阅读说明：本技术 对向节能制冷循环中的压缩机中的制冷剂注入的控制 (Control of refrigerant injection into a compressor in an economized refrigeration cycle ) 是由 埃里克·维南迪 雷米·迪克斯 保罗·基亚拉蒙特 卢卡·马佐拉纳 于 2021-04-22 设计创作，主要内容包括：本发明涉及对向节能制冷循环中的压缩机中的制冷剂注入的控制。在制冷循环中执行控制向制冷循环中的压缩机中的注入的方法。制冷循环包括至少节能器热交换器、排热热交换器、第一膨胀设备和被配置用于压缩制冷剂的压缩机。压缩机包括用于压缩的装置、抽吸口、排放口和注入口,排放口经由排放管线连接至排热热交换器,注入口连接至用于压缩的装置。节能器热交换器包括：具有连接至排热热交换器的输入和连接至第一膨胀设备的输出的第一路径；以及具有经由节能器阀连接至排热热交换器的输入和经由注入管线连接至压缩机的注入口的输出的第二路径。该方法包括：使用基于节能器热交换器中的制冷剂的过热水平的第一操作模式来调节节能器阀。(The present invention relates to control of refrigerant injection into a compressor in an economized refrigeration cycle. A method of controlling injection into a compressor in a refrigeration cycle is performed in the refrigeration cycle. The refrigeration cycle includes at least an economizer heat exchanger, a heat rejection heat exchanger, a first expansion device, and a compressor configured to compress a refrigerant. The compressor comprises means for compression, a suction port, a discharge port connected to the heat rejecting heat exchanger via a discharge line, and an injection port connected to the means for compression. The economizer heat exchanger includes: a first path having an input connected to the heat rejection heat exchanger and an output connected to the first expansion device; and a second path having an input connected to the heat rejection heat exchanger via an economizer valve and an output connected to an injection port of the compressor via an injection line. The method comprises the following steps: the economizer valve is adjusted using a first mode of operation based on a superheat level of refrigerant in the economizer heat exchanger.)

1. A method of controlling injection into a compressor (2) in a refrigeration cycle (1), wherein the method is performed in a refrigeration cycle (1), the refrigeration cycle (1) comprising at least an economizer heat exchanger (11), a heat rejecting heat exchanger (3), a first expansion device (4) and a compressor (2) configured for compressing a refrigerant, wherein the compressor (2) comprises means for compressing, a suction port (2a), a discharge port (2b) and an injection port (2c), wherein the discharge port (2b) is connected to the heat rejecting heat exchanger (3) via a discharge line (14), and wherein the injection port (2c) is connected to the means for compressing, and wherein the economizer heat exchanger (11) comprises:

a first path (11a), the first path (11a) having an input connected to the heat rejecting heat exchanger (3) and an output connected to the first expansion device (4), and

a second path (11b), said second path (11b) having an input connected to said heat rejecting heat exchanger (3) via an economizer valve (13) and an output connected to said injection port (2c) of said compressor (2) via an injection line (12);

the method comprises the following steps:

adjusting (106) the economizer valve (13) by using a first mode of operation that is based on a superheat level of refrigerant in the economizer heat exchanger (11).

2. The method of claim 1, wherein:

the heat rejecting heat exchanger (3) is arranged downstream of the discharge outlet (2b) of the compressor (2);

the first expansion device (4) is arranged downstream of the heat rejecting heat exchanger (3) and upstream of the suction opening (2a) of the compressor (2).

3. The method of any preceding claim, wherein the first mode of operation comprises: setting the opening degree of the economizer valve (13) to a value calculated by using the first operation mode to maintain the superheat level of the refrigerant at the output of the second path (11b) of the economizer heat exchanger (11) in a predetermined range.

4. The method of any of the preceding claims, further comprising:

determining (102) a pressure of refrigerant in the injection line (12);

determining (104) a temperature of refrigerant in the discharge line (14); and is

Wherein the adjusting (106) comprises:

based on the determined pressure and the determined temperature, determining (108) whether to continue (110) adjusting (106) the economizer valve (13) based on a superheat level of refrigerant at an output of the economizer heat exchanger (11) or whether to perform one of:

adjusting (112) the economizer valve (13) by using a second mode of operation based at least on the temperature of refrigerant in the discharge line (14), or

Adjusting (114) the economizer valve (13) by using a third mode of operation based at least on the pressure of refrigerant in the injection line (12).

5. The method of claim 4, wherein the adjusting (106) comprises:

determining (108) whether to perform adjusting the economizer valve (13) by using any combination of the first, second, and third operating modes based on the determined pressure and the determined temperature.

6. The method according to any one of claims 4 or 5, wherein adjusting (112) the economizer valve (13) by using the second operating mode comprises: adjusting the economizer valve (12) to maintain the temperature of the refrigerant in the discharge line (14) below a first predetermined set point.

7. The method of any of claims 4 to 6, wherein adjusting (114) the economizer valve (13) by using the third operating mode comprises: adjusting the economizer valve (12) to maintain the pressure of the refrigerant in the injection line (12) below a second predetermined set point.

8. The method of any of claims 4 to 7, wherein the adjusting (106) further comprises:

closing (306) the economizer valve (13) if it is determined that the determined pressure of refrigerant in the injection line (12) is below a first threshold;

setting (310) an opening degree of the economizer valve (13) to a value calculated by using at least one of the first operation mode or the second operation mode if it is determined that the determined pressure of the refrigerant in the injection line (12) is higher than the first threshold value and lower than a second threshold value;

setting (314) the opening degree of the economizer valve (13) to a value calculated by using a combination of at least the first and third operation modes, if it is determined that the determined pressure of the refrigerant in the injection line (12) is higher than the second threshold value and lower than a third threshold value;

-setting (318) the opening degree of the economizer valve (13) to a value calculated by using at least the third operation mode, if it is determined that the determined pressure of the refrigerant in the injection line (12) is higher than the third threshold value and lower than a fourth threshold value;

closing (316) the economizer valve (13) and stopping operation of the compressor (2) if it is determined that the determined pressure of refrigerant in the injection line (12) is above the fourth threshold.

9. The method of claim 8, wherein setting (310) the opening degree of the economizer valve (13) to a value calculated by using at least the first or second operation mode comprises:

setting (406) the opening degree of the economizer valve (13) to a value calculated by using the first operation mode if the determined temperature of the refrigerant in the discharge line (14) is below a fifth threshold value, which comprises setting the opening degree of the economizer valve (13) to a value calculated from a superheat level of the refrigerant in the second path (11b) of the economizer heat exchanger (11);

setting (410) the opening degree of the economizer valve (13) to a value calculated from the superheat level of the refrigerant in the economizer heat exchanger (11) and the determined temperature of the refrigerant in the discharge line (14) if the determined temperature of the refrigerant in the discharge line (14) is higher than the fifth threshold and lower than a sixth threshold;

setting (414) the opening degree of the economizer valve (13) to a value calculated from the determined temperature of the refrigerant in the discharge line (14) if the determined temperature of the refrigerant in the discharge line (14) is higher than the sixth threshold and lower than a seventh threshold; and

closing (416) the economizer valve (13) and stopping operation of the compressor (2) if the determined temperature of the refrigerant in the discharge line (14) is above the seventh threshold.

