DESCRIPTION

[0001] It is the object of the present invention a liquid or gas fuel portable heater to heat air and introduce it into an environment to heat it.

[0002] Portable heaters are known, with:

- a combustion chamber with a substantially tubular side wall and at least one supply opening for introducing a fuel, for example, a gas or a liquid hydrocarbon, and an oxidant, for example, air, and at least one discharge opening for discharging the combustion gases,

- a housing having a tubular wall extending externally about the side wall of the combustion chamber,

- an annular space formed between the side wall of the combustion chamber and the tubular wall of the housing,

- , an electric fan received in the housing and actuatable to convey a heating air flow through the annular space,

- other electrical devices, for example, a pump for the fuel fluid, a fan for the oxidant air, a dispensing valve of the fuel fluid, an igniter, an electronic control unit, a display or lighting means etc.

[0003] The heating air flow, during the passage thereof through the annular space, exchanges heat with the side wall of the combustio chamber and cools the tubular wall of the housing. At the outlet of the annular space, the heating air flow is hot and can be directed into the environment that is desired to be heated. This may occur by tubular conduits connected to a front side of the heater, or by the simple orientation of the front side of the heater towards the environment to be heated.

[0004] The combustion chamber can be insulated from the environment to be heated. In such a case, the discharge opening of the combustion chamber is connected to a combustion gas and fume discharge conduit, which isolates them and bring them externally of the environment to be heated. Consequently, only the heating air flow, free from combustion fumes, is introduced into the environment to be heated.

[0005] In .an alternative embodiment, the hot combustion gases and fumes are also introduced in the environment to be heated, by exploiting the entire thermal energy produced by the combustion.

[0006] It follows that the heater could comprise:

[0007] A) a single electric fan positioned and actuatable to convey:

- both the heating air flow through the annular space between the combustion chamber and the housing,

- and an oxidant air flow to the inside of the combustion chamber.

In this case, the electric fan could for example convey a single flow, which is then divided into two partial flows of heating air and oxidant air.

[0008] B) a first electric fan positioned and actuatable to convey the heating air flow through the annular space between the combustion chamber and the housing, and a second electric fan positioned and actuatable to convey the oxidant air flow to the inside of the combustion chamber .

[0009] In addition to the electric fan, the known heaters need an electric power source to:

actuating the starting device that starts the combustion, by setting off a sparkle or generating an electric arc in the combustion chamber,

- actuating the electric pump to supply the fuel fluid into the combustion chamber (in the case of a diesel oil heater) ,

- actuating the dispensing valve of a gas fuel,

operating the electronic control unit, display or lighting means etc.

[0010] The absorbed electric power can reach values up to 1000 W and thus requires a connection to the power grid, which is not always available in the operation- sites of the portable heaters, for example, in mines, road and railway construction sites, refugee camps, or sites of early intervention following natural catastrophes. [0011] Attempts have been made to provide combustion portable heaters with a rechargeable electric battery which, however, is excessively heavy and is not sufficient _. to ensure an operating autonomy having a suitable duration.

[0012] Furthermore, there is the proposal to provide, on board of the portable heater, a thermoelectric converter, for example, a combustion motor with alternator or a Seebeck effect thermo-electric cell.

[0013] The combustion motor adds weight, noise, and pollution, the management of which would make the heater too complex and not enough robust for the typical applications thereof.

[0014] The use of a thermoelectric cell with Seebeck effect to provide electric power seems a more promising way, even if, to date no burners exist, which successfully implement this concept.

[0015] An obstacle still to be overcome is the difficult arrangement of the thermoelectric cell into the heater. Such thermoelectric cells, typically made of Bi-Te allows, irremediably fail upon exceeding preset threshold temperatures, e.g., 350 °C. In order to avoid the thermal damage, to date the Seebeck cells are arranged in areas of the heater that are not much exposed to the heat.

[0016] A further obstacle to the use of thermoelectric cells in the portable combustion burners is the poor electric power that can be obtained while keeping the thermal different constant. Such obtainable electric power is further decreased by the "safe" positioning of the Seebeck cell in areas that are not much exposed to the heat and by the difficulty in efficiently dissipating the thermal energy on the cold side of the Seebeck cell.

