Fixed-frequency chiller and temperature control method thereof

Abstract

The present application discloses a fixed-frequency chiller and a temperature control method thereof, which are applied to a temperature control system, wherein the fixed-frequency chiller comprises: a refrigerant system, a coolant system and a controller, wherein the refrigerant system comprises a first circuit for circulating the refrigerant and a compressor, a condenser, a first expansion valve and a heat exchanger sequentially arranged on the first circuit; the refrigerant system further comprises: a bypass line and a second expansion valve and an evaporator sequentially arranged on the bypass line; the bypass line is connected between the upstream of the first expansion valve and the downstream of the heat exchanger; the controller signal is connected to the first expansion valve and the second expansion valve, and controls the closing, opening and operation of the first expansion valve and the second expansion valve respectively. The present application can cope with heat fluctuations of a load (such as a data center server), dynamically adjust the refrigerant flow rate, and achieve temperature regulation within a certain control accuracy.

Description

Technical Field

[0001] The present application relates to the field of temperature control of chillers, and in particular to a constant-frequency chiller and a temperature control method thereof. Background Art

[0002] Chiller precision control is a crucial technology, primarily used in applications requiring precise temperature control, such as data centers and energy storage systems. In this technology, variable-frequency compressors utilize an inverter to adjust the motor speed, thereby altering the compressor's operating state to achieve energy savings and reduce consumption while maintaining high temperature control accuracy.

[0003] While variable-frequency compressors can achieve precise control under variable loads, they require a frequency converter (VFD). Currently, VFDs have high leakage currents, making them unsuitable for use in some industries. For example, in the medical industry, where some units come into direct contact with the human body, national standards require leakage currents of less than 10mA, with some units requiring even 0.5mA. This makes variable-frequency compressors unsuitable for this application.

[0004] In the process of implementing this application, the inventors discovered that the prior art has at least the following technical problems:

[0005] However, in some application scenarios, the load does not generate heat continuously, but generates heat intermittently, and the heat generated also changes dynamically. If a fixed-frequency compressor is used, if the heat generation of the load fluctuates, the fixed-frequency compressor will not be able to respond in time, resulting in a loss of control accuracy. Summary of the Invention

[0006] To this end, the present application proposes a fixed-frequency chiller and a temperature control method thereof, which can promptly respond to the heat generation fluctuation of the load in the chiller using a fixed-frequency compressor to achieve precise temperature control and effectively avoid loss of control accuracy.

[0007] In a first aspect, a temperature control method for a fixed-frequency chiller is provided, the fixed-frequency chiller comprising: a refrigerant system and a secondary refrigerant system, the refrigerant system comprising a first circuit for circulating refrigerant, and a compressor, a condenser, a first expansion valve, and a heat exchanger sequentially arranged on the first circuit;

[0008] The refrigerant system further includes: a bypass line and a second expansion valve and an evaporator sequentially arranged on the bypass line; the bypass line is connected between the upstream of the first expansion valve and the downstream of the heat exchanger;

[0009] The brine system includes a second circuit for circulating brine, the second circuit being connected to the heat exchanger and flowing through a heat source, wherein the refrigerant in the refrigerant system and the brine in the brine system perform heat exchange in the heat exchanger;

[0010] The temperature control method comprises:

[0011] Acquire a plurality of preset control intervals, wherein the plurality of control intervals include, in descending order, a first control interval, a second control interval, a third control interval, and a fourth control interval;

[0012] Obtaining a current control target temperature T0 of the brine or a current cooling capacity Q of the brine system, and determining the control interval corresponding to the current control target temperature T0 or the current cooling capacity Q;

[0013] When in the first control interval, controlling the first expansion valve to close, and setting the operating valve step of the second expansion valve to the maximum valve step;

[0014] When in the second control range, adjusting the operation valve step of the first expansion valve according to the superheat of the refrigerant, and increasing the operation valve step of the second expansion valve;

[0015] When in the third control range, adjusting the operation valve step of the first expansion valve according to the superheat of the refrigerant, and reducing the operation valve step of the second expansion valve;

[0016] When in the fourth control interval, the operating valve step of the first expansion valve is set to the maximum valve step, and the second expansion valve is closed.

