EP2784409B1

EP2784409B1 - A portable fuel heater to heat air and a method for heating air through said heater

Info

Publication number: EP2784409B1
Application number: EP13161801.9A
Authority: EP
Inventors: Enzo Giaretta; Stefano Verani; Davide Galletti; Ugo Romagnani; Sergio Lorenzi
Original assignee: MCS Italy SpA
Current assignee: MCS Italy SpA
Priority date: 2013-03-28
Filing date: 2013-03-28
Publication date: 2017-01-18
Anticipated expiration: 2033-03-28
Also published as: EP2784409A1

Description

It is the object of the present invention a portable liquid or gaseous fuel heater to heat air and input it into an environment in order to heat it.
Portable heater devices are known, which use the heat produced by the combustion of a fuel, for example, a gas or a liquid hydrocarbon, in the presence of an oxidizing agent, for example, ambient air, and one or more fans actuated by an electric motor, to generate an air flow that first skims heated surfaces of the combustion chamber, then reaches the environment to be heated.
Sometimes, a forced air flow is actuated in the combustion chamber so as to obtain a suitable mixing ratio between fuel and air, thus optimizing the combustion and reducing or eliminating the CO formation, which is hazardous to the health.
In fact, there are two main types of heaters: a first type of heater inputs the combustion gaseous products into the environment to be heated together with a forced air flow passing through the combustion chamber with an excess of oxygen, so as to almost completely eliminate the CO produced. This need is met by mounting a fan at an end of the chamber to push the air through the combustion chamber towards the opposite end of the same combustion chamber, to then reach the environment. In this way the heated air contains the combustion products, thus it is very important to generate an air flow with a suitable flow rate.
Furthermore, there is a second type of heaters that have the combustion chamber insulated from the environment to be heated, and connected instead to a gas discharge duct leading to the outside of the environment to be heated. In this case also, there is at least one fan intended to generate a forced air flow in the combustion chamber, which is however conveyed externally to the environment to be heated.
In both types of heaters, there may be an air moving system, for example a fan, which pushes fresh air to externally skim the combustion chamber, to be subsequently inputted in the environment to be heated without discharge gases.
In both these cases, it is known to use one or more fans actuated by one or more electric motors, thus requiring an external power supply.
These known heaters comprise a starter device that primes the combustion by sparking off a spark or generating an electric arc in the combustion chamber during the supply of the gaseous fuel or the vaporized liquid fuel.
Generally, this spark or electric arc is generated via the electric power withdrawn from the electric grid.
The known portable heaters such as those described above, require, throughout their standard operation, an electric power supply to supply at least the fan for the forced flow, the formation of the starting spark, which can be constant or repeated at preset time intervals for safety reasons, and optionally for the movement and injection of the fuel (such as, for example, diesel oil), for an electronic control or to serve other services such as probes, sensors, safety valves, etc. The electric power required can easily reach higher values, even up to 1000 W power and more, according to the air flow rate required for operation.
The known portable devices sometimes comprise a tank for holding a liquid fuel or a cylinder for holding a gaseous fuel on board, so as to be independent from the point of view of the fuel supply.
However, such known devices, particularly in the case that the combustion has to take place in a controlled manner with an oxygen oversupply, cannot perform their function in a manner independent from a power supply from an external grid.
Attempts have been made to overcome this drawback, but without success. In fact, a portable gas environmental heater is known, having a tubular combustion chamber and a fan actuated by an electric motor, to generate a forced air flow in the combustion chamber, which tries to solve such a problem by providing the device with a rechargeable electric battery to internally supply the fan and other electric and electronic devices on board.
Although high capacity batteries are known, they are absolutely not sufficient to ensure an operative life of a suitable duration, since the powers required are high, and such a device is not capable of autonomously operating for more than a few hours. When the battery is empty, it is essential to recharge it, otherwise the device cannot be used anymore.
Such a device is absolutely useless in applications for which one has to stay far from electric power sources for a prolonged period. Moreover, such a device does not ensure any safety in the most difficult environmental situations.
Another drawback of this known device is given by the fact that, when trying to prolong the operating time, electrical components have to be used with a low electric power consumption, thus having reduced overall dimensions of the heater, thus reduced air flow rates.
Therefore, the known devices that use only a battery cannot be implemented for high hot air flow rates to heat large environments.
Other attempts, aimed to make a fuel air heater autonomous, are a large sized heater to which a generator is associated, having an internal combustion engine separated from the heater. Such a solution is capable of heating even very large environments, but it requires a very bulky and heavy structure, which is certainly not portable, but which can optionally be transported while being towed by a motorized transport means. Therefore, such a device can be used only in particular cases.
Another drawback of the associated generator is given by the combustion gases that, being it aimed to generate a motive force, does not allow optimizing the quality of the discharge gases via an excess of oxygen. Furthermore, such a solution turns out to be undesired due to the high noise it generates.
The patent US 5,509,604 describes a chargeable fan heater capable of operation without external power supply, having a burner for burning fuel to produce hot combustion gas, a sterling engine having a shaft and for producing works by the thermal energy from the hot combustion gas, a fan for discharging the hot combustion gas to spaces to be heated, a combined motor-generator connected to the sterling engine to generate electricity, a battery for supplying power to the combined motor-generator and being charged by the electricity generated in the combined motor-generator, and a control box.
The patent application US 2013/0008423 A1 describes a forced-air heater having a self-contained on-board electric-power supply, a fuel tank, a support, a housing, a combustion chamber, and a motorized fan to draw in ambient air through an air intake and force the air into the combustion chamber.
The object of the present invention is to devise and provide a portable air heater that allows meeting the above-mentioned needs and at least partially obviating the drawbacks set forth above with reference to the prior art.
In particular, the task of the present invention is to provide a liquid or gaseous fuel air heater capable of operating continuously while generating a high forced air flow in the combustion chamber without the need for any electric power source, whether an external one, or built-up on board.
Another object of the present invention is to provide a portable liquid or gaseous fuel air heater that further has compact dimensions and that is easily transportable.
Such an object and tasks are achieved by a portable liquid or gaseous fuel heater to heat air in accordance with claim 1. According to another aspect of the present invention, the above mentioned objects and advantages are met by a method to heat an environment through such a portable liquid or gaseous fuel heater.
Further objects, solutions, and advantages are present in the embodiments described herein below and claimed in the dependent claims appended herein below.
Further features and advantages of the present invention will be apparent from the description set forth below of preferred implementation examples, given by way of indicative, non-limiting example, with reference to the appended Figures, in which:

