Method for estimating refrigerant inventory of refrigeration system, estimation device, and refrigeration system

Abstract

The embodiment of the present application provides a kind of refrigerant inventory estimation method of refrigerating system, estimation device and refrigerating system.The method comprises obtaining the temperature information and pressure information of refrigerant at the inlet of expansion valve;According to the pressure information at the inlet of expansion valve and the temperature information of refrigerant at the inlet of expansion valve, determine the supercooling degree at the inlet of expansion valve;According to calibration experiment, determine the supercooling degree at the inlet of expansion valve of refrigerating system and the refrigerant inventory correlation model;According to the supercooling degree at the inlet of expansion valve, estimate refrigerant inventory based on the supercooling degree at the inlet of expansion valve and the refrigerant inventory correlation model.The technical scheme provided by the embodiment can estimate the quality of refrigerant inventory in real time, accurately estimate refrigerant inventory by the supercooling degree at the inlet of expansion valve, solve the problem that the refrigerant inventory estimation accuracy of existing refrigerant inventory detection method is poor.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a method, device and system for estimating the refrigerant inventory in a refrigeration system. Background Technology

[0002] In vapor compression refrigeration systems, refrigerant, as the core medium for energy transfer, directly determines the system's operational performance, energy efficiency, and reliability. Insufficient refrigerant can lead to reduced cooling / heating capacity, increased compressor discharge temperature, and decreased COP (coefficient of performance), potentially causing compressor damage due to poor lubrication or overheating. Conversely, excessive refrigerant can cause condenser buildup and abnormal evaporation pressure, similarly affecting system stability and lifespan. Therefore, accurately determining the refrigerant level within the refrigeration system is crucial for system installation, commissioning, maintenance, and troubleshooting.

[0003] Existing methods for detecting refrigerant levels in refrigeration systems suffer from poor accuracy in estimating refrigerant levels. Summary of the Invention

[0004] This invention provides a method, apparatus, and system for estimating the refrigerant inventory in a refrigeration system, in order to address the problem of poor accuracy in estimating refrigerant inventory in existing methods for detecting refrigerant inventory in refrigeration systems.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for estimating the refrigerant inventory in a refrigeration system, comprising:

[0007] Obtain the temperature and pressure information of the refrigerant at the expansion valve inlet;

[0008] The subcooling degree of the expansion valve inlet is determined based on the pressure information at the expansion valve inlet and the temperature information of the refrigerant at the expansion valve inlet.

[0009] Based on calibration experiments, a correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory was determined.

[0010] Based on the subcooling at the expansion valve inlet, and using a correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, the refrigerant inventory is estimated.

[0011] Optionally, determining the subcooling at the expansion valve inlet based on the pressure information at the expansion valve inlet and the refrigerant temperature information at the expansion valve inlet includes:

[0012] Based on the pressure information at the inlet of the expansion valve, determine the saturation temperature of the refrigerant corresponding to the pressure information at the inlet of the expansion valve;

[0013] The subcooling degree at the expansion valve inlet is determined based on the difference between the refrigerant temperature at the expansion valve inlet and the saturation temperature.

[0014] Optionally, the step of determining the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory based on calibration experiments includes:

[0015] Set calibration conditions, which include ambient temperature, evaporator load, and compressor frequency;

[0016] Different masses of refrigerant are charged into the refrigeration system, based on the designed refrigerant quantity. Starting with the design of refrigerant volume The step size is the refrigerant volume to be designed. Termination, calibration experiment, calculate the subcooling degree at the expansion valve inlet corresponding to the refrigerant quantity, and record the mass of the corresponding refrigerant quantity;

[0017] Based on the mass of refrigerant stock from the calibration experiment and the corresponding subcooling at the expansion valve inlet, a least squares fitting method was used to obtain a correlation model between the subcooling at the expansion valve inlet and the refrigerant stock.

[0018] Optionally, the correlation model between the subcooling degree at the expansion valve inlet and the refrigerant inventory is calculated using the following formula:

[0019] ;

[0020] in, Let a, b, and c represent the mass of the refrigerant in the refrigeration system, and a, b, and c represent model coefficients. This refers to the actual subcooling at the expansion valve inlet.

[0021] Optionally, after estimating the refrigerant inventory based on the subcooling at the expansion valve inlet and a refrigerant inventory correlation model, the method further includes:

[0022] Obtain the current operating status of the refrigeration system;

[0023] Based on the difference between the current operating conditions and the calibration conditions, the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is corrected, and the corrected correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is determined.

[0024] Based on the modified correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, the refrigerant inventory is estimated according to the subcooling at the expansion valve inlet.

