Refrigeration appliance

Abstract

A refrigeration apparatus including a refrigerant circuit is disclosed. The refrigerant circuit includes a compressor including a compressor fan and a motor driving the compressor fan; a condensing device downstream of the compressor, the condensing device including a condenser and a subcooler; an expansion valve downstream of the condensing device; an evaporator between the expansion valve and the compressor; a main refrigerant line fluidly connecting the compressor, the condensing device, the expansion valve, and the evaporator in series in a loop. A motor cooling line including a motor cooling valve fluidly connects the subcooler to the motor to tap refrigerant from the main refrigerant line to cool the motor, the motor cooling line also connecting to the main refrigerant line at a return point upstream of the compressor fan to return refrigerant to the main refrigerant line at the compressor fan. A bypass line fluidly connects an outlet of the condenser to the expansion valve to bypass the subcooler, the bypass line including a bypass valve to selectively allow refrigerant in the main refrigerant line to bypass the subcooler.

Description

Technical Field

[0001] This invention relates to a refrigeration device and a method for operating the refrigeration device. Background Technology

[0002] A refrigeration unit typically includes a compressor, condenser, expansion valve, and evaporator, which are connected in series and through which refrigerant flows. Ambient air flows over the condenser to cool the pressurized refrigerant inside, while the air or water to be cooled flows over the evaporator to transfer heat to the refrigerant, thereby cooling the air.

[0003] Compressor components heat up during operation and require cooling. Refrigerant from the condenser can be passively driven to the compressor and used to cool its components. However, under certain conditions, the amount of refrigerant directed to the compressor may be insufficient to cool its components. To overcome this problem, previously considered methods of operating the refrigeration unit relied on decoupling from the most efficient operation. Summary of the Invention

[0004] According to a first aspect, a refrigeration device including a refrigerant circuit is provided, the refrigerant circuit comprising: a compressor, the compressor including a compressor fan and a motor driving the compressor fan; a condensing unit disposed downstream of the compressor, the condensing unit including a condenser and a subcooler; an expansion valve disposed downstream of the condensing unit; an evaporator disposed between the expansion valve and the compressor; a main refrigerant line fluidly connecting the compressor, the condensing unit, the expansion valve and the evaporator in a loop series; and a motor cooling line, the motor cooling line including... The system includes a motor cooling valve, wherein the motor cooling line fluidly connects the subcooler to the motor to divert refrigerant from the main refrigerant line to cool the motor, wherein the motor cooling line is further connected to the main refrigerant line at a return point upstream of the compressor fan to allow refrigerant to return to the main refrigerant line at the compressor fan; wherein the refrigerant circuit also includes a bypass line fluidly connecting the outlet of the condenser to the expansion valve to bypass the subcooler, wherein the bypass line includes a bypass valve to selectively allow refrigerant in the main refrigerant line to bypass the subcooler.

[0005] The compressor may include an inverter. The subcooler may be connected to the inverter via an inverter cooling line including an inverter cooling valve, and wherein the inverter cooling line is further connected to the main refrigerant line at the return point to guide refrigerant from the inverter to the main refrigerant line at the compressor fan.

[0006] The refrigeration equipment may include a controller. The controller may be configured to control the opening and closing of the bypass valve. The controller may be configured to control the opening and closing of the inverter cooling valve. The controller may be configured to control the opening and closing of the motor cooling valve. An additional controller may be present, integrated with the compressor, and configured to control the operation of the motor and the inverter, and to control the opening and closing of the motor cooling valve, the inverter cooling valve, and / or the expansion valve.

[0007] The bypass valve may be a regulating valve. The controller may be configured to control the bypass valve to control the flow rate of refrigerant through the bypass valve.

[0008] The refrigeration equipment may include a first pressure sensor and a second pressure sensor, the first pressure sensor being arranged to monitor the pressure of the refrigerant leaving the subcooler, and the second pressure sensor being arranged to monitor the pressure in the main refrigerant line at the return point; wherein, the controller is arranged to receive a first pressure parameter from the first pressure sensor and a second pressure parameter from the second pressure sensor, and the controller is arranged to control the bypass valve based on the first pressure parameter and the second pressure parameter.

