EP0014630A1 - Thermodynamic engine and its use as a motor or as a refrigerating machine - Google Patents

Abstract

Thermodynamic machine with a fluid work circuit working in the liquid/vapour phase between a hot source (3) and a cold source (2), comprising a motor (8) for utilising the gas expansion of the fluid interposed between the hot source (3) and the cold source (2), each comprising an exchanger, and means (5) for the forced circulation of the fluid in the work circuit, which are driven from the said utilising motor (8), characterised in that the said work circuit has associated with it a refrigerating circuit with refrigerant fluid working in the liquid/vapour phase in order to produce a cold source (2) interacting with the cold-source exchanger (1) of the work circuit, whilst the hot-source exchanger (3) of the work circuit interacts with a medium which need only be the atmosphere or which can be of a temperature higher than the latter, the said refrigerating circuit comprising means for the forced circulation of the refrigerant fluid which are likewise driven from the said utilising motor. <IMAGE>

Description

The invention relates to a thermodynamic machine with a fluid working circuit working in the liquid-vapor phase between a hot source which may be only the atmosphere and a cold source created, according to a new design, using the machine itself, of purely thermal operating principle based on the borrowing of calories from the atmosphere which can be, if necessary, increased by exploiting solar energy or by external combustion of additional supply, which leads to eliminate or reduce the consumption of chemical energy as well as the usual resulting pollution in applications of engine or refrigeration machines in particular.

Essentially, for this purpose, the thermodynamic machine according to the invention, comprising a fluid working circuit working in the liquid-vapor phase between a hot source and a cold source, comprising a motor for using the gaseous expansion of the fluid interposed between the hot source and the cold source each comprising an exchanger, and means for forced circulation of the fluid in the working circuit driven from said operating motor, is characterized in that it is associated with said working circuit a refrigerating circuit with refrigerant working in liquid-vapor phase to create a cold source cooperating with the cold source exchanger of the working circuit, while the hot source exchanger of the working circuit, cooperating with a medium possibly being only the atmosphere or of a higher temperature than the latter, said refrigeration circuit comprising means for forced circulation of the refrigerant also driven from said operating motor.

The invention also extends to a particular embodiment of the refrigeration circuit, while the choice of fluids in the two circuits also conditions its optimization as will be seen below.

• - la figure 1 est une vue schématique d'un circuit de travail de la machine thermodynamique selon l'invention ;
• - la figure 2 est un diagramme température-pression de l'évolution du fluide du circuit de travail au cours d'un cycle complet ;
• - la figure 3 est une vue schématique d'un circuit frigorifique de la machine thermodynamique selon l'invention ;
• - la figure 4 est un diagramme température-pression de l'évolution du fluide frigorigène au cours d'un cycle complet ;
• - la figure 5 est un diagramme partiel illustratif d'une variante du cycle du circuit de travail ;
• - la figure 6 est un diagramme entropique des cycles du circuit de travail et du circuit frigorifique illustratif du rendement d'une machine thermodynamique selon l'invention.

An embodiment of a thermodynamic machine according to the invention is moreover described below, by way of example, and with reference to the appended drawing, in which:

• - Figure 1 is a schematic view of a working circuit of the thermodynamic machine according to the invention;
• - Figure 2 is a temperature-pressure diagram of the evolution of the working circuit fluid during a complete cycle;
• - Figure 3 is a schematic view of a refrigeration circuit of the thermodynamic machine according to the invention;
• - Figure 4 is a temperature-pressure diagram of the evolution of the refrigerant during a complete cycle;
• - Figure 5 is a partial illustrative diagram of a variant of the working circuit cycle;
• - Figure 6 is an entropy diagram of the cycles of the working circuit and the refrigeration circuit illustrating the efficiency of a thermodynamic machine according to the invention.

The working circuit of the machine object of figure 1 comprises an exchanger 1 constituting the cold source of this circuit and in which the working fluid is intended to be liquefied. This exchanger 1 is disposed in an enclosure 2 constituting the cold source of a refrigeration circuit which will be described later.