[0017] According to one embodiment of the present application, the superheat of the refrigerant is obtained according to the difference between the temperature of the refrigerant outlet of the heat exchanger and the saturation temperature of the refrigerant, where the saturation temperature of the refrigerant is the temperature of saturated vapor at the pressure of the refrigerant outlet of the heat exchanger.

[0018] According to one embodiment of the present application, when the operating valve step of the first expansion valve is the maximum valve step or the operating valve step of the second expansion valve is the maximum valve step, the monitored superheat of the refrigerant is a positive number.

[0019] According to one embodiment of the present application, when the operating valve step of the first expansion valve is the maximum valve step or the operating valve step of the second expansion valve is the maximum valve step, the monitored superheat of the refrigerant is a positive number.

[0020] According to one embodiment of the present application, when the operation valve step of the first expansion valve is adjusted according to the superheat of the refrigerant, the operation valve step of the second expansion valve is controlled by PID regulation;

[0021] Alternatively, when the operating valve step of the first expansion valve is adjusted according to the superheat of the refrigerant, the operating valve step of the second expansion valve is increased to a preset second control interval valve step value, or the operating valve step of the second expansion valve is reduced to a preset third control interval valve step value.

[0022] According to one embodiment of the present application, when the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current control target temperature T0 of the refrigerant: the first control interval is [-b, -a], the second control interval is (-a, 0], the third control interval is (0, +a], and the fourth control interval is (+a, +b], where a and b are positive numbers and a<b.

[0023] According to one embodiment of the present application, when the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current cooling capacity Q of the refrigerant system: the first control interval is [Q1, Q2], the second control interval is (Q2, Q3], the third control interval is (Q3, Q4], and the fourth control interval is (Q4, Q5], where Q1<Q2<Q3<Q4<Q5.

[0024] According to one embodiment of the present application, the current cooling capacity Q is calculated according to the refrigerant temperature difference ΔT on both sides of the heat source according to the following formula: Q = ρ × v × C × ΔT;

[0025] Wherein, ρ represents the density of the refrigerant, v represents the volume flow rate of the refrigerant, C represents the specific heat capacity of the refrigerant, and ΔT represents the temperature difference of the refrigerant on both sides of the heat source; the volume flow rate v is measured by a flow meter installed in the second circuit; the refrigerant temperature difference ΔT is obtained by respectively measuring the refrigerant temperature entering the heat source and the refrigerant temperature flowing out of the heat source and then calculating the difference.

[0026] In a second aspect, a constant-frequency chiller comprises: a refrigerant system, a secondary refrigerant system, and a controller, wherein the refrigerant system comprises a first circuit for circulating refrigerant, and a compressor, a condenser, a first expansion valve, and a heat exchanger sequentially arranged on the first circuit;

[0027] The refrigerant system further includes: a bypass line and a second expansion valve and an evaporator sequentially arranged on the bypass line; the bypass line is connected between the upstream of the first expansion valve and the downstream of the heat exchanger;

[0028] The brine system includes a second circuit for circulating brine, the second circuit being connected to the heat exchanger and flowing through a heat source, wherein the refrigerant circulating in the refrigerant system and the brine circulating in the brine system perform heat exchange in the heat exchanger;

[0029] The controller signal is connected to the first expansion valve and the second expansion valve, and controls the closing, opening and operation of the first expansion valve and the second expansion valve respectively.

[0030] According to one embodiment of the present application, the first expansion valve and the second expansion valve are electronic expansion valves.

[0031] According to one embodiment of the present application, the evaporator is arranged next to the condenser, and the evaporator and the condenser perform heat exchange through air. The above one or more technical solutions in the embodiment of the present application have at least one of the following technical effects:

[0032] When the second expansion valve opens and the opening of the first expansion valve changes, the flow rate through the second expansion valve changes accordingly. The bypass line where the second expansion valve is located acts as a diverter to ensure that the refrigerant flows to the evaporator, preventing excessive condensing pressure from causing the unit to shut down.