Fig 1 illustrates a schematic view in longitudinal section of a portable gas heater according to the invention, having an energy conversion cell;
Fig. 2 illustrates an axonometric front view of the heater in Fig. 1;
Fig. 3 illustrates a schematic view in longitudinal section of an implementation of the heater in Fig. 1, in which five conversion cells are represented;
Fig. 4 shows an axonometric front view of the heater in Fig. 3;
Fig. 5 illustrates a schematic view in longitudinal section of an implementation of the heater in Fig. 1, comprising a liquid cooling circuit;
Fig. 6 shows an axonometric front view of the heater in Fig. 5;
Fig. 7 illustrates a schematic view in longitudinal section of an implementation of the heater in Fig. 1, comprising a Stirling engine;
Fig. 8 illustrates another implementation of the heater in Fig. 7, further comprising a liquid cooling circuit;
Fig. 9 shows a further implementation of the heater in Fig. 2, comprising a heat pipe-type cooling system;
Fig. 10 illustrates a schematic view in longitudinal section of an implementation of the heater in Fig. 1, comprising a heat pipe-type cooling device;
Fig. 11 shows an axonometric front view of the heater in Fig. 10;
Fig. 12 shows a schematic view in longitudinal section of a second embodiment of a gas heater according to the invention;
Fig. 13 shows an axonometric front view of the heater in Fig. 12;
Fig. 14 illustrates a schematic view in longitudinal section of an embodiment of the heater in Fig. 12, having a liquid cooling circuit;
Fig. 15 shows an axonometric front view of the heater in Fig. 14;
Fig. 16 illustrates a schematic view in longitudinal section of an embodiment of the heater in Fig. 12, further comprising a diesel oil pre-heating circuit;
Fig. 17 shows an axonometric front view of the heater in Fig. 16;
Fig. 18 illustrates a schematic view in longitudinal section of an embodiment of the heater in Fig. 12, comprising a heat pipe-type cooling circuit;
Fig. 19 shows an axonometric front view of the heater in Fig. 18;
Fig. 20 illustrates a third embodiment of the invention, relative to a diesel oil irradiation heater, comprising two energy conversion cells to supply a combustion air adduction fan;
Fig. 21 shows an axonometric front view of the heater in Fig. 20;
Fig. 22 illustrates a schematic view in longitudinal section of an embodiment of the heater in Fig. 20, having two energy conversion cells arranged to withdraw heat by conduction directly from the combustion chamber wall;
Fig. 23 illustrates a schematic view in longitudinal section of an embodiment of the heater in Fig. 20, in which each energy conversion cell comprises a respective cooling fan;
Fig. 24 shows an axonometric front view of the heater in Fig. 23;
Fig. 25 shows a schematic view in longitudinal section of an embodiment of the heater in Fig. 20, a liquid cooling circuit;
Fig. 26 shows an axonometric front view of the heater in Fig. 25;
Fig. 27 illustrates a schematic view in longitudinal section of a fourth embodiment of the heater according to the invention, which is suitable for high flow rates, comprising a plurality of energy conversion cells to actuate a generating fan, and a tube bundle thermal exchanger;
Fig. 28 shows a schematic view in longitudinal section of an implementation of the heater in Fig. 27, having a liquid cooling circuit;
Fig. 29 shows a schematic view in longitudinal section of an embodiment of the heater in Fig. 27, having a heat pipe-type cooling circuit;
Fig. 30 shows a flowchart describing an operation of the heater.

