Fluid cooling system with variable-working condition adjustment function

Abstract

The present disclosure relates to a cooling system with a variable operating condition regulation function for a fluid. The cooling system includes an expander, a compressor driven by a motor with a rotating speed adjustable, a controller and a sensing apparatus. The sensing apparatus is configured to detect the temperature of a fluid and / or a refrigeration working medium, the controller can receive data of the sensing apparatus and can control the rotating speed of the motor based on the data of the sensing apparatus, and it can be ensured that the temperature of the cooled fluid is kept at a predetermined value by regulating the rotating speed of the motor when a required cold quantity of the cooled fluid and / or a cold quantity provided by the refrigeration working medium are / is changed. Particularly, the control is carried out in a PID regulation mode, and the system has the advantages of simple control, safety, reliability and rapid regulation, such that the cooling system of the present disclosure can correspondingly regulate the cold quantity along with the change of operating conditions, and the variable operating condition regulation with the cold quantity ranging from 0 to 100% is realized.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of liquefied natural gas (LNG) storage and transportation, in particular to a processing system for boil-off gas in an LNG ship, and particularly relates to a cooling system with a variable operating condition regulation function for a fluid.BACKGROUND

[0002] With the rapid development of economic society and modern industry, energy utilization and environmental pollution become the focus of world attention. In the face of increasingly severe environmental requirements, the transformation of international energy strategies is accelerated, and the development and application of clean fuels become important development directions of energy strategies. Natural gas has the characteristics of small pollutant emission and relatively low cost, such that the proportion of the natural gas in international energy supply is increased year by year, and the situation that the global natural gas consumption demand is rapidly increased is expected to continue until 2040. Compared with pipeline transportation of the natural gas, marine LNG transportation has the advantages of flexibility, and diversified production places and destinations because long transportation pipelines do not need to be laid and the natural gas can be flexibly transported around the world. With the continuous and dramatic increase of natural gas trade volume, the global LNG shipping industry will be rapidly developed, and 600 large LNG ship orders are expected to be newly added in the world by 2030.

[0003] In view of the special physical and chemical properties of LNG, the LNG may receive externally conducted heat, resulting in boil-off gas during transportation of any LNG ships even if the thermal insulation property of a cargo tank is excellent. The production of the boil-off gas can make pressure of the cargo tank rise and destroy the structure of the cargo tank. If the boil-off gas is directly discharged into the atmosphere, direct economic loss and greenhouse harm are also caused. Therefore, a cooling system for the boil-off gas needs to be provided, and the cooling system can recondensate and reliquefy the boil-off gas in the cargo tank, reduce evaporation possibility of the boil-off gas in the cargo tank, reduce transportation cost, and improve safety of LNG transportation, and is an important high value-added device on large LNG transport ships and refueling ships at present. Such problems also exist in LNG storage facilities on land.

[0004] However, in an existing LNG boil-off gas cooling system, from the process technology, when a mixed working medium reliquefaction mode is adopted, it leads to complicated flow and high maintenance difficulty, and working media such as propane are explosive gases, which have high leakage risk and high danger. When a nitrogen expansion reliquefaction mode is adopted, inert gas is used as a refrigeration working medium, the safety is high, but the system needs more auxiliary devices such as a boil-off gas compressor, a nitrogen generator, a boil-off gas heater and the like, the installation and debugging period is long, and the maintenance cost is high. Meanwhile, since the pressure and temperature in LNG storage apparatuses are affected by many factors, such as external temperature change, change in the amount of incoming and outgoing LNG, and change in the corresponding temperature, and the like, the pressure and temperature in the LNG storage apparatuses constantly fluctuate. Therefore, it is urgently required to develop an LNG cooling system having a control mode with high safety, high reliability, and high adaptability.SUMMARY

[0005] To solve the above technical problems, the present disclosure provides a cooling system with a variable operating condition regulation function for a fluid. The fluid may preferably be liquefied natural gas. The cooling system includes a cooling loop configured to cool the fluid. The cooling loop includes: a compressor, configured to compress a refrigeration working medium of the cooling system, so as to increase pressure of the refrigeration working medium; a cooler, configured to cool the compressed refrigeration working medium; an expander, configured to expand the cooled refrigeration working medium; a motor, capable of driving the compressor to compress the refrigeration working medium, where a rotating speed of the motor is adjustable, especially continuously variable; and a heat exchanger, configured to generate heat exchange between a cooled fluid and the expanded refrigeration working medium, where the refrigeration working medium operates in a closed cycle in the cooling loop, after the refrigeration working medium is compressed in the compressor, the refrigeration working medium is cooled by the cooler to reduce the temperature, then is expanded by the expander to reduce the pressure and the temperature, and then absorbs heat from the cooled fluid in the heat exchanger to reduce the temperature of the cooled fluid, and the refrigeration working medium after absorbing the heat enters the compressor to be compressed; and the cooling system further includes a controller and a sensing apparatus, the sensing apparatus is configured to detect a temperature of the fluid and / or the refrigeration working medium, the sensing apparatus and the motor are connected to the controller, and the controller can receive data of the sensing apparatus and control the rotating speed of the motor based on the data of the sensing apparatus.

