FR3073575A1 - HEAT EXCHANGE SYSTEM - Google Patents

Abstract

The invention relates to a heat exchange system (100) comprising: a first circuit (15) for the circulation of a fuel (14); a second circuit (10) for the circulation of a coolant (5); a heat exchanger (8) allowing the heat exchange between the fuel (14) and the coolant (5). It is expected that, the heat exchanger (8) comprising a succession of plates (18) delimiting two by two channels (28, 29), the heat exchanger (8) comprises a first inlet (12) and a first outlet (13) for the first circuit (14) so that a portion (29) of said channels (28, 29) forms a portion of the first circuit (15) as well as a second input (21) and a second output (22). ) for the second circuit (3) so that the remaining portion (28) of said channels (28, 29) forms part of the second circuit (10), the channels of the first circuit (29) and the second circuit (28) being alternate when one follows the succession of plates.

Description

HEAT EXCHANGE SYSTEM

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a heat exchange system for heating a fuel before combustion, for example in a boiler. The invention also relates to a boiler comprising such a heat exchange system.

The invention relates to a heat exchange system intended for example for heating domestic heating oil. This heat exchange system can be installed in boilers arranged without limitation in individual houses, buildings of all sizes, industries, factories.

TECHNOLOGICAL BACKGROUND

We know the effects of heating fuel oil on its physical appearance. This process was tested in 1903, by Mr. William COHEN, from Tennessee (United States of America).

The heating of this fuel, has the effect, at 90 ° C of reducing in its almost totality, the viscosity contained in the liquid, which causes, conversely, a very significant increase in its mass volume, thus making the cleaner fuel and better flammability.

We know many patents on the preheating of fuel oil, some reheating very large quantities or on the contrary very small volumes.

For example, it is known from patent application FR2796134 published on 2001-01-12 and invented by ourselves, a fuel oil preheating device comprising a heated circuit in which the fuel oil circulates before its combustion, in particular in a boiler. According to this patent application, the device comprises at least one heating body (1, 2, 3) formed by an external element (8 a, b, c) and an internal element (7 a, b, c) nested and extending longitudinally in the same direction so as to define, between the internal wall of the external element (8 a, b, c) and the external wall of the internal element (7 a, b, c), an intermediate space constituting the heated circuit. This patent application is applicable to the preheating of fuel oil before its use in particular in boilers.

At the time it was necessary to make savings on fuel. However, despite some advances in the field, heating engineers have never been unanimous in the use of these processes.

The main reasons are in our opinion their volume, their weight, their design, their price and their cost / economy ratio. We therefore had to take into account all these criteria to achieve a system eliminating all these disadvantages.

Some preheaters had very large volumes, others used coils. In all these preheaters, the same defect appeared.

Note that the incoming cold fuel oil, sent by a 12 to 14 bar pump, cooled the hot fuel oil, yet heated by resistors often exceeding 3000 watts. The fact is that these preheaters heated volumes in the coils with a small exchange surface, therefore very difficult to heat constantly, throughout the duration of the burner cycle.

For our system, we have increased the exchange surface while at least partially solving the drawbacks.

OBJECT OF THE INVENTION

The object of the invention is to respond to this wish while remedying at least one of these aforementioned drawbacks.

According to the invention, a heat exchange system is proposed comprising:

a first circuit for the circulation of a fuel;

a second circuit for the circulation of a heat transfer fluid;

a heat exchanger allowing the heat exchange between the fuel and the heat transfer fluid;

According to a general characteristic, the heat exchanger comprises a succession of plates delimiting two by two of the channels, the heat exchanger further comprises a first inlet and a first outlet for the first circuit so that a part of said channels forms a part of the first circuit, the heat exchanger also comprises a second inlet and a second outlet for the second circuit so that the remaining part of said channels forms part of the second circuit, and the channels of the first circuit and of the second circuit are alternated when the 'we follow the succession of plates.

Preferably, the second circuit forms a closed circuit and in this case comprises a safety valve.

