Speed control strategy for condenser fan in refrigeration system

Abstract

A refrigeration system (10) is disclosed that includes a refrigeration circuit (12) that includes a compressor (14), a condenser (18), an expansion valve (22), and an evaporator (26). A condenser fan (29) of the refrigeration system (10) is configured to operate at a condenser fan speed that is set based on current refrigeration demands of the system (10) under control of a controller (35).

Description

Technical Field

[0001] The present invention relates to a refrigeration system, such as a transport refrigeration system, and particularly to a speed control strategy for a condenser fan in a refrigeration system. Background Technology

[0002] A refrigeration system typically includes a refrigeration circuit, which comprises a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration circuit generally defines the flow of refrigerant used to control the temperature of the space to be cooled. The refrigerant flow can be described as beginning with the compressor, which compresses the refrigerant to form a superheated refrigerant gas. This superheated refrigerant gas is then delivered to the condenser, which is in thermal communication with the cooler surrounding environment, thereby removing heat from the refrigerant into the environment. The refrigerant, now condensed into a liquid, is then delivered from the condenser to the evaporator via the expansion valve. The evaporator is in thermal communication with the space to be cooled. As air in this space flows over the evaporator, the liquid refrigerant evaporates and absorbs heat from the air to cool the space. To complete the cycle around the refrigeration circuit, the refrigerant is returned from the evaporator to the compressor, for example, via an electronic throttling valve.

[0003] Typically, a condenser fan is installed to circulate air across the condenser, helping to remove heat from the refrigerant. The condenser fan is usually mechanically or electrically coupled to the prime mover of the refrigeration system and is configured to operate at a fixed, i.e., constant speed, which is a fixed ratio of the prime mover speed. There are usually at least two available prime mover speeds, such as high speed and low speed, and the condenser fan will also have two speeds proportionally.

[0004] A fixed fan speed is chosen to ensure sufficient airflow to the condenser during worst-case operating conditions. For example, the condenser fan might be set to operate at a fixed speed high enough to meet the system's maximum potential cooling demands. High heat dissipation typically occurs when the refrigeration system has a high capacity (such as during pull-down operation due to a warm refrigerated space). At higher ambient temperatures, heat dissipation is more difficult and generally requires more airflow, so the condenser fan is set to an appropriate fixed speed for this purpose. However, in many cases, the system is not in pull-down mode but maintains a given temperature by, for example, performing continuous cooling regulation, where the cooling capacity and therefore heat dissipation are much lower. Additionally, the ambient temperature is typically not as high as the temperature designed for worst-case conditions.

[0005] Therefore, the speed of the condenser fan in a conventional refrigeration system and the resulting power consumption are typically higher than the speed and power consumption required to meet the system's current heat dissipation demand (e.g., when the current cooling demand is lower than the maximum potential cooling capacity corresponding to a fixed speed).

[0006] Therefore, improved speed control for the condenser fan is desired. Summary of the Invention

[0007] According to one aspect of the present invention, a refrigeration system is provided, comprising: a refrigeration circuit including at least a compressor, a condenser, an expansion valve, and an evaporator; a variable-speed condenser fan; and a controller configured to monitor the refrigeration demand of the refrigeration system in a first operating mode (e.g., using one or more sensors) and to set the speed of the condenser fan based on the current refrigeration demand of the system.

[0008] The controller can be configured to: monitor a set of operating parameters of the refrigeration circuit indicating cooling demand; and set the condenser fan speed based on the current values ​​of the set of operating parameters.

[0009] A set of operating parameters (monitored and used to set the condenser fan speed) may include one or more of compressor speed, condenser inlet temperature, evaporator inlet temperature, evaporator fan speed, and throttle valve position (in embodiments, all of these may be included). Alternatively, a set of operating parameters (monitored and used to set the condenser fan speed) may include one or more of compressor speed, compressor suction pressure, condenser discharge pressure, and throttle valve position (in embodiments, all of these may be included).

[0010] The controller can be configured to monitor a first set of operating parameters and different second sets of operating parameters, each indicating the cooling demand; and to interchangeably set the condenser fan speed based on the current values ​​of the first and second sets of operating parameters.

[0011] The controller can be configured to: in a first operating mode, set the condenser fan speed by default based on the current values ​​of a first set of operating parameters, and if the controller detects a fault in one or more sensors used to monitor the first set of operating parameters, set the condenser fan speed based on the current values ​​of a second set of operating parameters.

[0012] The controller can be configured to set the condenser fan speed based on a predetermined model of system efficiency, which can be a function of a set of operating parameters and the condenser fan speed. The predetermined model can be a meta-model pre-defined based on statistical analysis of a set of simulation data representing the system efficiency across the entire operating curve of the refrigeration system.

[0013] The controller can be configured to set the speed of the condenser fan based on a predetermined relationship between the current operating parameter value and the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter value.

[0014] This predetermined relationship can be determined by performing regression analysis using a predetermined model. This predetermined relationship can be determined (e.g., by a computer processor) by using a predetermined model (e.g., a meta-model) to determine the individual condenser fan speeds at which the system efficiency will reach its maximum for each permutation of the operating parameter values; and by fitting a (e.g., a curve) function to the individual condenser fan speeds at which the system efficiency will reach its maximum for each permutation; and storing the function in memory for use by the controller.

[0015] The predetermined relationship can take the form of a regression model (e.g., by performing the function determined through the regression analysis described above), which can be stored in memory accessible to the controller. The regression model can be stored in the controller's own memory. The controller can be configured to: input the current operating parameter values ​​into the regression model; receive the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values ​​as the output of the regression model; and set the condenser fan to operate at a speed selected based on the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values.

