Heating device

Abstract

 The invention relates to a heating device for heating a reservoir of water, which heating device comprises:

• a watertight housing with an internal burning zone;
• an air inlet for supplying air to the burning zone;
• a fuel inlet for supplying fuel into the burning zone;
• a gas outlet for removing the combustion gasses out of the housing;
• a heat exchanger arranged above the burning zone comprising first channels through which the combustion gasses are transported and second channels, which are in heat exchanging contact with the first channels; and
• at least one water inlet and one water outlet, which are connected to the second channels.

Description

[0001] This invention relates to a heating device for heating a reservoir of water. In particular it relates to heating devices for outdoor tanks, hot tubs, spa units, swimming pools and the like hereafter also called "tubs and pools".

[0002] Tubs and pools that are used in gardens and remote areas can not always be heated with electricity or natural gas because these energy sources are inaccessible and technically difficult to unstall and maintain. Heating hot tubs and spa units using wood, coal and/or other fuels is a good alternative. Also because the heating is very fast. Solid fuels are available in nearly all parts of the world. Furthermore, most solid fuel burning heaters need little maintenance, which is beneficial when operating in remote areas. An effective method for heating water is direct contact of the water with a surface heated by the hot combustion gasses.

[0003] A number of such water heaters is in existence. The first of such heaters look very much like a wood stove having a sealed housing for emersion into a tank as described by US patent number 881 362, US patent number 966 147, US patent number 1 268 202 and US patent number 1 468 561.

[0004] US patent number 4 455 997 describes a L-shaped heating unit composed of a highly heat conductive metal, such as aluminum. The unit is entirely submerged in the tank of water except for air and fuel inlets and an exhaust outlet.

[0005] It is an object of the present invention to provide a low maintenance, submerged, low cost, woods, coal or any other fuel burning heating device for heating the water in tubs and pools, outdoor tanks, spa units and the like with an improved efficiency.

[0006] This object is achieved by a heating device, which comprises:

• a watertight housing with an internal burning zone;
• an air inlet for supplying air to the burning zone;
• a fuel inlet for supplying fuel into the burning zone;
• a gas outlet for removing the combustion gasses out of the housing;
• a heat exchanger arranged above the burning zone comprising first channels through which the combustion gasses are transported and second channels, which are in heat exchanging contact with the first channels; and
• at least one water inlet and one water outlet, which are connected to the second channels.

[0007] The heat exchanger provides for an improved use of the heat generated by burning the fuel, which results in a rapid heating of the water.

[0008] In a preferred embodiment a first guide tube is connected to the at least one water inlet and the open end of the first guide tube is positioned lower than the water inlet.

[0009] When water is warmed it will flow upwardly, while colder water will flow downwardly. By using a guide tube a convection flow will be generated when the water is warmed. The cold water from the bottom of the tank will be sucked up by the guide tube and supplied to the water inlet of the heating device.

[0010] In another preferred embodiment a second guide tube is connected to the at least one water outlet and the open end of the second guide tube is positioned higher than the water outlet.

[0011] As already mentioned above heated water has the tendency to flow upwardly. By providing the second guide tube a natural convection flow will be generated when the water is heated. This provides for a good circulation of the water out of the tank through the heating device providing for an improved efficiency.

[0012] According to again another embodiment of the invention, the heat exchanger comprises finns arranged in the first channels.

[0013] These finns enlarge the heat exchanging surface and thus provide for an increased efficiency.

[0014] According to another embodiment of the invention the fuel inlet comprises a lid for covering the fuel inlet, and the lid comprises a hollow handle, through which air can flow to the burning zone.

[0015] For safety purposes it would be desireable to cover the fuel inlet. However because of the burning process this lid could get very hot. By providing a hollow handle through which air can flow, the air will always cool the handle enabling a safe removal of the lid when refueling the heating device.

[0016] It is preferred when a chimney is connected to the gas outlet to arrange a perforated sleeve substantially concentric around the chimney.

[0017] As people will bath in the reservoir, it should be ensured that no one can directly touch the gas outlet, as this will be very hot. The perforated sleeve will prevent direct contact to the chimney and because of the perforations air can flow freely through the perforations and thus cool the sleeve.

[0018] Also preferably the outer, bottom surface of the housing is convex. When fuel is burned inside the housing, the walls of the housing could get very hot. When the bottom surface is totally flat, air bubbles could get caught or be formed underneath the bottom. As a result the temperatures of the bottom surface could get very high. By providing a convex outer, bottom surface the bubbles will easily flow away. The development of accessively high temperatures at the interface between the bubbles and the bottom is therefore avoided.

[0019] These and other features and advantages according to the invention are elucidated below in conjunction with the attached drawings.

