Refrigeration house defrosting control system and method based on frosting model

Abstract

The invention relates to a refrigeration house dynamic defrosting control system and method based on a frosting prediction model, and belongs to the field of refrigeration house refrigeration technologies and control. The system comprises a data acquisition module, a frosting prediction module, a frosting verification module and a dynamic defrosting module. The data acquisition module monitors evaporator inlet and outlet air inlet temperature, fin temperature, air pressure value and humidity change in real time. The frosting prediction module calculates the frosting rate and the frosting amount based on the inherent parameters and the real-time data of the refrigerator evaporator. The frosting prediction module verifies the frosting condition and corrects the frosting amount. And the dynamic defrosting control module adjusts the defrosting time according to the prediction result. According to the method, the frosting state is accurately predicted through a conventional sensor in combination with a lightweight algorithm, the defrosting time is optimized, and unnecessary defrosting operation is reduced, so that the energy consumption is reduced, the refrigeration efficiency of the refrigeration house is improved, the service life of equipment is prolonged, and intelligent and efficient operation of the refrigeration house is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of cold storage refrigeration technology and control. Specifically, it particularly relates to a cold storage defrosting control system and method based on a frosting model. Background Art

[0002] As a special type of building for constant temperature storage, a cold storage is an essential facility in industries such as food and medicine. Usually, the energy consumption of a cold storage can account for more than 70% of the energy consumption of the entire cold chain logistics enterprise, and the energy cost accounts for more than 30% of the enterprise's operating cost. In the refrigeration process, as the direct component for heat and cold conduction, the fins of the heat exchanger are almost inevitably frosted due to the water vapor and oxidation reaction of the goods themselves, as well as the water mist generated by the breathing of the cargo handlers. According to research, the COP value of the refrigeration system under frosting conditions can be reduced by more than 15% within 40 minutes, resulting in increased power consumption and even causing equipment failures, thereby increasing enterprise costs and wasting energy.

[0003] Traditional defrosting technologies mainly include timed defrosting and time-temperature defrosting methods. Such methods are simple, direct, and low-cost, and have a certain effect. However, the accuracy is relatively low, and there are often situations of defrosting without frost or incomplete defrosting. There are also high-precision methods in defrosting research, such as applying an electric current to the evaporator to analyze the change in the electric field, applying vibrations to the fins to analyze the change in amplitude, and an image detection method based on a neural network. Such methods require precise instruments and high installation and maintenance costs, and it is difficult to adapt to the changing cold storage conditions, so they are rarely applied in practice. Summary of the Invention

[0004] In view of the technical problems of high energy consumption, low efficiency, and lack of precise prediction existing in the traditional cold storage defrosting technology mentioned in the above background art, a cold storage dynamic defrosting control system and method based on a frosting prediction model are provided. By precisely predicting the frosting state and dynamically controlling the defrosting operation, the energy-saving and efficient operation of the cold storage is realized.

[0005] The technical means adopted by the present invention are as follows:

[0006] A cold storage defrosting control system based on a frosting model, comprising:

[0007] A data acquisition module, used for real-time monitoring of the temperature, humidity, air pressure value inside the cold storage, and the fin temperature of the evaporator;

[0008] A frosting prediction module, used for calculating the frosting rate and frosting amount through a frosting model according to the inherent parameters of the cold storage and real-time data;

[0009] A frosting verification module, used for verifying whether the calculation of the frosting amount is accurate and correcting the inaccurate frosting amount values;

[0010] The dynamic defrosting module is used to adjust the defrosting time according to the results of the frosting prediction module and the frosting verification module.

[0011] Further, the inherent parameters of the cold storage include: the specifications of the evaporator, the rated wind speed of the fan, and the air volume.

[0012] Further, the frosting rate m f calculated by the frosting model is as follows:

[0013] m f = m a (d h - d q ) = ρ a V a (d h - d q );

[0014] where m a represents the air mass flow rate; d h represents the moisture content of the gas inhaled by the evaporator fan; d q represents the moisture content of the gas discharged by the evaporator;

[0015]

[0016] where P sd represents the saturated water vapor partial pressure; φ represents the relative humidity; P s represents the saturated water vapor pressure.

[0017] Further, the formula for calculating the frosting amount by the frosting model is as follows:

[0018]

[0019] where M f represents the frosting amount; n represents the total time elapsed from the start of frosting calculation to the present; Δt represents the time interval.