[0016] Instead of a regression model, the predetermined relationship can be represented by a lookup table, which can be stored in memory accessible to the controller. The lookup table can be stored in the controller's own memory. The controller can be configured to: identify the entry in the lookup table corresponding to the current operating parameter value; read data from that entry indicating the condenser fan speed at which system efficiency will reach its maximum value for the current operating parameter value; and set the condenser fan to operate at a speed selected based on the condenser fan speed at which system efficiency will reach its maximum value for the current operating parameter value.

[0017] The controller can be configured to set the condenser fan speed based on a predetermined model of system efficiency by performing an optimization algorithm using the predetermined model to determine the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values.

[0018] Executing the optimization algorithm may include: for each condenser fan speed in a set of predefined condenser fan speeds; inputting the condenser fan speed and current operating parameter values ​​into a predetermined model of system efficiency; and receiving cooling capacity values ​​and fuel or power consumption values ​​as output data from the predetermined model of system efficiency. Executing the optimization algorithm may also include: based on the output data for a set of predefined condenser fan speeds, determining a predefined condenser fan speed that maximizes the system efficiency for the corresponding cooling capacity and fuel or power consumption values.

[0019] The refrigeration system may include a power supply for at least powering the controller and the condenser fan. Furthermore, the controller may be configured in a second operating mode to: determine the excess power capacity currently available from the power supply based on current power consumption and a predefined maximum power capacity of the power supply; determine the maximum speed at which the condenser fan can operate when utilizing the excess power capacity from the power supply; and set the condenser fan to operate at the determined maximum speed.

[0020] According to another aspect, a method for operating a variable-speed condenser fan of a refrigeration system is provided, the refrigeration system including a refrigeration circuit including at least a compressor, a condenser, an expansion valve, and an evaporator; the method includes: when operating in a first operating mode, a controller performs the following operations: monitoring the current refrigeration demand of the refrigeration system and setting the speed of the condenser fan based on the current refrigeration demand of the system.

[0021] The method may also include the controller performing the following operations: monitoring a set of operating parameters of a refrigeration circuit indicating cooling demand; and setting the condenser fan speed based on the current values ​​of the set of operating parameters.

[0022] As described above, a set of operating parameters may include one or more of the following: compressor speed, condenser inlet temperature, evaporator inlet temperature, evaporator fan speed, and throttle valve position. Alternatively, a set of operating parameters may include one or more of the following: compressor speed, compressor suction pressure, condenser discharge pressure, and throttle valve position.

[0023] The controller can monitor a first set of operating parameters and different second sets of operating parameters, each indicating the cooling demand; and can interchangeably set the condenser fan speed based on the current values ​​of the first and second sets of operating parameters.

[0024] The controller can set the condenser fan speed by default based on the current value of the first set of operating parameters in the first operating mode, and if the controller detects a fault in one or more sensors used to monitor the first set of operating parameters, it can set the condenser fan speed based on the current value of the second set of operating parameters.

[0025] The controller can set the condenser fan speed based on a predetermined model of system efficiency, which can be a function of a set of operating parameters and the condenser fan speed. As mentioned above, the predetermined model can be a meta-model predetermined based on a set of simulation data representing the system efficiency across the entire operating graph of the refrigeration system. Therefore, in this embodiment, the method includes the step of performing a statistical analysis on a set of simulation data representing the system efficiency across the entire operating graph of the refrigeration system.

[0026] The controller can set the condenser fan speed based on a predetermined relationship between the current operating parameter values ​​and the condenser fan speed at which the system efficiency will reach its maximum for the current operating parameter values. This predetermined relationship can have been determined by performing regression analysis using a predetermined model. Therefore, in an embodiment, the method may include the step of performing regression analysis using a predetermined model.

[0027] The predetermined relationship can take the form of a regression model, which is stored in memory accessible to the controller. In this case, the method may further include the controller performing the following operations: inputting the current operating parameter value into the regression model; receiving the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter value as the output of the regression model; and setting the condenser fan to operate at a speed selected based on the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter value.

[0028] Instead of a regression model, the predetermined relationship can be in the form of a lookup table stored in memory accessible to the controller. In this case, the method may further include the controller performing the following operations: identifying an entry in the lookup table corresponding to the current operating parameter value; reading data from the entry indicating the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter value; and setting the condenser fan to operate at a speed selected based on the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter value.

[0029] The controller can set the condenser fan speed based on a predetermined model of system efficiency by following these steps: executing an optimization algorithm using the predetermined model to determine the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values.

[0030] In the case where the refrigeration system includes a power supply for at least powering the controller and the condenser fan, the method may further include: when operating in a second operating mode, the controller performs the following operations: determining the excess power capacity that can be obtained from the power supply based on the current power consumption and the predefined maximum power capacity of the power supply; determining the maximum speed at which the condenser fan can operate when utilizing the excess power capacity from the power supply; and setting the condenser fan to operate at the determined maximum speed.

[0031] In the above embodiments, system efficiency can be defined with respect to a refrigeration system utilizing power generated by an internal combustion engine. In this case, system efficiency can be defined as the ratio of net cooling capacity (in watts) to fuel consumption (in liters per hour). Additionally or alternatively, system efficiency can be defined with respect to a refrigeration system utilizing power generated by an onboard electric motor. In this case, system efficiency can be defined as the ratio of net cooling capacity (in watts) to power consumption (in watts).

[0032] The various units or components described herein (such as unit controllers) may be coupled to each other via wireless links and thus may include transceiver circuitry and one or more antennas. Additionally or alternatively, the units described herein may be coupled to each other via wired links and thus may include interface circuitry (such as a Universal Serial Bus (USB) socket). It should be understood that the units described herein may be coupled to each other via any combination of wired and wireless links.

