FR2930021A1 - Heat exchanger i.e. radiator, for heating, ventilation and/or air-conditioning system of motor vehicle, has dissipation unit for dissipating heat produced by metastable solution, where air flow is passed through dissipation unit - Google Patents

Abstract

The exchanger has a dissipation unit (8) formed by fins for dissipating heat produced by a metastable solution (S) e.g. acetic acid solution of sodium salt, where an air flow is passed through the dissipation unit. The solution is housed inside a storage unit (9) and contains ethylene glycol and gelling agent. The storage unit is formed by plates (12, 13) and a closing plate (14). An activation unit e.g. electrical discharge or micro-vibration unit, provokes exothermic reaction of the solution. Engine coolant (11) regenerates the solution.

Description

Heat exchanger comprising a metastable solution.

The invention relates to the field of ventilation systems, heating and / or air conditioning of motor vehicles and in particular to heat exchangers.

The evolution of vehicles with high-performance and / or hybrid thermal engines allows reductions in fuel consumption. In return, the heat losses of these engines are becoming weaker.

However, these heat losses are transmitted via the engine cooling circuit to a heat exchanger of the ventilation system, heating and / or air conditioning to provide heating of the cabin air. These thermal losses of the engine are therefore necessary to heat the air of the passenger compartment of the vehicle. During a cold start of the engine, these thermal losses are not sufficient to ensure proper heating in the first moments of operation of the ventilation system, heating and / or air conditioning. This disadvantage is even more pronounced during winter periods, the thermal losses of the engine being less for a cold start. To date, several additional heating solutions are known to overcome this lack of thermal loss by the motor, but each have disadvantages.

First of all, there are solutions which consume a great deal of electrical energy, such as an electric radiator comprising stones with a positive temperature coefficient or an immersion heater, ie an electrical resistance that exchanges heat with heat. the water. For hybrid vehicles for example, the reserve of electrical energy is limited. The use of such solutions is therefore not satisfactory since they require a large amount of electrical energy. In addition, these solutions are expensive because of the use, for example, stones with positive temperature coefficient.

There are also fuel-consuming solutions such as a burner on the water or on the air or the operation of the air conditioning loop in heat pump mode. As car manufacturers seek to drastically reduce the fuel consumption of vehicles, this type of solution is not suitable.

The recovery of heat losses, either at the exhaust via a water / gas exchanger, or with the aid of a viscocoupler arranged in the engine compartment and heating the engine oil by shear, is also an additional heating solution. Nevertheless, these solutions are not effective during the first moments of operation of the vehicle and especially during winter periods. Indeed, the exhaust gas when starting the vehicle out of the vehicle at a temperature too low to be able to recover thermal energy or the oil does not heat up sufficiently when starting the vehicle.

Finally, a hot water storage bottle can be an additional heating solution. However, this type of bottle is bulky, heavy, expensive and has a limited life. This solution is not suitable for smaller and smaller vehicles.

In summary, these various solutions sounds: expensive and / or bulky and / or consuming electrical energy and / or unsuitable when starting the vehicle.

The invention overcomes these difficulties by a heat exchanger comprising at least one heating means and at least one means for dissipating the heat produced by the heating means, said dissipation means being able to be traversed by a flow of heat. air. The heating means is a metastable solution generating heat.

Metastable heat-generating solution is understood to mean any saturated aqueous solution of salt and in a supercooled state, the supercooling state being a liquid state at a temperature below the melting temperature.

The use of a heat-generating metastable solution as a heating means has the advantage of releasing the heat necessary for heating the air of the passenger compartment without resorting to a high consumption of energy. Indeed, it suffices for a simple electric shock or a micro-vibration to initiate the exothermic reaction of the metastable solution. In addition, this type of metastable solution is inexpensive. Finally, the amount of metastable solution required for additional heating at least equivalent to the known solutions does not generate a large footprint.

Additional or optional features of the invention are set forth below.

the heat-generating solution is a solution of acetic acid of sodium salt. the heat generating solution comprises ethylene glycol.

the metastable heat generating solution comprises a gelling agent.

the heat exchanger comprises an activation means for causing an exothermic reaction of the heat generating solution.

the activation means is an electric discharge.

an electrical type device generates the electric discharge. the activation means is a micro vibration. a device of the mechanical type generates the micro vibration.

the metastable heat generating solution is housed inside at least one storage means.

the storage means and the dissipation means are in contact and arranged parallel to each other in a beam-forming manner.

