Metering method, control device, refrigerating unit and storage medium

Abstract

The invention discloses a metering method, a control device, a refrigerating unit and a storage medium. The metering method is used for the refrigerating unit, the refrigerating unit comprises a compressor, a heat exchanger, an economizer and a plurality of sampling nodes, the compressor is connected with the heat exchanger, the economizer is connected with the compressor and the heat exchanger, and the sampling nodes are arranged among the compressor, the heat exchanger and the economizer. The metering method comprises the steps that the enthalpy difference of sampling nodes and the mechanical work of a compressor are determined according to performance parameters of the compressor, operation parameters of a heat exchanger and a preset pressure enthalpy characteristic curve table under the current working condition; and determining the refrigerant mass flow of the refrigerating unit according to the enthalpy difference of the sampling nodes and the mechanical work of the compressor. A water flow meter does not need to be additionally installed on a pipeline of the refrigerating unit, the size of the pipeline does not need to be considered, cost can be reduced, and the measurement precision of the refrigerant mass flow can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and more specifically, to a metering method, a control device, a refrigeration unit and a computer-readable storage medium. Background Art

[0002] In the related art, corresponding water flow meters are installed on the chilled water pipes and cooling water pipes in the centrifugal refrigeration unit, which can measure the mass flow of the refrigerant in the pipes of the centrifugal chiller, and obtain the cooling and heating capacity of the centrifugal refrigeration unit through the mass flow of the refrigerant. However, the installation and commissioning costs of the water flow meter are high, and the water flow meter is more stringent on the size of the installed pipe. If it is installed on a pipe that does not meet the standards, the measurement accuracy of the refrigerant mass flow will be low. Summary of the invention

[0003] A metering method, a control device, a refrigeration unit and a computer-readable storage medium provided in an embodiment of the present invention can solve the problems of high cost, inaccurate measurement accuracy and inaccurate refrigeration and heating capacity of the refrigeration unit caused by using a water flow meter in the refrigeration unit.

[0004] The metering method of the embodiment of the present invention is used for a refrigeration unit. The refrigeration unit includes a compressor, a heat exchanger, an economizer and a plurality of sampling nodes, the compressor is connected to the heat exchanger, the economizer is connected to the compressor and the heat exchanger respectively, the sampling node is arranged between the compressor, the heat exchanger and the economizer, and the metering method includes:

[0005] Determining the enthalpy difference of the sampling node and the mechanical work of the compressor according to the performance parameters of the compressor under the current working conditions, the operating parameters of the heat exchanger and a preset pressure-enthalpy characteristic curve table;

[0006] The refrigerant mass flow rate of the refrigeration unit is determined according to the enthalpy difference of the sampling node and the mechanical work of the compressor.

[0007] In this way, by obtaining the enthalpy difference of each sampling node in the refrigeration unit and the mechanical work of the compressor, the refrigerant mass flow rate of the refrigeration unit can be calculated, thereby eliminating the need to install an additional water flow meter on the pipeline of the refrigeration unit and the need to consider the size of the pipeline, thereby reducing costs and improving the measurement accuracy of the refrigerant mass flow rate.

[0008] In certain embodiments, the performance parameters of the compressor include at least one of the following: an operating pressure of the compressor, an operating temperature of the compressor, and an operating power of the compressor; and the operating parameters of the heat exchanger include an operating pressure of the heat exchanger and an operating temperature of the heat exchanger.

[0009] In this way, by obtaining the operating pressure, operating temperature and operating power of the compressor corresponding to the sampling node, the operating pressure and operating temperature of the heat exchanger, and substituting them into the preset pressure-enthalpy characteristic curve table, the enthalpy difference of the sampling node can be accurately obtained in the pressure-enthalpy characteristic curve table.

[0010] In some embodiments, the sampling nodes include a first sampling node, a second sampling node, a third sampling node, a fourth sampling node, and a fifth sampling node, the compressor includes a first compressor and a second compressor, the heat exchanger includes a first heat exchanger and a second heat exchanger, the first compressor is connected to the first heat exchanger, the second compressor is connected to the second heat exchanger, the first compressor is connected to the second compressor, the first sampling node is located between the first compressor and the first heat exchanger, the second sampling node is located between the second compressor and the second heat exchanger, the third sampling node is located between the second heat exchanger and the economizer, the fourth sampling node is located between the economizer and the compressor, and the fifth sampling node is located between the economizer and the first heat exchanger. The enthalpy difference of the sampling nodes and the mechanical work of the compressor are determined according to the performance parameters of the compressor under the current working conditions, the operating parameters of the heat exchanger, and the preset pressure-enthalpy characteristic curve table, including:

[0011] According to the performance parameters of the first compressor, the performance parameters of the second compressor, the operating parameters of the first heat exchanger, the operating parameters of the second heat exchanger and the preset pressure-enthalpy characteristic curve table under the current operating conditions, a first enthalpy difference of the first sampling node, a second enthalpy difference of the second sampling node, a third enthalpy difference of the third sampling node, a fourth enthalpy difference of the fourth sampling node, a fifth enthalpy difference of the fifth sampling node and the mechanical work of the compressor are determined.

[0012] In this way, by determining the enthalpy differences of the first sampling node, the second sampling node, the third sampling node, the fourth sampling node and the fifth sampling node, the work efficiency of the compressor and the heat exchanger on the refrigerant can be evaluated, and the foundation for measuring the refrigerant mass flow rate in the refrigeration unit can be laid.

[0013] In some embodiments, determining a fourth enthalpy difference of the fourth sampling node includes:

[0014] determining an operating pressure of the fourth sampling node according to an operating parameter of the first heat exchanger and an operating parameter of the second heat exchanger;

[0015] A fourth enthalpy difference of the fourth sampling node is determined according to the operating pressure of the fourth sampling node and the preset pressure-enthalpy characteristic curve table.

