 and thereby improves an emissions rating of the stove 100 because fewer unwanted emissions are produced. The flow of ambient air 117 through the conduit 111 may be thought of as a self-replenishing heat sink of the heat exchanger 110.

Generally, the heat exchanger 110 allows at least some heat that would otherwise be lost out of the opening 130 to be transferred to ambient air within the space that is to be heated by the stove 100. This improves an efficiency of the stove 100. Using thicker fire bricks 190 (e.g. between 40 mm and 100 mm, e.g. 50 mm) in the fuel chamber 120 raises the temperature of the fuel chamber 120 during use which improves an emissions rating of the stove 100 because less incomplete combustion takes place and fewer unwanted emissions are produced. Using thicker fire bricks 190 in a conventional stove would reduce a thermal output of the stove because more heat is kept in the fuel chamber and eventually lost to the opening, thereby reducing the conventional stove's efficiency. However, the heat exchanger 110 acts to transfer at least some of the heat that would otherwise be lost to the opening 130 to the ambient air of the space that is to be heated. Thus, the heat exchanger 110 enables thicker fire bricks 190 to be used in the fuel chamber 120 without negatively affecting an efficiency of the stove 100.

The second baffle 160 may be located on top of the first baffle 140. The top 188 of the stove 100 may be no more than 10 cm above the top of an opening to the fuel chamber 120. The compact arrangement of the heat exchanger 110 within the emissions chamber 150 and the first and second baffles 140, 160 advantageously allows these improvements in efficiency and emissions rating to be realised without compromising the size and/or design of the stove 100. That is, the heat exchanger 110 is compact enough to not significantly affect the size of the stove 100, meaning that the stove 100 may be installed in relatively compact spaces.

The heat exchanger 110 may be removable. Using a removable heat exchanger 110 advantageously increases an operational lifetime of the stove 100 because the heat exchanger 110 can easily be removed for maintenance and/or replaced without affecting the rest of the stove 100.

Figure 2 is a perspective view of the front of a double sided stove 300 comprising a heat exchanger (not shown) according to an embodiment of the invention. A double sided stove 300 comprises two opposing transparent panels 301, 302 that allow the fuel chamber 320 to be viewed from opposing directions. One of the transparent panels 301 may form part of a door (not shown) of the stove 300. Components of the stove 300 are similar to the components of the stove 100 shown in Figure 1. That is, the stove 300 comprises a fuel chamber 320 for combusting fuel (not shown), thermal insulation 390, a floor 200 comprising a grating, legs 240 for supporting the stove 300, air flow control means (not shown), similar dimensions (i.e. width, height and depth), an opening 330 for conveying emissions and a flue collar 332. However, due to there being two transparent panels 301, 302 rather than one, the double sided stove 300 may emit more heat than the single sided stove 100. The double sided stove 300 may, for example, output 8 kW or more of heat. The double sided stove 300 may, for example, output 15 kW or less of heat. For example, the double sided stove 300 may output about 12 kW of heat.

In the example of Figure 2, the stove 300 comprises a heat exchanger having a plurality of conduits (not shown). Outlets 312a-j of the conduits are visible in Figure 2. The outlets 312a-j are located on a top panel 305 of the stove 300. A top 305 of the stove 300 may be no more than 10 cm from a top 324 of an opening to the fuel chamber 320.

Figure 3 schematically depicts a perspective view of a portion of the double sided stove 300 of Figure 2. Some components (e.g. walls) of the stove 300 are missing in Figure 3 such that internal parts of the stove 300 are visible. Part of a flow path of air 313 through the stove 300 is shown in Figure 3. Air enters the stove 300 from underneath the stove 300 via holes 308. During operation (i.e. during combustion in the fuel chamber 320) the air flows along a channel 342 located between an inner plate 343 and an outer plate 344 proximate a base 315 of the stove 300. The air then travels up the channel 342 along a side 316 of the stove 300. The air then travels along a back (not shown) of the stove 300 before being directed into the fuel chamber 320 by a third baffle 345. In the fuel chamber 320, oxygen in the air contributes to the combustion of fuel. The combustion of fuel generates heated gas. A flow path of gas through the stove 300 is shown in Figure 4.