[0006] Further, the sensing apparatus may be provided on at least one of an inlet pipe section of the expander, a pipe section between an outlet of the expander and the heat exchanger, an outlet pipe section of the cooled fluid of the heat exchanger, or an outlet pipe section of the refrigeration working medium of the heat exchanger.

[0007] Further, a corresponding predetermined value is provided in the controller for a temperature-related value of the refrigeration working medium or a temperature-related value of the cooled fluid at a location where the sensing apparatus is mounted, and when an actual value detected by the sensing apparatus is different from the predetermined value, the controller regulates the rotating speed of the motor using a PID control manner so as to regulate a circulation speed of the refrigeration working medium in the cooling loop and thus regulate a refrigeration amount provided by the cooling loop until the actual value is the same as the predetermined value; and especially, when the actual value is greater than the predetermined value, the controller increases the rotating speed of the motor, and when the actual value is less than the predetermined value, the controller decreases the rotating speed of the motor.

[0008] Further, the temperature-related value can be a temperature value detected by a single sensing apparatus, a speed of change of the temperature value detected by the single sensing apparatus, a difference value of the temperature values detected by a plurality of sensing apparatuses, or a speed of change of the difference value of the temperature values detected by the plurality of sensing apparatus.

[0009] Further, a flowing direction of fluid in at least part of a section of the heat exchanger is opposite to a flowing direction of the expanded refrigeration working medium, where the refrigeration working medium adopts inert gas, the refrigeration working medium is preferably selected from He, N 2 , H 2 , Ne, or a mixed gas of at least two of He, N 2 , H 2 , or Ne, and the fluid is liquefied natural gas, carbon dioxide, hydrogen, helium, or a mixed gas of at least two of the liquefied natural gas, the carbon dioxide, the hydrogen, or the helium.

[0010] Further, the cooling loop further includes a regenerative heat exchanger, and the refrigeration working medium flowing out of the heat exchanger exchanges heat with the refrigeration working medium prior to entering the expander in the regenerative heat exchanger; and the heat exchanger and the regenerative heat exchanger are mounted in a thermal insulation apparatus.

[0011] Further, at least two compressors are provided, and the at least two compressors are arranged in the cooling loop in series and / or in parallel, such that the refrigeration working medium flows through the at least two compressors in series and / or in parallel, where an outlet of each compressor is provided with a cooler; the refrigeration working medium expands in the expander to enable the expander to output energy, and at least one of the at least two compressors can receive the energy output by the expander; and at least one of the at least two compressors can be driven by the motor.

[0012] Further, at least one of the at least two compressors can be arranged in a co-axial drive with the motor and the expander, such that the at least one compressor is driven by energy output by the motor and the expander together.

[0013] Further, at least two expanders are provided, and the at least two expanders are arranged in the cooling loop in series and / or in parallel, such that the refrigeration working medium flows through the at least two expanders in series and / or in parallel.

[0014] Further, the compressor is an axial compressor or a centrifugal compressor, and the expander is an axial expander or a centrifugal expander.

[0015] Furthermore, the expander is provided with a bypass branch, one end of the bypass branch is connected to an inlet of the expander, the other end of the bypass branch is connected to an outlet of the expander, and preferably, a regulating valve is provided on the bypass branch and configured to regulate the refrigeration working medium flowing from the inlet of the expander to the outlet of the expander via the bypass branch; and especially, one end of the bypass branch is connected to a pipe section of the inlet of the expander located at an upstream part of the heat exchanger, and the other end of the bypass branch is connected to a pipe section of the outlet of the expander located at a downstream part of the heat exchanger.