[0009] The refrigeration equipment may include a first pressure sensor, a second pressure sensor, and a third pressure sensor. The first pressure sensor is arranged to monitor the pressure of the refrigerant leaving the subcooler, the second pressure sensor is arranged to monitor the pressure in the main refrigerant line at the compressor inlet, and the third pressure sensor is arranged to monitor the pressure in the main refrigerant line at the compressor outlet. The controller is arranged to receive a first pressure parameter from the first pressure sensor, a second pressure parameter from the second pressure sensor, and a third pressure parameter from the third pressure sensor. The controller may be arranged to control the bypass valve based on the first pressure parameter, the second pressure parameter, and the third pressure parameter.

[0010] The compressor may be a two-stage compressor including a first-stage compressor fan and a second-stage compressor fan, wherein the return point is located between the first-stage compressor fan and the second-stage compressor fan.

[0011] According to a second aspect, a method for operating the refrigeration equipment described above is provided, the method comprising: determining whether there is insufficient refrigerant being supplied from the subcooler to the compressor; and, in response to determining that there is insufficient refrigerant being supplied from the subcooler to the compressor, controlling the bypass valve to increase the flow rate of refrigerant through the bypass valve.

[0012] The refrigerant supplied from the subcooler to the compressor may involve supplying refrigerant from the subcooler to the compressor motor via motor cooling lines to cool the motor.

[0013] Increasing the flow rate of refrigerant through the bypass valve may include: opening the bypass valve, or gradually increasing the size of the opening through the bypass valve.

[0014] Determining whether there is insufficient refrigerant being delivered to the compressor may include: monitoring a first pressure parameter related to the pressure of the refrigerant in the main refrigerant line at the outlet of the subcooler; monitoring a second pressure parameter related to the pressure in the main refrigerant line at the return point upstream of the compressor fan; and determining whether there is insufficient refrigerant being delivered to the compressor based on the first pressure parameter and the second pressure parameter.

[0015] The second pressure parameter may relate to the pressure in the main refrigerant line located at the return point between the first-stage compressor fan and the second-stage compressor fan of the two-stage compressor.

[0016] Determining whether there is insufficient refrigerant being delivered to the compressor may include: calculating a difference parameter related to the difference between the first pressure parameter and the second pressure parameter; comparing the difference parameter with the first threshold; and if the difference parameter is lower than the first threshold, determining that there is insufficient refrigerant being delivered to the compressor.

[0017] The method may further include: determining whether excessive refrigerant is being supplied to the compressor. The method may also include: in response to determining that excessive refrigerant is being supplied to the compressor, reducing the flow of refrigerant through the bypass valve.

[0018] Reducing the flow rate of refrigerant through the bypass valve may include closing the bypass valve or gradually reducing the size of the opening through the bypass valve.

[0019] Determining whether excessive refrigerant is being supplied to the compressor may include: comparing the difference parameter with a second threshold; and if the difference parameter is higher than the second threshold, determining that excessive refrigerant is being supplied to the compressor.

[0020] The first threshold and the second threshold can be the same.

[0021] Those skilled in the art will understand that, except in cases of mutual exclusion, any feature or parameter described with respect to any of the foregoing aspects can be applied to any other aspect. Furthermore, except in cases of mutual exclusion, any feature or parameter described herein can be applied to any aspect and / or combined with any other feature or parameter described herein. Attached Figure Description

[0022] Embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0023] Figure 1 A schematic diagram of an exemplary refrigeration device is shown; and

[0024] Figure 2 and Figure 3 This is a flowchart illustrating the steps of an exemplary method for operating a refrigeration device. Detailed Implementation

[0025] Figure 1 An exemplary refrigeration device 10 including a refrigerant circuit is shown. The refrigerant circuit includes a compressor 12, a condenser 14, an expansion valve 16, and an evaporator 18, which are connected in series with each other via a main refrigerant line 11 and fluidly connected in the order described above, wherein the evaporator is connected to the compressor 12 to form a circuit.

[0026] In this example, compressor 12 is a two-stage compressor including a first-stage compressor fan 20 and a second-stage compressor fan 22. In other examples, the compressor may have only one stage, or the compressor may have more than two stages.

[0027] The compressor 12 includes a motor 24 configured to drive a first-stage compressor fan 20 and a second-stage compressor fan 22. The motor 24 is connected to an inverter 26 configured to control the speed of the motor 24.

