EP1809955B1 - Production of very low-temperature refrigeration in a thermochemical device. - Google Patents

Description

The present invention relates to a thermochemical device for the production of cold at very low temperature, as described by US5174367 and US5857346 . A system constituted by a thermochemical dipole implementing two reversible thermochemical phenomena is a known means for producing cold. The thermochemical dipole comprises a BT reactor, an HT reactor and means for exchanging a gas between BT and HT. The two reactors are the seat of selected reversible thermochemical phenomena such that, at a given pressure in the dipole, the equilibrium temperature in BT is lower than the equilibrium temperature in HT.

• une adsorption renversable de G par un solide microporeux S ;
• une réaction chimique renversable entre un solide réactif S et G ;
• une absorption de G par une solution saline ou binaire S selon le schéma $$\mathrm{ʺsorbant\; Sʺ}+\mathrm{ʺGʺ\; \leftrightarrows \; ʺsorbant\; S}+\mathrm{Gʺ}\mathrm{.}$$
  

The reversible phenomenon in the HT reactor involves an S sorbent and a G gas and can be:

• reversible adsorption of G by a microporous solid S;
• a reversible chemical reaction between a solid reagent S and G;
• absorption of G by saline or binary S according to the scheme $$\mathrm{"Sorbent\; S"}+\mathrm{"G"\; S\; "sorbent}+\mathrm{BOY\; WUT}\mathrm{.}$$
  

L'étape de régénération correspond à l'étape de décomposition dans HT $$\mathrm{ʺsorbant\; S}+\mathrm{Gʺ}\to \mathrm{ʺsorbant\; Sʺ}+\mathrm{ʺGʺ}\mathrm{.}$$

The reversible phenomenon in the LV reactor involves the same gas G. It can be a change in the liquid / gas phase of the gas G or a reversible adsorption of G by a microporous solid S ¹ , or a reversible chemical reaction between a reactive solid S ¹ and G, or an absorption of G by a solution S1, the sorbent S1 being different from S. The cold production step of the device corresponds to the synthesis step in HT $$\mathrm{"Sorbent\; S"}+\mathrm{BOY\; WUT}\to \mathrm{S\; sorbent}+\mathrm{BOY\; WUT}\mathrm{.}$$

The regeneration step corresponds to the decomposition step in HT $$\mathrm{S\; sorbent}+\mathrm{BOY\; WUT}\to \mathrm{"Sorbent\; S"}+\mathrm{BOY\; WUT}\mathrm{.}$$

• au cours de l'étape de production de froid par le dipôle, la consommation exothermique de gaz dans HT a lieu à une température proche de et supérieure à To, qui créé dans le dipôle une pression telle que la température d'équilibre dans le réacteur BT est proche de et inférieure à T_F.
• au cours de l'étape de régénération du dipôle, la libération endothermique de gaz dans HT est effectuée à la température Tc qui crée dans le dipôle une pression telle que la température à laquelle s'effectue la consommation exothermique de gaz dans BT est proche de et supérieure à To.

The production of cold at a temperature T _F in a dipole (BT, HT) from a heat source at the temperature T _c and a thermal sink at the temperature To, implies that the thermochemical phenomenon in BT and the Thermochemical phenomenon in HT are such that:

• during the step of producing cold by the dipole, the exothermic consumption of gas in HT takes place at a temperature close to and greater than To, which creates in the dipole a pressure such that the equilibrium temperature in the reactor BT is close to and lower than T _F.
• during the regeneration step of the dipole, the endothermic release of gas in HT is carried out at the temperature Tc which creates in the dipole a pressure such that the temperature at which the exothermic consumption of gas in BT occurs is close to and greater than To.

The thermochemical phenomena currently used make it possible to produce cold at a negative temperature in BT, but they do not meet the above criteria with the aim of producing cold at very low temperatures (T _F typically from -20 ° C to - 40 ° C) for applications for freezing and long-term storage of foodstuffs from a heat source whose thermal potential is of the order of 60 to 80 ° C, the heat sink generally consisting of the ambient environment being at a temperature TB of the order of 10 ° C to 25 ° C. Either these phenomena require during regeneration a Tc temperature well above 70 ° C to operate with a heat sink at room temperature To, or they require a heat sink at a temperature lower than To if a heat source is used at Tc = 60-80 ° C.