The working circuit includes another exchanger 3 forming an evaporator and cooperating with the atmosphere.

Between the exchanger 1 and the exchanger 3 are arranged a valve 4 followed by a pump 5 intended to pump the liquefied fluid in order to inject it under a certain pressure into the exchanger 3.

Between the exchanger 3 and the exchanger 1 are successively disposed a storage tank 6 of pressurized gaseous fluid, a valve 7, a turbine 8 constituting the operating motor and a pressure regulator 9 opening directly into the exchanger 1. The turbine 8 is used in particular to drive the pump 5. Initially the valves 4 and 7 are closed and the circuit is loaded with gaseous ethylene under pressure in its part including the pump 5, the exchanger 3 and the storage tank 6.

The cold source being considered as established, the operation of the machine, for which the valves 4 and 7 are put in the open position, takes place in the working circuit according to the cycle object of the temperature-pressure diagram of FIG. 2, the temperature T y being expressed in degrees Kelvin and the pressure P in bars. This cycle is established by way of example for ethylene (C ₂ H ₄ ) chosen as working fluid among other possible, and for a maximum pressure of 30 bars in the flask, from which the possible excess can be derived. by means of a discharge valve 10 on the pipe 11 interposed between turbine 8 and regulator 9, this pipe 11 may include a non-return valve preventing any discharge to the turbine when the valve 7 is closed.

A to B is shown the expansion phase considered adiabatic of ethylene admitted into the turbine 8 from the storage tank 6 until it passes through the regulator 9, at the outlet of which it relaxes along the portion BC of its liquefaction curve L, entering the cold source exchanger 1, where it will be entirely liquefied according to CD and brought to D at a temperature lower than that of its liquefaction temperature under the prevailing residual pressure, which is the temperature corresponding to point C.

This temperature in D depends of course on the temperature reached in the enclosure 2 of cold source and the. diagram of figure 2 is established here for a cold source obtained by using Xenon under 1 bar, which corresponds to a temperature of 165 · k.

The ethylene thus liquefied is then discharged by the pump 5 under a certain pressure in the exchanger 1, this rise in pressure corresponding to the phase DE of the diagram. In exchanger 1, the liquefied ethylene is then heated by the calories captured from the atmosphere by the exchanger, and its temperature in liquid phase rises according to the illustrated phase from E to F, while from this last point F placed on the liquefaction curve L, the ethylene is vaporized in the exchanger 1 and here considered to be heated to constant volume according to the illustrated phase from F to A, where we find ourselves at the initial point A of the cycle corresponding to the state of the ethylene gas in the storage tank 6 (a constant pressure heating diagram would pass through D, E1, A, the practical diagram being established between the two).

To stop the operation of the working circuit, the valve 7 is closed first and the liquid ethylene present in the exchanger 1 is exhausted using the pump 5, towards the exchanger 3 and ball 6, where the ethy lene remains stored in the gas phase, after closing the valve 4. This reconditioning of the circuit is provided with the use of external energy to drive the pump 5 due to the shutdown of the turbine 8, the time required for simple volumetric pumping of the quantity of liquid ethylene present in the exchanger 1, so that after a predetermined timed actuation of the pump 5 the valve 4 can be closed and the working circuit returned to the initial starting condition.

This external energy can be taken outside the machine or taken from storage means associated with the latter and charged by taking from the work of the turbine (such as accumulator batteries supplying an electric motor for driving the pump). An energy balance of such a cycle will be explained later on after the description of the refrigeration circuit creating the cold source.

The refrigeration circuit of the machine object of FIG. 3, with refrigerant working in liquid-vapor phase, comprises a storage tank 12 of gaseous fluid under pressure which is connected by a conduit 13 provided with a valve 14 to a regulator 15 opening in enclosure 2 of cold source.

The vapor phase of the latter is sucked in via a pipe 16 and a compressor 17, which recompresses it to pass it through a valve 18 and a pipe 19 through a heat exchanger 20 disposed in the enclosure 2 and the outlet duct 21 of which opens into the latter via a pressure reducer 22.

