Chiller suction flow limiting with input power or motor current control

Abstract

To provide a chiller for effectively managing compressor operation to reduce or eliminate a liquid droplet flow from an evaporator to a compressor.SOLUTION: A chiller 22 includes an evaporator 46, a compressor 48 including a prime mover, a first pressure sensor 86 that detects a first pressure in the evaporator 46, a second pressure sensor 88 that detects a second pressure in a condenser 50, and a controller 100. The controller 100 determines a predicted energy level of the compressor 48 based on the first pressure and the second pressure, the predicted energy level associated with a liquid droplet flow into the compressor 48, compares the predicted energy level to an operating energy level, and modifies the at least one of the input power and the input current to the prime mover based on the comparison satisfying a modification condition.SELECTED DRAWING: Figure 2

Description

[Background technology]

[0001] Refrigerants can transfer heat between fluids and may be utilized in a variety of applications, such as power generation in heating, ventilation, and air conditioning (HVAC) systems, heat pumps, or organic Rankine cycles (ORCs). The refrigerant may be transported in a refrigerant piping system that includes pipes, fittings, valves, etc. The refrigerant piping system transports the refrigerant between various vessels and equipment in the HVAC system, such as compressors, turbines, pumps, evaporators, and condensers. The refrigerant may undergo one or more phase changes in the refrigerant piping system, such that both liquid and vapor refrigerants may exist in the HVAC system. Summary of the Invention [Means for solving the problem]

[0002] One embodiment of the present disclosure is a chiller. The chiller includes an evaporator that receives a first flow of refrigerant, transfers heat to the first flow of refrigerant, and outputs a second flow of refrigerant. The chiller includes a compressor that receives the second flow of refrigerant via piping between the evaporator and the compressor, the compressor including a prime mover that performs work on the second flow of refrigerant based on at least one of an input power to the prime mover and an input current to the prime mover. The chiller includes a first pressure sensor that detects a first pressure of the refrigerant at the evaporator. The chiller includes a second pressure sensor that detects a second pressure of the refrigerant at a condenser of the chiller. The chiller includes a controller that determines a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being associated with a flow of droplets in the second flow of refrigerant received by the compressor, compares the predicted energy level to an operating state energy level of the compressor, and modifies at least one of the input power and the input current to the prime mover based on the comparison satisfying a modification condition.

[0003] Another embodiment of the present disclosure is a method of chiller inlet flow restriction. The method includes receiving, by a controller, a first pressure from an evaporator pressure sensor coupled to an evaporator. The method includes receiving, by the controller, a second pressure from a condenser pressure sensor coupled to a condenser. The method includes determining, by the controller, a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being associated with a flow of droplets from the evaporator to the condenser. The method includes comparing, by the controller, the predicted energy level to an operating state energy level of the compressor. The method includes modifying at least one of an input power and an input current to a prime mover of the compressor based on the comparison satisfying a modification condition.

[0004] Yet another embodiment of the present disclosure is a chiller controller comprising one or more processors and a memory device storing computer readable instructions that, when executed by the one or more processors, cause the one or more processors to: receive, at a condition detector, a first pressure from an evaporator pressure sensor coupled to an evaporator, receive, at the condition detector, a second pressure from a condenser pressure sensor coupled to a condenser, determine, at an energy predictor, a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being associated with a flow of droplets from the evaporator to the condenser, compare, at a compressor controller, the predicted energy level to an energy level during an operating condition, and modify, at least one of an input power and an input current to a prime mover of the compressor based on the comparison satisfying a modification condition.

[0005] Those skilled in the art will appreciate that this summary is illustrative only and is not intended to be in any way limiting. It will be understood that other aspects, inventive features, and advantages of the apparatus and / or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and when read in conjunction with the accompanying drawings. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view of a building serviced by a heating, ventilation, and air conditioning (HVAC) system in accordance with an illustrative embodiment. [Diagram 2] 2 is a block diagram illustrating a portion of the HVAC system of FIG. 1 in greater detail, showing a refrigeration circuit configured to circulate a refrigerant between an evaporator and a condenser, according to an exemplary embodiment. [Diagram 3] FIG. 3 is a block diagram of a controller for the refrigeration circuit of FIG. 2 according to an exemplary embodiment. [Figure 4] 1 is a flow diagram of a method for chiller inlet flow limitation by input power or motor current control in accordance with an illustrative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] The present disclosure generally relates to the field of refrigeration systems. More specifically, the present disclosure relates to chiller suction flow restriction by input power or motor current control. A refrigeration system may include a chiller, which may include an evaporator, a condenser, a compressor, and piping connecting these and various other components. The evaporator evaporates a refrigerant to provide net cooling to a process fluid, such as water, flowing through the piping. It may be desirable for the evaporator to generate dry, saturated vapor from the refrigerant and for the compressor to receive this dry, saturated vapor based on the suction generated by the compressor. However, in some cases, the refrigerant output by the evaporator contains liquid droplets that are lifted by the higher velocity vapor flow based on the suction from the compressor. Additionally, size, weight, power, and cost considerations may make it desirable to reduce the size of the evaporator to meet the minimum design capacity needs of the refrigeration system. However, the compressor may provide a higher capacity and suction flow rate due to a reduced lift or differential pressure across the compressor due to the operating conditions of the chiller, which may increase the gas velocity at the evaporator and carry liquid droplets into the compressor. These effects can reduce the efficiency of the chiller and can cause damage to the compressor's mechanical components.

