Controller and Method for Controlling Operation of a Refrigerant Circuit

Abstract

The invention refers to a controller for controlling operation of a refrigerant circuit, which refrigerant circuit comprises a compressor arrangement, a heat releasing heat exchanger heating an external medium, for example ambient air, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, in particular a refrigerant circuit for transport refrigeration.

1 . Controller for controlling operation of a refrigerant circuit, which refrigerant circuit comprises a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, in particular a refrigerant circuit for transport refrigeration,
 said controller controlling at least one of
 a first actuator driving said compressor arrangement such that a first parameter detected by said controller meets a predefined first parameter setting associated with said compressor arrangement, 
 a second actuator driving a blower arrangement associated with said heat releasing heat exchanger such that a second parameter detected by said controller meets a predefined second parameter setting associated with said heat releasing heat exchanger and 
 a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger such that a third parameter detected by said controller meets a predefined third parameter setting associated with said heat absorbing heat exchanger. 
   
     
     
         2 . Controller according to  claim 1 , wherein said controller ( 120 ) optimizes the energy efficiency of said refrigerant circuit ( 40 ) during operation, which energy efficiency comprises an optimization of at least one of i) the COP and ii) the energy consumption of the at least one actuator controlled in order to meet the respective parameter setting by an optimization process comprising
 varying the respective predefined parameter setting by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting,   waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change and   in case the change of the energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and   in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said parameter setting.   
     
     
         3 . Controller according to  claim 2 , wherein said optimizing process is repeated. 
     
     
         4 . Controller according to  claim 2 , wherein
 said controller optimizes the energy efficiency of said refrigerant circuit during operation, which energy efficiency comprises an optimization of at least one of i) the COP and ii) the energy consumption of at least two of the actuators controlled in order to meet the respective parameter, by an optimization process comprising
 varying a selected one of the predefined parameter settings by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, 
 waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change and 
   in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said selected parameter setting.   
     
     
         5 . Controller according to  claim 4 , wherein said optimization process changes only one predefined parameter setting at a time. 
     
     
         6 . Controller according to  claim 4 , wherein according to said optimization process changing one selected parameter setting by one step of change is followed by again changing the same parameter setting before selecting a further parameter setting. 
     
     
         7 . Controller according to  claim 4 , wherein according to the optimization process changing of one selected parameter setting by one step of change is followed by selecting a further parameter setting and changing said further parameter setting by one step of change. 
     
     
         8 . Controller according to  claim 1 , wherein the parameters and the corresponding parameter settings are temperature based. 
     
     
         9 . Controller according to  claim 8 , wherein the parameters and the parameter settings are based on temperatures detected at the refrigerant circuit. 
     
     
         10 . Controller according to  claim 1 , wherein the first parameter and the first parameter setting are based on a temperature detected close to the heat absorbing heat exchanger. 
     
     
         11 . Controller according to  claim 10 , wherein the first parameter and the first parameter setting relate to the temperature of the flow of gaseous medium through the heat absorbing heat exchanger, in particular the temperature of return flow of gaseous medium. 
     
     
         12 . Controller according to  claim 1 , wherein the second parameter and the second parameter setting are based on a temperature indicating the operation of the heat releasing heat exchanger. 
     
     
         13 . Controller according to  claim 12 , wherein the second parameter and the second parameter setting are based on a temperature difference between the saturated discharge temperature detected at the compressor arrangement and the ambient temperature detected close to the heat releasing heat exchanger. 
     
     
         14 . Controller according to  claim 1 , wherein the third parameter and the third parameter setting are based on the temperature in the storage volume. 
     
     
         15 . Controller according to  claim 14 , wherein the third parameter and the third parameter setting are based on the maximum temperature variation in the space within the storage volume surrounding the cargo. 
     
     
         16 . Controller according to  claim 1 , wherein a step width of the respective step of change is within the range from 0.1 K to 4 K. 
     
     
         17 . Controller according to  claim 1 , wherein a step width of the step of change is variable between a maximum step width and a minimum step width. 
     