[0016] In this way, based on the operating parameters of the first heat exchanger and the operating parameters of the second heat exchanger, the operating pressure of the fourth sampling node can be determined, and the enthalpy difference of the fourth sampling node can be calculated based on the operating pressure of the fourth sampling node, which can reflect the conversion efficiency of the compressor to the refrigerant and lay the foundation for measuring the refrigerant mass flow rate in the refrigeration unit.

[0017] In some embodiments, determining a fifth enthalpy difference of the fifth sampling node includes:

[0018] A fifth enthalpy difference of the fifth sampling node is determined according to the operating parameters of the first heat exchanger, the operating pressure of the fourth sampling node and the preset pressure-enthalpy characteristic curve table.

[0019] In this way, by determining the fifth enthalpy difference of the fifth sampling node, the conversion efficiency of the heat exchanger to the refrigerant can be reflected, and a foundation can be laid for measuring the refrigerant mass flow rate in the refrigeration unit.

[0020] In certain embodiments, the performance parameter of the compressor includes the operating power of the compressor, and determining the mechanical work of the compressor includes:

[0021] The mechanical work of the compressor is determined according to the operating power of the first compressor, the operating power of the second compressor and a preset efficiency factor.

[0022] In this way, by calculating the mechanical work of the compressor, the actual working efficiency of the compressor can be indirectly reflected, and it can lay the foundation for measuring the refrigerant mass flow rate in the refrigeration unit.

[0023] In some embodiments, determining the refrigerant mass flow rate of the refrigeration unit according to the enthalpy difference of the sampling node and the mechanical work of the compressor includes:

[0024] The refrigerant mass flow rate of the refrigeration unit is determined according to a first enthalpy difference of the first sampling node, a second enthalpy difference of the second sampling node, a third enthalpy difference of the third sampling node, a fourth enthalpy difference of the fourth sampling node, a fifth enthalpy difference of the fifth sampling node, and the mechanical work of the compressor.

[0025] In this way, by determining the refrigerant mass flow rate of the refrigeration unit, the refrigeration system can be operated in the most energy-saving state, thereby improving the refrigeration efficiency and paving the way for calculating the refrigeration and heating capacity in the refrigeration unit.

[0026] In certain embodiments, the metering method further comprises:

[0027] determining a cooling and heating capacity of the first heat exchanger according to the first enthalpy difference, the fifth enthalpy difference and a refrigerant mass flow rate of the refrigeration unit;

[0028] Determining a refrigerant mass flow rate of a fourth sampling node included in the sampling nodes according to the third enthalpy difference, the fourth enthalpy difference and the fifth enthalpy difference;

[0029] The cooling and heating capacity of the second heat exchanger is determined according to the second enthalpy difference, the third enthalpy difference and the refrigerant mass flow rate at the fourth sampling node.

[0030] In this way, by obtaining the enthalpy difference of the sampling nodes, including the first enthalpy difference, the second enthalpy difference, the third enthalpy difference, the fourth enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the fifth sampling node, the cooling and heating capacity of the heat exchanger can be accurately determined without the use of an additional water flow meter, which can reduce costs, improve the measurement accuracy of the refrigerant mass flow rate and improve the accuracy of obtaining the cooling and heating capacity of the refrigeration unit.

[0031] In certain embodiments, the metering method comprises:

[0032] determining a cooling water mass flow rate of the first heat exchanger according to the cooling and heating capacity of the first heat exchanger, the operating parameters of the first heat exchanger and a preset constant-pressure specific heat capacity;

[0033] The cooling water mass flow rate of the second heat exchanger is determined according to the cooling and heating capacity of the second heat exchanger, the operating parameters of the second heat exchanger and the preset constant-pressure specific heat capacity.

[0034] In this way, after determining the cooling and heating capacity of the first heat exchanger and the cooling and heating capacity of the second heat exchanger, the cooling water mass flow of the first heat exchanger and the second heat exchanger can be accurately obtained according to the operating parameters of the first heat exchanger and the second heat exchanger under the current working conditions.

[0035] The control device of the embodiment of the present invention includes a processor and a memory; the memory stores a computer program, the computer program is executed by the processor, and the computer program includes instructions for executing the metering method described in any one of the above embodiments.

[0036] The refrigeration unit according to the embodiment of the present invention includes the control device described in any one of the above embodiments.

[0037] The non-volatile computer-readable storage medium containing a computer program according to an embodiment of the present invention includes a computer program. When the computer program is executed by a processor, the processor executes the metering method described in any one of the above embodiments.

[0038] Additional aspects and advantages of embodiments of the present invention will be given in part in the following description and in part will be obvious from the following description or learned through practice of embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0040] Figure 1 is a schematic diagram of a module of a refrigeration unit according to some embodiments of the present invention;

[0041] Figure 2 is a schematic flow diagram of a metering method according to certain embodiments of the present invention;

[0042] Figure 3 is a schematic diagram of a module of a control device in some embodiments of the present invention;

[0043] Figures 4 to 10 is a schematic flow diagram of a metering method according to certain embodiments of the present invention;

[0044] Fig.11 It is a schematic diagram of the connection status of a computer-readable storage medium and a processor according to some embodiments of the present invention.

[0045] Description of Figure Numbers:

[0046] 100. refrigeration unit; 10. compressor; 11. first compressor; 12. second compressor; 20. heat exchanger; 21. first heat exchanger; 22. second heat exchanger; 30. economizer; 40. sampling node; 41. first sampling node; 42. second sampling node; 43. third sampling node; 44. fourth sampling node; 45. fifth sampling node; 50. control device; 51. processor; 52. memory; 521. computer program; 200. computer readable storage medium. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of the present invention, and cannot be understood as limiting the embodiments of the present invention.