[0008] Such considerations are addressed by the present solution by implementing chiller inlet flow limitation via input power or motor current control to effectively manage compressor operation to reduce or eliminate droplet flow from the evaporator to the compressor. For example, the present solution system and method can predict a power or current level corresponding to an evaporator design speed limit at which droplet flow to the compressor may be expected to occur, and use a controller to limit further power or current increases to prevent droplet flow (e.g., liquid flow carryover) to the compressor. In some embodiments, the chiller includes an evaporator that receives a first flow of refrigerant, transfers heat to the first flow of refrigerant, and outputs a second flow of refrigerant. The chiller includes a compressor that receives the second flow of refrigerant via piping between the evaporator and the compressor, the compressor including a prime mover that performs work on the second flow of refrigerant based on at least one of the input power to the prime mover and the input current to the prime mover. The chiller includes a first pressure sensor that detects a first pressure of the refrigerant at the evaporator. The chiller includes a second pressure sensor that detects a second pressure of the refrigerant at a condenser of the chiller. The chiller includes a controller that determines a predicted energy level of operation of the compressor based on the first pressure and the second pressure, compares the predicted energy level to an operating state energy level associated with a flow of droplets in the second flow of refrigerant received by the compressor, and modifies at least one of the input power and input current to the prime mover based on the comparison satisfying a modification condition, such that if the predicted energy level is too high (e.g., greater than the operating state energy level), the controller limits the power or current to the prime mover as necessary to reduce or prevent a risk of droplets flowing into the compressor that would otherwise occur if a design speed limit of the evaporator is exceeded. can be eliminated.

[0009] HVAC systems FIG. 1 shows a perspective view of a building 10. The building 10 is served by a heating, ventilation and air conditioning system (HVAC) system 20. The HVAC system 20 can include a chiller 22, a boiler 24, a rooftop cooling unit 26, and a number of air handling units (AHUs) 36. The HVAC system 20 uses a fluid circulation system to provide heating and / or cooling to the building 10. The circulating fluid can be cooled by the chiller 22 or heated by the boiler 24, depending on whether cooling or heating is required. The boiler 24 can add heat to the circulating fluid by burning a combustible material (e.g., natural gas). The chiller 22 can place the circulating fluid in a heat exchange relationship with another fluid (e.g., a refrigerant) in a heat exchanger (e.g., an evaporator). The refrigerant removes heat from the circulating fluid during the evaporation process, thereby cooling the circulating fluid.

[0010] The circulating fluid from the chiller 22 or boiler 24 may be transported to the AHU 36 via ducting 32. The AHU 36 may place the circulating fluid in a heat exchange relationship with an airflow passing through the AHU 36. For example, the airflow may be passed through ducting in a fan coil unit or other air conditioning terminal unit through which the circulating fluid flows. The AHU 36 may transfer heat between the airflow and the circulating fluid to provide heating or cooling for the airflow. The heated or cooled air may be delivered to the building 10 via an air distribution system including an air supply duct 38 and returned to the AHU 36 via an air return duct 40. The HVAC system 20 may include a separate AHU 36 for each floor of the building 10. In other embodiments, a single AHU (e.g., a rooftop AHU) may supply air for multiple floors or zones. The circulating fluid from the AHU 36 may return to the chiller 22 or boiler 24 via ducting 34.

[0011] The refrigerant in the chiller 22 may be evaporated as it absorbs heat from the circulating fluid. The vapor refrigerant may be fed to a compressor in the chiller 22 where the temperature and pressure of the refrigerant is increased (e.g., using a rotating impeller, screw compressor, scroll compressor, reciprocating compressor, centrifugal compressor, etc.). The compressed refrigerant may be discharged to a condenser in the chiller 22. In some embodiments, water (or another fluid) flows through tubes in the condenser of the chiller 22 to absorb heat from the refrigerant vapor, thereby condensing the refrigerant. The water flowing through the tubes in the condenser may be pumped from the chiller 22 to the cooling unit 26 via piping 28. The cooling unit 26 may use fan-driven cooling or fan-driven evaporation to remove heat from the water. The cooling water from the cooling unit 26 may be pumped back to the chiller 22 via piping 30, and the cycle repeats.