10. The method according to any one of claims 8 or 9, wherein setting (314) the opening degree of the economizer valve (13) to a value calculated by using a combination of at least the first and third operating modes comprises:

setting (506) the opening degree of the economizer valve (13) to a value calculated from the determined pressure and superheat value of the refrigerant in the injection line (12) if the determined temperature of the refrigerant in the discharge line (14) is below an eighth threshold;

setting (510) the opening degree of the economizer valve (13) to a value calculated from the determined pressure of the refrigerant in the injection line (12), the determined temperature of the refrigerant in the discharge line (14) and the superheat value, if the determined temperature of the refrigerant in the discharge line (14) is higher than the eighth threshold and lower than a ninth threshold; and

closing (512) the economizer valve (13) and stopping operation of the compressor (2) if the determined temperature of the refrigerant in the discharge line (14) is above the ninth threshold.

11. The method of claim 10, wherein the eighth threshold is equal to the fifth threshold, and wherein the ninth threshold is equal to the seventh threshold.

12. The method according to any one of claims 8 to 11, wherein setting (318) the opening degree of the economizer valve (13) to a value calculated by using at least the third operation mode comprises:

setting (606) the opening degree of the economizer valve (13) to a value calculated from the determined pressure of the refrigerant at the economizer heat exchanger (11) if the determined temperature of the refrigerant in the discharge line (14) is below a tenth threshold;

setting (610) the opening degree of the economizer valve (13) to a value calculated from the determined pressure of the refrigerant at the economizer heat exchanger (11), the determined temperature of the refrigerant in the discharge line (14) and the superheat value, if the determined temperature of the refrigerant in the discharge line (14) is above the tenth threshold and below an eleventh threshold; and

closing (612) the economizer valve (13) and stopping operation of the compressor (2) if the determined temperature of the refrigerant in the discharge line (14) is above the eleventh threshold.

13. The method of claim 12, wherein the tenth threshold is equal to the fifth threshold, and wherein the eleventh threshold is equal to the seventh threshold.

14. A method of controlling injection into a compressor (2) in a refrigeration cycle (1), wherein the method is performed in a refrigeration cycle (1), the refrigeration cycle (1) comprising at least an economizer heat exchanger (11), a heat rejecting heat exchanger (3), a first expansion device (4) and a compressor (2) configured for compressing a refrigerant, wherein the compressor (2) comprises means for compressing, a suction port (2a), a discharge port (2b) and an injection port (2c), wherein the discharge port (2b) is connected to the heat rejecting heat exchanger (3) via a discharge line (14), and wherein the injection port (2c) is connected to the means for compressing, and wherein the economizer heat exchanger (11) comprises:

a first path (11a), the first path (11a) having an input connected to the heat rejecting heat exchanger (3) and an output connected to the first expansion device (4), and

a second path (11b), the second path (11b) having a path via an economizer valve (13)

An input connected to the heat rejecting heat exchanger (3) and an output connected to the injection port (2c) of the compressor (2) via an injection line (12);

the method comprises the following steps:

determining (202) a pressure of refrigerant in the injection line (12);

determining (204) a temperature of refrigerant in the discharge line (14); and

based on the determined pressure and the determined temperature, selecting (206) one of:

a first mode of operation for adjusting the economizer valve (13) based on a superheat level of refrigerant at an output of the second path (11b) of the economizer heat exchanger (11),

a second operating mode for adjusting the economizer valve (13) based on the temperature of the refrigerant in the discharge line (14), and

a third operating mode for adjusting the economizer valve (13) based on the pressure of refrigerant in the injection line (12);

adjusting (208) the economizer valve (13) by using the selected operating mode.

Technical Field

The present patent application relates to a method for controlling refrigerant injection into a compressor in a refrigeration cycle, wherein the refrigeration cycle includes an injection compressor and an economizer.

Background

Refrigeration systems having a refrigeration cycle are well known in the art. In a typical refrigeration cycle, a refrigerant is circulated through a refrigeration system, wherein the refrigerant undergoes changes in thermodynamic properties in different parts of the refrigeration system. The refrigerant is a fluid, i.e. a liquid or a vapour or a gas, respectively. An example of the refrigerant may be an artificial refrigerant, such as fluorocarbon. However, in recent applications, carbon dioxide CO, as a non-artificial refrigerant₂Has become increasingly important because carbon dioxide is not harmful to the environment. Changes in thermodynamic properties of the refrigerant may include, for example, changes in temperature, pressure, volume, or enthalpy, where a change in one property may also affect at least one other property at times, or where at least one property may remain unchanged as other properties change in some cases. The change in thermodynamic properties may be accompanied by a phase change of at least a portion of the refrigerant, such as a phase change from a liquid to a vapor, and vice versa.

Refrigerants are used in refrigeration systems to transfer heat in a refrigeration cycle. Therefore, it is generally easy to transfer heat from one point in the refrigeration cycle to another point in the refrigeration cycle by the refrigerant. These points in the refrigeration cycle may be represented by heat exchangers, for example. In the first heat exchanger, the refrigerant may receive heat from a source. The source may be, for example, the air of a room whose temperature should be controlled. After being transferred to the second heat exchanger, the refrigerant may discharge heat in the second heat exchanger, for example, by transferring heat to the exhaust gas.

Today, refrigeration systems are particularly important for controlling temperature or climate conditions. A particular type of refrigeration system is a compression refrigeration system, sometimes referred to as a Vapor Compression Refrigeration System (VCRS).

As used herein, a refrigeration cycle includes at least a compressor for compressing a refrigerant. The compressed refrigerant may drive a cycle. Furthermore, such refrigeration cycles typically include a heat exchanger in which heat may be extracted from the compressed refrigerant. Extracting heat from the compressed refrigerant is sometimes referred to as heat rejection because heat is rejected from the refrigeration system. Therefore, the heat exchanger is often referred to as a heat rejection heat exchanger. Furthermore, such refrigeration cycles typically include an expansion device in which the pressure and thus the temperature of the refrigerant is reduced. The expansion device may be, for example, a valve, in particular an expansion valve, or a metering device. Furthermore, such a refrigeration cycle typically includes another heat exchanger, which may be used to receive heat from the source. The other heat exchangers are commonly referred to as heat absorption heat exchangers. The heat absorption heat exchanger is in fluid communication with the compressor such that the refrigerant is directed to the compressor to close the cycle.

In some refrigeration cycles, a compressor is used to drive the refrigeration cycle. Such compressors generally comprise a suction and a discharge opening and means for compression. The suction port is configured to receive refrigerant from the refrigeration cycle. For example, the refrigerant may be received from a heat absorption heat exchanger. The suction port is in fluid communication with the compression chamber for at least a first instance of time to provide refrigerant to the means for compressing. In the device for compression, the refrigerant will be compressed to a desired pressure. Compression generally increases the pressure of the refrigerant. This may be accompanied by an increase in the temperature of the refrigerant. Where the compressor may be a scroll compressor, the means for compressing may be formed by a scroll group of scroll compressors.

The means for compressing is in fluid communication with a discharge port of the compressor for at least a second instance of time to provide compressed refrigerant to the discharge port. At the discharge, the compressed refrigerant may be discharged from the compressor at a desired discharge pressure or a desired discharge temperature.

