Control method for a refrigeration system

Abstract

The application provides a control method of a refrigeration system, comprising: when powered on, determining whether the ambient temperature Th fluctuates when the first preset condition or the second preset condition is met; if not, controlling the frequency of the variable frequency compressor to decrease by △F1; wherein the first preset condition is that the exhaust pressure P at the exhaust port of the variable frequency compressor fluctuates twice within t1 time from the starting moment; the second preset condition is that P accumulatively fluctuates three times within t2 time from the starting moment; t1 < t2; the fluctuation range of the exhaust pressure P is P > P0 + △P or P < P0 - △P, P0 is the exhaust pressure value at the starting moment, and △P = 0.1-0.3 MPa; the fluctuation range of the ambient temperature Th is Th > Th0 + 2 DEG C or Th < Th0 - 2 DEG C, Th0 is the ambient temperature at the starting moment, and the control method is simple and convenient, and the variable frequency compressor can be controlled to operate in a stable state.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration equipment, and particularly to a control method for a refrigeration system. Background Art

[0002] With the development of technology and the improvement of living standards, refrigeration devices are increasingly widely used in daily life and household life, and more attention is paid to the preservation of frozen foods. Through research, a low-temperature environment below -40°C is beneficial to the preservation of frozen foods.

[0003] However, when the refrigeration device realizes a low-temperature environment below -40°C, at different ambient temperatures or evaporation temperatures, the ratio of the refrigerant to the compressor oil in the evaporator and the condenser is different. When the ambient temperature or evaporation temperature is relatively high, the proportion of the compressor oil in the condenser increases, resulting in an increase in the flocculation temperature of the compressor oil in the refrigerant-compressor oil mixture fluid, so that the compressor oil at the capillary outlet is prone to flocculation, leading to capillary blockage and affecting the refrigeration effect of the refrigeration system. Summary of the Invention

[0004] To solve the above technical problems, an object of the present invention is to provide a control method for a refrigeration system to solve the problem that the compressor oil at the capillary outlet of the existing refrigeration system is prone to flocculation and block the capillary when realizing a cryogenic low-temperature environment below -40°C.

[0005] To achieve one of the above object of the present invention, an embodiment of the present invention provides a control method for a refrigeration system, including:

[0006] When powered on, when the first preset condition or the second preset condition is satisfied, it is judged whether the ambient temperature Th fluctuates;

[0007] If not, the frequency of the variable-frequency compressor is controlled to decrease by △F1;

[0008] Wherein, the first preset condition is that the exhaust pressure P at the exhaust port of the variable-frequency compressor fluctuates twice within the time t1 since the starting moment; the second preset condition is that P fluctuates three times in total within the time t2 since the starting moment; t1 < t2; the fluctuation range of the exhaust pressure P is P > P0 + △P or P < P0 - △P, P0 is the exhaust pressure value at the starting moment, △P = 0.1 - 0.3 MPa; the fluctuation range of the ambient temperature Th is Th > Th​​0 + 2°C or Th < Th​​0 - 2°C, Th​​0 is the ambient temperature at the starting moment.

[0009] As a further improvement of one embodiment of the present invention, the control method further includes: when the first preset condition or the second preset condition is met, if the ambient temperature Th fluctuates, it is determined whether the rate of change θ of the exhaust pressure P with the ambient temperature Th is greater than a preset value θ0, where θ = P / Th; if so, the frequency of the variable frequency compressor is controlled to decrease by ΔF1.

[0010] As a further improvement of one embodiment of the present invention, when the ambient temperature Th is 35-45℃, θ0 = 0.05-0.1 MPa / ℃; when the ambient temperature Th is 25-35℃, θ0 = 0.04-0.08 MPa / ℃; when the ambient temperature Th is 15-25℃, θ0 = 0.03-0.07 MPa / ℃; and when the ambient temperature Th is 5-15℃, θ0 = 0.02-0.06 MPa / ℃.

[0011] As a further improvement of one embodiment of the present invention, the control method further includes: if P reaches a preset value P0 within a time period t2 from the start time, then the frequency of the variable frequency compressor is controlled to decrease by ΔF2, wherein ΔF2 < ΔF1.

