Pre-cooling type liquid helium temperature zone throttling refrigerator and optimization method, device and medium thereof

Abstract

The optimization method for a pre-cooled liquid helium temperature-range throttling refrigerator disclosed herein relates to the field of cryogenic and refrigeration engineering. It includes: for a predetermined operating condition, taking the smaller of the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the cooling temperature as the maximum cooling capacity obtainable per unit mass of working fluid under the predetermined operating condition; assuming that if there exists a case where the minimum isothermal enthalpy difference between the high and low pressure working fluids equals the maximum cooling capacity between the cooling temperature and the lowest pre-cooling temperature, then M = 1; otherwise, determining whether adding a throttling stage can obtain the maximum cooling capacity: assuming each intermediate stage has a high pressure, taking the intersection of the enthalpy-temperature lines of the working fluid at stage l and stage l+1 as the high pressure outlet state of heat exchanger l in the JT unit, obtaining a new high pressure working fluid enthalpy-temperature line; if there exists a case where the minimum isothermal enthalpy difference between the high and low pressure working fluids equals the maximum cooling capacity, then taking and outputting each intermediate stage high pressure; otherwise, continuing to determine whether adding a throttling stage can obtain the maximum cooling capacity.

Description

Technical Field

[0001] This disclosure relates to the field of cryogenic and refrigeration engineering technology, specifically to a pre-cooled liquid helium temperature-range throttling refrigerator and its optimization method, apparatus and medium. Background Technology

[0002] Liquid helium temperature cryogenics are key components in various fields, such as electromagnetic wave detection, gravitational wave detection, superconducting magnet and detector cooling, and pre-cooling for sub-Kelvin level refrigeration. There are three main types of liquid helium temperature cryogenics: Gifford-McMahon (GM) cryogenics, pulse tube cryogenics, and pre-cooled throttling cryogenics (Joule-Thomson, JT). Compared to GM and pulse tube cryogenics, pre-cooled JT cryogenics offer higher cooling efficiency, can transmit cooling power over longer distances, and have no moving cryogenic parts, thus isolating vibration and shielding against electromagnetic interference.

[0003] Most JT refrigerators currently under development employ single-stage throttling. Existing research on maximizing the Coefficient of Performance (COP) of JT refrigerators indicates that, for a given pre-cooling temperature, there exists an optimal high pressure that maximizes the cooling capacity at the liquid helium temperature. Theoretical analysis and experimental results confirm that adding a single stage of throttling can increase the cooling capacity and thus improve the COP of the JT refrigerator. However, existing research on multi-stage throttling only discusses a few fixed intermediate pressures and does not perform global optimization of the operating conditions. The maximum cooling capacity under predetermined operating conditions and the path to obtaining the highest COP remain unclear. Summary of the Invention

[0004] This disclosure aims to at least partially address one of the technical problems in the related art.

[0005] To address this, this disclosure proposes a pre-cooled liquid helium temperature-range throttling refrigerator and its optimization method, apparatus, and medium. Specifically, it proposes a multi-stage throttling method to obtain the highest COP for the helium working fluid throttling refrigerator. For throttling refrigerators using helium-4 or helium-3 working fluids, with determined pre-cooling temperature, cooling temperature, and cycle high and low pressures, the method proposed in this disclosure can determine the maximum cooling capacity achievable per unit mass of working fluid under these operating conditions, and design one or more throttling schemes to achieve the highest COP for the refrigerator.

[0006] To achieve the above objectives, the present disclosure adopts the following technical solution:

[0007] The first aspect of this disclosure provides an optimization method for a pre-cooled liquid helium temperature-range throttling refrigerator. The pre-cooled liquid helium temperature-range throttling refrigerator includes M-stage JT units for throttling and cooling the working fluid to the refrigeration temperature. Each M-stage JT unit includes M heat exchangers, M JT valves, and one evaporator. The heat exchangers and JT valves within the M-stage JT unit are numbered sequentially from 1 to M according to their temperature from highest to lowest. The high-pressure inlet and low-pressure outlet of heat exchanger number 1 serve as the inlet and outlet of the M-stage JT unit, respectively. The high-pressure outlet of heat exchanger number m... m Through the high-pressure inlet c of heat exchanger m+1, JT valve m is connected to the high-pressure inlet c of heat exchanger m+1. m Connect the low-pressure outlet end of heat exchanger m+1 to the low-pressure inlet end d of heat exchanger m. m Connections, m = 1, 2, ..., M-1, high-pressure outlet b of heat exchanger M. M The low-pressure inlet of heat exchanger M is connected sequentially through valve M and evaporator. M connect;

[0008] The optimization method for determining the number of stages M and the high voltage of each intermediate stage of the JT unit includes the following steps:

[0009] Step S1: Set the working fluid type and circulating low-pressure P for the predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L,max ;