[0020] Further, the frosting verification module verifies and corrects the accuracy of the calculated frosting amount through the difference between the cold storage temperature and the evaporator suction temperature. The formula is as follows:

[0021]

[0022] where ΔT(x) represents the difference between the temperature at the fan inlet and the evaporation temperature; T0 represents the difference between the cold storage temperature and the evaporation temperature under the frost-free condition; ΔT(x - 1) represents the difference between the temperature at the previous verification and the evaporation temperature; j represents the total number of corrections within one defrosting cycle; k p , k i , k d all represent gain coefficients.

[0023] Furthermore, the defrosting time is calculated by the following formula:

[0024]

[0025] where Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice; c represents the specific heat capacity of ice; -T d represents the difference between the current fin temperature and 0 °C.

[0026] The present invention also provides a cold storage defrosting control method based on a frosting model, including the following steps:

[0027] Step 1: Input the rated wind speed v a of the evaporator, the cross-sectional area S of the fan air duct, the calculation time interval Δt of the frosting rate, the electric heating defrosting power P df and efficiency η df , and the critical frost amount according to the equipment and requirements used by the user;

[0028] Step 2: Read the humidity value of the humidity sensor behind the fin and the value T of the temperature sensor close to the fin every Δt time, as well as the value P of the barometer on the side of the evaporator; use the value T d of the temperature sensor as the dew point temperature in the cold storage at this time, and obtain the saturated water vapor pressure P d in the cold storage at this moment and the critical humidity d ; compare the critical humidity value with the value read by the humidity sensor ; if if it means that the cold storage does not meet the prerequisite conditions for frosting at this time, that is, the cold storage will not frost at this time, and the system does not perform frosting calculation; until after a time step of Δt, the sensor reading operation is performed again; if it means that the cold storage meets the conditions required for frosting, that is, there is a frosting phenomenon in the cold storage; after the cold storage frosting condition is met, calculate the frosting rate and frosting amount of the cold storage;

[0029] Step 3: Calculate the air mass flow rate of the evaporator;

[0030] Step 4: Calculate the moisture content d q of the air at the outlet of the evaporator and the moisture content d h of the air at the inlet respectively;

[0031]

[0032] Among them, d represents the moisture content in g / kg; P s represents the saturated water vapor pressure; P sd represents the partial pressure of saturated water vapor; T represents the temperature at the air outlet;

[0033] Step 5. Calculate the frosting rate m f :

[0034] m f = m a (d h - d q );

[0035] Calculate the frosting amount M f , defined as:

[0036]

[0037] Among them, n represents the total time used from the start of calculating frosting to the present, Δt represents the time interval, and i represents the i-th moment.

[0038] Step 6. To avoid the situation that in the Δt moment during the frosting process, part of it meets the frosting conditions while part does not, resulting in a deviation in the calculation of the system frosting amount, verify the result of the frosting amount;

[0039] Step 7. After the calculation and verification of the frosting amount are completed, perform the defrosting operation.

[0040] Furthermore, the saturated water vapor pressure P d and the critical humidity in the cold storage are:

[0041]

[0042] Furthermore, the said Step 3 includes the following steps:

[0043] Step 31. Obtain the gas density ρ a , defined as:

[0044]

[0045] Among them, ρ d represents the dry air density, ρ m represents the wet air density, with the unit of kg / m 3 ; P d represents the partial pressure of dry air; R d represents the dry air gas constant, taking 287 J / (kg*K); R m represents the water vapor gas constant, taking 461.5 J / (kg*K), and the two constant values remain unchanged; T represents the value of the probe-type temperature sensor behind the evaporator fin;

[0046] Step 32: Calculate the air mass flow rate m at this moment a , which is defined as:

[0047] m a = v a ρ a S;

[0048] where S represents the cross-sectional area of the fan air duct; v a represents the wind speed; m a represents the air mass flow rate, with the unit kg / s.