[0016] After implementation, the present disclosure has the following beneficial effects: through the cooling system with the variable operating condition regulation function for the fluid, the cooling system includes the compressor driven by the motor with the rotating speed adjustable, the controller and the sensing apparatus, the sensing apparatus is configured to detect the temperature of the fluid and / or the refrigeration working medium, the controller can receive the data of the sensing apparatus and can control the rotating speed of the motor based on the data of the sensing apparatus, and it can be ensured that the temperature of the cooled fluid is kept at the predetermined value by regulating the rotating speed of the motor when the required cold quantity of the cooled fluid and / or the cold quantity provided by the refrigeration working medium are / is changed. Particularly, the control is carried out in a PID regulation mode, and the system has the advantages of simple control, safety, reliability and rapid regulation, such that the cooling system of the present disclosure can correspondingly regulate the cold quantity along with the change of operating conditions, and the variable operating condition regulation with the cold quantity ranging from 0 to 100% is realized.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the present disclosure, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below. It is obvious that the drawings in the description below are merely some embodiments of the present disclosure, and those of ordinary skills in the art can obtain other drawings according to these drawings without creative efforts. FIG. 1 is a control flowchart according to the present disclosure. FIG. 2 is a system diagram of Embodiment 1 according to the present disclosure. FIG. 3 is a system diagram of Embodiment 2 according to the present disclosure. FIG. 4 is a system diagram of Embodiment 3 according to the present disclosure. FIG. 5 is a system diagram of Embodiment 4 according to the present disclosure.

[0018] Reference numerals: 1. compression and expansion integrated machine; 2. compression apparatus; 3. cooler; 4. thermal insulation apparatus; 5. regenerative heat exchanger; 6. heat exchanger; 7. first motor; 8. second motor; 9. controller; 10. regulating valve of bypass branch; 11. sensing apparatus; C1, first-stage compressor; C2, second-stage compressor; C3, third-stage compressor; E1, expander; L1, fluid inlet pipe section; and L2, fluid outlet pipe section.DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure but not all of them. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skills in the art without creative effort shall fall within the protection scope of the present disclosure.

[0020] To solve the above technical problems, the present disclosure provides a cooling system with a variable operating condition regulation function for a fluid. The fluid may preferably be liquefied natural gas. The fluid is liquefied natural gas, carbon dioxide, hydrogen, helium, or a mixed gas of at least two of liquefied natural gas, carbon dioxide, hydrogen, or helium.

[0021] The cooling system includes a cooling loop, the cooling loop is configured to cool the fluid, a refrigeration working medium is provided in the cooling loop in a closed mode, the refrigeration working medium adopts inert gas, and the refrigeration working medium is preferably He, N 2 , H 2 , Ne, or a mixed gas of at least two of He, N 2 , H 2 , or Ne.Embodiment 1:

[0022] As shown in FIG. 2, a cooling loop of a cooling system includes: a compressor, configured to compress a refrigeration working medium of the cooling system, where in the present embodiment, the compressor adopts a three-stage series compression manner, that is, the compressor includes a first-stage compressor C1, a second-stage compressor C2, and a third-stage compressor C3, and for the refrigeration working medium, the first-stage compressor C1, the second-stage compressor C2, and the third-stage compressor C3 are arranged in series, that is, the refrigeration working medium sequentially passes through the first-stage compressor C1, the second-stage compressor C2, and the third-stage compressor C3 step by step, such that the refrigeration working medium is gradually pressurized by each stage of compressor, thereby gradually increasing the pressure of the refrigeration working medium; a cooler 3, configured to cool the refrigeration working medium compressed by the compressor, where in the present embodiment, three independent cooler modules are included inside the cooler 3, and the independent cooler modules are connected to outlets of the first-stage compressor C1, the second-stage compressor C2, and the third-stage compressor C3 respectively, so as to cool the refrigeration working medium at the outlet of each stage of compressor respectively; for the refrigeration working medium, the refrigeration working medium is compressed in the compressor, the volume is reduced, the pressure of the refrigeration working medium is increased, and meanwhile, the temperature of the refrigeration working medium is also increased; therefore, the temperature of the refrigeration working medium can be reduced by providing the cooler module at the outlet of each stage of compressor; here, a cold source in the cooler may be cooling water at normal temperature or air at normal temperature; therefore, the refrigeration working medium at normal temperature and normal pressure (not normal temperature and normal pressure relative to ambient temperature, but relative state of a refrigeration working medium circulating in the cooling loop, and high temperature, low temperature, medium pressure, high pressure, and low pressure described below are also the same) is compressed by the first-stage compressor C1 to become a refrigeration working medium at high temperature and medium pressure, then is cooled by the cooler 3 to become a refrigeration working medium at normal temperature and medium pressure, then is compressed by the second-stage compressor C2 to become a refrigeration working medium at high temperature and sub-high pressure, then is cooled by the cooler 3 to become a refrigeration working medium at normal temperature and sub-high pressure, then compressed by the third-stage compressor C3 to become a refrigeration working medium at high temperature and high pressure, and then is cooled by the cooler 3 to become a refrigeration working medium at normal temperature and high pressure; and an expander E1, configured to expand the cooled refrigeration working medium, where an inlet of the expander E1 is fluidly connected to the cooler 3 and configured to expand the refrigeration working medium at normal temperature and normal pressure that is compressed by the three stages of compressors and cooled by the cooler; and in the expander E1, the volume of the refrigeration working medium at normal temperature and normal pressure increases, such that the pressure and the temperature decrease, and the refrigeration working medium at normal temperature and normal pressure is expanded by the expander E1 to become a refrigeration working medium at low temperature and low pressure.