[0010] Step S2: Set the series loop variable and initialize If the minimum isothermal enthalpy difference between high and low pressure working fluids exists within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, and this difference is equal to the maximum cooling capacity q... L,max In the case of [the situation], then take [the following]. Otherwise, proceed to step S3;

[0011] Step S3, let The high voltage of each intermediate stage is set as follows: And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. Let b be the intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure. l This corresponds to the high-pressure outlet state of the first heat exchanger (unit l) in the JT unit, based on point b. l A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and uses a circulating high-pressure P. H The enthalpy-temperature curve of the working fluid is located at point b. l-1 and point b l The high-pressure working fluid enthalpy-temperature line between them adopts a Class I high-pressure P Hl The enthalpy-temperature curve of the working fluid is located at point 1. The high-pressure working fluid enthalpy-temperature wire between the evaporator inlet and the evaporator inlet is adopted. High voltage Enthalpy-temperature curve of the working fluid; for the obtained new enthalpy-temperature curve of the high-pressure working fluid, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q. L,max In the case of [the situation], then take [the following]. And output high voltage for each intermediate stage; otherwise, proceed to step S4.

[0012] Step S4, repeat step S3.

[0013] In some embodiments, in step S3, the method used to set the high voltage of each intermediate stage is a traversal method.

[0014] In some embodiments, when using the traversal method, the high voltage P of each intermediate stage is recorded. Hl The traversal step size is ΔP. Then the traversal space is k l It is any natural number.

[0015] In some embodiments, in step S3, the method used to set the high pressure of each intermediate stage is the gradient descent method, which takes the pressure value corresponding to the maximum minimum isothermal enthalpy difference between the high and low pressure working fluids as the corresponding intermediate stage high pressure.

[0016] In some embodiments, the working medium is selected as helium-3 or helium-4.

[0017] The second aspect of this disclosure provides a pre-cooled liquid helium temperature-range throttling refrigerator, comprising an M-stage JT unit for throttling and cooling the working fluid to the refrigeration temperature. The M-stage JT unit includes M first heat exchangers, M JT valves, and an evaporator. The first heat exchangers and JT valves within the M-stage JT unit are numbered sequentially from 1 to M according to their temperature from high to low. The high-pressure inlet and low-pressure outlet of the first heat exchanger number 1 serve as the inlet and outlet of the M-stage JT unit, respectively. The high-pressure outlet of the first heat exchanger number m... m Through the high-pressure inlet c of the first heat exchanger (m+1) connected to valve m, JT valve is connected to... m Connect the low-pressure outlet end of heat exchanger m+1 to the low-pressure inlet end d of heat exchanger m. m Connections, m = 1, 2, ..., M-1, the high-pressure outlet b of the first heat exchanger (number M).M The low-pressure inlet d of the first heat exchanger (M) is connected sequentially through valve M and evaporator. M connect;

[0018] The number of stages M of the JT unit and the high voltage of each intermediate stage are determined according to the optimization method described in any embodiment of the first aspect of this disclosure.

[0019] In some embodiments, the pre-cooled liquid helium temperature-range throttling refrigerator further includes:

[0020] A compressor is used to compress a low-pressure working fluid into a high-pressure working fluid.

[0021] The precooling unit, connected to the compressor and the JT unit, is used to cool the working fluid below the transition temperature.

[0022] In some embodiments, the precooling unit adopts an N-stage precooling unit, including N second heat exchangers and N precooling heat exchangers. The N second heat exchangers and N precooling heat exchangers are numbered sequentially from 1 to N according to the temperature from high to low. The high-pressure outlet end of the i-th second heat exchanger and the high-pressure inlet end of the i+1-th second heat exchanger are connected through the i-th precooling heat exchanger. The low-pressure outlet end of the i+1-th second heat exchanger is connected to the low-pressure inlet end of the i-th second heat exchanger, i = 1, 2, ..., N-1. The high-pressure outlet end of the N-th second heat exchanger is connected to the inlet end of the M-stage JT unit through the N-th precooling heat exchanger. The outlet end of the M-stage JT unit is connected to the low-pressure inlet end of the N-th second heat exchanger.