[0049] Furthermore, step 7 includes the following steps:

[0050] Step 71: Calculate the frosting time t df :

[0051]

[0052] where Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice; c represents the specific heat capacity of ice; -T d represents the difference between the current fin temperature and 0°C;

[0053] Step 72: Perform defrosting treatment by means of segmented heating; the segmented heating is divided into a preheating stage, a main heating stage, and a post-treatment stage, with the heating powers being 10%, 80%, and 30% of the rated power respectively, and the running times being one-fourth, one-half, and one-fourth of the total defrosting time respectively;

[0054] Step 73: Check whether the defrosting is successful; judge whether the defrosting is successful by checking whether the temperature T d+1 read by the temperature sensor close to the fin reaches 0°C after the defrosting ends; if T d+1 ≥ -0.5°C, it means that the frost has been removed or there is a small amount of residue, and there is no need to perform defrosting treatment again, and directly enter the next frosting calculation; if -2°C < T d+1 < -0.5°C, the defrosting operation can be restarted for treatment; if the temperature is too low, such as T d+1 ≤ -2°C, the machine needs to be stopped to check for faults;

[0055] Step 74: Calculate the additional defrosting time as:

[0056]

[0057] where t add represents the additional defrosting time; Td Indicates the fin surface temperature before the start of the system defrost operation.

[0058] Compared with the prior art, the present invention has the following advantages:

[0059] The cold storage dynamic defrost control system and method based on the frosting prediction model provided by the present invention have the following significant advantages compared with the prior art: By predicting the frosting amount and accurately triggering the defrost operation, it avoids the ineffective energy consumption caused by inaccurate problems in traditional timed or threshold defrosting. The system parameters are adjustable, widely adapting to various frosting environments. The present invention uses conventional sensors and combines lightweight algorithms, greatly reducing the hardware cost while ensuring accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0061] Figure 1 It is the basic flowchart of the control system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0063] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0064] Such as Figure 1As shown in the figure, the present invention provides a dynamic defrosting control system for cold storage based on a frosting prediction model, which uses conventional sensors and combines lightweight algorithms to accurately predict the frosting state and optimize the defrosting timing, aiming to achieve a better defrosting effect even in scenarios with low equipment performance. The defrosting method adopted in the present invention is electric heating defrosting. The sensors used include temperature and humidity sensors and pressure sensors. Generally, a probe-type temperature and humidity sensor is placed about 20 cm before and after the evaporator, led out from the ceiling, with an error range of ±2%RH and ±0.5°C. A wireless patch-type temperature sensor is placed on the evaporator fins, close to the evaporator fins, with an error range of ±0.5°C. The pressure sensor is placed on the side of the evaporator, with an error range of ±5 hPa. To correct the errors and outliers of the sensor data, median filtering is used when reading the sensor data, with a window size of 5, and the median value is output after sorting the data within the window by size.

[0065] The system includes:

[0066] A data acquisition module for real-time monitoring of the temperature, humidity, air pressure value in the cold storage and the fin temperature of the evaporator;

[0067] A frosting prediction module for calculating the frosting rate and frosting amount through a frosting model according to the inherent parameters of the cold storage and real-time data; the inherent parameters of the cold storage include: the specifications of the evaporator and the rated wind speed and air volume of the fan. The formula for calculating the frosting rate m f is:

[0068] m f = m a (d h - d q ) = ρ a V a (d h - d q );

[0069] Among them, m a represents the air mass flow; d h represents the moisture content of the gas inhaled by the evaporator fan; d q represents the moisture content of the gas discharged by the evaporator;

[0070]

[0071] Among them, P sd represents the saturated water vapor partial pressure; φ represents the relative humidity; P s represents the saturated water vapor pressure.

[0072] The formula for calculating the frosting amount through the frosting model is:

[0073]

[0074] Among them, M f represents the amount of frosting; n represents the total time elapsed from the start of frosting calculation to the present; Δt represents the time interval.

[0075] The frosting verification module is used to verify whether the calculation of the amount of frosting is accurate and correct the value of the inaccurate amount of frosting; the frosting verification module verifies the accuracy and correction of the calculation of the amount of frosting through the difference between the cold storage temperature and the suction temperature of the evaporator. The formula is:

[0076]

[0077] Among them, ΔT(x) represents the difference between the temperature at the air inlet of the fan and the evaporation temperature; T0 represents the difference between the cold storage temperature and the evaporation temperature under the frost-free condition; ΔT(x - 1) represents the difference between the temperature and the evaporation temperature during the previous verification; j represents the total number of corrections within a defrosting cycle; k p 、k i 、k d all represent gain coefficients.