This avoids the use of a coil disposed in a container and in which circulates a volume of fuel, this volume having a limited exchange surface with the liquid of the container.

On the contrary, with these plates, the exchange surface is maximized with respect to the volumes of the channels by choosing a low height of the channels, for example less than 3 mm, preferably less than 1.5 mm, this allows a good temperature rise of the combustible.

The plates are preferably delimited by two parallel planes so that the heat exchanger is easy to build.

Because the channels of the first circuit and the second circuit are alternated when following the succession of plates, each plate disposed between two channels forms an exchange interface. In addition, the liquids contained in each of the two types of channels, intersect permanently, these being perfectly sealed with respect to each other.

It is possible, for example, to provide a minimum number of 10 exchange interfaces in order to allow sufficient heating of the fuel by the heat transfer fluid.

A simple exchange system is thus obtained, in which the fuel enters the exchanger to meander through channels defined by plates, for example made of stainless steel, and thus take the temperature of the heat transfer fluid, then exit from the exchanger. through the exit and go to the jets of a boiler.

It is the heat of the heat transfer fluid that we use to heat the fuel.

By heating the fuel, the yield is improved during the burning of the fuel. Indeed, a hot fuel, devoid of its viscosity, burns much better, and in almost all of it, hence automatically, less discharge of polluting gases into the atmosphere.

Indeed, we know the effect of pollution released by the combustion of fuels: oil, fuel, diesel, diesel. A real war is waged against these types of fuel, responsible for the deaths of several thousand people per year. The only cause of this pollution is the viscosity contained in these fuels. The existence of this viscosity is due to less refining than that of petrol, in order to obtain a cheaper fuel.

This is where our invention comes in: cleaning up this type of fuel. Indeed, the fact of heating said fuel, between 85 and 90 ° c, completely dissolves the viscosity, making fuel oil, fuel oil, diesel, diesel, as clean as petrol, therefore more combustible and above all less polluting .

It is a little as if these fuels undergo a second refining, more pushes than the first refining, in order to make it cleaner, devoid of its viscosity and consequently, less polluting.

In summary, the widespread use of our invention would save thousands of lives each year, especially among children and the elderly, the first victims of air pollution, due to exhaust gases, not only of all vehicles using these fuels, but also boats, factories, individual houses and all buildings.

On the other hand, the fouling of the sprinklers and of the boiler in general is reduced.

According to other characteristics taken individually or in combination:

-the plates are arranged so that hg = t x hc, where:

-hc is a height of the channels of the first circuit;

-hg is a height of the channels of the second circuit;

-t is between 1.8 and 2.5.

By choosing a factor greater than 1, the section of the channels of the second circuit is increased so that for a given flow rate in these channels, the speed decreases, which allows a more intense exchange with the channels of the first circuit. In addition, with larger section channels, the volume of the heat transfer fluid is greater than the volume of fuel, which makes it more difficult to change its temperature.

However, with a constant number of exchange interfaces, the height of the heat exchanger increases linearly with the factor t.

Thus, by choosing a range for the factor ranging from 1.8 and 2.5, an optimal compromise is obtained between on the one hand efficient heating of the fuel by the heat transfer fluid and on the other hand the height of the heat exchange system.

In particular, effective heating is understood to mean that the fuel is mainly heated by the heat transfer fluid and that marginally the heat transfer fluid is cooled by the fuel.

the heat exchanger of substantially parallelepipedal shape comprises a first side provided with the first outlet and the second inlet and a second side provided with the first inlet and the second outlet so that in the heat exchanger, the directions of circulation of the first circuit and the second circuit are opposite.

There is thus obtained in the heat exchanger, a more homogeneous heat exchange between the first and the second circuit.

the heat transfer fluid comprises ethylene glycol or demineralized water with alcohol.

It is a heat transfer fluid with a high boiling temperature, which makes it possible to use a heat transfer fluid heated to a temperature above 100 ° C., for example 135 ° C. in the case of a closed circuit, thus allowing faster and more intense heating of the fuel. Ethylene glycol is also known to those skilled in the art under the acronym MEG.