[0048] See also Figure 1 , Figure 2 and Figure 3 The metering method of the embodiment of the present invention is used for a refrigeration unit 100. The refrigeration unit 100 includes a compressor 10, a heat exchanger 20, an economizer 30 and a plurality of sampling nodes 40. The compressor 10 is connected to the heat exchanger 20, the economizer 30 is connected to the compressor 10 and the heat exchanger 20 respectively, and the sampling node 40 is arranged between the compressor 10, the heat exchanger 20 and the economizer 30. The metering method includes:

[0049] Step 011: Determine the enthalpy difference of the sampling node 40 and the mechanical work of the compressor 10 according to the performance parameters of the compressor 10 under the current working condition, the operating parameters of the heat exchanger 20 and the preset pressure-enthalpy characteristic curve table;

[0050] Step 012: Determine the refrigerant mass flow rate of the refrigeration unit 100 according to the enthalpy difference of the sampling node 40 and the mechanical work of the compressor 10 .

[0051] In this way, by obtaining the enthalpy difference of each sampling node 40 in the refrigeration unit 100 and the mechanical work of the compressor 10, the refrigerant mass flow rate of the refrigeration unit 100 can be calculated, thereby eliminating the need to install an additional water flow meter on the pipeline of the refrigeration unit 100 and the need to consider the size of the pipeline, thereby reducing costs and improving the measurement accuracy of the refrigerant mass flow rate.

[0052] Among them, the refrigeration unit 100 can be a first-stage centrifugal refrigeration unit or a second-stage centrifugal refrigeration unit with a flash tank or a plate exchanger economizer 30, which can provide low-temperature chilled water through a refrigeration cycle to meet various refrigeration needs. The present application takes a second-stage centrifugal refrigeration unit as an example for explanation. Among them, the refrigeration unit 100 includes a compressor 10, a heat exchanger 20, an economizer 30 and a plurality of sampling nodes 40. The compressor 10 can be a centrifugal compressor, which can provide power for the refrigerant to move through centrifugal force, and perform heat exchange when the refrigerant passes through the heat exchanger 20, thereby realizing a refrigeration cycle.

[0053] The heat exchanger 20 may be an evaporator or a condenser, and may be connected to the compressor 10 respectively, so that when the refrigerant flows through the evaporator or the condenser, heat exchange may be performed, thereby realizing a refrigeration cycle.

[0054] The economizer 30 can be a flash tank or a plate heat exchanger. The economizer 30 can be connected to the heat exchanger 20 so that the refrigerant after heat exchange in the heat exchanger 20 can flow through the economizer 30. The economizer 30 can absorb heat through the throttling evaporation of the refrigerant itself, so that another part of the refrigerant can be supercooled, which can significantly improve the refrigeration cycle efficiency of the refrigeration unit 100, increase the cooling capacity of the refrigeration unit 100, and reduce the exhaust temperature of the compressor 10.

[0055] The sampling node 40 is disposed on a pipeline of the refrigeration unit 100. For example, the sampling node 40 can be located on a pipeline connecting the compressor 10 and the compressor 10, on a pipeline connecting the compressor 10 and the heat exchanger 20, on a pipeline connecting the heat exchanger 20 and the economizer 30, or on a pipeline connecting the economizer 30 and the compressor 10.

[0056] The refrigeration unit 100 includes a control device 50, and the control device 50 includes a processor 51, a memory 52, and a computer program 521. The computer program 521 is stored in the memory 52 and executed by the processor 51, and the computer program 521 includes instructions for executing the metering method.

[0057] Specifically, the processor 51 can determine the enthalpy difference of the sampling node 40 and the mechanical work of the compressor 10 according to the performance parameters of the compressor 10 under the current working condition, the operating parameters of the heat exchanger 20 and the preset pressure-enthalpy characteristic curve table. The current working condition can be the cooling working condition or the heating working condition of the refrigeration unit 100.

[0058] The performance parameter of the compressor 10 includes at least one of the operating pressure of the compressor 10, the operating temperature of the compressor 10, and the operating power of the compressor 10. For example, the operating pressure of the compressor 10 may be the suction pressure or the exhaust pressure of the compressor 10; the operating temperature of the compressor 10 may be the suction temperature or the exhaust temperature of the compressor 10; and the operating power of the compressor 10 may be the real-time electric power of the inverter in the compressor 10.

[0059] The operating parameters of the heat exchanger 20 include the operating pressure of the heat exchanger 20 and the operating temperature of the heat exchanger 20. For example, the operating pressure of the heat exchanger 20 may be the condensing pressure when the condenser is in operation and the evaporating pressure when the evaporator is in operation; the operating temperature of the heat exchanger 20 may be the refrigerant temperature at the outlet side of the condenser and the refrigerant temperature at the refrigerant inlet side, or the operating temperature of the heat exchanger 20 may be the refrigerant temperature at the outlet side of the evaporator and the refrigerant temperature at the refrigerant inlet side.

[0060] The preset pressure-enthalpy characteristic curve table can be obtained by fitting a large amount of experimental data, and the preset pressure-enthalpy characteristic curve table includes various characteristic curves on the pressure-enthalpy diagram, such as saturation curve, isobars, isenthalpy lines, isotherms and isentropic lines. Various characteristic curves can be used to describe the state changes of the refrigerant at different pressures and enthalpy values. For example, the saturation curve can divide the pressure-enthalpy diagram into three areas, representing that the refrigerant exists in the form of liquid, vapor and a mixture of liquid and vapor, and in the semicircular area, the refrigerant can reach thermal equilibrium; isobars can represent the state changes of the refrigerant at the same pressure; isenthalpy lines can represent the state changes of the refrigerant at the same enthalpy value; isotherms can represent the state changes of the refrigerant at the same temperature; isentropic lines can represent the state changes of the refrigerant at the same entropy value.