[0023] Here, in order to cool the fluid, particularly LNG, the cooling loop includes a heat exchanger 6, where the fluid enters the heat exchanger 6 through a fluid inlet pipe section L1 and then flows out of the heat exchanger 6 through a fluid outlet pipe section L2. In the heat exchanger 6, heat is exchanged between the refrigeration working medium at low temperature and low pressure that has cryogenic capability and the cooled fluid. Specifically, the cooled fluid transfers heat to the refrigeration working medium at low temperature and low pressure, thereby further reducing the temperature of the cooled fluid. The heat exchanger 6 may be a multi-flow heat exchanger. As shown in FIG. 2, in at least part of a section of the heat exchanger 6, a flowing direction of the fluid is opposite to a flowing direction of the refrigeration working medium, that is, the fluid and the refrigeration working medium perform heat transfer in the heat exchanger 6 in a relatively counter-flow manner, which can improve the efficiency of heat transfer and the cooling effect of the cooled fluid.

[0024] Meanwhile, in the heat exchanger 6, the refrigeration working medium at low temperature and low pressure still has a low temperature after absorbing the heat of the cooled fluid, a regenerative heat exchanger 5 is further provided, and in the regenerative heat exchanger 5, the refrigeration working medium output by the heat exchanger 6 is used to cool the refrigeration working medium at normal temperature and high pressure at the inlet of the expander E1, so as to further reduce the air intake temperature of the expander E1, thereby achieving the purpose of saving energy. Similarly, as shown in FIG. 2, in at least part of a section of the regenerative heat exchanger 5, a flowing direction of the refrigeration working medium at normal temperature and high pressure at the inlet of the expander E1 is opposite to a fluid flowing direction of the refrigeration working medium output by the heat exchanger 6, that is, the two kinds of refrigeration working media perform heat transfer in the regenerative heat exchanger 5 in a relatively counter-flow manner, which can improve the efficiency of heat transfer and the cooling effect. Here, in order to ensure that the cooled fluid and the refrigeration working medium do not emit the cold quantity to the external environment, a thermal insulation apparatus 4 is provided, the regenerative heat exchanger 5 and the heat exchanger 6 are provided in the thermal insulation apparatus 4, the heat exchange between the cooled fluid and the refrigeration working medium at low temperature and the external environment is effectively isolated, and the effect of the whole cooling system is improved.

[0025] Therefore, the refrigeration working medium sequentially flows through the first-stage compressor C1, the cooler 3, the second-stage compressor C2, the cooler 3, the third-stage compressor C3, the cooler 3, the regenerative heat exchanger 5, the expander E1, the heat exchanger 6, and the regenerative heat exchanger 5, and then returns to the inlet of the first-stage compressor C1, thereby completing one cycle in the cooling loop. The reciprocating cycle can provide continuous cryogenic cooling capability to the cooled fluid.

[0026] The first-stage compressor C1, the second-stage compressor C2, and the third-stage compressor C3 may be axial compressors and / or centrifugal compressors, and the expander E1 may be an axial expander or a centrifugal expander.

[0027] Since the compressor converts external energy into internal energy of the compressed gas, the compressor needs to be driven by external power to operate. In the present embodiment, the cooling loop further includes a first motor 7 and a second motor 8, the first motor 7 is configured to drive the first-stage compressor C1, and the second motor 8 is configured to drive the second-stage compressor C2 and the third-stage compressor C3. Specifically, as shown in FIG. 2, the second-stage compressor C2, the third-stage compressor C3, and the second motor 8 are connected by a common rotating shaft. Therefore, only one second motor 8 is used to drive the second-stage compressor C2 and the third-stage compressor C3.

