Fixed-frequency water chilling unit and temperature control method thereof

Abstract

The invention discloses a fixed-frequency water chilling unit and a temperature control method thereof, the fixed-frequency water chilling unit is applied to a temperature control system, and the fixed-frequency water chilling unit comprises a refrigerant system, a secondary refrigerant system and a controller. The refrigerant system comprises a first loop for a refrigerant to circularly flow, and a compressor, a condenser, a first expansion valve and a heat exchanger which are sequentially arranged on the first loop; the refrigerant system further comprises a bypass pipeline, a second expansion valve and an evaporator, wherein the second expansion valve and the evaporator are sequentially arranged on the bypass pipeline. The bypass pipeline is bypassed between the upstream of the first expansion valve and the downstream of the heat exchanger; the controller is in signal connection with the first expansion valve and the second expansion valve and controls closing, opening and operation of the first expansion valve and the second expansion valve respectively. According to the invention, heat fluctuation of a load (such as a data center server) can be coped with, the refrigerant flow is dynamically adjusted, and temperature adjustment is realized within a certain control precision.

Description

Technical Field

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

[0002] Chiller precision control is an important technology, which is mainly used in occasions that require precise temperature control, such as data centers, energy storage, etc. In related technologies, variable frequency compressors use inverters to adjust the speed of the motor, thereby changing the operating state of the compressor body to achieve energy saving and consumption reduction while maintaining high temperature control accuracy.

[0003] Although variable frequency compressors can achieve precision control under variable loads, the variable frequency system requires the introduction of a frequency converter, which currently has a large leakage current and does not meet the requirements of some industries. For example, in the medical industry, some units are in direct contact with the human body. The national standard requires that the leakage current of the whole machine be less than 10mA, and some units even require 0.5mA. Variable frequency compressors do not meet the use conditions.

[0004] In the process of implementing this application, the inventors found that there are at least the following technical problems in the prior art:

[0005] However, in some application scenarios, the load does not generate heat continuously, but generates heat intermittently, and the heat generated also changes dynamically. When using a fixed-frequency compressor, if the heat generation of the load fluctuates, the fixed-frequency compressor cannot 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, wherein the fixed-frequency chiller comprises: a refrigerant system and a secondary refrigerant system, 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;

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

[0009] The brine system comprises a second circuit for circulating brine, the second circuit is connected to the heat exchanger and flows through a heat source, and 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 ascending 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, the first expansion valve is controlled to be closed, and the operation valve step of the second expansion valve is set to the maximum valve step;

[0014] When in the second control interval, 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 interval, 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, and the saturation temperature of the refrigerant is the temperature of saturated steam under 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 coolant: 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 an 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 coolant, v represents the volume flow rate of the coolant, C represents the specific heat capacity of the coolant, and ΔT represents the temperature difference of the coolant on both sides of the heat source; the volume flow rate v is measured by a flowmeter set on the second circuit; the coolant temperature difference ΔT is obtained by respectively measuring the coolant temperature entering the heat source and the coolant 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 comprises: a bypass pipe and a second expansion valve and an evaporator sequentially arranged on the bypass pipe; the bypass pipe is bypassed between the upstream of the first expansion valve and the downstream of the heat exchanger;

[0028] The brine system comprises a second circuit for circulating brine, the second circuit is connected to the heat exchanger and flows through a heat source, and 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 an 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 is opened and the opening of the first expansion valve changes, the flow through the second expansion valve changes accordingly. The bypass line where the second expansion valve is located ensures that the refrigerant flows to the evaporator through the function of diversion, preventing the condensing pressure from being too high and 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 fluctuation of the load, dynamically adjust the refrigerant flow rate, and can promptly respond to the heat generation fluctuation 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 apparent from the description below, or will be learned through the 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 is a structural schematic diagram of a fixed-frequency chiller provided in an embodiment of the present application;

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

[0038] Figure 3 It 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 the 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 pipe; 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 drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0046] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0047] The fixed-frequency chiller and 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 fixed-frequency chiller includes: a refrigerant system 10, a secondary coolant system 20 and a controller.

[0049] The refrigerant system 10 includes a first circuit 100 through which the refrigerant circulates, and a compressor 110 , a condenser 120 , a first expansion valve 130 , and a first side (refrigerant side) of a heat exchanger 140 sequentially disposed 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 which are 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 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] According to the fact that the total flow through the main circuit is equal to the sum of the flow through the first expansion valve 130 and the second expansion valve 210, it can be known that when the second expansion valve 210 is opened and the opening (valve step) of the first expansion valve 130 changes, the flow through the second expansion valve 210 changes accordingly. The bypass line 200 where the second expansion valve 210 is located plays a role in regulating the distribution of the refrigerant flow by diverting the flow, so as to achieve precision temperature control in response to the change in the heat generation of the heat source 23. Since 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, so that the compressor 110 will not be compressed with liquid, thereby ensuring the reliability of the compressor 110. In principle, as long as the refrigerant has superheat (the superheat of the refrigerant is a positive number), the protection of the compressor 110 can be achieved. If the superheat is too low, the refrigerant cannot be completely gasified, and liquid shock may damage the compressor 110; if the superheat is too high, the refrigeration effect is reduced and the compressor 110 is overheated. Therefore, by controlling the superheat of the refrigerant, the flow rate of the refrigerant can be more accurately adjusted, thereby controlling the refrigeration effect of the heat exchanger 140.