For example, to produce cold at -30 ° C using a hot source at 70 ° C, if BT is the seat of a phase change L / G ammonia NH ₃ , and HT is the seat "d" a chemical sorption of NH ₃ by a reactive solid S: if S is BaCl ₂ , it would be necessary to have a heat sink at 0 ° C for the BT reactor during the cold production step, whereas if S is CaCl ₂ , would need a heat sink at -5 ° C, that is to say at a temperature much lower than To, during the regeneration step.

Solar energy or geothermal energy is an interesting source of heat, but it provides low temperature heat, which is generally not higher than 60-70 ° C if capture technology is used. inexpensive, such as planar sensors conventionally used for the production of domestic hot water. The use of these types of energy therefore does not achieve the goal.

• le dipôle D2 fonctionne avec des phénomènes thermochimiques capables de produire du froid à une température Tf inférieure à -20°C avec un puits thermique à To, mais qui nécessiterait pour sa régénération une source chaleur à une température supérieure à la température Th avec un puits thermique à To ;
• le dipôle D1 fonctionne avec des phénomènes thermochimiques régénérables à partir d'une source de chaleur disponible à la température Th et d'un puits thermique à la température To.

The inventors have now found that it is possible to produce cold at a temperature Tf lower than -20 ° C from a heat source at a temperature Th between 60 and 80 ° C and a heat sink at the room temperature To ranging from 10 ° C to 25 ° C, by associating two dipoles D1 and D2 so that:

• the dipole D2 operates with thermochemical phenomena capable of producing cold at a temperature Tf lower than -20 ° C with a thermal well at To, but which would require for its regeneration a heat source at a temperature above the temperature Th with a well thermal to To;
• the dipole D1 operates with regenerable thermochemical phenomena from a heat source available at the temperature Th and a heat sink at the temperature To.

The object of the present invention is therefore to provide a method and a device for the production of cold at a temperature Tf lower than -20 ° C, from a heat source at a temperature Th of the order of 60 -80 ° C and a heat sink at room temperature To of the order of 10 ° C to 25 ° C.

• les phénomènes thermochimiques dans le dipôle D2 sont tels que ce dipôle peut produire du froid à Tf avec un puits thermique à la température ambiante To ;
• les phénomènes thermochimiques dans le dipôle D1 sont tels que ce dipôle peut être régénéré à partir de la source de chaleur Th et un puits thermique à la température To ;
• D1 comprend un évaporateur/condenseur EC1 et un réacteur R1 reliés par un conduit permettant le passage contrôlé de gaz, et D2 comprend un évaporateur/condenseur EC2 et un réacteur R2 relié par un conduit permettant le passage contrôlé de gaz ;
• EC1 contient un gaz G1 et R1 contient un sorbant S1 capable de former un processus physico-chimique renversable avec G1, et EC2 contient un gaz G2 et R2 contient un sorbant S2 capable de former un processus physico-chimique renversable avec G2;
• Les dipôles D1 et D2 sont munis de moyens permettant de les coupler entre eux par voie thermique lorsque G1 et G2 sont différents et par voie massique lorsque G1 et G2 sont identiques ;
• les gaz et les sorbants mis en oeuvre sont choisis de manière que, lorsque les dipôles sont couplés, les températures d'équilibre des phénomènes thermochimiques dans les réacteurs et les évaporateurs/condenseurs sont telles que T (EC1) ≤ T(EC2) < T(R1) < T(R2) ; les phénomènes thermochimiques sont choisis parmi le changement de phase L/G de l'ammoniac (NH₃), de la méthylamine (NH₂CH₃) ou de H₂O dans les évaporateurs/ condenseurs, et pour les réacteurs, on choisi entre
  • une sorption chimique renversable de NH₃ par SrCl₂ ou par BaCl₂, ou de NH₂CH₃ par CaCl₂ ;
  • une adsorption d'eau par la zéolithe ou un silicagel ;
  • l'adsorption de méthanol (MeOH) ou de l'ammoniac dans du charbon actif ;
  • l'absorption de NH₃ dans une solution liquide d'ammoniaque (NH₃,H₂O). Dans la suite du texte, l'expression "les éléments" d'un dipôle sera utilisée pour désigner simultanément le réacteur et l'évaporateur/condenseur du dipôle. Le procédé de production de froid à la température Tf à partir d'une source de chaleur à la température Th et d'un puits thermique à la température ambiante To consiste à faire fonctionner le dispositif selon l'invention à partir d'un état initial dans lequel le dipôle D2 est à l'état régénéré, et le dipôle D1 est à régénérer, les deux éléments d'un dipôle donné étant isolés l'un de l'autre, ledit procédé comprenant une série de cycles successifs constitués par une étape de production de froid et une étape de régénération :
  • au début de la première étape, qui est l'étape de production de froid à Tf, on met les deux éléments de chacun des dipôles en communication, ce qui provoque la phase d'évaporation endothermique spontanée dans EC2 (productrice de froid à Tf) qui produit G2 sous forme de gaz, et le transfert du gaz libéré vers R2 pour son adsorption exothermique par S2 dans R2, et parallèlement on apporte de la chaleur à la température Th au réacteur R1, ce qui provoque la désorption du gaz G1 par S1 dans R1 et la phase de condensation de G1 dans EC1 ;
  • au cours d'une deuxième étape, qui est l'étape de régénération du dispositif, on apporte de la chaleur à la température Th au réacteur R2 pour réaliser la désorption de G2 par le sorbant S2 dans R2, et on transfère de D2 vers D1 soit de la chaleur lorsque G1 et G2 sont différents, soit du gaz si G1 et G2 sont identiques, pour réaliser une sorption de gaz par S1 dans R1.

