A medium constant temperature method suitable for cryogenic pressure vessel cold insulation performance test

Abstract

The present invention relates to a method for constant temperature of a medium before a cold insulation performance test of a cryogenic pressure vessel. The method comprises the following steps: when the device is powered on, a control module automatically detects the state of a solenoid valve and sets the solenoid valve to a normally closed state; when the control module detects that all valves and liquid level sensors are normal, a medium is introduced into an inlet L i of a medium to be constant temperature, and the medium is output from an outlet Lo of the constant temperature medium to a thermal insulation performance test device of the cryogenic pressure vessel, and a rough electric power setting value F is calculated; according to the calculated value of the rough electric power setting value F, all programmable resistance heaters are simultaneously energized to increase the temperature, and a target temperature T of the medium is calculated; when the values ​​of all temperature sensors reach the target temperature T, a first solenoid valve is opened and values ​​are re-applied according to a preset rule; and a collection module collects the values ​​of temperature sensors on output pipes to ensure that the temperature of the medium is always constant at a certain constant temperature preset value, and that the temperature of the constant temperature medium is always within a constant range, thereby meeting the requirements of the cold insulation performance test of the cryogenic pressure vessel.

Description

Technical Field

[0001] The invention belongs to the technical field of cold preservation performance testing of cryogenic pressure vessels, and particularly relates to a method for constant temperature of a medium before cold preservation performance testing of a cryogenic pressure vessel. Background Art

[0002] Stationary vacuum insulated cryogenic pressure vessels are important industrial equipment, widely used in fields such as liquefied natural gas, refrigerants, medical treatment, and scientific research. Therefore, they must undergo rigorous inspection and testing during production and use to ensure their safety and reliability.

[0003] Before testing the cold-keeping performance of a fixed vacuum insulated cryogenic pressure vessel, the test medium needs to be passed into the vessel. At this time, it is necessary to ensure that the outlet temperature of the constant temperature medium remains at a constant value to meet the temperature required by the cold-keeping performance test conditions of the cryogenic pressure vessel. Summary of the Invention

[0004] In order to solve the problem that there is a lack of a method to ensure that the medium is maintained at a preset constant value before the cold preservation performance test of the cryogenic pressure vessel.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for maintaining a constant temperature of a medium before a cryogenic pressure vessel cold-insulation performance test, comprising a thermostat, the thermostat comprising a thermostat box, the thermostat box comprising an external shell side and an internal tube side, the thermostat box having an external temperature-controlled medium inlet Li, the temperature-controlled medium inlet Li being connected to the tube side inside the thermostat box via an input pipe, the input pipe having a first solenoid valve and a temperature sensor, the shell side being divided into a plurality of constant temperature chambers, each constant temperature chamber inside the shell side being equipped with a temperature sensor, a tube side being provided in the middle of each constant temperature chamber, a programmable resistance heater being provided in the middle of each tube side, the temperature sensor being connected to an acquisition module via a data bus, the acquisition module being connected to a control module, the end of the tube side being connected to a constant temperature medium outlet Lo via an output pipe, the medium outlet Lo being located on a cryogenic pressure vessel cold-insulation performance test device;

[0007] The shell side top is provided with a pressure sensor and a liquid level sensor, and the pressure sensor and the liquid level sensor are connected to the acquisition module through the data bus;

[0008] The right side of the bottom end of the shell side is connected to a medium inlet L1 through a first pipe. The first pipe has a second solenoid valve. The medium inlet L1 is located on a first medium storage tank. The second solenoid valve is controlled by a control module.

[0009] The bottom of the shell side is connected to a cooling port L2 through a second pipe. The second pipe is provided with a third solenoid valve. The third solenoid valve is controlled by a control module. The cooling port L2 is located on a second medium storage tank.

[0010] The output pipeline is also provided with a residual pressure discharge valve and a temperature sensor, and the residual pressure discharge valve is controlled by a control module;

[0011] The top of the shell side is connected to an overpressure reflux port L3 through a third pipe, and a fourth solenoid valve is provided on the third pipe. The overpressure reflux port L3 is located on the third medium storage tank, and the fourth solenoid valve is controlled by a control module.

