A liquid nitrogen liquid level and temperature control system

Abstract

The application discloses a liquid nitrogen liquid level and temperature control system and relates to the technical field of low-temperature acquisition; and specifically comprises the following: a liquid nitrogen pool connected with a liquid nitrogen gravity tank through a first pipeline and used for storing liquid nitrogen; the liquid nitrogen gravity tank is used for outputting liquid nitrogen to the liquid nitrogen pool through the first pipeline; and an opening-adjustable valve is arranged on the top of the liquid nitrogen pool and used for absorbing steam generated by heat absorption and evaporation of the liquid nitrogen pool and for adjusting the opening of the valve to control the steam amount of the steam according to a set temperature range. The liquid nitrogen filling mode used by the application has a lower working temperature compared with the mode of pumping liquid nitrogen steam into a pipeline by using a vacuum pump. When the temperature of the liquid nitrogen in the liquid nitrogen pool is not within the set temperature range, the opening-adjustable valve is used to control the steam amount in the liquid nitrogen pool, so that the steam pressure is controlled, the low-temperature liquid nitrogen in the liquid nitrogen gravity tank flows into the liquid nitrogen pool, the temperature of the liquid nitrogen in the liquid nitrogen pool is accurately controlled, and the system is driven by gravity, so that energy is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low temperature acquisition, in particular to a liquid nitrogen liquid level and temperature control system. BACKGROUND

[0002] Liquid nitrogen freezing is a commonly used low temperature acquisition technology, which has been widely used in biomedical, material science and earth science research.

[0003] The commonly used liquid nitrogen freezing mainly includes two methods, the first method is liquid nitrogen temperature cooling, the sample is first frozen to the liquid nitrogen temperature (-195.8℃), and then heated according to the requirement, so as to obtain the required temperature; the second method is to use the low temperature steam of liquid nitrogen for cooling, a vacuum pump is used to create negative pressure in the pipeline, so that the low temperature steam of liquid nitrogen enters the pipeline, thereby cooling the load.

[0004] The first method needs to freeze and heat at the same time, which consumes more energy; and the second method uses a vacuum pump to suck in the cold steam, which generally needs several hours to obtain a stable low temperature, if the speed is to be improved, a large flow vacuum pump is needed, however, there is a limit to continuously improve the pumping speed of the vacuum pump to produce larger cold steam flow, when the vacuum degree reaches a certain low, the freezing point of liquid nitrogen will rise sharply, causing the liquid nitrogen in the suction pipeline to freeze and become solid, so as to continue to provide cold steam, therefore, the general cold steam method can only maintain about -70℃, and it is very difficult to obtain lower temperature, and it is very difficult to make the temperature controllable by adjusting the pumping speed of the vacuum pump, in addition, the vacuum pump is always in working state, which consumes more energy. SUMMARY

[0005] The purpose of the present application is to provide a liquid nitrogen liquid level and temperature control system to solve the technical problems of the prior art that cannot obtain lower temperature, temperature is not controllable and consumes more energy.

[0006] To achieve the above purpose, the present application provides the following scheme:

[0007] A liquid nitrogen liquid level and temperature control system, comprising: a liquid nitrogen pool, a liquid nitrogen gravity tank, a heat conducting plate, a liquid nitrogen inlet pipe and an opening adjustable valve.

[0008] The liquid nitrogen pool is connected with the liquid nitrogen gravity tank through a first pipeline and is used for storing liquid nitrogen.

[0009] The liquid nitrogen gravity tank is used for outputting liquid nitrogen to the liquid nitrogen pool through the first pipeline.

[0010] The heat conducting plate is arranged on the side of the liquid nitrogen pool and is used for transferring heat to the liquid nitrogen pool.

[0011] The liquid nitrogen introduction pipe is arranged at the connection between the liquid nitrogen pool and the first pipe, and is used for introducing the liquid nitrogen in the first pipe into the liquid nitrogen pool.

[0012] The opening adjustable valve is arranged at the top of the liquid nitrogen pool, and is used for absorbing the steam generated by the heat absorption evaporation of the liquid nitrogen pool, and adjusting the steam amount of the steam according to the set temperature range.

[0013] Optionally, the system further comprises a manual liquid nitrogen valve.

[0014] The manual liquid nitrogen valve is arranged at the connection between the first pipe and the liquid nitrogen gravity tank, and is used for controlling the cut-off and opening of the first pipe.

[0015] Optionally, the system further comprises a liquid nitrogen storage tank.

[0016] The liquid nitrogen storage tank is connected with the liquid nitrogen gravity tank through a liquid nitrogen conveying pipe, and is used for providing liquid nitrogen to the liquid nitrogen gravity tank.