[0056] When the first expansion valve 130 is not closed or is not operated at the maximum valve step, the operating valve step of the first expansion valve 130 is adjusted according to the superheat of the refrigerant to enter the compressor 110, and the controller can use PID adjustment for the operating valve step of the second expansion valve 210, so that the temperature of the secondary coolant entering the heat source 23 is as close as possible to the control target temperature of the secondary coolant. In this way, the heat fluctuation of the heat source 23 (such as a data center server) can be coped with, the refrigerant flow rate can be dynamically adjusted, and temperature regulation can be achieved within a certain 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 coolant 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, and 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 loop 100; one path continues to flow along the first loop 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 coolant system 20: the coolant flowing through the heat source 23 enters the heat exchanger 140, and the heat of the coolant is absorbed by the refrigerant in the heat exchanger 140. After the temperature of the coolant is reduced, it enters the heat source 23 through the circulation pump 22 to complete a cycle.

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

[0061] The evaporator 220 is arranged beside the condenser 120, and the evaporator 220 performs heat exchange with the condenser 120 through air. Specifically, the condenser 120, the evaporator 220 and the fan 230 are arranged in sequence along the first direction, and the fan 230 accelerates the air to flow from the condenser 120 to the evaporator 220. More specifically, the refrigerant passing through the second expansion valve 210 is throttled and depressurized to become a low-pressure two-phase refrigerant, and enters the evaporator 220 to absorb the heat of the hot air passing through the condenser 120 and transform into a superheated refrigerant gas.

[0062] The present application also proposes a temperature control method for a fixed-frequency chiller unit as a 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 with 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 with a touch-sensitive surface (e.g., a touch screen display and / or a touch pad).

[0064] In the following various 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 executed 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 an 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 a judgment standard, and achieves precise temperature control through 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, setting 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 coolant or the current cooling capacity Q of the coolant system is within the first control interval, the second control interval, the third control interval or the fourth control interval.

[0072] Among them, 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 cooling demand of the heat source 23 is small or the cooling capacity of the refrigerant system is too large; the third control interval indicates that the cooling demand of the heat source 23 is too large or the cooling capacity of the refrigerant system is too small; the fourth control interval indicates that the cooling demand of the heat source 23 is large 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 operation 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 interval, 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 interval, 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 superheat of the refrigerant is obtained according to the difference between the temperature of the refrigerant outlet of the heat exchanger 140 and the saturation temperature of the refrigerant, wherein the saturation temperature of the refrigerant is the temperature of the saturated steam under the pressure of the refrigerant outlet of the heat exchanger. As described above, by setting a temperature sensor and a pressure sensor on the first circuit 100 according to the refrigerant outlet of the heat exchanger 140, the corresponding temperature value and pressure value can be obtained, and the superheat of the refrigerant to enter the compressor 110 can be obtained by performing a difference calculation based on the temperature value obtained and the temperature of the saturated steam corresponding to the pressure value obtained. The refrigerant can be an HFC refrigerant, an HC hydrocarbon refrigerant, etc. By querying the thermodynamic property table of the refrigerant, the saturation temperature value corresponding to the pressure value can be found according to the pressure value.

[0078] When the operation valve step of the first expansion valve 130 is the maximum valve step or the operation valve step of the second expansion valve 210 is the maximum valve step (i.e., in the first control interval or the fourth control interval), the monitored refrigerant superheat is a positive number. More specifically, at this time, the refrigerant superheat needs to be within a reasonable range, otherwise it will affect the reliability of the compressor 110. In order to ensure the control accuracy, the adjustment rate of the first expansion valve 130 and the second expansion valve 210 can be accelerated.

[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 coolant, 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 to correspond 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], wherein 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 which increase in sequence, and Q1, Q2, Q3, Q4 and Q5 are positive numbers which increase in sequence.

[0085] It should be noted that the brine system 20 includes a second loop 21 for circulating the brine, and a heat exchanger 140 , a circulation pump 22 and a heat source 23 sequentially arranged on the second loop 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 coolant, and then obtain the mass flow by multiplying the volume flow by the fluid density of the coolant.

[0089] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out 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 reverse 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 the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0091] In the description of this specification, the description with reference to the terms "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 schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[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 spirit 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 arranged in sequence on the first circuit; The refrigerant system further comprises: a bypass pipe and a second expansion valve and an evaporator sequentially arranged on the bypass pipe; the bypass pipe is bypassed between the upstream of the first expansion valve and the downstream of the heat exchanger; The brine system comprises a second circuit for circulating brine, the second circuit is connected to the heat exchanger and flows through a heat source, and 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 ascending 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, the first expansion valve is controlled to be closed, and the operation valve step of the second expansion valve is set to the maximum valve step; When in the second control interval, 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 interval, 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 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 coolant: 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 to correspond 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 according to 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 coolant, v represents the volume flow rate of the coolant, C represents the specific heat capacity of the coolant, and ΔT represents the temperature difference of the coolant on both sides of the heat source; the volume flow rate v is measured by a flow meter arranged on the second circuit; the coolant temperature difference ΔT is obtained by respectively measuring the coolant temperature entering the heat source and the coolant temperature flowing out of the heat source and then calculating the difference.

8. A fixed frequency chiller, comprising: A refrigerant system, a secondary refrigerant 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 arranged in sequence on the first circuit; The refrigerant system further comprises: a bypass pipe and a second expansion valve and an evaporator sequentially arranged on the bypass pipe; the bypass pipe is bypassed between the upstream of the first expansion valve and the downstream of the heat exchanger; The brine system comprises a second circuit for circulating brine, the second circuit is connected to the heat exchanger and flows through a heat source, and 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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