[0078] The dynamic defrosting module is used to adjust the defrosting time according to the results of the frosting prediction module and the frosting verification module. The defrosting time is calculated by the following formula:

[0079]

[0080] Among them, Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice; c represents the specific heat capacity of ice; -T d represents the difference between the current fin temperature and 0°.

[0081] The present invention also includes a cold storage defrosting control method based on a frosting model, including the following steps:

[0082] Step 1. Input the rated wind speed v a 、the cross-sectional area S of the fan air duct, the time interval Δt for calculating the frosting rate, the electric heating defrosting power P df and efficiency η df 、the critical amount of frost according to the equipment and requirements used by the user.

[0083] The time interval Δt is recommended to be set to 5 - 15 minutes to balance accuracy and computational load. When the water vapor of the goods is high, Δt is lowered, and vice versa. The critical frost amount can be set according to experience or in the following way: When the system runs for the first time and reaches the set temperature, after the preconditions for frosting are met, continuously calculate and accumulate the frost amount, and at the same time detect the change in the difference between the cold storage temperature and the evaporation temperature when the valve opening is 50%. After exceeding the maximum value of 4 degrees Celsius within the normal range, start defrosting and record the total accumulated frost amount at this time. 85% of the total frost amount is recorded as the critical total frost amount M 临界 To ensure accurate defrosting under different working conditions (such as equipment aging, changes in environmental temperature and humidity), dynamic calibration is required, and the calibration period is 30 days. Use formula (1) to establish a linear regression relationship between ΔT and frost amount, defined as:

[0084]

[0085] where ΔT 实测 represents the difference between the temperature at the inlet of the internal fan and the temperature of the evaporator in the cold storage sensor data. ΔT 基准 is the difference between the temperature at the inlet of the fan and the temperature of the evaporator under normal frost-free conditions. The specific value can be referred to in Table 1.

[0086] Step 2: Read the humidity value of the humidity sensor behind the fin and the value T of the temperature sensor close to the fin every Δt time, d and the value P of the barometer on the side of the evaporator; Take the value T d of the temperature sensor as the dew point temperature in the cold storage at this time, and obtain the saturated water vapor pressure P d and the critical humidity

[0087]

[0088] Compare the critical humidity value with the value read by the humidity sensor If then the cold storage does not meet the preconditions required for frosting at this time, that is, the cold storage will not frost at this time, and the system does not perform frost calculation. Wait until after the Δt time step and then read the sensor operation; If then it means that the cold storage meets the conditions required for frosting, that is, there is a frosting phenomenon in the cold storage; After the cold storage frosting condition is met, calculate the cold storage frosting rate and frosting amount.

[0089] Step 3: Calculate the air mass flow rate of the evaporator to obtain the gas density ρ a at this time, defined as:

[0090]

[0091] where ρ d represents the dry air density, and ρ m represents the moist air density, with the unit of kg / m 3 ; P d represents the partial pressure of dry air; R d represents the dry air gas constant, taking 287 J / (kg*K); R m represents the water vapor gas constant, taking 461.5 J / (kg*K), and the two constant values remain unchanged; T represents the value of the probe-type temperature sensor behind the evaporator fins;

[0092] Then calculate the air mass flow rate m a , which is defined as:

[0093] m a = v a ρ a S;

[0094] where S represents the cross-sectional area of the fan air duct; v a represents the wind speed; m a represents the air mass flow rate, with the unit of kg / s.

[0095] Step 4: Calculate the moisture content d q of the air at the outlet of the evaporator and the moisture content d h of the air at the inlet respectively;

[0096]

[0097] where d represents the moisture content with the unit of g / kg; P s represents the saturated water vapor pressure; P sd represents the partial pressure of saturated water vapor; T represents the temperature at the air outlet; this calculation needs to be performed twice, namely at the outlet and the inlet, for the next step.