[0061] For example, the compressor 10 is provided with devices such as a temperature sensor and a pressure sensor that can obtain the performance parameters of the compressor 10, so that the compressor 10 can transmit the performance parameters of the compressor 10 under the current working conditions to the processor 51; the heat exchanger 20 is provided with devices such as a temperature sensor and a pressure sensor that can obtain the operating parameters of the heat exchanger 20, so that the heat exchanger 20 can transmit the operating parameters of the heat exchanger 20 under the current working conditions to the processor 51; the memory 52 stores a pressure-enthalpy characteristic curve table, and the processor 51 can obtain the enthalpy difference of each sampling node 40 by inputting the obtained performance parameters of the compressor 10 and the operating parameters of the heat exchanger 20 into the pressure-enthalpy characteristic curve table, and the processor 51 can calculate the mechanical work of the compressor 10 by obtaining the real-time electric power of the inverter in the compressor 10.

[0062] After the processor 51 obtains the enthalpy difference of multiple sampling nodes 40 and the mechanical work of the compressor 10, it can obtain multiple two-variable linear equations related to the refrigerant mass flow rate of the refrigeration unit 100, and by combining the multiple two-variable linear equations to form a two-variable linear equation system, and solving the two-variable linear equation system, it is possible to obtain the value of the refrigerant mass flow rate of the refrigeration unit 100.

[0063] See also Figure 1 and Figure 4 In some embodiments, the sampling node 40 includes a first sampling node 41, a second sampling node 42, a third sampling node 43, a fourth sampling node 44 and a fifth sampling node 45, the compressor 10 includes a first compressor 11 and a second compressor 12, the heat exchanger 20 includes a first heat exchanger 21 and a second heat exchanger 22, the first compressor 11 is connected to the first heat exchanger 21, the second compressor 12 is connected to the second heat exchanger 22, the first compressor 11 is connected to the second compressor 12, the first sampling node 41 is located between the first compressor 11 and the first heat exchanger 21, the second sampling node 42 is located between the second compressor 12 and the second heat exchanger 22, the third sampling node 43 is located between the second heat exchanger 22 and the economizer 30, the fourth sampling node 44 is located between the economizer 30 and the compressor 10, and the fifth sampling node 45 is located between the economizer 30 and the first heat exchanger 21. Step 011: According to the performance parameters of the compressor 10 and the operating parameters of the heat exchanger 20 under the current working conditions, the enthalpy difference of the sampling node 40 and the mechanical work of the compressor 10 are determined, including:

[0064] Step 0111: According to the performance parameters of the first compressor 11, the performance parameters of the second compressor 12, the operating parameters of the first heat exchanger 21, the operating parameters of the second heat exchanger 22 and the preset pressure-enthalpy characteristic curve table under the current operating conditions, determine the first enthalpy difference of the first sampling node 41, the second enthalpy difference of the second sampling node 42, the third enthalpy difference of the third sampling node 43, the fourth enthalpy difference of the fourth sampling node 44, the fifth enthalpy difference of the fifth sampling node 45 and the mechanical work of the compressor 10.

[0065] In this way, by determining the enthalpy differences of the first sampling node 41, the second sampling node 42, the third sampling node 43, the fourth sampling node 44 and the fifth sampling node 45, the work efficiency of the compressor 10 and the heat exchanger 20 on the refrigerant can be evaluated, and the foundation for measuring the refrigerant mass flow rate in the refrigeration unit 100 can be laid.

[0066] Specifically, the compressor 10 includes a first compressor 11 and a second compressor 12, and the first compressor 11 can be connected to the second compressor 12 through a pipeline. The first compressor 11 can be a primary compressor in a two-stage centrifugal refrigeration unit, that is, a low-pressure compressor 10; the second compressor 12 can be a secondary compressor in a two-stage centrifugal refrigeration unit, that is, a high-pressure compressor 10.

[0067] The heat exchanger 20 includes a first heat exchanger 21 and a second heat exchanger 22. The first heat exchanger 21 can be an evaporator, and the second heat exchanger 22 can be a condenser. The first compressor 11 can be connected to the first heat exchanger 21 through a pipeline, and the second compressor 12 can be connected to the second heat exchanger 22 through a pipeline. After the first heat exchanger 21 is connected to the economizer 30 through a pipeline and a throttle valve arranged on the pipeline, it can be connected to the second heat exchanger 22 through a pipeline and a throttle valve arranged on the pipeline.

[0068] The sampling nodes 40 include a first sampling node 41, a second sampling node 42, a third sampling node 43, a fourth sampling node 44, and a fifth sampling node 45. The first sampling node 41 is located on the pipeline between the first compressor 11 and the first heat exchanger 21; the second sampling node 42 is located on the pipeline between the second compressor 12 and the second heat exchanger 22; the third sampling node 43 can be located on the pipeline between the second heat exchanger 22 and the economizer 30; the fourth sampling node 44 is located on the pipeline between the economizer 30 and the compressor 10; and the fifth sampling node 45 can be located on the pipeline between the first heat exchanger 21 and the economizer 30.

[0069] The processor 51 can obtain the suction temperature and suction pressure of the first compressor 11 through the temperature sensor and pressure sensor set in the first compressor 11; the processor 51 can obtain the exhaust temperature and exhaust pressure of the second compressor 12 through the temperature sensor and pressure sensor set in the second compressor 12.