[0023] The third aspect of this disclosure provides an optimization apparatus for a pre-cooled liquid helium temperature-range throttling refrigerator based on the optimization method described in any embodiment of the first aspect of this disclosure, comprising:

[0024] The first module is configured to set the working fluid type and circulating low-pressure P under predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L,max ;

[0025] The second module is configured to set series loop variables. and initialize If the minimum isothermal enthalpy difference between high and low pressure working fluids exists within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, and this difference is equal to the maximum cooling capacity q... L,max In the case of [the situation], then take [the following]. Otherwise, call the third module;

[0026] The third module is configured to determine whether the next level of throttling can achieve the maximum cooling capacity q by following the steps below.L,max :make The high voltage of each intermediate stage is set as follows: And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. Let b be the intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure. l This corresponds to the high-pressure outlet state of heat exchanger number 1 in unit JT, based on point b. l A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and uses a circulating high-pressure P. H The enthalpy-temperature curve of the working fluid is located at point b. l-1 and point b l The high-pressure working fluid enthalpy-temperature line between them adopts a Class I high-pressure P Hl The enthalpy-temperature curve of the working fluid is located at point 1. The high-pressure working fluid enthalpy-temperature wire between the evaporator inlet and the evaporator inlet is adopted. High voltage For the newly obtained high-pressure working fluid enthalpy-temperature curve, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q... L,max In the case of [the situation], then take [the following]. It outputs high pressure for each intermediate stage; otherwise, it continues to determine whether the next stage of throttling can achieve the maximum cooling capacity q. L,max .

[0027] A fourth aspect of this disclosure provides a computer-readable storage medium storing computer instructions for causing the computer to perform the optimized method described in any embodiment of the first aspect of this disclosure.

[0028] Compared with the prior art, this disclosure has the following characteristics and beneficial effects:

[0029] Since the maximum cooling capacity per unit mass of a pre-cooled liquid helium temperature-range throttling refrigerator depends on the smaller of the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the cooling temperature, and given that the pre-cooling temperature, cooling temperature, and cycle high and low pressures are all fixed, the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature is also fixed. The advantage of this disclosure lies in the fact that when the specific enthalpy difference between the high and low pressure working fluids at the cooling temperature is less than that at the lowest pre-cooling temperature, the specific enthalpy difference between the high and low pressure working fluids at the cooling temperature can be increased through the multi-stage throttling method proposed in this invention, thereby increasing the maximum cooling capacity per unit mass of the pre-cooled liquid helium temperature-range throttling refrigerator and clearly defining the path to obtaining the highest COP. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the throttling refrigerator targeted by the optimization method provided in the first aspect of this disclosure;

[0031] Figure 2 This is an overall flowchart of the optimization method provided in the first aspect of this disclosure;

[0032] Figure 3 This is the enthalpy-temperature diagram of the throttling path corresponding to the operating conditions of Embodiment 1 of this disclosure;

[0033] Figure 4 This is a schematic diagram of the structure of a first-stage JT unit determined according to the working conditions of Embodiment 1 of this disclosure;

[0034] Figure 5 In Figure (a) and (b), the enthalpy-temperature diagrams of the first-stage throttling path and the second-stage throttling path, respectively, correspond to the operating conditions of Embodiment 2 of this disclosure.

[0035] Figure 6 This is a schematic diagram of the structure of the secondary JT unit determined according to the working conditions of Embodiment 2 of this disclosure;

[0036] Figure 7 In Figures (a) and (b), the enthalpy-temperature diagrams for the first-stage throttling path and the third-stage throttling path, respectively, correspond to the operating conditions of Embodiment 3 of this disclosure.

[0037] Figure 8 This is a schematic diagram of the structure of a three-level JT unit determined according to the working conditions of Embodiment 3 of this disclosure;

[0038] Figure 9 This is a schematic diagram of the structure of an electronic device provided in the third aspect of this disclosure. Specific implementation methods

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0040] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0041] An optimization method for a pre-cooled liquid helium temperature-range throttling refrigerator is provided in the first aspect of this disclosure. See also... Figure 1 The throttling chillers to be optimized include:

[0042] The M-class JT unit is used to throttle and cool the working fluid to the refrigeration temperature. The M-class JT unit includes M first heat exchangers, M JT valves, and one evaporator. The first heat exchangers and JT valves within the M-class JT unit are numbered sequentially from 1 to M according to their temperature from highest to lowest. The high-pressure inlet and low-pressure outlet of the first heat exchanger number 1 serve as the inlet a and outlet e of the M-class JT unit, respectively. Inlet a and outlet e of the M-class JT unit are connected to the high-pressure outlet and low-pressure inlet of the pre-cooling unit, respectively. The high-pressure outlet b of the first heat exchanger number m... m Through the high-pressure inlet c of the first heat exchanger (m+1) connected to valve m, JT valve is connected to... m Connect the low-pressure outlet end of heat exchanger m+1 to the low-pressure inlet end d of heat exchanger m. m Connections, m = 1, 2, ..., M-1, the high-pressure outlet b of the first heat exchanger (number M). M The low-pressure inlet d of the first heat exchanger (M) is connected sequentially through valve M and evaporator. M connect;

[0043] See Figure 2 The optimization method provided in this embodiment is used to determine the number of stages M of the JT unit and the high pressure of each intermediate stage, so that the throttling refrigerator can obtain the maximum cooling capacity and achieve optimal COP under predetermined operating conditions. The optimization method of this embodiment includes the following steps:

[0044] Step S1: Set the working fluid type and circulating low-pressure P for the predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L,max ;

[0045] Step S2: Set the series loop variable and initialize If the minimum isothermal enthalpy difference between the high and low pressure working fluids is equal to the maximum cooling capacity q within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature... L,max This indicates that the first-stage throttling from high pressure to low pressure enables the throttling chiller to obtain the maximum cooling capacity under predetermined operating conditions. Therefore, take... If the minimum isothermal enthalpy difference between the high and low pressure working fluids is less than the maximum cooling capacity q within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature... L,max If the first-stage throttling from high pressure to low pressure cannot enable the throttling chiller to obtain the maximum cooling capacity under the predetermined operating conditions, it is necessary to consider whether the next stage of throttling can obtain the maximum cooling capacity, i.e., to execute step S3.

[0046] Step S3, let Setting intermediate high voltage And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. The intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure is denoted as point b. l This corresponds to the high-pressure outlet state of the first heat exchanger (unit 1) in the JT unit, including the temperature at the high-pressure outlet of the first heat exchanger (unit 1). enthalpy value and pressure Based on points A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and adopts a circulating high-pressure (i.e., first-stage high-pressure) P. H The enthalpy-temperature line of the working fluid is located at b. l-1 Point and b l The high-pressure working fluid enthalpy-temperature line between points adopts a level I high-pressure P Hl The enthalpy-temperature line of the working fluid is located at The high-pressure working fluid enthalpy-temperature line between the point and the evaporator inlet is adopted. High voltage Enthalpy-temperature curve of the working fluid; for the obtained new enthalpy-temperature curve of the high-pressure working fluid, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q. L,max In the case of [the situation], then take [the following]. And output each intermediate stage high voltage P Hl If the minimum isothermal enthalpy difference between the high-pressure and low-pressure working fluids is less than the maximum cooling capacity q L,max Then proceed to step S4;

[0047] Step S4, repeat step S3.

[0048] In some embodiments, the working fluid in the throttling refrigerator is helium-3 or helium-4. It should be noted that the optimization method in this embodiment is mainly aimed at helium working fluid. This is because, due to the physical properties of helium working fluid, the minimum isothermal enthalpy difference between the high and low pressure working fluids in the first-stage throttling may not be obtained at the pre-cooling temperature within the range from the refrigeration temperature to the minimum pre-cooling temperature. Therefore, it is necessary to explore whether multi-stage throttling can obtain the maximum cooling capacity.

[0049] In some embodiments, the method used in step S3 to set each intermediate high voltage is a traversal method, wherein each intermediate high voltage P is denoted as... Hl The traversal step size is ΔP. Then the traversal space is k l Let P be any natural number, and if during the traversal, there exists a P... Hl The value makes the minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q. L,max In the case of [the situation], then take [the following]. And output P Hl Value (or range of values). Otherwise, specify all possible P values. Hl None of the chosen values ​​can achieve the minimum isothermal enthalpy difference between the high and low pressure working fluids to reach the maximum cooling capacity q. L,max At this point, S4 needs to be executed to try. Level throttling.

[0050] In other embodiments, the method used in step S3 to set the high pressure of each intermediate stage is a gradient descent method, whereby the pressure value corresponding to the maximum minimum isothermal enthalpy difference between the high and low pressure working fluids is taken as the intermediate stage high pressure P. Hl The value, If the maximum value of the minimum isothermal enthalpy difference between the high and low pressure working fluids is less than the maximum cooling capacity q within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature... L,max Then proceed to step S4. If the maximum value of the minimum isothermal enthalpy difference between high and low pressure working fluids within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature is equal to the maximum cooling capacity q, then... L,max In the case of [the situation], then take [the following]. And output each intermediate stage high voltage P Hl .

[0051] The following are specific embodiments of the optimization method proposed in the first aspect of this disclosure.

[0052] Example 1

[0053] like Figure 3 ( Figure 3 Points a, b, c, d, and e in the diagram correspond to... Figure 4 The states of midpoints a, b, c, d, and e are shown. Point O is the intersection of the high-pressure and low-pressure lines at the liquid helium temperature. Point e* corresponds to the enthalpy point of the low-pressure working fluid at the lowest pre-cooling temperature. The working fluid used is helium-4, the cooling temperature is 4.2K, the lowest pre-cooling temperature is 15.0K, the circulating high pressure is 1000kPa, and the circulating low pressure is 100kPa. The specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature is also shown. It is 7.29 kJ / kg, h a and The specific enthalpy of the working fluid at points a and e*, respectively, and the specific latent heat of vaporization Δh of the working fluid at the refrigeration temperature. lg The maximum cooling capacity per unit mass of working fluid under this operating condition is 7.29 kJ / kg, which is 20.98 kJ / kg. The minimum isothermal enthalpy difference between the high and low pressure working fluids within the temperature range of 4.2 K to 15.0 K is... The value equals the maximum cooling capacity, indicating that the maximum cooling capacity under this predetermined operating condition can be achieved by a single-stage throttling from 1000 kPa to 100 kPa. Therefore, the JT unit in the throttling chiller adopts the following... Figure 4 The first-level JT unit is shown.