[0012] FIG. 2 illustrates a block diagram of a portion of the HVAC system 20 according to an exemplary embodiment. The chiller 22 may include a refrigeration circuit 42 and a controller 100. The refrigeration circuit 42 may include an evaporator 46, a compressor 48, a condenser 50, and an expansion valve 52. The compressor 48 may be configured to circulate a refrigerant through the refrigeration circuit 42. The compressor 48 may be operated by the controller 100. The compressor 48 may compress the refrigerant to a high pressure and high temperature state and discharge the compressed refrigerant to a compressor discharge line 54 that connects an outlet of the compressor 48 to an inlet of the condenser 50. The compressor 48 may be or include a screw compressor or a semi-hermetic screw compressor, or the compressor 48 is, for example, a hermetic or open screw compressor. The compressor 48 may also be or include a scroll compressor, a reciprocating compressor, a centrifugal compressor, or yet another type of compressor.

[0013] The condenser 50 may receive compressed refrigerant from a compressor discharge line 54. The condenser 50 may receive a separate heat exchange fluid (e.g., water, a water-glycol mixture) from a refrigeration circuit 56. , another refrigerant, etc. The condenser 50 may be configured to transfer heat from the compressed refrigerant to a heat exchange fluid, thereby condensing the compressed refrigerant from a gas refrigerant to a liquid or mixed fluid state. The cooling circuit 56 may include a heat recovery circuit configured to use heat absorbed from the refrigerant for heating applications. The cooling circuit 56 may include a pump 58 for circulating the heat exchange fluid between the condenser 50 and the cooling unit 26. The cooling unit 26 may include a cooling coil 60 configured to facilitate heat transfer between the heat exchange fluid and another fluid (e.g., air) flowing through the cooling unit 26. The cooling unit 26 may include a cooling tower. The heat exchange fluid may give up heat within the cooling unit 26 and return to the condenser 50 via piping 30.

[0014] The refrigeration circuit 42 may include a line 62 connecting an outlet of the condenser 50 to an inlet of an expansion device 52. The expansion device 52 may expand the refrigerant in the refrigeration circuit 42 to a low temperature, low pressure condition. The expansion device 52 may be a fixed position device or a variable position device (e.g., a valve). The expansion device 52 may be actuated manually or automatically (e.g., by the controller 100 via a valve actuator) to regulate the expansion of the refrigerant passing therethrough. The expansion device 52 may output the expanded refrigerant to a line 64 connecting an outlet of the expansion device 52 to an inlet of the evaporator 46.

[0015] The evaporator 46 may receive the expanded refrigerant from line 64. The evaporator 46 may also receive a separate chilled fluid (e.g., water, a water-glycol mixture, another refrigerant, etc.) from a chilled fluid circuit 66. The evaporator 46 may be configured to transfer heat from the chilled fluid to the expanded refrigerant in the refrigeration circuit 42, thereby cooling the chilled fluid and evaporating the refrigerant. The chilled fluid circuit 66 may include a pump 68 for circulating the chilled fluid between the evaporator 46 and the AHU 36. The AHU 36 may include a cooling coil 70 configured to facilitate heat transfer between the chilled fluid and another fluid (e.g., air) flowing through the AHU 36. The chilled fluid may absorb heat in the AHU 36 and return to the evaporator 46 via piping 34. The evaporator 46 may output the heated refrigerant to a compressor suction line 72 that connects an outlet of the evaporator 46 to an inlet of the compressor 48.

[0016] The chilled fluid circuit 66 may include a chilled fluid temperature sensor 74 disposed along the piping 32. The chilled fluid temperature sensor 74 may be configured to detect a temperature Tcf (e.g., an exiting chilled liquid temperature, etc.) of the chilled fluid flowing in the piping 32 between the evaporator 46 and the AHU 36. The refrigeration circuit 42 may include a suction temperature sensor 76 disposed along the compressor suction line 72. The suction temperature sensor 76 may be configured to detect a temperature Tsuc of the refrigerant flowing in the compressor suction line 72 between the evaporator 46 and the compressor 48 (i.e., the temperature of the refrigerant entering the compressor 48). The refrigeration circuit 42 may include a suction pressure sensor 78 disposed along the compressor suction line 72. The suction pressure sensor 78 may be configured to detect a pressure Psuc of the refrigerant flowing in the compressor suction line 72 between the evaporator 46 and the compressor 48 (i.e., the pressure of the refrigerant entering the compressor 48). The refrigeration circuit 42 may include a discharge temperature sensor 80 disposed along the compressor discharge line 54. The discharge temperature sensor 80 may be configured to detect the temperature Tdis of the refrigerant flowing in the compressor discharge line 54 between the compressor 48 and the condenser 50 (i.e., the temperature of the refrigerant leaving the compressor 48). The refrigeration circuit 42 may include a discharge pressure sensor 82 disposed along the compressor discharge line 54. The discharge pressure sensor 82 may be configured to detect the pressure Pdis of the refrigerant flowing in the compressor discharge line 54 between the compressor 48 and the condenser 50 (i.e., the pressure of the refrigerant leaving the compressor 48).

