Refrigeration device and method

Abstract

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

1 - 11 . (canceled) 
     
     
         12 . A refrigeration device refrigerating to a low temperature that is between minus 100 degrees centigrade and minus 273 degrees centigrade, the refrigeration device comprising:
 a working circuit forming a loop and containing a working fluid, the working circuit forming a cycle comprising, in series:
 a compression mechanism for compressing the working fluid, the compression mechanism comprising at least one electric motor driving the rotation of a shaft bearing at least one compressor impeller at a rotational speed that is controlled between a minimum speed and a maximum design speed, which is determined by the characteristics of the motor 
 a cooling mechanism for cooling the working fluid, 
 an expansion mechanism for expanding the working fluid, and 
 a heating mechanism for warming the working fluid, 
   a cooling exchanger intended to extract heat from at least one member by supplying it a determined refrigeration power through exchange of heat with the working fluid circulating in the working circuit after the working fluid has been expanded in the expansion mechanism,   wherein the refrigeration device has a variable refrigeration power that is controlled by regulating the rotational speed of the motor,   an electronic controller configured to control the refrigeration power supplied by the refrigeration device by controlling the rotational speed of the motor, the electronic controller being configured to receive a demand signal demanding the determined cold power to be delivered and, in response, to control the rotational speed of the motor in order to meet said cold-power demand,   wherein 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 and in that, in nominal operation, which is to say when the device is supplying the determined cold power, the electronic controller is configured to set the maximum operating speed of the motor to the rotational speed that supplies the determined cold power and to regulate the rotational speed of the motor as a function of the demand for cold power without exceeding said maximum operating speed.   
     
     
         13 . The device as claimed in  claim 12 , wherein the electronic controller is a speed controller comprising a microprocessor and/or a computer. 
     
     
         14 . The device as claimed in  claim 12 , further comprising at least one temperature sensor sensing the temperature of the working fluid 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. 
     
     
         15 . The device as claimed in  claim 14 , wherein the electronic controller is configured to control the rotational speed of the motor in order to achieve a target temperature value at the at least one temperature sensor. 
     
     
         16 . The device as claimed in  claim 12 , wherein the electronic controller is configured to calculate the value for the rotational speed of the motor as a function of the demand for cold power using a formula obtained as a regression function of the actual measurements of the performance of the device. 
     
     
         17 . The device as claimed in  claim 16 , wherein the regression function is a polynomial function, of degree greater than or equal to two, of the cold power, said formula, and notably the coefficients of the polynomial function, being calculated from actual measurements of the performance of the device. 
     
     
         18 . The device as claimed in  claim 12 , wherein the compression mechanism comprises one or more compressor impellers arranged, where applicable, in series and/or in parallel in the working circuit and forming one or more compression stages for the working fluid, the compressor impeller or impellers being driven in rotation by one or more motors, the expansion mechanism comprising one or more turbines positioned, where applicable, in series and/or in parallel in the working circuit and forming one or more expansion stages for the working fluid, at least one of the turbines being mounted on the same shaft of a motor driving the rotation of at least one compressor impeller. 
     
     
         19 . The device as claimed in  claim 18 , further comprising several motors, the electronic controller being configured to control the rotational speed of all or some of the motors in order to meet said demand for cold power. 
     
     
         20 . The device as claimed in  claim 12 , wherein the cooling exchanger intended to extract heat from at least one member comprises a fluid circulation passage for cooling a member consisting of a stream of fluid. 
     
     
         21 . A refrigeration method for refrigerating to a low temperature, which is to say to a temperature comprised between minus 100 degrees centigrade and minus 273 degrees centigrade, a member such as a stream of fluid, using the refrigeration device as claimed in  claim 12 , comprising the step of regulating the cold power delivered by the refrigeration device by controlling the maximum operating speed of the motor. 
     
     
         22 . The method as claimed in  claim 21 , further comprising a step of receiving a demand signal demanding a determined cold power that is to be delivered by the device, a step of determining a determined rotational speed of the motor in order to meet said demand for power, a step of setting the maximum operating speed to the determined rotational speed value and a step of maintaining the rotational speed of the motor at said maximum operating speed.