The cold generating device according to the present invention comprises a cold generating dipole D2 and an auxiliary dipole D1, and is characterized in that:

• the thermochemical phenomena in the dipole D2 are such that this dipole can produce cold at Tf with a heat sink at room temperature To;
• the thermochemical phenomena in the dipole D1 are such that this dipole can be regenerated from the heat source Th and a heat sink at the temperature To;
• D1 comprises an evaporator / condenser EC1 and a reactor R1 connected by a conduit allowing the controlled passage of gas, and D2 comprises an evaporator / condenser EC2 and a reactor R2 connected by a conduit for the controlled passage of gas;
• EC1 contains a gas G1 and R1 contains a sorbent S1 capable of forming a reversible physico-chemical process with G1, and EC2 contains a gas G2 and R2 contains a sorbent S2 capable of forming a reversible physico-chemical process with G2;
• D1 and D2 dipoles are provided with means for coupling them thermally between them when G1 and G2 are different and mass when G1 and G2 are identical;
• the gases and sorbents used are chosen so that, when the dipoles are coupled, the equilibrium temperatures of the thermochemical phenomena in the reactors and the evaporators / condensers are such that T (EC1) ≤ T (EC2) <T (R1) <T (R2); the thermochemical phenomena are chosen from the L / G phase change of ammonia (NH ₃ ), of methylamine (NH ₂ CH ₃ ) or of H ₂ O in the evaporators / condensers, and for the reactors, one chooses between
  • reversible chemical sorption of NH ₃ by SrCl ₂ or BaCl ₂ , or of NH ₂ CH ₃ by CaCl ₂ ;
  • water adsorption by zeolite or silica gel;
  • the adsorption of methanol (MeOH) or ammonia in activated carbon;
  • the absorption of NH ₃ in a liquid solution of ammonia (NH ₃ , H ₂ O). In the rest of the text, the expression "the elements" of a dipole will be used to designate simultaneously the reactor and the evaporator / condenser of the dipole. The method for producing cold at temperature Tf from a heat source at temperature Th and a heat sink at ambient temperature To consists of operating the device according to the invention from an initial state. in which the dipole D2 is in the regenerated state, and the dipole D1 is to be regenerated, the two elements of a given dipole being isolated from one another, said method comprising a series of successive cycles constituted by a step of cold production and a regeneration step:
  • at the beginning of the first step, which is the cold production step at Tf, the two elements of each of the dipoles are brought into communication, which causes the spontaneous endothermic evaporation phase in EC2 (cold producer at Tf) which produces G2 in the form of gas, and the transfer of the liberated gas to R2 for its exothermic adsorption by S2 in R2, and at the same time heat is supplied at the temperature Th to the reactor R1, which causes the desorption of the gas G1 by S1 in R1 and the condensation phase of G1 in EC1;
  • during a second step, which is the regeneration step of the device, heat is supplied at the temperature Th to the reactor R2 to achieve the desorption of G2 by the sorbent S2 in R2, and is transferred from D2 to D1 either heat when G1 and G2 are different, or gas if G1 and G2 are identical, to perform gas sorption by S1 in R1.