[0025] Optionally, the step of correcting the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory based on the difference between the current operating condition and the calibration condition, and determining the corrected correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, includes:

[0026] Obtain the ambient temperature, evaporator load, and compressor frequency for the current operating conditions;

[0027] Based on the difference between the ambient temperature under the current operating condition and the ambient temperature under the calibration condition, the difference between the evaporator load under the current operating condition and the evaporator load under the calibration condition, and the difference between the compressor frequency under the current operating condition and the compressor frequency under the calibration condition, the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is modified to obtain the modified correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory.

[0028] Optionally, the modified correlation model between the subcooling degree at the expansion valve inlet and the refrigerant inventory adopts the following formula:

[0029] ;

[0030] in, This is an estimate of the quality of the corrected refrigerant inventory. , , These are the ambient temperature, evaporator load, and compressor frequency under the rated operating conditions. , , This is the working condition correction factor.

[0031] Optionally, after estimating the refrigerant inventory based on the subcooling at the expansion valve inlet and a refrigerant inventory correlation model, the method further includes:

[0032] Based on the difference between the refrigerant inventory and the first preset inventory threshold, a refrigerant shortage warning is triggered;

[0033] Based on the difference between the refrigerant inventory and the second preset inventory threshold, a refrigerant overload warning is triggered;

[0034] The first preset inventory threshold is less than the second preset inventory threshold.

[0035] Secondly, this embodiment provides a device for estimating the refrigerant inventory of a refrigeration system, comprising:

[0036] The acquisition module is used to acquire the temperature and pressure information of the refrigerant at the inlet of the expansion valve;

[0037] The subcooling calculation module is used to determine the subcooling at the inlet of the expansion valve based on the pressure information at the inlet of the expansion valve and the temperature information of the refrigerant at the inlet of the expansion valve.

[0038] The model determination module is used to determine the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory based on calibration experiments.

[0039] The estimation module is used to estimate the refrigerant inventory based on the subcooling at the expansion valve inlet and a refrigerant inventory correlation model.

[0040] Thirdly, this embodiment provides a refrigeration system, including: a refrigerant inventory estimation device for the refrigeration system provided in the second aspect, as well as a compressor, a condenser, an expansion valve, an evaporator, a temperature sensor, and a pressure sensor;

[0041] The compressor is connected to the condenser, the condenser is connected to the expansion valve, the expansion valve is connected to the evaporator, and the evaporator is connected to the compressor; the pressure sensor and the temperature sensor are located at the inlet of the expansion valve; the pressure sensor and the temperature sensor are respectively connected to the refrigerant inventory estimation device of the refrigeration system.

[0042] The refrigerant inventory estimation method for refrigeration systems provided in this embodiment addresses the problems of existing refrigerant inventory estimation methods being complex to operate, having weak anti-interference capabilities, and low accuracy. The refrigerant inventory estimation method for refrigeration systems provided in this embodiment achieves real-time and accurate estimation of the refrigerant inventory of the refrigeration system by constructing a correlation model of "subcooling degree at the inlet of the expansion valve - refrigerant inventory". It also has the advantages of being easy to operate, highly versatile, and having strong anti-interference capabilities. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0044] Figure 1 This is a flowchart of a method for estimating the refrigerant inventory in a refrigeration system provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the structure of a refrigeration system provided in an embodiment of the present invention;

[0046] Figure 3This is a fitting curve diagram of refrigerant inventory and corresponding subcooling at the inlet of the expansion valve provided by an embodiment of the present invention;

[0047] Figure 4 This is a flowchart of another method for estimating the refrigerant inventory in a refrigeration system provided in an embodiment of the present invention. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0050] Based on the above-mentioned technical problems, this embodiment proposes the following solutions:

[0051] Figure 1 This is a flowchart illustrating a method for estimating the refrigerant inventory in a refrigeration system, provided in an embodiment of the present invention. See also... Figure 1 The method for estimating the refrigerant inventory in a refrigeration system provided in this embodiment of the invention includes:

[0052] S101. Obtain the temperature information T1 and pressure information P1 of the refrigerant at the expansion valve inlet.

[0053] Specifically, Figure 2 This is a schematic diagram of a refrigeration system provided in an embodiment of the present invention. See also... Figure 2 The refrigeration system may include a compressor 1, a condenser 2, an expansion valve 3, an evaporator 4, a refrigerant mass flow meter 5, a gas-liquid separator 6, and connecting pipes 7. Sensors 8 are installed at key locations in the refrigeration system to collect operating parameters, providing a data basis for calculating the subcooling degree at the expansion valve inlet and estimating the refrigerant inventory.