[0033] The various units described herein may include any suitable circuitry to perform the methods described herein and illustrated in the figures. Modules may include: at least one application-specific integrated circuit (ASIC); and / or at least one field-programmable gate array (FPGA); and / or a single-processor or multi-processor architecture; and / or a sequential (von Neumann) / parallel architecture; and / or at least one programmable logic controller (PLC); and / or at least one microprocessor; and / or at least one microcontroller; and / or a central processing unit (CPU); and / or a graphics processing unit (GPU) to perform these methods.

[0034] Each unit may include one or more memories (e.g., non-transitory computer-readable storage media) and / or communicate with the one or more memories that store the data described herein and / or store software (computer-readable instructions) for performing the processes described herein. Attached Figure Description

[0035] The invention will now be described by way of example with reference to the accompanying drawings, in which:

[0036] Figure 1 This is a side view of the transport refrigeration system (TRS) according to an embodiment;

[0037] Figure 2 schematically shown Figure 1 The transport refrigeration unit (TRU) of the TRS;

[0038] Figure 3This is a schematic flowchart illustrating the control logic and processing steps executed by the TRU's unit controller when operating in the first operating mode. This control logic and processing steps are used to determine the optimal condenser fan speed to maximize system efficiency.

[0039] Figure 4 This is a flowchart illustrating the simulation and modeling process for the first operating mode;

[0040] Figure 5 It schematically illustrates the control logic and processing steps for determining and implementing the optimal fan speed according to the first control strategy of the first operating mode;

[0041] Figure 6 This schematically illustrates a flowchart of the control logic and processing steps for determining and achieving the optimal fan speed based on a second control strategy according to a first operating mode; and

[0042] Figure 7 The flowchart schematically illustrates the control logic and processing steps executed by the TRU's unit controller when operating in a second operating mode, which are used to determine the condenser fan speed that maximizes system capacity. Detailed Implementation

[0043] Figure 1 This is a side view of a transport refrigeration system (TRS) 10 for a transport unit 25 (also referred to as a "refrigerated container") according to an embodiment. The transport unit 25 shown is a trailer-mounted transport unit. However, the embodiments described in this specification can be used with other types of transport units. For example, transport unit 25 can represent a container (e.g., a container on a flatbed truck, a multimodal container, etc.), a truck, a boxcar, or other similar types of transport units with an interior space where the environment can be controlled.

[0044] TRS 10 includes a refrigeration unit, hereinafter referred to as Transport Refrigeration Unit (TRU) 15. TRU 15 is disposed on the front wall 30 of transport unit 25 (but TRU 15 may be disposed elsewhere) and is configured to control one or more environmental conditions, such as, but not limited to, the temperature, humidity, and / or air quality of the interior space 50 of transport unit 25. In embodiments, interior space 50 may alternatively be referred to as regulated space 50, cargo space 50, environmentally controlled space 50, container 50, etc. Specifically, TRU 15 is configured to transfer heat from the air inside interior space 50 to the ambient air outside transport unit 25.

[0045] According to an embodiment, the interior space 50 may include one or more partitions or inner walls (not shown) for at least partially dividing the interior space 50 into multiple zones or compartments. It should be understood that the interior space 50 can be divided into any number of zones and can be divided in any structure suitable for cooling different zones. In some examples, each zone may have the same or different setpoint temperatures.

[0046] TRU 15 includes a programmable unit controller 35, which includes a single integrated control unit 40. It should be understood that in other embodiments, the unit controller 35 may include a distributed network (not shown) of TRU control elements. The unit controller 35 may include a processor, memory, a clock, and input / output (I / O) interfaces (not shown). The unit controller 35 may include fewer or additional components.

[0047] TRU 15 also includes a closed refrigeration circuit controlled by unit controller 35. Figure 2 (Ref. 12 in the accompanying drawings). The unit controller 35 controls the refrigeration circuit of the TRU 15 to achieve the desired state of the interior space 50 (e.g., temperature, humidity, air quality, etc.). In particular, the unit controller 35 can communicate wired or wirelessly with one or more sensors for measuring various operating conditions of the TRU 15 (such as chamber temperature, ambient temperature) and operating parameters of the TRU 15 (such as evaporator temperature, pressure, etc.) to allow the unit controller 35 to draw conclusions about what actions must be taken to achieve the desired state. For example, the unit controller 35 can compare the current state (e.g., chamber temperature and ambient temperature) with the target state (e.g., the chamber setpoint temperature) and adjust the current cooling capacity delivered by the TRU 15 accordingly. This can be accomplished by sending control signals to various control devices of the TRU 15, such as refrigeration throttle valves, dampers, etc., which control the movement of refrigerant through the refrigeration circuit.

[0048] TRU 15 also includes a power compartment (not shown) that houses an internal combustion engine (e.g., a diesel engine, etc.) that can provide power to drive the compressor and other components of the refrigeration circuit (e.g., a fan). The power compartment also houses an onboard electric motor that can replace the internal combustion engine to drive the compressor and other components when plugged into a backup power source (e.g., a three-phase power outlet).

[0049] The unit controller 35 itself is powered by a power module (not shown), which may include one or more power sources. The power source receives electrical energy from a generator (e.g., a belt-driven alternator, a direct-drive generator, etc.), which is mechanically driven by the prime mover of an internal combustion engine or an electric motor in the power compartment.

[0050] Figure 2 A schematic diagram showing more details Figure 1 The TRU 15. As shown in the figure, the TRU 15 includes not only the aforementioned refrigeration circuit 12 and unit controller 35, but also a condenser fan 29 and an evaporator fan 210.

