# Patent

## Title
Plant for producing cold, heat and/or work

## Abstract

A plant for the producing of cold, heat and/or work. The plant includes at least one modified Carnot machine having a first assembly that includes an evaporator Evap combined with a heat source, a condenser Cond combined with a heat sink, a device DPD for pressurizing or expanding a working fluid GT, a means for transferring said working fluid GT between the condenser Cond and DPD, and between the evaporator Evap and DPD; a second assembly that includes two transfer vessels CT and CT′ that contain a transfer liquid LT and the working fluid GT in the form of liquid and/or vapor; a means for selectively transferring the working fluid GT between the condenser Cond and each of the transfer vessels CT and CT′, as well as between the evaporator Evap and each of the transfer enclosures CT and CT′; and a means for selectively transferring the liquid LT between the transfer vessels CT and CT′ and the compression or expansion device DPD, said means including at eat hydraulic converter.

## Background
RELATED APPLICATIONS
This application is a National Phase application of PCT/FR2009/000365, filed on Mar. 30, 2009, which in turn claims the benefit of priority from French Patent Application No. 08 01786, filed on Apr. 1, 2008, the entirety of which are incorporated herein by reference)
The present invention relates to a refrigeration, heat and/or work production plant.
TECHNOLOGICAL BACKGROUND
Thermodynamic machines used for refrigeration, heat production or energy production all refer to an ideal machine called the “Carnot machine”. An ideal Carnot machine requires a heat source and a heat sink at two different temperature levels—it is therefore a “dithermal” machine. It is called a “driving” Carnot machine when it operates by delivering work and a “receiving” Carnot machine (also called a Carnot heat pump) when it operates by consuming work. In driving mode, the heat Qhi is delivered to a working fluid GT from a hot source at the temperature Thi, the heat Qlo is yielded by the working fluid GT to a cold sink at the temperature Tlo and the net work W is delivered by the machine. Conversely, in heat pump mode, the heat Qlo is taken by the working fluid GT to the cold source Tlo, the heat Qhi is yielded by the working fluid to the hot sink at the temperature Thi and the net work W is consumed by the machine.
According to the second law of thermodynamics, the efficiency of a dithermal (driving or receiving) machine, that is to say a real machine whether operating in the Carnot cycle or not, is at most equal to that of the ideal Carnot machine and depends only on the temperatures of the source and of the sink. However, the practical implementation of the Carnot cycle, consisting of two isothermal steps (at temperatures Thi and Tlo) and two reversible adiabatic steps, encounters a number of difficulties that have not been completely solved hitherto. During the cycle, the working fluid may still remain in the gaseous state or it may undergo a liquid/vapor change of state during the isothermal transformations at Thi and Tlo. When a liquid/vapor change of state occurs, the heat transfers between the machine and the environment take place with a higher efficiency than when the working fluid remains in the gaseous state. In the first case and for the same exchanged thermal power levels at the heat source and at the heat sink, the exchange areas are smaller (and therefore less expensive). However, when there is a liquid/vapor change of state, the reversible adiabatic steps consist in compressing and expanding a liquid/vapor two-phase mixture. The techniques of the prior art do not allow two-phase mixtures to be compressed or expanded. According to the current prior art it is not known how to carry out these transformations correctly.
To remedy this problem, it has been envisaged to approximate the Carnot cycle by isentropically compressing a liquid and isentropically expanding a superheated vapor (for a driving cycle) and by compressing the superheated vapor and isenthalpically expanding the liquid (for a receiving cycle). However, such modifications induce irreversibilities in the cycle and very significantly reduce its efficiency, that is to say the efficiency of the motor or the coefficient of performance or the coefficient of amplification of the heat pump.
GENERAL DEFINITION OF THE INVENTION
The object of the present invention is to provide a thermodynamic machine operating in a cycle close to the Carnot cycle, which is better than the machines of the prior art, that is to say a machine that operates with a liquid/vapor change of state of the working fluid in order to maintain the advantage of the low contact areas required, while still substantially limiting the irreversibilities in the cycle during the adiabatic steps.
One subject of the present invention is a refrigeration, heat and/or work production plant, comprising at least one modified Carnot machine. Another subject of the invention is a refrigeration, heat and/or work production process using a plant comprising at least one modified Carnot machine.
A refrigeration, heat or work production plant according to the present invention comprises at least one modified Carnot machine formed by:

    a) a 1st assembly that comprises an evaporator Evap associated with a heat source, a condenser Cond associated with a heat sink, a device PED for pressurizing or expanding a working fluid GT, means for transferring the working fluid GT between the condenser Cond and the PED and between the evaporator Evap and the PED;
    b) a 2nd assembly that comprises two transfer chambers CT and CT′ that contain a transfer liquid LT and the working fluid GT in liquid and/or vapor form, the transfer liquid LT and the working fluid being two different fluids;
    c) means for the selective transfer of the working fluid GT between the condenser Cond and each of the transfer chambers CT and CT′ on the one hand, and between the evaporator Evap and each of the transfer chambers CT and CT′ on the other; and
    d) means for the selective transfer of the liquid LT between the transfer chambers CT and CT′ and the compression or expansion device PED, said means comprising at least one hydraulic converter.


In the present text:

    
    
        “modified Carnot cycle” means a thermodynamic cycle comprising the steps of the theoretical Carnot cycle or similar steps with a degree of reversibility of less than 100%;
        “modified Carnot machine” denotes a machine having the above features a), b), c) and d);
        “hydraulic converter” denotes either a hydraulic pump or a hydraulic motor;
        “hydraulic pump” denotes a device that uses mechanical energy delivered by the environment to the “modified Carnot machine” to pump a hydraulic transfer fluid LT at low pressure and to restore it at higher pressure;
        “auxiliary hydraulic pump” denotes a device that uses mechanical energy delivered by the environment to the “modified Carnot machine” or taken from the work delivered to the environment by the “modified Carnot machine” to pressurize either the transfer liquid LT or the working fluid GT in the liquid state;
        “hydraulic motor” denotes a device that delivers mechanical energy generated by the modified Carnot machine to the environment by depressurizing the transfer liquid LT at high pressure and restoring it at lower pressure;
        “environment” denotes any element external to the modified Carnot machine, including heat sources and sinks and any element of the plant to which the modified Carnot machine is connected;
        “reversible transformation” means a transformation that is reversible in the strict sense, and also a quasi-reversible transformation. The sum of the variations in entropy of the fluid that undergoes the transformation and of the environment is zero during a strictly reversible transformation corresponding to the ideal case, and slightly positive during an actual, quasi-reversible transformation. The degree of reversibility of a cycle may be quantified by the ratio of the efficiency (or the coefficient of performance COP) of the cycle to the efficiency of the Carnot cycle operating between the same extreme temperatures. The greater the reversibility of the cycle, the closer this ratio is to 1 (the ratio always being less than 1);
        “isothermal transformation” means a strictly isothermal transformation or one under conditions close to the theoretical isothermal nature, recognizing that, under actual operating conditions, during a transformation considered to be isothermal carried out cyclically, the temperature T undergoes slight variations, such that ΔT/T is ±10%; and
        “adiabatic transformation” means a transformation with no heat exchange with the environment, or with heat exchange that it is endeavored to minimize by thermally isolating the fluid that undergoes the transformation and the environment.
    
    


The refrigeration, heat and/or work production process according to the invention consists in making a working fluid GT undergo a succession of modified Carnot cycles in a plant according to the invention comprising at least one modified Carnot machine. A modified Carnot machine comprises the following transformations:

    
    
        an isothermal transformation with heat exchange between GT and the heat source, or between GT and the heat sink;
        an adiabatic transformation with a reduction in the pressure of the working fluid GT,
        an isothermal transformation with heat exchange between GT and the heat sink, or between GT and the heat source; and
        an adiabatic transformation with an increase in the pressure of the working fluid GT.
    
    


The process is characterized in that:

    
    
        the working fluid is in a liquid-gas two-phase form at least during the two isothermal transformations of a cycle; and
        the two isothermal transformations produce or are produced by a change in volume of GT concomitant with the displacement of a transfer liquid LT that drives or is driven by a hydraulic converter, and as a consequence, work is delivered or received by the plant by means of a hydraulic fluid which flows through a hydraulic converter during at least the two isothermal transformations.
    
    


In one embodiment, the work is received or delivered by the plant via a hydraulic fluid which flows through a hydraulic converter during just one of the adiabatic transformations. In this embodiment, the modified Carnot cycle and the modified Carnot machine are referred to as being “of the 1st type”.
In one embodiment, the work is received or delivered by the plant via a hydraulic fluid which flows through a hydraulic converter during both adiabatic transformations. In this embodiment, the modified Carnot cycle and the modified Carnot machine are referred to as “of the 2nd type”.



DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the liquid/vapor equilibrium curves for various fluids that can be used as working fluid GT. The saturation vapor pressure P (in bar) is plotted on the y-axis, on a logarithmic scale, as a function of the temperature T (in ° C.) plotted on the x-axis.
FIG. 2 shows a schematic view of a modified driving Carnot machine of the 2nd type.
FIG. 3 shows, in a Mollier diagram used by refrigeration engineers, a modified driving Carnot cycle followed by a working fluid GT. The pressure P is plotted on a logarithmic scale as a function of the enthalpy per unit mass h of the working fluid.
FIG. 4 shows, in a Mollier diagram, three modified driving Carnot cycles of the 2nd type that have the same temperature Tlo of the working fluid during heat exchange with the cold sink and increasing temperatures T′′hi, T′hi, and Thi, of the working fluid during heat exchange with the hot source.
FIG. 5 is a schematic representation of a modified driving Carnot machine of the 1st type.
FIG. 6 shows, in a Mollier diagram, a modified driving Carnot cycle of the 1st type followed by a working fluid GT. The pressure P is plotted on a logarithmic scale as a function of the enthalpy per unit mass h of the working fluid.
FIG. 7 shows a schematic view of a modified receiving Carnot machine of the 2nd type.
FIG. 8 shows, in a Mollier diagram, a modified receiving Carnot cycle of the 2nd type followed by a working fluid GT. The pressure P is plotted on a logarithmic scale as a function of the enthalpy per unit mass h of the working fluid.
FIG. 9 shows a schematic view of a modified receiving Carnot machine of the 1st type.
FIG. 10 shows, in a Mollier diagram, a modified receiving Carnot cycle of the 1st type followed by a working fluid GT. The pressure P is plotted on a logarithmic scale as a function of the enthalpy per unit mass h of the working fluid.
FIG. 11 shows a schematic view of a modified Carnot machine that can operate depending on the choice of the user in the 1st driving mode or in the 1st receiving mode.
FIGS. 12a and 12b illustrate schematically two embodiments of modified driving Carnot machines operating between the same extreme temperatures Thi and Tlo, these figures indicating the direction of heat exchange and work exchange between these machines and the environment. FIG. 12a shows an embodiment of thermal coupling at an intermediate temperature level between two modified driving Carnot machines. FIG. 12b shows another embodiment with a single modified driving Carnot machine.
FIG. 13 shows schematically the heat source and sink temperature levels and the direction of heat exchange and work exchange in a plant comprising a high-temperature modified driving Carnot machine mechanically coupled to a low-temperature modified receiving Carnot machine.
FIG. 14 shows schematically the heat source and sink temperature levels and the direction of heat exchange and work exchange in a plant comprising a low-temperature modified driving Carnot machine mechanically coupled to a high-temperature modified receiving Carnot machine.
FIGS. 15a to 15h show schematically the heat and work exchange between a modified Carnot machine (or combinations of such machines) and the environment, and also the heat source and sink temperatures, for 8 examples involving various working fluids.
FIGS. 16, 17 and 18 show, in Mollier diagrams for water, n-butane and 1, 1,1,2-tetrafluoroethane, the various modified Carnot cycles involved in the 8 examples of FIG. 15.



DETAILED DESCRIPTION OF THE INVENTION
In a plant according to the present invention, a modified Carnot machine may have a driving machine configuration or a receiving machine configuration. In both cases, the machine may be of the 1st type (work exchange between the transfer liquid and the environment during one of the adiabatic transformations) or of the 2nd type (work exchange between the transfer liquid and the environment during both adiabatic transformations). A modified Carnot machine may also have a configuration that allows, depending on the choice of the user, operation in driving (1st or 2nd type) mode or in receiving (1st or 2nd type) mode.
The process for controlling a driving machine comprises at least one step during which heat is supplied to the plant, with a view to recovering work during at least one of the transformations of the modified Carnot cycle. The process for controlling a receiving machine comprises at least one step during which work is supplied to the plant, with a view to recovering heat at the hot sink Thi or removing heat at the cold source at Tlo during at least one of the isothermal transformations of the modified Carnot cycle.
The process according to the present invention consists in subjecting a working fluid GT to a succession of cycles between a heat source and a heat sink. In what follows, for the sake of simplification and because this does not affect the operating principle of the modified Carnot machine, no distinction is made between the temperature of the hot source or sink and that of the working fluid that exchanges with this source or sink, these temperatures being denoted by Th. Likewise, no distinction is made between the temperature of the cold source or sink and that of the working fluid that exchanges with this source or sink, these temperatures being denoted by Tlo. Thus, any heat exchange is considered to be perfect.
The working fluid GT and the transfer liquid LT are preferably chosen in such a way that GT is weakly soluble, preferably insoluble, in LT, GT does not react with LT, and in the liquid state GT is less dense than LT. When the solubility of GT in LT is too high or if GT in the liquid state is denser than LT, it is necessary to isolate them from each other by a means that does not prevent work exchange. Said means may consist for example in interposing a flexible membrane between GT and LT which creates an impermeable barrier between the two fluids but which offers only very slight resistance to the displacement of the transfer liquid and slight resistance to heat transfer. Another solution is formed by a float that has a density intermediate between that of the working fluid GT in the liquid state and that of the transfer liquid LT. A float may constitute a large physical barrier, but it is difficult to make it perfectly effective if it is desired for there to be no friction on the side walls of the chambers CT and CT′. On the other hand, the float may constitute a very effective thermal resistance. The two solutions (membrane and float) may be combined.
The transfer liquid LT is chosen from liquids that have a low saturation vapor pressure at the operating temperature of the plant so as to avoid, in the absence of a separating membrane as described above, limitations due to diffusion of the GT vapor through the LT vapor at the condenser or at the evaporator. Provided that there is the abovementioned compatibility with GT, nonexhaustive examples of LT may be water or a mineral oil or a synthetic oil, preferably one having a low viscosity.
The working fluid GT undergoes transformations in the temperature/pressure thermodynamic domain preferably compatible with liquid-vapor equilibrium, that is to say between the melting point and the critical temperature. However, during the modified Carnot cycle some of these transformations may occur completely or partly in the supercooled liquid or superheated vapor domain, or the supercritical domain. Preferably, a working fluid is chosen from pure substances and azeotropic mixtures so as to have a one-variable relationship between temperature and pressure at liquid-vapor equilibrium. However, a modified Carnot machine according to the invention may also operate with a nonazeotropic solution as working fluid.
The working fluid GT may for example be water, CO2, or NH3. The working fluid may also be chosen from alcohols containing 1 to 6 carbon atoms, alkanes containing 1 to 18 (more particularly 1 to 8) carbon atoms, chlorofluoroalkanes preferably containing 1 to 15 (more particularly 1 to 10) carbon atoms and partially or completely fluorinated or chlorinated alkanes preferably containing 1 to 15 (more particularly 1 to 10) carbon atoms. In particular, mention may be made of 1,1,1,2-tetrafluoroethane, propane, isobutane, n-butane, cyclobutane, and n-pentane. FIG. 1 shows the liquid/vapor equilibrium curves for a few of the aforementioned fluids GT. The saturation vapor pressure P (in bar) is plotted on a logarithmic scale on the y-axis as a function of the temperature T (in ° C.) plotted on the x-axis.
A fluid that can be used as working fluid may act as driving fluid or as receiving fluid, depending on the plant in which it is used, on the available heat sources and on the desired objective.
In general, the working fluids and transfer liquids are firstly chosen according to the available heat source and heat sink temperatures and the desired maximum or minimum saturation vapor pressures in the machine, and then according to other criteria, such as especially toxicity, environmental impact, chemical stability and cost.
The fluid GT in the chambers CT or CT′ may be in the liquid/vapor two-phase mixture state after the adiabatic expansion step in the case of the driving cycle or after the adiabatic compression step in the case of the receiving cycle. In this case, the liquid phase of GT accumulates at the GT/LT interface. When the vapor content of GT is high (typically between 0.95 and 1) in the chambers CT or CT′ before said chambers are connected with the condenser, it is conceivable for the liquid phase of GT in these chambers to be completely eliminated. This elimination may be carried out while maintaining the temperature of the working fluid GT in the chambers CT or CT′ at the end of the steps of bringing the chambers CT or CT′ into communication with the condenser, at a value above that of the working fluid GT, in the liquid state in the condenser, so that there is no liquid GT in CT or CT′ at this moment.
In one embodiment, the plant comprises means for heat exchange between, on the one hand, the heat source and the heat sink, which are at different temperatures, and, on the other hand, the evaporator Evap, the condenser Cond and possibly the working fluid GT in the transfer chambers CT and CT′.
When the hydraulic converter of the modified Carnot machine is a hydraulic motor and the temperature of the source is above the temperature of the sink, the modified Carnot machine is a driving machine. A plant according to the present invention may comprise a single modified driving Carnot machine, or such a machine coupled to a complementary device, depending on the intended objective. The coupling may be achieved thermally or mechanically.
In a modified driving Carnot machine of the 1st type, the device PED consists of a device that pressurizes the working fluid GT in the saturated liquid or supercooled liquid state, for example an auxiliary hydraulic pump AHP1.
In a modified driving Carnot machine of the 2nd type, the pressurization or expansion device PED comprises, on the one hand, a compression/expansion chamber ABCD and the transfer means associated therewith and, on the other hand, an auxiliary hydraulic pump AHP2 that pressurizes the hydraulic transfer fluid LT.
In a process according to the invention implemented according to a modified driving Carnot cycle, the cycle comprises the following transformations:

    
    
        an isothermal transformation during which heat is delivered to GT from the heat source at the temperature Thi;
        an adiabatic transformation with a reduction in the pressure of the working fluid GT;
    
    


an isothermal transformation during which heat is delivered by GT to the heat sink at the temperature Tlo below the temperature Thi; and
an adiabatic transformation with an increase in the pressure of the working fluid GT.
When the process of the invention is a succession of modified driving Carnot cycles, the heat source is at a temperature above the temperature of the heat sink. Each cycle is formed by a succession of steps during which there is a change in volume of the working fluid GT. This variation in volume causes a displacement of the liquid LT that drives a hydraulic motor or is caused by a displacement of the liquid LT which is driven by an auxiliary hydraulic pump. Thus, the plant consumes work during certain steps and this is recovered during other steps, whereas over the complete cycle there is a net production of work to the environment. The environment may be an ancillary device that transforms the work delivered by the plant to electricity, to heat or to refrigeration power. A process for operating a modified driving Carnot machine is described in greater detail on the basis of the machine shown schematically in FIG. 2.
FIG. 2 shows a schematic view of a modified driving Carnot machine of the 2nd type that comprises an evaporator Evap, a condenser Cond, an isentropic compression/expansion chamber ABCD, a hydraulic motor HM, an auxiliary hydraulic pump AHP2 and two transfer chambers CT and CT′. These various elements are connected together by a first circuit containing exclusively the working fluid GT and a second circuit containing exclusively the transfer liquid LT. Said circuits comprise various branches that can be closed off by controlled valves.
The evaporator Evap and the condenser Cond contain exclusively the fluid GT, in general in the liquid/vapor mixture state. However, depending on the working fluid GT and the temperature of the hot source Thi, said working fluid GT may be in the supercritical domain at said temperature Thi and, under these conditions, the evaporator Evap contains GT only in the gaseous state. It is the liquid LT that passes exclusively through the motor HM and the pump AHP2. The elements ABCD, CT and CT′ constitute the interfaces between the two (GT and LT) circuits and they contain the hydraulic transfer fluid LT in the bottom portion and/or the working fluid GT in the liquid, vapor or liquid/vapor mixture state in the upper portion.
ABCD is connected to Cond and to Evap by circuits containing GT that can be closed off by the solenoid valves SV3 and SV4 respectively. Evap is connected to CT and CT′ by circuits containing GT that can be closed off by the solenoid valves SV1 and SV1′ respectively. Cond is connected to CT and CT′ by circuits containing GT that can be closed off by the solenoid valves SV2 and SV2 respectively. In the embodiment shown in FIG. 2, the closure means are two-way solenoid valves. However, other types of valves, whether controlled or not, may be used, especially pneumatic valves, slide valves or nonreturn valves. Certain pairs of two-way valves (i.e. having an inlet and an outlet) may be replaced with three-way valves (having one inlet, two outlets, or two inlets and one outlet). Other possible valve combinations are within the competence of a person skilled in the art.
In the embodiment shown in FIG. 2, the liquid passing through the hydraulic motor always flows in the same direction. In this embodiment, which is the most frequent one for a hydraulic motor, the high-pressure transfer liquid LT is always connected to the motor HM at the same inlet (on the right in FIG. 2) and the low-pressure transfer liquid LT is always connected to the motor HM at the same outlet (on the left in FIG. 2). Since the chambers CT and CT′ are alternately at high pressure and at low pressure, a set of solenoid valves serves for connecting them to the appropriate inlet/outlet of the motor HM. Thus, the hydraulic motor HM is connected on the inlet (or upstream) side to CT and CT′ by a circuit containing high-pressure LT that can be closed off by the solenoid valves SVhi and SVhi′ respectively, and is connected on the outlet (or downstream) side to CT and CT′ by a circuit containing low-pressure LT that can be closed off by the solenoid valves SVlo and SVlo′ respectively. For example in the step of the cycle shown in FIG. 2, the high pressure is in the chamber CT′ and the low pressure in CT; the solenoid valves SVhi′ and SVlo are open and the solenoid valves SVhi and SVlo are closed, the transfer liquid flowing through HM from right to left. During the other half of the cycle, the high pressure is in CT and the low pressure is in CT′, the solenoid valves SVhi′ and SVlo are closed and the solenoid valves SVhi and SVlo′ are open, but the transfer liquid passes through the hydraulic motor in the same direction (from right to left).
ABCD is connected in its lower portion to the downstream end of HM by a circuit containing the transfer liquid LT and comprising, in two parallel branches, the auxiliary hydraulic pump AHP2 and the solenoid valve SVr. When LT flows from HM to ABCD, it is pressurized by AHP2 and SVr is closed. When LT flows from ABCD to MH, it flows under gravity, SVr is open and AHP2 is stopped. Since the transfer liquid LT is finally transferred to CT or CT′, it is necessary for ABCD to be above the chambers CT and CT′.
In FIG. 2, the shaft SH of the hydraulic motor HM is connected to a receiver (i.e. a work-consuming element), either directly or via a conventional coupling. The receiver is an alternator ALT coupled directly to the shaft of the hydraulic motor, and the auxiliary hydraulic pump AHP2 is connected via a magnetic clutch MC. Other coupling modes, such as a universal joint, a belt or a magnetic or mechanical clutch, may be used. Likewise, other receivers may be connected onto the same shaft, for example a water pump, a modified receiving Carnot machine, or a conventional heat pump (with mechanical vapor compression). If necessary, a flywheel may also be mounted on this shaft to promote the concatenation of the receiving and driving steps of the cycle.
A modified Carnot cycle may be described in the Mollier diagram used by refrigeration engineers, in which the pressure P is plotted on a logarithmic scale as a function of the enthalpy per unit mass h of the working fluid. FIG. 3 shows the Mollier diagram of the modified driving Carnot cycle followed by the working fluid GT.
Depending on the fluid GT used, the step of isentropically expanding the saturated vapor at the outlet of the evaporator may result in a two-phase mixture or in superheated vapor. In FIG. 3, the two-phase mixture case is shown by the path between the points “c” and “d” shown as a dotted line and the superheated vapor case is shown by the path between the points “c” and “dsv” shown as the solid line. Furthermore, whatever GT is, the vapor at the outlet of the evaporator may be superheated in such a way that, after the isentropic expansion, there is only superheated vapor or vapor at the saturation limit. This 3rd case is shown in FIG. 3 by the path between the points “csv” and “dsv” shown as the dash-dot line. Any incursion at the start or end of the isentropic expansion in the superheated vapor domain generates irreversibilities and therefore results in a reduction in efficiency of the cycle. However, when the position of the point “d” is very close to the saturated vapor stage, it is preferable to eliminate any liquid GT in the chambers CT or CT′ by superheating GT after the isentropic expansion. The choice of means for heating GT in CT and CT′ is within the competence of a person skilled in the art. The heat may for example be supplied by an electrical resistance element or by exchange with the hot source at Thi. The heat exchange may take place in a heat exchanger integrated into the LT circuit, said LT exchanging heat in turn with GT at their interface in CT and CT′. The heat exchange may also take place at the side walls of CT and CT′. It is the latter possibility that is shown in FIG. 2, in which the heat at the temperature Ti is supplied to CT.
The modified driving Carnot cycle is formed by four successive phases starting at times tα, tγ, tδ and tλ respectively. This is described below with reference to the a-b-c-dsv-e-a cycle of the Mollier diagram shown in FIG. 3. The principle is the same for the a-b-csv-dsv-e-a cycle.
αβγ Phase (Between the Times tα, and tγ):
At the time immediately preceding tα, the level of LT is low (denoted by L) in ABCD and the cylinder CT, and is high (denoted by H) in the cylinder CT′. At the same instant, the saturation vapor pressure of GT has a low value Plo in ABCD and CT and a high value Phi in Evap and CT′. It is this instant of the cycle that the configuration of the plant shown schematically in FIG. 2 corresponds to.
At time tα, the opening of the solenoid valves SVlo′, SV2, SVhi′ and SVlo and the engagement of the AHP2 cause the following effects:

    
    
        the saturated GT vapor leaving the evaporator at Phi penetrates CT′ and delivers the transfer liquid LT to an intermediate level (denoted by J). LT passes through the motor HM, expanding therein and producing work, a portion of which is recovered by the pump AHP2;
        after having been expanded by HM, a portion of the transfer liquid LT is transferred to CT and the other portion of the liquid LT is transferred to ABCD. In CT, the LT passes from the low level to the intermediate level (denoted by I), and discharges the GT vapor into the condenser, where it condenses and accumulates in the bottom portion (the valve SV2 being open and the valve SV3 being closed). The other portion of LT is taken in by the pump AHP2 and discharged at a higher pressure into ABCD, thereby enabling the liquid/vapor GT mixture contained in this chamber to be isentropically compressed.
    
    
    In the Mollier diagram (FIG. 3), this step corresponds to the following simultaneous transformations:
    
        a→b in the chamber ABCD;
        b→c in the Evap-CT′ assembly;
        dsv→e in the CT-Cond assembly.
    
    


The pressurization of GT from the low pressure Plo up to the high pressure Phi in ABCD must be carried out before it is introduced into the evaporator, which is still at the high pressure Phi. It is therefore only at the time tβ that the solenoid valve SV4 (which may be replaced by a nonreturn valve) between ABCD and Evap is opened. This requires there to be a stock of GT in the liquid state in the evaporator at the start of this phase, which stock is reconstituted at the end of this step.
From an energy standpoint, during this αβγ phase, heat Qhi has been consumed at the evaporator at Thi, heat Qlo, has been released at the condenser at Tlo (Tlo<Thi) and a net work Wαβγ has also been delivered to the outside.
γδ Phase (Between Times tγ and tδ):
At time tγ, that is to say when the level of LT has reached the predefined values (I in CT, J in CT′ and H in ABCD), the valves SV2, SVlo and SVhi′ are left open and the solenoid valves SV3 and SVr are opened. As a result:

    
    
        the GT vapor contained in CT′ continues to expand, but quasi-adiabatically (c→d→dsv transformation in the Mollier diagram of FIG. 3) and again discharges the transfer liquid LT through the motor HM into the cylinder CT. In fact, this transformation may be decomposed into a strictly adiabatic expansion (c→d) which ends up, depending on the fluid GT, in the two-phase domain or in the superheated vapor, followed by a slight superheating (d→dsv) via the walls of CT′ that are kept at a temperature sufficient to permit this (between Tlo and Thi). The transformation d→dsv is not essential; if after the strictly adiabatic expansion (c→d) the fluid GT is in the two-phase domain, the liquid GT will be partially discharged at the end of this γδ phase into the condenser; the chamber ABCD in communication with the condenser is brought back down to the low pressure and the transfer liquid LT that it contains in its lower portion flows under gravity into CT, which must therefore be preferably beneath ABCD. However if the solenoid valve SVr is opened slightly before the solenoid valve SV3 and if a small amount of GT remains in the saturated liquid state in the upper portion of ABCD, then the depressurization of LT during the step of communicating with CT causes the remainder of said liquid GT initially at the high pressure Phi to be partially or completely vaporized. Under these conditions, the pressure upstream of SVr may be sufficient throughout the duration of LT transfer so as to compensate for the liquid column height, and the chamber ABCD is then not necessarily above the chambers CT and CT′;
        because of the rise in the level of LT (from 1 to H) in CT, the remainder of the GT vapor in CT condenses in Cond (e→a transformation); and
        all the condensates (those accumulated during the preceding phase and those of the present phase) are in ABCD.
    
    


From an energy standpoint, during this γδ phase, heat Qea is released at the condenser at Tlo, a little heat (taken from the hot source at Thi) is possibly consumed in CT′ to provide the d→dsv superheating and work Wβγ is also delivered to the outside.
The second portion of the cycle is symmetric: the evaporator, the condenser and ABCD are the sites of the same successive transformations, whereas the roles of the chambers CT and CT′ are reversed.
δελ Phase (Between Times tδ and tλ):
This phase is equivalent to the αβγ phase but with the transfer chambers CT and CT′ reversed.
λα Phase (Between Times tλ and tα):
This phase is equivalent to the γδ phase but with the transfer chambers CT and CT′ reversed.
After the λα phase, the modified driving Carnot machine of the 2nd type is in the α state of the cycle described above. The various thermodynamic transformations followed by the fluid GT (with the d→+dsv transformation considered as optional) and the levels of the transfer liquid LT are given in Table 1. The states of the actuators (solenoid valves and clutch of the pump AHP2) are given in Table 2, in which x indicates that the corresponding solenoid valve is open or that the pump AHP2 is engaged.










TABLE 1









Trans-
LT level












Step
formation
Location
CT
CT′
ABCD





αβγ
a → b
ABCD
L→I
H→J
L→H



b → c
Evap + CT′



d or dsv → e
CT + Cond


γδ
c → d or dsv
CT′
I→H
J→L
H→L



e → a
CT + Cond + ABCD


δελ
a → b
ABCD
H→J
L→I
L→H



b → c
Evap + CT



d or dsv → e
CT′ + Cond


λα
c → d or dsv
CT
J→L
I→H
H→L



e → a
CT′ + Cond + ABCD




























TABLE 2





Step
SV1
SV1′
SV2
SV2′
SV3
SV4
SVlo
SVhi
SVlo′
SVhi′
SVr
AHP2







αβγ

x
x


x(to tβ)
x


x

x


γδ


x

x

x


x
x



δελ
X


x

x (to tε)

x
x


x


λα



x
x


x
x

x









Work production is continuous throughout the duration of the cycle, but not at constant power, either because the pressure difference across the terminals of the hydraulic motor varies, or because a portion, which can vary over time, of this work is recovered by the auxiliary hydraulic pump AHP2. This is not a problem if the work delivered to the outside is used directly for a receiving machine that does not have to be constant within the cycle, such as a water pump or a modified receiving Carnot machine. Of course, the average power over a cycle remains constant from one cycle to another, when a steady operating state is reached and if the temperatures Thi and Tlo remain constant.
Moreover, the evaporator is isolated from the rest of the circuit during the γδ and λα phases, whereas the heat supplied by the hot source at Thi is a priori continuous. Under these conditions, during these isolation phases there will be a temperature rise and therefore a pressure rise in the evaporator followed by a sudden drop at times tα and tδ when the valve SV1 or SV1′ reopens.
In a preferred method of implementing the process of the invention, the fact that the transfer liquid LT is incompressible and the fact that the variations in level which occur simultaneously in the three chambers ABCD, CT and CT′ are therefore not independent are taken into account. Moreover, these variations in the level of LT result from or involve concomitant variations in the volume of the fluid GT. This is represented by the following equation between the densities of GT at various stages of the cycle:

ρe−ρa=ρc  (Equation 1)

ρi being the density of GT at the thermodynamic state of the point “i”, “i” being e, a, dsv and c respectively.