Reference will be made herein below to a "cell with direct conversion of thermal energy into electric power" to indicate a device, such as the so-called Seebeck cells, which use a thermal-electric effect whereby a temperature differential at the ends of a conductor or semiconductor generates an electric potential.
Reference will be made to a "Stirling engine" to indicate: an external combustion engine capable of converting an external thermal energy, anyhow generated, into kinetic energy according to any configurations of detail of the same engine. The configurations known to date are different (alpha, beta, gamma, rhombic, free piston, etc.) and under development, both in the overall configuration and in its details and components.
Reference will be made to "heat pipe" to indicate: a system that is known in a number of fields, which is capable of efficiently transferring high amounts of heat in a short time by virtue of the use of the material properties to absorb or to release a lot of heat during phase transition (latent heat).
With reference to the Figures, a portable liquid or gaseous fuel heater to heat air according to the invention is generally indicated with the reference 1, 101, 201, 301.
In a general embodiment, the heater 1, 101, 201, 301 comprises a combustion chamber 10, 110, 210, 310 defined by a first delimitation wall 11, 111, 211, 311. Such a first delimitation wall can be, for example, substantially tubular, or cylindrical, as in the case of the heaters indicated with the numbers 1, 101, 301 and with reference to the Figures 1-19 and 27-29, or it can be substantially conical or "bell-shaped", as in the case of the heaters 201 of the Figures 20-26.
The heater 1, 101, 201, 301 comprises suitable fuel adduction ducts 12, 112, 212, 312 leading to the outside of the combustion chamber 10, 110, 210, 310.
The heater 1, 101, 201, 301 further comprises first forced ventilation means 13, 113, 213, 313 so configured as to generate an combustive air flow 14, 114, 214, 314 through said combustion chamber 10, 110, 210, 310 in preset pre-mixing conditions between combustive air and fuel.
Furthermore, the heater 1, 101, 201, 301 comprises an energy converter 20, 50 arranged with a first thermal exchange portion 21, 51 in thermal contact with the inside of the combustion chamber (10) at a first temperature T1 and a second thermal exchange portion 22, 52 in thermal contact with the external environment 19 at a second temperature T2, so configured as to convert the temperature differential between said first temperature T1 and said second temperature T2 into energy that is suitable to supply said first forced ventilation means 13, 113, 213, 313.
In the present description, the first thermal exchange portion 21 will be referred to also as "hot portion", since it is suitable to be heated, and the second thermal exchange portion 22 will be referred to also as "cold portion", since it is suitable to be cooled.
The energy converter 20, 50 is connected to said first forced ventilation means 13, 113, 213, 313 so as to actuate the first forced ventilation means 13, 113, 213, 313.
A first embodiment of the present invention is shown in the Figs. 1-11. Such an embodiment uses a gas as a fuel.
In accordance with this embodiment, the combustion chamber 10 has its first delimitation wall 11 having a substantially cylindrical shape. Such a wall can also have other shapes, for example, a prismatic shape, with any number of sides, with a sectional shape that is oval, polygonal.
At a rear base of this delimitation wall, an end 36 of the fuel adduction ducts 12 is arranged, for example, a nozzle 33 for dispensing gas into the combustion chamber.
At this rear base, a bottom plate 34 is arranged, preferably for partially closing the combustion chamber 10 so as to provide openings 35, 37 that are suitable to the insertion of oxidizing air into the combustion chamber 10.
In particular, such openings can comprise an annular opening 35 interposed between the bottom plate 34 and the first delimitation wall 11 of the combustion chamber 10. For example, such an annular opening 35 is arranged along the outer edge of the bottom plate 34. In other words, the annular opening 35 follows the inner surface of the first wall 11 of the combustion chamber. The annular opening preferably has a substantially constant width. Furthermore, the end 36 of the adduction ducts 12 is preferably in a central position with respect to the bottom plate 34; therefore, in other words, the nozzle 33 for the adduction of gas 12 into the combustion chamber 10 is surrounded by said annular opening 35.
Such an arrangement of the annular opening allows generating an combustive air flow that internally skims the first wall 11 of the combustion chamber, separating the flame 38 from the first wall itself. This allows cooling the same wall, keeping it at an operative temperature suitable to not thermally damage the heater components.