In some refrigeration cycles, the compressor may be an injection compressor. In addition to the above-described features of the compressor, the injection compressor further includes an injection port. The injection port is in fluid communication with a source for providing a refrigerant. The source may be, for example, an economizer. Further, the injection port is in fluid communication with the means for compressing of the compressor for at least a third instance of time. Where the injection port is in fluid communication with the means for compressing, refrigerant is provided from a source to the means for compressing of the compressor. The refrigerant provided from the source to the means for compressing may be referred to as additional refrigerant, injected refrigerant, or fresh refrigerant. In most applications, the injected refrigerant is in a vapor state. However, in certain situations, such as where it is desirable to reduce the temperature of the refrigerant in the compressor, it may be beneficial to inject liquid refrigerant in addition to vapor refrigerant.

In general, the efficiency of a system, expressed in terms of the so-called coefficient of performance (COP), depends on the temperature or pressure difference between the temperature or pressure of the refrigerant in the heat rejecting heat exchanger and the refrigerant in the heat absorbing heat exchanger. However, injection conditions, such as pressure and temperature, have a direct impact on the efficiency of the system. Therefore, controlling the refrigerant system based solely on the temperature of the refrigerant in the heat rejecting heat exchanger may result in operational inefficiencies or fluctuations in the cooling provided by the refrigeration system. Accordingly, there is a need in the art to improve the efficiency of refrigeration systems.

Disclosure of Invention

This need is overcome by the method for controlling injection into a compressor of a refrigeration cycle according to the present invention.

Generally, the present invention relates to a method for controlling injection into a compressor of a refrigeration cycle based on an superheat level of a refrigerant in an economizer. The method may include different modes of operation. In some embodiments of the invention, one of these modes of operation may establish a default mode of operation for the method according to the invention, while the other mode of operation may be used under certain system conditions. In this case, the method according to the invention provides a method of switching between suitable operating modes. Alternatively, in other embodiments of the invention, the method does not establish a default mode, but may select an appropriate operating mode from a plurality of reasonable operating modes based on the determined system parameters.

The method of controlling injection into a compressor in a refrigeration cycle according to the present invention is performed in the refrigeration cycle, the refrigeration cycle comprising at least an economizer valve, a heat rejecting heat exchanger, a first expansion device, and a compressor configured to compress a refrigerant. The compressor includes a device for compression, a suction port, a discharge port, and an injection port. The heat rejection heat exchanger may be disposed downstream of a discharge of the compressor. The connection between the discharge and the heat rejecting heat exchanger may be referred to as a discharge line. The first expansion device may be disposed downstream of the heat rejection heat exchanger and upstream of a suction of the compressor. Further, the refrigeration cycle may include a heat absorption heat exchanger disposed downstream of the first expansion device and upstream of the suction port of the compressor.

The injection port is connected to the means for compressing for at least a specific instance of time. The means for compressing is configured to receive refrigerant from a suction port and/or an injection port of the compressor. Further, the means for compressing compresses the refrigerant. Further, the means for compressing may be configured to provide compressed refrigerant to a discharge port of the compressor.

In a preferred embodiment, the compressor may be a scroll compressor and the means for compressing may be formed by a scroll group of scroll compressors.

The economizer includes an economizer heat exchanger including a first path and a second path for exchanging heat between refrigerant in the first path and refrigerant in the second path. The first path has an input connected to the heat rejection heat exchanger and an output connected to the first expansion device. The second path has an input connected to the heat rejection heat exchanger via an economizer valve and an output connected to an injection port of the compressor via an injection line. Preferably, the first and second paths of the economizer have opposite flow directions. However, other flows are possible in which the first path and the second path have opposite flow directions. For example, it is also possible that the first path and the second path are oriented in a parallel flow direction or in a cross flow direction, wherein the orientation of the flow in the first path is perpendicular to the orientation of the flow in the second path. Furthermore, any combination of the mentioned flow types is possible. Since the present invention relates to the control of refrigerant in a refrigerant cycle of a refrigerant system, the term "connection" is used throughout this application to describe a connection via which fluid communication is achieved. In other words, the connection enables the exchange of refrigerant between the connected entities.

According to the invention, the method comprises: the economizer valve is adjusted by using a first mode of operation that is based on a superheat level of refrigerant in the economizer heat exchanger. The method may also include determining a superheat level of the refrigerant in the economizer heat exchanger. For example, the superheat level may be determined at an output of the second path of the heat rejection heat exchanger.

The adjusting may include calculating an opening degree of the economizer valve based on a superheat level of the refrigerant in the economizer heat exchanger, and setting the opening degree to the calculated value. Throughout this application, any reference to calculating the opening degree may also include setting the opening degree to the calculated value.

The first mode of operation may be referred to as an overcontrol mode. This mode of operation is based on the following findings: the maximum refrigeration cycle efficiency is reached with minimal superheat at the economizer. The superheat can be measured as the temperature increase compared to the boiling point. For example, a superheat value of 5 kelvin would refer to a 5 kelvin increase in temperature compared to the saturation point. The saturation point may also be referred to as the boiling point. The desired superheat value depends on the refrigerant used. In the typical CO₂In the refrigeration cycle, the value of 5 kelvin is the target value for superheat in the economizer, as lower values may lead to instability or may lead to droplet injection into the compressor, which will reduce cycle efficiency. Other preferred refrigerants having the same target superheat value of 5 kelvin are R717 (ammonia), R290 (propane) and R32.

The superheat level (SH) may be calculated based on a temperature measured at an output of the second path of the economizer and a saturation temperature measured downstream of the economizer valve.The saturation temperature, which may also be referred to as the boiling temperature, may be measured directly or indirectly. An example of a direct temperature measurement is measuring the temperature between the economizer valve and the inlet of the second path of the economizer. An example of indirect temperature measurement is measuring the pressure at the location and determining the temperature from the pressure. Using the temperature values, T may be represented by SH ═ T_{An outlet}–T_{Saturation of}To calculate the superheat level, where T_{An outlet}Is the temperature measured at the outlet of the second path of the economizer, and T_{Saturation of}Is the saturation temperature.

The first mode of operation may be referred to as a superheat control mode, and may include setting the opening of the economizer valve to a value calculated using the first mode of operation to maintain a superheat level of refrigerant at an output of the second path of the economizer heat exchanger at a first predetermined set point. The predetermined set point may be set by the manufacturer or an operator of the corresponding refrigeration system. In some embodiments, the calculated value of the opening degree may be a pre-calculated value. Further, the pre-calculated value may be updated by a feedback controller, such as a PID controller.

In a preferred embodiment, different operating modes may be used to control the economizer valve. For example, the first mode of operation, which may be referred to as an over-thermal control mode, may be a default mode of operation in which injection control is controlled. At least two additional modes of operation may be provided. Of these two additional operating modes, there may be a second operating mode, which may be referred to as a Drain Line Temperature (DLT) control mode, and a third operating mode, which may be referred to as an economizer heat exchanger pressure (EHXP) control mode or a charging pressure control mode.