- the fuel is chosen from one of the following liquids: fuel oil, fuel oil, fuel oil, diesel or diesel.

These are fuels whose viscosity can be greatly reduced by heating. This allows an increase in efficiency in the boiler.

the second circuit comprises a storage tank with heat transfer fluid and a pump arranged between the storage tank and the heat exchanger for circulating the heat transfer fluid there.

By placing the heat exchanger just after the pump, good circulation of the heat transfer fluid in the channels is ensured in the second circuit.

-the heat exchange system includes a heating resistor arranged in the storage tank to heat the heat transfer fluid.

In addition, by placing the channels of the second circuit just downstream of the heating resistor and the pump, it is ensured that the heat transfer fluid is hot to heat the fuel in the channels of the first circuit.

-the heating resistance and the pump are configured so that the fuel temperature at the first outlet is between 85 ° C and 90 ° C.

It is indeed the ideal temperature for dissolving all of the viscosity contained in fuel oils, fuel oil, diesel, diesel. It is this viscosity which prevents the fuel from burning completely. Without this viscosity, we obtain the equivalent of a fuel that has undergone further refining until it becomes gasoline.

Once this viscosity has disappeared, the temperature of 90 ° C allows the fuel oil to develop its mass volume of 30 to 35%, depending on the quality of the fuel, to obtain better combustion and to eliminate the polluting gases which poison l 'atmosphere.

It is therefore at this temperature that the fuel has the lowest viscosity and a better efficiency during its combustion while avoiding coking.

-the pump is configured so that in the heat exchanger, the flow of the heat transfer fluid is at least 100 times that of the fuel.

The amount of heat transfer fluid circulating between the plates is a function of the pump flow. Thus, with a flow rate which is disproportionate to what the flow rate of the fuel consumed by the nozzle may be, this ensures perfect heating of the fuel and the cooling of the heat transfer fluid by the fuel is avoided.

An almost constant temperature of the heat transfer fluid is therefore ensured while the temperature of the fuel will tend towards that of the heat transfer fluid after it has been heated by the heating resistor.

-the heat exchange system comprises a housing containing the heat exchanger and the two circuits and in that it comprises rock wool disposed in the housing around the heat exchanger and the storage tank.

There is thus obtained a substantially isothermal housing, in particular at the level of the heat exchanger and therefore a constant temperature of the heat exchanger and of the heat transfer fluid.

The invention also relates to a boiler comprising:

-a combustion chamber,

-a nozzle for bringing fuel into the combustion chamber,

a burner connected upstream of the nozzle, the burner being provided with a fan, said fan being supplied by an electrical connection, and

-a heat exchange system as described above.

According to a general characteristic, the first circuit of the heat exchange system being connected upstream of the nozzle, the pump is connected to the electrical connection of the fan so that the pump operates in synchronization with the cycles of the boiler.

Thus, the pump operates only during the burner operating time, which is approximately 3 minutes, reducing the energy expenditure of the pump as much as possible.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will appear on examining the detailed description of modes of implementation and embodiments, in no way limiting, and the appended drawings in which:

FIG. 1 represents, according to one embodiment, a block diagram of the invention.

FIG. 2 represents an embodiment of the exchanger according to the invention.

FIG. 3 schematically represents a boiler according to the invention.

DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

In FIG. 1, we can see a heat exchange system 100 comprising:

a first circuit 15 in which a fuel 14 flows in a direction of circulation 16

a second circuit 10 in which a heat transfer fluid 5 circulates in a direction of circulation 11

- a tank, for example made of stainless steel 1, for the heat transfer fluid

a heating resistor 2 arranged in the tank, to heat the heat transfer fluid there

-a thermostat 3

a filling cap for the heat transfer fluid 4

-a safety valve 6 for the second circuit 10

a heat exchanger 8 comprising a succession of plates 18

an inlet 12 for the fuel 14 in the heat exchanger 8, called the first inlet

an outlet 13 for the fuel 14 in the heat exchanger 8, called the first outlet

an inlet 21 for the heat transfer fluid 5 into the heat exchanger 8, called the second inlet

an outlet 22 of the heat transfer fluid 5 in the heat exchanger 8, called the second outlet

a channel 28 between two plates 18 in which the heat transfer fluid 5 circulates

a channel 29 between two plates 18 in which the fuel 14 circulates

an inlet 27 of the first circuit 15 through which enters the fuel 14

an outlet 17 of the first circuit 15 through which the heated fuel 14 leaves towards the nozzles of a boiler (not visible in FIG. 1, visible in FIG. 3)