[0070] The processor 51 stores the suction temperature and suction pressure inputs of the first compressor 11 in the pressure-enthalpy characteristic curve table in the memory 52, so as to determine the first enthalpy difference of the first sampling node 41; the processor 51 stores the exhaust temperature and exhaust pressure inputs of the second compressor 12 in the pressure-enthalpy characteristic curve table in the memory 52, so as to determine the second enthalpy difference of the second sampling node 42.

[0071] The processor 51 can obtain the subcooling and condensing pressure of the second heat exchanger 22 under the current working condition by means of the temperature sensor and the pressure sensor arranged in the second heat exchanger 22. The subcooling is a description of the extent to which the refrigerant liquid is further cooled after condensation, so that its temperature is lower than the saturation temperature under the condensing pressure. The subcooling of the second heat exchanger 22 refers to the difference between the saturated liquid temperature corresponding to the condensing pressure of the condenser under the current working condition and the actual temperature of the refrigerant liquid at the outlet side of the condenser. The processor 51 inputs the subcooling and condensing pressure of the second heat exchanger 22 into the pressure-enthalpy characteristic curve table stored in the memory 52, so as to determine the third enthalpy difference of the third sampling node 43.

[0072] The processor 51 can determine the fourth enthalpy difference of the fourth sampling node 44 and the fifth enthalpy difference of the fifth sampling node 445 by inputting the performance parameters of the first compressor 11, the performance parameters of the second compressor 12, the operating parameters of the first heat exchanger 21, and the operating parameters of the second heat exchanger 22 under the current operating conditions into a preset pressure-enthalpy characteristic curve table.

[0073] See also Figure 1 and 5 In some embodiments, step 0111: determining a fourth enthalpy difference of a fourth sampling node 44 comprises:

[0074] Step 01111: determining the operating pressure of the fourth sampling node 44 according to the operating parameters of the first heat exchanger 21 and the operating parameters of the second heat exchanger 22;

[0075] Step 01112: Determine a fourth enthalpy difference of the fourth sampling node according to the operating pressure of the fourth sampling node 44 and a preset pressure-enthalpy characteristic curve table.

[0076] In this way, according to the operating parameters of the first heat exchanger 21 and the operating parameters of the second heat exchanger 22, the operating pressure of the fourth sampling node 44 can be determined, and the enthalpy difference of the fourth sampling node 44 can be calculated according to the operating pressure of the fourth sampling node 44, which can reflect the conversion efficiency of the compressor 10 for the refrigerant and lay the foundation for measuring the refrigerant mass flow rate in the refrigeration unit 100.

[0077] Specifically, the sampling node 40 includes a fourth sampling node 44, and the fourth sampling node 44 is located between the economizer 30 and the compressor 10. For example, the economizer 30 can be connected to the pipeline connecting the first compressor 11 and the second compressor 12 through a pipeline, and the fourth sampling node 44 can be set on the pipeline connecting the first compressor 11 and the second compressor 12.

[0078] The processor 51 can obtain the operating pressure of the first heat exchanger 21 through the pressure sensor disposed in the first heat exchanger 21. For example, when the first heat exchanger 21 is an evaporator, the processor 51 can obtain the evaporation pressure of the evaporator.

[0079] The processor 51 can obtain the operating pressure of the second heat exchanger 22 through the pressure sensor disposed in the second heat exchanger 22. For example, when the first heat exchanger 21 is a condenser, the processor 51 can obtain the condensing pressure of the condenser.

[0080] Then, the evaporation pressure of the evaporator and the condensation pressure of the condenser are input into a preset equation for solving the operating pressure of the fourth sampling node 44, so that the processor 51 can calculate the operating pressure of the fourth sampling node 44. For example, the preset equation for solving the operating pressure of the fourth sampling node 44 may be:

[0081]

[0082] Wherein, P4 represents the operating pressure of the fourth sampling node 44; 1.05 can be determined by fitting a large amount of experimental data; P l Indicates the condensing pressure of the condenser; P z Indicates the evaporation pressure of the evaporator.

[0083] After acquiring the operating pressure of the fourth sampling node 44, the processor 51 inputs the operating pressure of the fourth sampling node 44 into the pressure-enthalpy characteristic curve table stored in the memory 52, so as to determine the fourth enthalpy difference of the fourth sampling node 44. For example, the refrigerant of the fourth sampling node 44 is a high-temperature and high-pressure gaseous refrigerant flowing out of the second compressor 12, which can correspond to the saturated gas phase boundary line in the pressure-enthalpy characteristic curve table. Then, by inputting the operating pressure of the fourth sampling node 44 into the pressure-enthalpy characteristic curve table, the processor 51 can determine that the intersection of the operating pressure of the fourth sampling node 44 and the saturated gas phase boundary line is the fourth enthalpy difference of the fourth sampling node 44.

[0084] See also Figure 1 and Figure 6 In some embodiments, step 0111: determining a fifth enthalpy difference of the fifth sampling node 45 comprises:

[0085] Step 01113: Determine the fifth enthalpy difference of the fifth sampling node 45 according to the operating parameters of the first heat exchanger 21 , the operating pressure of the fourth sampling node 44 and a preset pressure-enthalpy characteristic curve table.

[0086] In this way, by determining the fifth enthalpy difference of the fifth sampling node 45 , the conversion efficiency of the heat exchanger 20 on the refrigerant can be reflected, and a foundation can be laid for measuring the mass flow rate of the refrigerant in the refrigeration unit 100 .