[0012] As a further improvement of one embodiment of the present invention, the starting time is the start-up time of the variable frequency compressor, or the time when the temperature Tr of the storage room rises to Tr0, where Tr0 = Tset + 5℃, and Tset is the set temperature of the storage room.

[0013] As a further improvement of one embodiment of the present invention, the control method further includes: controlling the condenser fan to start when the power is on; and controlling the variable frequency compressor to start at an initial frequency F1 when the exhaust pressure P at the exhaust port of the variable frequency compressor drops to a preset value P0.

[0014] As a further improvement of one embodiment of the present invention, after the variable frequency compressor is started, the variable frequency compressor is controlled to uniformly increase its frequency to F2.

[0015] As a further improvement of one embodiment of the present invention, the control method further includes: if the exhaust temperature T at the exhaust port of the variable frequency compressor reaches a preset value T0 after time t2 from the start time, the variable frequency compressor is controlled to stop, and the frequency of the variable frequency compressor at this moment is recorded as F3.

[0016] As a further improvement of one embodiment of the present invention, the control method further includes: after a preset shutdown time t3, controlling the variable frequency compressor to restart at an initial frequency F1, and uniformly increasing the frequency to F4 within a preset time t4, wherein F4 = F3 - 5Hz.

[0017] As a further improvement of one embodiment of the present invention, the refrigeration system includes a variable frequency compressor, a condenser, a capillary tube, and an evaporator connected in sequence. The refrigeration system further includes a heat exchanger comprising a high-temperature heat exchange tube and a low-temperature heat exchange tube arranged in parallel and exchanging heat with each other. The inlet of the high-temperature heat exchange tube is connected to the condenser, and its outlet is connected to the capillary tube. The inlet of the low-temperature heat exchange tube is connected to the evaporator, and its outlet is connected to the return port of the variable frequency compressor.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The control method of the refrigeration system of the present invention monitors the fluctuation of the discharge pressure P at the discharge port of the variable frequency compressor when it is powered on, and controls the frequency of the variable frequency compressor to decrease while eliminating the influence of the ambient temperature Th. On the one hand, it can reduce the discharge volume and the suction volume, so as to increase the evaporation pressure, reduce the pressure difference at both ends of the capillary tube and the flow rate of refrigerant in the capillary tube, and thus increase the temperature at the outlet of the capillary tube, thereby preventing the compressor oil at the outlet of the capillary tube from flocculating and avoiding capillary tube blockage that affects the refrigeration efficiency. On the other hand, it can control the operating pressure of the refrigeration system within its tolerable range to ensure the normal operation of the refrigeration system. Attached Figure Description

[0019] Figure 1 This is a logic flowchart of a control method for a refrigeration system according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of a refrigeration circuit according to an embodiment of the present invention. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings.

[0022] In the various illustrations of this invention, for ease of illustration, certain dimensions of structures or parts may be enlarged relative to other structures or parts; therefore, only the basic structure of the subject matter of this invention is used to illustrate the invention.

[0023] It should be understood that although the terms first, second, etc., may be used in this document to describe various elements or structures, the objects being described should not be limited by these terms. These terms are only used to distinguish these objects from one another.

[0024] See Figure 1 An embodiment of the present invention provides a control method for a refrigeration system, comprising:

[0025] When powered on, if the first or second preset condition is met, determine whether the ambient temperature Th fluctuates.

[0026] If not, then control the frequency of the variable frequency compressor to decrease by ΔF1;

[0027] Among them, the first preset condition is that the exhaust pressure P at the exhaust port of the variable-frequency compressor fluctuates twice within the time t1 since the starting moment; the second preset condition is that P fluctuates three times in total within the time t2 since the starting moment; t1 < t2; the fluctuation range of the exhaust pressure P is P > P0 + △P or P < P0 - △P, where P0 is the exhaust pressure value at the starting moment, and △P = 0.1 - 0.3 MPa; the fluctuation range of the ambient temperature Th is Th > Th0 + 2°C or Th < Th0 - 2°C, where Th0 is the ambient temperature at the starting moment.