Figure 4 schematically depicts an alternative perspective view of the stove 300 of Figure 2 and Figure 3. Some components (e.g. walls) of the stove 300 are missing in Figure 4 such that internal parts of the stove 300 are visible. Combusting fuel in the fuel chamber 320 generates heat. At least a portion of the generated heat is carried by a convection current of heated gas along flow paths 318. The heated gas may, for example, comprise heated air and combustion emissions. The heated gas generally rises within the fuel chamber 320. The heated gas generally travels along the flow paths 318 through the fuel chamber 320 before being directed to the emissions chamber 350 by a first baffle 340. The heated gas is then directed towards the heat exchanger 310 by a second baffle 360. The second baffle 360 may split the flow of heated gas amongst different parts 370, 372 of the heat exchanger 310. The second baffle 360 may receive a flow of heated gas from a front of the stove 300 and/or a back of the stove 300. In the example of Figure 4, only the flow of heated gas from the front of the stove 300 is shown.

The first baffle 340 is generally U shaped. The second baffle 360 is generally U shaped. The second baffle 360 is located on top of the first baffle 340. The first baffle 340 is perpendicularly oriented with respect to the second baffle 360. Curved portions of the first baffle 340 and the second baffle 360 force incident heated gas to change direction and/or slow down. The change in direction and/or slowing of the heated gas caused by the first and second baffles 340, 360 cause at least some particulate matter to be taken out of the flow of heated gas and be deposited on the first and second baffles 340, 360. As the heated gas travels around and amongst the conduits 311a-j the heated gas must change direction and may slow down. This may also lead to more particulate matter being taken out of the flow of heated gas and being deposited on the heat exchanger 310. The example of Figure 4 shows heated gas changing direction as it enters the emissions chamber 350, changing direction to move past the second baffle 360, changing direction to drop down along walls of the first baffle 340 and turning amongst conduits 311a-j of the heat exchanger 310. All of these changes in direction of the heated gas may contribute to removing particulate matter form the heated gas.

Removing particulate matter from the heated gas advantageously improves an emissions rating of the stove 300 because fewer unwanted emissions reach the opening and escape to atmosphere.

Inlets 314a-j of the conduits 311a-j may be arranged so as to neighbour a lower portion (e.g. a vertical wall) of the first baffle 340. Outlets 312 ad of the conduits 311 ad may be arranged so as to neighbour an upper portion of the second baffle 360. The conduits 311a-j of the heat exchanger 310 may therefore extend between a lower portion of the first baffle 340 and an upper portion of the second baffle 360. This forms a compact arrangement which advantageously avoids the need to add another section to the top of the stove to house the heat exchanger. For example, the height of the stove may be similar to the height of conventional stoves which allows installation of the stove in spaces that conventional stoves can be installed in.

In the example of Figure 4, the heat exchanger 310 comprises ten conduits 311a-e, 311j (other conduits i.e. 311f-i, are not visible in Figure 4). The heat exchanger 310 may comprise more than ten conduits 311a-e, 311j, e.g. up to sixteen conduits. The heat exchanger 310 may comprise less than ten conduits 311a-e, 311j, e.g. down to six conduits. Using a plurality of conduits 311a-e, 311j increases a surface area of the heat exchanger 310 which in turn advantageously improves the rate of heat exchange between the heated gas in the emissions chamber 350 and ambient air in the conduits 311ae, 311j. This in turn advantageously reduces heat loss via the opening (not shown) and thereby improves an efficiency of the stove 300.

In the example of Figure 4, the heat exchanger 310 comprises a first group 370 of conduits 311a-e located at a first side (not shown) of the stove 300 and a second group 372 of conduits 311 f-j located at an opposing side 373 of the stove 300. The opening (not shown) may be located between the first group 370 of conduits 311a-e and the second group 372 of conduits 311 f-j. Using a heat exchanger 310 comprising different groups 370, 372 of conduits 311a-j located at different sides of the stove 300 advantageously brings the heated gas into thermal communication with a greater number of conduits 311a-j, thereby improving heat exchange from the heated gas to ambient air within the conduits 311a-j.