On a conduit 23 connecting the valve 18 to the storage tank 12 are also arranged a compressor 24 followed by an exchanger 25 immersed in the atmosphere.

• - une position I de mise en communication du compresseur 17 avec le conduit 19 vers l'échangeur 20 (celle représentée au dessin),
• - et une position II de mise en communication du compresseur 17 avec le conduit 23 vers le compresseur complémentaire 24 (celle obtenue par une rotation indiquée par la flèche F au dessin).

The valve 18 is a two-position selection valve comprising:

• a position I for placing the compressor 17 in communication with the duct 19 towards the exchanger 20 (that shown in the drawing),
• - And a position II of communication of the compressor 17 with the duct 23 to the additional compressor 24 (that obtained by a rotation indicated by the arrow F in the drawing).

The operation of this refrigeration circuit is described below using the temperature-pressure diagram in FIG. 4, corresponding to the use of Xenon as a refrigerant, assuming that initially the valve 14 is closed, the valve 18 is in position I, and that the Xenon in the gaseous state is stored under a pressure of approximately 10 bars, at atmospheric temperature of approximately 290 · K, in the balloon 12, in fact in the part of circuit between the valves 18 and 14 including the exchanger 25 and the tank 12.

By opening the valve 14, the gaseous Xenon of the balloon 12 reaches the regulator 15 where it relaxes along the portion of adiabatic A, Bx followed by the portion BxCx of its liquefaction curve L, which here corresponds roughly to a liquefaction at 50% (ratio of A1 Cx on the ordinate of A1) the residual gas phase being pumped into enclosure 2 by the compressor 17 which recompresses it according to CxDx, by sending it to the exchanger 20 where it is here considered to be cooled to constant volume along the portion of curve DxBx in the diagram, before being expanded again in the expander 22 along the portion BxCx of the liquefaction curve L, where it is then still liquefied to about 50% (cooling at constant pressure would pass the diagram through DxB1, BxCx, the practical diagram being established between the two).

This operation thus continues according to the BxCxDx cycle with gas phase influx coming from the tank 12 according to the ABxCxDxBxCx cycle until the valve 14 is closed so that only the BxCxDx cycle maintained by the compressor drive remains. 17.

To stop with the operation of the machine, working circuit understood as already explained, the operation of the refrigeration circuit, the valve 18 is passed to position II for connection of the compressor 17 on the additional compressor 24 which compresses the gaseous phase of the Xenon up to 'upon exhaustion of its liquid phase in the enclosure 2, by heating it along the portion of adiabatic CxDxE of Figure 4, while it is then cooled in the exchanger 25 to accumulate in the tank 12 to the ambient temperature according to the portion of curve EA returning to the starting point of the cycle, the valve 18 being brought back to position 1 at the end of this phase to maintain the portion of circuit including the tank 12 and between valves 18 and 14 in gas phase under pressure.

This reconditioning of the refrigeration circuit is also provided with the use of external energy to drive the compressors 17 and 24 due to the shutdown of the turbine 8, until, for example, the pressure in the source enclosure 2 cold has fallen to a value corresponding to the absence of liquid Xenon. This energy can be taken as indicated during the presentation of reconditioning of the working circuit.

An energy balance of the two circuits can be established as follows:

avec Y exposant adiabatique égal à

(rapport des cha- leurs massiques à pression et volume constants), T_o la température correspondant à P_o en A et p la pression en B. Puisque α .peut varier entre 1,1 et 1,7, il est préférable de choisir un fluide à petit α. L'éthylène, par exemple, a un α de 1,255 dans la zone des pressions et température mises en jeu, correspondant à un C_v de 8,5 cal/ mole.In the diagram of figure 2, the useful work from A to B is given by the formula:

with Y adiabatic exponent equal to

(ratio of mass heat at constant pressure and volume), T _o the temperature corresponding to P _o at A and p the pressure at B. Since α. can vary between 1.1 and 1.7, it is preferable to choose a fluid with small α. Ethylene, for example, has an α of 1.255 in the region of the pressures and temperatures involved, corresponding to a C _v of 8.5 cal / mole.

