WO2023156047A1

WO2023156047A1 - Refrigeration device and method

Info

Publication number: WO2023156047A1
Application number: PCT/EP2022/086870
Authority: WO
Inventors: Sylvain LANDE
Original assignee: L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date: 2022-02-15
Filing date: 2022-12-20
Publication date: 2023-08-24
Also published as: FR3132754A1; FR3132754B1

Abstract

Refrigeration device comprising a working circuit (10) of working fluid forming a cycle comprising a mechanism (2, 3) for compression, cooling, expansion and heating, an electric motor (11) driving in rotation a shaft (15) which carries a compressor wheel (2), an electronic controller (12) configured to receive a signal (13) demanding a defined cooling power (P) and, in response, to control the speed of rotation (V) of the motor (11), the electronic controller (12) being configured to limit the maximum operating speed (Vmf) of the motor (11) to a value less than or equal to its maximum design speed (Vmc), in nominal operation, the electronic controller (12) fixing the maximum operating speed (Vmf) of the motor at the speed of rotation that supplies the cold power (P), and regulating the speed of rotation (V) of the motor in accordance with the demand for cold power, without exceeding the maximum operating speed (Vmf).

Description

Refrigeration device and method

The invention relates to a device and a method for refrigerating

The invention relates more particularly to a device for refrigeration at low temperature, in particular cryogenic, that is to say at a temperature between minus 100 degrees centigrade and minus 273 degrees centigrade, comprising a working circuit forming a loop and containing a working fluid, the working circuit forming a cycle comprising in series: a working fluid compression mechanism, a working fluid cooling mechanism, a working fluid expanding mechanism and a working fluid heating mechanism , the device comprising a cooling exchanger intended to extract heat from at least one member by supplying it with a refrigeration power determined by heat exchange with the working fluid circulating in the working circuit after its expansion in the expansion mechanism , the compression mechanism comprising at least one electric motor rotating a shaft carrying at least one compressor wheel at a speed of rotation controlled between a minimum speed and a maximum design speed determined by the characteristics of the engine, the device being of the variable refrigeration power type controlled by regulating the rotational speed of the motor, the device comprising an electronic controller configured to control the refrigeration power supplied from the refrigerating device by controlling the rotational speed of the motor, the electronic controller being configured to receiving a determined cold power demand signal to be delivered and, in response, for controlling the rotational speed of the engine to deliver said cold power demand.

The invention relates in particular to the management of the load of a cryogenic machine from a set point coming from a customer system/from an operator to be cooled, while leaving the system self-secured.

The invention relates in particular to managing the speed of an autonomous motor in the event of poor conditions of use (insufficient flow rate to be cooled, temperature of the fluid to be cooled which is already too cold, etc.). For this type of device, the cold power supplied is a function of the speed of the motors. The higher the engine speed, the more cold power the machine will deliver to the customer fluid. When the machine is in nominal operation (cooling of the customer fluid), the temperature of the working fluid is imposed by the temperature of the customer fluid. The internal regulation point of the machine is based on the temperature of the working fluid. That is, the speed controller will adjust the motor speed to maintain that working fluid temperature at that setpoint. If this measured temperature of the working fluid exceeds the setpoint, the motor accelerates. On the contrary, if this measured temperature of the working fluid is below the setpoint, the motor decelerates. This setpoint is generally colder than the setpoint temperature of the customer fluid to be cooled. The speed controller will request an acceleration of the motor speed, without having any effect on the temperature of the working fluid, but will achieve an increase in the cold power supplied.

For these applications, it is known to use a PID type regulation, with a regulated parameter (motor speed) to maintain a measurement (cold power of the machine) at a certain setpoint (operating point coming from the customer).

The regulation of such a device is dependent on the quality of the parameter measurement. In the event of loss of one of the sensors on the cold power measurement chain, it is no longer possible to correctly regulate the load of the machine. Moreover, in the known systems, the responsiveness of the regulation is low because the system takes a certain time to reach the setpoint. Too fast a "PID" type adjustment there is the significant risk of oscillation of the load.