FIG. 4 shows the Mollier diagrams for three modified driving Carnot cycles of the 2nd type, namely the a′′-b′′-c′′-dsv-e′′-a′′ cycle, the a′-b′-c′-dsv-e′-a′ cycle and the a-b-c-dsv-a cycle. These three cycles have the same GT temperature Tlo in the condenser and increasing GT temperatures in the evaporator, namely T′′hi, T′hi and Thi; respectively. In this figure, the dot-dashed curves are curves at constant density.
When the temperatures of the condenser and the evaporator are very close (or even coincident), the point “e” in the Mollier diagram is close to the point “a” (or coincident therewith) as shown schematically in the a′′-b′′-c′′-dsv-e′′-a′′ cycle. As the temperature difference between the heat sink and the heat source increases, the point “e” moves away from the point “a” and approaches the point “dsv”. The a′-b′-c′-dsv-e′-a′ cycle represents an intermediate case and the a-b-c-dsv-a cycle represents the extreme case in which the points “e” and “dsv” are coincident. As the efficiency of the modified driving Carnot cycle increases with the temperature difference between the heat sink and the heat source, the a-b-c-dsv-a cycle is preferable provided that there is a heat source at the temperature Thi sufficient for a fixed sink temperature Tlo.
In this preferred case (in which ρe=ρdsv), equation 1 reduces to ρc=ρa as shown in FIG. 4. Furthermore, the steps described in the general configuration of the operating process of the modified driving Carnot machine of the 2nd type are simplified since the dsv (or d)→e transformation no longer takes place.
Thus, the temperature difference (Thi−Tlo) between the two isothermal transformations of the modified driving Carnot cycle cannot exceed a certain value ΔTmax which depends on one of the temperatures (Thi or Tlo and on the chosen working fluid GT. Now, the performance of the modified Carnot machine depends especially on this value ΔTmax. To obtain the maximum performance with a given fluid GT and a given temperature Thi or Tlo, it is necessary to choose the other operating conditions such that the ρa/ρc ratio is as close as possible to 1 (but always less than 1), or preferably such that 0.9≦ρa/ρc≦1 and more particularly 0.95≦ρa/ρc≦1.
The various thermodynamic transformations of this preferred method of implementation are given in Table 3 and the states of the actuators (solenoid valves and clutch of the pump AHP2) are given in Table 4 in which x means that the corresponding solenoid valve is open or that the pump AHP2 is engaged.










TABLE 3









Trans-
LT level












Step
formation
Location
CT
CT′
ABCD





αβγ
a → b
ABCD
L
H→J
L→H



b → c
Evap + CT′


γδ
c → d or dsv
CT′
L→H
J→L
H→L



d or dsv → a
CT + Cond + ABCD


δελ
a → b
ABCD
H→J
L
L→H



b → c
Evap + CT


λα
c → d or dsv
CT
J→L
L→H
H→L



d or dsv → a
CT′ + Cond + ABCD




























TABLE 4





Step
SV1
SV1′
SV2
SV2′
SV3
SV4
SVlo
SVhi
SVlo′
SVhi′
SVr
AHP2







αβγ

x



x(to tβ)



x

x


γδ


x

x

x


x
x



δελ
x




x (to tε)

x



x


λα



x
x


x
x

x









The steps of the modified driving Carnot cycle of the 2nd type in the preferred configuration are explained in detail below if they differ from those described above for the general configuration.
Starting from an initial state in which, on the one hand, the working fluid GT is maintained in the evaporator Evap at high temperature and in the condenser Cond at low temperature by heat exchange with the hot source at Thi and the cold sink at Tlo<Thi, respectively and, on the other hand, all the GT and transfer liquid LT communication circuits are closed, the working fluid GT is subjected to a succession of cycles comprising the following steps:
αβγ Phase (Between Times tα and tγ):
At time tα, the opening of the solenoid valves SV1′ and SVhi′ the engagement of AHP2 cause the following effects:

    
    
        the saturated GT vapor leaving the evaporator at Phi enters CT′ and discharges the transfer liquid LT at an intermediate level (denoted by J). LT passes through the motor HM, being expanded therein, thereby producing work, a portion of which is recovered by the pump AHP2; and after having been expanded by HM, the transfer liquid LT is taken in by the pump AHP2 and delivered at a higher pressure to ABCD, which enables the liquid/vapor GT mixture contained in this chamber to be isentropically compressed.
    
    


In the Mollier diagram (FIG. 4), this step corresponds to the following simultaneous transformations:
a→b in the chamber ABCD;
b→c in the Evap-CT′ assembly.
The pressurization of GT from Plo to Phi in ABCD must be carried out before it is introduced into the evaporator, which is always at the high pressure Phi. It is therefore only at time tβ that the solenoid valve SV4 (which may be replaced by a nonreturn valve) between ABCD and Evap is opened.
From an energy standpoint, during this αβγ phase, heat Qhi has been consumed at the evaporator at T′hi and net work Wαβγ has also been delivered to the outside.
γδ Phase (Between Times tγ and tδ):
At time tγ, that is to say when the level of LT has reached the predefined values (J in CT′ and H in ABCD), the valves SV1′ and SV4 are closed, SVhi′ is left open and the solenoid valves SV2, SV3, SVlo and SVr are opened. As a result:

    
    
        the GT vapor contained in CT′ continues to expand, but adiabatically or quasi-adiabatically, that is to say according to the c→d transformation (possibly followed by d→dsv) and discharges the transfer liquid LT through the motor HM into the cylinder CT. This transformation may be decomposed into a strictly adiabatic expansion (c→d) which ends up, depending on the fluid GT, in the two-phase domain or in the superheated vapor, followed by a slight superheating (d→dsv) by the walls of CT′ that are maintained at a sufficient temperature to allow this (between Tlo and Thi);
        the chamber ABCD in communication with the condenser is brought back down to the low pressure and the transfer liquid LT that it contains in its lower portion flows under gravity into CT, which must therefore be preferably below ABCD. However, if the solenoid valve SVr is opened slightly before the solenoid valve SV3 and if a small amount of GT remains in the saturated liquid state in the upper portion of ABCD, then the depressurization of LT during the step of communication with CT causes the remainder of said liquid GT initially at the high pressure Phi to be partially or completely vaporized. Under these conditions, the pressure upstream of SVr may be sufficient throughout the duration of the LT transfer to compensate for the liquid column height and the chamber ABCD is then not necessarily above the chambers CT and CT′;
        because of the rise in the level of LT (from L to H) in CT, the GT vapor contained in CT condenses in the condenser Cond (d or dsv→a transformation); and
        the condensates do not accumulate in Cond since they flow under gravity into the chamber ABCD.
    
    


From an energy standpoint, during this γδ phase, heat Qda is released in the condenser at Tlo, a small amount of heat (taken from the hot source at Thi) is possibly consumed in CT′ in order to provide the superheating d→dsv and work Wγδ is also delivered to the outside.
As in the general case of the method of implementing the process of the invention in a modified driving Carnot machine of the 2nd type, the other half of the cycle is symmetric:

    
    
        the δελ phase (between times tδ and tλ) is equivalent to the αβγ phase but with the transfer chambers CT and CT′ reversed; and
        the λα phase (between times tλ and tα) is equivalent to the γδ phase but with the transfer chambers CT and CT′ reversed.

More particularly:

        at time tδ, all the circuits opened at time tγ are closed, the GT circuit between Evap and CT is opened (by SV1), the LT circuit between CT and upstream of the hydraulic motor HM is opened (by SVhi) and the auxiliary pump AHP2 is actuated, so that:
        
            the saturated GT vapor leaving Evap at the high pressure Phi enters CT and delivers LT at an intermediate level J;
            LT passes through HM, expanding therein, and is then taken in by AHP2 and discharged into ABCD;
        
        
        at time tε, the GT circuit between ABCD and Evap is opened (by SV4) so that the working fluid GT is introduced into the evaporator in the liquid state;
        at time tλ, the GT circuit between Evap and CT on the one hand and between ABCD and Evap on the other is closed, the auxiliary pump AHP2 is stopped, the GT circuit is opened between Cond and ABCD (by SV3) on the one hand and between CT′ and Cond (by SV2′) on the other, and the LT circuit between CT′ and ABCD is opened (by SVr and SVlo′) so that:
        
            the GT vapor contained in CT continues to expand, adiabatically, and discharges LT up to the low level in CT and then through HM into CT′;
            the chamber ABCD in communication with Cond is brought back down to the low pressure and LT, which it contains in its lower portion, flows into CT′; and
            the GT vapor contained in CT′ condenses in Cond.
        
        
    
    


After several cycles, the plant operates in a steady state in which the hot source continuously delivers heat at the temperature Thi to the evaporator Evap, heat is delivered continuously by the condenser Cond to the cold sink at the temperature Tlo, and work is delivered continuously by the machine.
In this preferred case of the modified driving Carnot cycle of the 2nd type, there is, for a given working fluid and for whatever temperature of the condenser Tlo, a maximum value of the temperature Thi-max of the evaporator such that the densities ρc and ρa are equal. However, if there is a heat source at a temperature Thi well above Thi-max, it is possible a priori for the machine to have a higher efficiency, either by combining, in cascade, two modified driving Carnot machines in the plant of the invention, or by using, in the plant, a modified driving Carnot machine of the 1st type.
In a modified driving Carnot machine of the 1st type, the pressurization/expansion device placed between the condenser Cond and the evaporator Evap comprises an auxiliary hydraulic pump AHP1 and a solenoid valve SV3 in series. FIG. 5 is a schematic representation of the device. The elements identical to those of the driving machine of the 2nd type are denoted by the same references. The solenoid valve SV3 may be replaced by a simple nonreturn valve, which itself may be integrated into the pump AHP1. The working fluid GT in the saturated liquid state at the outlet of the condenser Cond is directly pressurized by the pump AHP1 and introduced into the evaporator Evap.
In FIG. 5, the possibility of supplying heat at the temperature Ti into the chambers CT and CT′ has not been shown, but it remains possible as in FIG. 2.
The various steps of the cycle and the states of the actuators (solenoid valves and AHP1 pump) are explained in detail below and given in Tables 5 and 6.











TABLE 5









Trans-
LT level














Step
formation
Location
CT
CT′







αβ
a → b
Between Cond
L→I
H→J





and Evap




b → bl → c
Evap + CT′




dsv → e
CT + Cond



βγ
c → dsv
CT′
I→H
J→L




e → a
CT + Cond



γδ
a → b
Between Cond
H→J
L→I





and Evap




b → bl → c
Evap + CT




dsv → e
CT′ + Cond



δα
c → dsv
CT
J→L
I→H




e → a
CT′ + Cond


















TABLE 6








Open solenoid valves or operating AHP1 pump

















Step
SV1
SV1′
SV2
SV2′
SV3
SVlo
SVhi
SVlo′
SVhi′
AHP1





αβ

x
x

x
x


x
x


βγ


x

x
x


x
x


γδ
x


X
x

x
x

x


δα



X
x

x
x

x









The steps of the modified driving Carnot cycle of the 1st type are described below for the points that differ from what has been described above for the modified driving Carnot cycle of the 2nd type in its general configuration. The first cycle is carried out from an initial state in which the working fluid GT is maintained in the evaporator Evap at high temperature and in the condenser Cond at low temperature by heat exchange with the hot source at Thi and the cold sink at Tlo, respectively, and all the communication circuits for the working fluid GT and for the transfer liquid LT are closed off. At time t0, the auxiliary hydraulic pump AHP1 is actuated and the GT circuit between Cond and Evap is opened (by SV3) so that a portion of GT, in the saturated or supercooled liquid state, is taken in by AHP1 in the lower portion of the condenser Cond and discharged in the supercooled liquid state into Evap where it heats up, and then GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
αβ Phase (Between Times tα and tβ):
At the time immediately preceding tα, the level of LT is low (denoted by L) in the cylinder CT and high (denoted by H) in the cylinder CT′. At the same instant, the saturation vapor pressure of GT has a low value Plo in CT and a high value Phi in Evap and CT′. It is this instant of the cycle which is shown schematically in FIG. 5.
At time tα, the opening of the solenoid valves SV1′, SV2, SV3, SVhi′ and SVlo and the operation of the AHP1 cause the following effects:

    
    
        the saturated GT vapor leaving the evaporator at Phi enters CT′ and discharges the transfer liquid LT at an intermediate level (denoted by J). LT passes through the motor HM, being expanded therein, thereby producing work. The work necessary for the AHP1 is delivered by an independent electric motor (not shown). In a variant, the pump AHP1 may be connected to the shaft of the hydraulic motor via the magnetic clutch MC so that, during this step, a portion of the work delivered by the hydraulic motor is recovered by the pump AHP1;
        after having been expanded by HM, the transfer liquid LT is delivered into CT. In CT, LT passes from the low level to the intermediate level (denoted by I), discharges the GT vapor into the condenser, where it condenses. The working fluid GT in the saturated liquid state is taken in by the pump AHP1 and delivered at a higher pressure into Evap, where it enters in the supercooled liquid state.
    
    


In the Mollier diagram (FIG. 6), this step corresponds to the following simultaneous transformations:
a→b between the condenser and the evaporator;
b→b1→c in the Evap-CT′ assembly;
dsv→e in the CT-Cond assembly.
It is preferable for the auxiliary hydraulic pump AHP1 not to be operating and for the solenoid valve SV3 not to be open if there is no liquid GT upstream of this pump. A liquid level detector may be placed as safety element to stop the pump and close the solenoid valve if necessary. The evaporation of GT in Evap is continuously compensated for by supplies of liquid GT coming from the condenser so that the level of liquid GT in the evaporator is approximately constant.
From an energy standpoint, during this αβ phase, heat Qhi has been consumed in the evaporator at Thi, heat Qde has been released in the condenser at Tlo (Tlo<Thi) and net work Wαβ has also been delivered to the outside, said work Wαβ being the difference between the work delivered by the hydraulic motor HM and that consumed by the auxiliary hydraulic pump AHP1.
βγ Phase (Between Times tβ and tγ):
At time tβ, that is to say when the level of LT has reached the predefined values (I in CT and J in CT′), the solenoid valve SV1′ is closed, the valves SV2, SV3, SVlo and SVhi′ are left open and the pump AHP1 is operating (if liquid GT is present upstream). It follows that:

    
    
        the GT vapor contained in CT′ continues to expand, but adiabatically (c→dsv transformation in the Mollier diagram of FIG. 6) and again discharges the transfer liquid LT through the motor HM into the cylinder CT. As in the embodiment illustrated by FIG. 3, this transformation may be decomposed into a strictly adiabatic expansion (c→d) which ends up, depending on the fluid GT used, in the two-phase domain or in the superheated vapor, followed by slight superheating (d→dsv) by the walls of CT′ maintained at a sufficient temperature for allowing this (between Tlo and Thi);
        because of the rise in the level of LT (from I to H) in CT, the remainder of the GT vapor in CT condenses in Cond (e→a transformation); and as in the case of the previous step, the condensates are taken in by AHP1 as they accumulate at the bottom of the condenser.
    
    


From an energy standpoint, during this βγ phase, heat Qea is released in the condenser at Tlo, a small amount of heat (taken from the hot source at Thi) is consumed in CT′ for the d→dsv, superheating, and net work Wβγ is also delivered to the outside.
The other half is symmetric: the evaporator and the condenser are the sites of the same successive transformations, whereas the roles of the chambers CT and CT′ are reversed.
γδ Phase (Between Times tγ and tδ) and δα Phase (Between Times tδ and tα):
These phases are equivalent to the αβ phase and the βγ phase respectively, but with the transfer chambers CT and CT′ reversed.
More particularly:


    
    
        at time tγ, the circuits opened at time tβ are closed, except for that for transferring GT between Cond and Evap (via SV3), the GT circuit is opened between Evap and CT (by SV1) on the one hand and between CT′ and Cond (by SV2′) on the other, and the circuit for transferring LT from CT to CT′ passing via the hydraulic motor HM is opened (by SVhi and SVlo′), so that:
        
            GT is heated and evaporates in Evap and the saturated GT vapor leaving Evap at the high pressure Phi enters CT and delivers LT at an intermediate level J;
            LT passes through HM, being expanded therein, and then LT is delivered to CT′ up to the intermediate level I;
            the GT vapor contained in CT′ and discharged by the liquid LT condenses in Cond; and
            GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser Cond, where it is progressively taken in by AHP1 and then discharged in the supercooled liquid state into Evap;
        
        
        at time tδ, the GT circuit between Evap and CT is closed (i.e. closure of SV1) so that:
        
            the GT vapor contained in CT continues to expand, adiabatically, and discharges LT up to the low level in CT and then through HM into CT′ where it reaches the high level;
            the remainder of the GT vapor contained in CT′ and discharged by the liquid LT condenses in Cond; and
            GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser Cond where it is progressively taken in by AHP1 and finally discharged in the supercooled liquid state into Evap.
        