If it is chosen that the useful work is done with a residual pressure of 4 bars, and if the ambient temperature is 290 · K, the useful work will be of the order of 700 (calories / mole).

avec ΔT la différence de température entre A et B)(It is obviously also given by:

with ΔT the temperature difference between A and B)

We must subtract from this, the work necessary to compress the ethylene and the work necessary to maintain the cold source.

avec à en bars de D à E la masse moléculaire en grammes la densité en grammes/cm³.The work necessary to compress ethylene is given by:

with at in bars from D to E the molecular mass in grams the density in grams / cm ³ .

As the molecular mass of C ₂ H ₄ is 28 and the density of the liquid is estimated at 0.756 g / cm ³ , we obtain:

Much more important is the work necessary to maintain the cold source whose cycle is given in Figure 4 in the case of Xenon.

As the Y of Xenon is at least 1.6 the gaseous adiabatics are given by:

If the BxCxDx cycle is used only 50% of the Xenon is liquefied. As the heat of vaporization of Xenon is 3,000 calories per mole, the cold source can recover 1,500 calories per mole of Xenon without changing the temperature. To obtain these 1,500 calories, it was necessary to refrigerate the Xenon from Dx to Bx which cost 288 cal / mole (C is at most 3.31).

As these calories are obtained from the cold source, only 1,212 (calories / mole) remains available.

It was also necessary to compress the gas from Cx to Dx which requires 320 cal / mole of Xenon.

As in the ethylene cycle, ethylene is half liquefied and its heat of vaporization is 3,250 (cal / mole), it will be necessary to give, to liquefy the ethylene completely, 1,625 (cal / mole d 'ethylene) at the cold source.

The flow rate in moles of the cold source should therefore be approximately 1.4 moles of Xenon per mole of C ₂ H ₄ . The work of the compressor 17 of the cold source will therefore be 448 cal / mole of ^C ₂ H ₄ .

Each mole of C ₂ H ₄ producing 700 working calories, but this production requiring (448 + 30 - 478) working calories, the useful net work will therefore be approximate 220 calories per mole of C ₂ H ₄ .

For the first start-up of the machine, it may suffice, the valves of the two circuits being in the off position, to fill each circuit with corresponding gas under pressure by means of the valves 26 and 27 respectively provided on balloon 6 and balloon 12, then put the valves in the machine operating position.

Then, the machine can be restarted after stop reconditioning according to the procedures already set out.

It is therefore possible with a thermodynamic machine according to the invention to create a refrigerating machine, or a motor, or a combination of the two, without using energy other than that taken from the atmosphere and while having working pressures which can be easily between 20 and 40 bars in particular.

In use as a motor, the cold source part of the two circuits will of course be carefully insulated to avoid losses in its place.

In use as a refrigerating machine, the cold source enclosure 2 will constitute at least part of itself the role of the usual evaporator in a refrigerating machine.

Of course, the engine of use is not necessarily a turbine but can also be a piston engine with distribution by usual valves, mono or polycylindrical for example, with intake manifold receiving the fluid under pressure from balloon 6 and manifold exhaust connected to the regulator 9 of the working circuit.

The optimization of such a machine leads to consider following rations:

For the working circuit, it will be advantageous to use a fluid having a low heat of vaporization with a low α, as already indicated.

On the contrary, for the cold source circuit, it would be advantageous to use a fluid having a strong heat of vaporization with strong α.

soit élevé, ce qui revient à un C_p petit.In particular if one wants to minimize the expenditure of mechanical energy W in the compressor 17, it is necessary to choose a gas whose ratio γ =

is high, which amounts to a small C _p .

20 cal/mole) à 1,7 (Cp

5 cal/mole).The α vary by 1.1 (C _p

20 cal / mole) to 1.7 (Cp

5 cal / mole).