[0017] Optionally, the system further comprises a liquid level measurement and controller and a normally open electromagnetic valve.

[0018] The liquid level measurement and controller is connected with the liquid nitrogen gravity tank and the normally open electromagnetic valve respectively, and is used for detecting the liquid level of the liquid nitrogen in the liquid nitrogen gravity tank, and controlling the opening and closing of the normally open electromagnetic valve.

[0019] The normally open electromagnetic valve is connected with the liquid nitrogen storage tank, and is used for controlling the air pressure of the liquid nitrogen storage tank.

[0020] Optionally, the system further comprises a liquid nitrogen pump.

[0021] The liquid nitrogen pump is arranged at the top of the liquid nitrogen storage tank, and is used for pumping the liquid nitrogen in the liquid nitrogen storage tank.

[0022] Optionally, the system further comprises a nitrogen tank.

[0023] The nitrogen tank is connected with the liquid nitrogen storage tank through a second pipe, and is used for providing nitrogen to the liquid nitrogen storage tank.

[0024] Optionally, the system further comprises a pressure regulator.

[0025] The pressure regulator is arranged at the connection between the second pipe and the nitrogen tank, and is used for adjusting the pressure in the nitrogen tank.

[0026] Optionally, the system further comprises a normally closed electromagnetic valve.

[0027] The normally closed electromagnetic valve is arranged on the second pipe.

[0028] The liquid level measurement and controller is further connected with the normally closed electromagnetic valve, and is used for controlling opening and closing of the normally closed electromagnetic valve.

[0029] According to the specific embodiments of the present application, the following technical effects are disclosed: the present application provides a liquid nitrogen liquid level and temperature control system, which obtains lower temperature and controllable low-temperature environment through gravity self-driven liquid nitrogen filling mode; when the liquid nitrogen in the liquid nitrogen pool works at the set temperature, the steam in the liquid nitrogen pool will become more and more with heat absorption, and the opening adjustable valve adjusts the pressure generated by the steam in the liquid nitrogen pool, so that the liquid nitrogen gravity left in the liquid nitrogen gravity tank is balanced with the pressure generated by the steam, at this time, the liquid nitrogen pool is in a liquid level maintaining state, if the steam amount generated by heat absorption is greater than the steam amount discharged through the opening adjustable valve, the internal pressure of the liquid nitrogen pool will be increased, so that the flow from the liquid nitrogen gravity tank to the liquid nitrogen pool becomes smaller, and the temperature in the liquid nitrogen pool becomes higher due to the steam, at this time, the opening of the opening adjustable valve is adjusted to increase, so that the pressure generated by the steam in the liquid nitrogen pool is reduced; compared with the mode of using a vacuum pump to pump the liquid nitrogen steam into a pipeline, the liquid nitrogen filling mode used in the present application has lower working temperature, and secondly, when the temperature of the liquid nitrogen in the liquid nitrogen pool is not in the set temperature range, the steam amount in the liquid nitrogen pool is controlled through the opening adjustable valve, so that the steam pressure is controlled, so that the low-temperature liquid nitrogen in the liquid nitrogen gravity tank flows into the liquid nitrogen pool, the temperature of the liquid nitrogen in the liquid nitrogen pool is accurately controlled, and since the system is driven by gravity, energy is saved. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0031] Figure 1 The present application provides a flow chart of a liquid nitrogen liquid level and temperature control system.

[0032] Symbol explanation:

[0033] Liquid nitrogen gravity tank - 1, liquid level measurement and controller - 2, liquid nitrogen storage tank - 3, nitrogen tank - 4, pressure regulator - 5, normally closed electromagnetic valve - 6, normally open electromagnetic valve - 7, liquid nitrogen pump - 8, liquid nitrogen delivery pipe - 9, liquid nitrogen pool - 10, opening adjustable valve - 11, manual liquid nitrogen valve - 12, heat conduction plate - 101, liquid nitrogen inlet pipe - 102. DETAILED DESCRIPTION

[0034] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0035] The present application aims to provide a liquid nitrogen level and temperature control system, so as to obtain lower liquid nitrogen temperature, controllable temperature environment and energy saving.

[0036] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0037] As shown in the flow chart of the liquid nitrogen level and temperature control system provided by the present application. Figure 1

[0038] A liquid nitrogen level and temperature control system, comprising: a liquid nitrogen pool 10, a liquid nitrogen gravity tank 1, a heat-conducting plate 101, a liquid nitrogen introduction pipe 102 and an opening-adjustable valve 11.