        
    
    


After several cycles, the plant operates in a steady state in which the hot source continuous delivers heat at high temperature Thi in the evaporator Evap, heat is continuously delivered by the condenser Cond into the cold sink at Tlo and work is continuously delivered by the machine.
In this configuration (of the 1st type), equation (1) linking the densities of GT in the various steps of the cycle is still valid, i.e.:

ρe−ρa=ρdsv−ρc  (equation 1)

However, the density of GT leaving the condenser, i.e. in the saturated liquid state (point “a” in the Mollier diagram) is always much lower than that of GT leaving the evaporator, that is to say in the saturated or superheated vapor state (point “c” or “csv” in the Mollier diagram) irrespective of the temperature difference between Thi and Tlo. Thus, the following double inequality is still satisfied:

ρa<ρc<ρdsv  (inequality 1)

The point “e” is always between the points “a” and “dsv” in the Mollier diagram and the temperatures Tlo and Thi may be fixed completely independently without this affecting the operation of the modified driving Carnot machine of the 1st type.

The modified driving Carnot, machine of the 1st type is simpler in its operation and comprises fewer constituent elements. However, as in the case of the Rankine cycle, the b→b1 transformation generates appreciable irreversibilities, this having an unfavorable effect on the efficiency of the cycle. However, since the increase in the difference (Thi−Tlo has, conversely, a positive effect on this efficiency, it is possible, depending on the thermodynamic conditions and the fluid GT that are chosen, for the efficiency of the modified driving Carnot machine of the 1st type to be finally higher than that of the modified driving Carnot machine of the 2nd type, including in its preferred configuration.
When the process of the invention is a succession of modified receiving Carnot cycles, the heat source is at a temperature Tlo below the temperature Thi of the heat sink. Each cycle is formed by a succession of steps during which there is a change in volume of the working fluid GT. This variation in volume causes or is caused by a displacement of the liquid LT. Thus during certain steps, the plant consumes work and restores work during other steps, but over the complete cycle there is a net consumption of work delivered by the environment via a hydraulic pump HP.
In a modified receiving Carnot machine of the 1st type, the adiabatic expansion step is isenthalpic rather than isentropic. This is because the work that can be recovered during the isentropic expansion is low in comparison with the work involved during the other steps of the cycle. The isenthalpic expansion requires only a simple irreversible adiabatic expansion device, the pressurization or expansion device may be a capillary tube or an expansion valve. In a modified receiving Carnot machine of the 2nd type, it is necessary for the pressurization and expansion device to be an adiabatic compression/expansion bottle ABCD and the associated transfer means. Thus, in this preferred configuration of the 1st type, the coefficient of performance or the coefficient of amplification of the modified receiving Carnot machine will be slightly reduced (while still being higher than the equivalent machines of the prior art) but with a significant simplification of the process and a lower cost.
When the process of the invention is a succession of modified receiving Carnot cycles, the heat source is at a temperature Tlo below the temperature Thi of the heat sink. Each cycle is formed by a succession of steps during which there is a change in volume of the working fluid GT. This variation in volume causes or is caused by a displacement of the liquid LT. Thus during certain steps the plant consumes work and restores work during other steps, but over the complete cycle there is a net consumption of work delivered by the environment via a hydraulic pump HP.
FIG. 7 shows a schematic view of a modified receiving Carnot machine of the 2nd type which comprises an evaporator Evap, a condenser Cond, an isentropic compression/expansion chamber ABCD, a hydraulic pump HP and two transfer chambers CT and CT′. These various elements are connected together by a first circuit containing exclusively the working fluid GT and a second circuit containing exclusively the transfer liquid LT. Said circuits comprise various branches that can be closed off by means which may or may not be controlled. In the embodiment shown in FIG. 7, the controlled valves are two-way solenoid valves. However, other types of controlled valves may be used, especially pneumatic valves, slide valves or nonreturn valves. Certain pairs of two-way valves (i.e. having one inlet and one outlet) may be replaced with three-way valves (one inlet and two outlets, or two inlets and one outlet). Other possible valve combinations are within the competence of a person skilled in the art.
The evaporator Evap and the condenser Cond contain exclusively the fluid GT in general in the liquid/vapor mixture state. However, depending on the working fluid GT and the temperature Thi of the hot sink, said working fluid GT may be in the supercritical domain at Thi and under these conditions the condenser Cond contains GT only in the gaseous state.
Passing through the pump HP is exclusively liquid LT. The elements ABCD, CT and CT′ constitute the interfaces between the two (GT and LT) circuits. They contain the hydraulic transfer fluid LT in the lower portion and/or the working fluid GT in the liquid, vapor or liquid-vapor mixture state in the upper portion. ABCD is connected to Cond and to Evap by circuits containing GT that can be closed off by the solenoid valves SV3 and SV4 respectively. Evap is connected to CT and CT′ by circuits containing GT that can be closed off by the solenoid valves SV1 and SV1′ respectively. Cond is connected to CT and CT′ by circuits containing GT that can be closed off by the solenoid valves SV2 and SV2′ respectively.
In general, the liquid passing through a hydraulic pump always flows in the same direction. It is this most common option which is shown in FIG. 7. This means that the low-pressure transfer liquid LT is always connected to the pump HP at the same inlet (on the left in FIG. 7) and that the high-pressure transfer liquid LT is always connected to the pump HP at the same outlet (on the right in FIG. 7). Since the chambers CT and CT′ are alternately at high pressure and at low pressure, a set of solenoid valves serves to connect them to the appropriate inlet/output of the pump HP. Thus, the pump HP is connected on the inlet (or upstream) side to CT and CT′ by a circuit containing LT at low pressure which can be closed off by the solenoid valves SVlo and EVlo′ respectively, and on the outlet (or downstream) side to CT and CT′ by a circuit containing LT at high pressure that can be closed off by the solenoid valves SVhi and SVhi′ respectively. For example, if the high pressure is in the chamber CT′ and the low pressure in CT, the solenoid valves SVhi′ and SVlo are open and the solenoid valves SVhi and SVlo′ are closed, the transfer liquid flows through HP from left to right. During the other half of the cycle, the high pressure is then in CT and the low pressure in CT′, and the solenoid valves SVhi′ and SVlo are closed and the solenoid valves SVhi and SVlo′ are open, but the transfer liquid passes through the hydraulic pump in the same direction (from left to right).
ABCD is connected in its lower portion by two parallel branches of the circuit containing the transfer liquid LT. The branch that can be closed off by the solenoid valve SVi is connected to the high-pressure LT circuit and the branch that can be closed off by the solenoid valve SVr is connected to the low-pressure circuit. When LT flows from ABCD into the transfer chamber CT or CT′, it flows under gravity and it is therefore necessary for ABCD to be above the chambers CT and CT′.
The shaft of the hydraulic pump HP must be connected to one or more drive devices (i.e. delivering work) either directly or via a conventional coupling, such as a universal joint, a belt or a clutch (whether magnetic or mechanical). For example in FIG. 7, the shaft SH is connected to an electric motor EM via a magnetic clutch MC1, whereas another magnetic clutch MC2 serves to couple other motors, such as a hydraulic turbine, a gasoline or diesel engine, a gas-powered engine, or a modified driving Carnot machine. Finally, if necessary, a flywheel may also be mounted on this shaft to promote the concatenation of the receiving and driving steps of the cycle.
The modified receiving Carnot cycle followed by the driving fluid GT is described in the Mollier diagram shown in FIG. 8.
Depending on the fluid GT used, the step of isentropically compressing the saturated vapor at the outlet of the evaporator may result in a two-phase mixture or in superheated vapor. In FIG. 8, the first case (two-phase mixture, which is quite rare) is represented by the path between the points “1” and “2” shown by the dotted line and the second case (superheated vapor) is shown by the path between the points “1” and “2sv” shown by the solid line. Moreover, irrespective of GT, the vapor at the outlet of the evaporator may be slightly superheated in such a way that, after the isentropic compression, there is only superheated vapor or vapor at the saturation limit. This third case is shown in FIG. 8 by the path between the points “1sv,” and “2sv” shown by the dot-dashed line. Any incursion at the start or end of the isentropic compression in the superheated vapor domain generates irreversibilities and therefore causes a slight reduction in the coefficient of performance or coefficient of amplification of the cycle. As in the case of the modified driving Carnot machine, it is possible to superheat GT at the inlet of the isentropic compression, but this provides only a slight advantage (it avoids any liquid GT being present in the chambers CT or CT′) and only in the case in which said isentropic compression results in the two-phase domain. The technical solutions for producing this superheating are the same as in the case of the driving machine (electrical resistance element, heat exchange with the hot source at Thi, etc.) and are not shown in FIG. 7.
The device for introducing the working fluid GT into the evaporator is designed so that GT is introduced in the liquid state into the evaporator, but after the saturated liquid (point 3 in the Mollier diagram of FIG. 8) has been expanded, and therefore occupying more volume and with an overhead above the remaining liquid (point 4 of the Mollier diagram in FIG. 8). One solution among other conceivable solutions consists in introducing a flexible suction tube with its sucking end fixed to a float in ABCD just beneath the float line. The chamber ABCD must be placed above the GT liquid level in the evaporator (as shown in FIG. 7) and above CT and CT′ so that the discharge, either of liquid GT or of LT, into one or other reservoir can take place by gravity.
The modified receiving Carnot cycle is formed by four successive phases starting at times tα, tγ, tδ and tλ respectively. Only the 1-2sv-3-4-5-1 cycle is described below since the variant with the “1sv” point does not modify the principle.
Starting from an initial state in which all the communication circuits for the working fluid GT and for the transfer liquid LT are closed off, at t0, the hydraulic pump HP is actuated and then GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
αβγ Phase:
At the instant immediately preceding tα, the level of LT is high (denoted by H) in ABCD and the cylinder CT, and is low (denoted by L) in the cylinder CT′. At the same instant, the saturation vapor pressure of GT has a high value Phi in ABCD, Cond and CT and has a low value Plo in Evap and CT′. It is this instant of the cycle which is shown schematically in the configuration of FIG. 7.
At time tα, the solenoid valves SVr, SVlo and SVhi′ are opened. The isentropic expansion of GT to the liquid/vapor mixture state (but with an almost zero vapor content by weight) in ABCD discharges LT through HP. At the same time, the very small amount of saturated vapor and the transfer liquid LT that are contained in CT follow the same pressure variation, which, owing to the small amount of vapor, is not accompanied by a significant variation in the level of LT in CT. The transfer liquid LT downstream of HP isentropically compresses the GT vapor contained in CT′. The pressures upstream and downstream of the pump HP are balanced at time tβ. Between tα and tβ there is theoretically no net consumption of work delivered by the pump HP. The time interval tβ-tα is short, since during this step there is no heat transfer.
At time tβ, the solenoid valves SV1 and SV4 are opened. The consequences are the following:

    
    
        after SV1 has been opened, the saturated GT vapor leaving the evaporator at Phi enters CT and delivers the transfer liquid LT at an intermediate level (denoted by J). This liquid is taken in and pressurized by the pump HP, which consumes net work delivered by the outside. On leaving the pump, LT is delivered into the cylinder CT′ (up to the level I), thereby enabling the isentropic compression of GT up the pressure Phi to be completed; and after SV4 has been opened, the working fluid GT in the saturated liquid state and at low pressure Plo flows under gravity into the evaporator Evap, which more than compensates, in terms of mass, for the gaseous GT outlet into CT.

During this αβγ phase, the following transformations were carried out:

    
    


3→4 transformation in ABCD;
4→5 transformation in the Evap-CT assembly; and
1→2sv transformation in CT′. The compression is isentropic and it is assumed that, for the fluid GT used, this ends up in the superheated vapor domain.
From an energy standpoint, during this αβγ phase, heat Q45 has been pumped into the evaporator at Tlo and work Wαβγ has also been consumed by the pump HP. This work has been delivered by the outside with a power increasing from tβ since the pressure upstream of the pump remains virtually constant (=Plo) after this instant, whereas the downstream pressure increases up to Phi.
γδ Phase:
At time tγ, i.e. when the level of LT has reached the predefined values (L in ABCD, J in CT and I in CT′), SV1, SVlo and SVhi′ are left open and the solenoid valves SV2′, SV3 and SVi are opened simultaneously. As a result, the GT vapor continues to be produced in the evaporator and to be expanded in CT (5→1 transformation), thereby again discharging the transfer liquid taken in by the pump into the cylinder CT′, which is this time connected to the condenser. The GT vapor contained in CT′ is desuperheated (partly in CT′) and completely condenses in the condenser (2sv→3 transformation) in which the vapor does not accumulate since it is discharged under gravity into ABCD. In parallel, a portion of the transfer liquid LT output by the pump is discharged into ABCD, in order to reestablish the high LT level therein.
From an energy standpoint, during this αβ phase, heat Q51 is pumped into the evaporator at Tlo, heat Q23 is released in the condenser at Thi (with Thi>Tlo), which requires work Wγδ delivered by the outside. This work is at almost constant power since the pressures upstream and downstream of the pump are also practically constant (with nonlimiting heat exchangers at the condenser and the evaporator).
At time tδ, one half of the cycle is complete. The other half is symmetric: the evaporator, the condenser and the chamber ABCD are the sites for the same successive transformations, but the roles of the chambers CT and CT′ are reversed.
δελ Phase (Between Times tδ and tλ) and λα Phase (Between Times tλ and tα):
These phases are equivalent to the αβγ phase and to the γδ phase respectively, but with the transfer chambers CT and CT′ reversed.
More particularly:

    
    
        at time tδ, all the circuits opened at time tγ are closed, the LT circuits for transferring LT are opened (by SVr) on the one hand from the chamber ABCD to the upstream end of the hydraulic pump HP and, on the other hand, from CT′ to CT passing via the hydraulic pump HP (by SVlo′ and SVhi) so that:
        
            GT in the liquid/vapor equilibrium state in ABCD and in CT′ is expanded from the high pressure Phi to the low pressure Plo and delivers LT through HP into CT;
            the GT vapor contained in CT is adiabatically compressed;
        
        
        at time tε, the GT circuit is opened between Evap and CT′ (by SV1′) on the one hand and between ABCD and Evap (by SV4) on the other, so that:
        
            LT is taken in by the pump HP, which pressurizes it and discharges it into CT;
            the LT levels in ABCD, CT and CT′ pass from high to low, from low to an intermediate level I, and from high to an intermediate level J, respectively;
            because the volume occupied by the GT vapor in CT′ increases, GT evaporates in Evap and the saturated GT vapor leaving Evap at the low pressure Plo enters CT′;
            the GT vapor contained in CT continues to be adiabatically compressed up to the high pressure Phi;
            GT in the saturated liquid state at the low pressure Plo flows under gravity from ABCD into Evap;
        
        
        at time tλ, the GT circuit between ABCD and Evap is closed (by SV4), the LT circuit between ABCD and the upstream side of the pump HP is closed (by SVr), the GT circuit is opened between CT and Cond (by SV2) on the one hand and between Cond and ABCD (by SV3) on the other, and the LT circuit between the downstream side of the pump HP and ABCD is opened (by SVi) so that:
        
            LT is again taken in by the pump HP, which pressurizes it and delivers it into CT;
            the LT levels in ABCD, CT and CT′ pass from low to high, from the intermediate level I to high and from the intermediate level J to low, respectively;
            because the volume occupied by the GT vapor in CT′ continues to increase, GT evaporates in Evap and the saturated GT vapor leaving Evap at the low pressure Plo enters CT′;
            the GT vapor contained in CT at high pressure Phi is discharged by LT and condenses in Cond; and
            GT in the saturated liquid state flows under gravity from Cond into ABCD.
        
        
    
    


After several cycles, the plant operates in a steady state.
For refrigeration, in the initial state GT is maintained in the condenser Cond at high temperature by heat exchange with the hot sink at Thi and in the evaporator Evap at a temperature equal to or below Thi by heat exchange with a medium external to the machine, said medium having initially a temperature Thi. In the steady state, net work is consumed by the hydraulic pump HP, the condenser Cond continuously removes heat to the hot sink at high temperature Thi and heat is continuously consumed by the evaporator Evap, with extraction of heat from the external medium in contact with said evaporator Evap, the temperature Tlo of said external medium being strictly below Thi.
For heat production, in the initial state GT is maintained in the evaporator Evap at low temperature by heat exchange with the cold source at Tlo and GT is maintained in the condenser Cond at a temperature Thi≧Tlo by heat exchange with a medium external to the machine, said medium having initially a temperature ≧Thi. In the steady state, net work is consumed by the hydraulic pump HP, the cold source at Tlo continuously supplies heat to the evaporator Evap, the condenser Cond continuously delivers heat to the hot sink, the plant producing heat to the external medium in contact with said condenser Cond, the external medium having a temperature Thi>Tlo.
After the λα phase, the modified receiving Carnot machine of the 2nd type is in the α state of the cycle. The various thermodynamic transformations undergone by the fluid GT and the levels of the transfer liquid LT are given in Table 7. The states of the solenoid valves are given in Table 8, in which “x” means that the corresponding valve is open.