[0028] The condensing unit 14 is located downstream of the compressor 12 and includes two condensing stages. In the first stage, the condensing unit 14 includes a condenser 28, and in the second stage, the condensing unit 14 includes a subcooler 30. The subcooler 30 is located downstream of the condenser 28.

[0029] The expansion valve 16 is located downstream of the condensing unit 14, and the evaporator 18 is located between the expansion valve 16 and the compressor 12.

[0030] A check valve 32 is provided between the compressor 12 and the condenser 14. The check valve 32 is configured to ensure that the refrigerant flows from the compressor 12 to the condenser 28 and to prevent the refrigerant from flowing from the condenser 28 to the compressor 12 in the opposite direction.

[0031] Cooling line 34 directly fluidly connects subcooler 30 to compressor 12 to supply subcooled refrigerant to compressor 12, thereby cooling compressor 12. In this example, cooling line 34 diverts subcooled refrigerant from main refrigerant line 11, which connects subcooler 30 to expansion valve 16, and directs the diverted refrigerant to compressor 12.

[0032] Within the compressor 12, the cooling line 34 is divided into a motor cooling line 36 and an inverter cooling line 38. The motor cooling line 36 fluidly connects the subcooler 30 to the motor 24, allowing subcooled refrigerant to be directed to the motor 24 and permitted to expand to cool the motor 24 via heat transfer. The inverter cooling line 38 fluidly connects the subcooler 30 to the inverter 26, allowing subcooled refrigerant to be directed to the inverter 26 and permitted to expand to cool the inverter via heat transfer.

[0033] Motor cooling line 36 includes a motor cooling valve 37 configured to control the flow rate of refrigerant through motor cooling line 36 to motor 24. Inverter cooling line 38 includes an inverter cooling valve 39 configured to control the flow rate of refrigerant through inverter cooling line 38 to inverter 26.

[0034] The motor cooling line 36 and the inverter cooling line 38 are reconnected to the main refrigerant line 11 at the return point 40 between the first-stage compressor fan 20 and the second-stage compressor fan 22, so that the refrigerant diverted from the motor cooling line 36 and the inverter cooling line 38, after being used to cool the motor 24 and the inverter 26 respectively, re-enters the main refrigerant line 11. The maximum possible refrigerant flow through the motor cooling line 36 and the inverter cooling line 38 (i.e., if the motor cooling valve 37 and the inverter cooling valve 39 are fully open) depends on the refrigerant pressure in the main refrigerant line 11 at the return point 40 and the refrigerant pressure in the main refrigerant line 11 at the outlet of the subcooler 30. The pressure at return point 40 must be at least a threshold amount lower than the pressure at the outlet of subcooler 30 in order to passively drive the subcooled refrigerant through motor cooling line 36 and inverter cooling line 38 to return point 40 (i.e., there must be a sufficiently high pressure difference to drive the refrigerant through motor cooling line 36 and inverter cooling line 38).

[0035] The threshold value can be an absolute threshold, or it can depend on the load on compressor 12.

[0036] In an example where the compressor is a single-stage compressor including a compressor fan, the motor cooling line and inverter cooling line can be connected to the main refrigerant line upstream of the compressor fan (i.e., the return point can be located upstream of the compressor fan).

[0037] The outlet of condenser 28 is also fluidly connected to the main refrigerant line 11 upstream of expansion valve 16 via bypass line 42. Bypass line 42 is arranged to allow at least some of the refrigerant in the main refrigerant line 11 to bypass subcooler 30, such that some refrigerant flows directly from condenser 28 to the main refrigerant line 11 between subcooler 30 and expansion valve 16.

[0038] The bypass line 42 includes a bypass valve 44 configured to selectively open and close in order to control the flow rate of refrigerant through the bypass line 42.

[0039] Controller 50 is connected to bypass valve 44, motor cooling valve 37, inverter cooling valve 39, and expansion valve 16. Controller 50 is configured to selectively open and close these valves, thereby controlling the flow of refrigerant through the refrigerant circuit. In some examples, an additional controller may be present, integrated with the compressor, and configured to control the motor cooling valve and inverter cooling valve. Controller 50 or the additional controller may also control the operation of the inverter and compressor during use.

[0040] In this example, bypass valve 44, motor cooling valve 37, inverter cooling valve 39, and expansion valve 16 are regulating valves, allowing controller 50 to change the orifice size of each valve, thereby precisely controlling the refrigerant flow through these valves. In other examples, these valves may be two-state valves, which can selectively open and close but cannot control the orifice size and therefore cannot directly control the flow through these valves. In some examples, the valves may be any combination of two-state valves and regulating valves.

