FR2823498A1 - Thermal management of reformer for production of fuel for fuel cell of electrically propelled motor vehicle comprises obtaining energy from condensation of refrigerant fluid - Google Patents

Abstract

The thermal management of a reformer (1), for the production of a fuel for a fuel cell (P) of a electrically propelled motor vehicle (V), able to obtain calorific energy as a function of the calorific needs of the reformer comprises producing at least a part of this energy by the condensation of a refrigerant fluid. Independent claims are also included for the following: (a) a device for the thermal management of a reformer for the production of fuel for a fuel cell; and (b) a vehicle incorporating a reformer using this device for its thermal management.

Description

The invention relates to a process for thermal management of a reformer of

  production of a fuel intended for a fuel cell of an electrically propelled motor vehicle, said method being capable of supplying energy

  calorific according to the calorific needs of said reformer.

  Conventionally, a reformer produces a fuel, for example hydrogen, from a fuel such as, for example, propane, butane, methanol, petrol, diesel, kerosene or so on. . However, the reformer does not operate correctly when its temperature leaves a determined operating range. However, the chemical reactions leading, from fuel and air, to the production of the fuel do not always alone enable the temperature of the reformer to be maintained within this operating range. The reformer must then receive thermal energy, in the form of heat energy or energy

  from an outside source.

  Document EP 1014464 A2 describes a device in which a gaseous mixture of fuel and water vapor intended for the reformer is previously reheated to a predetermined temperature by a burner before being injected into the reformer. Reforming this heated mixture leads to the desired temperature

in the reformer.

  When the vehicle is started cold, the reformer however rises slowly in temperature, the duration of temperature rise being conventionally of the order of fifteen minutes. During this phase, the reformer cannot function satisfactorily, which is the source of additional gas pollution and

  poor energy efficiency.

  In addition, the device described in EP 1014464 A2 does not make it possible to cool the

  reformer. It is therefore not suitable for exothermic reformers.

  The object of the invention is to provide a process for thermal management of a reformer which makes it possible to accelerate the heating of the reformer, in particular during the

  cold start, and which is also suitable for cooling the reformer.

  This object is achieved by a thermal management method of a reformer for producing a fuel intended for a fuel cell of an electrically propelled motor vehicle, said method being capable of supplying heat energy by function of the calorific needs of said reformer, remarkable in that it consists in producing at least part of said calorific energy by

  condensation of a refrigerant.

  According to other characteristics of the process according to the invention, - in the event of the refrigeration requirements of said reformer, refrigeration energy is produced by evaporation of said refrigerant, then at least part of said refrigeration energy is transferred to said reformer, - the amount of said condensed or evaporated refrigerant is adjusted to fix the amount of heat or cooling energy, respectively, transferred to said reformer. Thanks to these characteristics, it is possible to supply heat energy which may possibly complement that provided by the burner during cold starting. The method according to the invention is also capable of supplying cooling energy to the reformer, and therefore usable for exothermic reformers. The invention also relates to a device for managing the temperature of a reformer for producing a fuel intended for a fuel cell of an electrically propelled motor vehicle, said device being capable of supplying heat energy as a function the heat requirements of said reformer, remarkable in that it comprises a refrigerant circuit in which a refrigerant circulates, said refrigerant circuit comprising at least one compressor, a first exchanger in heat transfer relation with said reformer, an expansion means and a second exchanger, said refrigerant circuit being arranged so that said refrigerant condenses in said first exchanger producing at least one

  part of said heat energy, and evaporates in said second exchanger.