TABLE 7









Trans-
LT Level












Step
formation
Location
CT
CT′
ABCD





αβγ
3 → 4
ABCD
H → J
L → I
H → L



4 → 5
Evap + CT



1 → 2sv
CT′


γδ
5 → 1
Evap + CT
J → L
I → H
L → H



2sv → 3
CT′ + Cond + ABCD


δελ
3 → 4
ABCD
L → I
H → J
H → L



4 → 5
Evap + CT′



1 → 2sv
CT


λα
5 → 1
Evap + CT′
I → H
J → L
L → H



2sv → 3
CT + Cond + ABCD

















TABLE 8








Open solenoid valves



















Step
SV1
SV1′
SV2
SV2′
SV3
SV4
SVlo
SVhi
SVlo′
SVhi′
SVr
SVi





αβγ
x (to tβ)




x (to tβ)
x


x
x



γδ
x


x
x

x


x

x


δελ

x (to tε)



x (to tε)

x
x

x



λα

x
x

x


x
x


x









Work consumption is continuous over the duration of the cycle (excluding between the times tα and tβ on the one hand and tδ and tε on the other), but not always at constant power insofar as the pressure difference at the terminals of the hydraulic pump may vary. Of course, the average power over a cycle remains constant from one cycle to another, when a steady operating state is reached and if the temperatures Thi and Tlo remain constant. Moreover, the condenser is isolated from the rest of the circuit during the αβγ and δελ phases, whereas the removal of heat in the hot sink at Thi is a priori continuous. Under these conditions, during these isolation phases there will be a temperature drop and therefore a pressure drop in the condenser and then a sudden rise at times tγ and tλ upon the valve SV2 or the valve SV2′ reopening.
Since the transfer liquid LT is incompressible, the variations in level that occur simultaneously in the three chambers ABCD, CT and CT′ are not independent. Moreover, these variations in the level of LT result from or involve concomitant variations in the volume of the fluid GT. This is expressed by the following equation between the densities of GT at various stages of the cycle represented in FIG. 8:

ρ5−ρ3=ρ1−ρ2sv  (equation 2)

ρi being the density of GT in the thermodynamic state of the point “i”, “i” being the points 5, 3, 1 and respectively. Examples of curves at constant density are shown as dot-dash lines in FIG. 8.

Unlike the modified driving Carnot cycle of the 2nd type, here there is no limit to the temperature difference between the cold source at Tlo and the hot sink at Thi. Since the density at the point “3” is always the lowest of the cycle, the following double inequality again applies, irrespective of Thi and Tlo:

ρ4<ρ5<ρ1  (inequality 2)

In a modified receiving Carnot machine of the 1st type, the pressurization/expansion device is inserted in series between the condenser Cond and the evaporator Evap; it comprises a simple expansion device, such as for example an expansion valve EV or a capillary tube, and possibly in series a solenoid valve SV3. Such a device is shown in FIG. 9, in which the legends have the same meanings as in the other figures, and the combination of EV and SV3 constitutes the expansion device. The working fluid GT in the saturated liquid state leaving the condenser Cond is immediately expanded and introduced into the evaporator Evap. An example of such a modified receiving Carnot cycle of the 1st type is shown schematically by the 1-2sv-2g-3-4-5-1 cycle in the Mollier diagram of FIG. 10.
The various steps of the cycle and the states of the solenoid valves are explained in detail below and given in Tables 9 and 10. The solenoid valve SV3 is not essential since, when the machine is in operation, it is always open. Its only benefit is to be able to isolate the condenser from the evaporator on stopping the machine.











TABLE 9









Trans-
LT Level














Step
formation
Location
CT
CT′







αβ
3 → 4
Between Cond
H→J
L→I





and Evap




4 → 5
Evap + CT




1 → 2sv
CT′



βγ
5 → 1
Evap + CT
J→L
I→H




2sv → 2g → 3
CT′ + Cond



γδ
3 → 4
Between Cond
L→I
H→J





and Evap




4 → 5
Evap + CT′




1 → 2sv
CT



δα
5 → 1
Evap + CT′
I→H
J→L




2sv → 2g → 3
CT + Cond


















TABLE 10








Open solenoid valves
















Step
SV1
SV1′
SV2
SV2′
SV3
SVlo
SVhi
SVlo′
SVhi′





αβ
x



x
x


x


βγ
x


x
x
x


x


γδ

x


x

x
x



δα

x
x

x

x
x









The steps of the modified receiving Carnot cycle Of the 1st type are explained in detail below when they differ from those described above in the case of the modified receiving Carnot cycle of the 2nd type.
Starting from an initial state in which all the communication circuits for the working fluid GT and for the transfer liquid LT are closed off, at time t0 the hydraulic pump HP is actuated and the GT circuit between Cond and Evap is opened (by SV3) and GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
αβ Phase (Between Times tα and tβ):
At the instant immediately preceding tα, the level of LT is high (denoted by H) in the cylinder CT and low (denoted by L) in the cylinder CT′. At the same instant, the saturation vapor pressure of GT has a high value Phi in Cond and CT and a low value Plo in Evap and CT′. It is this instant of the cycle which is shown schematically in FIG. 9.
At time tα, the opening of the solenoid valves SV1, SV3. SVlo and SVhi′, has the following consequences:

    
    
        the saturated vapor of GT leaving the evaporator at Plo enters CT and delivers the transfer liquid LT to an intermediate level (denoted by J). LT is taken in by the pump HP which pressurizes it, thereby consuming work;
        after having been pressurized by HP, the transfer liquid LT is delivered in CT′. In CT′, LT passes from the low level to the intermediate level (denoted by I) and isentropically compresses the GT vapor contained in this chamber; and
        following the opening of SV3, the working fluid GT in the saturated liquid state and at high pressure Phi is expanded by the valve EV and then introduced in the two-phase mixture state into the evaporator Evap, thereby compensating in terms of mass for the discharge of gaseous GT into CT.
    
    


In the Mollier diagram (shown in FIG. 10), this step corresponds to the following simultaneous transformations:
the 3→4 transformation between Cond and Evap;
the 4→5 transformation in the Evap-CT assembly; and
the 1→2sv transformation in CT′.
As previously, the working fluid GT used is supposed to end up, after this isentropic transformation, in the superheated vapor domain.
From an energy standpoint, during this αβ phase, heat Q45 has been pumped into the evaporator at Tlo and work Wαβ has also been consumed by the pump HP. This work has been delivered by the outside at increasing power since the pressure upstream of the pump remains practically constant (=Plo), whereas the downstream pressure increases up to Phi.
βγ Phase (Between Times tβ and tγ):
At time tβ, that is to say when the level of LT has reached the predefined values (J in CT and I in CT′), SV1, SV3, SVlo and SVhi′ are left open and the solenoid valve SV2 is opened. As a result, the GT vapor continues to be produced in the evaporator and to expand in CT (5→1 transformation), thereby again delivering the transfer liquid taken up by the Pump into the cylinder CT′, which this time is connected to the condenser. The GT vapor contained in CT′ is desuperheated (i.e. the 2sv→2g transformation partly in CT′) and condenses completely in the condenser (2sv→2g→3 transformation). The fluid GT in the saturated liquid state is expanded by EV and introduced into the evaporator.
From an energy standpoint, during this βγ phase, heat Q51 is pumped into the evaporator at Tlo, heat Q23 is released into the condenser at Thi (where Thi>Tlo), thereby requiring work Wγδ delivered by the outside. This work is at a virtually constant power since the pressures upstream and downstream of the pump are also practically constant (with nonlimiting heat exchangers at the condenser and the evaporator).
At time tγ, one half of the cycle has been completed. The other half is symmetric: the evaporator and the condenser are the sites for the same successive transformations, while the roles of the chambers CT and CT′ are reversed.
γδ Phase (Between Times tγ and tδ) and δα Phase (Between Times tδ and tα):
These phases are equivalent to the αβ phase and to the βγ phase respectively, but with the transfer chambers CT and CT′ reversed.
More particularly:

    
    
        at time tγ, all the circuits open at time tβ are closed, except for the GT circuit between Cond and Evap, the LT circuit enabling LT to be transferred from CT′ to CT passing via the hydraulic pump HP is opened (by SVlo and SVhi) and the GT circuit between Evap and CT′ is opened (by SV1′) so that:
        
            LT is taken in by the pump HP, which pressurizes it and delivers it into CT;
            the level of LT in CT passes from the low level to an intermediate level I, and in CT′ from the high level to an intermediate level J;
            since the volume occupied by the GT vapor in CT′ increases, the working fluid GT evaporates in Evap and the saturated vapor of GT leaving Evap at the low pressure Plo enters CT′;
            the GT vapor contained in CT is adiabatically compressed up to the high pressure Phi; and
            GT in the saturated or supercooled liquid state in Cond and at the high pressure Phi is expanded isenthalpically and introduced in the liquid/vapor two-phase mixture state and at the low pressure Plo into the evaporator Evap;
        
        
        at time tδ, the GT circuit between CT and Cond is opened (by SV2) so that:
        
            LT is again taken in by the pump HP, which pressurizes it and delivers it into CT;
            the level of LT in CT passes from the intermediate level I to the high level and in CT′ from the intermediate level J to the low level;
            because the volume occupied by the GT vapor in CT′ continues to increase, GT evaporates in Evap and the saturated GT vapor leaving Evap at the low pressure Plo enters CT′; and
            the GT vapor contained in CT, at the high pressure Phi, is delivered by LT and condenses in Cond.
        
        
    
    


After several cycles, the plant operates in a steady state.
As regards refrigeration: in the initial state, GT is maintained in the condenser Cond at high temperature by heat exchange with the hot sink at Thi and in the evaporator Evap at a temperature equal to or below Thi by heat exchange with a medium external to the machine, said medium having initially a temperature equal to or below Thi; and in the steady state, net work is consumed by the hydraulic pump HP, the condenser Cond continuously removes heat to the hot sink at high temperature Thi and heat is continuously consumed by the evaporator Evap, that is to say heat is extracted from the external medium in contact with said evaporator Evap, the temperature Tlo of said external medium being strictly below Thi.
As regards heat production: in the initial state, GT is maintained in the evaporator Evap at low temperature by heat exchange with the cold source at Tlo, and in the condenser Cond at a temperature equal to or above Thi by heat exchange with a medium external to the plant at a temperature equal to or above Thi; and, in the steady state, net work is consumed by the hydraulic pump HP, the cold source at Tlo continuously supplies heat to Evap, and Cond continuously removes heat to the hot sink, that is to say there is heat production to the external medium in contact with Cond, the temperature Thi of said external medium being strictly above Tlo.
In this configuration (called the receiving configuration of the 1st type), equation (2) and inequality (2) linking the densities of GT in the various steps of the cycle are still valid.
The modified receiving Carnot machine of the 1st type is simpler in its operation and comprises fewer constituent elements. However, as in the case of a conventional mechanical vapor compression cycle, the 3→4 and 2sv→2g transformations generate a few irreversibilities, this having an unfavorable effect on the coefficient of performance or coefficient of amplification of the cycle. However, since this degradation is moderate, the configuration of the 1st type is preferred for the modified receiving Carnot machine. This is because, although the modified receiving Carnot machine of the 1st type is similar to conventional mechanical vapor compression machines, it still retains two key advantages:

    
    
        the adiabatic compression step (1→2sv) has a higher isentropic compression efficiency, it is less noisy and more reliable; and
        the same machine, by slight modifications, may operate in driving mode, something which is not possible with the machines of the prior art.
    
    