[0039] The liquid nitrogen pool 10 is connected with the liquid nitrogen gravity tank 1 through a first pipeline, and is used for storing liquid nitrogen.

[0040] The liquid nitrogen gravity tank 1 is used for outputting liquid nitrogen to the liquid nitrogen pool 10 through the first pipeline.

[0041] The heat-conducting plate 101 is arranged on the side of the liquid nitrogen pool 10, and is used for transferring heat to the liquid nitrogen pool 10.

[0042] The liquid nitrogen introduction pipe 102 is arranged at the connection between the liquid nitrogen pool 10 and the first pipeline, and is used for introducing liquid nitrogen in the first pipeline into the liquid nitrogen pool 10.

[0043] The opening-adjustable valve 11 is arranged on the top of the liquid nitrogen pool 10, and is used for absorbing steam generated by heat absorption and evaporation of the liquid nitrogen pool 10, and also used for adjusting the opening of the valve to control the steam amount of the steam according to the set temperature range.

[0044] In actual application, it further comprises a manual liquid nitrogen valve 12.

[0045] The manual liquid nitrogen valve 12 is arranged at the connection between the first pipeline and the liquid nitrogen gravity tank 1, and is used for controlling the cutoff and opening of the first pipeline.

[0046] In actual application, it further comprises a liquid nitrogen storage tank 3.

[0047] ​The liquid nitrogen storage tank 3 is connected with the liquid nitrogen gravity tank 1 through the liquid nitrogen conveying pipe 9, and is used for providing liquid nitrogen to the liquid nitrogen gravity tank 1.

[0048] In actual application, the liquid level measurement and controller 2 and the normally open electromagnetic valve 7 are further included.

[0049] The liquid level measurement and controller 2 is connected with the liquid nitrogen gravity tank 1 and the normally open electromagnetic valve 7 respectively, and is used for detecting the liquid level of the liquid nitrogen in the liquid nitrogen gravity tank 1 and controlling the opening and closing of the normally open electromagnetic valve 7.

[0050] The normally open electromagnetic valve 7 is connected with the liquid nitrogen storage tank 3, and is used for controlling the air pressure of the liquid nitrogen storage tank 3.

[0051] In actual application, the liquid nitrogen pump 8 is further included.

[0052] The liquid nitrogen pump 8 is arranged on the top of the liquid nitrogen storage tank 3, and is used for pumping out the liquid nitrogen in the liquid nitrogen storage tank 3.

[0053] In actual application, the nitrogen tank 4 is further included.

[0054] The nitrogen tank 4 is connected with the liquid nitrogen storage tank 3 through the second pipeline, and is used for providing nitrogen to the liquid nitrogen storage tank 3.

[0055] In actual application, the pressure regulator 5 is further included.

[0056] The pressure regulator 5 is arranged at the connection position of the second pipeline and the nitrogen tank 4, and is used for regulating the pressure in the nitrogen tank 4.

[0057] In actual application, the normally closed electromagnetic valve 6 is further included.

[0058] The normally closed electromagnetic valve 6 is arranged on the second pipeline.

[0059] The liquid level measurement and controller 2 is further connected with the normally closed electromagnetic valve 6, and is used for controlling the opening and closing of the normally closed electromagnetic valve 6.

[0060] When the liquid nitrogen in the liquid nitrogen pool 10 works at the set temperature, the liquid nitrogen injection is not needed, and the opening degree adjustable valve 11 is adjusted to control the steam amount, so as to control the size of the steam pressure, so that the size of the steam pressure and the gravity of the liquid nitrogen in the liquid nitrogen gravity tank 1 are equal and offset each other, at this time, there is no liquid nitrogen output in the liquid nitrogen gravity tank 1, and the temperature of the liquid nitrogen in the liquid nitrogen pool 10 is stabilized in the required set temperature range.

[0061] When the temperature is higher than the set temperature, the liquid level measurement and controller 2 controls the opening adjustable valve 11 to increase the opening, the pressure in the first pipe decreases, and more liquid nitrogen can flow into the first pipe, increasing the refrigeration efficiency and reducing the temperature.

[0062] When the temperature is lower than the set temperature, the liquid level measurement and controller 2 controls the opening adjustable valve 11 to decrease the opening, the pressure in the first pipe increases, and the flow rate of liquid nitrogen decreases, thereby reducing the refrigeration and increasing the temperature. This indicates that the system is over-cooled at this time.

[0063] The opening adjustable valve 11 is controlled by a PID (Proportion Integral Differential) controller or other similar algorithm controller.