[0028] The refrigeration working medium expands in the expander E1, and then does work on the expander E1, such that the expander E1 rotates to output mechanical energy. Here, in order to improve the operation effect of the system by using the energy output by the expander E1, as shown in FIG. 2, the expander E1, the first motor 7, and the first-stage compressor C1 are mounted on a common rotating shaft to form a compression and expansion integrated machine 1, such that the mechanical energy output by the first motor 7 and the mechanical energy output by the expander E1 can be transmitted to the first-stage compressor C1 through the common rotating shaft together, thereby improving the energy utilization efficiency. Alternatively, of course, the expander E1 may be mounted on a common rotating shaft with the second-stage compressor C2 and / or the third-stage compressor C3 to form a compression and expansion integrated machine, while the first-stage compressor C1 is driven by the motor separately; or two expanders which are arranged in series or in parallel may be provided, and each expander and the corresponding compressor may be coaxial to form a compression and expansion integrated machine to drive the compressor. It is claimed that the compression and expansion integrated machine may include the compressors and the expander which rotate coaxially, or may include the compressor, the expander and the motor which rotate coaxially.

[0029] Further alternatively, in order to improve the refrigeration capacity of the cooling loop, a plurality of compressors, a plurality of expanders, and three or more motors may be included. Three or more compressors are provided, and two or more expanders are provided, where the plurality of compressors are arranged in series, in parallel, or in series and in parallel. Specifically, each compressor may be driven by the motor alone, or may be driven coaxially by the motor and the expander together, thereby constituting the cryogenic type boil-off gas cooling system having higher refrigeration capacity.

[0030] As shown in FIG. 2, a bypass branch is further provided in the cooling loop. Specifically, an upstream end of the bypass branch is connected to a pipe section between the cooler 3 and the regenerative heat exchanger 5, and a downstream end of the bypass branch is connected to a pipe section between the regenerative heat exchanger 5 and the first-stage compressor C1, so as to partially deliver the refrigeration working medium at high pressure that is compressed by three stages into the inlet of the first-stage compressor C1 for anti-surge backflow and pressure and temperature regulation during startup in the system. Further, in order to achieve a regulating effect, a regulating valve 10 is preferably provided on the bypass branch and configured to regulate the refrigeration working medium flowing from the inlet of the expander E1 to the outlet of the expander E1 via the bypass branch, that is, to regulate the refrigeration working medium compressed by three stages and flowing to the inlet of the first-stage compressor C1 via the bypass branch, particularly regulate the flow or pressure. In this way, the amount of the refrigeration working medium flowing to the expander E1 can be directly regulated and controlled, and the flow of the refrigeration working media in the three stages of compressors is increased. Therefore, when the compressor or the expander has surging, the regulating valve 10 can be opened to regulate the operating state of the compressor or the expander, thereby eliminating the surging phenomenon and preventing the compressor or the expander from being damaged or destroyed by surging. Specifically, at the start of the cooling system, the regulating valve 10 is fully opened; and when the cooling system stably operates, the regulating valve 10 is then completely closed.

[0031] The required cold quantity of the cooled fluid constantly changes under the influence of various factors, and the cold quantity provided by the refrigeration working medium in the cooling loop constantly changes under the influence of various factors, such that the operating condition of the cooling loop constantly changes. In order to ensure that the cooling loop can provide a reliable and stable cooling effect for the cooled fluid under the condition of change, the cooling system of the present disclosure also has variable operating condition regulation capacity.

[0032] As shown in FIG. 2, the cooling system includes a sensing apparatus 11, specifically a temperature sensor, and the sensing apparatus 11 is provided at the outlet of the expander E1, specifically at a pipe section between the outlet of the expander E1 and the heat exchanger 6, and is configured to detect the temperature of the refrigeration working medium at low temperature and low pressure at the outlet of the expander E1. With the cooling system of the present disclosure, when the state of the cooled fluid in the heat exchanger 6 changes, for example, the flow changes or the temperature changes, that is, the cold quantity changes. For example, if the required cold quantity is increased, the operating condition of the refrigeration working medium does not change at this moment, but when heat exchange is generated in the heat exchanger 6, the required cold quantity of the fluid is increased, and the cold supply quantity of the refrigeration working medium does not change temporarily, which directly results in that the temperature of the refrigeration working medium flowing out of the heat exchanger 6 is increased, and then when the flow speed and the flow of the refrigeration working medium in the cooling loop do not change, the temperature of the refrigeration working medium at the outlet of the expander E1 is increased, and the cold supply quantity provided is insufficient, thereby deteriorating the cycle. With the same logic, a decrease in the required cold quantity will cause a decrease in the temperature of the refrigeration working medium at the outlet of the expander E1, a decrease in the cold supply quantity will cause an increase in the temperature of the refrigeration working medium at the outlet of the expander E1, and an increase in the cold supply quantity will cause a decrease in the temperature of the refrigeration working medium at the outlet of the expander E1.