[0017] Therefore, to ensure the provision of the electric power required by the heater, it would be necessary to install in the heater a high amount of thermoelectric cells. with large dimensions, thus increasing the complexity and the manufacturing cost.

[0018] Therefore, the object of the present invention is to provide a portable fuel heater of air, which is provided with an unit with at least one Seebeck-effect thermoelectric cell, and having such characteristics as to at least partially obviate the drawbacks mentioned with reference to the prior art.

[0019] A particular object of the invention is to provide a portable fuel heater of air, provided with a Seebeck- effect thermoelectric cell unit, and having such characteristics as to ensure an improved cooling of the thermoelectric cell unit.

[0020] A further particular object of the invention is to propose a heater of the specified type, in which the thermoelectric cell is protected against a harmful overheating .

[0021] A further particular object of the invention is to propose a heater of the specified type, having such characteristics as to increase the electric power that can be generated, while keeping the amount and dimensions of the installed thermoelectric cells constant.

[0022] A further particular object of the invention is to propose a heater of the specified type, which is electrically self-supplied and independent from the power grid, and which has a reduced number of thermoelectric cells .

[0023] These and other objects are achieved by a liquid or gas fuel portable heater to heat air in accordance with claim 1.

[0024] Advantageous embodiments are the object of the dependent claims.

[0025] In accordance with an aspect of the invention, a fuel portable heater comprises:

- a combustion chamber with a substantially tubular side wall defining a combustion space and at least one supply opening for introducing a fuel and an oxidant, and at least one discharge opening for discharging the combustion gases,

- a housing having a tubular wall extending externally about the side wall of the combustion chamber,

- an annular space formed between the side wall and the tubular wall,

an electric fan received in the or connected in communication with the housing and actuatable to convey a heating air flow through the annular space,

- a Seebeck effect thermoelectric converter having a hot side and a cold side, said thermoelectric converter being connected to the side wall of the combustion chamber with the hot side in a thermal exchange relationship with the combustion space and the cold side in a thermal exchange relationship with the annular space,

- guide surfaces formed in the annular space so as to change the flow section of the annular space in a circumferential direction about the side wall and to deviate at least one part of the heating air flow from at least one first circumferential area of the annular space towards at least one second circumferential area of the annular space,

wherein the thermoelectric converter is located at the second circumferential area.

[0026] In this manner it is possible, while keeping the dimensions of the combustion chamber and the tubular wall of the housing constant, concentrating a higher air volume for the thermal exchange in the second circumferential area of the annular space and exploiting this higher volume to more efficiently cool the cold side of the Seebeck cell. The Seebeck cell, in turn, transports an additional amount of heat from the combustion chamber exactly into the second circumferential area of the annular space, where the direct thermal exchange between the side wall and the heating air and the indirect one are concentrated: combustion space - thermoelectric converter - heating air. In this manner, it is possible to maintain an efficient overall thermal exchange, avoiding harmful overheatings of the Seebeck cell, and putting the Seebeck cell in a very high thermal potential (delta) in order to be able to generate a sufficient electric power for the operation of the heater.

[0027] In accordance with aspects of the invention, the guide surfaces can be stationary and can be formed by one or more deflection inserts, which are arranged in the annular space between the side wall and the tubular wall or, alternatively, the guide surfaces can be formed directly by the side and tubular walls.

[0028] To this aim, the side and tubular walls can be coaxial, while having a different cross-section shape so as to implement in the circumferential direction of the annular space a change of the free radial width between the side wall and the tubular wall.

[0029] Alternatively, the side and tubular walls can be arranged in an eccentric manner the one to the other and have a similar cross-sectional shape, for example, circular, or different, so as to implement in the circumferential direction of the annular space a change of the free radial width between the side wall and the tubular wall.