The choice of one or other type of receiving machine will be made according to the means available, especially according to the temperature of the heat source and heat sink, the working fluid GT and the intended result.
The same modified Carnot machine may provide, alternately, depending on the user's choice, either the driving function or the receiving function. In such a case, said modified Carnot machine is termed a “multipurpose” machine. This possibility means that the machine possesses the constituent elements necessary for satisfying each of the two (driving or receiving) operating modes as described above and additional elements for switching from one mode to the other, the two modes not being able to operate simultaneously. Many constituent elements necessary for each mode may be the same, namely the elements Cond, Evap, CT, CT′, most of the controlled valves and certain portions of the GT and LT circuits. It is therefore unnecessary to duplicate these elements in the multipurpose modified Carnot machine. Other elements are specific to one particular mode. For example, the device PED, combining the chamber ABCD with the solenoid valves SV3 and SV4, as described in FIG. 2, allows the machine to operate in driving mode of the 2nd type but not to operate in the receiving mode of the 2nd type, as described in FIG. 7. The converse is not true, that is to say the device PED combining the chamber ABCD with the solenoid valves SV3 and SV4, as described in FIG. 7, does allow the machine to operate in receiving mode of the 2nd type or in driving mode of the 2nd type. A second example of the incompatibility of usage in the two modes also relates to the PED devices, but for the modified Carnot machines of the 1st type: the auxiliary hydraulic pump AHP1 (FIG. 5) cannot provide the function of expanding the working fluid, like the expansion valve EV or the capillary tube C (FIG. 9), and vice versa. Likewise, the hydraulic converter is either a pump or a motor. However, there are converters that can provide both functions, depending on the direction of flow of the fluid.
FIG. 11 shows schematically a multipurpose modified Carnot machine that can provide, depending on the user's choice, either the function of a modified driving Carnot machine of the 1st type or the function of a modified receiving Carnot machine of the 1st type. The other three combinations of the two types are also possible, namely driving and receiving modes of the 2nd type, driving mode of the 1st type and receiving mode of the 2nd type, and driving mode of the 2nd type and receiving mode of the 1st type. To select the operating (driving or receiving) mode requires no sophisticated means. For example, in FIG. 11, the solenoid valves SV3D and SV3R are open and closed, or closed and open respectively, if the driving mode or the receiving mode is selected respectively. These two solenoid valves SV3n and SV3R may be replaced by a three-way valve. Finally, again in this example shown in FIG. 11, the hydraulic pump and the hydraulic motor are considered as two separate hydraulic converters. Depending on the operating mode selected, namely driving or receiving mode, one or other of the converters is active according to the opening of the three-way solenoid valve SVRD, it being possible for said solenoid valve SVRD to be replaced by two two-way solenoid valves or any other actuator in the transfer liquid circuit.
In one particular embodiment, a modified Carnot machine may be coupled to a complementary device, by thermal coupling or by mechanical coupling.
A modified driving or receiving Carnot machine according to the invention may be thermally coupled at its condenser and/or its evaporator to a complementary device. The thermal coupling may be achieved by means of a heat-transfer fluid or a heat pipe, or by direct contact or by radiation.
The complementary device may be a driving or receiving thermodynamic machine. The two most advantageous cases relate to the coupling of a modified driving Carnot machine to a driving thermodynamic machine or the coupling of a modified receiving Carnot machine to a receiving thermodynamic machine. In both cases, the driving thermodynamic machine or the receiving thermodynamic machine receives heat from the condenser of the modified driving Carnot machine or the modified receiving Carnot machine respectively or gives heat to the evaporator of the modified driving Carnot machine or the modified receiving Carnot machine respectively. Said driving or receiving thermodynamic machines may be a second modified driving Carnot machine (of the 1st type or of the 2nd type) or a modified receiving Carnot machine different from the first one (of the 1st type or of the 2nd type).
One mode of thermally coupling two modified driving Carnot machines is illustrated schematically in FIGS. 12a and 12b. FIG. 12a shows the temperature levels of the heat sources and heat sinks and the direction of heat exchange and work exchange between the machines or with the environment. A first, high-temperature (HT) machine operates between a heat source at the temperature Thi and a heat sink at the intermediate temperature Tm1 and contains a working fluid GT1. A second, low-temperature (LT) machine operates between a heat source at Tm2 and a heat sink at the temperature Tlo, and it contains a working fluid GT2. The temperatures are such that Thi>Tm1>Tm2>Tlo>Tambient. If the heat transfers at the condenser of the HT machine and the evaporator of the LT machine are infinitely efficient (because of an infinite exchange area and/or infinite exchange coefficients), the temperatures Tm1 and Tm2 are practically equal. In all cases, in this combination called a “thermal cascade” combination, the amount of heat Qhi is delivered to the HT machine at the temperature Thi in order to evaporate the fluid GT1, the amount of heat Qm1 released by the condensation of GT1 in the condenser of the HT machine at the temperature Tm1 is entirely transferred (Qm1=Q2) or partially transferred (Qm1>Qm2) to the evaporator of the LT machine to evaporate the fluid GT2 at the temperature Tm2, and the heat Qlo produced at the temperature Tlo by the condensation of the fluid GT2 is transmitted to the environment. When only work production is required, the heat transfer between the source at Tm1 and the sink at Tm2 is complete, that is to say there is equality between Qm1, and Qm2, denoted simply by Qm, in this case. When work and heat cogeneration is desired at a sufficient temperature level such as Tm1, then the heat transfer between the source at Tm1 and the sink at Tm2 is partial, that is to say Qm1 is greater than Qm2 and the difference is delivered to the user.
Optionally, the working fluids GT1 and GT2 may be identical. In parallel, the amounts of work W1 and W2 are delivered by the HT machine and the LT machine respectively. The overall efficiency ((W1+W2)/Qhi) of the cascaded combination of the two modified driving machines is not necessarily equal to, but in general somewhat lower than, that of a modified driving Carnot machine alone operating between the same extreme temperatures Thi and Tlo, as shown schematically in FIG. 12b. In fact, these two efficiencies are the same under the quadruple conditions that the two modified Carnot machines are of the 2nd type and operate ideally, that is to say with no irreversibilities, that the temperatures Tm1 and Tm2 are coincident and that there is integral heat recovery (Qm1=Qm2) at this intermediate temperature Tm.
The thermally cascaded combination of modified driving Carnot machines may involve machines of the same (1st or 2nd) type or machines of different types.
A first advantage of the cascaded combination of two modified driving Carnot machines of the 2nd type lies in the fact that the temperature difference Thi−Tlo is no longer limited as when a single modified driving Carnot machine of the 2nd type is used (due to the condition on the densities expressed by equation (1)). Thus, the overall efficiency of the cascaded combination may again become higher than that of the single machine when the difference (Thi−Tlo) of said combination becomes greater than the maximum difference permitted for said single machine.
A second advantage of the cascaded combination of two modified driving Carnot machines of the 1st or 2nd type is that the pressure of each of the working fluids GT1 and GT2 is lower than that of the working fluid of the single modified driving Carnot machine (of the 1st or 2nd type) operating between the same extreme temperatures Thi and Tlo.
Cascaded coupling may be achieved using more than two modified driving Carnot machines according to the same principle. The first machine is supplied with heat at the highest temperature Thi to evaporate a working fluid, and the last machine of the cascade releases the heat, generated by condensation at the lowest temperature Tlo, into the environment, Tlo nevertheless being above the temperature of said environment. Between these two extreme machines, each intermediate machine receives the heat released by the condensation of the working fluid of the preceding machine and transfers the heat released by the condensation of its own working fluid to the machine that follows it. Each machine delivers an amount of work to the environment.
Two modified receiving Carnot machines may be coupled in cascade in a manner similar to that described above in the case of the driving machines. The work flux and the heat flux are in the opposite directions to those shown in FIG. 12a. 
The cascaded combination of two modified receiving Carnot machines has the not insignificant advantage of reducing the pressure of each of the working fluids GT1 and GT2 relative to that of the working fluid found in the case of a single modified receiving Carnot machine, whether of the 1st type or the 2nd type, operating between the same extreme temperatures Tlo and Thi.
A modified Carnot machine according to the invention may be mechanically coupled to a complementary device at the hydraulic motor if the machine is a driving machine or at the hydraulic pump if the machine is a receiving machine. The mechanical coupling may be achieved for example by means of a belt, a universal joint, a magnetic or nonmagnetic clutch, or directly onto the shaft of the hydraulic motor or of the hydraulic pump.
The complementary device may be a driving device, for example an electric motor, a hydraulic turbine, a wind turbine, a petroleum-driven engine, a gas-driven engine, a diesel engine, or another modified driving Carnot machine.
The complementary device may be a receiving device, for example a hydraulic pump, a transport vehicle, an alternator, a mechanical vapor compression heat pump, an air compressor, or another modified receiving Carnot machine.
The complementary device may also be a driving/receiving device, such as a flywheel for example.
One particularly preferred method of implementing mechanical coupling consists in coupling a modified driving Carnot machine to a modified receiving Carnot machine.
A first embodiment of a plant comprising a modified driving Carnot machine mechanically coupled to a modified receiving Carnot machine is shown schematically in FIG. 13 together with the temperature levels of the heat sources and heat sinks and the direction of heat exchange and work exchange.
The driving machine contains a working fluid GT1. It receives an amount of heat Qhi from a source at the temperature Thi, it releases an amount of heat QmD at a temperature TmD and work W. The temperature Thi of the source is necessarily above the temperature TmD of the heat sink.
The receiving machine contains a working fluid GT2. It releases an amount of heat QmR at a temperature TmR. It receives an amount of heat Qlo from a source at the temperature Tlo and the work W released by the driving machine. The temperature Tlo of the source is necessarily below the temperature TmR of the heat sink.
The two main applications intended by such a combination, which uses only heat at Thi as single energy source, are:

    
    
        refrigeration production at Tlo: in this case Tlo<Tambient≦TmR; and
        heat production at TmR and TmD: for example for heating a dwelling, that is to say when Tlo is the ambient temperature on the outside Tambient—outside, the two average temperatures LmD and TmR are equal and the coefficient of amplification (QmR+QmD)/Qhi is greater than 1.
    
    


A second embodiment of a plant comprising a modified driving Carnot machine mechanically coupled to a modified receiving Carnot machine is shown schematically in FIG. 14 together with the temperature levels of the heat sources and the heat sinks and the direction of heat exchange and work exchange.
The driving machine contains a working fluid GT2. It receives an amount of heat QmD from a source at the temperature Tm, it releases an amount of heat Qlo at a temperature Tlo and work W. The temperature Tm of the source is necessarily above the temperature Tlo of the heat sink.
The receiving machine contains a working fluid GT1. It releases an amount of heat Qhi at a temperature Thi. It receives an amount of heat QmR from the source at the temperature Tm and work W released by the driving machine. The temperature Tm of the source is necessarily below the temperature Thi of the heat sink.
Such a plant according to the invention makes it possible to obtain an amount of heat at a higher temperature than the temperature of the available heat source without consuming work delivered by the environment. This application is particularly advantageous when there is discharge of unutilized heat and when heat is required at a higher temperature.
A plant according to the present invention may be used to produce, from a heat source, electricity, heat or refrigeration. Depending on the application in question, the plant comprises a modified driving Carnot machine or a modified receiving Carnot machine associated with an appropriate environment. The working fluid and the hydraulic transfer liquid are chosen according to the desired objective, the temperature of the available heat source and the temperature of the available heat sink.
A modified receiving Carnot machine may be used in the entire field of refrigerating machines and heat pumps: freezing, refrigeration, “reversible” air conditioning, that is to say cooling in summer and heating in winter.
Conventional MVC (mechanical vapor compression) refrigerating machines are reputed to have a good coefficient of performance COP (=Qlo/W) or a good coefficient of amplification COA (=Qm/W). In fact, these coefficients are much lower (by about 50%) than those of the Carnot machine and therefore of the modified receiving Carnot machine of the present invention, in particular of the 2nd type, and to a lesser extent of the 1st type. By replacing current MVC machines with modified receiving Carnot machines it is possible to reduce the electrical energy needed to meet the same requirements.
As in the case of conventional CMV heat pumps, the reasonable pressure range for the working fluid GT of a modified receiving Carnot machine lies between 0.7 bar and 10 bar approximately. At pressures below 0.7 bar, the size of the pipes between the transfer cylinder and the evaporator and, most particularly, the volume of the transfer cylinder itself would become too large. Conversely, at pressures above 10 bar, safety and material strength problems arise. The use of alkanes or HFCs is very suitable for these applications. For example, isobutane has already been used in current refrigerators or freezers (since isobutane has no effect on the ozone layer). The transfer liquid that may be associated with these alkanes in a modified receiving Carnot machine for refrigerating applications is water. For refrigerating below 0° C., it would however be necessary in this case to insert a membrane between GT and LT so as to prevent any icing from obstructing the interior of the evaporator or to envisage regular deicing operations and devices for returning LT to the transfer chambers. Instead of water as transfer liquid, it is also conceivable to use an oil in which the chosen working fluid GT is weakly miscible.
The modified driving Carnot machines may be used for centralized or dispersed electricity generation, work production for pumping water, seawater desalination, etc., or the production of work for a dithermal receiving machine, i.e. one for the purpose of heating or for refrigerating, and in particular a modified receiving Carnot machine.
The advantages of a modified driving Carnot machine and those of a modified receiving Carnot machine may be added together by combining the two machines. Indeed, the mechanical-electrical conversion is then no longer necessary, thereby obviating the slight loss of efficiency that such a conversion involves.
A plant according to the invention may be used for the centralized generation of electricity from a centralized high-temperature heat source, for example produced by a nuclear reaction. A nuclear reaction produces heat at 500° C. The use of this heat involves either the use of a driving fluid compatible with this high temperature or the implementation of an intermediate step using a steam turbine, the steam being superheated to between 500 and 300° C. and the heat at 300° C. then being delivered to a modified driving Carnot machine that operates between this heat source at 300° C. and the cold sink of the external environment. With such a temperature difference, it is necessary for at least two modified driving Carnot machines involving different working fluids to be thermally cascaded. For the machine at the highest temperature, water is best suited as working fluid. In this configuration, the advantage afforded by the invention is that the overall electrical generation efficiency is better than that of current nuclear power stations.
An installation according to the invention may be used for decentralized electricity generation, using solar energy as heat source, this being renewable and available everywhere, albeit intermittent and quite dilute (with a maximum of about 1 kW/m2 in fine weather). Current cylindro-parabolic solar collectors may bring the driving fluid to about 300° C. Compared with centralized generation, the work delivered by the turbine between 500 and 300° C. is lost but only a renewable energy source is used.
It is also possible to use thermal solar energy delivered at lower temperatures, such as about 130° C., with vacuum tube collectors or about 80° C. with flat collectors. Obviously the lower the temperature of the hot source, the lower the efficiency of the modified driving Carnot machine. However for the lowest temperature Thi, that delivered by flat solar collectors, a thermally cascaded combination is no longer necessary; the modified driving Carnot machine is then simpler and therefore less expensive. When the sun is not shining, an auxiliary boiler may supply the necessary heat.
A plant according to the invention may be used to convert heat into work, without necessarily converting it into electricity. The mechanical work may be used directly, for example for a hydraulic pump or for a heat pump, the compressor of which is not driven by an electric motor. In the latter case, the end results are:

    
    
        heat production at a temperature Tm below that of the hot source at Thi but with a coefficient of amplification greater than 1, or at a temperature Thi above that of the hot source at Tm, but with a coefficient of amplification less than 1, said coefficients of amplification being greater than those of the prior art using adsorption or absorption systems; and
        refrigeration at a temperature Tlo (below room temperature) and with a coefficient of performance greater than that of the prior art using adsorption or absorption systems.
    
    


The present invention is illustrated by the following eight examples to which the invention is not however limited. FIGS. 15a to 15h show schematically, for each of the examples, the heat exchange and work exchange between the modified Carnot machine (or combinations of said machines) and the environment, and also the temperatures of the heat sources and heat sinks.

    Example 1 (FIG. 15a): three thermally cascaded modified driving Carnot machines of the 2nd type;
    Example 2 (FIG. 15b): two thermally cascaded modified driving Carnot machines of the 1st type;
    Examples 3 and 4 (FIGS. 15c and 15d): modified receiving Carnot machines of the 2nd or 1st type;
    Example 5 (FIG. 15e): two thermally cascaded modified receiving Carnot machines of the 1st type;
    Examples 6 and 7 (FIGS. 15f and 15g): mechanical coupling between a high-temperature modified driving Carnot machine of the 1st type and a low-temperature modified receiving Carnot machine of the 1st type; and
    Example 8 (FIG. 15h): mechanical coupling between a low-temperature modified driving Carnot machine of the 1st type and a high-temperature modified receiving Carnot machine of the 1st type.


In these examples, three working fluids GT are used, namely water (denoted by R718), n-butane (denoted by R600) and 1,1,1,2-tetrafluoroethane (denoted by R134a). The Mollier diagrams for these three fluids are shown in FIGS. 16, 17 and 18 respectively. Plotted in these diagrams are the various modified Carnot cycles that are involved in the abovementioned examples 1 to 8.
Example 1
Thermally Cascaded Combination of Three Modified Driving Carnot Machines of the 2nd Type
The objective is to produce work (which can be converted to electricity) with the best efficiency possible. For a given cold sink temperature (Tlo=40° C.), the efficiency will be higher the higher the temperature Thi of the hot source and the closer the machine cycle is to the ideal Carnot cycle. The modified driving Carnot cycle of the 2nd type is therefore used in its preferred configuration, that is to say by satisfying the constraint whereby the density of the working fluid leaving the condenser is the same as that leaving the evaporator (as described in FIG. 4).
With a heat source at Thi3 of 85° C., the working fluid used is 8600 and this describes the a-b-c-d-a cycle shown in FIG. 17. It should be noted that with this fluid, the c→d adiabatic expansion results in the vapor being in the superheated domain, but nevertheless very close to the saturation curve. The irreversibility is very low. The efficiency η3 of this cycle is 12.49% compared with 12.56% for a perfect Carnot cycle between the same temperatures.
With a heat source at Thi2 of 175° C. and in thermal cascade with the preceding cycle, the working fluid used is R718 and this describes the e-f-g-h-e cycle shown in FIG. 16. It should be noted that with this fluid, the g→h adiabatic expansion results in the fluid being in the two-phase domain and therefore causes no irreversibility. The efficiency η2 of this cycle is coincident with that of a Carnot cycle, therefore 16.7%.
Finally, with a heat source at Thi1 of 275° C. and in thermal cascade with the preceding cycle, the working fluid used is again R718, and this describes the a-b-c-d-a cycle shown in FIG. 16. The c→d adiabatic expansion again results in the two-phase domain. The efficiency η1 of this cycle is 16.4%.
The thermally cascaded combination of these three modified driving Carnot machines of the 2nd type (FIG. 15a), with realistic temperature differences at the heat transfer level between the various machines, results in the following overall efficiency:

η=(W1+W2+W3)/Qhi=η1+η2(1−η1)+η3(1−η2)(1−η1)

giving η=39.10%, i.e. 91% of the efficiency of the Carnot machine operating between the same extreme temperatures.
This efficiency is better than that of current nuclear power stations (≈34%) which nevertheless work with superheated steam at much higher temperatures (≈500° C.). Furthermore, the heat source at Thi1 (=275° C.) could be supplied by cylindro-parabolic solar collectors.
Example 2
Thermally Cascaded Combination of Two Modified Driving Carnot Machines of the 1st Type
As for the previous example, the objective is to produce work (which can be converted to electricity) but with a simpler machine using combinations of modified driving Carnot machines of the 1st type. The temperature differences between the heat source and the heat sink are no longer limited by the constraint of the density of the working fluid leaving the condenser having to be the same as that leaving the evaporator. However, excessively large pressure differences generate other technological problems; thus, using the same extreme heat source and heat sink (275° C. and 40° C.), it is preferable for two machines to be thermally cascaded rather than to have a single machine operating over such a large pressure difference.
The thermal cascading (FIG. 15b) consists in coupling two modified driving Carnot machines of the 1st type: the first uses water (R718) as working fluid and describes the i-j-b-c-k-i cycle shown in FIG. 16, while the second uses n-butane (R600) as working fluid and describes the e-f-b-c-d-e cycle shown in FIG. 17.
Steps j→b and f→b of these two cycles cause additional irreversibilities, but the efficiencies of the two cycles nevertheless remain very satisfactory (in comparison with the Carnot efficiency): η1=27.47% for the cycle with R718 and 12=10.82% for the cycle with R600.
The overall efficiency of the thermally cascaded combination (FIG. 15b) of these two modified driving Carnot machines of the 1st type is:

η=(W1+W2)/Qhi=η1+η2(1−η1)

i.e. η=35.32% (82% of the efficiency of the Carnot machine operating between the same extreme temperatures).