The heated gas heats the conduits 311a-j of the heat exchanger 310 as the heated gas passes around the conduits 311a-j. As the conduits 311a-j gain heat energy from the heated gas the temperature of the conduits 311a-j increases. Ambient air present within the conduits 311a-j receives heat energy from the conduits 311a-j and becomes heated ambient air. The heated ambient air then rises through the conduits 311a-j and exits the conduits 311a-j via the outlets 312a-j. Flow paths of heated ambient air 317 passing through the conduits 311a-j are shown in Figure 4. The heated ambient air that exits the outlets 312a-j is replaced by cooler ambient air entering the inlets 314a-j of the conduits 311a-j. This results in a current of ambient air passing through the conduits 311a-j. The conduits 311a-j are able to draw cooler ambient air into their inlets 314a-e (other inlets 314-f-j are not visible in Figure 4) by means of cooling the heated gas as the heated gas passes the conduits 311a-j in the emissions chamber 350.

Having the outlets 312a-j of the conduits 311a-j higher than the inlets 314a-j of the conduits 311a-j advantageously promotes the current of ambient air 317 passing through the conduits 311a-j due to the heated ambient air being allowed to rise through the conduits 311a-j. The promotion of the current of ambient air passing through the conduits 311a-j improves the rate of heat exchange between the heated gas in the emissions chamber 350 and the ambient air 317 in the conduits 311a-j. This in turn advantageously reduces heat loss via the opening (not shown) and thereby improves an efficiency of the stove 300. The fuel chamber 320 is kept at a higher temperature which reduces the extent of incomplete burning occurring and thereby improves an emissions rating of the stove 300. The flow of ambient air 317 through the conduits 311a-j may be thought of as a self-replenishing heat sink of the heat exchanger 310.

Generally, the heat exchanger 310 allows at least some heat that would otherwise be lost out of the opening (not shown) to be transferred to ambient air within the space that is to be heated by the stove 300 (e.g. a room of a building). This improves an efficiency of the stove 300. Using thicker fire bricks 390 (e.g. between 40 mm and 100 mm, e.g. 50 mm) in the fuel chamber 320 raises the temperature of the fuel chamber 320 during use which improves an emissions rating of the stove 300 because less incomplete combustion takes place and fewer unwanted emissions are produced. Using thicker fire bricks 390 in a conventional stove would reduce a thermal output of the stove because more heat is kept in the fuel chamber and eventually lost to the opening, thereby reducing the conventional stove's efficiency. However, the heat exchanger 310 acts to transfer at least some of the heat that would otherwise be lost to the opening (not shown), thereby enabling thicker fire bricks 390 to be used in the fuel chamber 320 without negatively affecting an efficiency of the stove 300.

The compact arrangement of the heat exchanger 310 and the first and second baffles 340, 360 advantageously allows these improvements in efficiency and emissions rating to be realised without negatively affecting the size and/or design of the stove 300. That is, the heat exchanger 310 is compact enough to not significantly affect the size of the stove 300, meaning that the stove 300 may be installed in relatively compact spaces, e.g. an alcove of a room.

The heat exchanger 310 may be removable. Using a removable heat exchanger 310 advantageously increases an operational lifetime of the stove 300 because the heat exchanger 310 can easily be removed for maintenance and/or replaced without affecting the rest of the stove 300.

Figure 5 schematically depicts another alternative perspective view of a portion of the stove 300 of Figures 2-4. Some components (e.g. walls) of the stove 300 are missing in Figure 5 such that internal parts of the stove 300 are visible. Inlets 314f-j (other inlets 314a-e are not visible in Figure 5) and outlets 312a-j of the conduits 311a-j are visible in Figure 5. The inlets 314f-j are located on a side panel 391 of the stove 300. The outlets 312a-j are located on a top panel 392 of the stove 300.

Figure 6 schematically depicts a perspective view from beneath the stove 300 of Figures 2-5. Some components (e.g. walls) of the stove 300 are missing in Figure 6 such that internal parts of the stove 300 are visible. An aperture 394 is located at a base 315 of the stove 300 for allowing oxygen to enter the fuel chamber 320 from beneath the fuel chamber 320. This may provide a preferable way of oxygen entering the stove 300 when burning coal in the fuel chamber 320 rather than another solid fuel, e.g. wood.