[0098] Step 5: Calculate the frosting rate m f at this moment:

[0099] m f = m a (d h - d q );

[0100] In the theoretical case, is used to calculate the total frosting amount, but the values transmitted by the sensors are usually discrete in time, and there are differences in the response speed and reading interval of each sensor. On the other hand, the calculation amount is relatively large, so this method is not applicable. After improvement, the frosting amount M f at this moment is calculated, which is defined as:

[0101]

[0102] Among them, n represents the total time elapsed from the start of frost formation calculation to the current time, Δt represents the time interval, and i represents the i-th moment. For example, if n is one hour and Δt is 5 minutes, then there are time periods. That is, the sensor collects data every 5 minutes, calculates the frost formation rate, and then multiplies this rate by 300 to obtain the amount of frost formed within these 5 minutes. The total amount of frost in one hour is obtained by accumulating the different amounts of frost in 12 time periods. This calculation method is more convenient and has less computational complexity. In practice, Δt can be adjusted to different parameters according to different precisions.

[0103] Step 6: To avoid the situation where in the Δt time period during the frost formation process, part of it satisfies the frost formation condition while part does not, resulting in a deviation in the system's calculation of the amount of frost, it is necessary to verify the result of the amount of frost. The present invention uses the degree of similarity between the temperature in the cold storage and the suction temperature of the evaporator to judge the frost formation condition.

[0104] After the frost layer reaches a certain thickness, it hinders the air from flowing through the evaporator fins, resulting in a decrease in air flow and a reduction in the heat load of the evaporator. The evaporation amount of the refrigerant in the evaporator decreases, and the evaporation pressure drops, thereby causing the evaporation temperature to decrease. As the frost layer thickens, the downward trend of the evaporation temperature will gradually accelerate. The temperature in the cold storage is controlled to remain constant, so the temperature difference between the two gradually increases. Therefore, the difference between the temperature and the evaporator can roughly reflect whether there is a frost formation condition. During verification, the valve opening is controlled to operate at 50% for 1 minute, and the average value of the difference between the temperature and the evaporation temperature is read. Compare it with the normal range to obtain the difference from the maximum value of the normal temperature difference, and use discrete PID control to correct the amount of frost, defined as:

[0105] M f修正 = M f + M pid ;

[0106]

[0107] Among them, ΔT represents the difference between the temperature at the inlet of the fan and the evaporation temperature; T0 represents the difference between the temperature in the cold storage and the evaporation temperature under the frost-free condition, and the reference value is shown in Table 1; ΔT(x) represents the difference between the temperature at the inlet of the fan and the evaporation temperature during this verification; ΔT(x - 1) represents the difference between the temperature and the evaporation temperature during the previous verification; j is the total number of corrections within a defrosting cycle; k p 、k i 、k d represent the proportional gain, integral gain, and derivative gain respectively. The gain size can be adjusted in a fuzzy adaptive manner. When |ΔT| > 2°C, increase k p , k d for a quick response. When |ΔT| < 1°C, increase k iTo eliminate the steady-state error.

[0108] Table 1 Reference Table of the Difference between the Warehouse Temperature and the Evaporation Document under the Frost-Free Condition

[0109] <![CDATA[Temperature difference T0 between the reservoir temperature and the evaporation temperature]]> Relative humidity Type of stored products and storage 4-5 90％-95％ Fresh vegetables without packaging 6-7 80％-85％ Packaged meat and fresh vegetables 7-9 65％-80％ Pharmaceuticals, melons and packaged products for short-term storage 10-12 50％-65％ Butchering room, beer warehouse, film warehouse, etc.

[0110] To cope with the interference caused by equipment failures (such as refrigerant leakage), a reference item of the fan current fluctuation can be added at the same time. If ΔT increases abnormally and the fan current drops by more than 10%, it is determined as the frosting condition. If ΔT is abnormal but the fan current remains unchanged, it is judged as a fault and the fault diagnosis operation is triggered.

[0111] Step 7: After the frost amount calculation and verification are completed, the defrosting processing operation is carried out. First, calculate the frosting time t through formula (12) df , defined as:

[0112]

[0113] Among them, Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice, and a fixed value of 334 kJ / kg can be taken under normal pressure and normal state; c represents the specific heat capacity of ice, and a fixed value of 1.09×10 -3 m 3 / kt. The influence of air pressure change on the latent heat of fusion and specific heat capacity of ice is extremely small, so fixed values can be used; -T d represents the difference between the current fin temperature and 0°.