The heat exchanger comprises at least one means for regenerating the metastable solution.

- The regeneration means is a coolant of an engine of a motor vehicle. the heat exchanger comprises at least one means for circulating the engine coolant inside the heat exchanger, said circulation means being in contact with the storage means.

The circulation means, the storage means and the dissipation means are arranged parallel to one another so as to form a bundle.

- The circulation means is disposed perpendicularly to the storage means 25 and the dissipation means.

the regeneration means is at least one electrical resistance.

the electrical resistance is located inside the storage means. The invention also relates to a ventilation, heating and / or air conditioning system comprising at least one heat exchanger according to one of the preceding characteristics.

According to another characteristic, the ventilation system, heating and / or air conditioning, comprises a heat exchanger according to the invention located downstream with respect to a radiator traversed by the coolant of the engine of the vehicle.

Other features, details and advantages of the invention will emerge more clearly on reading the description given below as an indication in relation to drawings in which: FIG. 1 is a perspective view of a heat exchanger; According to the invention, FIG. 2 is a fragmentary sectional view showing in particular the structure of the heat exchanger bundle according to the invention. FIG. 3 is a view of a second embodiment of the invention. FIG. 4 is a side view of a plate constituting the beam of the second embodiment, FIG. 5 is a view of a third embodiment of the invention, FIG. perspective view of a tubular of the third embodiment, - Figure 6 is a partial view of the fourth embodiment of the invention, - Figures 7 and 8 illustrate a mechanical type device causing a micro-vibration, and - the fig Figure 9 shows an electrical type device causing an electric discharge.

Figure 1 shows a first embodiment of the invention. A heat exchanger 1, here a radiator for a ventilation system, heating and / or air conditioning not shown, comprises two water boxes 2, 3 each provided with an opening 4, 5. Between the first water box 2 and the second water box 3 is a bundle 6 consisting in part of tubes 7. The beam means the part of the heat exchanger 1 free of water box. Each tube 7 is fluidly connected to the two water boxes 2, 3 so that a coolant 11 of an engine of a vehicle entering the heat exchanger 1 via the opening 4 of the first water box 2 circulates in it and reaches the second water box 3. Thus, each tube 7 forms a circulation means 10 of the coolant 11. The coolant 11 exits the heat exchanger 1 via the opening 5 of the second water box. Thus, the heat exchanger has a liquid flow I. The flow direction of the cooling liquid is symbolized by arrows in FIG. 1. A dissipation means 8, ensuring the exchange of heat between the calories supplied by the coolant and a flow of air passing through the heat exchanger. heat is located between the tubes 7 of the beam 6. This dissipation means 8 is formed by fins. The heat exchanger 1 also comprises at least one heating means and at least one storage means 9. The heating means is a heat-generating metastable solution S. The latter S is housed in the storage means 9. The beam 6 comprises, as illustrated in FIG. 1, a plurality of storage means 9, dissipation means 8 and circulation means 10. The storage means 9 according to this embodiment is a closed envelope containing the metastable solution S. This envelope constitutes a reservoir for the heat generating metastable solution S. Each envelope is in contact with a tube 7 and a dissipation means 8. In other words, each storage means 9 is in contact with a dissipation means 8 and a circulation means 10.

According to this embodiment, the circulation means 10, the storage means 9, the circulation means 10 and the dissipation means 8 are arranged parallel to one another so as to form the bundle 6. The water boxes 2, 3 are arranged perpendicular to the storage means 9 and cover the beam 6 at two opposite ends. This particular arrangement of the beam 6 ensures efficient regeneration because the contact surface between the storage means 9 and the circulation means 10 is important. Indeed, since the cooling liquid 11 passing through the circulation means 10 is here a regeneration means 18 of the heat generating metastable solution S and that the circulation means 10 and the storage means 9 are contiguous to each other. According to their length, the contact surface and therefore the heat exchange surface between the storage means 9 and the circulation means 10 is optimal.

FIG. 2 shows in more detail the arrangement of the beam 6. The beam 6 is constituted by a repetition of a circulation means 10, a storage means 9 and a dissipation means 8. A first plate 12 and a second plate 13 are contiguous to each other to form the tube 7.