[0051] The refrigeration circuit 12 includes a compressor 14, a discharge line 16, a condenser 18, a condenser outlet line 20, an expansion valve 22, an evaporator inlet line 24, an evaporator 26, a suction line 28, and an electronic expansion valve (ETV) 84 on the suction line 28. Refrigerant in various states flows through the refrigeration circuit 12 in a manner substantially as described in the background section.

[0052] This will be understood as follows: Figure 2 An example refrigeration circuit suitable for the present invention is shown, and the present invention is applicable to any refrigeration cycle, such as a refrigeration cycle with a heat exchanger provided on the suction line.

[0053] The unit controller 35 forms part of a wider controller circuit 100, which includes a compressor speed (Comp RPM) sensor 83, an evaporator inlet air temperature (EAIT) sensor 60, an evaporator outlet air temperature (EAOT) sensor 62, a condenser inlet air temperature (CAIT) sensor 64, an evaporator fan speed (Evap RPM) sensor 66, and a condenser fan speed (Cond RPM) sensor 68. The electronic throttle valve position (ETVVP) is set by the unit controller 35 and is therefore always known to the unit controller 35, requiring no sensing device. As a supplement to or alternative to the EAIT sensor 60, EAOT sensor 62, CAIT sensor 64, Evap RPM sensor 66, and Cond RPM sensor 68, a suction line pressure (PVIP) sensor and a condenser discharge pressure (PGOP) sensor (neither shown) may be provided. The controller circuit 100 may also include sensors for measuring the chamber temperature of the internal space to be regulated and the ambient temperature outside that space.

[0054] Each sensor can be wired (e.g., via a wiring harness) or wirelessly coupled to controller 35. In the particular arrangement shown, EAIT sensor 60 is coupled to controller 35 via EAIT line 70. EAOT sensor 62 is coupled to controller 35 via EAOT line 72. CAIT sensor 64 is coupled to controller 35 via CAIT line 74. Evap RPM sensor 66 is coupled to controller 35 via Evap RPM line 76. Cond RPM sensor 68 is coupled to controller 35 via Cond RPM line 78. Comp RPM sensor 83 is coupled to controller 35 via Comp RPM line 79. Additionally, controller 35 is electrically coupled to evaporator fan 210 via evaporator fan control line 80, electrically coupled to electronic throttle valve 84 via electronic throttle valve control line 81, and electrically coupled to condenser fan 29 via condenser fan control line 82.

[0055] As described above, in a conventional arrangement, the condenser fan speed, and therefore the condenser airflow, is typically fixed and proportional to the fixed speed of the prime mover. However, in contrast, the present invention relates to a variable-speed condenser fan 29, driven by a DC or AC fan motor (not shown), which is powered by the power module of TRU 15. For example, the AC fan motor can be equipped with a variable frequency drive to change and set the rotational speed independently of the prime mover. The DC fan motor can be an electronically commutated motor (ECM), a brushless DC motor (BLDC), etc., providing variable speed control.

[0056] The speed of the condenser fan 29 is controlled and set by the unit controller 35. For example, the speed of the motor is adjusted according to a pulse width modulation (PWM) signal or analog voltage signal provided from the TRU controller 35 to the controller on the fan motor, which receives the signal and controls the fan speed accordingly.

[0057] In the first operating mode, the fan speed (and therefore the condenser airflow) changes in real time during the operation of the TRU 15 based on the current cooling demand of the TRU 15. For example, the first operating mode is used when the TRU 15 is operating in cooling mode (i.e., during temperature pull-down operation) or while maintaining the setpoint temperature for both continuous (modulated) and cyclic sentinel operations. The first operating mode can also be implemented for both fresh-keeping and freezer temperatures.

[0058] In the first mode, when cooling demand decreases, the condenser fan speed will automatically decrease to operate at a lower rotational frequency, and / or when cooling demand increases, the condenser fan speed will automatically increase to operate at a higher rotational frequency. Thus, when the condenser fan 29 operates below full speed (e.g., under low cooling demand conditions), the power consumed by the condenser fan 29 will be reduced, while ensuring that the condenser fan 29 is driven at an appropriate speed to meet the system's current cooling demand. Reference will now be made to... Figures 3 to 6 The first operating mode is described further.

[0059] Figure 3 This is a schematic flowchart illustrating the control logic and processing steps executed by the unit controller 35 of TRU 15 when operating in the first operating mode.

[0060] Starting at step 31, the unit controller monitors a set of multiple operating parameters of the refrigeration loop 12 in real time. These parameters will be used at step 32 to determine the optimal condenser fan speed to maximize system efficiency. This set of multiple operating parameters indicates the current cooling demand. Specifically, the operating parameters in this set can be those that allow the unit controller 35 (and by which it uses them) to determine the current cooling demand and draw conclusions about what actions must be taken to achieve the desired state in the regulated chamber.

[0061] In one embodiment, the operating parameters monitored at step 31 include (e.g., composed of the following) Comp RPM, CAIT, EAIT, Evap RPM, and ETVVP (hereinafter referred to as the first set of operating parameters). In an alternative embodiment, the operating parameters monitored include (e.g., composed of the following) Comp RPM, PVIP, PGOP, and ETVVP (hereinafter referred to as the second set of operating parameters). Figure 2 The controller circuit 100 uses multiple sensors to monitor operating parameters.

[0062] The unit controller 35 can be configured to monitor all of the above operating parameters, such that the first and second sets of operating parameters can be used interchangeably to determine the optimal condenser fan speed at step 32. For example, the unit controller can (e.g., by the user) be set to use one set of parameters (e.g., the first set of operating parameters) by default for this determination, but if the unit controller 35 detects a fault in one of the sensors corresponding to the default set of operating parameters, it switches to using the other set of parameters for this determination.