[0054] Example 2

[0055] like Figure 5 Points a, b, c, d, and e in (a) are respectively connected to... Figure 4 The states of the corresponding points in (a) and (b) are respectively related to the states of the points with the same name. Figure 6 The states of the corresponding points in the diagram are as follows: point O is the intersection of the high-pressure and low-pressure lines at the liquid helium temperature, and point e* corresponds to the enthalpy point of the low-pressure working fluid at the minimum pre-cooling temperature. The operating conditions shown are as follows: the working fluid is helium-4, the cooling temperature is 4.2K, the minimum pre-cooling temperature is 16.5K, the circulating high pressure is 2400kPa, and the circulating low pressure is 100kPa. The specific enthalpy difference between the high and low pressure working fluids at the minimum pre-cooling temperature is also shown. The specific latent heat of vaporization Δh of the working fluid at the refrigeration temperature is 12.07 kJ / kg. lg If the energy density is 20.98 kJ / kg, then the maximum cooling capacity obtainable per unit mass of working fluid under this operating condition is 12.07 kJ / kg. For example... Figure 5 As shown in (a), the following method is adopted. Figure 4 When the first-stage JT unit shown is performing first-stage throttling, the minimum isothermal enthalpy difference between the high and low pressure working fluids in the temperature range from 4.2K to 16.5K is h. d -h O Less than the maximum cooling capacity, h d and h O Let d and O be the specific enthalpy of the working fluid, respectively; therefore, two-stage throttling needs to be considered. The range of values ​​for the second-stage high-pressure system is obtained through traversal calculations, and the second-stage high-pressure system P is set. H2 Given a pressure of 1940 kPa, one feasible throttling path is proposed, namely, the new high-pressure working fluid enthalpy-temperature curve, such as... Figure 5 As shown in (b), the new high-pressure working fluid enthalpy-temperature line consists of two segments. The high-pressure working fluid enthalpy-temperature line located between point b1 and the inlet end of the JT unit adopts a circulating high pressure (i.e., a single-stage high pressure) P. H The working fluid enthalpy-temperature line, located at point b1 between the evaporator inlet and the high-pressure working fluid enthalpy-temperature line, adopts a two-stage high-pressure P-type design. H2 The working fluid enthalpy-temperature curve indicates that the maximum cooling capacity under the predetermined operating condition can be achieved through a two-stage throttling process, from isothermal throttling at 2400 kPa to 1940 kPa and then to 100 kPa. Therefore, the JT unit in the throttling chiller adopts the following... Figure 6 The second-level JT unit is shown.

[0056] Example 3

[0057] like Figure 7 Points a, b1, b2, b3, c1, c2, c3, d3, and e in (b) are respectively connected to... Figure 8The states of the corresponding points in the diagram are as follows: point O is the intersection of the high-pressure and low-pressure lines at the liquid helium temperature, and point e* corresponds to the enthalpy point of the low-pressure working fluid at the minimum pre-cooling temperature. The operating conditions shown are as follows: the working fluid is helium-3, the cooling temperature is 3.0 K, the minimum pre-cooling temperature is 15.0 K, the high pressure is 1600 kPa, and the low pressure is 81.83 kPa. The specific enthalpy difference between the high and low pressure working fluids at the minimum pre-cooling temperature is also shown. The specific latent heat of vaporization Δh of the working fluid at the refrigeration temperature is 10.31 kJ / kg. lg If the value is 10.41 kJ / kg, then the maximum cooling capacity obtainable per unit mass of working fluid under this operating condition is 10.31 kJ / kg. For example... Figure 7 As shown in (a), under this operating condition, there is no cooling capacity at liquid helium temperature in the first-stage throttling, therefore a two-stage throttling is considered. Through exhaustive calculations, any pressure value between 81.83 kPa and 1600 kPa, as the second-stage high pressure, cannot make the minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity within the temperature range from 3.0 K to 15.0 K; therefore, a third-stage throttling is considered. The ranges for the second-stage and third-stage high pressures are obtained through exhaustive calculations, and the second-stage high pressure P is set. H2 700kPa, Level III high pressure P H3 Given a pressure of 200 kPa, provide one feasible throttling path as follows: Figure 7 As shown in (b), the new high-pressure working fluid enthalpy-temperature line consists of three segments. The high-pressure working fluid enthalpy-temperature line located between point b1 and the inlet end of the JT unit adopts a circulating high-pressure (i.e., first-stage high-pressure) P. H The working fluid enthalpy-temperature curve, located between points b1 and b2, employs a two-stage high-pressure P-type enthalpy-temperature curve. H2 The working fluid enthalpy-temperature line, located between point b2 and the evaporator inlet, employs a three-stage high-pressure P-type enthalpy-temperature line. H3 The working fluid enthalpy-temperature curve indicates that the maximum cooling capacity under the predetermined operating condition can be achieved through a three-stage throttling process: isothermal throttling from 1600 kPa to 700 kPa, then isothermal throttling to 200 kPa, and finally throttling to 81.83 kPa. Therefore, the JT unit in the throttling chiller adopts the following... Figure 8 The three-level JT unit is shown.