[0033] The cooling system further includes a controller 9. The controller 9 is connected to the sensing apparatus 11 and can receive data detected by the sensing apparatus 11. The controller 9 may also be connected to the first motor 7 and the second motor 8, and the controller 9 can control rotating speeds of the first motor 7 and the second motor 8 based on the data of the sensing apparatus 11, so as to change the flow speed, namely the circulation multiplying power, of the refrigeration working medium in the cooling loop. Therefore, the amount of the refrigeration working medium flowing through the heat exchanger 6 in unit time can be regulated, thus the cold quantity provided by the cooling loop to the cooled fluid is regulated, and it is ensured that the cooled fluid can be sufficiently, reliably and stably cooled. Here, when the controller 9 performs regulation, the rotating speeds of the first motor 7 and the second motor 8 may be controlled based on a temperature value detected by the single sensor apparatus 11, or a speed of change (derivative of the temperature value) of the temperature value detected by the single sensor apparatus 11, or both the temperature value detected by the single sensor apparatus 11 and the speed of change thereof.

[0034] In order to ensure that the cooling loop provides the proper cold supply quantity to match the required cold quantity of the cooled fluid to improve the efficiency of the cooling loop, a predetermined value SP is provided in the controller 9, and when an actual value PV detected by the sensing apparatus 11 is different from the predetermined value SP, the controller 9 regulates the rotating speeds of the first motor 7 and the second motor 8 using a PID control manner so as to regulate a circulation speed of the refrigeration working medium in the cooling loop and thus regulate a refrigeration amount provided by the cooling loop until the actual value PV is the same as the predetermined value SP. In particular, additionally, the predetermined value may be regulated manually or automatically. In particular, when the state of the fluid in storage changes or the refrigeration working medium changes, for example, the temperature increases, and when it is clear that the required cold quantity of the fluid or the cold supply quantity of the refrigeration working medium changes, the predetermined value can be regulated manually or automatically to adapt to the change in the required cold quantity or the cold supply quantity.

[0035] A specific regulation method is as shown in FIG. 1. After the required cold quantity and / or the cold supply quantity changes / change, the sensing apparatus 11 obtains the actual value PV detected by a monitoring point, when the actual value PV is different from the predetermined value SP, it indicates that the required cold quantity and the cold supply quantity are in an unmatched state, the controller 9 regulates the rotating speeds of the first motor 7 and the second motor 8 using a PID regulation method, and herein, the rotating speeds or rotating frequencies of the first motor 7 and the second motor 8 are continuously variable. Specifically, for example, when the actual value PV is greater than the predetermined value SP, the controller 9 increases the rotating speeds of the first motor 7 and the second motor 8. When the actual value PV is less than the predetermined value SP, the controller 9 decreases the rotating speeds of the first motor 7 and the second motor 8 until the actual value PV is the same as the predetermined value SP, which indicates that the required cold quantity and the cold supply quantity are in a matched state.

[0036] The PID regulation mode has the advantages of simple control, safety, reliability and rapid regulation, such that the cooling system can correspondingly regulate the cold supply quantity along with the change of the operating condition, the variable operating condition regulation with the cold quantity ranging from 0 to 100% is realized, and therefore, the power consumption and the required cold quantity of the cooling system are matched with each other, and the energy utilization efficiency is improved.Embodiment 2:

[0037] The arrangement mode of Embodiment 2 is shown in FIG. 3, and details of the same parts as those in Embodiment 1 are not repeated herein. Embodiment 2 differs from Embodiment 1 in that a sensing apparatus 11 is arranged on an outlet pipeline of a refrigeration working medium of a heat exchanger 6 and configured to detect the temperature of the refrigeration working medium after absorbing heat of a cooled fluid in the heat exchanger 6. It is then likewise possible to reflect whether the required cold quantity and the cold supply quantity are matched at the monitoring point.