[0030] In order to better understand the invention and appreciate the advantages thereof, some exemplary, non- limiting embodiments will be described herein below, with reference to the appended figures, in which:

- Figs. 1 and 2 are schematized views in cross-section and in longitudinal section of a fuel portable heater according to a first embodiment of the invention;

- Fig. 3 is a schematized view in longitudinal section of a fuel portable heater according to a second embodiment;

- Figs. 4, 5 and 6 are schematized views in cross-section of a fuel portable heater according to a third, fourth, and fifth embodiment;

- Figs. 7 and 8 are schematized views in cross-section and in longitudinal section of a fuel portable heater according to a sixth embodiment;

- Figs. 9 and 10 show a fuel portable heater according to a preferred embodiment in a perspective view and in a rear view;

- Figs. 11 and 12 show the heater of Fig. 9 with the tubular wall of the housing removed;

- Figs. 13 and 14 show, in a front and side view, a combustion chamber with a thermoelectric converter and two deflection inserts of a heater according to an embodiment ;

- Fig. 15 is a front view of a thermal radiator of the cold side of a thermoelectric converter for a heater according to an embodiment of the invention.

[0031 ] With reference to the figures, a liquid or gas fuel portable heater to heat air, is generally indicated with the reference 1.

[0032] The heater 1 comprises a combustion chamber 2 with a substantially tubular side wall 3 defining a combustion space 4 and at least one supply opening 5 for introducing a fuel and an oxidant, and at least one discharge opening 6 for discharging the combustion gases.

[0033] The heater 1 further comprises a housing 7 having a tubular wall 8 extending externally about the side wall 3 of the combustion chamber 2 so as to form an annular space 9 between the side wall 3 and the tubular wall 8.

[0034] An electric fan 10 is received in the or connected in communication with the housing 7 and actuatable to convey a heating air flow 11 through the annular space 9. [0035] A Seebeck effect thermoelectric converter 12 (Seebeck cell) is connected to the side wall 3 of the combustion chamber 2 with a hot side 13 thereof in a thermal exchange relationship with the combustion space 4 and with a cold side 14 thereof in a thermal exchange relationship with the annular space 9.

[0036] According to an aspect of the invention, guide surfaces 15 are formed in the annular space 9 so as to change a flow section of the annular space 9 in a circumferential direction about the side wall 3 and to deviate at least one part of the heating air flow 11 from at least one first circumferential area 16 of the annular space 9 towards at least one second circumferential area 17 of the annular space 9, and the thermoelectric converter 12 is located at the second circumferential area 17.

[0037] In this manner it is possible, while keeping the dimensions of the combustion chamber 2 and of the tubular wall _. 8 of the housing 7 constant, concentrating a higher volume of heating air 11 in the second circumferential area 17 of the annular space 9 and exploiting this higher volume of heating air 11 for the thermal exchange and to more efficiently cool the cold side 14 of the Seebeck cell 12. The Seebeck cell 12, in turn, transports an additional amount of heat from the combustion chamber 2 in the second circumferential area 17 of the annular space 9 where the direct thermal exchange between the side wall 3 and the heating air 11 and the indirect one between the combustion space 4, the thermoelectric converter 12 and the heating air 11 are concentrated; In this manner, it is possible keep an efficient overall thermal exchange, avoiding harmful overheatings of the Seebeck cell 12 and putting the Seebeck cell 12 in a very high thermal potential in order to be able to generate an electric power sufficient for the operation of the heater 1.

[0038] In accordance with an embodiment, the guide surfaces 15 can be stationary and they can be formed by one or more deflection inserts 18 arranged in the annular space 9 between the side wall 3 and the tubular wall 8. The deflection inserts 18 can be connected, e.g., riveted, welded or screwed, on an outer surface 19 of the side wall 3 and project therefrom in the annular space 9. The deflection insert or inserts 18 can form two deflection walls 22 that are opposite and inclined with respect to a longitudinal axis of the side wall 3 so as to form in the annular space 9 a funnel, the angular or circumferential width of which narrows in the direction of the heating air flow 11 from a rear side 20 of the annular space 9 up to the proximity of an outer radiator 21 of the cold side [0039] Two guide walls 23 opposite and substantially parallel to the longitudinal axis of the side wall 3 and defining the above-mentioned second circumferential area 17 in which the thermoelectric converter 12 is arranged can be connected to the funnel-shaped deflection walls 22.

[0040] Alternatively or in addition, the guide surfaces.15 can be formed directly by the side 3 and tubular 8 walls .

[0041] According to an embodiment, the side 3 and tubular 8 walls can be coaxial, while having a different cross- section shape, so as to implement in the circumferential direction of the annular space 9 a change of the free radial width between the side wall 3 and the tubular wall 8 (with respect to the longitudinal axis of the side wall 3) . In this case, the second zone circumferential area or areas 17. receiving _. the .thermoelectric converter 12 have a radial width that is larger and the first circumferential area or areas 16 free from a thermoelectric converter 12 have a reduced radial width.