-a rock wool disposed in particular in the housing around the heat exchanger 8 and the tank 1

a housing 20 which may include a cover crimped by rivets

-a carrying handle 22

-an electrical outlet for resistance 23

an electrical connection 24, this electrical connection 24 being used for supplying a fan of a burner of a boiler (not visible in FIG. 1, visible in FIG. 3) having a nozzle of which the first circuit 15 is placed upstream via exit 17

-a cable gland 25 of the electrical connection 24

-four feet of the housing 26

The heat transfer fluid may for example be demineralized water added with alcohol 5.

The heat exchanger 8 is composed of a succession of plates 18 which form number X of channels of the second circuit 28 and a number Y of channels of the first circuit 29, X being substantially equal to Y. As will be explained in FIG. 2 , it is for example provided that in the heat exchanger 8, the channels of the second circuit 10 containing the heat transfer fluid 5 have a capacity double that of the channels of the first circuit 15 containing the fuel 14, thus ensuring better heating of the fuel 14 .

In addition, the channels of the first circuit 29 and the second circuit 28 are alternated when following the succession of plates, so that each plate disposed between two channels forms an exchange interface and that the channels 28 and 29 of the heat exchanger 8 are constantly crossing. However, the two liquids, the heating heat transfer fluid and the heated fuel, cannot mix, each of the two circuits being perfectly isolated from one another by the sealed plates 18.

The second circuit 10 comprises for example at least one pipe. These include the return pipe of the heat transfer fluid 5 to the tank 1.

In this case, rock wool can be provided around the return pipe and also a thermal insulating sheath 19 disposed on the return pipe. This pipe is for example a stainless steel tube.

The second circuit can include a pump 7 allowing the heat transfer fluid from the tank 1 to the heat exchanger 8 to circulate there. Advantageously, this pump is connected to the electrical connection 24 of the burner fan so that the pump 7 operates in synchronization with the cycles of the boiler 300 as is explained in more detail below.

In the second circuit 10, the heat transfer fluid 5 follows a cycle, tank, pump, heat exchanger, return pipe, tank. It is a closed, autonomous heating circuit, completely independent of any external input.

For example, the thermostat 3 is an integral part of the heating resistor 2. One can for example adjust the thermostat so that the low temperature of the heat transfer fluid is calibrated at 85 ° C while the high temperature is calibrated at 90 ° C.

The assembly of the two circuits and the heat exchanger is enclosed in the housing 20, itself supported by the four feet 26, ensuring very good stability. A handle 22 allows easy transport, the system being of a very light weight, for example not exceeding 6 kg.

The tank 1 and all of the elements contained in the housing 20 outside the pump are isolated by rock wool, ensuring perfect insulation. As a result, the start-up of the heating resistance becomes rare, because the temperature does not drop to 85 ° C until after nearly 200 burn cycles, the boiler operating in cycles as explained below.

In other words, it is described according to the embodiment of FIG. 1, a heat exchange system 100 comprising:

a first circuit 15 for the circulation of a fuel 14;

a second circuit 10 for the circulation of a heat transfer fluid 5;

a heat exchanger 8 allowing the heat exchange between the fuel 14 and the heat transfer fluid 5.

The heat exchanger 8 comprises a succession of plates 18 delimiting two by two of the channels 28, 29, a first inlet 12 and a first outlet 13 for the first circuit 15 so that a part 29 of said channels 28, 29 forms a part of the first circuit 15. It also includes a second input 21 and a second output 22 for the second circuit 10 so that the remaining part 28 of said channels 28, 29 forms part of the second circuit 10.