[0017] The refrigeration circuit 42 may include an evaporator pressure sensor 86 for sensing the pressure Pevap of the refrigerant flowing through the evaporator 46, and a condenser pressure sensor 88 for sensing the pressure Pcond of the refrigerant flowing through the condenser 50. The sensors 86, 88 may be similar to the sensors 78, 82. , sensors 78, 82 may be used to perform the functions of sensors 86, 88 relating to measuring pressures associated with the evaporator 46 and the compressor 48, respectively, as described further herein. The sensors 86, 88 may be positioned at various points within or adjacent the evaporator 46 and the condenser 50, respectively, to detect the respective pressures Pevap and Pcond.

[0018] The compressor 48 includes a prime mover 84 (e.g., a motor). The prime mover 84 may be a fixed speed drive or a variable speed drive. The controller 100 may send control signals to the prime mover 84 to control the operation of the prime mover 84, such as to control the rotational speed, flow rate, or other operating parameters of the compressor 48. The controller 100 may control the operation of the prime mover 84 based on at least one of a power or a current corresponding to the operation of the compressor 48. Depending on the operating conditions of the refrigeration circuit 42, droplets of refrigerant may flow from the evaporator 46 to the compressor 48. The controller 100 may control the operation of the prime mover 84 to reduce or eliminate the flow of droplets from the evaporator 46 to the compressor 48.

[0019] Chiller intake flow limiting by input power or motor current control 3 illustrates a block diagram of a refrigeration system 150 with a controller 100 according to an exemplary embodiment. The controller 100 can control the operation of the compressor 48, such as to control the operation of the compressor 48 based on at least one of input power or motor current control. Power and current, such as input power, input current, motor power, motor current, etc., can include power or current to the refrigeration system 150 (e.g., to a chiller), power or current to a motor controller of the refrigeration system 150, power or current to a drive (e.g., a variable speed drive) of the compressor 48, power or current to a motor of the compressor 48, or other power or current used to move the compressor 48. The controller 100 can use power and current limiting to protect the compressor 48 (e.g., prime mover 84) or limit energy usage of the building, and such limiting can be quite stable in terms of the control methodology (e.g., the controller 100 can prevent droplet introduction before it occurs because it does not have to rely on detected droplets as an input to a feedback control loop). For example, the controller 100 may control the power of operation of the variable speed drive mover 84 or the current of operation of the fixed speed drive mover 84. The controller 100 may determine a predicted energy level of operation of the compressor 48 at which the suction flow from the evaporator 46 to the compressor 48 may be expected to cause liquid droplets to flow into the compressor 48, compare the predicted energy level to the actual operating condition energy level of the compressor 48, and determine to limit the capacity of the compressor 48 based on the comparison to protect the compressor 48 from the flow of liquid droplets.

[0020] The controller 100 may include a communication interface 102 and a processing circuit 104. The communication interface 102 may include a wired or wireless interface (e.g., a jack, an antenna, a transmitter, a receiver, a transceiver, a wired terminal, etc.) for communicating data with various systems, devices, or networks. For example, the communication interface 102 may include an Ethernet card and / or a port for transmitting and receiving data over an Ethernet-based communication network. In some embodiments, the communication interface 102 includes a wireless transceiver (e.g., a WiFi transceiver, a Bluetooth transceiver, an NFC transceiver, a ZigBee transceiver, etc.) for communicating over a wireless communication network. The communication interface 102 may be configured to communicate over a local area network (e.g., a building LAN, etc.) and / or a wide area network (e.g., the Internet, a cellular network, a wireless communication network, etc.) and may use a variety of communication protocols (e.g., BACnet, TCP / IP, point-to-point, etc.).

[0021] The communication interface 102 may facilitate receiving inputs from various sensors. The sensors may include, for example, a chilled fluid temperature sensor 74 configured to detect the temperature of the chilled fluid at the outlet of the evaporator 46, a suction pressure sensor 78 configured to detect the pressure of the refrigerant in the compressor suction line 72, a discharge pressure sensor 82 configured to detect the pressure of the refrigerant in the compressor discharge line 54, and / or other sensors of the chiller 22 and / or HVAC system 20 (e.g., a suction temperature sensor 76, a discharge temperature sensor 80, a chilled fluid temperature sensor 74, etc.). The communication interface 102 may receive inputs directly from the sensors, over a local network, and / or over a remote communication network. The communication interface 102 may enable communication between the controller 100 and the compressor 48.