Such a variation has a considerable effect on W.

From this point of view, the Argon, Neon, Xenon, Krypton family is interesting since these gases have α between 1, 6 and 1.7.

Xenon is all the better as its heat of vaporization is 3,000 cal / mole.

On the other hand, the vaporization temperature of the fluid in the working circuit must be higher than that of the fluid in the cold source circuit, this being to be taken into account given that the smallest pressure in the two circuits has not need to be the same. So that one can relatively increase the vaporization temperature of the working fluid by keeping it under a certain pressure above the atmosphere. We lose part of it liquefaction, so that the cold source must be able to recover more heat.

It would also be beneficial to increase the lowest pressure of the cold source circuit so that the volume required for this circuit is minimized. But this goes against the previous desire.

In the main use of the machine as a motor, it would be beneficial to increase the temperature difference between B and A (figure 2) but this is only possible by choosing B closer to C, ie by decreasing the percentage of active fluid liquefied at C, as long as the ambient temperature remains close to 300 ° K.

In the case of using the machine as a refrigerating machine, it will be advantageous to adopt a diagram for the working circuit such that the turbine 8 produces only the work necessary for driving the pump 5 and the compressor 17, and possible storage of reconditioning energy, and in which point B will be chosen as high as possible on the liquefaction curve, taking into account the maximum pressure chosen in A.

But it is also possible to use a hot source at a temperature higher than that of the atmosphere, in particular by application or concentration of solar energy, by external combustion or recovery of any heat, applied to the exchanger 1 of the circuit. work or an additional exchanger interposed between the latter and the storage tank 6, to work in particular at higher temperature.

As the current liquid pumps are suitable for working at pressures much higher than those previously indicated, it will be preferable to modify then the work cycle illustrated in FIG. 2 as indicated in FIG. 5, as for the upper part of the diagram, the new points of this being designated by the same reference letters assigned the index "prime", and the lines T and T 'corresponding respectively to the ambient temperature and to the higher temperature considered of the hot source.

We see on this diagram that we then compress the liquid ethylene from E to E '.

Without this overcompression, which costs little work, the curve starting from the level EF and passing through A would lead to A ", while with it the curve passing through the level E'F 'will lead to A', which can in particular be chosen so as to be higher on the same adiabatic as that passing through A, that is to say without modifying point B of FIG. 2, chosen according to the considerations previously exposed.

An example has been given in FIG. 6 of an entropy diagram for the two fluid circuits, with ethylene in the working circuit and with Xenon in the refrigeration circuit, this diagram making it possible to assess the efficiency which can be expected from a such machine.

• AB est la détente utile de l'éthylène.
• BC correspond à la détente le long de la courbe de liquéfaction.
• CD correspond au refroidissement de l'éthylène de sa température de liquéfaction à celle du Xénon.
• DE correspond au pompage de l'éthylène liquide.
• EF correspond au réchauffement de ce liquide.
• FF correspond à sa vaporisation.
• FA correspond au réchauffement du gaz.

In this diagram, (T, S) for the two fluids (C ₂ H ₄ and Xenon) (Figure 6), the ethylene cycle is the cycle (A, B, C, D, E, F, F, A) while the Xenon cycle is the cycle (Dx, Bx, Cx, Cx, Dx).

• AB is the useful expansion of ethylene.
• BC corresponds to the expansion along the liquefaction curve.
• CD corresponds to the cooling of ethylene from its liquefaction temperature to that of Xenon.
• DE corresponds to the pumping of liquid ethylene.
• EF corresponds to the heating of this liquid.
• FF corresponds to its vaporization.
• FA corresponds to the heating of the gas.

The band "Ambient temperature" Ta shows when the possible auxiliary hot source must intervene which will heat the gas from this ambient temperature to the temperature corresponding to A.

For the Xenon cycle, the segment (Cx-Cx) corresponds to the evaporation of Xenon in the cold source, the segment (Cx-Dx) corresponds to the compression of the gaseous Xenon, the segment (Dx-Bx) corresponds to cooling , the segment (Bx-Cx) corresponds to the expansion along the liquefaction curve.