An object of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

To this end, the device according to the invention, moreover conforming to the generic definition given in the preamble above, is essentially characterized in that the electronic controller is configured to limit the maximum operating speed of the motor to a value less than or equal to the maximum design speed, in nominal operation, i.e. when the device supplies the determined cold power, the electronic controller being configured to fix the maximum operating speed of the motor at the rotational speed supplying the determined cold power and for regulating the rotational speed of the engine according to the demand for cold power without exceeding said maximum operating speed.

The controller will limit the motor speed up to the maximum value. The invention therefore consists in regulating the power delivered by modifying the maximum speed which can be requested by the speed controller. Regulation on the target temperature of the working fluid to be reached remains active. Thanks to the management of the maximum speed of the motor(s), it is thus possible to regulate the cold power delivered by the machine to the customer fluid to be cooled.

le contrôleur électronique est un contrôleur de vitesse comprenant un microprocesseur et/ou un ordinateur,
le dispositif comprend au moins un capteur de température du fluide de travail dans le circuit de travail, par exemple à une entrée et/ou à une sortie du mécanisme de détente, le contrôleur électronique étant configuré pour recevoir la mesure du au moins un capteur de température,
le contrôleur électronique est configuré pour piloter la vitesse de rotation du moteur pour atteindre une valeur cible de température au niveau du au moins un capteur de température,
le contrôleur électronique est configuré pour calculer la valeur de vitesse de rotation du moteur en fonction de la demande de puissance froide via une formule obtenue par une fonction de régression des mesures réelles de performance du dispositif,
la fonction de régression est une fonction polynomiale de degré supérieur ou égal à deux de la puissance froide, ladite formule et notamment les coefficients de la fonction polynomiale étant calculée à partir de mesures réelles de performance du dispositif,
le mécanisme de compression comprend une ou plusieurs roues de compresseurs disposées le cas échéant en série et/ou en parallèle dans le circuit de travail formant un ou plusieurs étages de compression pour le fluide de travail, la ou les roues de compresseur étant entrainées en rotation par un ou plusieurs moteurs, le mécanisme de détente comprenant une ou plusieurs turbines de disposées le cas échéant en série et/ou en parallèle dans le circuit de travail formant un ou plusieurs étages de détente pour le fluide de travail, au moins l’une des turbines étant montée sur le même arbre d’un moteur entraînant en rotation au moins une roue de compresseur,
le dispositif comprend plusieurs moteurs, le contrôleur électronique étant configuré pour piloter la vitesse de rotation de tout ou partie des moteurs pour fournir ladite demande de puissance froide,
l’échangeur de refroidissement destiné à extraire de la chaleur à au moins un organe comprend un passage de circulation de fluide pour refroidir un organe constitué d’un flux de fluide.

Further, embodiments of the invention may include one or more of the following features:

the electronic controller is a speed controller comprising a microprocessor and/or a computer,
the device comprises at least one working fluid temperature sensor in the working circuit, for example at an inlet and/or at an outlet of the expansion mechanism, the electronic controller being configured to receive the measurement from the at least one temperature sensor temperature,
the electronic controller is configured to control the speed of rotation of the motor to reach a target temperature value at the level of the at least one temperature sensor,
the electronic controller is configured to calculate the rotational speed value of the motor according to the cold power demand via a formula obtained by a regression function of the actual performance measurements of the device,
the regression function is a polynomial function of degree greater than or equal to two of the cold power, said formula and in particular the coefficients of the polynomial function being calculated from real measurements of the performance of the device,
the compression mechanism comprises one or more compressor wheels arranged, where appropriate, in series and/or in parallel in the working circuit forming one or more compression stages for the working fluid, the compressor wheel(s) being driven in rotation by one or more motors, the expansion mechanism comprising one or more turbines arranged in series and/or in parallel, where appropriate, in the working circuit forming one or more expansion stages for the working fluid, at least one turbines being mounted on the same shaft of an engine rotating at least one compressor wheel,
the device comprises several motors, the electronic controller being configured to control the speed of rotation of all or part of the motors to supply said cold power demand,
the cooling exchanger intended to extract heat from at least one member comprises a fluid circulation passage for cooling a member consisting of a flow of fluid.