Each plate 12, 13 is made of metal, such as aluminum, and comprises a stamping and / or a stamping which forms part of the tube 7. The storage means 9 is formed by the first plate 12 and a closure plate 14 The closure plate 14 differs from the first plate 12 in that it completely seals the stamping of the first plate 12. Thus, when the first plate 12 and the closure plate 14 are contiguous to each other , the stamping delimits an envelope in which the metastable solution S is housed. The metastable solution S does not circulate inside the heat exchanger 1. The dissipation means 8 is in contact with the closure plate 14. The assembly formed by the first plate 12, the second plate 13, the closure plate 14 and the fin 8 constitutes a first series which is repeated to form the beam 6 of the heat exchanger.

Below is described the mode of operation of such a heat exchanger. During the cold start of the motor vehicle, the engine does not provide enough calories via the coolant to the radiator, that is to say the heat exchanger, if a passenger wishes to heat the air of the cabin from the first moments of operation ciu vehicle. In this case, the calories needed to heat the cabin air are provided by the metastable solution via an exothermic reaction.

The exothermic reaction is initiated by a disturbance caused by an activation means 15. This disturbance causes solidification of the metastable solution. When changing the liquid-solid state of the metastable solution, a release of heat occurs: this is the exothermic reaction. This amount of heat is then transmitted to the dissipation means 8 which exchanges this quantity of heat with a flux of ai passing through the beam 6.

The disturbance is of the electric or recanic type. An electrical disturbance is for example an electric discharge 16 formed in the storage means.

A mechanical disturbance is for example a micro-vibration 17. Exemplary embodiments of these disturbances will be described later. Once the metastable solution is completely solidified, the exothermic reaction is complete.

The exothermic reaction of this solution being a reversible reaction, the solution remains in the solid state until a regeneration step. This regeneration step is caused just as the disturbance initiating the exothermic reaction. To regenerate the solution in the solid state, an endothermic reaction must be performed. In other words, a quantity of heat must be added to the solution in the solid state so that it changes state and becomes liquid again.

During the few minutes of the exothermic reaction, the engine warms up and begins to provide enough calories to the coolant passing through it for these calories to be used to increase the temperature of the air passing through the beam 6 of the heat exchanger. heat 1. As a result, the calories transported by the coolant from the hot engine take over to heat the air passing through the beam and / or to provide the amount of heat required for the endothermic reaction. of the metastable solution. Thus, the metastable solution passes from a solid state to a liquid state and is again able to provide heat by a new exothermic reaction. In other words, the regenerated metastable solution is able to provide additional heating again. According to the first embodiment, the regeneration means 18 of the metastable solution S is the coolant 11.

The reversibility of the exothermic and endothermic reactions of the metastable solution coupled with the supply of calories provided by the engine via the coolant has the great advantage of having a heat source available from the start of the vehicle even in the winter and from require no means of regeneration other than the engine coolant to regenerate the metastable solution after solidification.

Compared to a radiator provided with elements with a positive temperature coefficient, such a heat exchanger thus has the advantage of requiring only a very small amount of electrical energy for its operation because a simple electric shock and / or a micro-vibration activates the exothermic reaction and only the thermal energy lost by the engine regenerates the metastable solution.

In Figures 3 and 4 is illustrated a second embodiment. In FIG. 3, a heat exchanger 101 comprising storage means 9 and dissipation means 8 is shown. The beam 106 of the heat exchanger 101 consists of an alternation of a storage means 9 and a dissipation means 8. Each storage means 9 comprises two identical plates 120 contiguous to each other to form a reservoir housing the metastable solution S. A side view of a plate 120 is in Figure 4. The plate 120 has at each of its ends an orifice 121. The orifices 121 of a plate 120 do not communicate: not fluidly with the reservoir containing the metastable solution S. When the beam 106 is formed, the set of upper orifices 121a and the set of lower orifices 121b are respectively aligned. A first duct 122 is housed inside the upper openings 121a and conveys the engine coolant 11 inside the heat exchanger 101. A second duct 123 is housed inside the set of orifices. 121b and discharges the engine coolant 11 out of the heat exchanger 101.