[0012] The method is as follows:

[0013] Step 1: Turn on the power, and the control module automatically detects the status of the first solenoid valve, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, and sets them to the normally closed state;

[0014] Step 2: After the control module detects that all valves and liquid level sensors are normal, it introduces the medium to the constant temperature medium inlet Li, and the medium is output from the constant temperature medium outlet Lo to the cryogenic pressure vessel insulation performance test device, and then extracts the medium type and the instantaneous flow value L of the constant temperature medium returned by the cryogenic pressure vessel insulation performance test device. t And the values ​​of all temperature sensors in all constant temperature chambers and calculate the average temperature t 平均 , finally, calculate the rough value F of electric power according to the type of medium;

[0015] Step 3: Based on the calculated value of the rough set value of electric power F, all programmable resistance heaters are energized and heated simultaneously to calculate the target temperature T of the medium;

[0016] Step 4: Compare the received values ​​of all temperature sensors in the constant temperature chamber with the target temperature T. When the values ​​of all temperature sensors in the constant temperature chamber reach the target temperature T, open the first solenoid valve and re-apply the values ​​according to the preset rules;

[0017] Step 5: The acquisition module collects the value of the temperature sensor on the output pipe, that is, the temperature t1. If the absolute value of t1 minus the constant temperature preset value is not greater than 1, the fine adjustment process will not be entered. Otherwise, the fine adjustment process will be entered to complete power fine adjustment and fine adjustment. While the outlet flow of the overpressure return port L3 changes, the medium temperature is always kept constant at a certain constant temperature preset value.

[0018] Step 6: During the constant temperature process, the control module analyzes the instantaneous flow value L of the cryogenic pressure vessel cold preservation performance test device sent back by the acquisition module in real time. t / min is compared with the initial flow value L0 / min. When the flow difference exceeds the preset flow difference value, the rough electric power value F is recalculated and revalued according to the preset rules;

[0019] Step 7: When the test is completed and the acquisition module receives the test end signal from the cryogenic pressure vessel cold preservation performance test device, the control system resets the power of all programmable resistance heaters and cuts off the power supply, while opening the residual pressure discharge valve and closing the first solenoid valve.

[0020] Furthermore, before executing step S2, the liquid level sensor signal is extracted. When the thermostat media level is lower than the preset position, an audible and visual alarm is issued, and the second solenoid valve is automatically opened to replenish the liquid through the media storage tank. If the liquid level sensor on the thermostat fails to detect a normal signal within the preset time, it will prompt that the media replenishment has failed. Please check whether the second solenoid valve or the first media storage tank is normal, and cut off the main power supply to prevent the thermostat from drying out.

[0021] Furthermore, the rough setting value F of electric power is calculated as follows:

[0022] F=Q / 3600;

[0023] Q=C1m△t;

[0024] m=L0 / min*60*1.2555;

[0025] Where m is the constant temperature medium content per hour, Q is the total heat of the constant temperature medium, C1 is the specific heat of the constant temperature medium, and △t is the temperature to be heated.

[0026] Furthermore, three square guide baffle plates are fixed inside the shell side, and there is a gap between the square guide baffle plates and the left side and right side of the shell side. The three square guide baffle plates divide the shell side into four equal-sized constant temperature chambers, which are the first constant temperature chamber, the second constant temperature chamber, the third constant temperature chamber, and the fourth constant temperature chamber from top to bottom. The tube side is curved and is divided into the first tube section, the second tube section, the third tube section, and the fourth tube section from top to bottom. Each section is arranged in a corresponding constant temperature chamber.

[0027] The programmable resistance heaters are respectively a first programmable resistance heater, a second programmable resistance heater, a third programmable resistance heater and a fourth programmable resistance heater from top to bottom, wherein the first programmable resistance heater is fixed on the left side of the first constant temperature chamber, the third programmable resistance heater is fixed on the left side of the third constant temperature chamber, the second programmable resistance heater is fixed on the right side of the second constant temperature chamber, and the fourth programmable resistance heater is fixed on the right side of the fourth constant temperature chamber;

[0028] The preset rules are: attaching 40% of the rough electric power setting value F to the first programmable resistor heater; attaching 30% of the rough electric power setting value F to the second programmable resistor heater; attaching 20% ​​of the rough electric power setting value F to the third programmable resistor heater; and attaching 10% of the rough electric power setting value F to the fourth programmable resistor heater.