[0041] Therefore, in this example, the controller 50 is configured to control the bypass valve 44, the motor cooling valve 37, the inverter cooling valve 39, and the expansion valve 16, thereby precisely controlling the flow rate of refrigerant through the bypass line 42, the motor cooling line 36, the inverter cooling line 38, and the main refrigerant line 11 during use.

[0042] In this example, the refrigeration device 10 also includes a first pressure sensor 52, which is arranged to monitor the pressure of the refrigerant in the main refrigerant line 11 at the outlet of the subcooler 30. The refrigeration device 10 also includes a second pressure sensor 54 and a third pressure sensor 55, whereby the second pressure sensor 54 is arranged to monitor the pressure in the main refrigerant line 11 upstream (i.e., at the inlet) of the first compressor fan 20, and the third pressure sensor 55 is arranged to monitor the pressure downstream (i.e., at the outlet) of the second compressor fan 22. The controller 50 calculates the refrigerant pressure at return point 40 based on the pressure monitored by the second pressure sensor 54 and the pressure monitored by the third pressure sensor 55. The refrigerant pressure at return point 40 (p...) is then... r The calculation is: the square root of the product of the refrigerant pressure (p1) at the inlet of the first compressor fan 20 and the refrigerant pressure (p2) at the outlet of the second compressor fan (i.e., ).

[0043] In the example where the compressor is a single-stage compressor with one compressor fan, the second pressure sensor can be arranged to monitor the pressure in the main refrigerant line upstream of the compressor fan, and a third pressure sensor may not be present. In other examples, the sensor can be any sensor capable of outputting a parameter indicating refrigerant pressure, such as a temperature sensor. In other examples, a pressure sensor may be present and arranged to directly monitor the pressure at return point 40.

[0044] Controller 50 is configured to monitor a first pressure parameter received from a first pressure sensor 52, which relates to the pressure of the refrigerant in the main refrigerant line 11 downstream of the subcooler 30 or to the pressure of the refrigerant at the cooling line 34. Controller 50 is configured to monitor a second pressure parameter received from a second pressure sensor 54, which relates to the pressure of the refrigerant in the main refrigerant line 11 at the return point 40. Controller 50 is configured to control bypass valve 44 based on the first and second pressure parameters. Reference will be made below. Figure 2 and Figure 3 Describe the process in more detail.

[0045] The refrigeration equipment may also include a temperature sensor arranged to monitor the refrigerant temperature at the outlet of the condenser, the refrigerant temperature at the outlet of the subcooler, and / or the refrigerant temperature downstream of the expansion device.

[0046] Refrigeration unit 10 operates under normal conditions with bypass valve 44 closed, allowing all refrigerant to pass through subcooler 30. The vaporized refrigerant is compressed in compressor 12, thereby pressurizing the refrigerant and increasing its temperature. For example, for an outdoor ambient temperature of 35°C, the vaporized refrigerant can enter the compressor at approximately 2.7 bar (270 kPa) pressure and 6°C temperature, and exit the compressor at approximately 10 bar (1000 kPa) pressure and 50°C temperature. Therefore, the pressure at return point 40 is calculated as follows: The refrigerant leaves the compressor 12 in the gaseous phase.

[0047] The refrigerant passes through a condenser 14, where it first passes through a condenser 28 to condense itself by heat transfer to the ambient air. The refrigerant is discharged in liquid form from the outlet of the condenser 28. The refrigerant then passes through a subcooler 30, where it is further cooled. Due to the large mass flow in the narrow channels, there is a pressure loss as the refrigerant passes through the condenser 28 and subcooler 30. For example, the refrigerant may enter the condenser at 10 bar (1000 kPa) (the same pressure as the refrigerant leaving the compressor 12) and may lose 0.5 bar (50 kPa) of pressure as it passes through the condenser 28. The refrigerant may lose an additional 1.5 bar (150 kPa) of pressure as it passes through the subcooler 30, leaving it at 8 bar (800 kPa). This leaves a pressure difference of 2.8 bar (280 kPa) between the return point 40 and the outlet of the subcooler 30. This 2.8 bar pressure difference is sufficient to allow refrigerant to flow through the motor cooling line 36 and the inverter cooling line 38 by opening the corresponding motor cooling valve 37 and inverter cooling valve 39.