[0028] The fluctuation here refers to the change amplitude of the index value relative to the value at the starting moment exceeding the preset value. Specifically, the fluctuation range of the exhaust pressure P is P > P0 + 0.2 MPa or P < P0 - 0.2 MPa, that is, the fluctuation of the exhaust pressure P is defined as the situation where the difference between the value of the exhaust pressure at least at a certain moment and the value at the starting moment is greater than 0.2 MPa; and the fluctuation range of the ambient temperature Th is Th > Th0 + 2°C or Th < Th0 - 2°C, that is, the fluctuation of the ambient temperature Th is defined as the situation where the difference between the value of the ambient temperature at least at a certain moment and the value at the starting moment is greater than 2°C.

[0029] Define that from the moment when the change amplitude of the index value relative to the value at the starting moment exceeds the preset value, the continuous change until this change amplitude is first less than the preset value is one fluctuation. Specifically, one fluctuation of the exhaust pressure P is defined as: starting from the moment when P - P0 > 第1页 共3页0.2 MPa, continuously changing until P - P0 < 0.2 MPa appears for the first time; or, starting from the moment when P - P0 < -0.2 MPa, continuously changing until P - P0 > -0.2 MPa appears for the first time. One fluctuation of the ambient temperature Th is defined as: starting from the moment when Th - Th0 > 2°C, continuously changing until Th - Th0 < 2°C appears for the first time; or, starting from the moment when Th - Th0 < -2°C, continuously changing until Th - Th0 > -2°C appears for the first time.

[0030] By monitoring the fluctuation of the exhaust pressure P at the exhaust port of the variable-frequency compressor when powering on, and excluding the influence of the ambient temperature Th, the frequency of the variable-frequency compressor is controlled to decrease. On the one hand, the exhaust volume and the suction volume can be reduced, the evaporation pressure can be increased, the pressure difference at both ends of the capillary and the refrigerant flow rate in the capillary can be reduced, and then the temperature at the outlet of the capillary can be increased, thereby preventing the flocculation of the pressure oil at the outlet of the capillary and avoiding the capillary blockage from affecting the refrigeration efficiency. On the other hand, the operating pressure of the refrigeration system can be controlled within the range it can bear to ensure the normal operation of the refrigeration system.

[0031] Preferably, ΔF1 = 10Hz, which can prevent excessive frequency changes of the variable frequency compressor 1 from causing drastic changes in exhaust pressure, thereby preventing the variable frequency compressor from exceeding its tolerance range.

[0032] Preferably, the starting time is the start-up time of the variable frequency compressor, or the time when the temperature Tr of the storage chamber rises to Tr0, where Tr0 = Tset + 5℃, and Tset is the set temperature of the storage chamber. After power-on and the variable frequency compressor starts, or when the temperature of the storage chamber rises to more than 5℃ above the set temperature, the discharge temperature and discharge pressure of the variable frequency compressor will change drastically in order to meet the cooling and temperature requirements, causing the refrigeration system to operate unstablely. By controlling the stage where the discharge pressure is prone to drastic fluctuations, the operating pressure of the refrigeration system can be prevented from exceeding its tolerable range.

[0033] Preferably, t1 = 1h and t2 = 6h. By monitoring and controlling the refrigeration operation during the initial power-on period, the drastic fluctuations in the exhaust temperature of the inverter compressor during the initial power-on period can be avoided, thereby protecting the inverter compressor.

[0034] Furthermore, the control methods for the refrigeration system also include:

[0035] If the ambient temperature Th fluctuates when the first or second preset condition is met, it is determined whether the rate of change θ of the exhaust pressure P with the ambient temperature Th is greater than the preset value θ0, where θ = P / Th;

[0036] If so, the frequency of the variable frequency compressor is reduced by ΔF1.

[0037] In this way, after considering the correlation between ambient temperature Th and exhaust pressure P, the variable frequency compressor can be adjusted according to the abnormal fluctuations in exhaust pressure. This not only takes into account the impact of changes in ambient temperature Th on the operation of the refrigeration system, but also avoids misleading information and provides correct guidance.

[0038] Preferably, in this embodiment, the refrigerant used in the refrigeration system includes a first working substance and a second working substance, wherein the mass percentage of the first working substance is 10-60%, the mass percentage of the second working substance is 40-90%, the first working substance is one of R170, R1150, R23 or R14, and the second working substance is any one of R290, R600, R600a, R134a, R1234fy or R1234ze.