[0022] The processing circuit 104 may comprise a processor 106 and a memory 108. The processor 106 may be a general purpose or special purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable processing components. The processor 106 may be configured to execute computer code or instructions (e.g., fuzzy logic, etc.) stored in the memory 108 or received from other computer readable media (e.g., CD-ROM, network storage, remote server, etc.) to perform one or more of the processes described herein.

[0023] The memory 108 may include one or more data storage devices (e.g., memory units, memory devices, computer readable storage media, etc.) configured to store data, computer code, executable instructions, or other forms of computer readable information. The memory 108 may include random access memory (RAM), read only memory (ROM), hard drive storage, temporary storage, non-volatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and / or computer instructions. The memory 108 may include database components, object code components, script components, or any other type of information structure for supporting various activities and information structures described in this disclosure. The memory 108 may be communicatively coupled to the processor 106 via the processing circuitry 104 and may include computer code for executing (e.g., by the processor 106) one or more of the processes described herein.

[0024] The memory 108 may include various modules to complete the processes described herein. More specifically, the memory 108 includes a condition detector 110, an energy predictor 112, and a compressor controller 114. Although various modules with specific functions are illustrated in FIG. 3, the controller 100 and memory 108 may include any number of modules to complete the functions described herein. For example, activities of multiple modules may be combined into a single module, and additional modules with additional functions may be included. The controller 100 may further control other processes beyond the scope of this disclosure, including, but not limited to, controlling the operation of various components of the refrigeration system 150 based on desired or expected load conditions.

[0025] The condition detector 110 may receive condition data from various sensors in the refrigeration system 150. For example, the condition detector 110 may receive pressure data from the evaporator pressure sensor 86 and the condenser pressure sensor 88. The condition detector 110 may also receive temperature data from a temperature sensor.

[0026] The energy predictor 112 is capable of receiving the condition data from the condition detector 110 and determining a predicted energy level of operation of the compressor 48 based on the received condition data. The predicted energy level may correspond to at least one of compressor speed, compressor capacity, water flow rate, water temperature, suction volumetric flow rate, compressor performance, motor performance, and starter performance.

[0027] The energy predictor 112 may determine a predicted energy level based on a first pressure received by the condition detector 110 from the evaporator pressure sensor 86 and a second pressure received by the condition detector 110 from the condenser pressure sensor 88. The energy predictor 112 may perform an energy prediction function to calculate the predicted energy level.

[0028] The energy prediction function may include one or more calculation parameters that the energy predictor 112 may apply to the first and second pressures to calculate a predicted energy level. The one or more calculation parameters may be determined based on experimental and / or simulation testing of the operation of the refrigeration system 150. For example, the one or more calculation parameters may be determined by identifying energy levels associated with various values ​​of the evaporator pressure and the condenser pressure and fitting a curve, function, or other representation to the energy levels based on the values ​​of the evaporator pressure and the condenser pressure. The energy levels may be identified by operating the refrigeration system 150 (or its drivetrain) at various operating conditions. The energy levels may be identified by operating the refrigeration system 150 at a part load condition, which may more accurately represent the operation of the refrigeration system when the one or more calculation parameters are used to predict the energy levels. It will be appreciated that the calculation parameters determined for the first refrigeration system 150 may be applied to various other refrigeration systems 150. Using inputs such as capacity, water flow rate, water temperature, along with feedback values ​​such as evaporator pressure, condenser pressure, suction volumetric flow rate, and input current (or input power), one or more calculation parameters can be determined for a particular refrigeration system using an iterative process due to dependencies between evaporator pressure (or saturation temperature), suction volumetric flow rate limit, capacity, and desired volumetric flow rate. If the calculation parameters are determined based on the drivetrain of the refrigeration system 150 (e.g., to extrapolate the determined calculation parameters to other units with similar drivetrains), performance parameters (e.g., compressor performance, motor performance, starter performance) can be determined based on boundary condition variables (e.g., suction pressure, volumetric flow rate (or dimensionless flow rate θ), and discharge pressure (or dimensionless head Ω)) of the compressor 48 to determine the corresponding input current (or input power). Thus, if the values ​​of the boundary condition variables (e.g., volumetric flow rate or θ) are selected to be at the appropriate limiting values, the drivetrain calculations can directly provide the data necessary to determine the calculation parameters.It will be appreciated that the calculation parameters may be determined using processing circuitry 104 or processing circuitry of a device separate from the refrigeration system 150 (or driveline) operating to identify the relationship between the evaporator pressure, condenser pressure, and droplet flow.

[0029] The energy predictor 112 may select a particular energy prediction function to perform based on operating state characteristics of the compressor 48, which may be stored by the energy predictor 112. The operating state characteristics may indicate whether the prime mover 84 of the compressor 48 operates in a variable speed or fixed speed operating mode. If the operating state characteristics indicate that the prime mover 84 operates in a variable speed operating mode, the energy predictor 112 may select the energy prediction function according to Equation 1.