[0058] It is understood that the optimization method for the pre-cooled liquid helium temperature zone throttling refrigerator provided in the first aspect of this disclosure clarifies the advantages of multi-stage throttling over single-stage throttling, and helps to select a more efficient throttling method (including the number of throttling stages and intermediate pressure) according to different operating conditions.

[0059] The second aspect of this disclosure provides a pre-cooled liquid helium temperature-zone throttling refrigerator, wherein the number of stages M and the number of intermediate high pressures of the JT unit in the throttling refrigerator are determined according to the optimization method provided in any embodiment of the first aspect of this disclosure.

[0060] Furthermore, the pre-cooled liquid helium temperature-range throttling refrigerator of this embodiment also includes:

[0061] A compressor is used to compress a low-pressure working fluid into a high-pressure working fluid.

[0062] The precooling unit, connected to the compressor and JT unit, is used to cool the working fluid below the transition temperature.

[0063] Further, see Figure 1 The precooling unit adopts an N-stage precooling unit, including N second heat exchangers and N precooling heat exchangers. The N second heat exchangers and N precooling heat exchangers are numbered sequentially from 1 to N according to the temperature from high to low. The high-pressure outlet end of the i-th second heat exchanger and the high-pressure inlet end of the i+1-th second heat exchanger are connected through the i-th precooling heat exchanger. The low-pressure outlet end of the i+1-th second heat exchanger is connected to the low-pressure inlet end of the i-th second heat exchanger. i = 1, 2, ..., N-1. The high-pressure outlet end of the N-th second heat exchanger is connected to the inlet end of the M-stage JT unit through the N-th precooling heat exchanger. The outlet end of the M-stage JT unit is connected to the low-pressure inlet end of the N-th second heat exchanger.

[0064] An optimized apparatus for a pre-cooled liquid helium temperature-range throttling refrigerator provided in a third aspect embodiment of this disclosure includes:

[0065] The first module is configured to set the working fluid type and circulating low-pressure P under predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L,max ;

[0066] The second module is configured to set series loop variables. and initialize If the minimum isothermal enthalpy difference between high and low pressure working fluids exists within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, and this difference is equal to the maximum cooling capacity q... L,max In the case of [the situation], then take [the following]. Otherwise, call the third module;

[0067] The third module is configured to determine whether the next level of throttling can achieve the maximum cooling capacity q by following the steps below. L,max :make The high voltage of each intermediate stage is set as follows: And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. Let b be the intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure. lThis corresponds to the high-pressure outlet state of heat exchanger number 1 in unit JT, based on point b. l A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and uses a circulating high-pressure P. H The enthalpy-temperature curve of the working fluid is located at point b. l-1 and point b l The high-pressure working fluid enthalpy-temperature line between them adopts a Class I high-pressure P Hl The enthalpy-temperature curve of the working fluid is located at point 1. The high-pressure working fluid enthalpy-temperature wire between the evaporator inlet and the evaporator inlet is adopted. High voltage For the newly obtained high-pressure working fluid enthalpy-temperature curve, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q... L,max In the case of [the situation], then take [the following]. It outputs high pressure for each intermediate stage; otherwise, it continues to determine whether the next stage of throttling can achieve the maximum cooling capacity q. L,max .

[0068] It should be noted that the foregoing explanation of the embodiments of the optimization method also applies to the optimization device of this embodiment, and will not be repeated here.

[0069] To implement the above embodiments, this disclosure also proposes a computer-readable storage medium storing a computer program thereon, which is executed by a processor to perform the optimization method provided in the first aspect of this disclosure.

[0070] The following is for reference. Figure 9 The diagram illustrates a structural schematic suitable for implementing the electronic device provided in the third aspect of the present disclosure. The electronic device in the embodiments of the present disclosure may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (e.g., in-vehicle navigation terminals), as well as fixed terminals such as digital TVs, desktop computers, and servers. Figure 9 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of the embodiments disclosed herein.

[0071] like Figure 9As shown, the electronic device may include a processing unit (e.g., a central processing unit, a graphics processing unit, etc.) 101, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 102 or a program loaded from a storage device 108 into a random access memory (RAM) 103. The RAM 103 also stores various programs and data required for the operation of the electronic device. The processing unit 101, ROM 102, and RAM 103 are interconnected via a bus 104. An input / output (I / O) interface 105 is also connected to the bus 104.