In accordance with at least some embodiments of the present invention, a system parameter may be determined and a switch may be made from the first mode of operation to either of the second mode of operation and the third mode of operation based on the determined system parameter. Those skilled in the art will appreciate that it is also possible to switch from any of the second mode of operation and the third mode of operation back to the first mode of operation based on the determined system parameter. In addition, it is possible to switch directly from the second operating mode to the third operating mode and vice versa. Thus, the determination of system parameters may allow any switching between operating modes. The system parameters may include any temperature or pressure of the refrigerant in the refrigeration cycle and the superheat level. Preferably, the superheat level of the refrigerant at the output of the second path of the economizer heat exchanger, the pressure of the refrigerant in the injection line and the temperature of the refrigerant discharged from the compressor are used. In most applications, the pressure of the refrigerant in the second path of the economizer and the pressure of the refrigerant in the injection line are substantially the same. For purposes of this application, these system parameters may be used interchangeably.

The second mode of operation may be referred to as a discharge line temperature control mode. The purpose of the second mode of operation is to prevent the temperature of the refrigerant in the compressor from exceeding a threshold value, which would be detrimental to the refrigeration system. This may be performed by injecting vapor refrigerant in addition to liquid refrigerant. Since liquid injection may lead to a malfunction of the compressor, it is desirable to keep the liquid injection as low as possible.

In a preferred embodiment, the method may further comprise the step of determining the pressure of the refrigerant in the injection line and determining the temperature of the refrigerant in the discharge line. The pressure of the refrigerant in the injection line and the temperature of the refrigerant in the discharge line may be examples of system parameters, the determination of which may enable switching between operating modes.

Based on the determined pressure and the determined temperature, it may be determined whether to continue adjusting the economizer valve using the first mode of operation, or whether to perform one of: the economizer valve is adjusted by using the second mode of operation or by using the third mode of operation. Thus, adjusting the economizer valve by using the second mode of operation is based on the temperature of the refrigerant in the discharge line, and adjusting the economizer valve by using the third mode of operation is based on the pressure of the refrigerant in the injection line.

The second mode of operation, which may be referred to as a DLT control mode, may include adjusting the economizer valve to maintain the temperature of the refrigerant in the discharge line below a second predetermined set point. The second predetermined set point may be set by the manufacturer or an operator of the respective refrigeration system. Such predetermined set points may be updated by a feedback controller, such as a PID controller.

The third mode of operation may be referred to as an injection pressure control mode. This mode may be used in situations where the discharge temperature of the refrigerant at the compressor is under control but the compressor internal pressure is elevated. Therefore, the economizer valve needs to be closed to a higher degree than would be required to achieve the superheat target would be desired. It is necessary to limit the injection of refrigerant into the compressor and thereby reduce the pressure inside the compressor.

The third mode of operation, which may be referred to as an EHXP mode of operation, may include adjusting an economizer valve to maintain a pressure of refrigerant in the injection line below a third predetermined set point. The third predetermined set point may be set by the manufacturer or an operator of the respective refrigeration system. Such predetermined set points may be updated by a feedback controller, such as a PID controller.

In some preferred embodiments, the above adjustment may be performed based on a combination of two or more of the first, second, and third modes of operation.

In a preferred embodiment, if it is determined that the pressure of the refrigerant in the injection line is below the first threshold, the adjusting may include closing an economizer valve. The first threshold may be referred to as a minimum injection pressure for injection into the compressor at the economizer. The minimum injection pressure may depend on the operating conditions of the compressor. Additionally, the minimum injection pressure may correspond to a set point predetermined by a manufacturer or operator of the refrigeration system.

If the pressure of the refrigerant in the injection line is below the minimum injection pressure, it is necessary to close the economizer valve and thereby prevent the refrigerant from being injected into the compressor. Otherwise, at the point where the refrigerant should be injected into the device for compression, the pressure in the injection line may be lower than the pressure in the device for compression. This may therefore result in an undesirable reverse flow of refrigerant from the compressor through the injection line.

Further, the adjusting may include: if it is determined that the pressure of the refrigerant in the injection line is above the first threshold and below the second threshold, the opening of the economizer valve is set to a value calculated using the first operating mode, the second operating mode, or a combination of both. The second threshold may be referred to as a maximum injection pressure at the economizer for the first and second modes of operation.

Further, the adjusting may include: if it is determined that the pressure of the refrigerant in the injection line is above the second threshold and below a third threshold, the opening degree of the economizer valve is set to a value calculated by using a combination of at least the first operating mode and the third operating mode.

Further, the adjusting may include: if it is determined that the pressure of the refrigerant in the injection line is higher than the third threshold and lower than the fourth threshold, the opening degree of the economizer valve is set to a value calculated by using the third operation mode, and if it is determined that the pressure of the refrigerant in the injection line is higher than the fourth threshold, the economizer valve is closed and the operation of the compressor is stopped. The fourth threshold may be referred to as a maximum injection pressure. Since an excessively high injection pressure may impair the operation of the compressor or the compressor itself, the fourth threshold value may correspond to a safety condition preventing the pressure inside the compressor from rising above the fourth threshold value.

In yet another preferred embodiment, setting the economizer valve to a value calculated by using the first or second operating mode may comprise, if the determined pressure of the refrigerant in the discharge line is above the first threshold but below the second threshold: if the temperature of the refrigerant in the discharge line is below a fifth threshold, the opening of the economizer valve is set to a value calculated from the superheat level of the refrigerant in the economizer heat exchanger. The fifth threshold may be referred to as a discharge temperature threshold for achieving superheat and temperature control. Below the fifth threshold, only the superheat value of the refrigerant is used to calculate the opening of the economizer valve in case the pressure of the refrigerant in the injection line is below the second threshold. The purpose of this operation is to optimize the superheat value by achieving a superheat target value.

Further, setting the opening degree of the economizer valve may include: if the temperature of the refrigerant in the discharge line is above the fifth threshold and below the sixth threshold, the opening of the economizer valve is set to a value calculated from the superheat level of the refrigerant in the economizer heat exchanger and the determined temperature of the refrigerant discharged from the compressor. The sixth threshold may be referred to as an alarm discharge line temperature threshold. The fifth threshold and the sixth threshold define a transition region in which a combination of the first operation mode and the second operation mode is performed.

Further, setting the opening degree of the economizer valve may include: if the temperature of the refrigerant in the discharge line is higher than the sixth threshold value and lower than the seventh threshold value, the opening degree of the economizer valve is set to a value calculated from the determined temperature of the refrigerant discharged from the compressor. Additionally, setting the opening of the economizer valve may include: if it is determined that the temperature of the refrigerant in the discharge line is above the seventh threshold, the economizer valve is closed and operation of the compressor is stopped. The seventh threshold may be referred to as a maximum discharge line temperature threshold. The threshold may define a temperature point above which injection of refrigerant into the compressor would be detrimental to the compressor. Thus, if the discharge line temperature exceeds the seventh threshold, the economizer valve is closed and injection is stopped. Preferably, the operation of the compressor is also stopped.

In still another preferred embodiment, if the determined pressure of the refrigerant in the discharge line is higher than the second threshold but lower than the third threshold, setting the opening degree of the economizer valve to a value calculated by using the third operation may include: if the determined temperature of the refrigerant in the discharge line is lower than the eighth threshold value, the opening degree of the economizer valve is set to a value calculated from the determined pressure and the superheat value of the refrigerant in the injection line. Thus, a combination of the first operation mode and the third operation mode is performed.