[0039] When a refrigerant composed of the two working fluids is applied to a refrigeration system by adjusting their ratio, it can not only meet the system's requirements for the amount of flammable refrigerant charged, but also maintain a temperature of -90℃ to -40℃ within the storage compartment, achieving optimal preservation of frozen foods stored there. In practical applications, the mass percentage of the two working fluids can be adjusted according to the refrigeration unit's volume, ambient temperature, and application scenario to achieve the desired preservation effect.

[0040] More preferably, the first working refrigerant is R170 or R1150, and the second working refrigerant is any one of R290, R600, and R600a, with the first working refrigerant accounting for 20-50% by mass and the second working refrigerant accounting for 50-80% by mass. Such a binary refrigerant mixture can not only meet the temperature requirement of -90℃ to -40℃, but is also environmentally friendly and has important environmental protection significance.

[0041] More preferably, the first working refrigerant is R23 or R14, and the second working refrigerant is any one of R290, R600, and R600a. The mass percentage of the first working refrigerant is 10-40%, and the mass percentage of the second working refrigerant is 60-90%. Such a binary refrigerant mixture can not only meet the temperature requirement of -90℃ to -40℃, but also has flame retardant effect, improving the safety of the refrigeration system operation.

[0042] More preferably, the first working refrigerant is R170 or R1150, and the second working refrigerant is any one of R134a, R1234fy, and R1234ze, with the first working refrigerant accounting for 10-40% by mass and the second working refrigerant accounting for 60-90% by mass. Such a binary refrigerant mixture not only meets the temperature requirement of -90℃ to -40℃, but also has flame-retardant properties, improving the safety of the refrigeration system operation.

[0043] More preferably, the first working refrigerant is R23 or R14, and the second working refrigerant is any one of R134a, R1234fy, and R1234ze, with the first working refrigerant having a mass percentage of 20-50% and the second working refrigerant having a mass percentage of 50-80%. Such a binary refrigerant mixture not only meets the temperature requirement of -90℃ to -40℃, but also has flame-retardant properties, improving the safety of the refrigeration system operation.

[0044] In other embodiments, the refrigerant may also be configured to include a low-temperature refrigerant, a medium-temperature refrigerant, and a high-temperature refrigerant, wherein the mass percentage of the low-temperature refrigerant is 20-40%, the mass percentage of the medium-temperature refrigerant is 20-40%, the mass percentage of the high-temperature refrigerant is 40-60%, the low-temperature refrigerant is any one of R23, R14, R170, and R1150, the medium-temperature refrigerant is any one of R134a, R290, and R1270, and the high-temperature refrigerant is any one of R600 and R600a.

[0045] The refrigerant, composed of the above three working fluids, can be mixed in proportions to achieve a lower evaporation temperature and pressure while meeting the requirements for the amount of combustible refrigerant charged into the refrigeration system. When applied to a refrigeration system, this reduces the compressor's compression ratio, minimizing throttling and heat transfer losses, thus improving refrigeration efficiency and performance. This allows the storage compartment temperature to reach -90℃ to -40℃, which is beneficial for preserving frozen foods such as meat and fish. Furthermore, it lowers the technical requirements for the compressor. In practical applications, the mass percentages of the three working fluids can be adjusted based on the refrigeration unit's volume, ambient temperature, and application scenario to achieve the desired preservation effect.

[0046] When using the above-mentioned mixed refrigerant, the impact of ambient temperature fluctuations on the refrigeration system varies under different ambient temperatures.

[0047] Specifically, when the ambient temperature Th is 35–45℃, θ0 = 0.05–0.1 MPa / ℃;

[0048] When the ambient temperature Th is 25–35℃, θ0 = 0.04–0.08 MPa / ℃;

[0049] When the ambient temperature Th is 15–25℃, θ0 = 0.03–0.07 MPa / ℃;

[0050] When the ambient temperature Th is 5–15℃, θ0 = 0.02–0.06 MPa / ℃.