[0064] When the liquid nitrogen in the liquid nitrogen pool works at the set temperature, the steam in the liquid nitrogen pool will increase with heat absorption. The opening adjustable valve adjusts the pressure generated by the steam in the liquid nitrogen pool, so that the liquid nitrogen gravity left from the liquid nitrogen gravity tank balances with the pressure generated by the steam. At this time, the liquid nitrogen pool is in a liquid level maintaining state. If the amount of steam generated by heat absorption is greater than the amount of steam discharged through the opening adjustable valve, the internal pressure of the liquid nitrogen pool will rise, thereby reducing the flow rate of the liquid nitrogen gravity tank to the liquid nitrogen pool, and the temperature in the liquid nitrogen pool will rise due to the steam. At this time, the opening adjustable valve is adjusted to increase the opening, so that the pressure generated by the steam in the liquid nitrogen pool is reduced.

[0065] Let the difference between the liquid level of the liquid nitrogen gravity tank 1 and the liquid level of the liquid nitrogen pool 10 be h, and the pressure of the liquid nitrogen in the liquid nitrogen pool 10 be P1 = 810 kg / m 3 × 10 m / s 2 × h. If the opening of the opening adjustable valve 11 is adjusted at this time, the pressure of the gas in the liquid nitrogen pool 10 is also P1, and the temperature is stable.

[0066] In actual operation, the pressure in the liquid nitrogen pool 10 does not need to be measured, but only the opening of the opening adjustable valve 11 is directly controlled by measuring the temperature.

[0067] The liquid nitrogen gravity tank 1 is higher than the liquid nitrogen pool 10 in the horizontal position, and the specific height control is controlled by the computer, which adjusts the height according to different systems, internal pipe lengths and pipe diameters. The standard for adjustment is that when the system reaches the lowest temperature, no liquid nitrogen is discharged from the outlet.

[0068] When the temperature of the liquid nitrogen in the liquid nitrogen pool 10 rises, liquid nitrogen needs to be injected to maintain the set temperature range. At this time, the opening adjustable valve 11 is adjusted to control the amount of steam, thereby reducing the pressure in the first pipe, so that the liquid nitrogen in the liquid nitrogen gravity tank 1 flows into the liquid nitrogen pool 10 through the first pipe, thereby reducing the temperature of the liquid nitrogen in the liquid nitrogen pool 10.

[0069] The supplement device comprises a liquid nitrogen storage tank 3, a nitrogen tank 4, a normally open electromagnetic valve 7, a normally closed electromagnetic valve 6, a pressure regulator 5, a liquid nitrogen pump 8 and a liquid level measurement and controller 2, and the supplement device is used to supplement liquid nitrogen to the liquid nitrogen gravity tank 1, so that the liquid level is relatively stable, thereby improving the precision of temperature control.

[0070] The supplement device uses nitrogen as power, and the liquid nitrogen in the liquid nitrogen storage tank 3 is pressurized into the liquid nitrogen gravity tank 1 through pressurization of the liquid nitrogen storage pipe; the pressure of the liquid nitrogen storage tank 3 is controlled by the normally open electromagnetic valve 7 and the normally closed electromagnetic valve 6.

[0071] When the liquid level measurement and controller 2 detects that the liquid level is too low, the normally open electromagnetic valve 7 is controlled to be closed, because the normally open electromagnetic valve 7 controls the exhaust port of the liquid nitrogen storage tank 3 and has been in an open state, the gas pressure in the liquid nitrogen storage tank 3 is 1 standard atmosphere; the normally closed electromagnetic valve 6 is controlled to be opened by the liquid level measurement and controller 2, the liquid nitrogen storage tank 3 is communicated with the nitrogen tank 4, the gas pressure in the nitrogen tank 4 is adjusted to be less than 1 standard atmosphere through the pressure regulator 5; at this time, the nitrogen in the nitrogen tank 4 enters the liquid nitrogen storage tank 3, when the pressure in the liquid nitrogen storage pipe rises, the liquid nitrogen in the liquid nitrogen storage pipe enters the liquid nitrogen gravity tank 1 through the liquid nitrogen conveying pipe 9.

[0072] When the liquid level meets the set requirement, the normally closed electromagnetic valve 6 is closed by the liquid level measurement and controller 2 to block the nitrogen supply, and the normally open electromagnetic valve 7 is opened to discharge the pressure in the liquid nitrogen storage tank 3, so that the liquid nitrogen in the liquid nitrogen conveying pipe 9 flows back to the liquid nitrogen storage tank 3, and through accurate liquid level control, the precision of temperature control can be improved to the maximum extent.

[0073] The application provides a liquid nitrogen liquid level and temperature control system, which obtains lower temperature and controllable low-temperature environment through gravity self-driven liquid nitrogen filling mode.