[0114] In extreme cases, such as when RH>95% and T<-30°C and continuous operation exceeds ten minutes, the system triggers the auxiliary defrosting mode, Δt is reduced to 1 minute, and the critical frost amount is increased to 90% of the limit frost amount. The defrosting adopts segmented heating. The segmented heating is divided into a preheating stage, a main heating stage, and a post-treatment stage. The heating powers are 10%, 80%, and 30% of the rated power respectively. The running times are one-fourth, one-half, and one-fourth of the total defrosting time respectively, so as to avoid thermal stress damage to the evaporator.

[0115] After the defrosting operation is carried out according to the calculated defrosting time, it is necessary to check whether the defrosting is successful. The method of the present invention is to check whether the temperature T d+1 read by the temperature sensor close to the fin reaches 0 degrees after the defrosting is completed. T d+1 ≥ -0.5°C indicates that the frost has been removed or there is a small amount of residue, and there is no need to carry out defrosting treatment again, and directly enter the next frosting calculation. If -2°C < T d+1 < -0.5°C, the defrosting operation can be restarted for treatment. If the temperature is too low, such as T d+1If the temperature is ≤ -2°C, the machine needs to be stopped to check for faults.

[0116] Calculate the additional defrosting time, defined as:

[0117]

[0118] where t add represents the additional defrosting time; T d represents the fin surface temperature before the start of the system defrosting operation. That is, the T value in step 7. d value.

[0119] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0120] In the above embodiments of the present invention, the descriptions of each embodiment have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0121] In several embodiments provided by the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only illustrative. For example, the division of the units can be a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the couplings or direct couplings or communication connections shown or discussed with each other can be through some interfaces. The indirect couplings or communication connections of the units or modules can be in electrical or other forms.

[0122] The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0123] In addition, in each embodiment of the present invention, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated units can be implemented in the form of hardware or in the form of software functional units.

[0124] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), mobile hard disks, magnetic disks, or optical discs that can store program codes.

[0125] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cold storage defrosting control system based on a frosting model, characterized in that, Including: A data acquisition module for real-time monitoring of the temperature, humidity, air pressure value inside the cold storage and the fin temperature of the evaporator; A frosting prediction module for calculating the frosting rate and the amount of frost formed through a frosting model based on the inherent parameters of the cold storage and real-time data; A frosting verification module for verifying whether the calculated amount of frost formed is accurate and correcting the value of the inaccurate amount of frost formed; A dynamic defrosting module for adjusting the defrosting time according to the results of the frosting prediction module and the frosting verification module.

2. The defrosting control system for a cold storage based on a frosting model according to claim 1, wherein The inherent parameters of the cold storage include: the specifications of the evaporator and the rated wind speed and air volume of the fan.

3. The defrosting control system for a cold storage based on a frosting model according to claim 1, characterized in that, The frosting rate m calculated by the frosting model f has the following formula: m f = m a (d h - d q ) = ρ a V a (d h - d q ); where m a represents the air mass flow rate; d h represents the moisture content of the gas inhaled by the evaporator fan; d q represents the moisture content of the gas discharged from the evaporator; Among them, P sd represents the partial pressure of saturated water vapor; φ represents the relative humidity; P s represents the saturated water vapor pressure.

4. A defrosting control system for a cold storage based on a frosting model according to claim 1, characterized in that, The formula for calculating the amount of frost formed through the frosting model is: Among them, M f represents the frosting amount; n represents the total time elapsed from the start of frosting calculation to the present; Δt represents the time interval.

5. The defrosting control system for a cold storage based on a frosting model according to claim 1, characterized in that, The frosting verification module verifies the accuracy of the calculated amount of frost formed and makes corrections through the difference between the cold storage temperature and the suction temperature of the evaporator. The formula is: Among them, ΔT(x) represents the difference between the temperature at the air inlet of the fan and the evaporation temperature; T0 represents the difference between the temperature in the frost-free condition and the evaporation temperature; ΔT(x - 1) represents the difference between the temperature at the previous verification and the evaporation temperature; j represents the total number of corrections within a defrosting cycle; k p , k i , k d all represent gain coefficients.

6. The defrosting control system for a cold storage based on a frosting model according to claim 1, wherein The defrosting time is calculated through the following formula: Among them, Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice; c represents the specific heat capacity of ice; -T d represents the difference between the current fin temperature and 0°C.