[0054] For example, a first temperature sensor 811 and a first pressure sensor 812 are installed in the expansion valve inlet pipeline to collect the actual temperature and pressure of the refrigerant at the expansion valve inlet.

[0055] For example, a second temperature sensor 821 and a second pressure sensor 822 can be installed at the evaporator inlet to collect the actual temperature of the refrigerant at the evaporator inlet. With pressure A third temperature sensor 831 and a third pressure sensor 832 are installed at the evaporator outlet to collect the actual temperature of the refrigerant at the evaporator outlet. With pressure A fifth pressure sensor 85 is installed at the compressor suction port to collect the compressor suction pressure.

[0056] Among these requirements, the measurement accuracy of the sensor must meet the following standards: temperature sensor accuracy. Pressure sensor accuracy Full scale is used to ensure the accuracy of parameter acquisition.

[0057] If the refrigeration system is a single-temperature zone device, the actual temperature and pressure of the refrigerant at the expansion valve inlet can be used as the temperature information of the refrigerant at the expansion valve inlet. and stress information .

[0058] If the refrigeration system is a multi-temperature zone device containing multiple parallel evaporators, a temperature sensor and a pressure sensor need to be installed at the inlet of each evaporator expansion valve, and the average temperature at all expansion valve inlets should be taken as the temperature information. The average pressure at the inlet of all expansion valves is taken as the pressure information. This is to eliminate the uneven parameter effects caused by differences in the piping of multiple indoor units.

[0059] S102. Based on the pressure information at the expansion valve inlet and the temperature information of the refrigerant at the expansion valve inlet. Determine the subcooling degree at the inlet of the expansion valve. .

[0060] Specifically, the subcooling at the expansion valve inlet refers to the difference between the refrigerant temperature at the expansion valve inlet and the refrigerant saturation temperature at the corresponding pressure. The subcooling at the expansion valve inlet directly reflects the liquefaction stability of the refrigerant in the section from condenser 2 to expansion valve 3, and its changes are strongly coupled with the refrigerant level in the refrigeration system. For example, when the refrigerant level decreases, the refrigerant level in condenser 2 drops, resulting in insufficient heat exchange and a significant decrease in the subcooling at the expansion valve 3 inlet. Conversely, when the refrigerant level is excessive, the subcooling at the expansion valve 3 inlet will increase abnormally.

[0061] S103. Based on the calibration experiment, determine the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory.

[0062] Specifically, through calibration experiments, experimental data on the subcooling and refrigerant quantity at the expansion valve inlet of the refrigeration system are obtained. Based on the experimental data on the subcooling and refrigerant quantity at the expansion valve inlet of the refrigeration system, the functional relationship between the subcooling and refrigerant quantity at the expansion valve inlet of the refrigeration system is determined, and then the correlation model between the subcooling and refrigerant quantity at the expansion valve inlet of the refrigeration system is determined.

[0063] S104. Based on the subcooling at the expansion valve inlet, and using the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, estimate the refrigerant inventory.

[0064] Specifically, the subcooling at the expansion valve inlet can be calculated using real-time temperature and pressure information collected at the expansion valve inlet. This subcooling is then input into a refrigerant quantity correlation model to calculate and output the refrigerant quantity. Calculating the refrigerant quantity using this model improves the accuracy of refrigerant quantity estimation.

[0065] The refrigerant inventory estimation method for refrigeration systems provided in this embodiment addresses the problems of existing refrigerant inventory estimation methods being complex to operate, having weak anti-interference capabilities, and low accuracy. This embodiment's refrigerant inventory estimation method for refrigeration systems achieves real-time and accurate estimation of the refrigerant inventory by constructing a correlation model of "subcooling degree at the expansion valve inlet - refrigerant inventory". It also has the advantages of being easy to operate, highly versatile, and having strong anti-interference capabilities.

[0066] Optionally, based on the above embodiments, step S102, which involves using the pressure information at the expansion valve inlet and the temperature information of the refrigerant at the expansion valve inlet... Determining the subcooling ΔTᵥ at the inlet of the expansion valve may include:

[0067] First, based on the pressure information at the expansion valve inlet, determine the saturation temperature of the refrigerant corresponding to the pressure information at the expansion valve inlet. .

[0068] Secondly, based on the temperature information of the refrigerant at the inlet of the expansion valve. With the saturation temperature The difference is used to determine the subcooling at the inlet of the expansion valve. .

[0069] Specifically, based on the expansion valve inlet pressure information By using the refrigerant thermodynamic property table and based on the type of refrigerant used in the refrigeration system, such as R134A, R23, or R410A, the expansion valve inlet pressure information can be obtained. The corresponding saturation temperature of the refrigerant .