[0033] The operating valve step of the first expansion valve of the present application is adjusted according to the deviation between the actual superheat of the refrigerant flowing out of the heat exchanger and the target superheat, and the operating valve step adjustment method of the first expansion valve is PID adjustment, which can cope with the heat fluctuations of the load, dynamically adjust the refrigerant flow, and can promptly respond to the heat generation fluctuations of the load in the chiller using a fixed-frequency compressor to achieve precise temperature control, effectively avoiding the loss of control accuracy.

[0034] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0036] Figure 1 This is a structural diagram of a fixed-frequency chiller provided in an embodiment of the present application;

[0037] Figure 2 1 is a flow chart of a temperature control method for a fixed-frequency chiller provided in an embodiment of the present application;

[0038] Figure 3 This is a schematic diagram of the control interval division of the control target temperature of the refrigerant in the temperature control method of the fixed-frequency chiller provided in an embodiment of the present application.

[0039] Reference numerals:

[0040] 10. Refrigerant system;

[0041] 100, first circuit; 110, compressor; 120, condenser; 130, first expansion valve; 140, heat exchanger;

[0042] 200, bypass line; 210, second expansion valve; 220, evaporator; 230, fan;

[0043] 20. Coolant system;

[0044] 21. Second circuit; 22. Circulation pump; 23. Heat source. DETAILED DESCRIPTION

[0045] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0046] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0047] The fixed-frequency chiller, its temperature control method, and temperature control system provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings through specific embodiments and their application scenarios.

[0048] like Figure 1 As shown, the constant-frequency chiller includes: a refrigerant system 10, a secondary refrigerant system 20 and a controller.

[0049] The refrigerant system 10 includes a first circuit 100 through which refrigerant circulates, and a first side (refrigerant side) of a compressor 110 , a condenser 120 , a first expansion valve 130 , and a heat exchanger 140 sequentially provided on the first circuit 100 .

[0050] The refrigerant system 10 further includes a bypass line 200 , and a second expansion valve 210 and an evaporator 220 sequentially disposed on the bypass line 200 ; an end of the bypass line 200 is connected to the compressor 110 .

[0051] The brine system 20 includes: a second circuit 21 for circulating brine, and a second side (brine side) of a heat exchanger 140, a circulation pump 22, and a heat source 23 sequentially arranged on the second circuit 21;

[0052] The controller signal is connected to the first expansion valve 130 and the second expansion valve 210 , and controls the closing, opening and operation of the first expansion valve 130 and the second expansion valve 210 , respectively.

[0053] In the above-mentioned constant-frequency chiller, the refrigerant may be HFC refrigerant, HC hydrocarbon refrigerant, etc.; the secondary coolant may be water, ethylene glycol solution, etc.

[0054] In the above embodiments of the present application, the first circuit 100 where the refrigerant flows through the compressor 110, the condenser 120, the first expansion valve 130, and the first side of the heat exchanger 140 is the main circuit of the refrigerant system 10; the bypass line 200 where the refrigerant flows through the second expansion valve 210 and the evaporator 220 is the parallel branch of the segment of the first circuit 100 where the first side of the first expansion valve 130 and the heat exchanger 140 are located.

[0055] Since the total flow rate through the main circuit is equal to the sum of the flow rates through the first expansion valve 130 and the second expansion valve 210, it can be seen that when the second expansion valve 210 is opened and the opening (valve step) of the first expansion valve 130 changes, the flow rate through the second expansion valve 210 changes accordingly. The bypass line 200 in which the second expansion valve 210 is located regulates the distribution of refrigerant flow by diverting the flow, thereby achieving precise temperature control in response to changes in the heating value of the heat source 23. Because the compressor 110 is a fixed-frequency compressor, when the operating valve step of the first expansion valve 130 or the second expansion valve 210 is the maximum valve step, the refrigerant entering the compressor 110 needs to have a certain degree of superheat to prevent the compressor 110 from being compressed with liquid, thereby ensuring the reliability of the compressor 110. In principle, as long as the refrigerant has a degree of superheat (the superheat of the refrigerant is a positive number), the compressor 110 can be protected. If the superheat is too low, the refrigerant cannot be completely vaporized, which may cause liquid hammer and damage to the compressor 110. If the superheat is too high, the cooling effect is reduced and the compressor 110 overheats. Therefore, by controlling the superheat of the refrigerant, the refrigerant flow rate can be more accurately adjusted, thereby controlling the cooling effect of the heat exchanger 140.