The above-mentioned openings for inputting oxidizing air can comprise at least one hole 37 passing through the bottom plate 34, in positions suitable to properly feed the flame and optimize the combustion process.
In addition, or alternatively, openings adjacent to the gas dispensing nozzle can be provided, for example, an annular opening adjacent to and surrounding the nozzle 33.
The bottom plate 34 can be, for example, interposed between the first ventilation means 13 and the combustion chamber 10.
Such adduction ducts 12 can be configured to withdraw gas from a cylinder on board of the heater, or, preferably, from an external gas supply (not shown in the Figures).
The ventilation means comprise a first fan 13 actuated by an electric motor 39 and arranged so as to generate a first air flow 14 and direct it inside the combustion chamber 10, in particular through the openings 35, 37.
In other terms, the fan 13 is arranged on the opposite side of the combustion chamber with respect to an output port 60 for hot air and the combustion products.
The first fan 13 is arranged externally to the combustion chamber 10, and it is preferably arranged on the opposite side of the bottom plate 34 with respect to the combustion chamber.
According to an implementation of this first embodiment, the heater 1 comprising second forced ventilation means 13' so configured as to generate a second forced air flow 16 so that said second flow 16 externally skims the first delimitation wall 11 of the combustion chamber 10 and so that this second heated air flow 16 is inputted to the environment after skimming the first delimitation wall 11 and after being heated.
In particular, these second forced ventilation means comprise a fan 13', and in particular the fan 13' coincides with the fan 13. In other words, the above-mentioned implementation comprises only one fan 13 generating an air flow that divides into a first flow 14 within the combustion chamber 10, which mixes with the combustion fumes and exits the combustion chamber 10 through the output port 60 of the combustion chamber 10, and a second flow 16 of air free from combustion fumes, which externally skims the combustion chamber.
In other words, the first ventilation means 13 and the second ventilation means 13' coincide.
According to another embodiment, the first flow 14 and the second flow 16 are produced by distinct fans.
According to a preferred embodiment shown in the Figs. 1-11, the portable heater 1 comprises a second delimitation wall 31 surrounding externally the first delimitation wall 11 thus forming an interspace 32 therebetween, so configured as to be passed through by the second forced air flow 16.
In particular, the second delimitation wall 31 is a continuous wall free from side openings. In other words, the second delimitation wall 31 forms, together with the first delimitation wall 11, a continuous side wall chamber.
The second delimitation wall 31 is not formed by a net. In other words, the second delimitation wall 31 is a continuous structure that prevents a gas or air from passing therethrough.
The energy converters used in the present invention allow exploiting a temperature differential to convert it into an energy suitable to actuate the ventilation means, for example, the fans. Therefore, such converters have a first thermal exchange portion 21, 51, which has to be put into thermal contact with the inside of the combustion chamber 10 and a second thermal exchange portion 22, 52 in thermal contact with the external environment.
The energy produced by these converters depends on the value of the difference between the temperatures applied to the first thermal exchange portion and the second thermal exchange portion, therefore, the higher this difference is, the more is the energy produced.
Therefore, the energy produced by the converter will be as higher as the more the heat withdrawn from the thermal exchange portion at a lower temperature will be, i.e., the second thermal exchange portion 22, 52.
For this reason, the portable heater comprises cooling means, for example, a fluid 40, that are so configured as to generate a third forced flow 15 of cooling fluid to exchange heat with said energy converter 20 at said second temperature T2.
In particular, as shown in the Figs. 1-4, the fluid cooling means 40 comprise third forced ventilation means 13" and said fluid is environmental air, in which said third ventilation means 13" are actuatable by said energy converter 20.
In other words, a third forced air flow 15 is used, to cool the second thermal exchange portion 22, 52 of the energy converter 20, 50.
This third forced flow 15 may, for example, but not necessarily, be generated by the first ventilation means 13.
In the implementation of Figs. 1-11, the third forced flow 15 is generated by a fan 13" which is the same as the fan 13 that generates the first forced flow 14.