[0072] Typically, the following devices can be connected to I / O interface 105: input devices 106 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, etc.; output devices 107 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 108 including, for example, magnetic tapes, hard disks, etc.; and communication devices 109. Communication device 109 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 9 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown. More or fewer devices may be implemented or have alternatively.

[0073] In particular, according to embodiments of this disclosure, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, this embodiment includes a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such an embodiment, the computer program can be downloaded and installed from a network via communication device 109, or installed from storage device 108, or installed from ROM 102. When the computer program is executed by processing device 101, it performs the functions defined above in the methods of embodiments of this disclosure.

[0074] It should be noted that the computer-readable medium described in this disclosure can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this disclosure, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in connection with an instruction execution system, apparatus, or device. In this disclosure, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wires, optical fibers, RF (radio frequency), etc., or any suitable combination thereof.

[0075] The aforementioned computer-readable medium may be included in the aforementioned electronic device; or it may exist independently and not assembled into the electronic device.

[0076] The aforementioned computer-readable medium carries one or more programs, which, when executed by the electronic device, cause the electronic device to perform the optimized method provided in any embodiment of the first aspect of this disclosure.

[0077] Computer program code for performing the operations of this disclosure can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and Python, as well as conventional procedural programming languages ​​such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0078] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0079] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0080] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0081] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0082] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0083] Those skilled in the art will understand that implementing all or part of the steps of the methods in the above embodiments can be accomplished by instructing related hardware through a program. The developed program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0084] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0085] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. An optimization method for a pre-cooled liquid helium temperature-range throttling refrigerator, characterized in that, The pre-cooled liquid helium temperature-range throttling refrigerator includes M-stage JT units for throttling and cooling the working fluid to the refrigeration temperature. Each M-stage JT unit includes M heat exchangers, M JT valves, and one evaporator. The heat exchangers and JT valves within the M-stage JT unit are numbered sequentially from 1 to M according to their temperature from highest to lowest. The high-pressure inlet and low-pressure outlet of heat exchanger number 1 serve as the inlet and outlet of the M-stage JT unit, respectively. The high-pressure outlet of heat exchanger number m... m Through the high-pressure inlet c of heat exchanger m+1, JT valve m is connected to the high-pressure inlet c of heat exchanger m+1. m Connect the low-pressure outlet end of heat exchanger m+1 to the low-pressure inlet end d of heat exchanger m. m Connections, m = 1, 2, ..., M-1, high-pressure outlet b of heat exchanger M. M The low-pressure inlet of heat exchanger M is connected sequentially through valve M and evaporator. M connect; The optimization method for determining the number of stages M and the high voltage of each intermediate stage of the JT unit includes the following steps: Step S1: Set the working fluid type and circulating low-pressure P for the predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L，max ; Step S2: Set the series loop variable and initialize If the minimum isothermal enthalpy difference between high and low pressure working fluids exists within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, and this difference is equal to the maximum cooling capacity q... L，max In the case of [the situation], then take [the following]. Otherwise, proceed to step S3; Step S3, let The high voltage of each intermediate stage is set as follows: And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. Let b be the intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure. l This corresponds to the high-pressure outlet state of the first heat exchanger (unit l) in the JT unit, based on point b. l A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and uses a circulating high-pressure P. H The enthalpy-temperature curve of the working fluid is located at point b. l-1 and point b l The high-pressure working fluid enthalpy-temperature line between them adopts a Class I high-pressure P Hl The enthalpy-temperature curve of the working fluid is located at point 1. The high-pressure working fluid enthalpy-temperature wire between the evaporator inlet and the evaporator inlet is adopted. High voltage Enthalpy-temperature curve of the working fluid; for the obtained new enthalpy-temperature curve of the high-pressure working fluid, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q. L，max In the case of [the situation], then take [the following]. And output high voltage for each intermediate stage; otherwise, proceed to step S4. Step S4, repeat step S3.

2. The optimization method according to claim 1, characterized in that, In step S3, the method used to set the high voltage of each intermediate stage is the traversal method.

3. The optimization method according to claim 2, characterized in that, When using the aforementioned traversal method, record the high voltage P of each intermediate stage. Hl The traversal step size is ΔP. Then the traversal space is k l It is any natural number.

4. The optimization method according to claim 1, characterized in that, In step S3, the method used to set the high pressure of each intermediate stage is the gradient descent method, which takes the pressure value corresponding to the maximum minimum isothermal enthalpy difference between the high and low pressure working fluids as the corresponding intermediate stage high pressure.

5. The optimization method according to any one of claims 1 to 4, characterized in that, The working medium is either helium-3 or helium-4.