Figure 7, consisting of Figures 7A-7C, schematically depicts three different views of a heat exchanger 310 installed on fire bricks 401, 402 of the fuel chamber 320 according to an embodiment of the invention. Figure 7A shows the heat exchanger 310 from a first perspective. Figure 7B shows the heat exchanger 310 from a second perspective that is perpendicular to the perspective of Figure 7A. Figure 70 shows the heat exchanger 310 head on. Also shown in Figure 7 is the first baffle 340, the second baffle 360 and a flue collar 332 attached to the opening 330 of the stove.

The fire bricks 401, 402 act to increase a temperature within the fuel chamber 320 during use by thermally insulating the fuel chamber 320. The first baffle 340 and the second baffle 360 act to direct heated gas into the emissions chamber 350 and towards the heat exchanger 310 whilst also removing at least some particulate matter (e.g. carbon) from the heated gases. The flow of heated gas amongst the conduits at least partly determines the extent of heat exchange between the heated gas and the ambient air. The first and second baffles 340, 360 act to direct the flow of heated gas amongst the conduits of the heat exchanger 310. The first and second baffles 340, 360 thereby promote efficient heat exchange between the heated gas and the ambient air in the conduits of the heat exchanger. The heat exchanger 310 transfers at least some heat from the heated gases to ambient air within the conduits of the heat exchanger. This heat would otherwise be lost out of the opening of the stove, thus an efficiency of the stove is improved. As previously discussed, using thicker fire bricks 401, 402 (e.g. between 40 mm and 100 mm, e.g. 50 mm) in the fuel chamber 320 raises the temperature of the fuel chamber 320 during use which improves an emissions rating of the stove 300 because less incomplete combustion takes place and fewer unwanted emissions are produced. Using thicker fire bricks 390 in a conventional stove would reduce a thermal output of the stove because more heat is kept in the fuel chamber and eventually lost to the opening, thereby reducing the conventional stove's efficiency. However, the heat exchanger 310 acts to transfer at least some of the heat that would otherwise be lost to the opening (not shown) to ambient air in the space that is to be heated by the stove 300. Thus the heat exchanger 310 enables thicker fire bricks 390 to be used in the fuel chamber 320 without negatively affecting an efficiency of the stove 300. The fire bricks 401, 402, baffles 340, 360 and heat exchanger 310 thereby provide a synergistic effect which improves an efficiency and emissions rating of a stove in which the fire bricks 401, 402, baffles 340, 360 and heat exchanger 310 are installed. The heat exchanger 310 (e.g. along with the baffles 340, 360) may be retrofitted to existing stoves to improve their efficiency and emissions rating. When this is done, thicker fire bricks 401, 402 could also be retrofitted to the existing stove.

Figure 8 schematically depicts a perspective view of a heat exchanger 310 according to an embodiment of the invention. The heat exchanger 310 is configured to be installed in a pathway of heated gas between a fuel chamber and an opening of a stove for burning solid fuel, such as the single sided stove 100 of Figure 1 or the double sided stove 300 of Figures 2-6. The heat exchanger 310 comprises a first connector plate 501, a second connector plate 502 and a conduit extending between the first and second connector plates 501, 502. In the example of Figure 8, the heat exchanger 310 comprises five conduits 311a-e. The heat exchanger 310 may comprise more than five conduits 311a-e, e.g. up to eight conduits. The heat exchanger 310 may comprise less than five conduits 311a-e, e.g. down to three conduits. Using a plurality of conduits 311a-e increases a surface area of the heat exchanger 310 which in turn advantageously improves the rate of heat exchange between the heated gas in the emissions chamber and the ambient air in the conduits 311a-e. This in turn advantageously reduces heat loss via the opening of the stove and thereby improves an efficiency of the stove in which the heat exchanger 310 is installed.

Each conduit 311a-e comprises an inlet 314a-e through the first connector plate 501 and an outlet 312a-e through the second connector plate 502. The first connector plate 501 is oriented substantially perpendicular with respect to the second connector plate 502. This advantageously enables easy installation of the heat exchanger 310 to the top panel and side panel of a stove which are substantially perpendicular to one another. The heat exchanger 310 may be retrofitted to existing stoves to improve their performance (e.g. efficiency and emissions rating) as discussed above.