[0070] Calculate the actual subcooling at the expansion valve inlet. The formula is: .

[0071] in, The actual subcooling at the expansion valve inlet (unit: ), Actual refrigerant temperature at the expansion valve inlet (unit: ), For expansion valve inlet pressure information The corresponding saturation temperature of the refrigerant (unit: ).

[0072] Optionally, based on the above embodiments, see also... Figure 1 The above step S103, determining the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory based on the calibration experiment, may include:

[0073] First, set the calibration conditions, which include ambient temperature, evaporator load, and compressor frequency.

[0074] For details, please refer to [link / reference]. Figure 2 Collect compressor operating frequency f and ambient temperature. And evaporator load Q. Ambient temperature. The ambient temperature is on the condenser side. The evaporator load Q is the cooling capacity requirement on the evaporator side.

[0075] Experimental preparation: Before calibration, the refrigeration system needs to be evacuated, for example, the vacuum level needs to be adjusted. Let it stand for more than 2 hours to ensure that the refrigerant in the refrigeration system is evenly distributed and to avoid residual air or moisture interfering with the experimental data.

[0076] Calibration condition setting: Conduct the experiment under the rated operating conditions of the refrigeration system. The rated operating conditions of the refrigeration system can be ambient temperature. Evaporator load The compressor frequency f = the rated frequency.

[0077] Secondly, different masses of refrigerant are charged into the refrigeration system, based on the designed refrigerant quantity. Starting with the design of refrigerant volume The step size is the refrigerant volume to be designed. Termination, proceed with calibration experiments, and calculate the subcooling at the expansion valve inlet corresponding to the refrigerant quantity. And record the corresponding refrigerant inventory.

[0078] For example, standard refrigerant of different masses is charged into the refrigeration system, with the charge amount ranging from the designed refrigerant amount. Each interval The design refrigerant quantity is recorded once, and the subcooling degree at the expansion valve inlet is obtained from a single calculation. Record the corresponding refrigerant inventory. (Unit: kg). It should be noted that the expansion valve inlet subcooling... This refers to the subcooling at the expansion valve inlet.

[0079] Thirdly, based on the refrigerant inventory and the corresponding subcooling at the expansion valve inlet from the calibration experiment, the least squares method is used to fit and obtain the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory.

[0080] Specifically, Figure 3 This is a fitting curve diagram of refrigerant inventory and corresponding subcooling at the expansion valve inlet, provided by an embodiment of the present invention. See also... Figure 3 The red text indicates key data points, namely, refrigerant inventory. , , The relationship between the subcooling at the expansion valve inlet and the total refrigerant level is shown. Blue represents all calibration experimental data points. The black curve is a quadratic fit curve between the subcooling at the expansion valve inlet and the refrigerant quantity corresponding to the calibration experimental data points.

[0081] Before the calibration experiment, the refrigeration system was evacuated to a high vacuum and allowed to stand to ensure the accuracy of the experimental data. The designed refrigerant quantity was then charged under rated operating conditions. Standard refrigerant, interval The refrigerant quantity recording data was designed, and a quadratic correlation model of "subcooling degree at expansion valve inlet - refrigerant quantity" was fitted using the least squares method to reduce the relative error of the "subcooling degree at expansion valve inlet - refrigerant quantity" correlation model. This results in a high accuracy in estimating refrigerant inventory.

[0082] The refrigerant inventory estimation method for the refrigeration system provided in this embodiment focuses on the subcooling degree at the expansion valve inlet, a key parameter strongly coupled with refrigerant inventory. It uses high-precision sensors to collect data and fits a quadratic correlation model using the least squares method to control the relative estimation error within a certain range. Within this range, it is far superior to the methods used in related technologies for estimating refrigerant inventory. Given the above error levels, the refrigerant inventory estimation method for the refrigeration system provided in this embodiment offers accurate data support for the operation and maintenance of the refrigeration system.

[0083] Optionally, based on the above embodiments, the correlation model between the subcooling degree at the expansion valve inlet and the refrigerant inventory is calculated using the following formula: .

[0084] in, Let be the mass of the refrigerant in the refrigeration system (unit: kg), and a, b, and c be model coefficients. The actual subcooling at the expansion valve inlet (unit: The model coefficients are obtained by fitting calibration experimental data. Different types of refrigerants and different refrigeration system structures correspond to different model coefficients, thus improving versatility. For example, Figure 3 Example shown , , In this case, no restrictions are imposed.