  According to other optional characteristics of the device according to the invention, - said refrigerant circuit includes a common branch at medium pressure connected, by means of expansion branches on which are inserted expansion means, to first inputs of at least two exchangers of said refrigerant circuit, a common low pressure branch connected to the suction of a compressor and, by means of low pressure branches, to second inputs of said exchangers, and a common high pressure branch connected to the outlet of said compressor and, via high pressure branches, also connected to said second inlets, said refrigerant circuit further comprising means for adjusting the flow rate of said refrigerant in 1: said expansion branches, at high , and at low pressures, and an electronic control unit controlling said adjustment means so that, depending on their positions, the refrigerant passing through an exchanger comes from said high-pressure branch or from said medium-pressure branch and condenses or evaporates therein producing calories or frigories, respectively, said adjustment means of the flow rate of said refrigerant include high pressure valves and low pressure valves inserted into said high and low pressure branches, respectively, - the degree of opening of said high and low pressure valves is continuously adjustable, - said means for adjusting the flow rate of said refrigerant comprise at least one three-way valve inserted at a junction between a high-pressure branch, a low-pressure branch and a first inlet of a heat exchanger, the said means for adjusting the flow of said fluid refrigerant comprises a compressor with continuously adjustable flow, said means for adjusting the flow of said refrigerant include expansion means with continuously variable flow, - said refrigerant circuit includes a main loop in which are inserted in series said first exchanger, expansion means, said second exchanger and a four-way valve, said four-way valve being also inserted in a reversing loop in which the compressor led is inserted, the position of said four-way valve determining the direction of circulation of said refrigerant in said main loop, and thus the function of condenser or

evaporator of said exchangers.

  The invention finally relates to a vehicle comprising a reformer, remarkable in that this vehicle further comprises a device for thermal management of said reformer in accordance with the present invention, or in that the temperature of said reformer is managed according to a process in accordance with the present invention. Other characteristics of the invention will appear on reading the

  description which follows and on examination of the appended drawings in which:

  - Figure 1 schematically shows the preferred embodiment of the device according to the invention;

......

  - - Figure 2 schematically shows another embodiment of the device

according to the invention ;.

  - Figures 3 and 4 schematically represent two variants of the device illustrated

in figure 1.

  Identical ratings have been given to bodies fulfilling roles

analogs in different figures.

  An electrically propelled motor vehicle V (FIG. 1) incorporates a reformer 1 intended to supply fuel to a fuel cell P. via a line C. The temperature of the reformer 1 is kept within an appropriate range by means a primary refrigerant circuit, generally referenced by 15, traversed by a primary refrigerant and comprising a first exchanger 2 'in heat transfer relation with the reformer 1 and an external exchanger 2: in heat transfer relation with the outside of the vehicle V. The first inputs of the exchangers 2. and 22 are connected to a common medium-pressure branch 28, denoted "MP", by means of expansion branches, 29, and 292 respectively, on which regulators 30 are inserted. , and

302, respectively.

  In the example of a device illustrated in FIG. 1, the regulators 30, and 30: could be replaced by a single regulator, but so that the primary circuit can be used to manage the temperature of other organs than the reformer 1, it it is preferable to provide one regulator per exchanger. The meaning of this remark

  will appear more clearly when describing FIG. 3.

  The second inputs of exchangers 2, and 2: are connected to a common high-pressure branch 32, denoted "HP", by means of high-pressure branches, 34, and 342 respectively, on which high-pressure valves are inserted.

  pressure, 36, and 362 respectively, preferably with continuously adjustable flow.

  On the other hand, the second inputs of the exchangers 2, and 22 are connected to a common low pressure branch 38, denoted "BP", by means of low pressure branches, 40, and 402 respectively, on which are inserted. low pressure valves, 42, and 422 respectively, preferably with continuously adjustable flow. High, medium and low pressures have values depending on the nature

refrigerant.

  A compression branch 44 connecting the common branches at low and high pressures, 38 and 32 respectively, incorporates a primary compressor 46,

  preferably with continuously adjustable flow.

  An electronic control unit 47 controls the high pressure valves 36, and 362 via electrical lines 48, and 482, respectively, controls the low pressure valves 42, and 422 via electrical lines 50, and 502, respectively, as well as the primary compressor 46, by

  through a power line 52.

  A temperature sensor 54 measures the temperature of the reformer 1 and informs it, via an electric line 56, of the control unit

electronics 47.