6. A pre-cooled liquid helium temperature-range throttling refrigerator, characterized in that, The system includes an M-stage JT unit used to throttle and cool the working fluid to the refrigeration temperature. The M-stage JT unit comprises M first heat exchangers, M JT valves, and one evaporator. The first heat exchangers and JT valves within the M-stage JT unit are numbered sequentially from 1 to M according to their temperature, from highest to lowest. The high-pressure inlet and low-pressure outlet of the first heat exchanger number 1 serve as the inlet and outlet of the M-stage JT unit, respectively. The high-pressure outlet of the first heat exchanger number m... m Through the high-pressure inlet c of the first heat exchanger (m+1) connected to valve m, JT valve is connected to... m Connect the low-pressure outlet end of heat exchanger m+1 to the low-pressure inlet end d of heat exchanger m. m Connections, m = 1, 2, ..., M-1, high-pressure outlet b of heat exchanger M (first heat exchanger). M The low-pressure inlet d of the first heat exchanger (M) is connected sequentially through valve M and evaporator. M connect; The number of stages M of the JT unit and the high voltage of each intermediate stage are determined by the optimization method according to any one of claims 1 to 5.

7. The pre-cooled liquid helium temperature-range throttling refrigerator according to claim 6, characterized in that, The pre-cooled liquid helium temperature-range throttling refrigerator also includes: A compressor is used to compress a low-pressure working fluid into a high-pressure working fluid. The precooling unit, connected to the compressor and the JT unit, is used to cool the working fluid below the transition temperature.

8. The pre-cooled liquid helium temperature-range throttling refrigerator according to claim 7, characterized in that, The precooling unit adopts an N-stage precooling unit, including N second heat exchangers and N precooling heat exchangers. The N second heat exchangers and N precooling heat exchangers are numbered sequentially from 1 to N according to the temperature from high to low. The high-pressure outlet end of the i-th second heat exchanger and the high-pressure inlet end of the i+1-th second heat exchanger are connected through the i-th precooling heat exchanger. The low-pressure outlet end of the i+1-th second heat exchanger is connected to the low-pressure inlet end of the i-th second heat exchanger. i = 1, 2, ..., N-1. The high-pressure outlet end of the N-th second heat exchanger is connected to the inlet end of the M-stage JT unit through the N-th precooling heat exchanger. The outlet end of the M-stage JT unit is connected to the low-pressure inlet end of the N-th second heat exchanger.

9. An optimization device for a pre-cooled liquid helium temperature-range throttling refrigerator based on the optimization method described in any one of claims 1 to 5, characterized in that, include: The first module is configured to set the working fluid type and circulating low-pressure P under predetermined operating conditions. L Circulating high pressure P H Calculate the specific enthalpy difference between the high and low pressure working fluids at the lowest pre-cooling temperature and the specific latent heat of vaporization of the working fluid at the refrigeration temperature, taking the smaller of the two as the maximum cooling capacity q that can be obtained per unit mass of working fluid under the predetermined operating conditions. L，max ; The second module is configured to set series loop variables. and initialize If the minimum isothermal enthalpy difference between high and low pressure working fluids exists within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, and this difference is equal to the maximum cooling capacity q... L，max In the case of [the situation], then take [the following]. Otherwise, call the third module; The third module is configured to determine whether the next level of throttling can achieve the maximum cooling capacity q by following the steps below. L，max :make The high voltage of each intermediate stage is set as follows: And satisfy Plot the enthalpy-temperature curves of the high-pressure working fluid in each intermediate stage. Let b be the intersection of the enthalpy-temperature lines of the working fluid at level l and level l+1 high pressure. l This corresponds to the high-pressure outlet state of heat exchanger number 1 in unit JT, based on point b. l A new high-pressure working fluid enthalpy-temperature curve was obtained, which was derived from... The high-pressure working fluid enthalpy-temperature line, located between point b1 and the inlet end of unit JT, is composed of a segment and uses a circulating high-pressure P. H The enthalpy-temperature curve of the working fluid is located at point b. l-1 and point b l The high-pressure working fluid enthalpy-temperature line between them adopts a Class I high-pressure P Hl The enthalpy-temperature curve of the working fluid is located at point 1. The high-pressure working fluid enthalpy-temperature wire between the evaporator inlet and the evaporator inlet is adopted. High voltage For the newly obtained high-pressure working fluid enthalpy-temperature curve, within the temperature range from the refrigeration temperature to the minimum pre-cooling temperature, if there exists a minimum isothermal enthalpy difference between the high and low pressure working fluids equal to the maximum cooling capacity q... L，max In the case of [the situation], then take [the following]. It outputs high pressure for each intermediate stage; otherwise, it continues to determine whether the next stage of throttling can achieve the maximum cooling capacity q. L，max .

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the optimized method according to any one of claims 1 to 5.

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