Compared with the previous example, for quite a small degradation in the efficiency (−3.78%), the simplification of the machine is relatively substantial: two combined machines instead of three, and most particularly those of the 1st type which are simpler than those of the 2nd type.
Example 3
Modified Receiving Carnot Machines of the 2nd or 1st Type
The intended objective in Example 3 is the heating of a dwelling by low-temperature emitters (radiators or underfloor heating). A modified receiving Carnot machine operating between 5 and 50° C. is very suitable for this application (FIG. 15c).
The two possible options, that the machines of the 2nd type or the machines of the 1st type constitute, using R600 as working fluid, are compared.
With a modified receiving Carnot machine of the 2nd type, the cycle described is the 1-2-3→4′-9-1 cycle shown in FIG. 17. With this fluid, if the adiabatic compression step had been carried out starting from the saturated vapor, that is to say the point “9” of this cycle, said fluid at the end of this step would have been in the two-phase domain, which is not a drawback. As an illustration in this example, it is chosen to superheat the fluid slightly (i.e. step 9→1) such that there is only saturated vapor at the end of compression (point “2” of the cycle). This implies, during said step, a supply of heat, for example at the transfer cylinders as illustrated in FIG. 2 for a modified driving Carnot machine.
The coefficient of amplification of this modified receiving Carnot machine describing this cycle is:

COA=Qhi/W=7.18.

This COA is virtually the same as that of the Carnot machine operating between the same extreme temperatures since the irreversibility caused by the 9→1 superheating is very small.
However, the machine of the 2nd type requires the chamber ABCD and the associated connections, incurring a cost and involving more complex management of the cycle. With a modified receiving Carnot machine of the 1st type, the cycle described is the 1-2-3-4-9-1 cycle shown in FIG. 17. The COA of this machine of the 1st type is lower: COA=Qhi/W=6.06, i.e. 84% of the COA of the Carnot machine, but it nevertheless remains much better than the COA values for current MVC machines operating between the same extreme temperatures.
Example 4
Modified Receiving Carnot Machine of the 1st Type
The intended objective in Example 4 is to cool a dwelling in summer.
A modified receiving Carnot machine of the 1st type operating between 15 and 40° C. is very suitable for this application (FIG. 15d). The working fluid used (R600) describes the 5-6-7-8-5 cycle shown in FIG. 17. Compared with the previous example, it is chosen not to superheat the fluid before the isentropic compression step. The coefficient of performance of this modified receiving Carnot machine describing this cycle is:
COP=Qlo/W=10.33, i.e. 90% of the COP of the Carnot machine and in particular much better than the COP values of current MVC machines operating between the same extreme temperatures.
Example 5
Thermally Cascaded Combination of Two Modified Receiving Carnot Machines of the 1st Type
The intended objective in Example 5 is low-temperature refrigeration (for freezing purposes). Even though the temperature difference between the heat source and heat sink is not limited by any constraint on the densities of the working fluid being equal, it is preferable for there not to be too high a pressure difference in the machine as this generates other technological problems. Thus with the cold source at −30° C. and the hot sink at 40° C., it is preferable for two machines to be thermally cascaded rather than providing a single machine operating over such a large temperature difference. The thermal cascading (see FIG. 15e) consists in coupling two modified receiving Carnot machines of the 1st type: the first uses R600 as working fluid and describes the 9-6-7-10-9 cycle shown in FIG. 17 and the second uses R134a as working fluid and describes the 1-2-3-4-1 cycle shown in FIG. 18.
The overall coefficient of performance of the thermally cascaded combination of these two modified receiving Carnot machines of the 1st type is:

COP=Qlo/(W1+W2)=1/[1/COP2+(1+1/COP2)/COA1].

This gives COP=2.85, i.e. 82% of the COP of the Carnot machine and above all much better than the COP values of current two-stage MVC machines operating between the same extreme temperatures.
Example 6
Mechanical Coupling Between a High-Temperature Modified Driving Carnot Machine of the 1st Type and a Low-Temperature Modified Receiving Carnot Machine of the 1st Type
The intended objective in Example 6 (FIG. 150 is to cool a dwelling in summer using as energy source only heat, for example coming from solar collectors. To do this, a first machine—the modified driving Carnot machine of the 1st type using the working fluid R600, described in Example 2—is coupled to a second machine, the modified receiving Carnot machine of the 1st type described in Example 4.
The coefficient of performance of this combination (FIG. 15f) is: COP=Qlo/Qhi=η1COP2=1.29, i.e. 89% of the COP of the trithermal Carnot machine and most particularly much better than the COP values for adsorption or absorption trithermal systems of the current prior art operating between the same heat sources and sinks.
Example 7
Mechanical Coupling of a High-Temperature Modified Driving Carnot Machine of the 1st Type and a Low-Temperature Modified Receiving Carnot Machine of the 1st Type
The intended objectives in Example 7 (FIG. 15g) are several:

    
    
        cogeneration of work which can be converted to electricity and heat useful for (low-temperature) heating of a dwelling in winter;
        “low-temperature” air conditioning, i.e. compatible with conventional fan-coil units for buildings (especially offices or flats),

in all cases using as energy source only heat at a temperature achievable by a boiler or by cylindro-parabolic solar collectors.

    
    


For these practical objectives, a first machine—the modified driving Carnot machine of the 1st type using the working fluid R718, which describes the l-m-g-n-l cycle shown in FIG. 16—is coupled to a second machine, the modified receiving Carnot machine of the 1st type described in Example 3.
The efficiency η1 of the first machine is 25.34% (i.e. 91% of the Carnot efficiency), this being much higher than the current efficiency of photovoltaic solar collectors.
Although the electricity is not recovered for the receiving machine (FIG. 15g), the production of heat Qm1 supplements the electricity generation, i.e. 24.66% of the incident energy Qhi, whereas photovoltaic cells themselves deliver no heat. In the opposite case, that is to say for just heating and/or air conditioning applications, the coefficients of amplification and performance of this combination are joined to the COP and efficiency values of the two machines, as:

COA=COP+1=COP2×η1+1,

giving, respectively, COA=2.28 (84% of the Carnot COA) and COP=1.28 (74% of the Carnot COA).

Example 8
Mechanical Coupling Between a Low-Temperature Modified Driving Carnot Machine of the 1st Type and a High-Temperature Modified Receiving Carnot Machine of the 1st Type
The intended objective in Example 8 (FIG. 15h) is steam production at moderate pressure (2 bar), having, as sole energy source, “low-temperature” (85° C.) heat incompatible with direct production of said vapor. This is one example among others conventionally encountered on industrial sites where unutilized heat is discarded and where higher temperatures are required.
This thermotransformation objective between 85 and 120° C. (capable of generating vapor at 2 bar) may be carried out by mechanically coupling a first machine, namely the modified receiving Carnot machine of the 1st type, using R718, operating between 85 and 120° C. and describing the 1-2-3-4-1 cycle shown in FIG. 16, to a second machine, the modified driving Carnot machine of the 1st type, operating between 85° C. and 40° C. (which temperature is above the ambient temperature), using the working fluid R600 and described in Example 2.
The coefficient of performance COP1 of the first (receiving) machine is 9.14 (89% of the COP of the dithermal Carnot machine). It should be noted that with water as working fluid, the steam at the end of the isentropic compression step is highly superheated (T2=208° C.>>120° C.).
The overall coefficient of performance of the combination of the two machines (FIG. 15h) satisfies the equation:

COP=Qhi/(Qm1+Qm2)=(COP1+1)/(COP1+1/η2),

giving, with these source and sink temperatures: COP=55.2% (89% of the COP of the trithermal Carnot machine).

The various examples described above confirm that one and the same working fluid may be used as driving fluid or as receiving fluid, depending on the plant and the intended objective.
The fluid n-butane (R600) describes a driving cycle of the 1st type in Example 2 (FIG. 15b) and a receiving cycle of the 1st type in Example 7 (FIG. 15g) and the modified Carnot machine, of the driving and receiving type respectively, which uses this fluid R600 is combined in these two examples with another Carnot machine, of the driving type in this case, using water (R718) as working fluid. Consequently, it may be deduced from this that a plant according to the present invention may comprise a driving Carnot machine of the 1st type (with R718 as working fluid) coupled to a multipurpose modified Carnot machine (such as that described in FIG. 11, with R600 as working fluid) and that such a plant may be employed for applications as different as that intended in Example 2 and that intended in Example 7.

## Claims

1. A refrigeration, heat or work production plant, comprising at least one modified Carnot machine formed by:
a) a 1st assembly that comprises an evaporator (Evap) associated with a heat source, a condenser (Cond) associated with a heat sink, a device (PED) for pressurizing or expanding a working fluid GT, means for transferring the working fluid GT between the condenser (Cond) and the (PED) and between the evaporator (Evap) and the (PED);
b) a 2nd assembly that comprises two transfer chambers (CT) and (CT′) that contain a transfer liquid LT and the working fluid GT in liquid and/or vapor form, the transfer liquid LT and the working fluid being two different fluids;
c) means for the selective transfer of the working fluid GT between the condenser (Cond) and each of the transfer chambers (CT) and (CT′) on the one hand, and between the evaporator (Evap) and each of the transfer chambers (CT), and (CT′) on the other; and
d) means for the selective transfer of the liquid LT between the transfer chambers (CT) and (CT′) and the compression or expansion device (PED), said means comprising at least one hydraulic converter.

2. The plant as claimed in claim 1, in which the modified Carnot machine is a driving machine, wherein the hydraulic converter is a hydraulic motor and the heat source is at a temperature above that of the heat sink, and in that the (PED) is a device that pressurizes the working fluid GT, which is in the saturated liquid or supercooled liquid state.

3. The plant as claimed in claim 1, in which the modified Carnot machine is a driving machine, wherein the hydraulic converter is a hydraulic motor and the heat source is at a temperature above that of the heat sink, and in that the (PED) device comprises, on the one hand, a compression/expansion chamber (ABCD) and the transfer means associated therewith and, on the other hand, an auxiliary hydraulic pump (AHP2) for pressurizing the transfer liquid LT.

4. The plant as claimed in claim 1, in which the modified Carnot machine is a receiving machine, wherein the hydraulic converter is a hydraulic pump and the heat source is at a temperature below that of the heat sink, and in that the (PED) is an expansion valve (EV).

5. The plant as claimed in claim 1, in which the modified Carnot machine is a receiving machine, wherein the hydraulic converter is a hydraulic pump and the heat source is at a temperature below that of the heat sink, and in that the (PED) comprises a chamber (ABCD) for compressing or expanding, adiabatically, the working fluid GT by means of the transfer liquid LT.

6. The plant as claimed in claim 1, where said plant comprises a modified Carnot machine thermally coupled at its condenser and/or its evaporator to a complementary device, the complementary device being a driving dithermal thermodynamic machine as modified driving Carnot machine and a receiving dithermal thermodynamic machine as modified receiving Carnot machine.

7. The plant as claimed in claim 6, wherein the coupling is achieved by means of a heat-transfer fluid or a heat pipe or by direct contact or by radiation.

8. The plant as claimed in claim 6, wherein the dithermal thermodynamic machine is a second modified Carnot machine.

9. The plant as claimed in claim 1, wherein the modified Carnot machine is mechanically coupled to a complementary device.

10. The plant as claimed in claim 9, wherein said plant comprises a modified receiving Carnot machine coupled to a complementary driving device or to a driving/receiving device, or it comprises a modified driving Carnot machine coupled to a complementary receiving device or to a driving/receiving device.

11. The plant as claimed in claim 10, wherein:
the complementary driving device is selected from the group consisting of an electric motor, a hydraulic turbine, a wind generator, a petroleum-driven engine, a gas-driven engine, a diesel engine, or a modified driving Carnot machine;
the complementary receiving device is selected from the group consisting of a hydraulic pump, a transport vehicle, an alternator, a mechanical vapor or gas compression heat pump, an air compressor or a modified receiving Carnot machine;
the complementary driving/receiving device is a flywheel.

12. The plant as claimed in claim 1, wherein said plant comprises either one of a heat exchanger integrated into the LT circuit or within side walls of transfer chambers (CT) and (CT′), either one of which configured to exchange heat between, on the one hand, the heat source and/or the heat sink, which are at different temperatures, and, on the other hand, the working fluid GT in the transfer chambers (CT and (CT′), which heat exchange may be direct or indirect.

13. The plant as claimed in claim 1, wherein the working fluid GT and the transfer liquid LT are chosen in such a way that GT is weakly soluble in LT, GT does not react with LT and GT in the liquid state is less dense than LT.

14. The plant as claimed in claim 1, wherein the working fluid GT and the transfer liquid LT are isolated from each other by a flexible membrane which creates an impermeable barrier between the fluids and LT but which offers only a very slight resistance to the displacement of LT and a slight resistance to the heat transfer, or by a float which has an intermediate density between that of the working fluid GT in the liquid state and that of the transfer liquid LT.

15. The plant as claimed in claim 13, wherein the transfer liquid LT is chosen from the group consisting of water, mineral oils and synthetic oils.

16. The plant as claimed in claim 13, wherein the working fluid GT is a pure substance or an azeotropic mixture.

17. The plant as claimed in claim 13, wherein the working fluid GT is chosen from the group consisting of water, CO2, NH3, alcohols containing 1 to 6 carbon atoms, alkanes containing 1 to 18 carbon atoms, chlorofluoroalkanes containing 1 to 15 carbon atoms, partially or completely chlorinated alkanes containing 1 to 15 carbon atoms and partially or completely fluorinated alkanes containing 1 to 15 carbon atoms.

18. The plant as claimed in claim 1, wherein said plant is configured to conduct a refrigeration, heat and/or work production process consisting in subjecting a working fluid GT to a succession of modified Carnot cycles, wherein each modified Carnot cycle comprising the following GT transformations:
an isothermal transformation with heat exchange between GT and the heat source, or between GT and the heat sink;
an adiabatic transformation with a reduction in the pressure of the working fluid GT;
an isothermal transformation with heat exchange between GT and the heat sink, or between GT and the heat source; and
an adiabatic transformation with an increase in the pressure of the working fluid GT,

wherein:
the working fluid GT is in a liquid-gas two-phase form at least during the two isothermal transformations of a cycle; and
the two isothermal transformations produce or follow a change in volume of GT concomitant with the displacement of a transfer liquid LT which drives or is driven by a hydraulic converter, and work is delivered or received by the plant by means of a transfer liquid LT which flows through a hydraulic converter during at least the two isothermal transformations.

19. The plant as claimed in claim 18, wherein work is received or delivered by the plant via the transfer liquid LT which flows through a hydraulic converter during just one of the adiabatic transformations.

20. The plant as claimed in claim 18, wherein work is received or delivered by the plant via the transfer liquid LT which flows through a hydraulic converter during both adiabatic transformations.

21. The plant as claimed in claim 18, wherein the cycle comprises the following transformations:
an isothermal transformation initiated by supplying heat to GT from the heat source;
an adiabatic transformation with a reduction in the pressure of the working fluid GT and production of work by the plant;
an isothermal transformation during which heat is delivered by GT to a heat sink at a temperature below that of the source; and
an adiabatic transformation with an increase in the pressure of the working fluid GT.

22. The plant as claimed in claim 21, wherein work is exchanged between the plant and the environment during both adiabatic transformations of the cycle.

23. The plant as claimed in claim 22, wherein the ratio ρa/ρc is such that 0.9≦ρa/ρc≦1, ρa denoting the density of G1 at the end of the step of exchanging heat with the heat sink and ρc denoting the density of GT at the end of the step of exchanging heat with the heat source.

24. The plant as claimed in claim 18, wherein the cycle comprises the following transformations:
an isothermal transformation with the release of heat by GT to the heat sink;
an adiabatic transformation with a reduction in the pressure of the working fluid GT;
an isothermal transformation with heat supplied to GT via the heat source at a temperature below the temperature of the heat sink; and
an adiabatic transformation with an increase in the pressure of the working fluid GT initiated by supplying work via the transfer liquid LT.

25. The plant as claimed in claim 18, wherein said plant includes a modified Carnot machine coupled to a dithermal thermodynamic machine, wherein the heat is transferred from the condenser of the modified Carnot machine to the thermodynamic machine, or the evaporator of the modified Carnot machine receives heat from the thermodynamic machine.