[0085] Optional, Figure 4 This is a flowchart illustrating another method for estimating the refrigerant inventory in a refrigeration system provided by an embodiment of the present invention. Based on the above embodiments, see [link to other embodiments]. Figure 4 The method for estimating the refrigerant inventory in a refrigeration system provided in this embodiment of the invention may include:

[0086] S201. Obtain the temperature information of the refrigerant at the expansion valve inlet. and stress information .

[0087] S202, Based on the pressure information at the expansion valve inlet and the temperature information of the refrigerant at the expansion valve inlet. Determine the subcooling degree at the inlet of the expansion valve. .

[0088] S203. Based on the calibration experiment, determine the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory.

[0089] S204. Based on the subcooling at the expansion valve inlet, and using the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, estimate the refrigerant inventory.

[0090] S205. Obtain the current operating conditions of the refrigeration system.

[0091] Specifically, the current operating conditions of the refrigeration system include the current ambient temperature, current evaporator load, and current compressor frequency.

[0092] S206. Based on the difference between the current operating condition and the calibration condition, the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is modified, and the modified correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is determined.

[0093] Specifically, the rated operating condition refers to the ambient temperature under the rated operating conditions of the refrigeration system. Evaporator load compressor frequency Rated frequency.

[0094] Based on the differences between the current operating conditions and the calibration conditions, the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is modified. The modified correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory is determined so that it can meet the accuracy requirements of refrigerant inventory estimation under different operating conditions.

[0095] S207. Based on the modified correlation model between the subcooling degree at the expansion valve inlet and the refrigerant inventory, estimate the refrigerant inventory according to the subcooling degree at the expansion valve inlet.

[0096] Specifically, the modified subcooling input at the expansion valve inlet and the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory improve the accuracy of refrigerant inventory estimation under different operating conditions.

[0097] Optionally, based on the above embodiments, the step of correcting the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory according to the difference between the current operating condition and the calibration condition, and determining the corrected correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, includes:

[0098] First, obtain the ambient temperature under the current operating conditions. Evaporator load Q and compressor frequency f.

[0099] Secondly, based on the ambient temperature under the current operating conditions. Ambient temperature under calibration conditions The difference between the two, the evaporator load Q under the current operating condition and the evaporator load under the calibration condition. The difference between them, the compressor frequency f under the current operating condition and the compressor frequency under the calibrated operating condition The difference between the values ​​is used to correct the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, resulting in a corrected correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory.

[0100] Specifically, when there is a deviation between the actual operating conditions and the calibration conditions, an operating condition correction coefficient is introduced to correct the correlation model between the subcooling at the expansion valve inlet and the refrigerant inventory, thereby improving the estimation accuracy under different operating conditions. For example, the value range of the operating condition correction coefficient is 0.3 to 0.3.

[0101] Optionally, based on the above embodiments, the modified correlation model between the subcooling degree at the expansion valve inlet and the refrigerant inventory adopts the following formula:

[0102] .

[0103] in, The revised refrigerant inventory is an estimated value (unit: kg). , , These are the ambient temperature, evaporator load, and compressor frequency under the rated operating conditions. , , This is the working condition correction factor.

[0104] Optionally, based on the above embodiments, after estimating the refrigerant inventory according to the subcooling at the expansion valve inlet and a refrigerant inventory correlation model, the method may further include:

[0105] Step 1: Trigger a refrigerant shortage warning based on the difference between the refrigerant inventory and the first preset inventory threshold.

[0106] Step 2: Trigger an over-refrigerant warning based on the difference between the refrigerant level and the second preset refrigerant level threshold. The first preset refrigerant level threshold is less than the second preset refrigerant level threshold.

[0107] Specifically, the first preset refrigerant level threshold can be 0.8 × the designed refrigerant quantity. The second preset refrigerant level threshold can be 1.2 × the designed refrigerant quantity. For example, when the refrigerant level is less than the first preset level threshold, a refrigerant shortage warning is triggered. When the refrigerant level is greater than the second preset level threshold, a refrigerant excess warning is triggered, thus achieving timely warning of the refrigerant status of the refrigeration system.

[0108] An alternative implementation, exemplary, is illustrated below with a refrigeration system for a 10HP split-type environmental test facility using R410A refrigerant (design refrigerant capacity). Taking (e.g.) as an example, the specific implementation process of the present invention will be described in detail:

[0109] This embodiment provides a specific implementation method for a system calibration experiment as follows:

[0110] Experimental preparation: The refrigeration system of the environmental testing equipment was installed in the enthalpy difference laboratory, which allows for precise control of the ambient temperature and evaporator load. The refrigeration system was evacuated to a vacuum level. Let stand for 2 hours. Install sensor: Temperature sensor: Pt100 three-wire system, accuracy... Pressure sensor: piezoelectric, accuracy... .