[0063] At step 32, the unit controller 35 determines the optimal speed for operating the condenser fan 29 based on the current operating parameter values ​​to maximize system efficiency.

[0064] When utilizing the power generated by the internal combustion engine in the power compartment, the system efficiency of TRU 15 is:

[0065] System efficiency = Cooling capacity (watts) / Fuel consumption (liters per hour)

[0066] When using the onboard electric motor in the power compartment, the system efficiency of TRU 15 is:

[0067] System efficiency = Cooling capacity (watts) / Power consumption (watts)

[0068] In various embodiments, the determination at step 32 is based on a predetermined model of system efficiency, which is a function of a set of monitored operating parameters and the condenser fan speed. This predetermined model approximates the relationship between condenser fan speed, system efficiency (particularly cooling capacity and fuel / power consumption), and the set of operating parameters. For this purpose, a series of simulations of TRU 15 are performed beforehand by a computer processor to model the relationship between condenser fan speed and system efficiency for different values ​​of the set or more sets of operating parameters to be monitored at step 31. The unit controller 35 can then... Figure 3 In step 32 of the method, the predetermined model is used to determine a fan speed such that, for the current values ​​of the set of operating parameters monitored in step 31, the fan speed will produce a cooling capacity value and a fuel or power consumption value that yields the maximum system efficiency value according to the above equation. As will be described in further detail below, various different strategies can be used to determine the optimal fan speed using this predetermined model.

[0069] After the unit controller 35 has determined the optimal condenser fan speed at step 32, the unit controller 35 (at step 33) sets the condenser fan to operate at a speed selected based on the optimal condenser fan speed. In various embodiments, the condenser fan operates at the optimal fan speed or as close as possible to the optimal fan speed. In either case, to set the speed of the condenser fan 29, the unit controller 35 issues a speed command (PWM signal) along the condenser fan control pipeline 82.

[0070] It will be understood that during the operation of TRU 15, it can be repeated continuously in real time. Figure 3 Steps 31 to 33 are to ensure optimal fan speed throughout its operation.

[0071] Figure 4 This shows the above regarding Figure 3 Step 32 describes the flowchart of the simulation and modeling process.

[0072] The process begins by testing the actual operation of each component of the TRU 15 (such as the refrigeration circuit assembly, condenser, and evaporator fan) to determine their respective operational characteristics. Figure 4 Step 41). The operating characteristics of each component of TRU 25 can be mathematically expressed in the form of a characteristic curve, which defines the relationship between the component's performance and the various operating variables.

[0073] Then, at step 42, the characteristic curves of the individual components are combined to generate a mathematical model of TRU 15 (using a computer processor), namely the so-called "steady-state system model". The steady-state system model approximates the performance of the system because it takes as input the corresponding arrangement of the operating conditions and operating parameter values ​​(such as CompRPM, CAIT, EAIT, and superheat settings) of the key components in TRU 15, and outputs the cooling capacity value (i.e., watts), the fuel consumption value (liters per unit time) when the model simulates an internal combustion engine power system, and / or the power consumption value (watts) when the model simulates an electric system.

[0074] At step 43, if necessary, the accuracy of the steady-state system model can be verified and refined by comparing the inputs and outputs of the test simulation of the computer-generated model with the physical test data (“system-level test data”) obtained by operating the modeled physical TRU 15.

[0075] At step 44, a series of simulation cases are designed for system performance modeling across the entire system's operating graph. Specifically, multiple corresponding permutations of operating conditions (e.g., ambient temperature) and operating parameters for the components in TRU 15 are determined, such that they can be used as input to the steady-state system model to simulate the performance of TRU 15 across the entire system operating graph at step 45. Simulations can be performed using a wide range of compressor speeds, ambient temperatures (e.g., between -30 and 55°C), evaporator inlet temperatures (e.g., between -35 and 55°C), varying evaporator fan speeds, and / or electronic throttle valve positions, etc.

[0076] After running the simulation case using the steady-state system model, the process proceeds to step 46, where statistical analysis is performed on the obtained simulation data (i.e., multiple sets of input data and corresponding output data (cooling capacity and fuel or power consumption)) to determine the system efficiency model, namely, the condenser fan speed, system efficiency, and the above reference... Figure 3 In step 32 of the method, a relationship model between a set of operating parameters is determined.

[0077] The predetermined model can be considered as a meta-model representing the input-output relationship of the steady-state model. In this embodiment, the meta-model receives the condenser fan speed and the values ​​of a corresponding set of operating parameters from a plurality of sets of operating parameters to be monitored by the unit controller 35 according to the invention as input. In this respect, regarding the above... Figure 3 Step 31 of the method describes determining at least one meta-model for each of the first and second sets of operating parameters. In this embodiment, the output of the meta-model is system cooling capacity, fuel consumption and / or electrical power consumption, and optionally, system efficiency. In this embodiment, for each set of operating parameters, there is one meta-model for system cooling capacity and engine power consumption, and another meta-model for system cooling capacity and electrical power consumption.

[0078] In step 46, various statistical analysis techniques known in the art can be used to derive the meta-model. However, in various embodiments, methods based on neural networks, kriging, or regression models are selected and used for this purpose.

[0079] After generating one or more meta-models in step 46, these meta-models are used to determine the optimal condenser fan speed, which is then used to control the operation of the condenser fan. The unit controller will determine and use the optimal condenser fan speed to control the operation of the condenser fan according to either a first control strategy or a second control strategy, both of which are available to the controller (e.g., selectable by the user), as follows: Figure 4 Steps 47 and 48 are shown.