Further, setting the opening degree of the economizer valve may include: if the determined temperature of the refrigerant in the discharge line is higher than the eighth threshold value and lower than the ninth threshold value, the opening degree of the economizer valve is set to a value calculated from the determined pressure of the refrigerant in the injection line, the determined temperature of the refrigerant discharged from the compressor, and the superheat value. Thus, a combination of all three modes of operation may be performed.

Further, setting the opening degree of the economizer valve may include: if the determined temperature of the refrigerant in the discharge line is above the ninth threshold, the economizer valve is closed and operation of the compressor is stopped.

In at least some embodiments, the eighth threshold may be equal to the fifth threshold. Likewise, the ninth threshold may be equal to the seventh threshold.

In another preferred embodiment, setting the opening degree of the economizer valve to a value calculated by using at least the third operation mode may comprise, if the determined pressure of the refrigerant in the discharge line is higher than the third threshold value but lower than the fourth threshold value: if the determined temperature of the refrigerant in the discharge line is below a tenth threshold, the opening of the economizer valve is set to a value calculated from the determined pressure of the refrigerant at the economizer heat exchanger.

Further, setting the opening degree of the economizer valve may include: if the determined temperature of the refrigerant in the discharge line is above the tenth threshold and below the eleventh threshold, the opening of the economizer valve is set to a value calculated from the determined pressure of the refrigerant at the economizer heat exchanger, the determined temperature of the refrigerant in the discharge line, and the superheat value.

Additionally, setting the opening of the economizer valve may include: if the determined temperature of the refrigerant in the discharge line is above the eleventh threshold, the economizer valve is closed and operation of the compressor is stopped.

In at least some embodiments, the tenth threshold may be equal to the fifth threshold. In addition, the eleventh threshold value may be equal to the seventh threshold value.

In an alternative embodiment of the invention, the method for controlling injection into the compressor may not use a default operating mode, but may instead determine system parameters and determine an appropriate control operating mode based on the determined system parameters.

According to the invention, an alternative method of controlling injection into a compressor in a refrigeration cycle according to the invention is performed in the refrigeration cycle, the refrigeration cycle comprising at least an economizer, a heat rejecting heat exchanger, a first expansion device and a compressor configured for compressing a refrigerant. The compressor includes a device for compression, a suction port, a discharge port, and an injection port. The heat rejection heat exchanger may be disposed downstream of a discharge of the compressor. The connection between the discharge and the heat rejecting heat exchanger may be referred to as a discharge line. The first expansion device may be disposed downstream of the heat rejection heat exchanger and upstream of a suction of the compressor. Further, the refrigeration cycle may include a heat absorption heat exchanger disposed downstream of the first expansion device and upstream of the suction port of the compressor.

The injection port is connected to the means for compressing for at least a specific instance of time. The means for compressing is configured to receive refrigerant from a suction port and/or an injection port of the compressor. Further, the means for compressing compresses the refrigerant. Further, the means for compressing may be configured to provide compressed refrigerant to a discharge port of the compressor.

In a preferred embodiment, the compressor may be a scroll compressor and the means for compressing may be formed by a scroll group of scroll compressors.

The economizer includes an economizer heat exchanger including a first path and a second path for exchanging heat between refrigerant in the first path and refrigerant in the second path. The first path has an input connected to the heat rejection heat exchanger and an output connected to the first expansion device. The second path has an input connected to the heat rejection heat exchanger via an economizer valve and an output connected to an injection port of the compressor via an injection line. Since the present invention relates to the control of refrigerant in a refrigeration cycle of a refrigerant system, the term "connection" is used throughout the application to describe a connection via which fluid communication is achieved. In other words, the connection enables the exchange of refrigerant between the connected entities.

According to the invention, the method comprises: the pressure of the refrigerant in the injection line is determined and the temperature of the refrigerant discharged from the discharge port of the compressor is determined. The determination may be performed by one or more sensors.

Further, the method comprises: based on the determined pressure and the determined temperature, selecting one of: a first mode of operation for adjusting an economizer valve based on a superheat level of refrigerant in the economizer heat exchanger; a second mode of operation for adjusting the economizer valve based on the temperature of the refrigerant in the injection line; and a third mode of operation for calculating the economizer valve based on the pressure of the refrigerant in the injection line. In addition, the method comprises: the economizer valve is adjusted by using the selected operating mode.

The threshold values described throughout this application may be, in at least some embodiments, independent of the operating conditions of the refrigeration system. However, in other embodiments, at least one of the thresholds may depend on the operating conditions of the refrigeration system. For example, the third threshold may depend on at least one of a pressure of the refrigerant in the heat rejecting heat exchanger, a pressure of the refrigerant in the heat absorbing heat exchanger, or an ambient temperature. In this case, the controller performing the method according to the present invention may comprise logic for adaptively adjusting the third threshold value based on the operating conditions of the refrigeration system. Since the third threshold may be the maximum injection pressure, the dependence of the third threshold on the operating conditions of the refrigeration system may improve the flexibility of the control, may result in a higher COP and an increased reliability of the compressor, and may also protect the compressor from faults.

Drawings

The following description and the annexed drawings set forth in detail certain illustrative aspects of the system. These aspects are indicative, however, of but a few of the various ways in which the principles of various embodiments may be employed and the described embodiments are intended to include all such aspects and their equivalents.

In the drawings, like reference numerals generally refer to like parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.

In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:

FIG. 1 shows a schematic diagram of an exemplary refrigeration system control for refrigerant injection into a compressor in an economized refrigeration cycle;

fig. 2 shows a diagram of the effect of refrigerant injection on the optimum heat rejection heat exchanger pressure.

FIG. 3 shows a graph of discharge temperature versus injection pressure for an exemplary embodiment of the invention;

FIGS. 4a, 4b show block diagrams of inputs and outputs as controllers that may be used in connection with the present invention;

FIG. 5 shows a flow chart of a method of controlling injection into a compressor according to an embodiment of the invention;

FIG. 6 shows a flow chart of an alternative method of controlling injection into a compressor according to another embodiment of the present invention;

FIG. 7 illustrates a decision diagram of a preferred embodiment of a method of controlling injection into a compressor, wherein the decision diagram relates to adjusting an amount of injection into the compressor;

FIG. 8 shows a decision diagram illustrating step 310 of FIG. 7 in further detail;

FIG. 9 shows a decision diagram illustrating step 314 of FIG. 7 in further detail; and

fig. 10 shows a decision diagram illustrating step 318 of fig. 7 in further detail.

Detailed Description

The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced.

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

Fig. 1 shows a schematic diagram of a refrigeration system 1, the refrigeration system 1 being used for economizer-based control of refrigerant injection into a compressor 2 of the refrigeration system 1. The refrigeration system 1 comprises a compressor 2, the compressor 2 comprising a suction port 2a, a discharge port 2b and an injection port 2c, a heat rejecting heat exchanger 3 downstream of the compressor 2, a first expansion device 4 downstream of the heat rejecting heat exchanger 3, and a heat absorbing heat exchanger 7 downstream of the first expansion device 4 and upstream of the compressor 2.