[0048] The refrigerant then flows through expansion valve 16, where it expands. This reduces the refrigerant pressure and, consequently, the temperature, making the refrigerant colder than the water or air being cooled. For example, the refrigerant pressure downstream of expansion valve 16 could be 2.7 bar (270 kPa), and the refrigerant temperature downstream of expansion valve 16 could be 6°C.

[0049] The opening in the expansion valve 16 can be variable, allowing the pressure drop of the refrigerant passing through the expansion valve to change, and thus the temperature drop of the refrigerant passing through the expansion valve to change. The size of the opening can be controlled to ensure that the temperature of the refrigerant leaving the expansion valve 16 and thus entering the evaporator 18 remains constant, thereby keeping the cooling capacity of the refrigeration unit 10 constant.

[0050] The refrigerant downstream of expansion valve 16 is then directed to evaporator 18, where heat exchange occurs between the air or water to be cooled and the cooled refrigerant. The refrigerant evaporates, causing it to leave evaporator 18 as a gaseous phase, thus cooling the air.

[0051] During operation, the motor 24 and inverter 26 are heated and must be cooled. The controller 50 controls the motor cooling valve 37 and the inverter cooling valve 39 to control the flow of subcooled refrigerant to the motor 24 and inverter 26, respectively.

[0052] Under operating conditions with low ambient temperatures (e.g., 0°C), even with the motor cooling valve 37 and inverter cooling valve 39 fully open, the refrigerant flow from the subcooler 30 to the compressor 12 may be insufficient to cool the motor 24 and inverter 26. Under these operating conditions, the bypass valve 44 can be opened to allow for a greater refrigerant supply to the compressor, as explained below.

[0053] Figure 2 and Figure 3 This is a flowchart illustrating a method for operating an exemplary refrigeration device 10 to adjust the amount of refrigerant supplied to the compressor 12 as needed. This method can be used when the refrigeration device 10 is experiencing an abnormal condition.

[0054] For example, this situation may occur when the ambient temperature is low, such as 10°C. The compressor outlet pressure may be 5.8 bar (580 kPa), the refrigerant pressure downstream of expansion valve 16 may be 2.7 bar (270 kPa), and the refrigerant temperature at the compressor inlet may be 30°C. Therefore, the pressure at return point 40 is... With the same pressure drop across condenser 28 and subcooler 30, totaling 2 bar (200 kPa), the pressure at the outlet of subcooler 30 is 5.8 bar - 2 bar = 3.8 bar (380 kPa), resulting in a pressure difference of -0.2 bar (-20 kPa) between the return point 40 and the outlet of subcooler 30. In this situation, even with motor cooling valve 37 and inverter cooling valve 39 fully open, no refrigerant is delivered to motor 24 and inverter 26 for cooling. The low ambient air temperature in this case means a significant pressure loss across condenser 28 and subcooler 30, making the pressure difference between cooling line 34 and return point 40 insufficient to drive enough refrigerant to motor 24 and inverter 26, even with motor cooling valve 37 and inverter cooling valve 39 fully open. Therefore, insufficient cooling of motor 24 and inverter 26 may cause these components to overheat, potentially leading to damage or malfunction. As described above, the pressure difference between cooling line 34 and return point 40 can be increased by opening bypass valve 44. This allows refrigerant to bypass subcooler 30, resulting in a smaller pressure drop between the outlet of condenser 28 and cooling line 34.

[0055] Figure 2 A method 200 for operating the refrigeration equipment 10 to overcome these conditions is shown.

[0056] In step 202, the method determines whether there is not enough refrigerant delivered from the main refrigerant line downstream of the subcooler 30 to the compressor 12 (e.g., not enough to cool the motor 24 and the inverter 26).

[0057] If it is determined that insufficient refrigerant is being delivered to compressor 12, the method proceeds to step 204, in which bypass valve 44 is opened to increase the refrigerant flow through bypass valve 44. Increasing the refrigerant flow through bypass valve 44 reduces the refrigerant flow through subcooler 30, causing an increase in refrigerant pressure in the main refrigerant line 11 between subcooler 30 and expansion valve 16. This is because less refrigerant experiences pressure loss through subcooler 30.