[0056] When first expansion valve 130 is not closed or is not operating at its maximum valve step, the valve step of first expansion valve 130 is adjusted based on the superheat of the refrigerant entering compressor 110. Furthermore, the controller uses PID control to adjust the valve step of second expansion valve 210, ensuring that the brine temperature entering heat source 23 is as close as possible to the brine's target temperature. This allows for dynamic adjustment of refrigerant flow to address heat fluctuations in heat source 23 (e.g., data center servers), achieving temperature regulation within a certain level of control accuracy.

[0057] like Figure 1 As shown, in some embodiments, the first expansion valve 130 and the second expansion valve 210 are electronic expansion valves. The specific working principles of the refrigerant system 10 and the secondary refrigerant system 20 are described below.

[0058] For the refrigerant system 10: the refrigerant becomes a high-temperature and high-pressure gas after being pressurized by the compressor 110. The high-temperature and high-pressure gas will become a high-temperature and high-pressure supercooled liquid when flowing through the condenser 120. The high-temperature and high-pressure supercooled liquid will be divided into two paths after passing through the first circuit 100; one path continues to flow along the first circuit 100, and is throttled and reduced in pressure to a low-pressure two-phase state after passing through the first expansion valve 130 and enters the heat exchanger 140, and the other path is throttled and reduced in pressure to a low-pressure two-phase state after passing through the second expansion valve 210 and enters the evaporator 220, and finally they merge together and enter the compressor 110 to complete a cycle.

[0059] For the brine system 20: the brine flowing through the heat source 23 enters the heat exchanger 140, and the heat of the brine is absorbed by the refrigerant in the heat exchanger 140. After the temperature of the brine is reduced, it passes through the circulation pump 22 and enters the heat source 23, completing a cycle.

[0060] In some embodiments, the refrigerant system 10 further includes a fan 230 .

[0061] The evaporator 220 is positioned adjacent to the condenser 120, and exchanges heat with the condenser 120 through air. Specifically, the condenser 120, evaporator 220, and fan 230 are arranged sequentially along a first direction, with the fan 230 accelerating the flow of air through the condenser 120 toward the evaporator 220. More specifically, the refrigerant passing through the second expansion valve 210 is throttled and reduced in pressure to a low-pressure two-phase refrigerant. The refrigerant then enters the evaporator 220, where it absorbs heat from the hot air passing through the condenser 120 and is converted into superheated refrigerant gas.

[0062] The present application also proposes a temperature control method for a fixed-frequency chiller unit with a variable heat source. The temperature control method can be applied to a terminal, and can be specifically executed by hardware or software in the terminal.

[0063] The terminal includes, but is not limited to, a portable communication device such as a mobile phone or tablet computer having a touch-sensitive surface (e.g., a touch screen display and / or a touch pad). It should also be understood that, in some embodiments, the terminal may not be a portable communication device, but a desktop computer having a touch-sensitive surface (e.g., a touch screen display and / or a touch pad).

[0064] In the following embodiments, a terminal including a display and a touch-sensitive surface is described. However, it should be understood that the terminal may include one or more other physical user interface devices such as a physical keyboard, a mouse, and a joystick.

[0065] The temperature control method for a fixed-frequency chiller provided in an embodiment of the present application may be performed by an electronic device or a functional module or functional entity in the electronic device that can implement the temperature control method. The electronic devices mentioned in the embodiment of the present application include but are not limited to mobile phones, tablet computers, computers, cameras, and wearable devices. The temperature control method provided in the embodiment of the present application is described below using an electronic device as an example of the execution subject.