[0080] It will be understood here that, according to the present invention, the aforementioned steps 41 to 46 for simulating and modeling the efficiency of the TRU 15, particularly the system efficiency, will be performed prior to the operation of the refrigeration system. That is, the meta-model is predetermined and created offline in the initial stage prior to the operation of the TRU 15 (e.g., by a computer processor separate from the unit controller 35 or the wider TRU 15) so that it can be used later to determine the optimal fan speed.

[0081] Figure 5 It is shown schematically in more detail. Figure 3 The flowchart of the control logic and processing steps, especially when the unit controller operates according to the first control strategy to determine and use the optimal fan speed.

[0082] As referenced above Figure 3 As described in step 31, the unit controller begins by monitoring a set of operating parameters of the refrigeration circuit 12 in real time at step 51.

[0083] At step 52, the optimal condenser fan speed is determined by inputting the current values ​​of a set of monitored operating parameters into a regression model for the optimal condenser fan speed, wherein the regression model has been pre-determined for the set of operating parameters in question. The regression model is expressed as a function of the monitored set of operating parameters and outputs the optimal condenser fan speed based on a predetermined relationship between the set of operating parameters (or their possible values) and the optimal condenser fan speed.

[0084] This pre-arranged relationship is already based on... Figure 4 The metamodel determined in step 46 is predetermined. This is done by performing regression analysis using the metamodel to examine the relationship between the optimal fan speed and a set of operating parameters to be monitored. For example, the metamodel corresponding to the set of operating parameters to be monitored in step 51 is used to determine the fan speed that maximizes system efficiency for each permutation of the values ​​of that set of operating parameters.

[0085] Any suitable regression analysis technique can be used for this purpose. However, in this embodiment, for a given permutation of operating parameter values, these operating parameter values ​​are input into a meta-model along with a given (e.g., selected) condenser fan speed value. The meta-model then outputs the corresponding cooling capacity and fuel or power consumption. For example, this process is repeated over the entire range of possible condenser fan speeds such that the system efficiency achievable within that fan speed range (i.e., the ratio of cooling capacity to fuel or power consumption) is known. The optimal fan speed is then determined for the permutation of operating parameter values ​​in question, and is identified as the speed that achieves maximum system efficiency. The optimal fan speed is then determined in the same manner for multiple corresponding permutations of operating parameter values, and a curve function is fitted to multiple optimal fan speeds for the corresponding permutations of operating parameter values, where the curve function will be used as a regression model.

[0086] In an alternative embodiment, instead of a regression model, a predetermined relationship between a set of operating parameters and the optimal condenser fan speed can be represented as a lookup table. Therefore, a lookup table stored in memory can exist, having multiple entries, such as one entry for a corresponding arrangement of operating parameter values. Each entry in the table includes data indicating the optimal fan speed (determined by regression analysis) for the arrangement of operating parameter values ​​corresponding to that entry.

[0087] It will be understood that more than one regression model or lookup table can be generated for the system, that is, one regression model or lookup table can be generated for each different set of operating parameters to be monitored by the unit controller 35. Specifically, the first regression model or lookup table can take the current values ​​of Comp RPM, CAIT, EAIT, Evap RPM, and ETVVP as input and output the optimal condenser fan speed for these operating parameters to provide maximum system efficiency. The second regression model or lookup table can take the current values ​​of Comprpm, PVIP, PGOP, and ETVVP as input and output the optimal condenser fan speed for these operating parameters to provide maximum system efficiency. When the controller is configured to interchangeably set the condenser fan speed based on the current values ​​of the first set of operating parameters and the current values ​​of the second set of operating parameters, the controller can utilize the regression model or lookup table corresponding to the set of operating parameters in question.

[0088] like Figure 5 The dashed line in step 53 indicates that this occurs before and during the operation of TRU 15. Figure 4 After the meta-model is determined at step 46, one or more regression models and / or lookup tables are generated. However, the regression models and / or lookup tables are stored in the memory of the unit controller 35 for subsequent use at step 52 to determine the optimal fan speed for the current operating parameters of the system in real time.

[0089] After determining the optimal fan speed at step 52, the unit controller 35 will operate the condenser fan 29 at a speed as close as possible to the optimal speed. In this regard, it will be understood that, in practice, the condenser fan may only operate within a subrange of condenser fan speeds (through which the meta-model is created). Therefore, in various embodiments, the unit controller will determine whether the optimal fan speed determined at step 52 falls within a predetermined range of possible fan speeds at which the condenser fan can operate, and based on this determination, operate the condenser fan at an appropriate speed.

[0090] When the control strategy outputs an optimal condenser fan speed, the controller ensures that the condenser fan operates only between its predefined minimum and maximum fan speeds. Specifically, at step 54, the unit controller 35 determines whether the determined optimal condenser fan speed is greater than the minimum speed at which the condenser fan can operate. If the optimal speed is equal to or less than the minimum fan speed, the unit controller 35 proceeds to step 55, where the condenser fan operates at the minimum fan speed.

[0091] However, if the optimal condenser fan speed is determined to be greater than the minimum fan speed, the unit controller 35 will continue to determine at step 56 whether the optimal condenser fan speed is less than the maximum speed at which the condenser fan can operate. If the optimal speed is equal to or greater than the maximum fan speed, the unit controller 35 will proceed to step 57, in which the condenser fan operates at the maximum fan speed. If the optimal condenser fan speed is less than the maximum fan speed, the unit controller 35 will proceed to step 58, in which the condenser fan operates at the determined optimal condenser fan speed.