In this process, the dipoles therefore operate in phase opposition: one of the dipoles is in a gas absorption phase in the sorbent, while the other is in the gas desorption phase by the sorbent.

The different steps can be performed continuously or on demand. At the beginning of a step, the elements of the same dipole must be put in communication, so that thermochemical phenomena can occur. For to operate the device continuously, it is sufficient to bring to the end of a step, the amount of heat appropriate to the appropriate reactor to start the next step. If the device is intended to operate discontinuously, it suffices to isolate the elements of each dipole by the isolation means at the end of a cold production step or a regeneration step.

The process can be carried out permanently if the heat at the temperature Th is permanently available, for example if it is geothermal energy. The operation will be discontinuous if the heat source is not permanent, for example if it is solar energy whose availability varies during a day.

In a first embodiment, the coupling of the dipoles is effected thermally between the evaporator / condenser EC1 of the dipole D1 and the evaporator / condenser EC2 of the dipole D2, and the thermochemical phenomena are chosen such that, in this phase of coupling, T (EC1) <T (EC2) <T (R1) <T (R2). In this case, G1 and G2 are different.

The thermal connection between EC1 and EC2 can be achieved for example by a heat transfer fluid loop, by a heat pipe or by a direct contact.

The method of this first embodiment is characterized in that, in the second step, the evaporators / condensers EC1 and EC2 are thermally bonded, and heat is simultaneously supplied at the temperature Th to the reactor R2 to cause the endothermic desorption of G2 in R2 and the exothermic condensation of G2 in EC2, the heat released in EC2 being transferred to the EC1 reactor, which causes endothermic evaporation of G1 in EC1 and concomitant exothermic absorption of G1 by S1 in R1.

In this embodiment, the device produces cold at the temperature Tf during the cold generation step of the dipole D2 concomitant with the regeneration step of the auxiliary dipole D1.

During the step of regeneration of the dipole D2, cold can be produced at the temperature Ti lower than To in EC1 by the dipole D1, if the heat required during this step for the evaporation phase in EC1 is greater than the heat provided by the condensation phase in EC2.

The cold production method according to the first embodiment is illustrated on the Figures 1a and 1b , which represent the Clapeyron diagram respectively for the cold production stage ( Fig. 1a ), and for the regeneration stage ( Fig. 1b ). The lines 0, 1, 2 and 3 represent the equilibrium curve respectively for the phase change L / G of the gas G1, the reversible phenomenon G1 + S1 ⇆ (G1, S1), the reversible phenomenon G2 + S2 ⇆ (G2 , S2) and the L / G phase change of the G2 gas.

During the cold production step, the evaporation of G2 in EC2 (point E2 of line 3) by taking heat from the ambient environment to be cooled to Tf, and therefore produces cold at this temperature. G2 gas thus produced is transferred into R2 to be absorbed by S2 by releasing heat at a temperature above the ambient To (point R _2S of line 2). In parallel, a contribution to R1 of heat at the temperature Th (point R _1D of the curve 1) causes the release of G1 which is transferred in EC1 for the condensation of G1 (point C ₁ of the curve 0), releasing heat in the environment at To.

During the step of regeneration of the dipole D2, which corresponds to the regeneration step of the device, heat at the temperature Th is brought to R2 (point R _D2 of the line 2) which releases G2 gas which will condense in EC2 (point C ₂ of line 3) by releasing heat at temperature Ti, said heat being transferred to EC1 to trigger the release of gas G1 (point E ₁ of curve 0), said gas G1 passing in R1 for the synthesis step (point R _1S of curve 1). If the heat supplied by EC2 to EC1 is insufficient to release all of the gas in EC1, heat is taken from the environment, which will produce cold at the Ti temperature below room temperature.