  The operation of the device shown diagrammatically in FIG. 1 is described below. The electronic control unit 47 compares the actual temperature measured by the sensor 54 in the reformer 1 with the operating temperature range of the reformer 1, initially stored. It begins if the reformer 1 must be heated,

  cooled, or if it requires no additional intake of frigories or calories.

  In the operating example illustrated in FIG. 1, the reformer 1 must

to be reheated.

  The electronic control unit 47 controls the opening, denoted "O", of the high pressure valve 36, and of the low pressure valve 422, as well as the closing, denoted "F", of the low pressure valve 42, and the high pressure valve 362. The primary refrigerant coming from the common high pressure branch 32, in a thermodynamic condensable state, that is to say in an essentially gaseous form and at high pressure, passes through the exchanger 2, by condensing there, and therefore by producing calories at least partially transferred to the reformer 1. After expansion in the regulator 30 "it joins the common branch at medium pressure 28, then is relaxed at low pressure by the regulator 302.11 then enters, in an evaporable thermodynamic state, that is to say in an essentially liquid form at low pressure, into the external exchanger 22 o it evaporates producing frigories evacuated towards the outside of the vehicle V. A after evaporation, the primary refrigerant, in an essentially gaseous form and at low pressure, joins the common branch at low

  pressure 38 before being recompressed by the primary compressor 46.

  The compression of the primary refrigerant allows its reuse. It provides it with the energy transferred, in a calorific form, during condensation

in exchanger 2 ,.

  After compression, the primary refrigerant joins the common high-pressure branch 32. By reversing the position of the valves 36, 362, 40 "and 402, the electronic control unit 47 reverses the direction of circulation of the primary refrigerant in the circuit 15 and switches the roles of condenser or evaporator of the exchangers 2 'and 22, thus determining the heating or cooling of the reformer 1. The adjustment of the flow rates through the exchangers, by means of open valves and / or of the primary compressor 46 , allows the electronic control unit 47 to fix the

  amount of heat or cooling energy delivered to the reformer 1.

  To avoid mixing between primary refrigerants at high and low pressures, the electronic control unit 47 prevents simultaneous opening

  valves 36, and 362, as well as valves 40 ,, and 402.

  FIG. 2 illustrates another means of permuting the roles of the exchangers 2, and 22. The primary circuit 15 comprises a main loop 57a and an inversion loop 57b. The main loop 57a comprises a network of pipes 58 into which the heat exchanger 2, a pressure regulator 59, the external heat exchanger 22 and a four-way valve 60 are inserted in series. The four-way valve 60, controlled by the unit electronic control 47 via an electrical line 61, is also inserted in the reversing loop 57b comprising a network of pipes 64 in which the primary compressor 46 is inserted. The other members of FIG. 2

  are identical to those described above.

  A change in position of the four-way valve 60 changes the direction of circulation of the primary fluid in the exchangers 2 and 22, which reverses their respective thermal functions, the condenser becoming an evaporator and vice versa. By controlling the four-way valve 60, the electronic control unit 47 can thus cause heating or cooling of the reformer 1. FIG. 3 illustrates a variant of FIG. 1 in which a third exchanger 2a is inserted in the primary circuit 15 parallel to the other exchangers

2, and 22.

  -; The first inlet of the exchanger 23 is connected to the common medium-pressure branch 28 by means of an expansion branch 293 on which a regulator 303 is inserted. Its second inlet is connected on the one hand to the common branch at high pressure 32 via a high pressure branch 343 on which is inserted a high pressure valve 363, preferably with continuously adjustable flow rate, and on the other hand to the common low pressure branch 38 by l intermediate of a low pressure branch 403 on which a gate valve is inserted

  low pressure 423, preferably with continuously adjustable flow.

  The electronic control unit 47 controls the high pressure valve 363 via an electrical line 483 and the low pressure valve 423 through

  through a power line 50.

  The exchanger 23 is. for example, in relation to thermal transfer with the fuel cell P. the latter expressing to the electronic control unit 47,

  by means not shown, its thermal requirements.

  The operation of the device illustrated in Figure 3 is as follows.