7. A defrosting control method for a cold storage based on a frosting model, which applies the system described in any one of claims 1-6, characterized in that, Including the following steps: Step 1. Input the rated wind speed v of the evaporator, the cross-sectional area S of the fan air duct, the time interval Δt for calculating the frosting rate, the electric heating defrosting power P a , and the efficiency η df of the equipment used by the user and the requirements df ; and the critical frost amount Step 2: Read the humidity value of the humidity sensor behind the fin every Δt time and the value T of the temperature sensor close to the fin d , as well as the value P of the barometer on the side of the evaporator; Take the value T of the temperature sensor d as the dew point temperature in the cold storage at this time, and obtain the saturated water vapor pressure P d and the critical humidity Compare the critical humidity value with the value read by the humidity sensor If it means that the cold storage does not meet the prerequisite conditions for frosting at this time, that is, the cold storage will not frost at this time, and the system does not perform frosting calculation; until after Δt time step, read the sensor operation again; If it means that the cold storage meets the frosting conditions, that is, there is a frosting phenomenon in the cold storage; After the frosting conditions of the cold storage are met, calculate the frosting rate and frosting amount of the cold storage; Step 3: Calculate the air mass flow rate of the evaporator; Step 4: Calculate the moisture content d of the air at the outlet of the evaporator q and the moisture content d of the air at the inlet h ; where d represents the moisture content in g / kg; P s represents the saturated water vapor pressure; P sd represents the partial pressure of saturated water vapor; T represents the temperature at the tuyere; Step 5: Calculate the frosting rate m at this moment f : m f = m a (d h - d q ); Calculate the frosting amount M at this moment f , which is defined as: Where n represents the total time elapsed from the start of calculating the frost formation to the present, Δt represents the time interval, and i represents the i-th moment; Step 6: To avoid the situation where part of the frost formation conditions are met and part are not met within the Δt moment during the frost formation process, resulting in a deviation in the calculated amount of frost in the system, verify the result of the amount of frost formed; Step 7: After the calculation and verification of the amount of frost are completed, perform the defrosting processing operation.

8. A defrosting control method for a cold storage based on a frosting model according to claim 7, characterized in that, The saturated water vapor pressure P in the cold storage d and the critical humidity are as follows:

9. A defrosting control method for a cold storage based on a frosting model according to claim 7, characterized in that, The said Step 3 includes the following steps: Step 31: Obtain the gas density ρ at this moment a , which is defined as: Among them, ρ d represents the dry air density, and ρ m represents the wet air density, with the unit of kg / m 3 ; P d represents the partial pressure of dry air; R d represents the dry air gas constant, taking 287 J / (kg*K); R m represents the water vapor gas constant, taking 461.5 J / (kg*K), and the two constant values remain unchanged; T represents the value of the probe-type temperature sensor behind the evaporator fin; Step 32: Calculate the air mass flow rate m at this moment a , which is defined as: Among them, S represents the cross-sectional area of the fan air duct; v a represents the wind speed; m a represents the air mass flow rate, with the unit of kg / s.

10. A defrosting control method for a cold storage based on a frosting model according to claim 7, characterized in that, The said Step 7 includes the following steps: Step 71, calculate the frosting time t df : Among them, Q df represents the heat required for defrosting, η df represents the electric heating efficiency, P df represents the electric heating power, L represents the latent heat of fusion of ice; c represents the specific heat capacity of ice; -T d represents the difference between the current fin temperature and 0°C; Step 72: Perform defrosting treatment through segmented heating; the segmented heating is divided into a preheating stage, a main heating stage, and a post-treatment stage, with heating powers of 10%, 80%, and 30% of the rated power respectively, and running times of one-fourth, one-half, and one-fourth of the total defrosting time respectively; Step 73, check whether defrosting is successful; by using the temperature sensor that checks and is close to the fin, after the defrosting ends, read the temperature T d+1 to determine whether defrosting is successful; if T d+1 ≥ -0.5°C, it means that the frost has been removed or there is a small amount remaining, and there is no need to perform defrosting treatment anymore, and directly enter the next frosting calculation; if -2°C < T d+1 < -0.5°C, then the defrosting operation can be restarted for treatment; if the temperature is too low, such as T d+1 ≤ -2°C, then the machine needs to be stopped to check for faults; Step 74: Calculate the additional defrosting time as: where t add represents the additional defrosting time; T d represents the fin surface temperature before the start of the system defrosting operation.

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