The first circuit and the second circuit jointly using the heat exchanger are however perfectly sealed with respect to each other.

In addition, the channels of the first circuit 29 and the second circuit 28 are alternated when following the succession of plates.

For example, the heat exchanger 8 is of substantially parallelepiped shape and comprises a first side 30 provided with the first outlet 13 and the second inlet 21 and a second side 31 provided with the first inlet 12 and the second outlet 22 so that in the heat exchanger, the directions of circulation of the first circuit 15 and of the second circuit 10 are opposite.

It can be provided that the pump 7 making it possible to bring the heat transfer fluid from the tank to make it circulate in the heat exchanger is configured so that in the heat exchanger 8, the flow rate of the heat transfer fluid 5 is at least 100 times greater than that fuel 14.

Furthermore, provision is made to connect the first circuit 15 of the heat exchange system upstream of a nozzle (not visible in FIG. 1, visible in FIG. 3).

FIG. 2 represents an embodiment of the exchanger according to the invention. In this FIG. 2, one can see one of the channels 29 of the first circuit 15 and one of the channels 28 of the second circuit 10.

As can be seen, channel 28 has a height hg while channel 29 has a height hc. More precisely, hc is the height between two plates of the channels of the first circuit 15 and hg is the height between two plates of the channels of the second circuit 10. The plates are spaced so that hg = tx hc, formula in which t is included between 1.8 and 2.5.

For example, in the case where there are 10 exchange interfaces, Y = 6 and X = 5 and the minimum height of the heat exchanger is:

H = 6xhc + 5xtxhc + 12xc = in which c is the thickness of a plate and hc is the height of channel 29,

That is to say in the case t = 2 and hc = 1.5 mm: H = 42 mm.

FIG. 3 illustrates a boiler 300 comprising:

-a combustion chamber 204

- a nozzle 201

a burner 202 fitted with a fan 203, the fan being supplied by an electrical connection 24 and

-a fuel pump 205 from 12 to 14 bars for example.

a heat exchange system 100 as described above, said heat exchange system being preferably arranged on a nozzle line 206 of the boiler, between the burner 202 and the nozzle 201.

It is expected that the first circuit 15 of the heat exchange system being connected upstream of the nozzle 201, the pump 7 is connected to the electrical connection 24 of the fan 203 so that the pump 7 operates in synchronization with the cycles of the boiler 200.

For example, the pump 7 has a low electrical power, for example of the order of 60 watts.

In the boiler 300, the nozzle 201 allows the introduction of the fuel 14 into the combustion chamber 204 for its combustion.

The boiler operates by cycle, that is to say that its operation includes several burning cycles, for example of 3 minutes. During a burn cycle, the fuel is brought by the nozzle 17 into the combustion chamber 204 and the fan 203 operates. Between two burn cycles, a rest cycle can be provided during which the fuel is not brought by the nozzle 17 into the combustion chamber 204.

During a burn cycle, the fan is supplied by the electrical connection 24 which is activated and the nozzle 17 supplies fuel 14. Since the pump 7 is connected to the electrical connection 24 this pump 7 pumps the fluid coolant 5 during the burn cycle. This is the time during which the fuel 14 is supplied to the nozzle 17 and therefore during which the heating of the fuel 14 by the heat exchange system is very relevant. During the rest cycles, the electrical connection 24 is not activated, it is for example at zero electrical potential, which means that the fan 203 but also the pump 7 do not operate.

Thus, the pump 7 operates only during a burn cycle corresponding to the operating time of the burner, that is to say approximately 3 minutes, reducing to the maximum the energy expenditure of the pump.

In other words, our concept as described in Figures 1, 2 and 3 includes the following:

1 °) A tank 1 preferably made of stainless steel intended to receive the heat transfer fluid for example demineralized water added with 5% alcohol, with a heating resistance 2 of 400 watts only with slow rise (in 4 hours) so not to denature demineralized water if necessary. The heating resistor 2 is provided with a thermostat 3 incorporated in the body of the heating resistor 2, to capture temperature variations in real time.