[0029] Furthermore, the target temperature T of the medium is calculated as follows:

[0030] T=t 平均 +△t;

[0031] △t=Q / (C2*M);

[0032] t 平均 = the value of all temperature sensors in the constant temperature chamber / the number of temperature sensors in the constant temperature chamber;

[0033] Where: Q is the total heat of the constant temperature medium, C2 is the specific heat of the medium (4.2 kJ / kg °C), M is the volume mass of the medium at the set liquid level, and △t is the temperature to be heated.

[0034] Furthermore, it also includes liquid level control, which uses a dual protection algorithm to ensure normal liquid level and pressure of the system. The dual protection algorithm is as follows:

[0035] 1. Liquid level control is achieved by transmitting low and high liquid level signals via the liquid level sensor. When the acquisition module receives a low liquid level signal, the control module cuts off the heating power supply of all programmable resistance heaters and opens the second solenoid valve for liquid replenishment. When a high liquid level signal is received, the second solenoid valve is closed to stop liquid replenishment. When the liquid level sensor or the second solenoid valve fails, the fourth solenoid valve automatically opens to drain liquid to avoid overpressure events.

[0036] 2. When the pressure value of the pressure sensor is greater than or equal to 0.01MPa, the third solenoid valve is automatically opened to release the pressure and control the liquid level within the preset range.

[0037] Furthermore, in the event of a sudden power outage, all components on the thermostat are controlled to reset, the residual pressure discharge valve is normally open, and the first solenoid valve, the second solenoid valve and the fourth solenoid valve are normally closed.

[0038] Furthermore, it also includes over-temperature control: when an unexpected flow drop event occurs during the constant temperature process, if the temperature t1 is within 5°C of the preset value, the heater power is adjusted according to step 5. If it exceeds 5°C, the control module automatically opens the third solenoid valve to discharge the high-temperature medium. At the same time, the liquid level sensor cooperates to supplement the low-temperature medium to control the temperature and avoid over-temperature accidents.

[0039] Furthermore, the gap length is 20 mm, and the temperature sensor is fixed on the left side surface of each constant temperature cavity.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The acquisition module of the present invention collects the inlet temperature of the medium to be constant temperature, the temperature of each constant temperature chamber, the outlet temperature, the temperature difference and the instantaneous flow rate (volume), and cooperates with the control module to adjust the medium temperature, flow rate and liquid level in real time, so that the outlet temperature of the constant temperature medium can be maintained at a constant value and meet the temperature required by the cold preservation performance test conditions of the cryogenic pressure vessel.

[0042] (2) In the embodiment of the present invention, an adjustable precision-controlled resistance heater is used to convert electrical energy into medium heat within a specific temperature range. The total heat of the medium with a certain amount of thermal energy storage and the latent heat of vaporization and the specific heat of temperature rise of the medium required to maintain a constant temperature in the front-end cryogenic pressure vessel are precisely temperature-controlled and segmentedly exchanged on the surface of a small-diameter, multi-return, large-area pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the overall structure of an embodiment of the present invention;

[0044] Figure 2 Schematic diagram of the overall structure of the thermostat;

[0045] In the figure: 1-constant temperature box, 11-shell side, 111, first constant temperature chamber, 112-second constant temperature chamber, 113-third constant temperature chamber, 114-fourth constant temperature chamber, 12-pipe side, 121-first pipe section, 122-second pipe section, 123-third pipe section, 124-fourth pipe section, 13-second pipeline, 131-cooling port, 132-third solenoid valve, 133-second medium storage tank, 14-first pipeline, 141-medium inlet L1, 142-second solenoid valve, 143-first medium storage tank, 15-third pipeline, 151-overpressure reflux port, 152-fourth solenoid valve, 153-third Media storage tank, 16-pressure sensor, 17-liquid level sensor, 18-left side, 181-first programmable resistance heater, 182-third programmable resistance heater, 19-right side, 191-second programmable resistance heater, 192-fourth programmable resistance heater, 2-acquisition module, 21-data bus, 3-control module, 4-cryogenic pressure vessel cold insulation performance test device, 5-inlet Li for medium to be constant temperature, 51-input pipeline, 52-first solenoid valve, 53-temperature sensor, 6-constant temperature medium outlet Lo, 61-output pipeline, 62-residual pressure discharge valve, 7-square guide partition plate. DETAILED DESCRIPTION