In a preferred form of the first embodiment, each of the EC elements is an assembly comprising an evaporator E and a condenser C connected by a conduit allowing the passage of gas or liquid. In addition, in order to limit thermal losses and to improve the efficiency of D1 dipole regeneration, the elements involved in thermal coupling, ie E1 and C2, are thermally isolated from the ambient environment.

In a second embodiment, the two dipoles operate with the same gas G. In this embodiment, the dipoles D1 and D2 of the device according to the invention are coupled, during the regeneration phase of the dipole D1, by a link mass which allows the passage of gas between the reactor R1 of the dipole D1 and the reactor R2 of the dipole D2 on the one hand, between the evaporators / condensers EC1 and EC2 on the other hand. In addition, the thermochemical phenomena are chosen such that T (EC1) = T (EC2) <T (R1) <T (R2).

The cold production method according to this second embodiment is characterized in that, at the beginning of the second step, the communication between EC2 and R2 is stopped, R1 and R2 are put in communication, and the heat at the temperature Th to the reactor R2, which causes the endothermic desorption of G by S2 in R2, cooling the reactor R1, which causes absorption of the gas G in R1. Cooling can be performed using cooling fluid circuits. The cooling can also be controlled by external conditions, for example by natural cooling at night, in the absence of sun.

During the process, EC1 and EC2 are placed in communication to convert G in liquid form from EC1 to EC2. This operation can be performed during an additional step. It may also be performed during the 1 ^st or the ^2nd stage, if the device comprises an expansion valve on the conduit connecting EC1 and EC2.

The cold production method of this second embodiment is illustrated on the Figures 2a and 2b , which represent the Clapeyron diagram respectively for the cold production stage ( Fig. 2a ), and for the regeneration stage ( Fig. 2b ). The lines 0, 1 and 2 represent the equilibrium curve respectively for the L / G phase change of the gas G, the reversible phenomenon G + S1 ⇆ (G, S1), and the reversible phenomenon G + S2 ⇆ (G, S2).

During the cold production step, the evaporation of G in EC2 (point E of line 0) takes heat at Tf in the environment and produces cold at this temperature. G gas thus released is transferred to R2 for the synthesis step with S2 by releasing heat at a temperature above the ambient To (point R _2s of line 2). In parallel, a contribution to R1 of heat at the temperature Th (point R _1D of the curve 1) causes the release of G which is transferred into EC1 for the condensation of G (point C of the curve 0), releasing heat in the environment in To.

During the regeneration step, heat at the temperature Th is brought to R2 ( _2D R point of the line 2) which releases G gas which is transferred in R1 for synthesis with S1 (R _1S point of the curve 0).

The present invention is illustrated by the following examples to which it is however not limited.

Example 1

This example illustrates a device for the production of cold, in which the dipoles cooperate by a thermal connection. Each of the elements EC is constituted by a condenser and an evaporator connected by a conduit allowing the passage of gas or liquid, and designated C1, C2, E1 and E2. A schematic representation of the device is given on the figure 3 .

In accordance with the figure 3 , the dipole D1 comprises a reactor R1, a condenser C1 and an evaporator E1. R1 and C1 are connected by a conduit provided with a valve 1.1, C1 and E1 are connected by a single conduit. R1 is provided with heating means 2.1 and means 3.1 for evacuating heat. C1 is provided with means 4.1 to evacuate condensation heat. The dipole D2 comprises a reactor R2, a condenser C2 and an evaporator E2. R2 and C2 are connected by a conduit provided with a valve 1.2, R2 and E2 are connected by a duct equipped with a valve 8.2, C2 and E2 are connected by a duct provided with an expansion valve 9.2. R2 is provided with heating means 2.2 and means 3.2 for removing heat. E2 is equipped with means 5.2 for taking heat from the medium to be cooled. E1 and C2 are provided with means 6 allowing the exchange of heat between them and a device 7 which thermally isolates them from the environment.