The heat exchanger 101 according to FIGS. 3 and 4 does not have in its bundle 106 of tubes 7 arranged parallel to the dissipation means 8. The storage means 9 and the dissipation means 8 are arranged parallel to one another in order to form the beam 106. In addition, the circulation means 10 is arranged perpendicular to the storage means 9 and the dissipation means 8. Indeed, such a heat exchanger 101 is intended to replace an electric heater, housed in a ventilation system, heating and / or air conditioning and having elements with a positive temperature coefficient, placed upstream or downstream of a heat exchanger receiving only the coolant 11. The terms upstream and downstream are relative to the direction of flow of air through the ventilation system, heating and / or air conditioning.

In Figure 5 is shown a third embodiment. A heat exchanger 201 comprises a beam 206 disposed between two uprights 230. The beam 206 comprises an alternation of dissipation means 8 and storage means 9. According to this embodiment, the storage means 9 is formed by a tubing 235 containing the metastable solution S. This tubing is shown in FIG. 5a and comprises a cylindrical wall 236 and two lateral faces 237 located at the end of the cylindrical wall 236. A regeneration means 18 in the form of an electrical resistance 231 is housed in each storage means 9 and in contact with the metastable solution S. The electrical resistance 231 traverses longitudinally the tube 235. Thus, the heat exchanger 206 comprises a plurality of electrical resistance 231 forming part of an electrical circuit 232 passing through each means storage 9.

The electrical circuit 232 is connected to the electrical network of the vehicle. The electrical circuit 232 comprises a first fill 233 housed inside a first post 230a. This first wire 233 has an end protruding from the first upright 233 for connection to the vehicle electrical network. The electrical resistors 232 are connected in parallel to the first wire 233. A second wire 234 is housed in a second post 230b and has a projecting end of the second post 230b for connection to the vehicle electrical network. The electrical resistors 231 are connected in parallel to this second wire 234. The connection between the electrical resistors 231 and the first 233 and second 234 son is made completely leakproof. In other words, the connection between the electrical resistors 231 and the first 233 and second 234 son being made at the side faces 237 of the tubes 235, the tubes 235 comprises sealing means so that no leak of Metastable solution S is not possible at the side faces 237.

The electrical resistors 231 equipping the heat exchanger have the advantage of being low energy consumers to regenerate the metastable solution S in the solid state unlike elements with positive temperature coefficient.

In addition, such a heat exchanger 206 according to this embodiment is placed downstream of a heat exchanger fed only by the coolant 11 of the vehicle engine in a ventilation system, heating and / or air conditioning. As a result, when the calories supplied by the coolant 11 are large enough to heat the flow of air passing through the heat exchanger supplied by the coolant 11, the heat exchanger 206 according to the invention receives a heated air flow and the metastable solution in the solid state is then regenerated. The combination of the calories provided by the flow of air heated by the coolant and the calories provided by the electric resistors 231 ensures a low power consumption for the regeneration of the metastable solution S.

The particular arrangement of the electrical resistors 231 inside the tubes 235 ensures homogeneity of temperature during the regeneration of the metastable solution S. In fact, each electrical resistance 231 extending along the length of the tubing 235, a gradient of homogeneous temperature is obtained, thus improving the quality of the regeneration.

In Figure 6 is shown a fourth embodiment. A heat exchanger 301 shown partially comprises a beam 306 composed of an alternation of dissipation means 8 and storage means 9. The storage means 9 is a pipe 335 comprising a cylindrical wall 336 in contact with the dissipation means 8 and two side faces 337. Each side face 337 is open and in fluid communication with a channel 338.

Thus, the beam 306 is bordered at two opposite ends by two channels 338. Specifically, the channels 338 are arranged perpendicularly to the tubes 335. The fluid communication between the tubes 335 and the channels 338 imply that the metastable solution S is contained in FIG. both in tubings and channels. The storage means 9 is therefore formed by the two channels 338 and the tubes 335. In addition, each channel 338 houses an electrical resistance 331. This electrical resistance 331 extends along the length of the channel 338 and is in contact with the solution. metastable S. The electric resistors 331 are connected to the vehicle electrical network. According to this embodiment, only two electrical resistors are used for the regeneration of the metastable solution S. In fact, the regeneration is initialized in the two channels 338 and then is done by heat transfer step by step in the metastable solution and propagates in the tubes 335. This embodiment is then less electrical energy consumer vis-à-vis the third embodiment.

