Sauna stove

Abstract

FIELD: thermal power engineering.SUBSTANCE: invention relates to heat generating devices on solid or gaseous fuel, used for heating air and generating steam in premises of public and commercial baths or saunas designed for a relatively large number of users. The sauna stove comprises a metal casing finned on the outside, consisting of two parts. The lower part forms a fireclay-lined firebox with an open top, having a loading door on the front wall, a grate system with ash boxes. In the upper removable part of the casing between the front and rear walls, two heaters are installed with systems for supplying water to the heat-accumulating material and with doors located on the rear wall for loading heat-accumulating materials. Between the heaters and the side walls of the upper part of the casing, gaps are formed for the passage of flue gases to the chimney pipe, which is installed on the upper wall of the upper part of the casing. Inside the heaters, ribs are installed along the walls, dividing the heaters into several sections. Between the heaters at the level of their bottom, a horizontal partition is installed with gaps relative to the front and rear walls of the upper part of the casing. The chimney pipe is made elongated, and its inlet opening is placed above the horizontal partition at a distance equal to half the inner diameter of the chimney pipe. The width of the gaps between the horizontal partition and the walls of the upper part of the casing is 0.04D, where D is the diameter of the chimney.EFFECT: increase in energy efficiency, stove power and its efficiency is achieved by increasing heat removal from flue gases and lowering their temperature in the chimney, as well as reducing fuel consumption and increasing fire safety.4 cl, 1 dwg

Description

[0001] The invention relates to thermal power engineering, namely to heat-generating devices using solid or gaseous fuel, used for heating air and producing steam in public and commercial baths or saunas designed for a relatively large number of users.

[0002] Bath stoves are a unique type of heating device, with a centuries-long history of development. To date, many different designs have been created, typically specialized for specific applications. However, a significant drawback of existing sauna stove designs, whether operating on solid or gaseous fuel, is their comparatively low energy efficiency. This is due to the fact that a sauna stove simultaneously performs two tasks: heating the air for the steam room and generating steam. Ideally, this steam should be high-temperature (500-600°C) and finely dispersed. Producing steam with such parameters in large volumes is the most challenging task, as it requires heating and maintaining a high temperature in a large volume of heat-storing elements with low thermal conductivity.Therefore, in sauna stoves, this is achieved by increasing the flue gas temperature, which results in a decrease in stove efficiency (often by 30-40%) due to increased heat loss through the chimney. Furthermore, fuel consumption increases significantly. While this may be acceptable for individual stoves, for commercial stoves, such low energy efficiency significantly impacts the cost of operating the stove.

[0003] A sauna stove (RU 2740971, class F24B 1 / 02, F24B 5 / 02, F24B 7 / 00, F24B 13 / 00, 2021) is known, including a body, a firebox, an ash pan, a grate, a closed heater, a chimney pipe, a heater cover, and a protective casing. The side wall of the body is provided with hooks for attaching a heat exchanger. The closed heater has a side heater channel with a heater door. The closed heater is installed at a distance from the walls of the stove body, allowing flue gases to pass along the contour of the entire outer surface and a chimney in the upper wall of the stove body. Convection channels are on the rear and side walls of the stove, and a protective screen in the form of metal plates, panels, or fireclay stone is located along the perimeter of the stove body. The space between the stove and the screen is filled with heat-insulating material (stones).In the case of making the screen in the form of a casing made of natural stone along the contour of the furnace body, it is made with an open top and a side for laying out the stone, the side lower plates on the right and left are made U-shaped, it has side plates on the right, left and in front along the contour of the firebox channel and upper plates on the top and in front.

[0004] The well-known sauna stove has a complex design, is difficult to maintain, and has low energy efficiency. Furthermore, the stove's design does not allow for a significant increase in power for use in larger spaces.

[0005] A sauna stove is known (RU 2651878, class F24B 5 / 00, 2018), comprising a housing with a casing, with three modules located inside: a loading firebox module, a firebox module, and a dual-flow heater module. The loading firebox module is designed as a box, on the front part of which a door and a handle for opening it are installed. At the rear part there is an ash pan, installed so as to be able to move both along the loading firebox module and along the firebox module. The firebox module is designed as a box with at least one opening in the upper part for the passage of flue gases into a pipe, with a grate located in the lower part. The third module is designed as a box with a dual-flow channel organized inside for the passage of flue gases into the chimney. The lower section of the dual-flow heater module, located above the calibrated openings, is equipped with flame baffles. The modules are secured together using a profile joint.

[0006] The disadvantages of the known design are low energy efficiency, due to the upward flow of flue gases from the firebox around the heater into the chimney, as well as the impossibility of increasing the furnace power due to the fact that the design elements are not designed for high specific heat loads.