R1 is the seat of a reversible chemical sorption of methylamine (gas G1) on CaCl ₂ , 2 NH ₂ CH ₃ (the reactive solid S1), C1 and E1 being the seat of a phenomenon of condensation / evaporation of methylamine (the G1 gas). R2 is the seat of a reversible chemical sorption of NH ₃ (gas G2) on CaCl ₂ , 4 NH ₃ (the solid S 2), C2 and E2 being the seat of a phenomenon of condensation / evaporation of the NH ₃ gas.

• pour le dipôle 1 :
  
          NH₂CH₃ (gaz) ⇆ NH₂CH₃ (liquide)
  
          (CaCl₂, 2.NH₂CH₃) + 4.NH₂CH₃ ⇆ (CaCl₂, 6.NH₂CH₃)
  
  
• pour le dipôle 2 :
  
          NH_{3 (gaz)} ⇆ NH₃ (liquide)
  
          (CaCl₂, 4.NH₃) + 4.NH₃ ⇆ (CaCl₂, 8.NH₃)
  
  

Thermochemical phenomena are as follows:

• for the dipole 1:
  
  NH ₂ CH ₃ (gas) ⇆ NH ₂ CH ₃ (liquid)
  
  (CaCl ₂ , 2.NH ₂ CH ₃ ) + 4.NH ₂ CH ₃ ⇆ (CaCl ₂ , 6.NH ₂ CH ₃ )
  
  
• for the dipole 2:
  
  NH _{3 (gas)} ⇆ NH ₃ (liquid)
  
  (CaCl ₂ , 4.NH ₃ ) + 4.NH ₃ ⇆ (CaCl ₂ , 8.NH ₃ )
  
  

The operation of the device comprising these reagents is represented on the figure 9 which gives the equilibrium curves of the thermochemical phenomena concerned.

The parts of the device that are active during the cold production step are represented on the figure 4 . The valves 1.1 and 1.2 are opened and the heat transfer means 6 are inactivated. The opening of the valves 8.2 and 9.2 causes the spontaneous production of the gas G2 in E2, the transfer of G2 to R2 through the valve 8.2, which on the one hand causes the production of cold around E2 by the sampling means. 5.2 heat, and the synthesis in R2 with removal of heat formed to the atmosphere around R2 using means 3.2. Meanwhile, the heating means 2.1 provide R1 with heat which is at the temperature Th, which causes the production of G2 in G2, G2 passing in C1 connected thermally to the environment by means 4.1. G2 condenses in C2 and goes into E1.

The parts of the device that are active during the regeneration step of the device are represented on the figure 5 . The valves 1.1 and 1.2 remain open, R2 is supplied by the means 2.2 of the heat at the temperature Th, which releases the gas G2 which passes into the condenser C2 in which it condenses before passing simultaneously or later in the evaporator E2, depending on the state of the valve 9.2. The heat generated by the condensation in C2 is transferred to E1 by the means 6. This heat input in E1 causes an evaporation of G1 which is transferred via C1 and the valve 1.1 into R1 where it is absorbed by S1, the heat released by this absorption being transferred to the environment at the temperature To by the means 3.1. At the end of this step, the device is again ready to produce cold. If the production must be immediate, we repeat the first step. If the production has to be deferred, the device is maintained in the regenerated state by closing the valves 1.1, 1.2 and 8.2.

Such a device makes it possible to produce cold at an intermediate temperature Ti between To and Tf during the regeneration step of the device. For example, referring to the figure 9 If the heat supplied by EC2 by the condensation of NH ₃ to EC1 for evaporation of CH ₃ NH ₂ is insufficient to release the entire NH ₂ CH _3, heat is taken from the environment, which will produce cold at the temperature Ti close to 0 ° C.

Example 2

This example illustrates a device for the production of cold, in which the dipoles cooperate by a mass bond. EC1 and EC2 are respectively a condenser C1 and an evaporator E2. A schematic representation of the device is given on the figure 6 .

In accordance with the figure 6 , the dipole D1 comprises the reactor R1 and the condenser C1 connected by a conduit provided with a valve 11. R1 comprises means 21 for bringing the heat and means 31 for removing heat. C1 comprises means 41 for removing heat. The dipole D2 comprises the reactor R2 and the evaporator E2 connected by a conduit provided with a valve 12. R2 comprises means 22 for supplying heat and means 32 for removing heat. E2 comprises means 52 for supplying heat.