The invention also relates to a method for refrigerating at low temperature, that is to say at a temperature between minus 100 degrees centigrade and minus 273 degrees centigrade, of an organ such as a fluid flow by using a device refrigeration unit conforming to any one of the characteristics above or below, comprising regulation of the cold power delivered by the device by controlling the maximum operating speed of the motor.

According to a possible feature, the method comprises a step of receiving a determined cold power demand signal to be delivered by the device, a step of determining a determined rotational speed of the engine to deliver said power demand, a step of fixing from the maximum operating speed to the value of the determined rotational speed and a step of maintaining the rotational speed of the engine at said maximum operating speed.

The invention may also relate to any alternative device or method comprising any combination of the characteristics above or below within the scope of the claims.

Other features and advantages will appear on reading the description below, made with reference to the figures in which:

schematically and partially represents a first example of structure and operation of a refrigeration device according to the invention,

schematically and partially represents a second example of structure and operation of a refrigeration device according to the invention,

schematically and partially represents a third example of structure and operation of a refrigeration device according to the invention,

schematically and partially represents an example of variation of the cold power produced by such a device as a function of the rotational speed of the engine,

schematically and partially represents an example of control of the regulation of the rotational speed of the motor.

The device 1 for cryogenic refrigeration, that is to say operating at a low temperature comprised for example between minus 100 degrees centigrade and minus 273 degrees centigrade, comprises a working circuit 10 forming a loop and containing a working fluid.

The working circuit 10 forms a cycle comprising in series: a mechanism 2, 3 for compressing the working fluid, a mechanism 6, 16 for cooling the working fluid, a mechanism 7 for expanding the working fluid and a mechanism 6, 8 working fluid warming.

The device 1 comprises a cooling exchanger 8 intended to extract heat from at least one organ 25 or user by supplying it with a refrigeration power P determined by heat exchange with the working fluid circulating in the working circuit 10 after its trigger in the trigger mechanism 7. The cooling exchanger 8 intended to extract heat from at least one member 25 comprises, for example, a fluid circulation passage for cooling a member 25 consisting, for example, of a flow of fluid to be cooled.

The compression mechanism 2, 3 comprises at least one electric motor 11 rotating a shaft 15 carrying at least one compressor wheel 2 at a rotational speed controlled between a minimum speed and a maximum design speed Vmc of the engine which is determined for example by the design and manufacturing characteristics of the engine 11.

As illustrated in the various examples, the compression mechanism 2, 3 may comprise one or more compressor wheels 2 arranged, where appropriate, in series and/or in parallel in the working circuit 10 and forming one or more compression stages for the working fluid. The compressor wheel(s) 2 may be driven in rotation by one or more motors 11. The expansion mechanism 7 may comprise one or more turbines 7 (and/or expansion valve(s)) arranged where appropriate in series and/or in parallel in the working circuit 10 forming one or more expansion stages for the working fluid.

At least one of the turbines 7 can be mounted on the same shaft 15 of a motor 11 rotating at least one wheel 2 of the compressor.

The refrigeration device is of the type with variable refrigeration power P controlled by regulating the speed V of rotation of the motor 11.

For example, and as schematized in , this speed can be determined from a characteristic curve giving the cold power P as a function of the rotational speed of the engine. Note that the curve represented by way of example is a parabolic function, however this is in no way limiting.

For example, the electronic controller 12 can be configured to calculate the motor rotation speed value V according to the cold power demand via a formula in which said speed is given by a polynomial function of degree greater than or equal to two of the cold power P, said formula being predefined (established or calculated) from real measured performance measurements of the device 1.

For example, these actual values are measured on one device and the coefficients (the formula) can be defined for a whole range of identical devices (or each time for each machine).