[0087] Specifically, the sampling node 40 includes a fifth sampling node 45, which is located between the economizer 30 and the heat exchanger 20. For example, the fifth sampling node 45 can be located on a pipeline between the first heat exchanger 21 and the economizer 30, and the first heat exchanger 21 can be an evaporator.

[0088] The processor 51 can determine the fifth enthalpy difference of the fifth sampling node 45 according to the operating parameters of the first heat exchanger 21, the operating pressure of the fourth sampling node 44, and the pressure-enthalpy characteristic curve table. For example, the processor 51 can obtain the subcooling degree of the first heat exchanger 21 under the current working condition through the temperature sensor set in the first heat exchanger 21, and then the processor 51 inputs the subcooling degree of the first heat exchanger 21 and the operating pressure of the fourth sampling node 44 into the pressure-enthalpy characteristic curve table stored in the memory 52, so as to determine the fifth enthalpy difference of the fifth sampling node 45.

[0089] See also Figure 7 In some embodiments, the performance parameter of the compressor 10 includes the operating power of the compressor 10. Step 0111: determining the mechanical work of the compressor 10 includes:

[0090] Step 01114: Determine the mechanical work of the compressor 10 according to the operating power of the first compressor 11, the operating power of the second compressor 42 and a preset efficiency factor.

[0091] In this way, by calculating the mechanical work of the compressor 10 , the actual working efficiency of the compressor 10 can be indirectly reflected, and it can pave the way for measuring the mass flow rate of the refrigerant in the refrigeration unit 100 .

[0092] Specifically, the processor 51 can determine the mechanical work of the compressor 10 according to the operating power of the compressor 10 under the current working condition and the preset efficiency factor. For example, the processor 51 can obtain the real-time electric power of the inverter in the first compressor 11 and the real-time electric power of the inverter in the second compressor 12 under the current working condition, and by adding the two real-time electric powers and multiplying them by the preset efficiency factor, the processor 51 can determine the mechanical work of the compressor 10. The preset efficiency factor can be obtained by fitting a large amount of experimental data.

[0093] See also Figure 8In some embodiments, step 012: determining the refrigerant mass flow rate of the refrigeration unit 100 according to the enthalpy difference of the sampling node 40 and the mechanical work of the compressor 10, includes:

[0094] Step 0121: Determine the refrigerant mass flow rate of the refrigeration unit 100 according to the first enthalpy difference of the first sampling node 41, the second enthalpy difference of the second sampling node 42, the third enthalpy difference of the third sampling node 43, the fourth enthalpy difference of the fourth sampling node 44, the fifth enthalpy difference of the fifth sampling node 45 and the mechanical work of the compressor 10.

[0095] In this way, by determining the refrigerant mass flow rate of the refrigeration unit 100 , the refrigeration system can be operated in the most energy-saving state, thereby improving the refrigeration efficiency and paving the way for calculating the refrigeration and heating capacity of the refrigeration unit 100 .

[0096] Specifically, the processor 51 can determine the refrigerant mass flow rate of the refrigeration unit 100 according to the first enthalpy difference, the second enthalpy difference, the third enthalpy difference, the fourth enthalpy difference, the fifth enthalpy difference and the mechanical work of the compressor 10. Among them, the processor 51 can determine the binary linear equation about the refrigerant mass flow rate of the refrigeration unit 100 through the third enthalpy difference, the fourth enthalpy difference and the fifth enthalpy difference. For example, the binary linear equation about the refrigerant mass flow rate of the refrigeration unit 100 can be expressed as:

[0097]

[0098] Wherein, M represents the refrigerant mass flow of the refrigeration unit 100; x represents the mass flow at the fourth sampling node 44; h3 represents the third enthalpy difference of the third sampling node 43; h4 represents the fourth enthalpy difference of the fourth sampling node 44; and h5 represents the fifth enthalpy difference of the fifth sampling node 45.

[0099] The processor 51 can determine another binary linear equation about the refrigerant mass flow rate of the refrigeration unit 100 through the first enthalpy difference, the second enthalpy difference, the fourth enthalpy difference and the mechanical work of the compressor 10. For example, another binary linear equation about the refrigerant mass flow rate of the refrigeration unit 100 can be expressed as:

[0100] M*h1+x*h4+W comp =(M+x)*h2

[0101] Wherein, M represents the refrigerant mass flow rate of the refrigeration unit 100; x represents the mass flow rate at the fourth sampling node 44; h1 represents the first enthalpy difference of the first sampling node 41; h2 represents the second enthalpy difference of the second sampling node 42; h4 represents the fourth enthalpy difference of the fourth sampling node 44; W comp represents the mechanical work of the compressor 10 .

[0102] The processor 51 can determine the refrigerant mass flow rate of the refrigeration unit 100 by forming a system of two linear equations into two linear equations and solving the system.

[0103] See also Figure 1 and Fig. 9 In certain embodiments, the measuring method further comprises:

[0104] Step 013: determining the cooling and heating capacity of the first heat exchanger 21 according to the first enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the refrigeration unit 100;

[0105] Step 014: determining the refrigerant mass flow rate of the fourth sampling node 44 included in the sampling node 40 according to the third enthalpy difference, the fourth enthalpy difference and the fifth enthalpy difference;

[0106] Step 015: Determine the cooling and heating capacity of the second heat exchanger 22 according to the second enthalpy difference, the third enthalpy difference and the refrigerant mass flow rate of the fourth sampling node 44.

[0107] In this way, by obtaining the enthalpy difference of the sampling node 40, including the first enthalpy difference, the second enthalpy difference, the third enthalpy difference, the fourth enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the fifth sampling node 45, the cooling and heating capacity of the heat exchanger 20 can be accurately determined without the need for an additional water flow meter, which can reduce costs, improve the measurement accuracy of the refrigerant mass flow rate and improve the accuracy of obtaining the cooling and heating capacity of the refrigeration unit 100.