For example, the high temperature of the heat transfer fluid 5 is limited to 90 ° C., without this being able to be exceeded.

For example, the low temperature of the heat transfer fluid 5 is limited to 85 ° C., without this being able to drop lower.

2 °) A pump 7 for emptying the tank with an evacuation capacity of 3000 liters per hour, with a power of 60 watts. The pump 7 is advantageously connected to the electrical connection of the burner fan, in order to operate only during the burner operating time, ie approximately 3 minutes, reducing as much as possible the energy expenditure of the pump.

The pump 7 is provided with a high inlet receiving the heat transfer fluid 5 from the tank, with a low outlet for discharging this fluid in the heat exchanger 8.

3 °) The heat exchanger receives the heat transfer fluid 5 heated by the heating resistor and consists of plates forming channels 28 and 29. Some of these channels referenced 28 receiving the heat transfer fluid 5 while the other channels referenced 29 receive the fuel which instantly takes the temperature of the heat transfer fluid 5.

This heat exchanger, which we had manufactured for our needs, has a special feature: the channels 28 receiving the heat transfer fluid 5, for example, have a capacity which is twice that of the channels 29 receiving the fuel. As a result, the pump sends the same quantity of hot liquid, but this hot liquid stagnates longer than if the water / fuel plates had the same capacities. As a result, the heat transfer fluid 5 heats the fuel more intensely, while the latter cannot in any case cool the heat transfer fluid 5.

4 °) The second circuit includes a return pipe for example a stainless steel tube placed at the outlet 22 of the heat exchanger to enter the tank in order to bring the heat transfer fluid back into the tank.

Several tests have been carried out as explained below.

A 100 kW burner uses a first nozzle to expel air, of 6 gallons, and a second nozzle of 7 gallons for fuel consumption. Knowing that a gallon is equal to 3.7 liters, the consumption of this burner is: 3.7 X 7 = 25.9 liters. Let's say 26 liters per hour.

Our pump delivers 3000 liters / hour for a fuel consumption rate of 26 liters / hour. The enormous disproportion is then 100 times greater of the heating liquid compared to the liquid to be heated.

In the case of a 50 kW burner, the consumption the difference would then be 200 times.

In tank 1 which we fill with heat transfer fluid 5, we install a resistor 2 with a power of 400 watts with a slow rise in temperature, so that the heat transfer fluid 5 reaches 90 ° C.

Under the tank 1, we place a drain pump 7 with an evacuation capacity of 3000 liters an hour and only 60 watts. The pump 7 the heat transfer fluid 5 from the tank 1 to return it to the second inlet 21 of the heat exchanger 8.

During all of our laboratory tests, the temperature of the heat transfer fluid 5 did not drop to 85 ° C until after 200 cycles, this being due to the fact that the heat transfer fluid circuit 5 ended up in a closed circuit, and that all the stainless steel metallic elements, namely the tank, the heat exchanger and the return pipe if necessary, are enclosed in rock wool.

In addition, during these tests, it appeared that the amount of heat transfer fluid 5 of tank 1 is a function of the flow rate of the pump 7 while the fuel flow rate 14 is a function of the consumption of the burner. For burners with a capacity of more than 100 kW, the increase in our appliance will only be 10 to 15% more.

On the basis of these tests, we can affirm that the polluting gases released during different tests, have already reduced by a minimum of 30%, these 30% not having been consumed, therefore, no pollution rejected. As for the 70% consumed with a hot fuel, and which burned better than a cold fuel, the pollution generated is added to the 30%.

Therefore, we are assured that the heat transfer fluid 5 for example in the tests of demineralized water being at 90 ° C, flowing in channels whose capacity is double that of the fuel, the latter, at the outlet of the heat exchanger is 90 ° C.

As we have built our prototype, very small, and weighing no more than 6 kg, this device is capable of heating the fuel oil of a burner reaching 100 kW.

We have thus produced a device combining a space-saving volume, of a very light weight, which can be easily handled by a person skilled in the art. It has the additional advantage of being easy to manufacture which allows a very low price and makes our system easily marketable and cost-saving unbeatable.