[0020] Figure 1 shows in perspective view an outdoor tank with a heating device according to the invention.

[0021] Figure 2 shows in perspective view and partly cut away the heating device according to figure 1.

[0022] In figure 1 the outdoor tank 1 is shown with a heating device 2 according to the invention. The outdoor tank 1 is composed out of wooden slats 3, which are kept together by two rings 4. A fence 21 is arranged infront of the heating device 2, in order to prevent contact of users of the tank with hot parts of the heating device 2.

[0023] In figure 2, the heating device 2 is shown in more detail. The heating device 2 comprises a housing 5. At the bottom of the housing 5 wood can for example be burned. The housing 5 further comprises a fuel inlet 7 which is covered by a lid 8, having a hollow handle 9. A separate air inlet 23 is arranged in the fuel inlet 7.

[0024] In the housing 5 is a heat exchanger 10 arranged. This heat exchanger 10 has a number of horizontal tubes 11, which extend between two side walls of the housing 5. These tubes 11 form the second channels through which the water is transported. On the outside of these tubes 11 are plates 12 arranged, which enlarge the heat exchanging surface of the first channels through which the combustion gasses flow. Above the heat exchanger 10 a chimney 13 is arranged, which provides the gas outlet. Around the chimney 13 a perforated sleeve is arranged, which prevents direct contact with the chimney 13.

[0025] A first guide tube 15 is arranged over the inlets 16 of the tubes 11. This guide tube 15 is arranged such that the open end 17 of the guide tube 15 is positioned lower than the inlets 16.

[0026] At the other side a second guide tube 18 is arranged over the outlets of the tubes 11. The open end 19 of the second guide tube 18 is positioned higher than the outlets of the tubes 11.

[0027] The heater 2 is mounted to the side wall of the outdoor tank, hot tube, spa unit or the like by e.g. L-shaped brackets 22. These brackets 22 are positioned at the same side of the heater 2 as the second guide tube 18. In this way the hot water leaves the heater 2 at the side of the wall and direct contact of the hot water by persons is prevented. On the other side of the heater a fence 21 of wood or other suitable screening material could be mounted on four other L-shaped brackets 22 to prevent direct contact of the hot metal surface of the heater unit by persons in the water.

[0028] The heater device 2 is constructed of a single shell of highly corrosion resistant material that can also withstand high temperatures, such as stainless steel. The thickness of the heater wall is e.g. about 1 mm. Under normal operation conditions the temperatures are low since the heater is almost fully submerged. However, if by mistake the heater is heated without being submerged, temperatures may become very high. The heat conductivity of the metal is not important since the heating rate is fully determined by the heat transfer from the gas inside the firebox to the heater walls.

[0029] The bottom wall of the heater may be folded in a cross in order to position the center of the bottom slightly lower than the edges of the bottom of the heater. In this way gas bubbles that may be caught or formed underneath the bottom are forced away from the bottom. And the development of excessively high temperatures at the interface between the bubbles and the bottom is avoided.

[0030] The firebox fuel access and air intake may be closed with a lid 8. The lid contains two parallel rims 20 folded downward and a hollow handle 9 on top. The lid is perforated at the connection point between the lid and the hollow handle, so air can flow through the handle. During normal operation air is sucked through the hollow handle because of the low pressure inside the firebox. In this way the handle is cooled. The amount of air added to the firebox can be adjusted by sliding the lid over the air intake.

Claims

1. Heating device for heating a reservoir of water, which heating device comprises:

- a watertight housing with an internal burning zone;

- an air inlet for supplying air to the burning zone;

- a fuel inlet for supplying fuel into the burning zone;

- a gas outlet for removing the combustion gasses out of the housing;

- a heat exchanger arranged above the burning zone comprising first channels through which the combustion gasses are transported and second channels, which are in heat exchanging contact with the first channels; and

- at least one water inlet and one water outlet, which are connected to the second channels.

2. Heating device according to claim 1, wherein a first guide tube is connected to the at least one water inlet and wherein the open end of the first guide tube is positioned lower than the water inlet.

3. Heating device according to claim 1 or 2, wherein a second guide tube is connected to the at least one water outlet and wherein the open end of the second guide tube is positioned higher than the water outlet.

4. Heating device according to any of the preceding claims, wherein the heat exchanger comprises finns arranged in the first channels.

5. Heating device according to any of the preceding claims, wherein the fuel inlet comprises a lid for covering the fuel inlet, and which lid comprises a hollow handle, through which air can flow to the burning zone.

6. Heating device according to any of the preceding claims, wherein a chimney is connected to the gas outlet and wherein a perforated sleeve is arranged substantially concentric around the chimney.

7. Heating device according to any of the preceding claims, wherein the outer, bottom surface of the housing is convex.

Drawing