In such implementation, the heater comprises a conveying manifold 41 to convey the third forced flow 15 for cooling downstream the energy converter 20, for example, so that the third flow 15 is inputted in said interspace 32 and forms, or contributes to, said second forced flow 16.
In accordance with an implementation, the heater comprising a conveying manifold 41 to convey said third forced cooling flow 15 downstream the energy converter 20, so that said third flow 15 is inputted in said interspace 32 and forms, or contributes to, said second forced flow 16.
In accordance with the implementation shown in the Figs. 5, 6, 8, the cooling fluid is a cooling liquid 17, and said fluid cooling means 40 can, for example, but not necessarily, comprise a pump 45 actuatable by said energy converter 20, 50, which pump is hydraulically connected to a cooling circuit having a thermal exchange surface with said second thermal exchange portion 22, 52 of the energy converter.
In accordance with an implementation, shown in the Figs. 9-11, 18, 19-21, 29, the portable heater comprises cooling means comprising a heat pipe-type circuit 80 having an evaporation portion 81 in thermal contact with the combustion chamber 10, 110, 210, 310 and a condensation portion 82 in thermal contact with the external environment 19, in which the evaporation portion is fluidically connected to the condensation portion though a connecting duct 83.
In order to promote the heat transmission between the combustion chamber 10, 110, 210, 310 and the converter 20, 50, the heater can comprise a first thermal exchange member or first heat sink or first radiator 23 having a first end so configured as to be brought in direct thermal contact with the first thermal contact portion 21, 51 of the converter, and a body so shaped as to exhibit a high thermal exchange surface.
For example, the thermal exchange member 23 comprises an elongated metal element from which a plurality of tabs extends. In particular, the thermal exchange member 23 is secured to the combustion chamber so as to internally project from said combustion chamber, in particular to be directly hit by the combustion flame.
In order to facilitate the heat transmission between the converter 20, 50 and the external environment 19, the heater may comprise a second thermal exchange member or second heat sink or second radiator 25 having a first end so configured as to be brought in direct thermal contact with the second thermal contact portion 21, 51 of the converter, and a portion to exhibit a high thermal exchange surface.
In accordance with an implementation, as shown in the Figs. 1-6 and 10-29, the energy converter is a cell 26 for the direct conversion of thermal energy into electric power, in particular, a Seebeck cell.
The direct conversion cell 26 has two cell electric contacts or cables 27 of the cell, suitable to provide in output an electric potential difference as a function of the difference in the temperatures applied to the cell.
In accordance with other implementations shown in Figs. 7-9, the energy converter 50 is a Stirling engine having a motion output member (not shown in the Figures). In particular, the motion output member can be connected in input to a mechanical electric power generator, for example, an alternator or a dynamo (not shown). In other known configurations (free piston Stirling engine, for example), the energy generator can be integrated at the base of the engine body itself.
Since the force and movement speed of the Stirling engine output member is proportional to the difference in temperature applied to the same Stirling engine, the associated electric generator will provide in output an electric potential that is proportional to the above-mentioned temperature difference.
Therefore, the electric generator associated to the Stirling engine has two electric contacts or cables that are suitable to provide in output an electric potential difference that is proportional to the difference in the temperatures.
According to an implementation, the heater comprises at least one electrovalve 92 for opening/closing and/or adjusting the fuel flow through the adduction duct 12.
In accordance with an implementation, the heater comprising a control unit 93 connected to the first ventilation means 13 that is so configured as to influence the mixing ratio between the oxidizing air and the fuel, so that the amount of oxidizing air inputted into the combustion chamber is higher than the amount of air necessary to the combustion.
In particular, the control unit 93 can be connected to drive also the second ventilation means 13' and, in addition or alternatively, to said cooling means 40.
In accordance with an implementation, the heater 1, 101, 201, 301 comprises a flame sensor (not shown), so configured as to detect the presence of a flame in the combustion chamber and to provide in output a corresponding signal. In particular, the flame sensor can be connected to the control unit 93.