[0111] Calibration conditions: enthalpy difference, laboratory condenser side ambient temperature Evaporator load on the evaporator side That is, the design cooling capacity; compressor frequency. That is, the rated frequency.

[0112] Data acquisition: R410A refrigerant was charged into the refrigeration system, starting from 6.0 kg ( Start at 0.4 kg intervals (approximately) Record the data once, until it reaches 11.0 kg. A total of 13 data points were collected, and some of the data is shown in Table 1 below:

[0113] Table 1 shows the relationship between the parameter information of the refrigeration system and the actual refrigerant inventory.

[0114]

[0115] Model Fitting: The least squares method was used to fit the above 13 data points to obtain the correlation model of "subcooling degree at expansion valve inlet - refrigerant inventory". .

[0116] Model validation: Combining Figure 3 Select refrigerant inventory Subcooling at the inlet of the expansion valve at three points , , Substituting into the correlation model of "subcooling degree at expansion valve inlet - refrigerant inventory", the result is calculated as follows: They are respectively , , The relative errors are all This indicates that the correlation model of "subcooling degree at expansion valve inlet - refrigerant inventory" is qualified.

[0117] Operating condition correction factor calibration: changing ambient temperature ( ), Evaporator load ( , The compressor frequency (f=50Hz, 70Hz) was used for multi-condition calibration, and the operating condition correction coefficient was obtained by fitting the data. , (Based on design load) .

[0118] This embodiment provides a specific implementation method for real-time refrigerant inventory estimation as follows:

[0119] Parameter acquisition: The actual operating parameters of the refrigeration system at a certain moment are as follows: , , Real-time acquisition of: Pressure information at the expansion valve inlet. Temperature information at the expansion valve inlet .

[0120] Calculate the subcooling at the actual expansion valve inlet. :

[0121] Depend on Consulting the R410A thermodynamic property table, we obtain... .

[0122] .

[0123] Refrigerant inventory estimation: Substituting "subcooling at expansion valve inlet - refrigerant inventory" into the correlation model:

[0124]

[0125]

[0126] .

[0127] Operating condition correction:

[0128]

[0129]

[0130]

[0131] .

[0132] Early warning output: This triggers a "severe refrigerant shortage" warning, prompting maintenance personnel to replenish the refrigerant.

[0133] The refrigerant inventory estimation method for the refrigeration system provided in this embodiment does not require interruption of the refrigeration system operation. By collecting parameters such as temperature and pressure information in real time, it can achieve refrigerant inventory estimation 1 to 5 times per second, which meets the real-time monitoring needs of the dynamic operation of the refrigeration system and is especially suitable for complex refrigeration systems that require dynamic adjustment.

[0134] The refrigerant inventory estimation method for the refrigeration system provided in this embodiment fits the model coefficients through a single calibration experiment for different refrigeration systems and different types of refrigerants. It can be adapted to different refrigerant types, such as R134A, R23, and R410A, and can also be adapted to refrigeration systems with different structures, such as industrial refrigeration equipment and commercial chiller units. There is no need to redevelop the algorithm for different systems, so it has a wide range of applications.

[0135] The refrigerant inventory estimation method for the refrigeration system provided in this embodiment does not require additional complex hardware. It only requires the addition of a small number of high-precision temperature and pressure sensors to the existing refrigeration system. Some refrigeration systems already have relevant temperature and pressure sensors, which can be directly reused. The method is easy to install and maintain, has low investment costs, and is convenient for engineering promotion and application.

[0136] In addition to the core function of estimating refrigerant inventory, the refrigerant inventory estimation method provided in this embodiment can extend to automatic early warning based on the estimation results, intelligent refrigerant replenishment control for refrigerant shortage and / or refrigerant excess, and provide data basis for refrigeration system optimization and compressor overheat protection, effectively improving the overall intelligent operation level and reliability of the refrigeration system.

[0137] Based on the same inventive concept, this embodiment provides a device for estimating the refrigerant inventory in a refrigeration system. The device for estimating the refrigerant inventory in a refrigeration system provided in this embodiment may include:

[0138] The acquisition module is used to acquire the temperature and pressure information of the refrigerant at the inlet of the expansion valve;

[0139] The subcooling calculation module is used to determine the subcooling at the inlet of the expansion valve based on the pressure information at the inlet of the expansion valve and the temperature information of the refrigerant at the inlet of the expansion valve.

[0140] The model determination module is used to determine the correlation model between the subcooling degree at the expansion valve inlet of the refrigeration system and the refrigerant inventory based on calibration experiments.