[0066] The temperature control method for a fixed-frequency chiller provided in an embodiment of the present application sets different control intervals based on the current control target temperature T0 of the refrigerant or the current cooling capacity Q of the refrigerant system as the judgment standard, and achieves precise temperature control through the control methods corresponding to different control intervals.

[0067] The current control target temperature T0 of the brine is the brine temperature required to enter the heat source 23 obtained by the controller through calculation.

[0068] The current cooling capacity Q of the refrigerant system is calculated based on the refrigerant temperature difference ΔT on both sides of the heat source according to the following formula: Q = ρ × v × C × ΔT; wherein ρ represents the density of the refrigerant, v represents the volume flow rate of the refrigerant, C represents the specific heat capacity of the refrigerant, and ΔT represents the refrigerant temperature difference on both sides of the heat source; the volume flow rate v is measured by a flow meter arranged on the second circuit 21; the refrigerant temperature difference ΔT is obtained by respectively measuring the refrigerant temperature entering the heat source and the refrigerant temperature flowing out of the heat source and then calculating the difference.

[0069] like Figure 2 As shown, the temperature control method of the fixed-frequency chiller provided in the embodiment of the present application includes:

[0070] Step 310: Set the first control interval, the second control interval, the third control interval, and the fourth control interval in descending order;

[0071] Step 320: Determine whether the current control target temperature T0 of the brine or the current cooling capacity Q of the brine system is within the first control interval, the second control interval, the third control interval, or the fourth control interval.

[0072] The first control interval indicates that the heat source 23 has no cooling demand or the cooling capacity of the refrigerant system is too large; the second control interval indicates that the heat source 23 has a low cooling demand or the cooling capacity of the refrigerant system is too large; the third control interval indicates that the heat source 23 has a high cooling demand or the cooling capacity of the refrigerant system is too small; and the fourth control interval indicates that the heat source 23 has a high cooling demand or the cooling capacity of the refrigerant system is too small. According to the above division of control intervals from low to high, the controller controls the fixed-frequency chiller according to the following control logic:

[0073] When the current control target temperature T0 or the current cooling capacity Q is within the first control interval, the controller closes the first expansion valve 130 and sets the operating valve step of the second expansion valve 210 to the maximum valve step;

[0074] When the current control target temperature T0 or the current cooling capacity Q is within the second control range, the controller adjusts the operation valve step of the first expansion valve 130 according to the superheat of the refrigerant and increases the operation valve step of the second expansion valve 210;

[0075] When the current control target temperature T0 or the current cooling capacity Q is within the third control range, the controller adjusts the operation valve step of the first expansion valve 130 according to the superheat of the refrigerant and reduces the operation valve step of the second expansion valve 210;

[0076] When the current control target temperature T0 or the current cooling capacity Q is within the fourth control interval, the controller sets the operating valve step of the first expansion valve 130 to the maximum valve step and closes the second expansion valve 210 .

[0077] Here, the refrigerant superheat is calculated based on the difference between the refrigerant outlet temperature of heat exchanger 140 and the refrigerant saturation temperature, where the refrigerant saturation temperature is the temperature of saturated vapor at the pressure at the refrigerant outlet of the heat exchanger. As described above, a temperature sensor and a pressure sensor are installed on first circuit 100 corresponding to the refrigerant outlet of heat exchanger 140 to obtain the corresponding temperature and pressure values. The superheat of the refrigerant entering compressor 110 is calculated by calculating the difference between the saturated vapor temperature corresponding to the obtained temperature and pressure values. The refrigerant can be an HFC refrigerant, a hydrocarbon refrigerant, or the like. By consulting the thermodynamic property table for the refrigerant, the saturation temperature corresponding to the pressure value can be found based on the pressure value.