R1 and R2 are connected by a conduit which is placed before the valves 11 and 12, and which is provided with a valve 8. C1 is connected by a conduit to a reservoir which is itself connected to E2 by a conduit provided with an expansion valve 9 which can for example be controlled and activated by a drop in liquid level or pressure prevailing in E2.

The active parts of the device during the cold production step are represented on the figure 7 . The valve 8 is closed, the expansion valve 9 is activated according to the liquid filling or the pressure in E2, and the valves 11 and 12 are opened. The opening of the valve 12 causes the exothermic evaporation of gas in E2 with production of cold, and the exothermic synthesis in R2, the heat being removed by 32. At the same time, R1 is supplied via 21 heat at the temperature Tf, which causes the release of gas in R1, the transfer of this gas to C in which it condenses, the heat of condensation being transferred to the environment by 41. The condensed liquid in C is transferred into the tank 10.

The active parts of the device during step e regeneration are represented on the figure 8 . At the beginning of this step, the valves 11 and 12 are closed, the valve 8 is opened and the expansion valve 9 is closed, given that the pressure or the liquid level in E2 have not decreased. A supply of heat at the temperature Tf to R2 via 22 causes a gas evolution in R2, the transfer of this gas to R1 via the valve 8, and the exothermic synthesis in R1, the heat released being eliminated via 31.

Such a device can be implemented using ammonia as gas G, CaCl ₂ , NH ₃ as solid S 2 in R 2 and BaCl ₂ as solid S 1 in R 1.

Thermochemical phenomena are as follows:

NH _{3 (gas)} ⇆ NH ₃ (liquid)

(CaCl ₂ , 4 NH ₃ ) + 4 NH ₃ ⇆ (CaCl ₂ , 8 NH ₃ )

(BaCl ₂ ) + 8 NH ₃ ⇆ (BaCl ₂ , 8 NH ₃ )

The operation of the device comprising these reagents is represented on the figure 10 which gives the equilibrium curves of the thermochemical phenomena concerned. Analogous curves would be obtained by a similar device, in which CaCl ₂ , 4NH ₃ would be replaced by SrCl ₂ , N _H 3.

The cold production step is represented by the positions 1 and 2 of the dipoles D1 and D2. D1 is in the regeneration phase thanks to the introduction of heat available at the temperature Th of the order of 70 ° C, to cause the decomposition of (BaCl ₂ , 8NH ₃ ) in R1 with release of NH ₃ which will condense in C1 by releasing the heat in the heat sink constituted by the ambient at To = 25 ° C. Concomitantly, D2 is in the cold production phase, by taking heat from the medium to be cooled to a temperature Tf of the order of -30 ° C.

The step of regeneration of D2 is materialized by the position 3. The supply of available heat at the temperature Th of the order of 70 ° C causes the decomposition of (CaCl ₂ , 8.NH ₃ ) by releasing NH ₃ , which is transferred to R1 to cause synthesis of BaCl ₂ , 8NH ₃ . At this stage, the reactors R1 and R2 are in the state required for a regenerated device, and the opening of the valve 9 makes it possible to put C1 and E2 in the state required for complete regeneration of the device.

Claims (7)

1. A device for producing refrigeration to a temperature Tf of less than -20°C, from a heat source at a temperature Th of the order of the 60-80°C and a heat sink at room temperature To of the order of 10°C to 25°C, comprising a refrigerating dipole D2 and an auxiliary dipole D1, characterized in that:

   • the thermochemical phenomena in the dipole D2 are such that this dipole may produce refrigeration at Tf with a heat sink at room temperature To;

   • the thermochemical phenomena in the dipole D1 are such that this dipole may be regenerated from the heat source Th and a heat sink at temperature To;

   • D1 comprises an evaporator/condenser EC1 and a reactor R1 connected through a conduit allowing controlled passage of gas, and D2 comprises an evaporator/condenser EC2 and a reactor R2 connected through a conduit allowing controlled passage of gas;