[0038] The control method of Embodiment 2 is the same as that of Embodiment 1, as shown in FIG. 1, which is not repeated herein.Embodiment 3:

[0039] The arrangement mode of Embodiment 3 is shown in FIG. 4, and details of the same parts as those in Embodiment 1 are not repeated herein. Embodiment 3 differs from Embodiment 1 in that a sensing apparatus 11 is arranged on an inlet pipeline of a refrigeration working medium of an expander E1 and configured to detect the temperature of the refrigeration working medium at an inlet of the expander E1. It is then likewise possible to reflect whether the required cold quantity and the cold supply quantity are matched at the monitoring point.

[0040] The control method of Embodiment 3 is the same as that of Embodiment 1, as shown in FIG. 1, which is not repeated herein.Embodiment 4:

[0041] The arrangement mode of Embodiment 4 is shown in FIG. 5, and details of the same parts as those in Embodiment 1 are not repeated herein. Embodiment 4 differs from Embodiment 1 in that a sensing apparatus 11 is directly arranged on a fluid outlet pipe section L2 of a cooled fluid of a heat exchanger 6 and configured to detect the temperature of a refrigeration working medium in the fluid outlet pipe section L2 of the cooled fluid of the heat exchanger 6. It is then likewise possible to reflect whether the required cold quantity and the cold supply quantity are matched at the monitoring point.

[0042] The control method of Embodiment 4 is the same as that of Embodiment 1, as shown in FIG. 1, which is not repeated herein.

[0043] Although in the above described embodiments, the sensor apparatus 11 is provided at only one monitoring point, it is alternatively possible to provide two or more sensor apparatuses 11 in the cooling system, and the sensor apparatuses 11 are arranged at different locations respectively and configured to more quickly monitor a change in the required cold quantity of the fluid or a change in the cold supply quantity of the refrigeration working medium. For example, the sensing apparatuses may be provided at a refrigeration working medium inlet and a refrigeration working medium outlet of the heat exchanger, such that the temperature change of the refrigeration working medium and the temperature difference of the refrigeration working medium at the inlet and the outlet of the heat exchanger can be monitored in real time, and the operating condition change of the refrigeration working medium can be detected more quickly. Alternatively, the sensing apparatuses are arranged at a fluid inlet and a fluid outlet of the heat exchanger, such that the temperature change of the fluid and the temperature difference of the fluid at the inlet and the outlet of the heat exchanger can be monitored in real time, and the operating condition change of the fluid can be detected more quickly. Further, during regulation, the controller may regulate the motor by using PID control based on data (including a temperature value, a speed of change of the temperature value, etc.) of the single sensing apparatus, or based on the difference value of the plurality of sensing apparatuses, or based on data (including a temperature value, a speed of change of the temperature value, etc.) of the single sensing apparatus, the difference value of the plurality of sensing apparatuses, and / or a rate of change of the difference value of the plurality of sensing apparatuses (a derivative of the difference value of the plurality of sensing apparatuses). In particular, in order to enable a simple, quick and safe regulation mode, although the plurality of sensing apparatuses are provided in the cooling system, the controller may perform regulation based on the data of only one sensing apparatus when performing the control and regulation. Alternatively, the regulation is performed using data of corresponding different individual sensing apparatuses in different situations, but data of only one sensing apparatus is used in one situation.

[0044] After implementation, the present disclosure has the following beneficial effects: through the cooling system with the variable operating condition regulation function for the fluid, the cooling system includes the expander, the compressor driven by the motor with the rotating speed adjustable, the controller and the sensing apparatus, the sensing apparatus is configured to detect the temperature of the fluid and / or the refrigeration working medium, the controller can receive the data of the sensing apparatus and can control the rotating speed of the motor based on the data of the sensing apparatus, and it can be ensured that the temperature of the cooled fluid is kept at the predetermined value by regulating the rotating speed of the motor when the required cold quantity of the cooled fluid and / or the cold quantity provided by the refrigeration working medium are / is changed. Particularly, the control is carried out in a PID regulation mode, and the system has the advantages of simple control, safety, reliability and rapid regulation, such that the cooling system of the present disclosure can correspondingly regulate the cold quantity along with the change of operating conditions, and the variable operating condition regulation with the cold quantity ranging from 0 to 100% is realized.

[0045] The above disclosure is only a few of preferred embodiments of the present disclosure. Of course, they can not be used to limit the scope of the present disclosure, and therefore, equivalent changes according to the claims of the present disclosure are still covered by the scope of the present disclosure.