[0108] Specifically, the processor 51 can determine the cooling and heating capacity of the first heat exchanger 21 according to the first enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the refrigeration unit 100. The processor 51 can determine a linear equation for the cooling and heating capacity of the first heat exchanger 21 according to the first enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the refrigeration unit 100. For example, the linear equation for the cooling and heating capacity of the first heat exchanger 21 can be expressed as:

[0109] Q e =M*(h1-h5)

[0110] Among them, Q e represents the cooling and heating capacity of the first heat exchanger 21 ; M represents the refrigerant mass flow rate of the refrigeration unit 100 ; h1 represents the first enthalpy difference of the first sampling node 41 ; and h5 represents the fifth enthalpy difference of the fifth sampling node 45 .

[0111] The processor 51 can determine the refrigerant mass flow rate of the fifth sampling node 45 included in the sampling node 40 according to the third enthalpy difference, the fourth enthalpy difference and the fifth enthalpy difference. The processor 51 substitutes the third enthalpy difference, the fourth enthalpy difference, the fifth enthalpy difference and the refrigerant mass flow rate of the refrigeration unit 100 into a two-variable linear equation about the refrigerant mass flow rate of the refrigeration unit 100, thereby being able to calculate the refrigerant mass flow rate of the fourth sampling node 44.

[0112] Then, the processor 51 can determine the cooling and heating capacity of the second heat exchanger 22 according to the second enthalpy difference, the third enthalpy difference and the refrigerant mass flow rate of the fifth sampling node 45. The processor 51 can determine a linear equation for the cooling and heating capacity of the second heat exchanger 22 according to the second enthalpy difference, the third enthalpy difference and the refrigerant mass flow rate of the fifth sampling node 45. For example, the linear equation for the cooling and heating capacity of the second heat exchanger 22 can be expressed as:

[0113] Q c =(M+x)*(h2-h3)

[0114] Among them, Q c represents the cooling and heating capacity of the second heat exchanger 22; M represents the refrigerant mass flow rate of the refrigeration unit 100; x represents the mass flow rate at the fourth sampling node 44; h2 represents the second enthalpy difference of the second sampling node 42; h3 represents the third enthalpy difference of the third sampling node 43.

[0115] See also Fig.10 In certain embodiments, the measuring method comprises:

[0116] Step 016: Determine the cooling water mass flow rate of the first heat exchanger 21 according to the cooling and heating capacity of the first heat exchanger 21, the operating parameters of the first heat exchanger 21 and the preset constant-pressure specific heat capacity;

[0117] Step 017: Determine the cooling water mass flow rate of the second heat exchanger 22 according to the cooling and heating capacity of the second heat exchanger 22, the operating parameters of the second heat exchanger 22 and the preset constant-pressure specific heat capacity.

[0118] In this way, after determining the cooling and heating capacity of the first heat exchanger 21 and the cooling and heating capacity of the second heat exchanger 22, the cooling water mass flow rate of the first heat exchanger 21 and the second heat exchanger 22 can be accurately obtained according to the operating parameters of the first heat exchanger 21 and the second heat exchanger 22 under the current operating conditions.

[0119] Specifically, the processor 51 can determine the mass flow rate of cooling water of the first heat exchanger 21 according to the cooling and heating capacity of the first heat exchanger 21, the operating parameters of the first heat exchanger 21 and the preset constant-pressure specific heat capacity. Among them, the operating parameters of the first heat exchanger 21 include the outlet temperature and the inlet temperature of the cooling water of the first heat exchanger 21; the preset constant-pressure specific heat capacity is the amount of heat required to be absorbed when the temperature of a unit mass of the refrigerant increases by 1K (or 1°C, the two are numerically equal, but the units are different) under the condition of constant pressure. The processor 51 can determine a linear equation for the mass flow rate of cooling water of the first heat exchanger 21 according to the cooling and heating capacity of the first heat exchanger 21, the operating parameters of the first heat exchanger 21 and the preset constant-pressure specific heat capacity. For example, a linear equation for the mass flow rate of cooling water of the first heat exchanger 21 can be expressed as:

[0120]

[0121] Among them, M e represents the cooling water mass flow rate of the first heat exchanger 21; Q e represents the cooling and heating capacity of the first heat exchanger 21; C p Indicates the preset constant pressure specific heat capacity; T r represents the inlet temperature of the cooling water of the first heat exchanger 21; T s Indicates the outlet temperature of the cooling water of the first heat exchanger 21.

[0122] The processor 51 can determine the mass flow rate of cooling water of the second heat exchanger 22 according to the cooling and heating capacity of the second heat exchanger 22, the operating parameters of the second heat exchanger 22 and the preset specific heat capacity at constant pressure. The operating parameters of the second heat exchanger 22 include the outlet temperature and the inlet temperature of the cooling water of the second heat exchanger 22. The processor can determine the linear equation of the mass flow rate of cooling water of the second heat exchanger 22 according to the cooling and heating capacity of the first heat exchanger 21, the operating parameters of the second heat exchanger 22 and the preset specific heat capacity at constant pressure. For example, the linear equation of the mass flow rate of cooling water of the second heat exchanger 22 can be expressed as:

[0123]

[0124] Among them, M c represents the cooling water mass flow rate of the first heat exchanger 21; Q c Indicates the cooling and heating capacity of the second heat exchanger 22; C p Indicates the preset constant pressure specific heat capacity; T g represents the inlet temperature of the cooling water of the second heat exchanger 22; T k Indicates the outlet temperature of the cooling water of the second heat exchanger 22.