[0007] A high-power sauna stove is known, selected as a prototype (RU 2809370, cl. F24B 7 / 00, 2023), containing a ribbed metal body on the outside, consisting of two parts, the lower of which forms a firebox lined with fireclay material with an open top, having a loading door on the front wall, a grate system with ash boxes, and in the upper part of the body between the front and rear walls, two heaters are installed with systems for supplying water to the heat-accumulating material and with doors located on the rear wall for loading heat-accumulating materials, while between the heaters and between the heaters and the side walls of the upper part of the body, gaps are formed for the passage of flue gases to the chimney pipe, which is installed on the upper wall of the upper part of the body, and inside the heaters, ribs are installed along the walls, dividing the heaters into several sections.

[0008] A drawback of the known design is its low energy efficiency. This is due to the short contact time between flue gases and the heat-exchange surfaces of the heaters and the stove body. This necessitates maintaining a high flue gas temperature and entering a near-critical operating mode to quickly restore the temperature of the heat-accumulating material in the heaters when steam is generated. This significantly reduces the stove's efficiency, shortens its service life, and increases fuel consumption.

[0009] The technical result consists in increasing the energy efficiency, power of the furnace and its efficiency, due to the increase in heat removal from the flue gases and the decrease in their temperature in the chimney, as well as the reduction in fuel consumption and the improvement of fire safety.

[0010] The technical result is achieved in that a bath stove containing a ribbed metal body on the outside, consisting of two parts, the lower of which forms a firebox lined with fireclay material with an open top, having a loading door on the front wall, a grate system with ash boxes, and in the upper removable part of the body between the front and rear walls, two heaters are installed with systems for supplying water to the heat-accumulating material and with doors for loading heat-accumulating materials, located on the rear wall, while between the heaters and the side walls of the upper part of the body, gaps are formed for the passage of flue gases to the chimney pipe, which is installed on the upper wall of the upper part of the body, and inside the heaters along the walls, ribs are installed, dividing the heaters into several sections, between the heaters, at the level of their bottom, a horizontal partition is installed with gaps relative to the front and rear walls of the upper part of the body,the chimney pipe is made elongated, and its inlet is located above the horizontal partition at a distance equal to half the internal diameter of the chimney pipe, while the width of the gaps between the horizontal partition and the walls of the upper part of the body is 0.04D, where D is the diameter of the chimney.

[0011] The essence of the invention is explained in Fig. 1, which shows a simplified view of the furnace in cross section and indicates: 1 - body, 2 - the upper part of the body 1,3 - the lower part of the body 1,4 - the upper cover of the upper part 2 of the body, 5 - heaters (containers for placing heat-accumulating materials), 6 - heater ribs, 7 - the bottom of the heaters, 8 - a chimney pipe, 9 - a horizontal partition, 10 - gas channels between the heaters and the side walls of the upper part 2 of the body, 11 - a loading door, 12 - grates, 13 - ash boxes, 14 - lining of the side walls and the bottom of the lower part 3 of the body, 15 - connecting ribs.

[0012] Furnace body 1 and its components, depending on the furnace capacity, are made of steel with the required wall thickness and heat resistance, ensuring the required service life of the furnace. Fins (not shown in the figure) are welded to the outside of furnace body 1 to increase the heat-exchange surface of the furnace. To increase the emissivity, furnace body 1 is painted with black heat-resistant organosilicon paint. Furnace body 1 is detachable, consisting of upper 2 and lower 3 parts. This significantly improves the manufacturability of the furnace, reduces its production time, and improves maintainability. To expand the functionality of the furnace, furnace body 1 can be equipped with an internal or external water heating heat exchanger. Brick lining can be installed around furnace body 1 with an air gap. To increase the service life of the furnace, the side walls and the bottom of the lower part 3 of the furnace body are lined with fireclay bricks or fireclay slabs.Instead of the loading door 11, designed for loading solid fuel (firewood, briquettes, pellets), a gas or pellet burner can be installed. Grate bars 12 are installed on the bottom of the firebox 3 of the furnace body 1, and ash drawers 13 are located beneath them. Stone heaters 5 serve to accommodate heat-accumulating materials, which are rounded volcanic rocks 5-10 cm in size, such as basalt and peridotite. To increase the heat-exchange surface and improve the rigidity of the structure, ribs 6 are installed inside the stone heaters 5 on the side walls and bottom. Thus, the stone heaters 5 are divided into several sections. Due to the high thermal loads acting on the bottom 7 of the stone heaters 5, to increase their service life, the bottom 7 of the stone heaters 5 is made of metal that is several times thicker. The bottom 7 of the stone heaters 5 can also be coated on the outside with fireclay material. The 5 heaters on the back of the stove are equipped with tunnels with doors (not shown in the figure).Through these doors and water supply systems, it is distributed evenly onto the heat-accumulating material in all sections of the heaters 5 in order to generate steam for the steam room. To prevent thermal deformation of the housing 1 under high temperature conditions, the heaters 5 are connected by stiffening ribs (crossbars) in the gas ducts 10 to the side and upper 4 walls of the upper part 2 of the heater housing 1. The horizontal partition 9 serves to prevent flue gases formed during fuel combustion from entering directly into the chimney pipe 8. The partition 9 is installed at the level of the bottom 7 of the heaters 5 with gaps between the front and rear walls of part 2 of the heater housing 1. The width of the gaps (not shown in the figure) is 0.04D, where D is the chimney diameter. The partition 9 can be made of metal with a thickness not less than the thickness of the metal of the bottom 7 of the heaters 5 or of fireclay material (slabs or bricks).The inlet opening of the chimney pipe 8 is installed above the partition 9 at a distance equal to half the internal diameter of the chimney pipe 8. To increase the rigidity of the structure, the chimney pipe 8 is connected by jumpers to the side walls of the heaters 5. The connecting ribs 15 serve to connect, after manufacture or repair, through a sealing heat-resistant gasket, the two halves 2 and 3 of the body 1. For this purpose, mating holes are made in them, through which they are connected using bolts.