Claims

1. A cooling system with a variable operating condition regulation function for a fluid, comprising a cooling loop configured to cool the fluid, the cooling loop comprising: a compressor, configured to compress a refrigeration working medium of the cooling system; a cooler, configured to cool the compressed refrigeration working medium; an expander, configured to expand the cooled refrigeration working medium; a motor, capable of driving the compressor to compress the refrigeration working medium, wherein a rotating speed of the motor is adjustable; and a heat exchanger, configured to generate heat exchange between a cooled fluid and the expanded refrigeration working medium, wherein the cooling system further comprises a controller and a sensing apparatus, the sensing apparatus is configured to detect a temperature of the fluid and / or the refrigeration working medium, the sensing apparatus and the motor are connected to the controller, and the controller is configured to receive data of the sensing apparatus and control the rotating speed of the motor based on the data of the sensing apparatus.

2. The cooling system according to claim 1, wherein the rotating speed of the motor is continuously variable.

3. The cooling system according to claim 1 wherein the sensing apparatus is provided on at least one of an inlet pipe section of the expander, a pipe section between an outlet of the expander and the heat exchanger, an outlet pipe section of the cooled fluid of the heat exchanger, or an outlet pipe section of the refrigeration working medium of the heat exchanger.

4. The cooling system according to claim 3, wherein a corresponding predetermined value is provided in the controller for a temperature-related value of the refrigeration working medium or a temperature-related value of the cooled fluid at a location where the sensing apparatus is mounted; and when an actual value detected by the sensing apparatus is different from the predetermined value, the controller regulates the rotating speed of the motor until the actual value is the same as the predetermined value.

5. The cooling system according to claim 4, wherein the controller regulates the rotating speed of the motor using a PID manner; the predetermined value is set in a variable manner; when the actual value detected by the sensing apparatus is greater than the predetermined value, the controller increases the rotating speed of the motor; and when the actual value detected by the sensing apparatus is less than the predetermined value, the controller decreases the rotating speed of the motor.

6. The cooling system according to claim 4, wherein the temperature-related value is a temperature value detected by a single sensing apparatus, a speed of change of the temperature value detected by the single sensing apparatus, a difference value of the temperature values detected by a plurality of sensing apparatuses, and / or a speed of change of the difference value of the temperature values detected by the plurality of sensing apparatus.

7. The cooling system according to claim 1, wherein a flowing direction of fluid in at least part of a section of the heat exchanger is opposite to a flowing direction of the expanded refrigeration working medium, wherein the refrigeration working medium adopts inert gas; and the fluid is liquefied natural gas, carbon dioxide, hydrogen, or helium, or a mixed gas of at least two of the liquefied natural gas, the carbon dioxide, the hydrogen, or the helium.

8. The cooling system according to claim 7, wherein the refrigeration working medium is selected from He, N2, H2, Ne, or a mixed gas of at least two of He, N2, H2, or Ne.

9. The cooling system according to claim 1, wherein the cooling loop further comprises a regenerative heat exchanger, and the refrigeration working medium flowing out of the heat exchanger exchanges heat with the refrigeration working medium prior to entering the expander in the regenerative heat exchanger; and the heat exchanger and the regenerative heat exchanger are mounted in a thermal insulation apparatus.

10. The cooling system according to any one of claims 1 to 9, wherein at least two compressors are provided, and the at least two compressors are arranged in the cooling loop in series and / or in parallel, such that the refrigeration working medium flows through the at least two compressors in series and / or in parallel, wherein an outlet of each compressor is provided with a cooler; the refrigeration working medium expands in the expander to enable the expander to output energy, and at least one of the at least two compressors receives the energy output by the expander; and at least one of the at least two compressors is driven by the motor.

11. The cooling system according to claim 10, wherein at least one of the at least two compressors is arranged in a co-axial drive with the motor and the expander, such that the at least one compressor is driven by energy output by the motor and the expander together.

12. The cooling system according to claim 10, wherein at least two expanders are provided, and the at least two expanders are arranged in the cooling loop in series and / or in parallel, such that the refrigeration working medium flows through the at least two expanders in series and / or in parallel.

13. The cooling system according to any one of claims 1 to 12, wherein the expander is provided with a bypass branch, one end of the bypass branch is connected to an inlet of the expander, the other end of the bypass branch is connected to an outlet of the expander, and a regulating valve is provided on the bypass branch and configured to regulate the refrigeration working medium flowing from the inlet of the expander to the outlet of the expander via the bypass branch.

14. The cooling system according to claim 13, wherein one end of the bypass branch is connected to a pipe section of the inlet of the expander located at an upstream part of the heat exchanger, and the other end of the bypass branch is connected to a pipe section of the outlet of the expander located at a downstream part of the heat exchanger.

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