[0078] When the operating valve step of first expansion valve 130 or second expansion valve 210 reaches its maximum value (i.e., within the first control interval or the fourth control interval), the monitored refrigerant superheat is a positive value. More specifically, the refrigerant superheat must be kept within a reasonable range; otherwise, the reliability of compressor 110 may be affected. To ensure control accuracy, the adjustment rate of first expansion valve 130 and second expansion valve 210 may be increased.

[0079] When the current control target temperature T0 or the current cooling capacity Q is within the second control interval or the third control interval, the controller adjusts the operation valve step of the first expansion valve 130 according to the superheat of the refrigerant:

[0080] The controller adopts PID regulation to control the operating valve step of the second expansion valve 210, that is, the operating valve step of the second expansion valve 210 is a variable valve step value; or, the controller increases the operating valve step of the second expansion valve 210 to a preset second control interval valve step value, or the controller reduces the operating valve step of the second expansion valve 210 to a preset third control interval valve step value, that is, the operating valve step of the second expansion valve 210 is increased or decreased to a fixed valve step value.

[0081] like Figure 3 As shown, when the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current control target temperature T0 of the refrigerant, that is, the first control interval, the second control interval, the third control interval and the fourth control interval are temperature intervals, the first control interval is [-b, -a], the second control interval is (-a, 0], the third control interval is (0, +a], and the fourth control interval is (+a, +b], where a and b are positive numbers and a<b.

[0082] Here, the first control interval and the second control interval are temperature intervals below 0°C, and the third control interval and the fourth control interval are temperature intervals above 0°C.

[0083] When the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current cooling capacity Q of the refrigerant system: the first control interval is [Q1, Q2], the second control interval is (Q2, Q3], the third control interval is (Q3, Q4], and the fourth control interval is (Q4, Q5], where Q1<Q2<Q3<Q4<Q5.

[0084] Here, the first control interval, the second control interval, the third control interval and the fourth control interval are cooling capacity intervals that increase in sequence, and Q1, Q2, Q3, Q4 and Q5 are positive numbers that increase in sequence.

[0085] It should be noted that the brine system 20 includes a second circuit 21 for circulating brine, and a heat exchanger 140 , a circulation pump 22 and a heat source 23 sequentially arranged on the second circuit 21 .

[0086] In this step, the coolant can be water, ethylene glycol solution, etc. The coolant transfers heat from the heat source 23, and the temperature of the coolant directly reflects the heat release of the heat source 23.

[0087] During actual implementation, a mass flow meter can be set in the second loop 21 to detect the mass flow value of the refrigerant; temperature sensors can be set downstream of the heat source 23 and upstream of the heat source 23 to detect the outlet water temperature value downstream of the heat source 23 and the return water temperature value upstream of the heat source 23.

[0088] Of course, a flow meter may also be provided in the second circuit 21 to first detect the volume flow of the brine, and then obtain the mass flow by multiplying the volume flow by the fluid density of the brine.

[0089] It should be noted that, in this article, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be noted that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0090] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

[0091] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0092] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A temperature control method for a fixed-frequency chiller, characterized in that: The fixed-frequency chiller comprises: a refrigerant system and a secondary refrigerant system, wherein the refrigerant system comprises a first circuit for circulating the refrigerant and a compressor, a condenser, a first expansion valve and a heat exchanger sequentially arranged on the first circuit; The refrigerant system further includes: a bypass line and a second expansion valve and an evaporator sequentially arranged on the bypass line; the bypass line is connected between the upstream of the first expansion valve and the downstream of the heat exchanger; The brine system includes a second circuit for circulating brine, the second circuit being connected to the heat exchanger and flowing through a heat source, wherein the refrigerant in the refrigerant system and the brine in the brine system perform heat exchange in the heat exchanger; The temperature control method comprises: Acquire a plurality of preset control intervals, wherein the plurality of control intervals include, in descending order, a first control interval, a second control interval, a third control interval, and a fourth control interval; Obtaining a current control target temperature T0 of the brine or a current cooling capacity Q of the brine system, and determining the control interval corresponding to the current control target temperature T0 or the current cooling capacity Q; When in the first control interval, controlling the first expansion valve to close, and setting the operating valve step of the second expansion valve to the maximum valve step; When in the second control range, adjusting the operation valve step of the first expansion valve according to the superheat of the refrigerant, and increasing the operation valve step of the second expansion valve; When in the third control range, adjusting the operation valve step of the first expansion valve according to the superheat of the refrigerant, and reducing the operation valve step of the second expansion valve; When in the fourth control interval, the operating valve step of the first expansion valve is set to the maximum valve step, and the second expansion valve is closed.