Furthermore, the refrigeration system 1 comprises a second expansion device 6 and a flash (flash) tank 5. A flash tank 5 and a second expansion device 6 are disposed between the first expansion device 4 and the heat absorption heat exchanger 7. In detail, the flash tank 5 is arranged downstream of the first expansion device 4 and upstream of the second expansion device 6, the second expansion device 6 being arranged upstream of the heat absorption heat exchanger 7. Thus, the pressure and temperature of the refrigerant can be reduced.

In the refrigeration system 1 depicted in fig. 1, the flash tank 5 comprises two separate chambers 5a, 5 b. However, it is also possible for the flash tank to separate liquid refrigerant and vapor refrigerant in the same volume.

The two separation chambers 5a, 5b comprise a chamber 5a for collecting vapour or flash gas and a chamber 5b for collecting liquid. The liquid collection chamber 5b comprises at least one outlet. The connection between the flash tank 5 and the second expansion device 6 is established via at least one of the at least one outlet of the liquid collection chamber 5b of the flash tank 5.

The vapor collection chamber 5a of the flash tank 5 comprises at least one outlet. At least one outlet of the vapor collection chamber 5a is connected to a suction port of the compressor 2 via a bypass path 8 and a bypass valve 9.

Although a flash tank 5 and a bypass line 8 are depicted in fig. 1, those skilled in the art will appreciate that a flash tank 5 is not necessary for the refrigeration system. In at least some embodiments, no flash tank or a flash tank 5 without a bypass line is used.

The refrigeration system 1 includes an economizer heat exchanger 11. The economizer heat exchanger comprises two paths, a first path 11a and a second path 11b, the first path 11a being connected to the heat rejecting heat exchanger 3 and the first expansion device 4, the second path 11b being connected to the heat rejecting heat exchanger 3 via an economizer valve 13 and to the injection port 2c of the compressor 2 via an injection line 12. In the example depicted in fig. 1, the first and second paths of the economizer have counter-flow directions.

In the economizer heat exchanger 11 depicted in fig. 1, the first path 11a and the second path 11b are close to each other so that heat exchange can be performed between the two paths. Since the refrigerant in the second path 11b is expanded by the economizer valve 13, the refrigerant in the second path 11b has a lower temperature than the refrigerant in the first path 11 a. Therefore, heat is exchanged from the refrigerant of the first path 11a to the refrigerant of the second path 11 b. This process is a supercooling process that reduces the heat amount of the refrigerant in the first path 11a, and thus the temperature of the refrigerant in the first path 11a can also be reduced.

Furthermore, the refrigeration system 1 comprises a controller 10, the controller 10 being adapted to regulate at least the economizer valve 13. Additionally, the controller 10 may also be used to control any of the first expansion device 4, the flash tank 5, the second expansion device 6, the bypass valve 9, and the compressor 2. The operation of the controller 10 is based on the superheat level of the refrigerant in the economizer heat exchanger 11. In addition, the controller 10 may also use system parameters, such as the pressure of the refrigerant in the injection line 12 or the temperature of the refrigerant discharged from the compressor 2.

Fig. 1 readily indicates the connections for exchanging control signals by means of dashed lines. Although fig. 1 shows dashed lines between the controller 10 and the economizer valve 13, the first expansion device 4, the second expansion device 6, the compressor 2, and the flash tank 5, those skilled in the art will appreciate that these dashed lines are shown for illustration purposes only. The controller 10 may be connected to any subset of the aforementioned components of the refrigeration cycle. With respect to the connection between the controller 10 and the flash tank 5, it should be noted that the controller 10 may be connected to a sensor within the flash tank 5, wherein the sensor may be a pressure sensor. Further, in some examples, multiple controllers may be employed in a refrigeration system. Each of these multiple controllers may control any subset of the expansion device, compressor, and flash tank, as previously described with respect to controller 10.

FIG. 2 illustrates a refrigerant injection versus optimal heat rejection heat exchangerGraph of the effect of pressure. In detail, fig. 2 depicts a pressure (p) dependent on the refrigerant in the heat rejecting heat exchanger_c) Coefficient of performance (COP). Thus, the solid line 50 represents the curve for the COP of a refrigeration system with a closed injection valve (i.e. without injection of refrigerant into the means for compression of the compressor).

The dashed line 55 represents an exemplary curve for the COP of the same refrigeration system with an at least partially open injection valve (i.e. with refrigerant injection into the means for compression of the compressor). The difference between the curves is shown for illustrative purposes.

In a refrigeration system, to achieve a higher COP, the operating conditions are controlled. Without refrigerant injection, the COP depends on the temperature of the refrigerant in the heat rejecting heat exchanger. However, the injection of refrigerant has a direct impact on the efficiency of the system. This influence depends on the injection conditions, such as the pressure of the injected refrigerant or the temperature of the injected refrigerant. It can be seen that the implantation not only improves the overall COP. The injection also shifts the maximum value of the COP to the lower pressure of the refrigerant in the heat rejecting heat exchanger. The maximum of each curve represents the optimum heat rejection heat exchanger pressure. This optimum pressure is lower when refrigerant injection into the compressor is used.

Fig. 3 shows a graph of discharge temperature versus injection pressure for an exemplary embodiment of the invention. The pressure p corresponds to the pressure at which the refrigerant is injected into the injection port of the compressor. This pressure may be measured in the second path of the economizer or in the injection line and may be referred to as the injection pressure. The temperature T corresponds to a temperature of refrigerant discharged from a discharge port of the compressor. This temperature may be measured at the discharge or in the connection line between the discharge and the heat rejecting heat exchanger and may be referred to as the discharge line temperature DLT.

In the temperature-pressure diagram, different zones 70, 71, 72, 73, 74, 75 are depicted. These regions are based on specific pressure and temperature thresholds and indicate pressure and temperature ranges for each of the three operating modes or combinations thereof.

In situ pouringInlet pressure p₀Hereinafter, injection into the compressor is not performed. In this case, the injection pressure may be too low for effective injection. Conversely, the pressure may be so low that refrigerant from the injection line will not be injected into the compressor, but an undesirable reverse flow from the compressor through the discharge line may occur. P₀May be referred to as the minimum pressure for injection.

In addition, for p is higher than_maxThe injection is not performed at the pressure of (c). If the pressure will exceed p_maxThe refrigerant will be injected at such a high pressure that the compressor may be damaged or the efficiency of the refrigeration cycle will be reduced. Similarly, for exceeding the maximum temperature value T_maxWill not perform an implant.

At pressure level p₀And p_maxIn between, the injection is performed based on three operation modes or a combination thereof. Thus, the first operation mode is denoted as an overheating control mode. For slave p₀Up to p₁Pressure range and below T₁The first operating mode is performed. The corresponding region in the temperature-pressure diagram is region 70.

The second mode of operation is represented as the discharge line temperature control mode, and for slave p₀Up to p₁Pressure range and T₂And T_maxThe second operating mode is performed at a temperature range therebetween. The corresponding region in the temperature-pressure diagram is region 72.

At 71, for p₀To p₁And T₁To T₂A combination of the overheating control mode and the exhaust line temperature control mode is performed.