[0125] See also Fig.11The embodiment of the present invention further provides a computer-readable storage medium 200 on which a computer program 521 is stored. When the computer program 521 is executed by the processor 51, the steps of the metering method of any of the above-mentioned embodiments are implemented. For the sake of brevity, they are not repeated here.

[0126] In the description of this specification, the descriptions with reference to the terms "certain embodiments", "in an example", "exemplarily", etc., mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0127] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0128] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A metering method for a refrigeration unit, characterized in that: The refrigeration unit includes a compressor, a heat exchanger, an economizer and a plurality of sampling nodes, the compressor is connected to the heat exchanger, the economizer is connected to the compressor and the heat exchanger respectively, the sampling node is arranged between the compressor, the heat exchanger and the economizer, and the metering method includes: Determining the enthalpy difference of the sampling node and the mechanical work of the compressor according to the performance parameters of the compressor under the current working conditions, the operating parameters of the heat exchanger and a preset pressure-enthalpy characteristic curve table; The refrigerant mass flow rate of the refrigeration unit is determined according to the enthalpy difference of the sampling node and the mechanical work of the compressor.

2. The measuring method according to claim 1, characterized in that: The performance parameters of the compressor include at least one of the following: an operating pressure of the compressor, an operating temperature of the compressor, and an operating power of the compressor; the operating parameters of the heat exchanger include an operating pressure of the heat exchanger and an operating temperature of the heat exchanger.

3. The measuring method according to claim 1, characterized in that: The sampling nodes include a first sampling node, a second sampling node, a third sampling node, a fourth sampling node and a fifth sampling node, the compressor includes a first compressor and a second compressor, the heat exchanger includes a first heat exchanger and a second heat exchanger, the first compressor is connected to the first heat exchanger, the second compressor is connected to the second heat exchanger, the first compressor is connected to the second compressor, the first sampling node is located between the first compressor and the first heat exchanger, the second sampling node is located between the second compressor and the second heat exchanger, the third sampling node is located between the second heat exchanger and the economizer, the fourth sampling node is located between the economizer and the compressor, and the fifth sampling node is located between the economizer and the first heat exchanger. The enthalpy difference of the sampling nodes and the mechanical work of the compressor are determined according to the performance parameters of the compressor under the current working condition, the operating parameters of the heat exchanger and the preset pressure-enthalpy characteristic curve table, including: According to the performance parameters of the first compressor, the performance parameters of the second compressor, the operating parameters of the first heat exchanger, the operating parameters of the second heat exchanger and the preset pressure-enthalpy characteristic curve table under the current operating conditions, a first enthalpy difference of the first sampling node, a second enthalpy difference of the second sampling node, a third enthalpy difference of the third sampling node, a fourth enthalpy difference of the fourth sampling node, a fifth enthalpy difference of the fifth sampling node and the mechanical work of the compressor are determined.

4. The measuring method according to claim 3, characterized in that: The determining of the fourth enthalpy difference of the fourth sampling node comprises: determining an operating pressure of the fourth sampling node according to an operating parameter of the first heat exchanger and an operating parameter of the second heat exchanger; A fourth enthalpy difference of the fourth sampling node is determined according to the operating pressure of the fourth sampling node and the preset pressure-enthalpy characteristic curve table.

5. The measuring method according to claim 4, characterized in that: The determining of the fifth enthalpy difference of the fifth sampling node comprises: A fifth enthalpy difference of the fifth sampling node is determined according to the operating parameters of the first heat exchanger, the operating pressure of the fourth sampling node and the preset pressure-enthalpy characteristic curve table.

6. The measuring method according to claim 3, characterized in that: The performance parameter of the compressor includes the operating power of the compressor, and determining the mechanical work of the compressor includes: The mechanical work of the compressor is determined according to the operating power of the first compressor, the operating power of the second compressor and a preset efficiency factor.

7. The measuring method according to claim 3, characterized in that: Determining the refrigerant mass flow of the refrigeration unit according to the enthalpy difference of the sampling node and the mechanical work of the compressor includes: The refrigerant mass flow rate of the refrigeration unit is determined according to a first enthalpy difference of the first sampling node, a second enthalpy difference of the second sampling node, a third enthalpy difference of the third sampling node, a fourth enthalpy difference of the fourth sampling node, a fifth enthalpy difference of the fifth sampling node, and the mechanical work of the compressor.

8. The measuring method according to claim 7, characterized in that: The measurement method also includes: determining a cooling and heating capacity of the first heat exchanger according to the first enthalpy difference, the fifth enthalpy difference and a refrigerant mass flow rate of the refrigeration unit; Determining a refrigerant mass flow rate of a fourth sampling node included in the sampling nodes according to the third enthalpy difference, the fourth enthalpy difference and the fifth enthalpy difference; The cooling and heating capacity of the second heat exchanger is determined according to the second enthalpy difference, the third enthalpy difference and the refrigerant mass flow rate at the fourth sampling node.

9. The measuring method according to claim 8, characterized in that: The measurement method includes: determining a cooling water mass flow rate of the first heat exchanger according to the cooling and heating capacity of the first heat exchanger, the operating parameters of the first heat exchanger and a preset constant-pressure specific heat capacity; The cooling water mass flow rate of the second heat exchanger is determined according to the cooling and heating capacity of the second heat exchanger, the operating parameters of the second heat exchanger and the preset constant-pressure specific heat capacity.

10. A control device, characterized in that: include: processor, and; A memory, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the steps of the measurement method according to any one of claims 1 to 9 are implemented.

11. A refrigeration unit, characterized in that: Comprising the control device as claimed in claim 10.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the measurement method according to any one of claims 1 to 9 are implemented.

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