2. The temperature control method according to claim 1, characterized in that: The superheat of the refrigerant is obtained according to the difference between the temperature of the refrigerant outlet of the heat exchanger and the saturation temperature of the refrigerant, which is the temperature of saturated vapor at the pressure of the refrigerant outlet of the heat exchanger.

3. The temperature control method according to claim 2, characterized in that: When the operating valve step of the first expansion valve is the maximum valve step or the operating valve step of the second expansion valve is the maximum valve step, the monitored superheat degree of the refrigerant is a positive number.

4. The temperature control method according to claim 2, characterized in that: When the operation valve step of the first expansion valve is adjusted according to the superheat of the refrigerant, the operation valve step of the second expansion valve is controlled by PID regulation; Alternatively, when the operating valve step of the first expansion valve is adjusted according to the superheat of the refrigerant, the operating valve step of the second expansion valve is increased to a preset second control interval valve step value, or the operating valve step of the second expansion valve is reduced to a preset third control interval valve step value.

5. The temperature control method according to claim 4, characterized in that: When the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current control target temperature T0 of the brine: the first control interval is [-b, -a], the second control interval is (-a, 0], the third control interval is (0, +a], and the fourth control interval is (+a, +b], where a and b are positive numbers and a<b.

6. The temperature control method according to claim 4, characterized in that: When the first control interval, the second control interval, the third control interval and the fourth control interval are set corresponding to the current cooling capacity Q of the refrigerant system: the first control interval is [Q1, Q2], the second control interval is (Q2, Q3], the third control interval is (Q3, Q4], and the fourth control interval is (Q4, Q5], where Q1<Q2<Q3<Q4<Q5.

7. The temperature control method according to claim 6, characterized in that: The current cooling capacity Q is calculated based on the refrigerant temperature difference ΔT on both sides of the heat source according to the following formula: Q = ρ × v × C × ΔT; Wherein, ρ represents the density of the refrigerant, v represents the volume flow rate of the refrigerant, C represents the specific heat capacity of the refrigerant, and ΔT represents the temperature difference of the refrigerant on both sides of the heat source; the volume flow rate v is measured by a flow meter installed in the second circuit; the refrigerant temperature difference ΔT is obtained by respectively measuring the refrigerant temperature entering the heat source and the refrigerant temperature flowing out of the heat source and then calculating the difference.

8. A fixed-frequency chiller for executing the temperature control method according to any one of claims 1 to 7, comprising: A refrigerant system, a secondary refrigerant system, and a controller, wherein the refrigerant system includes a first circuit for circulating refrigerant, and a compressor, a condenser, a first expansion valve, and a heat exchanger sequentially arranged on the first circuit; The refrigerant system further includes: a bypass line and a second expansion valve and an evaporator sequentially arranged on the bypass line; the bypass line is connected between the upstream of the first expansion valve and the downstream of the heat exchanger; The brine system includes a second circuit for circulating brine, the second circuit being connected to the heat exchanger and flowing through a heat source, wherein the refrigerant in the refrigerant system and the brine in the brine system perform heat exchange in the heat exchanger; The controller signal is connected to the first expansion valve and the second expansion valve, and controls the closing, opening and operation of the first expansion valve and the second expansion valve respectively.

9. The constant frequency chiller according to claim 8, characterized in that: The first expansion valve and the second expansion valve are electronic expansion valves.

10. The constant frequency chiller according to claim 8, characterized in that: The evaporator is arranged on one side of the condenser, and the evaporator and the condenser perform heat exchange through air.

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