     
         18 . Controller according to  claim 17 , wherein for each parameter setting the optimization process starts with a maximum step width and reduces the step width if the change of energy efficiency is reduced in relation to the change of energy efficiency obtained in the course of the preceding step. 
     
     
         19 . Controller according to  claim 1 , wherein the controller detects, permanently or at least after defined time periods, a cargo temperature by at least one cargo temperature sensor and compares it to a given maximum admissible cargo temperature and in case the given maximum admissible cargo temperature is reached at least one of the first and second parameter settings are changed in order to reduce the cargo temperature. 
     
     
         20 . Controller according to  claim 1 , wherein the respective actuator is controlled in steps amounting to less than 10% of the available control range of said actuator. 
     
     
         21 . Controller according to  claim 1 , wherein the respective actuator is continuously controlled within the available control range. 
     
     
         22 . Controller according to  claim 1 , wherein the predefined parameter settings are stored in a memory of said controller. 
     
     
         23 . Controller according to  claim 22 , wherein several operational data sets each comprising the parameter settings which refer to different environmental conditions are stored in the memory. 
     
     
         24 . Controller according to  claim 23 , wherein different day time related operational data sets are provided. 
     
     
         25 . Controller according to  claim 23 , wherein different location related data sets are provided. 
     
     
         26 . Controller according to  claim 1 , wherein the controller detects environmental conditions. 
     
     
         27 . Controller according to  claim 1 , wherein the controller is provided with a remote access unit. 
     
     
         28 . Controller according to  claim 1 , wherein the controller comprises a processor for controlling said actuators and for performing said optimization process. 
     
     
         29 . Controller according to  claim 1 , wherein said controller comprises an input/output unit for operating the actuators and detecting the parameters. 
     
     
         30 . Method for controlling operation of a refrigerant circuit, which refrigerant circuit comprises a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume, in particular a refrigerant circuit for transport refrigeration,
 said method providing controlling at least one of
 a first actuator driving said compressor arrangement such that a first parameter detected at said refrigerant circuit ( 40 ) meets a predefined first parameter setting associated with said compressor arrangement, 
 a second actuator driving a blower arrangement associated with said heat releasing heat exchanger such that a second parameter detected at said refrigerant circuit meets a predefined second parameter setting associated with said heat releasing heat exchanger and 
 a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger such that a third parameter detected at said refrigerant circuit meets a predefined third parameter setting associated with said heat absorbing heat exchanger. 
   
     
     
         31 . Method according to  claim 30 , wherein said method optimizes the energy efficiency of said refrigerant circuit, during operation, which energy efficiency comprises an optimization of at least one of i) the COP and ii) the energy consumption of the at least one actuator controlled in order to meet the respective parameter setting
 by an optimization process comprising
 varying the respective predefined parameter setting by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, 
 waiting for a defined period of time for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change and 
   in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and
 in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said parameter setting. 
   
     
     
         32 . Method according to  claim 31 , wherein said optimizing process is repeated. 
     
     
         33 . Method according to  claim 31 , wherein said method optimizes the energy efficiency of said refrigerant circuit during operation, which energy efficiency comprises an optimization of at least one of i) the COP and ii) the energy consumption of the at least two of the actuators controlled in order to meet the respective parameter setting
 by an optimization process comprising
 varying a selected one of the predefined parameter setting by a step of change in a predefined direction of change increasing or decreasing the respective parameter setting, 
 waiting for a defined period of time, for example in order to obtain a thermodynamic thermal equilibrium at the refrigerant circuit, thereafter determining the change of energy efficiency of the refrigerant circuit obtained by said step of change, and 
   in case the change of energy efficiency corresponds to an improved energy efficiency the parameter setting amended by said step of change and said direction of change are maintained and stored as predefined parameters for the next variation of said selected parameter setting, and in case the change of energy efficiency does not correspond to an improved energy efficiency the parameter setting preceding said step of change is maintained and said direction of change is inverted and stored as predefined parameters for the next variation of said parameter setting.   
     
     
         34 . Method according to  claim 33 , wherein said optimization process changes only one predefined parameter setting at a time. 
     
     
         35 . Method according to  claim 33 , wherein according to said optimization process changing one selected parameter setting by one step of change is followed by again changing the same parameter setting before selecting the further parameter setting. 
     