[0042] Similarly, the side 3 and tubular 8 walls can be arranged in an eccentric, manner and have different cross- sectional shapes, so as to implement in the circumferential direction of the annular space 9 a change of the free radial width _. between the side wall 3 and the tubular wall 8 (with respect to the longitudinal axis of the side wall 3).

[0043] By way of non-limiting example, the cross-sectional shape of the side wall 3 can be circular or lobated (for example, bi-lobated, tri-lobated, rounded polygonal) and the cross-sectional shape of the tubular wall 8 can be lobated (for example, bi-lobated, tri-lobated, rounded polygonal) or circular, so as to implement in the circumferential direction of the annular space 9 a change of the free radial width between the side wall 3 and the tubular wall 8 (with respect to the longitudinal axis of the side wall 3) in order to be able exactly to arrange one or more thermoelectric converters 12 in the second circumferential areas 17 of radial width that is larger (figures 4, 5, 6) .

[0044] In accordance with a further embodiment (Fig. 7), the side 3 and tubular 8 walls can be arranged in an eccentric manner the one to the other and have a similar cross-sectional shape, for example, circular, or different, so as to implement in the circumferential direction of the annular space 9 a change of the free radial width between the side wall 3 and the tubular wall 8.

[0045] In all the embodiments hereto described, one or more deflection inserts 18 can be provided, for further directing the flow of the heating air through the outer radiator 21 of the thermoelectric converter 12.

[0046] According to a further embodiment, the side 3 and tubular 8 walls can have a constant cross-sectional shape, for example, a circular cylindrical tubular shape or a rounded polygonal prismatic shape, or a bi-lobated or tri-lobated prismatic shape.

[0047] Alternatively, the side 3 and tubular 8 walls can have a variable cross-sectional shape, for example, frusto-conical, which widens in the direction of the heating air flow 11.

[0048] In a preferred embodiment (Figs. 7, 8) the side 3 and tubular 8 walls are both circular cylindrical and arranged in an eccentric manner, in which, in the first circumferential area 16 of the annular space 9 a deflection insert 18 is arranged, which guides the heating air flow towards the second circumferential area 17 of a larger radial width. As it can be noticed in the Figs. 11 - 14, the deflection insert 18 forms sickle- shaped deflection walls 22, the height of which increases gradually from the rear side 20 of the annular space 9 towards the thermoelectric converter 12 to follow the increase of the radial width of the annular space 9 from the first circumferential area 16 to the second circumferential area 17. [0049] According to embodiments, the deflection insert 18 or the deflection wall 22 can extend radially from the side wall 3 up to the tubular wall 8 and substantially completely separate the first and second circumferential areas 16, 17 of the annular space 9. However, the deflection insert 18 or the deflection wall 22 can form through openings and/or slits 24 for a more targeted distribution of the partial flows of the heating air 11 between the first and second circumferential areas 16, 17.

[0050] In a preferred embodiment, the thermoelectric converter 12 is connected to an upper portion of the side wall 3, once the heater 1 is in the operative position. This allows better exploitation of the available spaces, since the reservoir and the electronic control are typically arranged in an area below the combustion chamber 3. Furthermore, the thermal convection effect from the bottom upwardly further increases the thermal exchange efficiency and the thermal potential available for the generation of electric power.

[0051 ] According to an embodiment, the thermoelectric converter 12 can have an overall length that is larger than a fifth (for relatively long combustion chambers 2, e.g., about 80cm ... llOcmm) of the length of the side wall 3 of the combustion chamber 2, preferably larger than 45% of the length of the side wall 3, still more preferably between 45% and 5-5% of the length of the side wall 3. Alternatively, the thermoelectric converter 12 can extend substantially along the entire length of the side wall 3.

[0052] Furthermore, the thermoelectric converter 12 is preferably positioned in a front position 25 of the annular space 9 facing away from a rear side 20 thereof, where it enters the heating air flow 11. However, the deflection walls 22 extend also in a front area of the annular space 9 to receive and direct the heating air flow 11 already when it enters the annular space 9.