As illustrated, the device 1 comprises an electronic controller 12 configured to control the refrigeration power P supplied by the refrigeration device 1 by controlling the speed V of rotation of the motor or motors 11. That is to say that, when there are several motors, the electronic controller 12 can be configured to control the speed V of rotation of all or part of the motors 11 to supply said cold power demand.

The electronic controller 12 is for example a speed controller comprising a microprocessor and/or a computer. It can be integrated into the device 1 or at least partly remote.

The electronic controller 12 is in particular configured to receive a cold power request signal 13 P determined to be delivered and, in response, to control the speed V of rotation of the motor 11 to supply said cold power request.

According to an advantageous feature, the electronic controller 12 is configured to limit the maximum operating speed Vmf of the motor 11 to a value less than or equal to the maximum design speed Vmc. In addition, in nominal operation, that is to say when the device 1 supplies the determined cold power, the electronic controller 12 is configured to set the maximum operating speed Vmf of the motor at the speed of rotation supplying the cold power P determined and to regulate the speed V of rotation of the engine according to the demand for cold power without exceeding said maximum operating speed Vmf. (for example Vmf is a percentage of Vmc Cf. ).

That is to say that, in operation, the speed of the motor can be varied according to the cold power P requested.

The maximum operating speed Vmf of the motor can be fixed for example at the start-up of the device 1 (at the start-up of the installation), it is the real speed which makes it possible to deliver the nominal power requested by the customer or user 25. By “ nominal operation" means, for example, the operation of the device when it supplies 100% of the nominal power.

This makes it possible to quickly reach the cold power setpoint to be supplied compared to a known PID type regulation. This solution also allows greater responsiveness to reach the set point for the application to be cooled (pressure, temperature, etc.).

This can make operation independent of actual cold power measurements delivered. This avoids a possible regulation error in the event of a bad measurement (drift of a sensor for example).

For example, the device 1 comprises at least one temperature sensor 9, 19 of the working fluid in the working circuit 10, for example at an inlet and/or at an outlet of the expansion mechanism 7 and the electronic controller 12 is configured to receive the measurement 14 from at least one temperature sensor 9, 19.

For example, the electronic controller 12 is configured to drive the speed V of rotation of the motor 11 to reach a target temperature value at the level of at least one temperature sensor 9, 19 in the working circuit.

The temperature target can be constant and equal to the cold temperature requested by the customer application to be cooled.

The regulation system can be autonomous with regard to temperature management (the controller 12 remains active because only the maximum speed is regulated). In the event of a problem with the flow rate of the fluid to be cooled 25 (stopping of a pump or other), the controller 12 can adjust the speed of rotation of the motor so as not to fall below the set temperature of the working fluid.

The maximum operating speed of the motor Vmf is preferably limited to a value strictly lower than the maximum design speed of the motor Vmc.

In other applications, it is possible that the maximum motor operating speed Vmf is equal to the maximum design motor speed Vmc. In these applications (in the liquefaction of a biomethane for example), the temperature of the customer fluid to be cooled (for example at the outlet of the cooling exchanger) is taken as a control parameter for regulating the speed of the motor(s). The measured temperature leads to a correction of the target temperature setpoint which then leads to a variation of the speed setpoint of the motor(s) (for example as a percentage % of the maximum operating speed of the motor.