[0051] Furthermore, the control method for the refrigeration system also includes:

[0052] If P reaches the preset value P0 within a time interval t2 from the start time, the frequency of the variable frequency compressor is controlled to decrease by ΔF2, where ΔF2 < ΔF1.

[0053] P0 is the upper limit threshold of the discharge pressure that the variable frequency compressor can withstand. In other words, at the initial stage of power-on, by monitoring the discharge pressure, the discharge pressure P is controlled below the upper limit threshold, thereby ensuring the normal operation of the refrigeration system.

[0054] Preferably, ΔF2 = 5Hz, which can prevent excessive frequency changes of the variable frequency compressor from causing drastic changes in exhaust pressure, thereby preventing the variable frequency compressor from exceeding its operating range.

[0055] Furthermore, the control method further includes:

[0056] When powered on, the condenser fan starts.

[0057] When the exhaust pressure P at the exhaust port of the variable frequency compressor drops to a preset value P0, the variable frequency compressor is controlled to start at the initial frequency F1.

[0058] The moment when the variable frequency compressor starts at the initial frequency F1 is the aforementioned starting moment.

[0059] When powered on, the condenser fan is started first to quickly reduce the exhaust temperature and pressure. Once the exhaust pressure drops to the preset value P0, the inverter compressor is then started. This avoids excessive exhaust pressure at power-on, which could lead to unstable operation of the refrigeration system and damage to it.

[0060] Preferably, the initial frequency F1 = Fmin ~ Fmin + 10Hz, where Fmin is the minimum set frequency of the variable frequency compressor. Starting the variable frequency compressor at a lower frequency F1 can further reduce the pressure on the compressor during power-on and is also beneficial for subsequent frequency increases of the compressor.

[0061] Furthermore, the control method of the refrigeration system also includes: after the variable frequency compressor starts, controlling the variable frequency compressor to uniformly increase the frequency to F2, thereby avoiding drastic fluctuations in exhaust pressure.

[0062] Furthermore, the control method of the refrigeration system also includes: after time t2 from the start time, if the exhaust temperature T at the exhaust port of the variable frequency compressor reaches a preset value T0, then the variable frequency compressor is controlled to stop, and the frequency of the variable frequency compressor at this moment is recorded as F3. This can protect the variable frequency compressor and prevent it from being damaged.

[0063] Furthermore, the control method for the refrigeration system also includes: after a preset shutdown time t3, controlling the variable frequency compressor to restart at an initial frequency F1, and then uniformly increasing the frequency to F4 within a preset time t4, where F4 = F3 - 5Hz. By implementing shutdown protection for the variable frequency compressor and controlling it to restart at a low frequency and uniformly increase the frequency, while simultaneously controlling the operating frequency of the variable frequency compressor after frequency increase, it is beneficial to control the discharge pressure of the variable frequency compressor and ensure the normal operation of the refrigeration system.

[0064] Preferably, t4 = 5 min. This ensures the frequency ramp-up rate of the inverter compressor and avoids instability in the refrigeration system caused by an excessively high frequency ramp-up rate.

[0065] Furthermore, the control method for the refrigeration system can be applied to a refrigeration device including a cabinet and a door. The cabinet has a storage compartment, and the door is used to open or close the storage compartment. The refrigeration device also includes a refrigeration system located within the cabinet and supplying cooling to the storage compartment. Specifically, the refrigeration device can be configured as a freezer, refrigerator, etc., to meet the needs of different users and different application scenarios.

[0066] See Figure 2 The refrigeration system includes a refrigeration circuit 100 and a refrigerant located in the refrigeration circuit 100. The refrigeration circuit 100 includes a variable frequency compressor 1, a condenser 2, a capillary tube 3, and an evaporator 4 connected in sequence. The refrigeration circuit 100 also includes a heat exchanger 5, which includes a high-temperature heat exchange tube 51 and a low-temperature heat exchange tube 52 connected in parallel and exchanging heat with each other. The inlet of the high-temperature heat exchange tube 51 is connected to the condenser 2, and its outlet is connected to the capillary tube 3. The inlet of the low-temperature heat exchange tube 52 is connected to the outlet of the evaporator 4, and its outlet is connected to the return port of the variable frequency compressor 1. The high-temperature heat exchange tube 51 and the low-temperature heat exchange tube 52 are named for ease of distinction. Comparatively, the temperature of the refrigerant in the high-temperature heat exchange tube 51 is higher than the temperature of the refrigerant in the low-temperature heat exchange tube 52.