   • EC1 contains a gas G1 and R1 contains a sorbent S1 capable of forming a reversible physico-chemical process with G1, and EC2 contains a gas G2 and R2 contains a sorbent S2 capable of forming a reversible physico-chemical process with G2;

   • the applied gases and sorbents are selected so that, at a given pressure, the equilibrium temperatures of the thermochemcal phenomena in the reactors and the evaporators/condensers are such that T(EC1) ≤ T(EC2) < T(R1) < T(R2);

   • the dipoles D1 and D2 are provided with means allowing their coupling with each other via a thermal route when G1 and G2 are different and via a massive route when G1 and G2 are identical;

   • the thermochemical phenomena in the evaporators/condensers are selected from the phase transition L/G of ammonia (NH₃), the phase transition of methylamine (NH₂CH₃) and the phase transition of H₂O;

   • the thermochemical phenomena in the reactors are selected from reversible chemical sorptions of NH₃ by CaCl₂, by SrCl₂, or by BaCl₂, or of NH₂CH₃ by CaCl₂, the adsorption of water by zeolite or a silica gel, the adsorption of methanol or ammonia in active coal, and the adsorption of NH₃ in a liquid solution of ammonia (NH₃, H₂O).
2. The device according to claim 1, characterized in that each of the evaporators/condensers is formed with an assembly comprising an evaporator E and a condenser C connected through a conduit letting through the gas or liquid.
3. The method for refrigerating to a temperature Tf of less than -20°C, from a heat source at a temperature Th of the order of 60-80°C and from a heat sink at room temperature To of the order of 10 to 25°C, characterized in that it consists of operating the device according to claim 1 from an initial state wherein the dipole D2 is in the regenerated state, and the dipole 1 is to be regenerated, both elements of a given dipole being isolated from each other, said method comprising a series of successive cycles formed by a refrigeration step and by a regeneration step:

   - at the beginning of the first step, which is the step for refrigerating to Tf, both elements of each of the dipoles are put into communication, which causes the spontaneous endothermic evaporation step in EC2 (refrigerating to Tf) which produces G2 as a gas, and the transfer of the released gas to R2 for its exothermic adsorption by S2 in R2, and in parallel heat at temperature Th is provided to the reactor R1, which causes desorption of the gas G1 by S1 in R1 and the condensation phase of G1 in EC1;

   - during a second step, which is the regeneration step of the device, heat at temperature Th is provided to the reactor R2 for achieving desorption of G2 by the sorbent S2 in R2, and either heat is transferred from D2 to D1 when G1 and G2 are different or gas when G1 and G2 are identical for achieving sorption of gas by S1 in R1.
4. The method according to claim 3, characterized in that the coupling of the dipoles is carried out via a thermal route between the evaporator/condenser EC1 of the dipole D1 and the evaporator/condenser EC2 of the dipole D2, G1 and G2 are different, and the thermochemical phenomena are selected so that, in this coupling phase, T (EC1) < T (EC2) < T (R1) < T(R2).
5. The method according to claim 4, characterized in that, during the second step, the evaporators/condensers EC1 and EC2 are put in thermal connection, and heat at temperature Th is simultaneously applied to the reactor R2 in order to cause endothermic desorption of G2 in R2 and exothermic condensation of G2 in R2, the heat released in EC2 being transferred to the reactor EC1, which causes endothermic evaporation of G1 in EC1 and concomitant exothermic absorption of G1 by S1 in R1.
6. The method according to claim 3, characterized in that the dipoles D1 and D2 operate with the same gas G and are coupled, during the regeneration phase of the dipole D1, through a mass connection which allows passage of the gas between the reactor R1 of the dipole D1 and the reactor R2 of the dipole D2 on the one hand and between the evaporators/condensers EC1 and EC2 on the other hand, the thermochemical phenomena being selected so that T(EC1) = T (EC2) < T (R1) < T(R2).
7. The method according to claim 6, characterized in that, at the beginning of the second step, communication between EC2 and R2 is stopped and R1 is put into communication with R2 and heat a temperature Th is simultaneously provided to the reactor R2, which causes endothermic desorption of G in R2, and by cooling the reactor R1, which causes absorption of the gas G in R1.

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