[0141] The estimation module is used to estimate the refrigerant inventory based on the subcooling at the expansion valve inlet and a refrigerant inventory correlation model.

[0142] The refrigerant inventory estimation device for refrigeration systems provided in this embodiment addresses the problems of complex operation, weak anti-interference ability, and low accuracy of existing refrigerant inventory estimation devices. This device acquires the temperature and pressure information of the refrigerant at the expansion valve inlet through an acquisition module; and determines the subcooling degree at the expansion valve inlet based on the pressure and temperature information of the refrigerant at the expansion valve inlet through a subcooling calculation module. Then, a model determination module determines the correlation model between the subcooling degree and refrigerant inventory at the expansion valve inlet based on calibration experiments. Finally, an estimation module estimates the refrigerant inventory based on the subcooling degree and the refrigerant inventory correlation model at the expansion valve inlet. The refrigerant inventory estimation device for refrigeration systems provided in this embodiment achieves real-time and accurate estimation of refrigerant inventory in refrigeration systems, while also possessing the advantages of simple operation, strong versatility, and strong anti-interference ability.

[0143] Based on the same inventive concept, this embodiment provides a refrigeration system. See also... Figure 2 The refrigeration system provided in this embodiment includes a refrigerant quantity estimation device for the refrigeration system provided in any of the above embodiments, as well as a compressor 1, a condenser 2, an expansion valve 3, an evaporator 4, a temperature sensor 811, and a pressure sensor 812. The compressor 1 is connected to the condenser 2, the condenser 2 is connected to the expansion valve 3, the expansion valve 3 is connected to the evaporator 4, and the evaporator 4 is connected to the compressor 1. The pressure sensor 812 and the temperature sensor 811 are located at the inlet of the expansion valve 3. The pressure sensor 812 and the temperature sensor 811 are respectively connected to the refrigerant quantity estimation device of the refrigeration system. In an optional embodiment, the refrigerant quantity estimation device of the refrigeration system can be integrated into the control unit 40.

[0144] It should be noted that, Figure 2 The diagram illustrates, for example, that 10 is the outdoor unit of the refrigeration system, 20 is the indoor unit, 30 is the data storage unit, 40 is the control unit, and 50 is the display unit. The control unit is connected to the sensor 8 and is used to acquire the pressure information at the expansion valve inlet and the refrigerant temperature information T1 at the expansion valve inlet collected by the sensor 8. The data storage unit 30 is connected to the control unit 40 and is used to store data such as the pressure information at the expansion valve inlet, the refrigerant temperature information T1 at the expansion valve inlet, and a correlation model between the subcooling degree and refrigerant inventory at the expansion valve inlet of the refrigeration system. The display unit 50 is connected to the control unit and is used to display the pressure information at the expansion valve inlet, the refrigerant temperature information T1 at the expansion valve inlet, the refrigerant inventory estimation results, and warning information. Warning information may include information such as insufficient or excessive refrigerant.

[0145] The refrigeration system provided in this embodiment includes the refrigerant inventory estimation device of the refrigeration system provided in any of the above embodiments, and has the beneficial effects of the refrigerant inventory estimation device of the refrigeration system provided in any of the above embodiments, which will not be described in detail here.

[0146] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method for estimating the refrigerant inventory in a refrigeration system, characterized in that, include: Obtain the temperature information of the refrigerant at the expansion valve inlet. and stress information ; Based on the pressure information at the expansion valve inlet and the temperature information of the refrigerant at the inlet of the expansion valve. Determine the subcooling degree at the inlet of the expansion valve. ; Based on calibration experiments, determine the subcooling at the inlet of the expansion valve of the refrigeration system. Model relating to refrigerant inventory; Based on the subcooling at the inlet of the expansion valve Based on the subcooling at the inlet of the expansion valve A model relating refrigerant inventory to estimate the refrigerant inventory is used.

2. The method according to claim 1, characterized in that, The pressure information based on the expansion valve inlet and the temperature information of the refrigerant at the inlet of the expansion valve. Determine the subcooling degree at the inlet of the expansion valve. ,include: Based on the pressure information at the expansion valve inlet Determine the pressure information at the inlet of the expansion valve. The corresponding saturation temperature of the refrigerant ; Based on the temperature information of the refrigerant at the inlet of the expansion valve With the saturation temperature The difference is used to determine the subcooling at the inlet of the expansion valve. .