According to an alternative embodiment, the storage means 9 and the channels 338 are made by a stack of plates.

The features below are applicable to all the embodiments described above.

Each embodiment described above comprises at least one activation means 15. FIGS. 7 and 8 show a first example of activation means 15 according to the embodiment of FIG. 3. The activation means 15 is here a micro-vibration. The micro-vibration is performed by a device of mechanical type comprising a magnet 151, a pusher 152, a spring 153 and a coil 154. A housing 155 houses the magnet 151, the pusher 152, the spring 153 and the coil 154. The housing 155 is disposed in the heat exchanger 1 so as to be in contact with a storage means 9. The magnet 151 is movable in translation inside the coil 154 along an axis A of the magnet 151 .

When no electric current passes through the coil 154, the magnet is in a first position P1 in which the pusher 152, fixed to the magnet 151 and extending along the axis A, does not project internally. storage means 9. In this first position P1, the pusher is fully housed inside the housing 155 and is held in position by the spring 153 fixed on one side to the magnet 151 and a Another side to the housing 155. The force exerted by the spring 153 on the magnet 151 prevents the pusher 152 from penetrating inside the storage means 9. When an electric current passes through the coil 154, a magnetic field is created and the magnetic field creates a force opposite to that of the spring 153 and allows the pusher 152 to penetrate inside the storage means via an orifice 91 formed on the storage means 9 for the passage of the pushbutton 152. The pusher 152 is then in a second position P2 in which it causes the activation of the exothermic reaction of the solution S contained in the storage means 9. When the pusher 152 penetrates inside the storage means 9, it comes into contact with the solution S and causes a micro-vibration 17 which initiates the exothermic reaction of the solution S. When the coil is no longer supplied with electric current, only the force of the spring 152 continues to be exerted on the magnet 151 and thus, the pusher returns to his first position. The micro-vibration 17 is therefore achieved via the pusher 152 which acts as a striker under the effect of the magnetic field created by the coil 154.

Since each storage means 9 of the heat exchanger 1 according to the embodiment of Figure 3 is independent, that is to say that the solution contained in a storage means 9 is enclosed in the latter and does not communicate fluidly with the solution of another storage means 9, each storage means 9 is provided with an activation means 15.

A second example of activation means 15 is illustrated in FIG. 9. Here, the activation means 15 is an electric discharge. The electric discharge is performed by an electrical type device comprising two electrodes 156 housed in a housing 155. The two electrodes 156 are connected to an electronic circuit 157 itself connected to the vehicle electrical network. An orifice 91 formed on the storage means 9 makes it possible to insert the two electrodes 157 inside the latter. Thus, the two electrodes 157 are immersed in the solution S contained in the storage means 9. When a current flows through the electronic circuit 157, an electric discharge 16 is created between the two electrodes 157 and initiates the exothermic reaction of the solution S .

The heating means according to the invention is a metastable solution S. Such a solution is for example a solution of sodium acetate (NaC2H3O2). More precisely, the metastable solution S is a solution of acetic acid of sodium salt. The advantage of using such a solution as heating means is due to the intrinsic characteristics of the latter. For example, this solution does not damage copper or its alloys, stainless steel or plastics. Thus, the storage means 9 can be made with these inexpensive materials. In addition, this solution is non-flammable which implies that it is not necessary to provide the heat exchanger of a control means of the heating means for the risk of fire.

According to another variant, the metastable solution S is of the following chemical composition: KAI (SO4) 2 -12H2O, or NH4Al (SO4) 2 -12H2O, or (NH4) Al (SO4) -6H2O. The chemical composition of the Metastable solution S is chosen so that the melting point of the solution, i.e. the temperature of the liquid-solid state change, is greater than or equal to 50 ° C.

The exothermic reaction of a sodium acetate solution is triggered by a controllable physical phenomenon (electric discharge 16 or micro-vibration 17) by means of a device of mechanical or electrical type, the additional heating provided by the Heat exchanger 1 is available at any time. The use of a sodium acetate solution as a heating medium is inexpensive.