  In the operating example illustrated in this figure, the reformer 1 must

  be heated and the fuel cell P must be cooled.

  To heat the reformer 1, the electronic control unit 47 proceeds by opening the high pressure valve 361 and closing the low pressure valve 42

  as explained in the description of Figure 1.

  To cool the fuel cell P. the electronic control unit 47 controls the closing of the high pressure valve 363 and the opening of the low pressure valve 423. The primary refrigerant coming from the common branch at medium pressure 28 is expanded at low pressure by the regulator 303 and then enters, in an evaporable thermodynamic state, that is to say in an essentially liquid form at low pressure, into the exchanger 2s where it evaporates producing frigories at least partly transferred to the fuel cell P. After evaporation, the primary refrigerant, in an essentially gaseous form and at low pressure, joins the common branch at low pressure 38 before being recompressed by the primary compressor 46 and join the

  high pressure common branch 32.

  By controlling the respective open or closed positions of the valves associated with an exchanger, the electronic control unit 47 therefore determines whether the primary refrigerant condenses or evaporates there, and thus heats or cools the consumer in transfer relationship. thermal with this exchanger. The adjustment of the flow rates through the exchangers, by means of the valves and / or of the primary compressor 46, allows the electronic control unit 47 to fix the amount of energy.

  heat or refrigeration thus delivered.

  11 clearly appears that the device makes it possible to manage, independently of each other, the temperatures of a plurality of consumers in heat transfer relation with exchangers inserted like exchangers 2, and 2, in the circuit 15. In particular, the vehicle interior air conditioner V can be connected to the primary circuit 15. The primary refrigerant circuit 15 can then result from a

  simple adaptation of the air conditioning circuit of this cabin.

  The electronic control unit 47 regulates the valves 362 and 42: controlling the operation of the condenser or evaporator of the external exchanger 2:, so that the energy received by the refrigerant through the compressor 46 and the exchangers of the circuit operating as an evaporator, here the exchanger 2s, being substantially equal to the energy supplied by the refrigerant through the exchangers of the circuit operating as a condenser. In the example illustrated in FIG. 3, it has been assumed that the electronic control unit 47 should thus transform the external exchanger 22 into a condenser by closing the low pressure valve

  42: and by opening the high pressure valve 36.

  The heat transfer relationship between the primary refrigerant and the reformer 1 can be established in different ways. For example, the reformer 1 can constitute the exchanger 2, itself or incorporate it into its structure, as

  shown schematically in Figures 1, 2 and 3.

  It can also, in an embodiment not shown, be in heat transfer relation with the exchanger 2, by means of a secondary circuit in which circulates a secondary heat-transfer fluid, for example air, l oil or water, this fluid receiving thermal energy through the exchanger 2, and transporting it to the reformer 1, which is useful for example in the event of an incompatibility between the fluid primary refrigerant and reformer 1 or if the architecture of the vehicle V does not allow the primary refrigerant circuit 15

to incorporate the reformer 1.

  The secondary circuit can be opened and the secondary fluid, for example

  the air, be evacuated outside the vehicle V after it has passed through the reformer 1.

  FIG. 4 illustrates a device comprising a secondary refrigerant circuit making it possible to condense or evaporate a secondary refrigerant fluid in an exchanger 21 in direct heat transfer relation with the reformer 1 according to the

thermal requirements of the latter.

  A secondary circuit 65 comprises a main loop 67 successively passing through the first exchanger 2 in direct heat transfer relation with the reformer 1, a four-way valve 69 for connection to an inversion loop 71, a second exchanger 72 called "intermediate" also crossed by the primary refrigerant, and a pressure reducing valve 73. The reversing loop 71 includes a

secondary compressor 75.

  When this is technically possible, the secondary fluid can advantageously be in direct contact with the reformer 1, the first exchanger 2 being eliminated. FIG. 4 illustrates a heating situation of the reformer 1. The secondary fluid, compressed at high pressure in the secondary compressor 75, enters the first exchanger 2, condenses there by releasing calories, then expands in the regulator 73 until low pressure, evaporates in the intermediate exchanger 72, then returns to the inlet of the secondary compressor 75 to be there

again compressed.