[0013] The sauna stove operates as follows. When the stove is cold, flue gases pass not only through the gas channels 10 but also directly to the inlet of the chimney pipe 8 through the gaps between the partition 9 and the front and rear walls of the upper part 2 of the stove body 1. As the volume of flue gases increases and the chimney heats up, its draft and the gas flow of hot flue gases through the gas channels 10 increase, getting under the upper cover 4, circulate under it for some time, and as they cool, they descend between the heaters to the entrance of the chimney pipe 8. Due to the fact that the gas molecules of the hot flue gases randomly give up their energy upon contact with the enclosing surfaces and upon the emission of thermal radiation quanta, then that part of the gas molecules that gave up their energy is displaced by molecules with higher energy and descends and, under the action of the vacuum created in the chimney pipe 8, enters the chimney and then into the atmosphere.This organization of flue gas flow increases the contact time of hot flue gases with the heat-exchange surfaces, thereby transferring additional thermal energy to them. This increases the temperature of the upper part 2 of the stove body 1 and the heaters 5, and consequently, the stove's thermal output. Because the stove ensures more complete extraction of thermal energy from the flue gases, their temperature in the chimney is significantly reduced. Heat loss with the flue gases is reduced, thereby increasing stove efficiency and reducing fuel consumption. The reduced flue gas temperature reduces the temperature of the chimney itself, thereby improving stove fire safety. Steam is generated in the stove by pouring the required volume of water into the water supply system, which evenly distributes it to the heated stones in all sections of heater 5.

[0014] Thus, the proposed sauna stove design, compared to the prototype and other similar models, improves energy efficiency and power by increasing the contact time of hot flue gases with the stove's heat-exchange surfaces. Reducing heat loss via flue gases increases efficiency and improves fire safety. This also reduces fuel consumption, thereby improving the stove's performance. Operation of a prototype stove manufactured using the proposed design at a commercial sauna complex for several years fully confirmed the stove's claimed performance. Furthermore, the additional thermal power generated by this stove virtually eliminated operation in near-critical conditions, significantly extending the stove's service life.

[0015] The development level, after an instrumental assessment of the main parameters of the stove and conducting full-scale tests of the stove under real operating conditions, is in the stage of organizing small-scale production of a range of sauna stoves with different thermal power.

Claims

1. A sauna stove comprising a ribbed metal body on the outside, consisting of two parts, the lower of which forms a firebox lined with fireclay material with an open top, having a loading door on the front wall, a grate system with ash boxes, and in the upper removable part of the body between the front and rear walls, two heaters are installed with systems for supplying water to the heat-accumulating material and with doors located on the rear wall for loading heat-accumulating materials, while between the heaters and the side walls of the upper part of the body, gaps are formed for the passage of flue gases to the chimney pipe, which is installed on the upper wall of the upper part of the body, and inside the heaters, ribs are installed along the walls, dividing the heaters into several sections, characterized in that between the heaters at the level of their bottoms, a horizontal partition is installed with gaps relative to the front and rear walls of the upper part of the body, the chimney pipe is made elongated,and its inlet is located above the horizontal partition at a distance equal to half the internal diameter of the chimney pipe, while the width of the gaps between the horizontal partition and the walls of the upper part of the body is 0.04D, where D is the diameter of the chimney.

2. A bath stove according to paragraph 1, characterized in that the horizontal partition is made of metal.

3. A sauna stove according to paragraph 1, characterized in that the horizontal partition is made of metal with a thickness no less than the thickness of the metal of the bottom of the heaters.

4. A bath stove according to paragraph 1, characterized in that the horizontal partition is made of fireclay slabs or bricks.

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