Furthermore, the control unit 93 can be connected to drive the adduction pump and the adjustment valve 93, beside to igniters 79, sensors, other pumps, and other consumptions (not shown).
In accordance with an implementation, the heater comprises a managing unit 94 for managing the electric power produced by the energy converter 20, 50, and an electric connection 96 suitable to be connected to a starting battery 95, said managing unit 94 being electrically connected to said energy converter 20, 50, to said control unit 93, and being connectable to said starting battery 95, said managing unit being configured so that, upon reaching a preset threshold value of energy produced by the energy converter (20, 50), the energy supply by the starting battery 95 is discontinued.
In accordance with an implementation, the above-mentioned control unit 93, and the above-mentioned energy managing unit 94 can be mutually integrated, eg., on a single electronic circuit.
In accordance with an alternative implementation, the starting battery can be connected to continuously supply the first ventilation means 13, and optionally all the other electric consumptions on board, in which said starting battery is connected to the converter 20, 50 to be continuously recharged.
In accordance with a second embodiment of the present invention, shown in the Figs. 12-19, the heater is supplied with a liquid fuel, particularly diesel oil.
Such a heater comprises a fuel tank 199 on board, for example, arranged underneath the combustion chamber 110.
This heater differs from the gas heater of the preceding figures in the following aspects.
It relates to an "indirect" model; therefore, the combustion chamber 111 opens to a chimney 198 configured to outflow the combustion fumes into a duct, which preferably opens to the outside of the environment to be heated. In this manner, the fumes produced by combustion are prevented from being inputted into the environment to be heated.
Again, in this second embodiment, first ventilation means 113 generate a first forced combustive air flow 114 to input it into the combustion chamber 110, through openings 35 at an end of the combustion chamber 110.
In accordance with a third embodiment of the present invention, shown in the Figs. 20-26, the heater 201 comprises a front grill 297, which, when overheated by the flame in the combustion chamber 210, heats an environment by irradiation.
Unlike the first embodiment, this heater uses a liquid fuel, for example, diesel oil, as for the second embodiment.
As in the preceding embodiments, first ventilation means 213 generate a first forced combustive air flow 214 in the combustion chamber 210, into which the fuel is also inputted.
This heater differs from the gas heater of the first embodiment in the following aspects.
The combustion flame 38 is directly oriented against the front grill 297, thus heating it to temperatures belonging to the "red heat" zone.
At these temperatures, the grill irradiates heat only in an area on which the radiations emitted by the front grill 297 are projected by irradiation. In other words, this type of heater performs a very powerful selective heating and with a reduced movement of air, which is suitable in particular cases.
The tubular combustion chamber 210 has a conical shape so as to optimize the temperature distribution and the diffusion of heat within the combustion chamber 210.
A fourth embodiment is shown in Figs. 27 to 29. The heater 301 is suitable to produce high hot air flow rates.
As for the other embodiments, first ventilation means 313 are present, which generate a first forced oxidizing air flow 314 in the combustion chamber, for example, through an injection head 323
A second forced flow 316 is instead generated by second ventilation means 313" that are, in particular, but not necessarily, different from the first ventilation means 313.
The combustion chamber 210 has an output duct 362, from which a tube bundle 363 originates, which tube bundle opens to a discharge manifold of the combustion fumes 364. The second forced flow 316, before going out from the output ports 360 and 361, is heated also by skimming the tube bundle 363.
In all the implementations described above, at least one thermal energy converter is present, which exploits the temperature difference between the combustion chamber and the lower environmental temperature to produce electric power and/or kinetic energy to actuate the first ventilation means 13, 113, 213, 313, for example, a fan actuated by an electric motor to generate a first forced combustive air flow sent into the combustion chamber, without requiring any electric power external supply.
According to a further aspect of the present invention, the above-mentioned objects and advantages are met by a method to heat an environment through a portable gaseous or liquid fuel heater, comprising the steps of:

providing a combustion chamber defined by a first delimitation wall;
providing fuel adduction ducts to the inside of the combustion chamber;
providing first forced ventilation means configured to generate an oxidizing air flow through said combustion chamber;
providing an energy converter configured to convert the temperature difference between a first temperature inside the combustion chamber and a second temperature of the external environment, into an energy that is suitable to supply said firs ventilation means;
said method further comprising the steps of:
- activating a starting forced flow of oxidizing air in said combustion chamber;
- supplying fuel to the inside of the combustion chamber;
- starting the combustion by an electric spark or arc so as to create a temperature difference between the inside of the combustion chamber and the outside.

In accordance with an implementation, a step is provided of:

converting the temperature difference between the inside of the combustion chamber and the outside environment into energy by means of said energy converter;
actuating by said energy said first forced ventilation means while maintaining an oxidizing air flow, a fuel flow, and an optional starting electric arc or spark through said combustion chamber in preset mixing conditions between oxidizing air and fuel.

An operation of a heater 1, 101, 201, 301 according to the invention is described herein below, in particular, the operating logic of such a heater having an energy converter 20, 50 and a managing unit 94 for managing the electric power generated by the converter 20, 50 will be described.
Upon starting (501) of the heater, for example, by actuating a starting switch, and in the presence of an initial electric power input (502), which will be described herein below, a fan actuation step (503) takes place, which fans generate an air flow (508) in the combustion chamber. Upon starting, also the generation of an electric arc (504) to spark a starting off spark takes place, the opening of an optional electrovalve (505) to input a fuel 506 into the combustion chamber, and starting (507) an injection pump 180 of the fuel or, alternatively, a fuel supply by Venturi effect. A fuel flow (509) is thus started in the combustion chamber.
The above-mentioned steps, taking place upon starting (501) can be performed simultaneously or according to any relative temporal sequence.
The cooperation in the combustion chamber of the air flow (508), the fuel flow (509), and the generation of an electric arc (504) leads to the generation (510) of a flame.
A flame sensor arranged in the combustion chamber can perform a verification step (511) for the presence of a flame inside the combustion chamber.
In the case that an absence of the flame is detected, a turning off step (512) of the heater is carried out, for example, comprising a step of interrupting the fuel flow by actuating the above-mentioned electrovalve.
On the contrary, in the case that the presence of a flame is detected in the combustion chamber, the combustion proceeds without being discontinued, thus generating a hot air (515) outflow.
Thus, the flame generation (510) causes the heating (513) of the first thermal exchange portion 21 of the converter 1, 101, 201, 301.
At the same time, a cooling step (514) of the second thermal exchange portion 22 of the converter is operated, in order to make the temperature difference between the first portion 21, 51 and the second portion 22, 52 of the converter 20, 50 as high as possible, so as to obtain in output a potential difference as high as possible.
This cooling step (514) is carried out by withdrawing heat (516) to the second portion 22, 52 by means of a cooling flow 40 in conditions of thermal exchange with the second portion 22, 52, for example, through the third forced flow 15, described above, or through a liquid cooling circuit 17, cooling means of the heat pipe-type 80 as described above.
Heating the first thermal exchange portion 21, 51 and the simultaneous cooling of the second thermal exchange portion 22, 52 produces a temperature difference relative to each other (517), also referred to as a thermal "delta".
In the case that the converter is a direct conversion cell 26, the temperature difference is directly converted into electric power (518).
Alternatively, if the converter is a heat engine converting a temperature difference into kinetic energy, such as, for example, a Stirling engine 50, an intermediate step takes place, of production of kinetic energy (519) take place. In such a case, the kinetic energy outputted by the thermal machine can be directly used to move the ventilation means.
Alternatively, a mechanical generator (520) of electric power is associated to the thermal machine, for example, a dynamo or an alternator.
The electric power, directly or indirectly generated by the converter 20, 50, is subjected to an optional step of current stabilization (521).
In accordance with an implementation, a verification step (522) is carried out, to verify whether the value of the electric power produced by the converter 20, 50 by virtue of the temperature difference exceeds the value of the powers required by the consumptions on board of the heater, thus forming an electric power excess.
Alternatively, the verification step (522) is to verify whether the value of the electric power produced by the converter 20, 50 by virtue of the temperature difference exceeds a preset threshold value, thus forming an electric power excess.
If the value of the electric power produced by the converter 20, 50 does not exceed the value of the power required by the consumptions on board of the heater, or the threshold value, the electric power produced is used to self-supply the heater, in particular, to electrically supply all the ventilation means and the control unit and the managing unit.
According to an embodiment, the electric power produced is used to supply the cooling means and/or the supplying pump.
In other words, if the value of the electric power produced by the converter 20, 50 does not exceed the value of the power required by the consumptions on board, or the threshold value, the electric power produced is the electric power input (502) described above. In such a manner, the heater according to the invention is self-supplied, does not requires an external electric power for its operation, and ensures a proper oxidizing air flow in the combustion chamber, reducing the CO produced by the combustion.
On the contrary, if the value of the electric power produced by the converter 20, 50 exceeds the value of the power required by the consumptions on board, or the threshold value, thus generating an excess of electric power, a step (523) is performed, of sending this excess to a recharging device of a buffer electric battery (524).
In particular, this buffer electric battery 524 corresponds to the starting battery 95 described above.
The energy produced by this buffer battery is used to form or concur to the input energy 502 described above.
To the embodiments of the device described above, those of ordinary skill in the art, with the aim of meeting contingent needs, will be able to make modifications, adaptations, and replacements of elements with other functionally equivalent ones, without for this departing from the scope of the following claims. Each of the characteristics described as belonging to a possible embodiment can be implemented independently from the other embodiments described.