The third operating mode is denoted injection pressure control mode and for slave p₂Up to p_maxPressure range and below T₁The third operating mode is performed. The corresponding region in the temperature-pressure diagram is region 74.

At 73, for p₁To p₂And is lower than T₁The over thermal control mode and the injection pressure control mode are performed in combination.

Furthermore, for values higher than T₁Discharge line temperature and p₁And p_maxWith the injection pressure in between, a combination of all three modes of operation is performed in region 75.

Those skilled in the art will appreciate that the pressure level p_iAnd temperature level T_iFor illustrative purposes. The particular values of these stages depend on the system to which the control operations are applied.

Fig. 4a, 4b show block diagrams of inputs and outputs as controllers that may be used in connection with the present invention.

In fig. 4a, the controller, represented by block "CTRL", receives as input the superheat value of the refrigerant in the second path of the economizer, and controls at least the economizer valve, which is represented as an economizer heat exchanger valve "EHXV". In addition, the controller may also control the operation of the compressor CMP. In fig. 4a, the output arrow of the compressor CMP is shown as a dashed line to illustrate that the controller may perform the economizer valve control, or both the economizer valve control and the compressor control.

In fig. 4b, the controller receives as input the superheat value and controls the economizer valve and optionally the compressor. Further, the controller receives as additional inputs the pressure of the refrigerant in the injection line (denoted as economizer heat exchanger pressure "EHXP") and the temperature of the refrigerant in the discharge line (denoted as discharge line temperature "DLT").

Fig. 5 shows a flow chart of a method 100 of controlling injection into a compressor according to an embodiment of the invention. The method 100 may be performed by a controller in a refrigeration cycle, for example, the controller 10 as depicted in fig. 1. Throughout the flow chart, solid lines indicate steps essential to the invention, whereas dashed lines indicate steps performed in a preferred embodiment of the invention.

The method 100 includes the step of determining 102 a pressure of the refrigerant in the injection line 12. Determining the pressure of the refrigerant in the injection line may include determining the pressure in any portion of the injection line 12, the second path of the economizer heat exchanger 11b, or the pressure at the outlet of the second path of the economizer heat exchanger 11 b.

Further, the method 100 includes the step of determining 104 a temperature of the refrigerant in the discharge line 14. Since the temperatures of the discharge port 2b and the discharge line 14 are similar, determining the temperature of the refrigerant at the discharge port 2b of the compressor 2 may also be performed by measuring the temperature of the refrigerant in the discharge line 14.

In addition, the method comprises: the economizer valve 13 is adjusted 106 using the first mode of operation. The first mode of operation may correspond to an over-temperature control mode. Adjusting 106 the economizer valve 13 can include determining 108 whether to continue adjusting the economizer valve using the first operating mode or whether to perform one of the second operating mode and the third operating mode. Thus, the first mode of operation may establish a default operation of the controller. The second mode of operation may correspond to a discharge line temperature control mode and the third mode of operation may correspond to an injection pressure control mode.

Based on the determination 108, the method 100 may include: continuing 110 adjusts 106 the economizer valve by using the first operating mode, or adjusts 112 the economizer valve by using the second operating mode, or adjusts 114 the economizer valve by using the third operating mode.

Fig. 6 shows a flow chart of a method 200 of controlling injection into a compressor according to an alternative embodiment of the present invention. Method 200 may be performed by a controller in a refrigeration cycle, for example, controller 10 as depicted in fig. 1.

The method 200 includes the step of determining 202 a pressure of the refrigerant in the injection line 12. Determining the pressure of the refrigerant in the injection line may include determining the pressure in any portion of the injection line 12, the second path of the economizer heat exchanger 11b, or the pressure at the outlet of the second path of the economizer heat exchanger 11 b.

Further, the method 200 includes the step of determining 204 a temperature of the refrigerant in the discharge line 14. Since the temperature of the refrigerant at the discharge port 2b and in the discharge line 14 is similar, determining the temperature of the refrigerant at the discharge port of the compressor 2 can also be performed by measuring the temperature of the refrigerant in the discharge line 14.

In addition, the method 200 includes the step of selecting 206 one of a first mode of operation, a second mode of operation, and a third mode of operation. Thus, the first operating mode may correspond to a superheat control mode, the second operating mode may correspond to a drain line temperature control mode, and the third operating mode may correspond to an injection pressure control mode.

Further, the method 200 includes adjusting 208 the economizer valve 13 by using the selected operating mode.

Fig. 7 shows a decision diagram 300 of a preferred embodiment of a method of controlling injection into a compressor, wherein the decision diagram 300 relates to adjusting the amount of injection into the compressor. The amount of injection into the compressor is controlled by adjusting a so-called economizer valve or economizer heat exchanger valve called EHXV (see reference numeral 13 in fig. 1). The decision may be performed by a controller, such as controller 10.

The method begins at step 302, where a determined pressure of refrigerant in an injection line is received at step 302. In fig. 7, the pressure of the refrigerant in the injection line is referred to as p.

At step 304, it is determined whether the injection pressure p is below a first threshold. In the event that the pressure is less than the first threshold, the method continues at step 306, where the economizer valve EHXV is closed in step 306. Otherwise, the method continues at step 308.

At step 308, it is determined whether the injection pressure p is greater than or equal to a first threshold and less than a second threshold. In the event that the injection pressure is greater than or equal to the first threshold and less than the second threshold, the method continues at step 310, where the economizer valve EHXV is opened in step 310. Here, the opening degree of the economizer valve EHXV is calculated according to at least one of the superheat value SH of the refrigerant in the economizer heat exchanger or the temperature DLT of the refrigerant in the discharge line. As will be described in more detail with respect to fig. 8, the opening may be calculated based on the superheat value, the discharge line temperature, or a combination of both, depending on the value of the discharge line temperature. In the event that the injection pressure is not greater than or equal to the first threshold and less than the second threshold, the method continues at step 312.

At step 312, it is determined whether the injection pressure p is greater than or equal to the second threshold and less than a third threshold. In the event that the injection pressure is greater than or equal to the second threshold and less than the third threshold, the method continues at step 314, where in step 314, the economizer valve EHXV is opened. Here, the opening degree of the economizer valve EHXV is calculated from at least the superheat value SH, the injection pressure P. As will be described in more detail with respect to fig. 9, the opening may be calculated based on the injection pressure, the discharge line temperature, or a combination of both, depending on the value of the discharge line temperature. In addition, it is also possible to consider the superheat value for calculation. In the event that the injection pressure is not greater than or equal to the second threshold and less than the third threshold, the method continues at step 316.

At step 316, it is determined whether the injection pressure p is greater than or equal to the third threshold and less than the fourth threshold. In the event that the injection pressure is greater than or equal to the third threshold and less than the fourth threshold, the method continues at step 318, where the economizer valve EHXV is opened at step 318. Here, the opening degree of the economizer valve EHXV is calculated from at least the injection pressure P. As will be described in more detail with respect to fig. 10, the discharge line temperature or superheat value may also be considered for the calculation of the opening degree, depending on the value of the discharge line temperature. In the event that the injection pressure is not greater than or equal to the third threshold and less than the fourth threshold, the method continues at step 320, where the economizer valve EHXV is closed and the compressor is shut down in step 320.