The cycles are given for 1 mole of ethylene therefore for 1.4 mole of Xenon and this is why the heat exchanges simulated by (D-C) and (Cx-Cx) are equal.

le rendement théorique du moteur n'est que de : 16,3 %.Useful work is represented by the area (A, B, C, D, E, F, F, A) minus the work required by the refrigerant circuit, i.e. the hatched area (Dx, Bx, Cx, Cx, Dx) , while Carnot's performance would be

the theoretical efficiency of the engine is only: 16.3%.

But all or a large part of the heat is given by the ambient air which costs nothing.

Of course, various embodiments can be envisaged for the two working and associated refrigeration circuits constituting the machine according to the invention, without however departing from the field of the latter.

Claims (13)

1.- Thermodynamic machine with fluid working circuit working in the liquid-vapor phase between a hot source and a cold source, comprising a motor for using the gaseous expansion of the fluid interposed between the hot source and the cold source each comprising a exchanger, and means for forced circulation of the fluid in the working circuit driven from said operating motor, characterized in that it is associated with said working circuit a refrigerant circuit with refrigerant working in liquid-vapor phase to create a cold source cooperating with the cold source exchanger of the working circuit, while the hot source exchanger of the working circuit cooperates with a medium which may be only the atmosphere or of a higher temperature than the latter, said refrigeration circuit comprising means of forced circulation of the refrigerant also entrained from said engine of use. 2. Thermodynamic machine according to claim 1, characterized in that the fluid of the working circuit has an adiabatic exponent (α) lower than that of the fluid of the refrigerating circuit. 3. Thermodynamic machine according to one of the preceding claims, characterized in that the heat of vaporization of the fluid in the working circuit is relatively low compared to that of the fluid in the refrigerating circuit. 4. Thermodynamic machine according to one of the preceding claims, characterized in that the refrigeration circuit comprises a cold source enclosure, a compressor drawing the gaseous refrigerant from the enclosure and returning it to an exchanger inside the enclosure, and a regulator opening into the enclosure and connected to the outlet of said interior exchanger. 5. Thermodynamic machine according to claim 4, characterized in that the refrigeration circuit comprises an accumulator tank of pressurized gaseous refrigerant connected by means of a control valve to start up a regulator opening into the enclosure. from a cold source, and a shut-off selection and control valve intended to interrupt the communication between said compressor and the interior exchanger, to connect this "compressor to a complementary compressor which is connected to said accumulator tank via a exchanger bathing at least in the atmosphere. 6. Thermodynamic machine according to claim 1, characterized in that the means of forced circulation of the working fluid are constituted by a pump of the liquefied phase of the latter leaving said cold source. 7. _- Thermodynamic machine according to claim 6, ca _- characterized in that the pump delivers into said heat source exchanger followed by a pressurized gaseous working fluid storage tank which is connected to the intake of the engine for use the output of which is connected by a pressure reducer to said cold source exchanger, and that two isolation valves are respectively provided, of one. part between the latter tank and the use engine and, secondly, between the cold source and said pump. 8. A thermodynamic machine according to claim 7, characterized in that a relief valve is provided between the accumulator tank and a conduit connecting the engine of use to the regulator. 9. Thermodynamic machine according to one of the preceding claims, characterized in that the fluid of the working circuit is ethylene. 10. _- Thermodynamic machine according to one of the claims tions above, characterized in that the refrigerant is Xenon. 11. Thermodynamic machine according to claims 1, 5, 6 and 7, characterized in that the aforementioned pump and the compressors are subjected to auxiliary drive means brought into play when the machine stops to recondition each circuit in gaseous fluid under pressure in its part including said accumulator tank. 12.- The application of a thermodynamic machine according to one of the preceding claims, as a source of mechanical energy by its engine of use. 13.- The application of a thermodynamic machine according to one of the preceding claims, as a refrigerating machine via the cold source of the refrigerating circuit.

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