  The frigories produced by the evaporation of the secondary fluid in the intermediate exchanger 72 are partly recovered by the primary refrigerant, the latter

  condensing in this same exchanger.

  A change in position of the four-way valve 69 changes the direction of circulation of the secondary fluid in the secondary circuit 65, which reverses the respective thermal functions of the exchanger 2, and of the intermediate exchanger 72, the condenser becoming an evaporator. and reciprocally. By controlling the four-way valve 69, the electronic control unit 47 can thus cause the

  heating or cooling the reformer 1.

  As is now clearly apparent, the method according to the invention makes it possible to manage the temperature of a reformer by supplying it, on demand, with heat or cooling energy. It is therefore suitable for all types of reformers, including

  included in exothermic reformers.

  In addition, the heating or cooling of the reformer 1 is rapid, the thermal effects associated with the condensation and evaporation of a refrigerant being immediate. The method according to the invention is therefore particularly suitable for

  accelerate the heating of the reformer, especially during cold start.

  The device according to the invention also has many other advantages: - The cooling efficiency of the reformer is not affected by the speed of the vehicle, which is generally not the case with air cooling devices. - In the embodiment illustrated in FIG. 3, the device according to the invention makes it possible to manage the thermal needs of a plurality of consumers of thermal energy. The overall management of the thermal needs of all consumers 10 by the electronic control unit 47, some cooling while others heat up, limits the overall flow of primary refrigerant required, and therefore the power of the primary compressor 46 and , if applicable, from

secondary compressor 75.

  - The equipment used to regulate the temperature of the reformer 1 is simple, known and readily available. In addition, the device according to the invention can result from a simple adaptation of the air conditioning circuit of the passenger compartment of the vehicle. - The compressors 46 and 75 respectively and the pump 56, preferably electric, have the advantage of operating independently of the nature of the

  fuel used by the reformer 1.

  - Finally, it is possible to vary the amount of thermal energy transferred to a consumer by varying the flow rate of the refrigerant through the exchanger associated with it. To do this, simply change the degree of opening of the valve

  open associated with this exchanger or the speed of the compressor (s).

  Of course, the invention is not limited to the method and the device described.

  and illustrated, provided by way of nonlimiting example.

  Depending on whether an exchanger condenses or evaporates the primary refrigerant, the associated pressure regulator (Figures 1, 3 and 4) expands at medium pressure a fluid reaching it from the exchanger at high pressure or, respectively, expands to at low pressure a fluid intended for the exchanger reaching it at medium pressure. If a single regulator cannot perform these two detents, it may for example be replaced by another means of expansion such as an assembly with two parallel branches each comprising a regulator adapted to one of the detents and mounted in

series with a non-return valve.

  The high and low pressure valves associated with an exchanger can also be replaced by other means of adjusting the flow rate of the primary refrigerant through this exchanger, for example by a three-way valve at the junction between the high branch pressure, the low pressure branch and the second inlet of this exchanger. The means for reversing the direction of passage of the exchanger 2, and of the intermediate exchanger 72 by the secondary refrigerant (FIG. 4), that is to say the reversing loop 71 and the four-way valve 69 , could also be different from those illustrated. One could, for example, use a secondary refrigerant circuit of architecture similar to that of the primary refrigerant circuit 15 of the figures

l and 3.

  The determination of the thermal requirements of the reformer 1 by the electronic control unit 47 is not limited to the determination as described,

  by means of the temperature sensor 54.

  Finally, the fuel cell P is an example of consumers among others, such as the vehicle interior, batteries, electronic components, etc. If a consumer never needs more than calories or frigories, the low or high pressure branch, respectively, associated with the corresponding exchanger can

advantageously be deleted.