The outer radiator 21 can comprise a plurality of fins 26 extending from a support plate 27 connected to the cold side of the Seebeck cell. The fins 26 extend in the axial direction and in the radial direction and can have a corrugated cross-sectional shape in a sectional plane orthogonal to the longitudinal axis of the side wall 3. The fins 26 can be mutually spaced apart in the circumferential direction with a pitch larger than 4 mm, preferably 6 mm to 10 mm (the indicated distance refers to the radially outer ends of the fins 26) . The support plate 27 has a curvature similar to the curvature of the adjacent portion of side wall 3 and has a radial thickness that is larger in a central area of connection with the Seebeck cell and that gradually decreases moving away from the central connection area. The outer radiator 21 can be made of aluminium.

[0053] The thermoelectric converter 12 can comprise an inner radiator 28 coupled to the hot side of the Seebeck cell and projecting from the side wall 3 into the combustion space 4. The inner radiator 28 can also comprise a plurality of fins 29 extending in the- radial direction and in the longitudinal direction of the combustion space 4. Advantageously the fins 29 project radially outwardly and inwardly from a support ring or tube 30 connected to the hot side of the Seebeck cell. The support ring or tube 30 has a radial thickness that is larger in the proximity of a connection area thereof with the hot side of the Seebeck cell and that gradually decreases up to a point diametrically opposite the connection area. The inner radiator 28 can be made of aluminium.

[0054] According to an embodiment, the thermoelectric converter 12 is mechanically connected to, but thermally insulated from the side wall 3. The side wall 3 can comprise an opening that is slightly larger than the dimensions of the Seebeck cell, which is located in the opening of the side wall 3 and sandwiched, together with an edge of the side wall 3, between the inner radiator 28, and the outer radiator 21, so that the thermoelectric converter 12 surrounds the side wall 3 sheet. In order to avoid overheatings, the outer radiator 21 (cold side) can be isolated, for example, spaced apart from the side wall 3 by spacers 39, e.g., feet obtained directly from the extrudate of the cold outer radiator 21, or spacers made of a thermoinsulating and thermoresistant material that is different from the material of the outer radiator 21.

[0055] As it is known, the heater 1 can comprise a fuel supply conduit 31 connecting the supply opening 5 to a liquid fuel reservoir 38 (preferably, on board of the portable heater 1) or a gas fuel source, e.g., a cylinder on board of the heater 1, or, preferably, to an external gas conduit.

[0056] A rear wall 32 of the combustion chamber 2 can form one or more oxidant openings 33 for the supply of oxidant air into the combustion space 4.

[0057] Therefore, the electric fan 10 can be positioned and actuatable to convey:

- both the heating air flow 11 through the annular space 9,

- and an oxidant air flow 34 in the combustion chamber.

[0058] In this case, the electric fan 10 is actuatable to convey a single flow that is subsequently divided into two partial flows of heating air 11 and oxidant air 34.

[0059] Alternatively, in addition to the electric fan 10 to convey the heating air flow 11 through the annular space 9, a second electric fan (not illustrated) can be provided for, which is positioned and actuatable to convey the oxidant air flow 34 in the combustion chamber 2.

[0060] One or more of the electric devices of the heater 1, preferably all the electric devices of the heater 1, such as, for example:

[0061] - the first electric fan 11 and/or an optional second electric fan,

[0062] - a starting device 35 arranged in the combustion chamber 2 to start the combustion,

[0063] - an optional electric pump 36 to supply the fuel fluid into the combustion chamber 2 (in the case of a diesel oil heater ) ,

[0064] - an electronvalve 37 to control the supply of a fuel fluid into the combustion chamber 2 (in the case of a gas and/or diesel oil heater) ,

[0065] - an electronic control unit 38 that drives the several functions of the heater 1,

can be connected, for an electric supply thereof, for example by the interposition of a battery unit 40, to said one or more Seebeck effect thermoelectric converters 12.

[0066] From the description hereto provided, those skilled in the art will be able to appreciate how the portable heater according to the invention reaches the objects of the invention.

[0067] It shall be apparent that, to the fuel portable heater according to the present invention, those skilled in the art, with the aim of meeting contingent, specific needs, will be able to make further modifications and variation, all anyhow falling within the protection scope of the invention, as defined by the following claims.