[0030]

number

[0031] If the operating state characteristics indicate that prime mover 84 is to operate in a fixed speed operating mode, energy predictor 112 may select an energy prediction function according to Equation 2.

[0032]

number

[0033] In this manner, the energy predictor 112 can perform an appropriate energy prediction function using the calculation parameters and the first and second pressures (e.g., pevap=first pressure, pcond=second pressure) to calculate a predicted energy level. It will be appreciated that the values ​​of the calculation parameters can be determined by fitting a curve of the form shown in Equation 1 or Equation 2, as appropriate, to the values ​​of the energy levels identified as a function of the evaporator and condenser pressures. An iterative optimization process may be used to determine the values ​​of the calculation parameters. The functions shown in Equation 1 and Equation 2 can be linearized (e.g., by taking logarithms, such as the natural logarithm, of both sides of the respective equations) to reduce the computational requirements for determining the calculation parameters by allowing the use of line fitting methods, such as linear least squares.

[0034] The compressor controller 114 may control the operation of the compressor 48 (e.g., control the operation of the prime mover 84). The compressor controller 114 may output a control signal corresponding to a desired input power or input current to the compressor 48, including limiting the input power or input current as necessary. The compressor controller 114 may use operating state characteristics of the compressor 48 to determine whether to generate a control signal to control the input power (e.g., when the compressor 48 is operating in a variable speed operating mode) or the input current (e.g., when the compressor 48 is operating in a fixed speed operating mode). The compressor controller 114 may initially calculate the input power or input current based on input variables such as a desired water flow rate, water temperature, or other variables indicative of the performance of the refrigeration system 150. The compressor controller 114 may limit the initially calculated input power or input current to reduce or eliminate the flow of liquid droplets into the compressor 48.

[0035] The compressor controller 114 compares the predicted energy level determined by the energy predictor 112 to the on-state energy level. The predicted energy level may correspond to an energy level at which droplet flow from the evaporator 46 into the compressor 48 may be expected to occur given certain values ​​of evaporator pressure and condenser pressure. For example, the predicted energy level may exceed a design speed limit of the evaporator 46 or correspond to an energy level at which droplet flow is determined to occur through experimental and / or simulation testing. The on-state energy level may be a current energy level of the compressor 48. As such, the compressor controller 114 may use the comparison to determine whether the compressor 48 is operating in a condition that may exceed a predicted energy level at which droplet flow from the evaporator 46 into the compressor 48 may be expected to occur.

[0036] The compressor controller 114 may measure at least one of the actual input current and the actual input power. For example, the compressor controller 114 may include an input current sensor, such as a current transformer, to measure the actual input current. The compressor controller 114 may include an input power sensor, such as a voltage sensor, that may be used to determine the actual input power (e.g., based on the actual input current and the actual input power). The compressor controller 114 may: The energy level during the driving state may be determined based on at least one of an actual input current and an actual input power.

[0037] The compressor controller 114 modifies at least one of the input power or the input current to the compressor 48 based on the comparison satisfying the modification condition. For example, if the predicted energy level is a value that should not be exceeded, the compressor controller 114 can limit at least one of the input power or the input current in response to the operating state energy level exceeding the predicted energy level (e.g., limit at least one of the input power and the input current if the operating state energy level is greater than the predicted energy level). If the predicted energy level is set to a value that triggers a limit, the compressor controller 114 can limit at least one of the input power and the input current in response to the operating state energy level being equal to the predicted energy level (e.g., limit at least one of the input power and the input current if the predicted energy level is equal to the operating state energy level). The compressor controller 114 can calculate the predicted energy level as at least one of the predicted input current and the predicted input power such that the compressor controller 114 can perform the comparison by at least one of comparing the actual input current to the predicted input current and comparing the actual input power to the predicted input power.

[0038] If the comparison does not meet the change condition, such as when the energy level during the operating state is less than the predicted energy level, the compressor controller 114 may determine not to limit the input power or the input current, for example, the compressor controller 114 may continue to monitor the first pressure and the second pressure, and the compressor controller 114 may determine to increase at least one of the input power and the input current (if the desired performance, such as the water flow rate or water temperature, indicates a command to increase at least one of the input power and the input current). Thus, if the measured input power and / or current are above the predicted values, the compressor controller 114 can reduce the on-state capacity of the compressor 48, and if the measured input power and / or current are below the predicted values, the on-state capacity of the compressor 48 (and thus the refrigeration system 150) is not limited by the suction flow rate, and the compressor controller 114 can control at least one of the input power and the input current by performing various processes, such as by controlling at least one of the input power and the input current based on the Tcf of the chilled fluid leaving the evaporator 46 detected by the chilled fluid temperature sensor 74 (e.g., by comparing the Tcf to a desired Tcf value). The compressor controller 114 can perform capacity control of the compressor 48 based on one or more of a variable speed drive, a compressor inlet flow damper or pre-swirler flow throttle, a compressor discharge variable geometry diffusion flow throttle, or a capacity control slide valve (e.g., if the compressor 48 includes a screw compressor).