[0046] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] See also Figure 1-2A method for constant temperature of a medium before testing the cold preservation performance of a cryogenic pressure vessel includes a constant temperature box 1, wherein the constant temperature box 1 includes an external shell side 11 and an internal tube side 12, and the outside of the constant temperature box 1 has an inlet Li5 for a medium to be constant temperature, and the inlet Li5 for the medium to be constant temperature is connected to the tube side 12 inside the constant temperature box 1 through an input pipe 51, and the input pipe 51 has a first solenoid valve 52 and a temperature sensor 53. The shell side is divided into multiple constant temperature chambers, and each constant temperature chamber inside the shell side is equipped with a temperature sensor, and a tube side is provided in the middle of each constant temperature chamber. A programmable resistance heater is installed in the middle of each tube side, and the temperature sensor is connected to the acquisition module 2 through a data bus 21, and the acquisition module 2 is connected to a control module 3. The end of the tube side is connected to the constant temperature medium outlet Lo6 through an output pipe 61.

[0048] The shell side top is provided with a pressure sensor 16 and a liquid level sensor 17 , and the pressure sensor 16 and the liquid level sensor 17 are connected to the acquisition module 2 via the data bus 21 .

[0049] The right side of the bottom end of the shell side 11 is connected to a medium inlet L1141 through a first pipe 14. The first pipe 14 has a second solenoid valve 142. The medium inlet L1 is located on a first medium storage tank 143. The second solenoid valve 142 is controlled by the control module 3.

[0050] The bottom of the shell side 11 is connected to a cooling port L2131 through a second pipe 13 . The second pipe 13 is provided with a third solenoid valve 132 . The third solenoid valve 132 is controlled by the control module 3 . The cooling port L2131 is located on a second medium storage tank 133 .

[0051] The output pipe 61 is further provided with a residual pressure discharge valve 62 and a temperature sensor. The residual pressure discharge valve 62 is controlled to be opened or closed by the control module 3 .

[0052] The top of the shell side is connected to an overpressure reflux port L3151 through a third pipe 15. The third pipe 15 is provided with a fourth solenoid valve 152. The overpressure reflux port L3151 is located on the third storage medium tank 153. The fourth solenoid valve 152 is controlled by the control module 3.

[0053] The method is as follows:

[0054] Step 1: Turn on the power, and the control module automatically detects the status of the first solenoid valve, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, and sets them to the normally closed state;

[0055] Step 2: After the control module detects that all valves and liquid level sensors are normal, it introduces the medium to the constant temperature medium inlet Li, and the medium is output from the constant temperature medium outlet Lo to the cryogenic pressure vessel insulation performance test device, and then extracts the medium type and the instantaneous flow value L of the constant temperature medium returned by the cryogenic pressure vessel insulation performance test device. t And the values ​​of all temperature sensors in all constant temperature chambers and calculate the average temperature t 平均 , finally, calculate the rough value F of electric power according to the type of medium;

[0056] Step 3: Based on the calculated value of the rough set value of electric power F, all programmable resistance heaters are energized and heated simultaneously to calculate the target temperature T of the medium;

[0057] Step 4: Compare the received values ​​of all temperature sensors in the constant temperature chamber with the target temperature T. When the values ​​of all temperature sensors in the constant temperature chamber reach the target temperature T, open the first solenoid valve and re-apply the values ​​according to the preset rules;

[0058] Step 5: The acquisition module collects the value of the temperature sensor on the output pipe, that is, the temperature t1. If the absolute value of t1 minus the constant temperature preset value is not greater than 1, the fine adjustment process will not be entered. Otherwise, the fine adjustment process will be entered to complete power fine adjustment and fine adjustment. While the outlet flow of the overpressure return port L3 changes, the medium temperature is always kept constant at a certain constant temperature preset value.

[0059] Step 6: During the constant temperature process, the control module analyzes the instantaneous flow value L of the cryogenic pressure vessel cold preservation performance test device sent back by the acquisition module in real time. t / min is compared with the initial flow value L0 / min. When the flow difference exceeds the preset flow difference value, the rough electric power value F is recalculated and revalued according to the preset rules;

[0060] Step 7: When the test is completed and the acquisition module receives the test end signal from the cryogenic pressure vessel cold preservation performance test device, the control system resets the power of all programmable resistance heaters and cuts off the power supply, while opening the residual pressure discharge valve and closing the first solenoid valve.

[0061] In this embodiment, the gap length is 20 mm, forming a good medium convection channel between the cavities. The length of the programmable resistance heater is 2 / 3 of the shell width.