[0092] In each of the above cases, the unit controller 35 will issue appropriate speed commands along the condenser fan control line (e.g., wiring harness) to operate the condenser fan.

[0093] Figure 6 It is shown schematically in more detail. Figure 3 The flowchart of the control logic and processing steps, especially when the unit controller operates according to the second control strategy to determine and use the optimal fan speed.

[0094] exist Figure 6 Many of the control logic and processing steps executed in the embodiments are related to... Figure 5 The control logic and processing steps of the described embodiments correspond to each other (and for this reason, in Figure 5 and Figure 6 (The same reference numerals are used to label the same processing steps in the accompanying drawings). For the sake of brevity, the details of these steps will not be repeated here.

[0095] Figure 6 Control strategies and Figure 5 The difference in the control strategy lies in the fact that, unlike the determination and use of regression models or lookup tables as described above, the meta-model corresponding to the set of operating parameters monitored in step 51 (i.e., the meta-model corresponding to the first set of operating parameters or the meta-model corresponding to the second set of operating parameters or both) itself is in the initialization step (i.e. Figure 6 The steps 61) are stored in the memory of the unit controller 35 for later use in real time to determine the optimal condenser fan speed during TRU 15 operation.

[0096] Specifically, at step 63, a meta-model is used to determine the fan speed that maximizes system efficiency for the current values ​​of the monitored set of operating parameters. To this end, the unit controller is configured to use the meta-model to execute an optimization algorithm to determine and select the condenser fan speed (from a range of possible fan speeds) that produces the highest system efficiency. It will be understood that when the controller is configured to interchangeably set the condenser fan speed based on the current values ​​of a first set of operating parameters and a second set of operating parameters, the controller can use a meta-model corresponding to either the first or second set of operating parameters. When using one set of operating parameters from multiple sets by default, the controller can execute an optimization algorithm using a meta-model corresponding to the default set of operating parameters, and if the controller detects a fault in one or more sensors used to monitor the default set of operating parameters, it switches to using a meta-model corresponding to the other set of operating parameters to execute the optimization algorithm.

[0097] For this purpose, any suitable optimization algorithm can be used. However, in some cases, this is accomplished by using an optimization algorithm that takes the current operating parameter values ​​and a given (e.g., selected) condenser fan speed as input to the meta-model and receives from the meta-model the cooling capacity, the corresponding fuel or power consumption (depending on the meta-model used), and, in some cases, the system efficiency as output. The optimization algorithm then repeats this step for each condenser fan speed across the entire condenser fan speed range. Based on the outputs obtained from the meta-model across the entire condenser fan speed range, the unit controller determines the fan speed at which the system efficiency reaches its maximum value. The unit controller then applies the above-mentioned... Figure 5 Continue in the manner described in steps 54 to 58 Figure 6 Steps 54 to 58 are used to issue appropriate speed commands to the condenser fan along the condenser fan control line.

[0098] The above text is for reference only. Figures 3 to 6 The present invention improves system efficiency, thereby improving fuel or power economy, compared to previously considered arrangements where the condenser fan operates at a fixed speed depending on the prime mover's rotational speed. It will be understood that the degree of fuel or power savings achieved by setting the condenser fan speed according to a first operating mode will vary with different enclosure and environmental conditions. However, at least under mainstream customer operating conditions (enclosure / ambient temperature: -25 / 8°C and -25 / 19°C), simulations show that up to 7% fuel savings can be achieved during pullback.

[0099] Although the invention has been described above with respect to a first operating mode in which the fan speed is set to increase system efficiency, in various embodiments, the unit controller 35 is also configured to operate according to a second operating mode in which the fan speed is set to maximize cooling capacity without regard to system efficiency.

[0100] It will be understood that the unit controller 35 can be configured to alternate between a first operating mode and a second operating mode. That is, in various embodiments, the unit controller 35 is configured to switch between a first operating mode that controls the fan speed to maximize efficiency and a second operating mode that controls the fan speed to maximize cooling capacity in response to receiving user input. This dual functionality provides a more versatile and complete system compared to a system configured to operate according to only one of these operating modes.

[0101] For example, the second operating mode can be initiated by a user-operable mechanical switch located on TRU 15, or by the user selecting the operating mode on the computer (e.g., input / output interface) of the unit controller 35.

[0102] Figure 7 This is a schematic flowchart illustrating the control logic and processing steps executed by the unit controller of TRU 15 when operating in the second operating mode.

[0103] The second operating mode is Figure 7 Beginning at step 71, the unit controller 35 determines, if any, excess power capacity available from a power source (e.g., a generator and an active rectifier, wherein the generator is driven by the prime mover of the power compartment) to enable the condenser fan to operate at the highest possible speed using that excess power capacity. This can be advantageously used to maximize cooling capacity and achieve faster pull-down and recovery times.

[0104] Therefore, at step 71, the unit controller 35 checks the maximum power capacity of the power supply and determines the current power drawn from the power supply based on the current generator speed. Based on the current power consumption and the total power capacity of the power supply, the unit controller 35 determines the excess power capacity (in addition to the current power consumption) that the condenser fan can use while maintaining the current speed of the prime mover (and thus the current speed of the compressor).

[0105] At step 73, the unit controller 35 determines the maximum speed at which the condenser fan can operate when utilizing excess power capacity from the power supply. In this embodiment, this may be a determination of the maximum average voltage and current that can be supplied to the motor driving the condenser fan 29.

[0106] At step 75, after the maximum fan speed has been determined, the unit controller sends a command or other signal along the condenser fan control line 82 to cause the condenser fan 29 to operate at the maximum speed determined at step 73.