Claims

A portable fuel heater (1, 101, 201, 301) to heat air, comprising:
- a combustion chamber (10, 110, 210, 310) defined by a first delimitation wall (11, 111, 211, 311);

- fuel adduction ducts (12) leading to the inside of the combustion chamber (10, 110, 210, 310);

- first forced ventilation means (13) configured to generate a combustive air flow (14) in the combustion chamber (10), where it reacts with the fuel;

- an energy converter (20, 50) arranged with a first thermal exchange portion (21, 51) in thermal contact with the combustion chamber (10, 110, 210, 310) and a second thermal exchange portion (22, 52) that is distinct from said first exchange portion, configured to convert the thermal energy of the temperature difference between the first thermal exchange portion (21, 51) and the second thermal exchange portion (22, 52) into electric energy, said energy converter (20, 50) being connected to actuate said first forced ventilation means (13),

- said energy converter comprising a Seebeck effect cell (26) for the direct conversion of the temperature difference into electric power;
characterized in that:
said first forced ventilation means (13) further generates a forced cooling air flow (15) to cool the second thermal exchange portion (22, 52) of the energy converter (20, 50).
The portable heater according to claim 1, wherein the first ventilation means (13) generates an airflow that divides into said combustive air flow (14) within the combustion chamber (10) suitable for mixing with combustion fumes and exiting the combustion chamber through an output port of the combustion chamber and a second forced air flow (16) free from combustion fumes which externally skim the combustion chamber (10).
The portable heater according to claim 1, comprising a second forced ventilation means (13') configured to generate a second forced air flow (16) so that said second flow (16) externally skims said first delimitation wall (11) of the combustion chamber (10) and so that said second heated air flow (16) is inputted into the environment after skimming the first delimitation wall (11), said second forced ventilation means (13') being connected to be supplied by said converter (20, 50).
The portable heater according to claim 2 or 3, comprising a second delimitation wall (31) externally surrounding said first delimitation wall (11) forming an interspace (32) therebetween, said second delimitation wall (31) being a continuous wall without side openings, said interspace (32) being configured to be passed through by said second forced air flow (16).
The portable heater according to any of the preceding claims, comprising cooling means (40) configured to generate a third forced flow (15) of cooling fluid in conditions of thermal exchange with the second thermal exchange portion (22, 52), wherein said cooling means (40) are connected to be supplied by said energy converter (20, 50).
The portable heater according to claim 5, wherein said cooling means (40) comprise third forced ventilation means (13") of environmental air.
The portable heater according to claim 2, comprising a conveying manifold (41) for conveying said forced cooling flow (15) downstream of the energy converter (20) so that said forced cooling flow (15) is inputted into said interspace (32) and forms said second forced flow (16).
The portable heater according to claim 5, wherein said cooling fluid is a cooling liquid, and wherein said cooling means (40) comprise an hydraulic circuit (17) in conditions of thermal exchange with said second thermal exchange portion (22, 52) of the energy converter (20, 50).
The portable heater according to claim 1 or 3 or 6, wherein at least one of said first forced ventilation means (13), said second forced ventilation means (13'), said third forced ventilation means (13'') comprise a rotor or fan associated to an electric motor connected to be supplied by the converter (20, 50).
The portable heater according to any of the preceding claims, comprising a valve (92) for the adjustment of the fuel flow rate, connected to said adduction ducts (50).
The portable heater according to any of the preceding claims, comprising a managing unit (94) for managing the electric power produced by the energy converter (20, 50), an electrical connection (96) for connecting said managing unit (94) to a starting battery (95), said managing unit (94) being electrically connected to said energy converter (20, 50) and to a control unit (93), said managing unit (94) being configured so that, upon reaching a preset threshold value of energy produced by the converter (20, 50), the energy supply by the starting battery (95) is discontinued.
A method to heat an environment through a portable fuel heater according to the features of at least one of the preceding claims, comprising the steps of:
- providing a combustion chamber defined by a first delimitation wall;

- providing fuel adduction ducts (12) to the inside of the combustion chamber;

- providing first forced ventilation means configured to generate an combustive air flow in said combustion chamber;

- providing an energy converter (20, 50) arranged with a first thermal exchange portion (21, 51) in thermal contact with the combustion chamber (10, 110, 210, 310) and a second thermal exchange portion (22, 52) distinct from said first portion, configured to convert the thermal energy from the temperature difference between the first thermal exchange portion (21, 51) and the second thermal exchange portion (22, 52) into a electric energy, said energy converter (20, 50) being connected to actuate said first forced ventilation means (13), and said energy converter (20, 50) comprising a Seebeck effect cell (26) for the direct conversion of the temperature difference into electric power;
said method further comprising the steps of:
- activating a starting forced flow of combustive air in said combustion chamber;

- supplying fuel to the inside of the combustion chamber;

- starting the combustion so as to create a temperature difference between the inside of the combustion chamber and the outside;

- generating electric power through said energy converter;

- actuating through said energy said first forced ventilation means generating a combustive air flow through said combustion chamber in preset mixing conditions of oxidizing air and fuel;
the method being characterized in comprising a step of:
- further generating a forced cooling air flow (15) by means of said first forced ventilation means (13) to cool the second thermal exchange portion (22, 52) of the energy converter (20, 50).