[0074] Compared with the prior art using a vacuum pump to pump liquid nitrogen vapor into a pipeline, the application has lower working temperature, and when the temperature of liquid nitrogen in the liquid nitrogen pool is not in the set temperature range, the opening degree of the valve is adjusted to control the amount of vapor in the liquid nitrogen pool, so that the size of the vapor pressure is controlled, the low-temperature liquid nitrogen in the liquid nitrogen gravity tank flows into the liquid nitrogen pool, the temperature of the liquid nitrogen in the liquid nitrogen pool is accurately controlled, and energy is saved because the system is driven by gravity.

[0075] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts of each embodiment can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0076] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A liquid nitrogen level and temperature control system, characterized by, It comprises: a liquid nitrogen pool, a liquid nitrogen gravity tank, a heat conduction plate, a liquid nitrogen inlet pipe and an opening adjustable valve; the liquid nitrogen pool is connected with the liquid nitrogen gravity tank through a first pipeline and is used for storing liquid nitrogen; the liquid nitrogen gravity tank is used for outputting liquid nitrogen to the liquid nitrogen pool through the first pipeline; the liquid nitrogen gravity tank is used for obtaining a lower temperature and a controllable low-temperature environment through a gravity self-driven liquid nitrogen filling mode; the heat conduction plate is arranged on the side of the liquid nitrogen pool and is used for transferring heat to the liquid nitrogen pool; the liquid nitrogen inlet pipe is arranged at the connection between the liquid nitrogen pool and the first pipeline and is used for guiding the liquid nitrogen in the first pipeline into the liquid nitrogen pool; the opening adjustable valve is arranged on the top of the liquid nitrogen pool and is used for absorbing steam generated by heat absorption and evaporation of the liquid nitrogen pool and adjusting the opening of the valve to control the steam amount of the steam according to a set temperature range; when the liquid level measurement and controller detects that the temperature is higher than the set temperature, the opening adjustable valve is controlled to increase the opening, the pressure in the first pipeline is reduced, more liquid nitrogen can flow into the first pipeline, the refrigeration efficiency is increased, and the temperature is reduced; when the liquid level measurement and controller detects that the temperature is lower than the set temperature, the opening adjustable valve is controlled to reduce the opening, the pressure in the first pipeline is increased, the flow rate of the liquid nitrogen is reduced, the refrigeration is reduced, and the temperature is increased.

2. The liquid nitrogen level and temperature control system of claim 1, wherein, It further comprises: a manual liquid nitrogen valve; the manual liquid nitrogen valve is arranged at the connection between the first pipeline and the liquid nitrogen gravity tank and is used for controlling the cutoff and opening of the first pipeline.

3. The liquid nitrogen level and temperature control system of claim 1, wherein, It further comprises: a liquid nitrogen storage tank; the liquid nitrogen storage tank is connected with the liquid nitrogen gravity tank through a liquid nitrogen conveying pipe and is used for providing liquid nitrogen to the liquid nitrogen gravity tank.

4. The liquid nitrogen level and temperature control system of claim 1, wherein, It further comprises: a liquid level measurement and controller and a normally open electromagnetic valve; the liquid level measurement and controller is connected with the liquid nitrogen gravity tank and the normally open electromagnetic valve respectively and is used for detecting the liquid level of the liquid nitrogen in the liquid nitrogen gravity tank and controlling the opening and closing of the normally open electromagnetic valve; the normally open electromagnetic valve is connected with the liquid nitrogen storage tank and is used for controlling the air pressure of the liquid nitrogen storage tank.

5. The liquid nitrogen level and temperature control system of claim 4, wherein, It further comprises: a liquid nitrogen pump; the liquid nitrogen pump is arranged on the top of the liquid nitrogen storage tank and is used for pumping out the liquid nitrogen in the liquid nitrogen storage tank.

6. The liquid nitrogen level and temperature control system of claim 5, wherein, It further comprises: a nitrogen tank; the nitrogen tank is connected with the liquid nitrogen storage tank through a second pipeline and is used for providing nitrogen to the liquid nitrogen storage tank.

7. The liquid nitrogen level and temperature control system of claim 6, wherein, It further comprises: a pressure regulator; the pressure regulator is arranged at the connection between the second pipeline and the nitrogen tank and is used for adjusting the pressure in the nitrogen tank.

8. The liquid nitrogen level and temperature control system of claim 7, wherein, It further comprises: a normally closed electromagnetic valve; the normally closed electromagnetic valve is arranged on the second pipeline; the liquid level measurement and controller is further connected with the normally closed electromagnetic valve and is used for controlling the opening and closing of the normally closed electromagnetic valve.

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