26. The plant as claimed in claim 18, wherein said plant includes first and second modified Carnot machines and optionally at least one intermediate modified Carnot machine between said first and second modified Carnot machines, the modified Carnot machines being thermally coupled, wherein:
the first machine is supplied with heat in order to evaporate a working fluid GTf and the last machine releases the heat generated by condensing a working fluid GTl into the environment, it being possible for said fluids GTf and GTl to be identical or different;
where appropriate, each intermediate machine receives the heat released by the condensation of the working fluid GTi-1 of the machine that precedes it and transfers the heat released by the condensation of its own working fluid GTi to the machine that follows it, it being possible for said fluids GTi-1 and GTi to be identical or different; and
each machine exchanges an amount of work with the environment,

and wherein the machines are all driving machines or all receiving machines and that:
when all the machines are driving machines, the heat delivered to the first machine is at the temperature Thi and the heat released by the last machine is at the temperature Tlo<Thi, and net work is delivered to the environment; and
when all the machines are receiving machines, the heat delivered to the first machine is at the temperature Tlo and the heat released by the last machine is at the temperature Thi which is above both Tlo and the temperature of the environment, and net work is delivered by the environment.

27. The plant as claimed in claim 3, said plant being configured to heat at a temperature Tlo and/or work, wherein, starting from an initial state in which, on the one hand, the working fluid GT is maintained in the evaporator Evap at high temperature and in the condenser (Cond) at low temperature by heat exchange with the hot source at Thi and the cold sink at Tlo (<Thi) respectively and, on the other hand, all the circuits for communication between GT and the transfer liquid L1 are closed off;
at time tα, the GT circuit between (Evap) and (CT′) is opened, the LT circuit between (CT′) and the upstream side of the hydraulic motor (HM) is opened and the auxiliary pump (AHP2) is actuated so that:
the working fluid GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the high pressure Phi enters (CT′) and delivers LT at an intermediate level J;
LT passes through (HM), being expanded therein, and then LT is taken in by (AHP2) and delivered to (ABCD);

at time tβ, the GT circuit between (ABCD) and (Evap) is opened so that the working fluid GT is introduced in the liquid state into the evaporator;
at time tγ, the GT circuit between (Evap) and (CT′) on the one hand and between (ABCD) and (Evap) on the other is closed, the auxiliary pump (AHP2) is stopped, the GT circuit between (Cond) and (ABCD) on the one hand, and between (CT) and (Cond) on the other, is opened and the LT circuit between (CT) and (ABCD) is opened so that:
the GT vapor contained in (CT′) continues to expand, adiabatically, and delivers LT to the low level in (CT′) and then through (HM) to (CT);
the chamber (ABCD) in communication with (Cond) is brought back down to the low pressure and LT that it contains in its lower portion flows into (CT);
the GT vapor contained in (CT) condenses in (Cond):

at time tδ, all the circuits open at time t□ are closed, the GT circuit between (Evap) and (CT) is opened, the LT circuit between (CT) and the upstream side of the hydraulic motor (HM) is opened and the auxiliary pump (AHP2) is actuated so that:
the saturated GT vapor leaving (Evap) at the high pressure Phi enters (CT) and delivers LT to an intermediate level J;
LT passes through (HM) being expanded therein, and then LT is taken in by (AHP2) and delivered to (ABCD);
at time tε, the GT circuit between (ABCD) and (Evap) is opened so that the working fluid GT is introduced in the liquid state into the evaporator;

at time tγ, the GT circuit between (Evap) and (CT) on the one hand, and between (ABCD and (Evap) on the other, is closed, the auxiliary pump (AHP2) is stopped, the GT circuit between (Cond) and (ABCD) on the one hand, and between (CT′) and (Cond) on the other, is opened and the LT circuit between (CT′) and (ABCD) is opened so that:
the GT vapor contained in (CT) continues to expand, adiabatically, and delivers LT to the low level in (CT) and then through (HM) to (CT′);
the chamber (ABCD) in communication with (Cond) is brought back down to the low pressure and the LT that it contains in its lower portion flows into (CT′); and
the GT vapor contained in (CT′) condenses in the (Cond),


wherein, after several cycles, the plant operates in a steady state in which the hot source continuously delivers heat at the temperature Thi to the evaporator (Evap), heat is continuously delivered by the condenser (Cond) to the cold sink at the temperature Tlo, and work is continuously delivered by the machine.

28. The plant as claimed in claim 2, wherein plat is configured to produce heat at a temperature Tlo and/or work, wherein, starting from an initial state in which the working fluid GT is maintained in the evaporator (Evap) at high temperature and in the condenser (Cond) at low temperature by heat exchange with the hot source at Thi and the cold sink at Tlo respectively, and all the communication circuits for the working fluid GT and for the transfer liquid LT are closed off, at time t0 the auxiliary hydraulic pump (AHP1) is actuated and the GT circuit between (Cond) and (Evap) is opened so that a portion of GT, in the saturated or supercooled liquid state, is taken in by (AHP1) into the lower portion of the condenser (Cond) and delivered in the supercooled liquid state into (Evap) where it is heated, and then GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
at time tα when, during the first action cycle, some GT remains liquid in the condenser, the GT circuit between (Evap) and (CT′) on the one hand, and between (CT) and (Cond) on the other, is opened and the circuit allowing LT to be transferred from (CT′) to (CT), passing through the hydraulic motor (HM,) is opened, so that:
GT is heated and evaporates in (Evap), and the saturated GT vapor leaving Evap at the high pressure Phi enters (CT′) and delivers LT to an intermediate level J;
LT passes through (HM,) being expanded therein, and then LT is delivered to (CT) up to the intermediate level I;
the GT vapor contained in (CT) and delivered by LT condenses in (Cond);
GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser (Cond), where it is progressively taken in by (AHP1) and then delivered in the supercooled liquid state to (Evap);

at time tβ the GT circuit between (Evap) and (CT′) is closed so that:
the GT vapor contained in continues to expand, adiabatically, and delivers LT up to the low level in (CT′) and then through (HM) to (CT) where it reaches the high level;
the rest of the GT vapor contained in (CT) and delivered by the liquid LT condenses in (Cond);
GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser (Cond), where it is progressively taken up by (AHP1) and then delivered in the supercooled liquid state into (Evap;

at time tγ, the circuits open at time tβ, except that for transferring GT between (Cond) and (Evap), are closed, the GT circuit between (Evap) and (CT) on the one hand, and between (CT′) and (Cond) on the other, is opened and the circuit for transferring LT from (CT) to (CT′), passing via the hydraulic motor (HM, is opened so that:
GT heats up and evaporates in (Evap) and the saturated GT vapor leaving Evap at the high pressure Phi enters (CT) and delivers LT to an intermediate level J;
LT passes through (HM), being expanded therein, and then LT is delivered into (CT′) up to the intermediate level I;
the GT vapor contained in (CT′) and delivered by the liquid LT condenses in (Cond);
GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser (Cond), where it is progressively taken up by (AHP1) and then delivered in the supercooled liquid state into (Evap);

at time tδ, the GT circuit between (Evap) and (CT) is closed so that:
the GT vapor contained in (CT) continues to expand, adiabatically, and delivers LT up to the low level in (CT) and then through (HM) into (CT′) where it reaches the high level;
the rest of the GT vapor contained in (CT′) and delivered by the liquid LT condenses in (Cond); and
GT in the saturated or supercooled liquid state arrives in the lower portion of the condenser (Cond), where it is progressively taken up by (AHP1) and finally delivered in the supercooled liquid state into (Evap),


wherein, after several cycles, the plant operates in a steady state in which the hot source continuously delivers heat at high temperature Thi to the evaporator (Evap), heat is continuously delivered by the condenser (Cond) to the cold sink at Tlo, and work is continuously delivered by the machine.

29. A method of managing a plant as claimed in claim 5, starting from an initial state in which all the communication circuits for the working fluid GT and the transfer liquid LT are closed off, wherein, at time t0, the hydraulic pump (HP) is actuated and then GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
at time tα, the LT circuits for transferring, on the one hand, LT from the chamber (ABCD) to the upstream side of the hydraulic pump (HP) and, on the other hand, LT from (CT) into (CT′) via the hydraulic pump (HP), are opened so that:
GT in the liquid/vapor equilibrium state in (ABCD) and in (CT) expands from the high pressure Ph to the low pressure Plo and delivers LT through (HP) into (CT′);
the GT vapor contained in (CT′) is adiabatically compressed;

at time tβ, the GT circuit between (Evap) and (CT) on the one hand, and between (ABCD) and (Evap) on the other, is opened so that:
the transfer liquid LT is taken in by the pump (HP), which pressurizes it and delivers it into (CT′);
the LT levels in (ABCD), (CT) and (CT′) pass from high to low, high to an intermediate level J, and low to an intermediate level I, respectively;
because the volume occupied by the GT vapor in (CT) increases, GT evaporates in Evap and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT);
the GT vapor contained in (CT′) continues to be adiabatically compressed up to the high pressure Phi; and
GT in the saturated liquid state at the low pressure Plo flows under gravity from (ABCD) into (Evap);

at time tγ, the GT circuit between (ABCD) and (Evap) is closed, the LT circuit between (ABCD) and the upstream side of the pump (HP) is dosed, the GT circuit between (CT′) and (Cond) on the one hand, and between (Cond) and (ABCD) on the other, is opened and the LT circuit between the downstream side of the pump (HP) and (ABCD) is opened so that:
LT is again taken in by the pump (HP, which pressurizes it and delivers it into (CT′);
the LT levels in (ABCD), (CT) and (CT′) pass from low to high, from the intermediate level J to low, and from the intermediate level I to high respectively;
because the volume occupied by the GT vapor in (CT) continues to increase, GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT);
the GT vapor contained in (CT′), at high pressure Phi, is delivered by LT into and condenses in (Cond); and
GT in the saturated liquid state flows under gravity from (Cond) to (ABCD);

at time tδ, all the circuits open at time tγ are dosed, the LT circuits for transferring LT on the one hand from the chamber (ABCD) to the upstream side of the hydraulic pump (HP, and on the other hand from (CT′) into (CT) passing via the hydraulic pump (HP, are opened so that:
GT in the liquid/vapor equilibrium state in (ABCD) and in (CT′) expands from the high pressure Phi to the low pressure Plo and delivers LT through (HP) into (CT); and
the GT vapor contained in (CT) is adiabatically compressed;

at time tε, the GT circuit between (Evap) and (CT′) on the one hand, and between (ABCD) and (Evap) on the other, is opened so that:
LT is taken in by the pump (HP, which pressurizes it and delivers it into (CT);
the LT levels in (ABCD), (CT) and (CT′) pass from high to low, from low to an intermediate level I, and from high to an intermediate level J respectively;
because the volume occupied by the GT vapor in (CT′) increases, GT evaporates in (Evap and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT′);
the (1 vapor contained in (CT) continues to be adiabatically compressed up to the high pressure Phi; and
GT in the saturated liquid state at the low pressure Plo flows under gravity from (ABCD) into (Evap);

at time tλ, the GT circuit between (ABCD) and (Evap) is closed, the LT circuit between (ABCD) and the upstream side of the pump (HP) is closed, the GT circuit between (CTv and (Cond) on the one hand, and between (Cond) and (ABCD) on the other, is opened and the LT circuit between the downstream side of the pump (HP) and (ABCDv is opened, so that:
is again taken in by the pump (HP), which pressurizes it and delivers it into (CT);
the LT levels in (ABCD), (CT) and (CT′) pass from low to high, from the intermediate level I to high and from the intermediate level J to low respectively;
because the volume occupied by the GT vapor in (CT′) continues to increase, GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT′;
the GT vapor contained in (CT), at high pressure Phi, is delivered by LT into and condenses in (Cond); and
GT in the saturated liquid state flows under gravity from (Cond) into (ABCD),


wherein after several cycles, the plant operates in a steady state and that:
for refrigeration, in the initial state, GT is maintained in the condenser (Cond) at high temperature by heat exchange with the hot sink at Thi and in the evaporator (Evap) at a temperature equal to or below Thi by heat exchange with a medium external to the machine, said medium having initially a temperature Thi, and in a steady state, net work is consumed by the hydraulic pump the condenser (Cond) continuously removes heat to the hot sink at high temperature Thi and heat is continuously consumed by the evaporator (Evap), with extraction of heat from the external medium in contact with said evaporator (Evap), the temperature Tlo of said external medium being strictly below Thi;
for heat production, in the initial state, GT is maintained in the evaporator (Evap) at low temperature by heat exchange with the cold source at Tlo, GT is maintained in the condenser (Cond) at a temperature Thi≧Tlo by heat exchange with a medium external to the machine, said medium having initially a temperature greater than or equal to Thi; and, in the steady state, net work is consumed by the hydraulic pump (HP), the cold source at Tlo continuously supplies heat to the evaporator (Evap), the condenser (Cond) continuously removes heat to the hot sink, the plant producing heat to the external medium in contact with said condenser (Cond), the external medium having a temperature Thi>Tlo.

30. A method for managing a plant as claimed in claim 4, starting from an initial state in which all the communication circuits for the working fluid GT and for the transfer liquid LT are closed off, wherein, at time t0, the hydraulic pump (HP) is actuated and the GT circuit between (Cond) and (Evap) is opened, and GT is subjected to a succession of modified Carnot cycles, each of which comprising the following steps:
at time tα, the LT circuit for transferring LT from the chamber (CT) to the chamber (CT′) passing via the hydraulic pump (HP is opened and the GT circuit between Evap and (CT) is opened, so that:
LT is taken in by the pump HP, which pressurizes it and delivers it into (CT′);
the LT level in (CD passes from high to an intermediate level J, and in (CT′) from low to an intermediate level I;
because the volume occupied by the GT vapor in (CT) increases, GT evaporates in Evap and the saturated GT vapor leaving Evap at the low pressure Plo enters (CT);
the GT vapor contained in (CT′) is adiabatically compressed up to the high pressure Phi; and
GT in the saturated or supercooled liquid state in (Cond) and at the high pressure Phi expands isenthalpically and is introduced in the liquid/vapor two-phase mixture state and at the low pressure Plo into the evaporator (Evap);

at time tβ, the GT circuit between (CT′) and (Cond) is opened so that:
LT is again taken up by the pump HP, which pressurizes it and delivers it into (CT′);
the LT level in (CT) passes from the intermediate level J to low, and in (CT′) from the intermediate level I to high;
because the volume occupied by the GT vapor in (CT) continues to increase, GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT); and
the GT vapor contained in (CT′), at high pressure Phi, is delivered by LT into and condenses in (Cond);

at time tγ, all the circuits open at time tβ, except for the GT circuit between (Cond) and (Evap), are closed, the LT circuit for transferring LT from (CT′) to (CT) passing via the hydraulic pump (HP) is opened and the GT circuit between (Evap and (CT′) is opened so that:
LT is taken in by the pump (HP), which pressurizes it and delivers it into (CT);
the LT level in (CT) passes from low to an intermediate level I, and in (CT′) from high to an intermediate level J;
since the volume occupied by the GT vapor in (CT′) increases, the working fluid GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT′);
the GT vapor contained in (CT) is adiabatically compressed up to the high pressure Phi; and
GT in the saturated or supercooled liquid state in (Condv and at the high pressure Phi expands isenthalpically and is introduced in the liquid/vapor two-phase mixture state and at the low pressure Plo into the evaporator (Evap); and

at time tδ the GT circuit between (CTv and (Cond) is opened so that:
LT is again taken in by the pump (HP), which pressurizes it and delivers it into (CT);
the LT level in (CT) passes from the intermediate level I to high and in (CT′) from the intermediate level J to low;
because the volume occupied by the GT vapor in (CT′) continues to increase, GT evaporates in (Evap) and the saturated GT vapor leaving (Evap) at the low pressure Plo enters (CT′); and
the GT vapor contained in (CT), at high pressure Phi, is delivered by LT into and condenses in (Cond),


wherein, after several cycles, the plant operates in a steady state, and that:
for refrigeration: in the initial state, GT is maintained in the condenser (Cond) at high temperature by heat exchange with the hot sink at Thi and in the evaporator (Evap) at a temperature equal to or below Thi by heat exchange with a medium external to the machine, said medium having initially a temperature greater than or equal to Thi; and, in the steady state, net work is consumed by the hydraulic pump (HP), the condenser (Cond) continuously removes heat to the hot sink at high temperature Thi and heat is continuously consumed by the evaporator (Evap), that is to say there is extraction of heat from the external medium in contact with said evaporator (Evap), the temperature Tlo of said external medium being <Thi; and
for heat production: in the initial state, GT is maintained in the evaporator (Evap) at low temperature by heat exchange with the cold source at Tlo and in the condenser (Cond) at a temperature ≧Thi by heat exchange with a medium external to the plant at a temperature ≧Thi; and, in the steady state, net work is consumed by the hydraulic pump HP, the cold source at Tlo supplies heat continuously to (Evap), and (Cond) continuously removes heat to the hot sink, that is to say there is production of heat in the external medium in contact with (Cond), the temperature Thi of said external medium being above Tlo.