In the event that the method reaches any of steps 306, 310, 314, 318, or 320, the method may continue again at step 302 by determining or receiving the injection pressure p. In this case, the method may determine or receive an updated value for the injection pressure p.

Fig. 8 shows a decision diagram describing in more detail a method 400 for determining the opening of the economizer valve EHXV based on step 310 of the decision diagram of fig. 7.

After step 310, the method 400 receives the determined value for the temperature of the refrigerant in the discharge line at step 402.

At step 404, it is determined whether the discharge line temperature DLT is below a fifth threshold. In the event that the temperature is less than the fifth threshold, the method continues at step 406, where the opening of the economizer valve EHXV is calculated based on the superheat level of the refrigerant in the economizer in step 406. This refers to the first mode of operation, also referred to as the overheating control mode. Referring to FIG. 3, step 406 may refer to operations performed with respect to the pressure and temperature located in region 70. Otherwise, the method continues at step 408.

At step 408, it is determined whether the discharge line temperature DLT is greater than or equal to the fifth threshold and less than the sixth threshold. In the event that the temperature is greater than or equal to the fifth threshold and less than the sixth threshold, the method continues at step 410, where the opening of the economizer valve is calculated based on the superheat level of the refrigerant in the economizer and the temperature DLT of the refrigerant in the discharge line at step 410. Thus, a combination of superheat control and vent line control modes may be performed. Referring to fig. 3, step 410 may refer to operations performed with respect to the pressure and temperature located in region 71. In the event that the discharge line temperature is not greater than or equal to the fifth threshold and less than the sixth threshold, the method continues at step 412.

At step 412, it is determined whether the discharge line temperature DLT is greater than or equal to the sixth threshold and less than the seventh threshold. In the event that the temperature is greater than or equal to the sixth threshold and less than the seventh threshold, the method continues at step 414 where the opening of the economizer valve EHXV is calculated from the temperature of the refrigerant in the discharge line DLT at step 414. Thus, the operation is performed based on the discharge line control mode. Referring to fig. 3, step 414 may refer to operations performed with respect to the pressure and temperature located in region 72. In the event that the discharge line temperature is not greater than or equal to the sixth threshold and less than the seventh threshold, the method continues at step 416, where the economizer valve EHXV is closed and the compressor is shut down at step 416.

In the event the method reaches any of steps 406, 410, 414, or 416, the method may continue again at step 402 by determining or receiving a discharge line temperature. In this case, the method may determine or receive an updated value for the discharge line temperature.

Fig. 9 shows a decision diagram describing in more detail a method 500 for determining the opening degree of the economizer valve EHXV based on step 314 of the decision diagram of fig. 7.

After step 314, the method 500 receives the determined value for the temperature of the refrigerant in the discharge line at step 502.

At step 504, it is determined whether the discharge line temperature DLT is below an eighth threshold. In case the temperature is less than the eighth threshold value, the method continues at step 506, in which step 506 the opening degree of the economizer valve EHXV is calculated from the pressure of the refrigerant in the injection line and the superheat value. Thus, a combination of the overheating control mode and the injection pressure control mode is performed. Referring to fig. 3, step 506 may refer to operations performed with respect to the pressure and temperature located in region 73. Otherwise, the method continues at step 508.

At step 508, it is determined whether the discharge line temperature DLT is greater than or equal to the eighth threshold and less than the ninth threshold. In the case where the temperature is greater than or equal to the eighth threshold and less than the ninth threshold, the method continues at step 510 where the opening of the economizer valve is calculated based on the superheat value, the pressure of the refrigerant in the injection line, and the temperature of the refrigerant in the discharge line DLT at step 510. Thus, a combination of all three operation modes is performed. Referring to fig. 3, step 510 may refer to operations performed with respect to the pressure and temperature located in region 75. In the event that the discharge line temperature is not greater than or equal to the eighth threshold and less than the ninth threshold, the method continues at step 512, where, in step 512, the economizer valve EHXV is closed and the compressor is shut down.

In some embodiments, the eighth threshold is equal to the fifth threshold, and the ninth threshold is equal to the seventh threshold.

In the event that the method reaches any of steps 506, 510, or 512, the method may again continue at step 502 by determining or receiving a discharge line temperature. In this case, the method may determine or receive an updated value for the discharge line temperature.

Fig. 10 shows a decision diagram describing in more detail a method 600 for determining the opening degree of the economizer valve EHXV based on step 318 of the decision diagram of fig. 7.

After step 318, the method 600 receives the determined value for the temperature of the refrigerant in the discharge line at step 602.

At step 604, it is determined whether the discharge line temperature DLT is below a tenth threshold. In the event that the temperature is less than the tenth threshold, the method continues at step 606, where the opening of the economizer valve EHXV is calculated from the pressure of the refrigerant in the injection line in step 606. Thus, the injection pressure control mode is executed. Referring to fig. 3, step 606 may refer to operations performed with respect to the pressure and temperature located in region 74. Otherwise, the method continues at step 608.

At step 608, it is determined whether the discharge line temperature DLT is greater than or equal to the tenth threshold and less than the eleventh threshold. In the event that the temperature is greater than or equal to the tenth threshold and less than the eleventh threshold, the method continues at step 610, where the opening of the economizer valve is calculated from the superheat value, the pressure of the refrigerant in the injection line, and the temperature of the refrigerant in the discharge line DLT at step 610. Thus, a combination of all three operation modes is performed. Referring to fig. 3, step 610 may refer to operations performed with respect to the pressure and temperature located in region 75. In the event that the discharge line temperature is not greater than or equal to the tenth threshold and less than the eleventh threshold, the method continues at step 612, where in step 612, the economizer valve EHXV is closed and the compressor is shut down.

In some embodiments, the tenth threshold is equal to the fifth threshold and the eleventh threshold is equal to the seventh threshold.

In the event that the method reaches any of steps 606, 610, or 612, the method may again continue at step 602 by determining or receiving a discharge line temperature. In this case, the method may determine or receive an updated value for the discharge line temperature.

In some embodiments, based on the stakeholders described with respect to fig. 7-10To perform operations to control the operation. In this case, if the eighth threshold value is equal to the fifth threshold value and the ninth threshold value is equal to the seventh threshold value and the tenth threshold value is equal to the fifth threshold value and the eleventh threshold value is equal to the seventh threshold value, one reaches the regions 70 to 75 described with respect to fig. 2, where the first threshold value corresponds to p₀The second threshold value corresponds to p₁The third threshold value corresponds to p₂The fourth threshold corresponds to p_maxThe fifth threshold corresponds to T₁The sixth threshold corresponds to T₂And the seventh threshold corresponds to T_max. Thus, a first operating mode is performed in zone 70 as an overcontrol mode, a second operating mode is performed in zone 72 as a discharge line temperature control mode, and a third operating mode is performed in zone 74 as an injection pressure control mode, while a combination of the first and second control modes is performed in zone 71, a combination of the first and third operating modes is performed in zone 73, and a combination of all three operating modes is performed in zone 75, and the economizer expansion valve is shut down while the compressor is shut down outside of zones 70-75.

What has been described above includes examples of one or more implementations. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the scope of the appended claims.