[0058] Increasing the pressure of the refrigerant in the main refrigerant line 11 at the cooling line 34 means that the pressure difference between the refrigerant line 34 and the return point 40 increases, thereby driving more refrigerant through the motor cooling line 36 and the inverter cooling line 38.

[0059] In this example, bypass valve 44 is a regulating valve, and in step 204, bypass valve 44 is gradually opened, and the method returns to step 202 to determine whether there is still insufficient refrigerant being supplied to compressor 12. This creates a negative feedback loop. In other examples, the bypass valve can be controlled to open by a specific amount depending on the degree of refrigerant shortage to compressor 12.

[0060] If sufficient refrigerant is supplied to compressor 12, the method determines in step 206 whether excessive refrigerant is being supplied to the compressor. If no excessive refrigerant is being supplied, and the supplied refrigerant is not insufficient, the level of refrigerant being supplied is at the desired setpoint. The method then proceeds to step 208, in which no changes are made to bypass valve 44, and the method returns to step 202.

[0061] If it is determined that excessive refrigerant is being supplied to compressor 12, the method proceeds to step 210 to reduce the flow of refrigerant through bypass valve 44 (e.g., this is achieved by reducing the size of the opening in bypass valve 44 or closing bypass valve 44). If bypass valve 44 is already closed, refrigeration unit 10 can return to normal operation, in which bypass valve 44 is closed. The method then returns to step 202.

[0062] Figure 3 An exemplary method for determining whether insufficient, excessive, or just enough refrigerant is being supplied to compressor 12 is illustrated in detail. This is determined by monitoring the pressure difference from cooling line 34 to return point 40. Ideally, the pressure difference will fall within a set range or at a set point, at which point it will be determined that just enough refrigerant is being supplied to compressor 12. The set range can be an absolute range of acceptable pressure differences, or the set range can vary and can be calculated based on the load on compressor 12.

[0063] In the method described below, controller 50 is configured to maintain the pressure difference within a set range, which is limited between a lower threshold and an upper threshold.

[0064] In the example where the threshold depends on the load on compressor 12, controller 50 can determine the threshold in real time by monitoring the compressor load and looking up the corresponding threshold from a lookup table. In other examples, the threshold can be calculated using a formula based on the compressor load. For example, the minimum threshold pressure when the compressor load is 30% can be 0.2 bar (20 kPa), while the minimum threshold pressure when the compressor load is 100% can be as high as 1 bar (100 kPa) multiple times.

[0065] In step 220, the method includes monitoring a first pressure parameter related to the pressure of the refrigerant in the main refrigerant line 11 at the outlet of the subcooler 30. This can be monitored by a first pressure sensor 52.

[0066] In step 222, the method includes monitoring a second pressure parameter relating to the pressure of the refrigerant in the main refrigerant line 11 at return point 40 (i.e., between the first-stage compressor fan 20 and the second-stage compressor fan 22). This can be monitored using a second pressure sensor 54. In an example where the compressor is a single-stage compressor with only one compressor fan, the second pressure parameter may relate to the pressure of the refrigerant in the main refrigerant line upstream of the compressor fan.

[0067] The method determines in steps 224 to 234 whether there is insufficient refrigerant, just enough refrigerant, or too much refrigerant being delivered to compressor 12, based on the first pressure parameter and the second pressure parameter.

[0068] In step 224, the method includes calculating a difference parameter relating to the difference between the first pressure parameter and the second pressure parameter. This difference parameter will indicate the pressure difference of the refrigerant between the outlet of the subcooler 30 (i.e., the cooling line 34) and the return point 40 of the compressor.

[0069] In step 226, the difference parameter is compared with a lower threshold, and it is determined whether the difference parameter is lower than the lower threshold. If the difference parameter is lower than the lower threshold, it is determined in step 228 that the pressure difference between the subcooler 30 and the return point 40 is not high enough, so that not enough refrigerant is delivered to the compressor 12 to cool it. If the difference parameter is not lower than the lower threshold (i.e., the difference parameter is higher than the lower threshold), the method proceeds to step 230.

[0070] In step 230, the difference parameter is compared with a second upper limit threshold, and it is determined whether the difference parameter is higher than the upper limit threshold. If the difference parameter is higher than the upper limit threshold, it is determined in step 232 that too much refrigerant has been delivered to compressor 12. If the difference parameter is lower than or equal to the upper limit threshold, the difference parameter must be within the set range, and thus it is determined in step 234 that just enough refrigerant has been delivered to compressor 12.