[0062] See also Figure 1-2In the present invention, three square guide baffle plates 7 are fixed inside the shell side 11. There is a gap between the square guide baffle plates 7 and the left side 18 and the right side 19 of the shell side 11. The three square guide baffle plates 7 divide the shell side into four equal-sized constant temperature chambers, which are, from top to bottom, a first constant temperature chamber 111, a second constant temperature chamber 112, a third constant temperature chamber 113, and a fourth constant temperature chamber 114. The tube side 12 is curved and is divided into a first tube section 121, a second tube section 122, a third tube section 123, and a fourth tube section 124 from top to bottom. Each section is arranged in a corresponding constant temperature chamber. A temperature gradient is formed between the layers of the four inner cavities from top to bottom, increasing layer by layer. In this way, an internal circulation channel is formed between the layers on the basis of good medium convection between each cavity, in which the hot medium rises and the cold medium descends.

[0063] In the present invention, the programmable resistor heaters are respectively a first programmable resistor heater 181, a second programmable resistor heater 191, a third programmable resistor heater 182 and a fourth programmable resistor heater 192 from top to bottom. The first programmable resistor heater 181 is fixed on the left side 18 of the first constant temperature chamber 111, the third programmable resistor heater 182 is fixed on the left side 18 of the third constant temperature chamber 113, the second programmable resistor heater 191 is fixed on the right side 19 of the second constant temperature chamber 112, and the fourth programmable resistor heater 192 is fixed on the right side 19 of the fourth constant temperature chamber 114, ensuring that countless micro-convection channels are formed in each individual cavity, ensuring good heat exchange in the cavity.

[0064] See also Figure 1 The temperature sensor is fixed on the left side of each constant temperature chamber.

[0065] The constant temperature medium outlet Lo6 is located on the cryogenic pressure vessel cold preservation performance testing device 4 .

[0066] The present invention will be further described below with reference to a specific embodiment:

[0067] (1) Temperature control:

[0068] 1. After powering on, the control module automatically detects the status of the first solenoid valve, the second solenoid valve, the third solenoid valve and the fourth solenoid valve, and puts them in the normally closed state.

[0069] 2. Detect the liquid level sensor signal. When the thermostat's media level falls below a preset level, an audible and visual alarm sounds and the second solenoid valve automatically opens to replenish the media from the media storage tank. If the liquid level sensor on the thermostat fails to detect a normal signal within the set 5 minutes, indicating a media replenishment failure, check the second solenoid valve or the first media storage tank for proper function and disconnect the main power supply to prevent the thermostat from drying out.

[0070] 3. See Figure 1 After the control module detects that all valves and liquid level sensors are normal, it extracts the medium type and the instantaneous flow value L of the constant temperature medium sent back by the cryogenic pressure vessel cold insulation performance test device. t / min and the values ​​of all temperature sensors in all constant temperature chambers, divided into temperatures (temperature t2~temperature t5) according to the constant temperature chamber from top to bottom and calculate the average temperature t 平均 , t 平均 =t2+t3+t4+t5 / 4.

[0071] 4. Calculate the rough setting value F of electric power based on the type of medium, taking nitrogen as an example.

[0072] F=Q / 3600 (unit: kw)

[0073] Q=C1m△t=1.038*(L0 / min*60*1.2555)*221(unit: kj / h)

[0074] m=L0 / min*60*1.2555 (unit: kg)

[0075] △t=221℃ (△t: liquid nitrogen is heated from -196℃ to 25℃)

[0076] Where m is the nitrogen equivalent per hour, Q is the total heat of temperature rise of constant temperature nitrogen, and C1 is the specific heat of the constant temperature medium (here the specific heat of nitrogen is 1.038).

[0077] 5. Based on the calculated value of the rough power setting value F, the first to fourth programmable resistance heaters are energized to increase the temperature. The target temperature T of the medium is calculated according to the algorithm.

[0078] T=t 平均 +△t;

[0079] △t=Q / (C2*M);

[0080] Where: Q is the total heat of the constant temperature nitrogen, C2 is the specific heat of the medium (4.2 kJ / kg.°C), M is the volumetric mass of the medium at the set liquid level, and △t is the temperature to be heated.