Claims (13)

  1. A method of thermal management of a reformer (1) for producing a fuel intended for a fuel cell (P) of an electrically propelled motor vehicle (V), said method being capable of supplying energy calorific according to the calorific needs of said reformer (1), characterized in that it consists in producing at least part of said energy   heat by condensation of a refrigerant.   2. Method according to claim 1, characterized in that, in case of refrigeration needs of said reformer (1), cooling energy is produced by an evaporation of said refrigerant, then it is transferred to said reformer (1) at least   part of said cooling energy.   3. Method according to resell ication 2, characterized in that one adj uste the amount of ud it condensed or evaporated refrigerant to fix the amount of heat energy   or refrigeration, respectively, transferred to said reformer (1).   4. Device for managing the temperature of a reformer (1) for producing a fuel intended for a fuel cell (P) of an electrically propelled motor vehicle (V), said device being capable of providing calorific energy according to the calorific needs of said reformer (1), characterized in that it comprises a refrigerant circuit (15; 65) in which a refrigerant circulates, said refrigerant circuit (15; 65) comprising at least one compressor (46; 75), a first exchanger (2) in heat transfer relation with said reformer (1), an expansion means (301,302,303; 73) and a second exchanger (2223; 72), said refrigerant circuit being arranged so that said refrigerant condenses in said first exchanger (2,) producing at least part of said   heat energy, and evaporates in said second exchanger (22 23; 72).   5. Device according to claim 4, characterized in that said refrigerant circuit (15) comprises a common branch at medium pressure (28) connected, by means of expansion branches (29 "292,293) on which are inserted a means of expansion (30 "302,303), at the first inputs of at least two exchangers (2" 22,23) of said refrigerant circuit (15), a common branch at low pressure (38) connected to the suction of ud it compressor (46) and, by means of low pressure branches (40 "402,403), to second inlets of said exchangers (2" 2:, 23), and a common high pressure branch (32) connected at the outlet of said compressor (46) and, via high pressure branches (34,34:, 343), also connected to said second inlets, said refrigerant circuit further comprising means for adjusting the flow rate of said refrigerant in said trigger branches (29., 29:, 293), high (34 "34 :, 343), and at low (40 "40:, 403) pressures, and an electronic control unit (47) controlling said adjustment means so that, according to their positions, the refrigerant passing through an exchanger comes from said branch at high pressure (32) or said medium pressure branch (28) and condenses thereon or there   evaporates producing calories or frigories, respectively.   6. Device according to claim 5, characterized in that the means for adjusting the flow rate of said refrigerant comprise high pressure valves (36 "36:, 363) and low pressure valves (42., 422.423) inserted in said   branches at high (34., 34:, 343) and low (40 "40;, 403) pressures, respectively.   7. Device according to claim 6, characterized in that the degree of opening of said high (361,36:, 363) and low (42., 42:, 423) pressures is adjustable continuously.   8. Device according to claim 5, characterized in that said means for adjusting the flow rate of said refrigerant comprise at least one three-way valve inserted at a junction between a high pressure branch (34., 34:, 343), a low pressure branch (40.40:, 403) and a first inlet of a heat exchanger (21,22,23).   9. Device according to any one of claims 5 to 8, characterized in that   said means for adjusting the flow rate of said refrigerant comprise a   compressor (46) with continuously adjustable flow.   10. Device according to any one of claims 5 to 9, characterized in that   said means for adjusting the flow rate of said refrigerant comprise means   regulator (30 "30,303) with continuously variable flow.   11. Device according to claim 4, characterized in that said refrigerant circuit (15) comprises a main loop (57a) in which are inserted in series said first exchanger (2), an expansion means (59), said second exchanger ( 2) and a four-way valve (60), said four-way valve (60) also being inserted in a reversing loop (57b) in which said compressor (46) is inserted, the position of said four-way valve channels (60) determining the direction of circulation of said refrigerant in said main loop, and thus the function of condenser or evaporator of said exchangers (2, 22). 12.Vehicle (V) comprising a reformer (1), characterized in that it further comprises a thermal management device of said reformer (1) according to any one of claims 4 to 11.   13.Vehicle (V) comprising a reformer (1), characterized in that the temperature of said reformer (1) is managed according to a process in accordance with any one of