[0071] In examples where the ideal pressure difference is a setpoint rather than a set range, the upper and lower thresholds can be the same, thus determining that sufficient refrigerant is being delivered to the compressor only when the difference parameter equals the threshold or the setpoint. In such examples, if the difference parameter is higher than the threshold, it is determined that too much refrigerant is being delivered to the compressor, and if the difference parameter is lower than the threshold, it is determined that insufficient refrigerant is being delivered to the compressor.

[0072] In this example, the controller 50 implementing the method controls the bypass valve 44 with a negative feedback loop to gradually increase or decrease the flow through the bypass valve 44, thereby maintaining the cooling of the compressor 12 at the desired point.

[0073] Although it has been described that determining whether there is insufficient or excessive refrigerant supplied to the compressor is based on the pressure monitored at the outlet of the subcooler 30 and the return point 40, this can be determined by other means, such as by monitoring the flow rate of fluid through the cooling lines, motor cooling lines and / or inverter cooling lines, or by monitoring the temperature of the motor 24 and the inverter 26 to infer that there is insufficient refrigerant if the motor temperature rises above a threshold.

[0074] It will be understood that the present invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the concepts described herein. Unless mutually exclusive, any feature may be used alone or in combination with any other feature, and this disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.

Claims

1. A refrigeration device including a refrigerant circuit, the refrigerant circuit comprising: A compressor, the compressor including a compressor fan and a motor that drives the compressor fan; A condensing device, located downstream of the compressor, comprising a condenser and a subcooler; An expansion valve is located downstream of the condensation unit; An evaporator is disposed between the expansion valve and the compressor; The main refrigerant line is fluidly connected in series in a loop: the compressor, the condenser, the expansion valve, and the evaporator; and A motor cooling line, including a motor cooling valve, fluidly connecting the subcooler to the motor to divert refrigerant from the main refrigerant line to cool the motor, wherein the motor cooling line is further connected to the main refrigerant line at a return point located upstream of the compressor fan to allow refrigerant to return to the main refrigerant line at the compressor fan; The refrigerant circuit further includes a bypass line that fluidly connects the outlet of the condenser to the expansion valve to bypass the subcooler. The bypass line includes a bypass valve to selectively allow refrigerant in the main refrigerant line to bypass the subcooler. The refrigeration equipment also includes a controller configured to control the opening and closing of the bypass valve. A first pressure sensor and a second pressure sensor, the first pressure sensor being arranged to monitor the pressure of the refrigerant leaving the subcooler, and the second pressure sensor being arranged to monitor the pressure in the main refrigerant line at the return point; The controller is configured to receive a first pressure parameter from the first pressure sensor and a second pressure parameter from the second pressure sensor, and the controller is configured to control the bypass valve based on the first pressure parameter and the second pressure parameter.

2. The refrigeration equipment according to claim 1, wherein, The compressor includes an inverter, and the subcooler is connected to the inverter via an inverter cooling line including an inverter cooling valve, and the inverter cooling line is further connected to the main refrigerant line at the return point to guide refrigerant from the inverter to the main refrigerant line at the compressor fan.

3. The refrigeration equipment according to claim 2, comprising a controller configured to control the opening and closing of the bypass valve, wherein, The controller is configured to control the opening and closing of the inverter cooling valve.

4. The refrigeration equipment according to any one of claims 1-3, wherein, The bypass valve is a regulating valve, and the controller is configured to control the bypass valve to control the flow rate of refrigerant through the bypass valve.

5. The refrigeration equipment according to any one of claims 1-3, wherein, The compressor is a two-stage compressor including a first-stage compressor fan and a second-stage compressor fan, wherein the return point is located between the first-stage compressor fan and the second-stage compressor fan.

6. The refrigeration equipment according to any one of claims 1-3, wherein, The controller is configured to control the opening and closing of the motor cooling valve.