[0081] 6. Compare the received values ​​of all temperature sensors in the constant temperature chamber (t2~t5) with the target temperature T. When the values ​​of all temperature sensors in the constant temperature chamber reach the target temperature T, open the first solenoid valve and re-apply the values ​​according to the following rules: 40%F power is attached to the first programmable resistance heater, 30%F power is attached to the second programmable resistance heater; 20%F power is attached to the third programmable resistance heater, and 10%F power is attached to the fourth programmable resistance heater.

[0082] 7. The acquisition module acquires the value of the temperature sensor on the output pipe, i.e., temperature t1. If the absolute value of (t1-25) is not greater than 1, the fine-tuning process will not be entered, where 25 refers to the constant temperature preset value; otherwise, the fine-tuning value P% is calculated. If P% is a positive value, the power of the first to fourth programmable resistance heaters is reduced by P% based on the original power; if P% is a negative value, the power of the first to fourth programmable resistance heaters is increased by P% based on the original power.

[0083] P%=100*(t1-25) / 25.

[0084] 8. During the constant temperature process, the control module analyzes the instantaneous flow value L of the cryogenic pressure vessel cold preservation performance test device sent back by the acquisition module in real time. t / min and initial flow value L t / min for comparison. When the flow difference exceeds 5%, recalculate the F value according to the algorithm and re-apply the value according to the following rules: 40% of the rough electric power setting value F is attached to the first programmable resistor heater; 30% of the rough electric power setting value F is attached to the second programmable resistor heater; 20% of the rough electric power setting value F is attached to the third programmable resistor heater; 10% of the rough electric power setting value F is attached to the fourth programmable resistor heater. Repeat step 7 to complete the system fine-tuning and fine-tuning. When the outlet flow of the overpressure return port L3 changes, the temperature can always be kept constant at a certain constant temperature preset value (25°C in this case).

[0085] 9. When the test is completed and the acquisition module receives the test end signal from the cryogenic pressure vessel cold preservation performance test device, the control system resets the power of the first programmable resistance heater to the fourth programmable resistance heater and cuts off the power supply, while opening the residual pressure discharge valve and closing the first solenoid valve.

[0086] 10. In case of sudden power outage, all components on the thermostat will be reset, the residual pressure discharge valve will be normally open, and the first solenoid valve, the second solenoid valve and the fourth solenoid valve will be normally closed to prevent the low-temperature medium from entering the back-end system and causing malfunctions when power is supplied.

[0087] Liquid level control:

[0088] Liquid level control uses a dual protection algorithm to ensure normal liquid level and pressure of the system.

[0089] 1. Liquid level control is achieved by transmitting low and high liquid level signals from the liquid level sensor. When the acquisition module receives a low liquid level signal, the control module cuts off the heating power from the first to the fourth programmable resistance heaters and opens the second solenoid valve to replenish liquid. When a high liquid level signal is received, the second solenoid valve closes to stop replenishing liquid. If the liquid level sensor or the second solenoid valve fails, the fourth solenoid valve automatically opens to drain liquid, preventing overpressure.

[0090] 2. When the pressure value of the pressure sensor is greater than or equal to 0.01MPa, the system automatically opens the third solenoid valve to release the pressure and control the liquid level within the preset range.

[0091] (3) Overtemperature control:

[0092] The thermostat of this invention is compatible with maintaining the temperature of nitrogen, oxygen, argon, LNG, and low-temperature carbon dioxide gases with flow rates ranging from 5L / min to 500L / min. If an unexpected flow drop occurs during the thermostatting process, such as a pipe detachment or leak, the system automatically adjusts (reduces) the heater power based on an algorithm if the temperature t1 is within 5°C of the preset value. If it exceeds 5°C, the control system automatically opens the third solenoid valve to discharge the high-temperature medium. Simultaneously, a liquid level sensor coordinates the replenishment of low-temperature medium to maintain temperature control and prevent overheating.

[0093] The medium can be pure water without chloride ions, and the constant temperature medium is compatible with gases gasified from low-temperature cryogenic pressure vessels, including nitrogen, oxygen, argon, LNG gas and carbon dioxide gas.

[0094] The outlet temperature of the constant temperature medium is controlled within a certain constant range. The constant temperature range of the medium is generally 25℃±1℃, but not limited to this. It can be adjusted according to actual conditions. The shell side is made of high-quality austenitic stainless steel.

[0095] The acquisition module uses RS485 communication interface to collect signals from six temperature sensors, pressure sensors, and liquid level sensors and detect the instantaneous flow value L of the constant temperature medium sent back. t / min, and sent to the control module.