     
         36 . Method according to  claim 33 , wherein according to the optimization process changing of one selected parameter setting by one step of change is followed by selecting a further parameter setting and changing said further parameter setting by one step of change. 
     
     
         37 . Method according to  claim 30 , wherein the parameters and the corresponding parameter settings are temperature based. 
     
     
         38 . Method according to  claim 37 , wherein the parameters and the parameter settings are based on temperatures detected at the refrigerant circuit. 
     
     
         39 . Method according to  claim 30 , wherein the first parameter and the first parameter setting are based on a temperature detected close to the heat absorbing heat exchanger. 
     
     
         40 . Method according to  claim 39 , wherein the first parameter and the first parameter setting relate to the temperature of the flow of gaseous medium through the heat absorbing heat exchanger, in particular the temperature of return flow of gaseous medium. 
     
     
         41 . Method according to  claim 30 , wherein the second parameter and the second parameter setting are based on a temperature indicating the operation of the heat releasing heat exchanger. 
     
     
         42 . Method according to  claim 41 , wherein the second parameter and the second parameter setting are based on to a temperature difference between the saturated discharge temperature detected at the compressor arrangement and the ambient temperature detected close to the heat releasing heat exchanger. 
     
     
         43 . Method according to  claim 30 , wherein the third parameter and the third parameter setting are based on the temperature in the storage volume. 
     
     
         44 . Method according to  claim 43 , wherein the third parameter and the third parameter setting are based on to the maximum temperature variation in the space within the storage volume surrounding the cargo. 
     
     
         45 . Method according to  claim 30 , wherein a step width of the respective step of change is within the range from 0.1 K to 4 K. 
     
     
         46 . Method according to  claim 30 , wherein a step width of the step of change is variable between a maximum step width and a minimum step width. 
     
     
         47 . Method according to  claim 46 , wherein for each parameter setting the optimization process starts with a maximum step width and reduces the step width if the change of energy efficiency is reduced in relation to the change of energy efficiency obtained in the course of the preceding step. 
     
     
         48 . Method according to  claim 30 , wherein the method provides detection, permanently or at least after defined time periods, of a cargo temperature by at least one cargo temperature sensor and compares it to a given maximum admissible cargo temperature and in case the given maximum admissible cargo temperature is reached at least one of the first and second parameter settings are changed in order to reduce the cargo temperature. 
     
     
         49 . Method according to  claim 30 , wherein the respective actuator is controlled in steps amounting to less than 10% of the available control range of said actuator. 
     
     
         50 . Method according to  claim 30 , wherein the respective actuator is continuously controllable within the available control range. 
     
     
         51 . Method according to  claim 30 , wherein the predefined parameter settings are stored in a memory. 
     
     
         52 . Method according to  claim 51 , wherein several operational data sets each comprising the parameter settings which refer to different environmental conditions are provided. 
     
     
         53 . Method according to  claim 52 , wherein different day time related operational data sets are provided. 
     
     
         54 . Method according to  claim 52 , wherein different location related data sets are provided. 
     
     
         55 . Method according to  claim 30 , wherein said method is remotely accessible. 
     
     
         56 . Refrigerant circuit in particular a refrigerant circuit for transport refrigeration, comprising a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in a storage volume,
 a first actuator driving said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger,   a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger, said refrigerant circuit comprising a controller for controlling operation of a refrigerant circuit, according to  claim 1 .   
     
     
         57 . Storage unit comprising an insulated housing enclosing a storage volume within which temperature sensitive cargo is received and surrounded by a gaseous medium, and a refrigerant circuit comprising a compressor arrangement, a heat releasing heat exchanger heating an external medium, a heat absorbing heat exchanger cooling a flow of gaseous medium through said heat absorbing heat exchanger for cooling cargo arranged in the storage volume,
 a first actuator driving said compressor arrangement, a second actuator driving a blower arrangement associated with said heat releasing heat exchanger,   a third actuator driving a blower arrangement associated with said heat absorbing heat exchanger, said refrigerant circuit comprising a controller for controlling operation of a refrigerant circuit, according to  claim 1 .