As a variant, the metastable solution S comprises a component making it possible to lower the solidification temperature so that the metastable solution S remains in the liquid state during winter periods in which the temperature outside the vehicle can reach -20 ° C. for example . Since the metastable solution S must be in the liquid state to be activated and provide heat by passing to the solid state, it is necessary for use of such a solution in a motor vehicle that this solution remains in the liquid state despite very low outside temperatures. Thus, the metastable solution S comprises ethylene glycol (C2H6O2) to reduce the liquid-solid state change temperature. In other words, ethylene glycol makes it possible to lower the melting point of the metastable solution S.

In addition to ethylene glycol, the metastable solution S optionally comprises an additive, such as a gelling agent. This gelling agent ensures a better stability of the metastable solution S, thus avoiding inadvertent triggering of the exothermic reaction. The gelling agent also provides an improvement in the life of the heat exchanger. Indeed, when the metastable solution S changes from the liquid state to the solid state, it exerts a greater mechanical stress on the walls of the storage means 9 due to the change of state.

The presence of the gelling agent makes it possible to reduce the intensity of this mechanical stress exerted by the metastable solution S on the storage means 9 by rendering the metastable solution S viscous during its passage in the solid state. In addition, this gelling agent enhances the temperature level reached by the exothermic reaction and increases the time of the exothermic reaction. The calories then transmitted to the air passing through the heat exchanger are in a higher quantity and this transmission lasts longer. Such a gelling agent is, for example, corn starch or aniline.

As a variant of the first embodiment, the heat exchanger comprises a single water box. In this case, the constituent plates of the bundle are shaped so as to ensure a circulation in U of the coolant 11. In addition, the heat exchanger according to the invention has two, three, four, five or six passes according to the conformation of the plates forming the beam.

Claims (3)

1. heat exchanger (1) comprising at least one heating means and at least one means for dissipating (8) the heat produced by the heating means, said dissipation means (8) being able to be traversed by a flow of air, characterized in that said heating means is a metastable solution (S) generating heat. 2. heat exchanger (1) according to claim 1, wherein the metastable solution (S) generating heat is a solution of acetic acid of sodium salt. 3. heat exchanger (1) according to claim 1 or 2, wherein the metastable solution (S) generating heat comprises ethylene glycol. 4_ heat exchanger (1) according to any one of the preceding claims, wherein the metastable solution (S) generating heat comprises a gelling agent. The heat exchanger (1) according to any one of the preceding claims, wherein it comprises an activating means (15) for causing an exothermic reaction of the heat generating metastable solution (S). The heat exchanger (1) according to claim 5, wherein the activating means (15) is an electric discharge (16). The heat exchanger (1) according to claim 6, wherein an electrical type device generates the electric discharge (16) .sub.20. The heat exchanger (1) according to claim 5, wherein the activation means (15) is a micro vibration (17). 9, heat exchanger (1) according to claim 8, wherein a mechanical type device generates the micro vibration (17). 10.Echangeur heat (1) according to any preceding claim, wherein the metastable solution (S) generating heat is housed inside at least one storage means (9). 11. heat exchanger (1) according to claim 10, wherein the storage means (9) and the dissipating means (8) are in contact and arranged parallel to each other so as to form a beam (6). 12.Echangeur heat (1) according to any preceding claim, wherein it comprises at least one regeneration means (18) of the metastable solution (S). The heat exchanger (1) according to claim 12, wherein the regeneration means (18) is a coolant (11) of an engine of a motor vehicle. 14. The heat exchanger (1) according to claims 10 and 13, wherein it comprises at least one means (10) for circulating the coolant (11) of the engine inside the heat exchanger (1). ), said circulation means (10) being in contact with the storage means (9). The heat exchanger (1) according to claim 14, wherein the circulation means (10), the storage means (9) and the dissipation means (8) are arranged parallel to one another The heat exchanger (1) according to claim 14, wherein the circulation means (10) is arranged perpendicular to the storage means (9) and the dissipation means (8). . 17. Heat exchanger (1) according to claim 12, wherein the regeneration means (18) is at least one electrical resistance. 18, heat exchanger (1) according to claims 10 and 17, wherein the electrical resistance is within the storage means (9). 19. A ventilation, heating and / or air conditioning system comprising at least one heat exchanger (1) according to one of the preceding claims. 20. Ventilation, heating and / or air conditioning system according to claim 19, wherein the heat exchanger (1) is located downstream with respect to a radiator traversed by the coolant (11) of the vehicle engine. 25