[0067] This refrigeration system utilizes heat exchange through high-temperature heat exchange tube 51 and low-temperature heat exchange tube 52. On the one hand, the refrigerant undergoes heat exchange and cooling before entering the evaporator 4. On the other hand, the refrigerant undergoes heat exchange and heating before entering the variable frequency compressor 1 after leaving the evaporator 4. By making reasonable use of the refrigeration system's own heat exchange, the pressure between the outlet of the variable frequency compressor 1 and the inlet of the capillary tube 3 is controlled within the range that the variable frequency compressor 1 can withstand during stable operation, which is beneficial for achieving low-temperature refrigeration below -40℃. However, it is more prone to oil condensation leading to capillary tube blockage. Applying this control method to this refrigeration system can more effectively solve the problem of capillary tube blockage caused by oil condensation at the capillary tube outlet, thereby ensuring refrigeration efficiency.

[0068] Specifically, the high-temperature heat exchange tube 51 and the low-temperature heat exchange tube 52 can be arranged side by side or wrapped together to achieve heat exchange.

[0069] Furthermore, the refrigeration device also includes a condenser fan located near the condenser 2, which can blow air to the condenser 2 to dissipate heat from the condenser 2.

[0070] Furthermore, the refrigeration circuit 100 also includes a dryer filter 6 located at the outlet of the condenser 2 to remove moisture and impurities mixed in the refrigerant. The outlet of the dryer filter 6 is connected to the high-temperature heat exchange tube 51.

[0071] In this way, the refrigerant is compressed into a high-temperature, high-pressure refrigerant gas by the variable frequency compressor 1. The refrigerant gas enters the condenser 2 and condenses into a gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant enters the heat exchanger 5 and exchanges heat with the low-temperature heat exchanger 52 in the high-temperature heat exchanger tube 51 and is further condensed. Then, the refrigerant enters the capillary tube 3 for throttling and pressure reduction. Then, the refrigerant enters the evaporator 4 and exchanges heat to form a gas-liquid two-phase refrigerant, that is, the refrigerant is in a gas-liquid two-phase state at the outlet of the evaporator 4. This gas-liquid two-phase refrigerant passes through the low-temperature heat exchanger 52 and exchanges heat with the high-temperature heat exchanger 51, causing the refrigerant in the high-temperature heat exchanger 51 to cool down and condense. The refrigerant is in a gaseous state at the outlet of the low-temperature heat exchanger 52. Then, the refrigerant returns to the variable frequency compressor 1.

[0072] By applying the above-mentioned refrigerant to the refrigeration system of the present invention, the pressure of the pipeline between the variable frequency compressor 1 and the capillary tube 41 in the refrigeration circuit 100 after stable operation can be controlled to less than 1.6 MPa. This solves the problem of excessive pressure when the low-temperature refrigerant is used alone in the refrigeration system, reduces the requirements on the compressor, ensures the feasibility of the refrigeration system, and enables the refrigeration device to achieve a low-temperature storage environment of -90℃ to -40℃.

[0073] Furthermore, the temperature Tl of the refrigerant at the outlet of condenser 2 is greater than the ambient temperature Th, and the temperature difference between the two is ΔT = Tl - Th, where ΔT ≤ 3℃. In this embodiment, ΔT is below 3℃, which is much smaller than the 8℃ or lower in the prior art.

[0074] Compared with the prior art, the control method of the refrigeration system provided by the present invention has the following advantages: The present invention monitors the fluctuation of the discharge pressure P at the discharge port of the variable frequency compressor when powered on, and controls the frequency of the variable frequency compressor to decrease after eliminating the influence of the ambient temperature Th. On the one hand, it can reduce the discharge volume and the suction volume, so as to increase the evaporation pressure, reduce the pressure difference at both ends of the capillary tube and the flow rate of refrigerant in the capillary tube, and thus increase the temperature at the outlet of the capillary tube, thereby preventing the compressor oil at the outlet of the capillary tube from flocculating and avoiding capillary tube blockage that affects the refrigeration efficiency. On the other hand, it can control the operating pressure of the refrigeration system within its tolerable range to ensure the normal operation of the refrigeration system.