7. A refrigeration device including a refrigerant circuit, the refrigerant circuit comprising: A compressor, the compressor including a compressor fan and a motor that drives the compressor fan; A condensing device, located downstream of the compressor, comprising a condenser and a subcooler; An expansion valve is located downstream of the condensation unit; An evaporator is disposed between the expansion valve and the compressor; The main refrigerant line is fluidly connected in series in a loop: the compressor, the condenser, the expansion valve, and the evaporator; and A motor cooling line, including a motor cooling valve, fluidly connecting the subcooler to the motor to divert refrigerant from the main refrigerant line to cool the motor, wherein the motor cooling line is further connected to the main refrigerant line at a return point located upstream of the compressor fan to allow refrigerant to return to the main refrigerant line at the compressor fan; The refrigerant circuit further includes a bypass line that fluidly connects the outlet of the condenser to the expansion valve to bypass the subcooler. The bypass line includes a bypass valve to selectively allow refrigerant in the main refrigerant line to bypass the subcooler. The refrigeration equipment also includes: A controller configured to control the opening and closing of the bypass valve. A first pressure sensor, a second pressure sensor, and a third pressure sensor are provided, wherein the first pressure sensor is arranged to monitor the pressure of the refrigerant leaving the subcooler, the second pressure sensor is arranged to monitor the pressure in the main refrigerant line at the inlet of the compressor, and the third pressure sensor is arranged to monitor the pressure in the main refrigerant line at the outlet of the compressor. The controller is configured to receive a first pressure parameter from the first pressure sensor, a second pressure parameter from the second pressure sensor, and a third pressure parameter from the third pressure sensor, and the controller is configured to control the bypass valve based on the first pressure parameter, the second pressure parameter, and the third pressure parameter.

8. The refrigeration equipment according to claim 7, wherein, The compressor includes an inverter, and the subcooler is connected to the inverter via an inverter cooling line including an inverter cooling valve, and the inverter cooling line is further connected to the main refrigerant line at the return point to guide refrigerant from the inverter to the main refrigerant line at the compressor fan.

9. The refrigeration equipment according to claim 8, comprising a controller configured to control the opening and closing of the bypass valve, wherein, The controller is configured to control the opening and closing of the inverter cooling valve.

10. The refrigeration apparatus according to any one of claims 7-9, wherein, The bypass valve is a regulating valve, and the controller is configured to control the bypass valve to control the flow rate of refrigerant through the bypass valve.

11. The refrigeration apparatus according to any one of claims 7-9, wherein, The compressor is a two-stage compressor including a first-stage compressor fan and a second-stage compressor fan, wherein the return point is located between the first-stage compressor fan and the second-stage compressor fan.

12. The refrigeration apparatus according to any one of claims 7-9, wherein, The controller is configured to control the opening and closing of the motor cooling valve.

13. A method of operating a refrigeration apparatus according to any one of the preceding claims, the method comprising: Determining whether there is insufficient refrigerant being delivered from the subcooler to the compressor includes: A first pressure parameter related to the pressure of the refrigerant in the main refrigerant line at the outlet of the subcooler is monitored. A second pressure parameter related to the pressure in the main refrigerant line at the return point upstream of the compressor fan; and Based on the first pressure parameter and the second pressure parameter, determine whether there is insufficient refrigerant being delivered to the compressor; and In response to a determination that there is insufficient refrigerant being delivered from the subcooler to the compressor, the bypass valve is controlled to increase the flow rate of refrigerant through the bypass valve.

14. The method according to claim 13, wherein, The second pressure parameter relates to the pressure in the main refrigerant line located at the return point between the first-stage compressor fan and the second-stage compressor fan of the two-stage compressor.

15. The method according to claim 13 or 14, wherein, Determining whether there is insufficient refrigerant being delivered to the compressor includes: Calculate the difference parameter related to the difference between the first pressure parameter and the second pressure parameter; Compare the difference parameter with a first threshold; and If the difference parameter is lower than the first threshold, it is determined that not enough refrigerant is delivered to the compressor.

16. The method according to any one of claims 13 to 14, wherein, The method further includes: determining whether excessive refrigerant is being supplied to the compressor; and in response to determining that excessive refrigerant is being supplied to the compressor, reducing the flow rate of refrigerant through the bypass valve.

17. The method according to claim 16, wherein, Determining whether excessive refrigerant is being supplied to the compressor includes: Calculate the difference parameter related to the difference between the first pressure parameter and the second pressure parameter; Compare the difference parameter with a second threshold; and If the difference parameter is higher than the second threshold, it is determined that too much refrigerant is being delivered to the compressor.

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