[0096] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for constant temperature of medium before testing the cold-keeping performance of cryogenic pressure vessels, characterized in that: The thermostat comprises a thermostat, the thermostat comprising an external shell side and an internal tube side, the thermostat having an inlet Li for a medium to be kept at a constant temperature on the outside of the thermostat, the inlet Li for the medium to be kept at a constant temperature being connected to the tube side inside the thermostat via an input pipe, the input pipe being provided with a first solenoid valve and a temperature sensor, the shell side being divided into a plurality of constant temperature chambers, each constant temperature chamber inside the shell side being provided with a temperature sensor, a tube side being provided in the middle of each constant temperature chamber, a programmable resistance heater being provided in the middle of each tube side, the temperature sensor being connected to an acquisition module via a data bus, the acquisition module being connected to a control module, the end of the tube side being connected to an outlet Lo for the constant temperature medium via an output pipe, the medium outlet Lo being located on a cold-keeping performance test device for a cryogenic pressure vessel; The shell side top is provided with a pressure sensor and a liquid level sensor, and the pressure sensor and the liquid level sensor are connected to the acquisition module through the data bus; The right side of the bottom end of the shell side is connected to a medium inlet L1 through a first pipe. The first pipe has a second solenoid valve. The medium inlet L1 is located on a first medium storage tank. The second solenoid valve is controlled by a control module. The bottom of the shell side is connected to a cooling port L2 through a second pipe. The second pipe is provided with a third solenoid valve. The third solenoid valve is controlled by a control module. The cooling port L2 is located on a second medium storage tank. The output pipeline is also provided with a residual pressure discharge valve and a temperature sensor, and the residual pressure discharge valve is controlled by a control module; The top of the shell side is connected to an overpressure reflux port L3 through a third pipe, and a fourth solenoid valve is provided on the third pipe. The overpressure reflux port L3 is located on the third medium storage tank, and the fourth solenoid valve is controlled by a control module. The method is as follows: Step 1: Turn on the power, and the control module automatically detects the status of the first solenoid valve, the second solenoid valve, the third solenoid valve, and the fourth solenoid valve, and sets them to the normally closed state; Step 2: After the control module detects that all valves and liquid level sensors are normal, it introduces the medium to the constant temperature medium inlet Li, and the medium is output from the constant temperature medium outlet Lo to the cryogenic pressure vessel insulation performance test device, and then extracts the medium type and the instantaneous flow value L of the constant temperature medium returned by the cryogenic pressure vessel insulation performance test device. t And the values ​​of all temperature sensors in all constant temperature chambers and calculate the average temperature t 平均 , finally, calculate the rough value F of electric power according to the type of medium; Step 3: Based on the calculated value of the rough set value of electric power F, all programmable resistance heaters are energized and heated simultaneously to calculate the target temperature T of the medium; Step 4: Compare the received values ​​of all temperature sensors in the constant temperature chamber with the target temperature T. When the values ​​of all temperature sensors in the constant temperature chamber reach the target temperature T, open the first solenoid valve and re-apply the values ​​according to the preset rules; Step 5: The acquisition module collects the value of the temperature sensor on the output pipe, that is, the temperature t1. If the absolute value of t1 minus the constant temperature preset value is not greater than 1, the fine adjustment process will not be entered. Otherwise, the fine adjustment process will be entered to complete power fine adjustment and fine adjustment. While the outlet flow of the overpressure return port L3 changes, the medium temperature is always kept constant at a certain constant temperature preset value. Step 6: During the constant temperature process, the control module analyzes the instantaneous flow value L of the cryogenic pressure vessel cold preservation performance test device sent back by the acquisition module in real time. t Compare with the initial flow value L0. When the flow difference exceeds the preset flow difference value, recalculate the rough electric power value F and re-apply the value according to the preset rules. Step 7: When the test is completed and the acquisition module receives the test completion signal from the cryogenic pressure vessel cold insulation performance test device, the control system resets the power of all programmable resistance heaters and cuts off the power supply. At the same time, the residual pressure discharge valve is opened and the first solenoid valve is closed. Three square guide baffle plates are fixed inside the shell side, with gaps between the square guide baffle plates and the left side and right side of the shell side. The three square guide baffle plates divide the shell side into four equal-sized constant temperature chambers, which are the first constant temperature chamber, the second constant temperature chamber, the third constant temperature chamber, and the fourth constant temperature chamber from top to bottom. The tube side is curved and is divided into the first tube section, the second tube section, the third tube section, and the fourth tube section from top to bottom, and each section is arranged in a corresponding constant temperature chamber. The programmable resistance heaters are respectively a first programmable resistance heater, a second programmable resistance heater, a third programmable resistance heater and a fourth programmable resistance heater from top to bottom, wherein the first programmable resistance heater is fixed on the left side of the first constant temperature chamber, the third programmable resistance heater is fixed on the left side of the third constant temperature chamber, the second programmable resistance heater is fixed on the right side of the second constant temperature chamber, and the fourth programmable resistance heater is fixed on the right side of the fourth constant temperature chamber; The preset rule is: 40% of the rough electric power setting value F is attached to the first programmable resistance heater; 30% of the rough electric power setting value F is attached to the second programmable resistance heater; Attach 20% of the rough electric power setting value F to the third programmable resistance heater; attach 10% of the rough electric power setting value F to the fourth programmable resistance heater.

2. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: Before executing step S2, extract the liquid level sensor signal. When the thermostat media level is lower than the preset position, an audible and visual alarm is issued, and the second solenoid valve is automatically opened to replenish the liquid through the media storage tank. If the liquid level sensor on the thermostat fails to detect a normal signal within the preset time, it will prompt that the media replenishment has failed. Please check whether the second solenoid valve or the first media storage tank is normal, and cut off the main power supply to prevent the thermostat from drying out.

3. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: The calculation of the rough value F of electric power is as follows: F=Q / 3600; Q=C1m△t; m=L0 / min*60*1.2555; Where m is the constant temperature medium content per hour, Q is the total heat of the constant temperature medium, C1 is the specific heat of the constant temperature medium, and △t is the temperature to be heated.

4. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: The target temperature T of the medium is calculated as follows: T=t 平均 +△t; △t=Q / (C2*M); t 平均 = the value of all temperature sensors in the constant temperature chamber / the number of temperature sensors in the constant temperature chamber; Where: Q is the total heat of the constant temperature medium, C2 is the specific heat of the medium (4.2 kJ / kg °C), M is the volume mass of the medium at the set liquid level, and △t is the temperature to be heated.

5. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: The fine adjustment process is as follows: Calculate the fine adjustment value P, the calculation method of the fine adjustment value P is: P=100*(t1-constant temperature preset value) / constant temperature preset value; If the fine adjustment value P% is a positive value, the power of all programmable resistance heaters will be reduced by P% based on the original power; if the fine adjustment value P is a negative value, the power of each programmable resistance heater will be increased by P% based on the original power.

6. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: It also includes liquid level control, which uses a dual protection algorithm to ensure normal liquid level and pressure in the system. The dual protection algorithm is as follows:

1. Liquid level control is achieved by transmitting low and high liquid level signals via the liquid level sensor. When the acquisition module receives a low liquid level signal, the control module cuts off the heating power supply of all programmable resistance heaters and opens the second solenoid valve for liquid replenishment. When a high liquid level signal is received, the second solenoid valve is closed to stop liquid replenishment. When the liquid level sensor or the second solenoid valve fails, the fourth solenoid valve automatically opens to drain liquid to avoid overpressure events.

2. When the pressure value of the pressure sensor is greater than or equal to 0.01MPa, the third solenoid valve is automatically opened to release the pressure and control the liquid level within the preset range.

7. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: In case of sudden power failure, all components on the thermostat are controlled to reset, the residual pressure discharge valve is normally open, and the first solenoid valve, the second solenoid valve and the fourth solenoid valve are normally closed.

8. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: It also includes over-temperature control: when an unexpected flow drop occurs during the constant temperature process, if the temperature t1 is within 5°C of the preset value, the heater power is adjusted according to step 5. If it exceeds 5°C, the control module automatically opens the third solenoid valve to discharge the high-temperature medium. At the same time, the liquid level sensor cooperates to supplement the low-temperature medium to control the temperature and avoid over-temperature accidents.

9. The method for maintaining a constant temperature of a medium before testing the cold-keeping performance of a cryogenic pressure vessel according to claim 1, characterized in that: The gap length is 20 mm, and the temperature sensor is fixed on the left side of each constant temperature cavity.

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