[0039] The compressor controller 114 may limit at least one of the input power or the input current by setting the at least one of the input power or the input current to a previous value. For example, the compressor controller 114 may maintain a database of power values ​​and current values. In response to a decision to limit the input power or the input current, the compressor controller 114 may retrieve a previous value of the input power or the input current from history, such as a previous value at a time when the compressor controller 114 determined not to change the at least one of the input power or the input current based on a corresponding previous predicted energy level.

[0040] The compressor controller 114 may maintain a database including the evaporator pressure, condenser pressure, input power, input current, predicted energy levels, and various other operating parameters, along with an indication that the comparison indicates that the input power or input current should be limited.

[0041] The compressor controller 114 can output an alert indicating that droplet flow may be occurring based on the comparison. For example, the compressor controller 114 can cause the communication interface 102 to send an alert. The alert may include information such as operational parameters maintained in a database by the compressor controller 114. The alert may include an indication of a value of a performance variable that corresponds to a changed condition being met, such as a water flow rate or water temperature that results in a predicted energy level associated with droplet flow.

[0042] 4 illustrates a method 400 for operating a refrigeration system (e.g., a chiller) according to an example embodiment. Method 400 may be performed using the HVAC system of FIG. 1 and / or the refrigeration system 150 of FIGS. 2 and 3.

[0043] At 405, a first pressure is received by the controller from an evaporator pressure sensor. The first pressure may represent a pressure of refrigerant flowing through the evaporator. The evaporator may receive a first flow of refrigerant, transfer heat to the first flow of refrigerant, and output a second flow of refrigerant.

[0044] A second pressure is received by the controller from the condenser pressure sensor at 410. The second pressure may represent the pressure of the refrigerant flowing through the condenser.

[0045] At 415, the controller determines a predicted energy level of operation of the compressor. The compressor may receive a second flow of refrigerant via piping between the evaporator and the compressor. The predicted energy level may be determined using an energy prediction function that uses the first pressure and the second pressure as inputs and evaluates the inputs using predetermined parameters. The compressor may include a prime mover that performs work on the second flow of refrigerant based on at least one of an input power to the prime mover and an input current to the prime mover. The prime mover may include a variable speed drive that the controller drives using the input power. The prime mover may include a fixed speed drive that the controller drives using the input current.

[0046] At 420, the controller compares a predicted energy level of operation of the compressor to the on-state energy level. The predicted energy level can be related to a flow of droplets in the second flow of refrigerant received by the compressor. The predicted energy level can correspond to a design speed limit of the evaporator. The compressor controller can determine the on-state energy level using at least one of an actual input current and an actual input power.

[0047] At 425, the controller determines whether the comparison satisfies a modification condition. The modification condition may correspond to the driving state energy level being greater than the predicted energy level or the driving state energy level being equal to or greater than the predicted energy level.

[0048] At 430, the controller limits at least one of the input power or input current to the prime mover based on the comparison satisfying the change condition. The controller can modify at least one of the input power and input current to limit at least one of the input power and input current to a value that can reduce or eliminate the flow of droplets from the evaporator into the compressor. The controller can output an alert in response to modifying at least one of the input power and input current to the prime mover based on the comparison satisfying the change condition. If the comparison does not satisfy the change condition, such as if the energy level during the running state is less than the predicted energy level, the controller can continue to monitor the pressures received from the evaporator pressure sensor and the condenser pressure sensor. If the comparison does not satisfy the change condition, such as if the energy level during the running state is less than the predicted energy level, the controller can limit the chiller. If the desired performance (eg, desired water flow rate or water temperature) indicates a command to increase the input power or input current, the input power or input current may continue to be increased as necessary.

[0049] References to "or" may be construed as inclusive, such that terms described using "or" can refer to either a single, a plurality, or all of the described terms. References to at least one of a list of consecutive terms may be construed as a disjunction, referring to either a single, a plurality, or all of the described terms. For example, a reference to "at least one of A and B" can include A only, B only, and both A and B. Such references used in combination with "comprising" or other open terminology can include additional items.

[0050] The construction and configuration of the systems and methods shown in the various exemplary embodiments are merely exemplary. While only exemplary embodiments are detailed in this disclosure, many modifications are possible (e.g., changes in the size, dimensions, structure, shape and proportions of various elements, parameter values, mounting arrangements, amounts of materials used, colors, orientations, etc.). For example, the location of elements can be reversed or otherwise changed, and the nature or number or location of distinct elements can be altered or changed. Such modifications are therefore intended to be included within the scope of this disclosure. The order or sequence of any process or method steps can be changed or resequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions can be made in the design, operating conditions and arrangements of the exemplary embodiments without departing from the scope of this disclosure.