[0107] It will be understood that during the operation of TRU 15, it can be repeated continuously in real time. Figure 7 Steps 71 to 75 ensure that the maximum possible fan speed is achieved at any given time. Furthermore, by utilizing only the excess available power beyond the current power consumption of the power supply to drive the fan, unit controller 35 ensures that the maximum fan speed can be achieved without impairing the operation of any individual component of the system. That is, unit controller 35 will ensure that the power drawn by condenser fan 29 does not exceed the power currently available from the power supply.

[0108] In view of the above, it can be seen that the present invention provides a universal refrigeration system that can be advantageously used to maximize system efficiency or refrigeration capacity. This is particularly advantageous compared to previously considered arrangements, in which such a level of control and optimization was not provided.

[0109] The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. Unless otherwise expressly stated, the terms "a," "an," and "the" also include the plural forms. When used in this specification, the terms "comprising" and / or "including" indicate the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other functions, integers, steps, operations, elements, and / or components.

[0110] Regarding the foregoing description, it should be understood that changes in detail can be made, particularly in terms of the construction materials used and the shape, size, and arrangement of parts, without departing from the scope of the invention. That is, the invention is not limited to the embodiments described above; any feature may be used alone or in combination with any other feature, except in mutually exclusive cases, and the invention extends to and includes all combinations and sub-combinations of one or more features described herein.

[0111] The term "embodiment" as used in this specification may, but does not necessarily, refer to the same embodiment. This specification and the described embodiments are merely examples. Other and further embodiments may be devised without departing from the basic scope of the invention, the true scope of which is indicated by the appended claims.

Claims

1. A refrigeration system (10), comprising: The refrigeration circuit (12) includes at least a compressor (14), a condenser (18), an expansion valve (22), and an evaporator (26). Variable speed condenser fan (29); and The controller (35) is configured in the first operating mode: A set of operating parameters of the refrigeration circuit (12) that monitors and indicates the refrigeration demand of the refrigeration system (10); An optimization algorithm is executed using a predetermined model of system efficiency to determine (32) the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values, wherein the predetermined model is a function of the set of operating parameters and the condenser fan speed; and The speed of the condenser fan (29) is set based on the condenser fan speed determined (32) when the system efficiency will reach its maximum value for the current operating parameter values. The optimization algorithm includes the following: For each condenser fan speed in a predefined set of condenser fan speeds: The condenser fan speed and the current operating parameter values ​​are input into a predetermined model of the system efficiency; and Receive cooling capacity and fuel or power consumption values ​​as output data from a predetermined model of system efficiency; and Based on the output data for the set of predefined condenser fan speeds, a predefined condenser fan speed is determined to maximize the system efficiency for the corresponding cooling capacity and fuel or power consumption values.

2. The refrigeration system (10) according to claim 1, wherein: The refrigeration system (10) includes a power supply for at least powering the controller and the condenser fan; and The controller (35) is configured in a second operating mode: Based on the current power consumption and the predefined maximum power capacity of the power source, determine the excess power capacity that can be obtained from the power source. Determine the maximum speed at which the condenser fan can operate when utilizing the excess power capacity from the power source; as well as The condenser fan (29) is set to operate at the determined maximum speed.

3. The refrigeration system according to claim 1, wherein the controller is configured to: Monitor the first set of operating parameters and different second sets of operating parameters, each set indicating the cooling demand; and The condenser fan speed can be set interchangeably based on the current values ​​of the first set of operating parameters and the current values ​​of the second set of operating parameters.

4. The refrigeration system according to claim 3, wherein the controller is configured to: In the first operating mode, the condenser fan speed is set by default based on the current value of the first set of operating parameters, and if the controller detects a fault in one or more sensors used to monitor the first set of operating parameters, the condenser fan speed is set based on the current value of the second set of operating parameters.

5. The refrigeration system according to any one of claims 1 to 4, wherein, The set of operating parameters includes: One or more of the following: compressor speed, condenser inlet temperature, evaporator inlet temperature, evaporator fan speed, and throttle valve position; or One or more of the following: compressor speed, compressor suction pressure, condenser discharge pressure, and throttle valve position.

6. A method of operating a variable speed condenser fan (29) of a refrigeration system (10), the refrigeration system comprising a refrigeration circuit (12), the refrigeration circuit comprising at least a compressor (14), a condenser (18), an expansion valve (22) and an evaporator (26). The method includes: When operating in the first operating mode, the controller (35) performs the following operations: A set of operating parameters of the refrigeration circuit that monitors and indicates the current refrigeration demand of the refrigeration system (10); An optimization algorithm is executed using a predetermined model of system efficiency to determine (32) the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values, wherein the predetermined model is a function of the set of operating parameters and the condenser fan speed; and The speed of the condenser fan (29) is set based on the condenser fan speed determined (32) when the system efficiency will reach its maximum value for the current operating parameter values. The optimization algorithm is executed to determine the condenser fan speed at which the system efficiency will reach its maximum value for the current operating parameter values, including: For each condenser fan speed in a predefined set of condenser fan speeds: The condenser fan speed and the current operating parameter values ​​are input into a predetermined model of the system efficiency; and Receive cooling capacity values ​​and corresponding fuel or power consumption values ​​as output data from a predetermined model of system efficiency; and Based on the output data for the set of predefined condenser fan speeds, a predefined condenser fan speed is determined to maximize the system efficiency for the corresponding cooling capacity and fuel or power consumption values.

7. The method according to claim 6, wherein, The set of operating parameters includes: One or more of the following: compressor speed, condenser inlet temperature, evaporator inlet temperature, evaporator fan speed, and throttle valve position; or One or more of the following: compressor speed, compressor suction pressure, condenser discharge pressure, and throttle valve position.

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