3. The method according to claim 1 or 2, characterized in that, The subcooling degree at the inlet of the expansion valve of the refrigeration system is determined based on calibration experiments. Models relating to refrigerant inventory include: Set calibration conditions, which include ambient temperature, evaporator load, and compressor frequency; Different masses of refrigerant are charged into the refrigeration system, based on the designed refrigerant quantity. Initially, the refrigerant quantity was designed. The step size is the refrigerant volume to be designed. Termination, proceed with calibration experiments, and calculate the subcooling at the expansion valve inlet corresponding to the refrigerant quantity. And record the quality of the corresponding refrigerant inventory; Based on the mass of the refrigerant stock from the calibration experiment and the corresponding subcooling at the expansion valve inlet. The subcooling at the expansion valve inlet was obtained by fitting the data using the least squares method. A model relating to refrigerant inventory.

4. The method according to claim 3, characterized in that, The subcooling at the inlet of the expansion valve The model relating to refrigerant inventory is calculated using the following formula: ； in, Let a, b, and c represent the mass of the refrigerant in the refrigeration system, and a, b, and c represent model coefficients. This refers to the actual subcooling at the expansion valve inlet.

5. The method according to claim 1 or 2, characterized in that, The subcooling degree based on the expansion valve inlet Based on the subcooling at the inlet of the expansion valve The model relating to refrigerant inventory, after estimating the refrigerant inventory, also includes: Obtain the current operating status of the refrigeration system; Based on the difference between the current operating conditions and the calibration conditions, the subcooling at the expansion valve inlet is adjusted. The refrigerant inventory correlation model was modified to determine the subcooling at the expansion valve inlet after modification. Model relating to refrigerant inventory; Based on the corrected subcooling at the expansion valve inlet The model is related to the refrigerant inventory, based on the subcooling at the expansion valve inlet. Estimate the amount of refrigerant in the tank.

6. The method according to claim 5, characterized in that, The subcooling of the expansion valve inlet is adjusted based on the difference between the current operating condition and the calibration condition. The refrigerant inventory correlation model was modified to determine the subcooling at the expansion valve inlet after modification. Models relating to refrigerant inventory include: Obtain the ambient temperature under current operating conditions. Evaporator load and compressor frequency ; Based on the ambient temperature of the current operating conditions Ambient temperature under calibration conditions The difference between them, the evaporator load under the current operating conditions Evaporator load under rated operating conditions The difference between them, the compressor frequency under the current operating conditions Compressor frequency under rated operating conditions The difference between them corresponds to the subcooling at the inlet of the expansion valve. The subcooling degree at the expansion valve inlet is obtained by correcting the refrigerant inventory correlation model. A model relating to refrigerant inventory.

7. The method according to claim 6, characterized in that, The subcooling at the modified expansion valve inlet The model relating refrigerant inventory uses the following formula: ； in, This is an estimated value for the quality of the corrected refrigerant inventory. , , These are the ambient temperature, evaporator load, and compressor frequency under the rated operating conditions. , , This is the working condition correction factor.

8. The method according to any one of claims 1, 2, 6 or 7, characterized in that, The subcooling degree based on the expansion valve inlet Based on the subcooling at the inlet of the expansion valve The model relating to refrigerant inventory, after estimating the refrigerant inventory, also includes: Based on the difference between the refrigerant inventory and the first preset inventory threshold, a refrigerant shortage warning is triggered; Based on the difference between the refrigerant inventory and the second preset inventory threshold, a refrigerant overload warning is triggered; The first preset inventory threshold is less than the second preset inventory threshold.

9. A device for estimating the refrigerant inventory in a refrigeration system, characterized in that, include: The acquisition module is used to acquire the temperature information of the refrigerant at the inlet of the expansion valve. and stress information ; The subcooling calculation module is used to calculate the subcooling based on the pressure information at the inlet of the expansion valve. and the temperature information of the refrigerant at the inlet of the expansion valve. Determine the subcooling degree at the inlet of the expansion valve. ; The model determination module is used to determine the subcooling at the inlet of the expansion valve of the refrigeration system based on calibration experiments. Model relating to refrigerant inventory; The estimation module is used to estimate the subcooling at the inlet of the expansion valve. Based on the subcooling at the inlet of the expansion valve A model relating refrigerant inventory to estimate the refrigerant inventory is used.

10. A refrigeration system, characterized in that, include: The refrigerant inventory estimation device for the refrigeration system of claim 9, as well as the compressor, condenser, expansion valve, evaporator, temperature sensor and pressure sensor; The compressor is connected to the condenser, the condenser is connected to the expansion valve, the expansion valve is connected to the evaporator, and the evaporator is connected to the compressor; the pressure sensor and the temperature sensor are located at the inlet of the expansion valve; the pressure sensor and the temperature sensor are respectively connected to the refrigerant inventory estimation device of the refrigeration system.

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