Claims

1. A chiller, an evaporator that receives a first flow of refrigerant, transfers heat to the first flow of refrigerant, and outputs a second flow of refrigerant; a compressor receiving the second flow of refrigerant via piping between the evaporator and the compressor, the compressor comprising a prime mover that performs work on the second flow of refrigerant based on at least one of an input electrical power to the prime mover and an input current to the prime mover; a first pressure sensor that detects a first pressure of the refrigerant in the evaporator; a second pressure sensor for detecting a second pressure of the refrigerant in a condenser of the chiller; a controller for determining a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being associated with a flow of droplets in the second flow of refrigerant received by the compressor, comparing the predicted energy level to an operating state energy level of the compressor, and modifying the at least one of the input power and the input current to the prime mover based on the comparison satisfying a modification condition; Equipped with a chiller.

2. the controller determining the predicted energy level using an energy prediction function that uses the first pressure and the second pressure as inputs and evaluates the inputs using predetermined parameters. The chiller of claim 1 comprising:

3. the prime mover including a variable speed drive that the controller drives using the input power; The chiller of claim 1 comprising:

4. the prime mover including a fixed speed drive that the controller drives using the input current; The chiller of claim 1 comprising:

5. the predicted energy level corresponds to the design speed limit of the evaporator; The chiller of claim 1 comprising:

6. The capacity of the compressor at maximum operating condition is greater than the capacity of the evaporator at maximum operating condition. The chiller of claim 1 comprising:

7. outputting an alert in response to modifying the at least one of the input power and the input current to the prime mover based on the comparison satisfying the modification condition. The chiller of claim 1 comprising:

8. The controller determines that the comparison satisfies the change condition when the driving state energy level at least one of meets and exceeds the predicted energy level. The chiller of claim 1 comprising:

9. receiving, by the controller, a first pressure from an evaporator pressure sensor coupled to the evaporator; receiving, by the controller, a second pressure from a condenser pressure sensor coupled to the condenser; And, determining, by the controller, a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being related to a flow of liquid droplets from the evaporator to the condenser; comparing, by the controller, the predicted energy level to an operating state energy level of the compressor; varying at least one of an input power and an input current to a prime mover of the compressor based on the comparison satisfying a change condition; A method for restricting chiller inlet flow, comprising:

10. determining, by the controller, the predicted energy level using an energy prediction function that uses the first pressure and the second pressure as inputs and evaluates the inputs using predetermined parameters; 10. The method of claim 9, comprising:

11. driving, by said controller, a variable speed drive of said prime mover using said input power; 10. The method of claim 9, comprising:

12. driving, by said controller, a fixed speed drive of said prime mover using said input current; 10. The method of claim 9, comprising:

13. the predicted energy level corresponds to the design speed limit of the evaporator; 10. The method of claim 9, comprising:

14. The capacity of the compressor at maximum operating condition is greater than the capacity of the evaporator at maximum operating condition. The chiller of claim 1 comprising:

15. outputting, by the controller, an alert in response to modifying the at least one of the input power and the input current to the prime mover based on the comparison satisfying the modification condition.

10. The method of claim 9, comprising:

16. one or more processors; When executed by the one or more processors, the one or more processors receiving a first pressure from an evaporator pressure sensor coupled to the evaporator at the condition detector; receiving a second pressure from a condenser pressure sensor coupled to the condenser at the condition detector; determining, by an energy predictor, a predicted energy level of operation of the compressor based on the first pressure and the second pressure, the predicted energy level being related to a flow of liquid droplets from the evaporator to the condenser; comparing, by a compressor controller, the predicted energy level to an operating state energy level of the compressor; The compressor controller varies at least one of the power and the current to the compressor prime mover based on the comparison satisfying a variation condition. a memory device storing computer readable instructions for causing the A chiller controller comprising:

17. the energy predictor uses the first pressure and the second pressure as inputs and determines the predicted energy level using an energy prediction function that evaluates the inputs using predetermined parameters.

20. The chiller controller of claim 16, comprising:

18. the controller at least one of: (i) using the electrical power to drive a variable speed drive of the prime mover; and (ii) using the electrical current to drive a fixed speed drive of the prime mover.

20. The chiller controller of claim 16, comprising:

19. the predicted energy level corresponds to the design speed limit of the evaporator; 20. The chiller controller of claim 16, comprising:

20. outputting an alert in response to modifying the at least one of the power and the current to the prime mover based on the comparison satisfying the modification condition.

20. The chiller controller of claim 16, comprising:

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