A surface 600 of the conduit 311a-e may be grooved and/or curved so as to increase a surface area of the conduit 311a-e. Increasing the surface area of the conduit 311a-e advantageously improves a heat exchange rate of the heat exchanger 310. For example, one or more conduits 311a-e may have a surface 600 having a generally sinusoidal curve and/or groove, a saw-tooth shape and/or groove, a square wave shape and/or groove, etc. The surface 600 of the conduit 311a-e may have a corrugated pattern so as to increase its surface area.

A thickness of the walls of the conduit may be about 2 mm or more. The thickness of the walls of the conduit may be about 5 mm or less. For example, the thickness of the walls of the conduit may be about 3 mm. The thinner the walls of the conduit the less time it takes heat energy to exchange from the heated gases to the ambient air. Thus, a thickness of the walls of the conduit may be selected so as to provide a desired rate of heat exchange between the heated gases and the ambient air.

A length of the conduit depends on the stove to which the heat exchanger 310 is to be installed. The length of the conduit may, for example, be between about 50 mm and about 200 mm, e.g. about 100 mm. The conduit may have a cross-sectional area of between about 800 mm2 and about 1000 mm2, e.g. about 900 mm2. The length and cross-sectional area of the conduit determines the volume of air that can occupy the conduit which in turn may affect a rate of heat exchange between the heated gas and the ambient air. A length and/or cross-sectional area of the conduit may be selected so as to achieve a desired rate of heat exchange between the heat exchanger and the ambient air.

The first and second connector plates 501, 502 comprise attachment means 611-622 for removably attaching the heat exchanger 310 to the stove. In the example of Figure 8, the attachment means comprise apertures for receiving bolts. The attachment means may take other forms such as clamps.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be utilized in ways that are different to those described above. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described herein without departing from the scope of the claims set out below.

Claims

CLAIMS: 1. A stove for heating a room comprising: a fuel chamber for combusting solid fuel; an opening for conveying heated gas from the fuel chamber to a flue; and, a heat exchanger located in a pathway of the heated gas between the fuel chamber and the opening, the heat exchanger being configured to transfer heat from the heated gas to ambient air, wherein the heat exchanger comprises a conduit configured to convey the ambient air, and wherein an outlet of the conduit is higher than an inlet of the conduit.
2. The stove of claim 1, wherein at least part of the conduit is sloped between the inlet and the outlet.
3. The stove of claim 2, wherein an angle of the slope of the conduit is between about 200 and about 50°.
4. The stove of claim 3, wherein the angle of the slope of the conduit is about 30°.
5. The stove of any of claims 1 to 4, wherein a surface of the conduit is grooved or curved.
6. The stove of any preceding claim, further comprising a first baffle extending across a portion of the fuel chamber so as to form an emissions chamber between the fuel chamber and the opening, wherein the heat exchanger is located within the emissions chamber.
7. The stove of claim 6, further comprising a second baffle located in the emissions chamber and configured to direct the heated gas towards the heat exchanger.
The stove of claim 7, wherein the second baffle is generally U shaped.
9. The stove of any preceding claim, wherein the fuel chamber comprises a fire brick that is between about 40 mm and about 100 mm thick.
10. The stove of any preceding claim, wherein the heat exchanger comprises a plurality of conduits.
11. The stove of claim 10, wherein the stove is a double sided stove and wherein the heat exchanger comprises a first group of conduits located at a first side of the stove and a second group of conduits located at an opposing side of the stove.
12. The stove of any preceding claim, wherein the heat exchanger is removable.
13. A heat exchanger configured to be installed in a pathway of heated gas between a fuel chamber and an opening of a stove for burning solid fuel, the heat exchanger comprising: a first connector plate; a second connector plate; and, a plurality of conduits extending between the first and second connector plates, each conduit comprising an inlet through the first connector plate and an outlet through the second connector plate, wherein the first connector plate is substantially perpendicular to the second connector plate.
14. The heat exchanger of claim 13, wherein surfaces of the conduits are curved or grooved.
15. The heat exchanger of any of claim 13 to 14, wherein the first and second connector plates comprise attachment means for removably attaching the heat exchanger to the stove.