It should be noted that the electrical elements allow a very low energy expenditure, if one takes into account a resistor 2 which rarely comes back into service, and a pump 7 of 60 Watts / hour, operating only with the burner operating time, approximately 3 minutes.

Our system is not only a fuel saver, but above all a leading pollution control device, capable of rendering very great services to the entire planet.

Because consumption is very significantly reduced, the impact on the environment becomes very significant.

Claims (11)

1. Heat exchange system (100) comprising: a first circuit (15) for the circulation of a fuel (14); a second circuit (10) for the circulation of a heat transfer fluid (5); a heat exchanger (8) allowing the heat exchange between the fuel (14) and the heat transfer fluid (5); characterized in that the heat exchanger (8) comprises a succession of plates (18) delimiting two by two of the channels (28, 29), in that the heat exchanger (8) comprises a first inlet (12) and a first outlet (13) for the first circuit (15) so that a part (29) of said channels (28, 29) forms a part of the first circuit (15), in that the heat exchanger comprises a second inlet ( 21) and a second outlet (22) for the second circuit (10) so that the remaining part (28) of said channels (28, 29) forms part of the second circuit (10) and in that the channels of the first circuit (29) and the second circuit (28) are alternated when following the succession of plates. 2. heat exchange system (100) according to the preceding claim characterized in that the plates (18) are arranged so that hg = t x hc, where: - hc is a height of the channels of the first circuit (15); - hg is a height of the channels of the second circuit (10); -1 is between 1.8 and 2.5. 3. Heat exchange system (100) according to claim 1 or 2, characterized in that the heat exchanger (8) of substantially parallelepiped shape comprises a first side (30) provided with the first outlet (13) and the second inlet (21) and a second side (31) provided with the first inlet (12) and the second outlet (22) so that in the heat exchanger, the directions of circulation of the first circuit (15) and of the second circuit (10) are opposite. 4. Heat exchange system (100) according to one of the preceding claims, characterized in that the heat transfer fluid (5) comprises ethylene glycol or demineralized water with alcohol. 5. Heat exchange system (100) according to one of the preceding claims, characterized in that the fuel (14) is chosen from one of the following liquids: oil, fuel, fuel oil, diesel or diesel. 6. heat exchange system (100) according to one of the preceding claims, characterized in that the second circuit (10) comprises a storage tank (1) with heat transfer fluid (5) and a pump (7) disposed between the storage tank (1) and the heat exchanger (8) to circulate the heat transfer fluid (5) there. 7. Heat exchange system (100) according to the preceding claim, characterized in that it comprises a heating resistor (2) disposed in the storage tank (1) for heating the heat transfer fluid (5). 8. Heat exchange system (100) according to the preceding claim, characterized in that the heating resistor (2) and the pump (7) are configured so that the temperature of the fuel (14) at the level of the first outlet ( 13) is between 85 ° C and 90 ° C. 9. heat exchange system (100) according to one of claims 6 to 8, characterized in that the pump (7) is configured so that in the heat exchanger (8), the flow of the heat transfer fluid (5 ) or at least 100 times that of the fuel (14). 10. Heat exchange system (100) according to one of claims 6 to 9, characterized in that it comprises a housing (20) containing the heat exchanger (8) and the two circuits (15, 10) and in that it comprises rock wool disposed in the housing (20) around the heat exchanger (8) and the storage tank (1). 11. Boiler (300) comprising: a combustion chamber (204), 5 - a nozzle (201) for bringing a fuel (14) into the combustion chamber (204), a burner (202) connected upstream of the nozzle (201), the burner being provided with a fan (203), said fan (203) being supplied by an electrical connection (24) and 10 -a heat exchange system (100) according to one of claims 6 to 10, characterized in that the first circuit (15) of the heat exchange system being connected upstream of the nozzle (201), the pump (7) is connected to the electrical connection (24) of the fan (203) so that pump 15 (7) operates in synchronization with the cycles of the boiler (200).