[0075] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0076] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a refrigeration system, characterized in that, The refrigeration system includes a variable-frequency compressor, a condenser, a capillary tube, and an evaporator connected in sequence. The refrigeration system further includes a heat exchanger, which includes a high-temperature heat exchange tube and a low-temperature heat exchange tube arranged in parallel and exchanging heat with each other. The inlet of the high-temperature heat exchange tube is connected to the condenser and its outlet is connected to the capillary tube. The inlet of the low-temperature heat exchange tube is connected to the evaporator and its outlet is connected to the suction port of the variable-frequency compressor; The control method includes: When power is on, when the first preset condition or the second preset condition is satisfied, it is judged whether the ambient temperature Th fluctuates; If not, the frequency of the variable-frequency compressor is controlled to decrease by △F1; Among them, the first preset condition is that the exhaust pressure P at the exhaust port of the variable-frequency compressor fluctuates twice within the time t1 since the starting moment; the second preset condition is that P accumulatively fluctuates three times within the time t2 since the starting moment; t1 < t2; the fluctuation range of the exhaust pressure P is P > P0 + △P or P < P0 - △P, P0 is the exhaust pressure value at the starting moment, and △P = 0.1 - 0.3 MPa; the fluctuation range of the ambient temperature Th is Th > Th0 + 2°C or Th < Th0 - 2°C, and Th0 is the ambient temperature at the starting moment.

2. The control method for the refrigeration system according to claim 1, characterized in that, The control method further includes: When the first preset condition or the second preset condition is satisfied, if the ambient temperature Th fluctuates, it is judged whether the change rate θ of the exhaust pressure P with respect to the ambient temperature Th is greater than the preset value θ0, where θ = P / Th; If so, the frequency of the variable-frequency compressor is controlled to decrease by △F1.

3. The control method for the refrigeration system according to claim 2, characterized in that, When the ambient temperature Th is 35 - 45°C, θ0 = 0.05 - 0.1 MPa / °C; When the ambient temperature Th is 25 - 35°C, θ0 = 0.04 - 0.08 MPa / °C; When the ambient temperature Th is 15 - 25°C, θ0 = 0.03 - 0.07 MPa / °C; When the ambient temperature Th is 5 - 15°C, θ0 = 0.02 - 0.06 MPa / °C.

4. The control method for the refrigeration system according to claim 1, characterized in that, The control method further includes: Within the time t2 since the starting moment, if P reaches the upper limit threshold of the exhaust pressure that the variable-frequency compressor can withstand, the frequency of the variable-frequency compressor is controlled to decrease by △F2, where △F2 < △F1.

5. The control method for the refrigeration system according to claim 1, characterized in that, The starting moment is the starting moment of the variable-frequency compressor, or the moment when the temperature Tr of the storage compartment rises to Tr0, where Tr0 = Tset + 5°C, and Tset is the set temperature of the storage compartment.

6. The control method for the refrigeration system according to claim 5, characterized in that, The control method further includes: When power is on, the condensing fan is controlled to start; When the exhaust pressure P at the exhaust port of the variable-frequency compressor drops to the upper limit threshold of the exhaust pressure that the variable-frequency compressor can withstand, the variable-frequency compressor is controlled to start at the initial frequency F1.

7. The control method for the refrigeration system according to claim 6, characterized in that, After the variable-frequency compressor starts, the variable-frequency compressor is controlled to increase its frequency uniformly to F2.

8. The control method for the refrigeration system according to claim 1, characterized in that, The control method further includes: After the time t2 since the starting moment, if the exhaust temperature T at the exhaust port of the variable-frequency compressor reaches the preset value T0, the variable-frequency compressor is controlled to stop, and the frequency of the variable-frequency compressor at this moment is recorded as F3.

9. The control method for the refrigeration system according to claim 8, characterized in that, The control method further includes: After a preset shutdown time t3, the variable frequency compressor is controlled to restart at an initial frequency F1, and then uniformly increases the frequency to F4 within a preset time t4, where F4 = F3 - 5Hz.

Images