Claims

Device for refrigerating at low temperature, in particular cryogenic, that is to say at a temperature between minus 100 degrees centigrade and minus 273 degrees centigrade, comprising a working circuit (10) forming a loop and containing a working fluid, the working circuit (10) forming a cycle comprising in series: a mechanism (2, 3) for compressing the working fluid, a mechanism (6, 16) for cooling the working fluid, a mechanism (7) for expanding the working fluid and a mechanism (6, 8) for heating the working fluid, the device (1) comprising a cooling exchanger (8) intended to extract heat from at least one member (25) by supplying it with power (P) refrigeration determined by heat exchange with the working fluid circulating in the working circuit (10) after its expansion in the expansion mechanism (7), the compression mechanism (2, 3) comprising at least one motor (11) electric rotating a shaft (15) carrying at least one compressor wheel (2) at a speed of rotation controlled between a minimum speed and a maximum design speed (Vmc) determined by the characteristics of the engine (11) , the device (1) being of the type with variable refrigeration power (P) controlled by regulating the speed (V) of rotation of the motor (11), the device (1) comprising an electronic controller (12) configured to control the power (P) of refrigeration supplied by the refrigeration device (1) by controlling the speed (V) of rotation of the motor (11), the electronic controller (12) being configured to receive a power demand signal (13) (P ) cold determined to deliver and, in response, to control the speed (V) of rotation of the motor (11) to supply said demand for cold power, characterized in that the electronic controller (12) is configured to limit the maximum speed of operation (Vmf) of the motor (11) at a value less than or equal to the maximum design speed (Vmc) and in that, in nominal operation, that is to say when the device (1) provides cold power determined, the electronic controller (12) is configured to fix the maximum operating speed (Vmf) of the motor at the speed of rotation supplying the determined cold power (P) and to regulate the speed (V) of rotation of the motor according to the cold power demand without exceeding said maximum operating speed (Vmf).
Device according to Claim 1, characterized in that the electronic controller (12) is a speed controller comprising a microprocessor and/or a computer.
Device according to Claim 1 or 2, characterized in that it comprises at least one sensor (9, 19) for the temperature of the working fluid in the working circuit (10), for example at an inlet and/or at an outlet. of the expansion mechanism (7), the electronic controller (12) being configured to receive the measurement (14) from the at least one temperature sensor (9, 19).
Device according to Claim 3, characterized in that the electronic controller (12) is configured to control the speed (V) of rotation of the motor (11) to reach a target temperature value at the level of the at least one sensor (9, 19 ) of temperature.
Device according to any one of Claims 1 to 4, characterized in that the electronic controller (12) is configured to calculate the value of the rotational speed (V) of the motor as a function of the demand for cold power via a formula obtained by a regression function of the actual performance measurements of the device (1).
Device according to Claim 5, characterized in that the regression function is a polynomial function of degree greater than or equal to two of the cold power, the said formula and in particular the coefficients of the polynomial function being calculated from real performance measurements of the device (1).
Device according to any one of Claims 1 to 6, characterized in that the compression mechanism (2, 3) comprises one or more compressor wheels (2) arranged, where appropriate, in series and/or in parallel in the circuit ( 10) working forming one or more compression stages for the working fluid, the compressor wheel or wheels (2) being driven in rotation by one or more motors (11), the expansion mechanism (7) comprising one or more turbines (7) arranged in series and/or in parallel, where appropriate, in the working circuit (10) forming one or more expansion stages for the working fluid, at least one of the turbines (7) being mounted on the same shaft (15) of a motor (11) rotating at least one compressor wheel (2).
Device according to Claim 7, characterized in that it comprises several motors (11), the electronic controller (12) being configured to control the speed (V) of rotation of all or part of the motors (11) to supply the said request for cold power.
Device according to any one of Claims 1 to 8, characterized in that the cooling exchanger (8) intended to extract heat from at least one member (25) comprises a fluid circulation passage for cooling a member ( 25) consisting of a flow of fluid.
Method of refrigerating at low temperature, that is to say at a temperature between minus 100 degrees centigrade and minus 273 degrees centigrade, a member (25) such as a fluid stream using a refrigeration device to any one of claims 1 to 9, comprising regulation of the cold power delivered by the device (1) by controlling the maximum operating speed (Vmf) of the motor (1).
Method according to Claim 10, characterized in that it comprises a step of receiving a signal (13) requesting determined cold power (P) to be delivered by the device (1), a step of determining a speed of determined rotation (V) of the engine to supply said power demand, a step of fixing the maximum operating speed (Vmf) to the value of the determined rotation speed and a step of maintaining the speed (V) of rotation of the engine at said maximum operating speed (Vmf).