Helium cooler for liquid helium temperature zone

Abstract

The utility model discloses a helium cooler for a liquid helium temperature zone. The helium cooler comprises a vacuum cavity and a vacuum flange cover fixed above the vacuum cavity in a sealed mode. A cold shield, a liquid helium cavity, a liquid nitrogen cavity and a liquid helium cavity suspender are arranged in the vacuum cavity; the liquid helium cavity and the liquid nitrogen cavity are both arranged in the cold shield, and the liquid nitrogen cavity is located above the liquid helium cavity. The upper end of the liquid helium cavity suspender is fixed with the vacuum flange cover, the lower end of the liquid helium cavity suspender is fixed with the liquid helium cavity, and the middle section of the liquid helium cavity suspender is fixed with the inner side of the cold shield; a heat exchange coil pipe and a liquid level meter are installed in the liquid helium cavity, a cold shield coil pipe is installed on the outer side of the cold shield, and the cold shield coil pipe is connected with the liquid nitrogen cavity; the vacuum flange cover is provided with a heat exchange coil inlet pipe and a heat exchange coil outlet pipe, and the heat coil inlet pipe and the heat exchange coil outlet pipe are connected with the two ends of the heat exchange coil respectively. According to the utility model, the helium working medium in other states is cooled to a liquid helium temperature area by using liquid helium, so that the low heat leakage is ensured, and the structural strength is good.

Description

Technical Field

[0001] The utility model belongs to the field of heat exchangers, in particular to a helium cooler used in a liquid helium temperature zone. Background Art

[0002] In deep cryogenic experiments, it is often necessary to use liquid helium temperature range working fluid to cool the experimental samples. In some cases, liquid helium cannot be used directly to cool the experimental samples or direct use of liquid helium cooling cannot achieve the expected heat exchange effect. At this time, it is necessary to cool the helium working fluid in other states to the liquid helium temperature range before cooling the experimental samples.

[0003] Since the temperature of liquid helium is extremely low and the latent heat of vaporization is small, how to reduce the heat leakage of containers used in the liquid helium temperature range is a very important consideration.

[0004] For example, a Chinese patent document with publication number CN112797309A discloses a liquid helium dewar, including a vacuum cover, a liquid nitrogen chamber, a liquid nitrogen cold shield, a liquid helium chamber, a vacuum layer, a suspension rod and a radiation shield, wherein the liquid nitrogen cold shield is used to reduce the radiation heat leakage of the liquid helium chamber and slow down the evaporation rate of the liquid helium. However, in order to reduce the heat leakage of the structure, such liquid helium containers often design the suspension rod to be a slender structure, which has poor stability and is prone to damage to the internal structure if it encounters vibration during use. Utility Model Content

[0005] The utility model provides a helium cooler for a liquid helium temperature zone, which utilizes liquid helium to cool helium working fluid in other states to the liquid helium temperature zone, and has good structural strength while ensuring low heat leakage.

[0006] A helium cooler for a liquid helium temperature zone comprises a vacuum cavity and a vacuum flange cover sealed and fixed on the upper portion thereof; a cold shield, a liquid helium cavity, a liquid nitrogen cavity and a liquid helium cavity suspension rod are arranged inside the vacuum cavity;

[0007] The liquid helium chamber and the liquid nitrogen chamber are both arranged inside the cold shield, and the liquid nitrogen chamber is located above the liquid helium chamber; the upper end of the liquid helium chamber suspension rod is fixed to the vacuum flange cover, the lower end of the liquid helium chamber suspension rod is fixed to the liquid helium chamber, and the middle section of the liquid helium chamber suspension rod is fixed to the inner side of the cold shield;

[0008] A heat exchange coil and a liquid level gauge are installed inside the liquid helium chamber, a cold shield coil is installed outside the cold shield, and the cold shield coil is connected to the liquid nitrogen chamber;

[0009] The vacuum flange cover is provided with a heat exchange coil inlet pipe and a heat exchange coil outlet pipe, and the heat exchange coil inlet pipe and the heat exchange coil outlet pipe are respectively connected to the two ends of the heat exchange coil.

[0010] Furthermore, the heat exchange coil is fixed to the bottom of the liquid helium chamber through a coil tray.

[0011] Furthermore, the liquid helium chamber suspension rod is a hollow circular tube, the upper end of the liquid helium chamber suspension rod is fixed to the vacuum flange cover by a hoisting upper pad, the lower end of the liquid helium chamber suspension rod is fixed to the liquid helium chamber by a hoisting lower pad, and the middle section of the liquid helium chamber suspension rod is fixed to the inner side of the cold screen by a cold screen fixing block and a hoisting thermal bridge.

[0012] In terms of reducing the heat leakage of liquid helium, in addition to the conventional use of liquid nitrogen cold shield to reduce radiation heat leakage, the utility model also designs the liquid helium chamber suspension rod as a hollow circular tube. Compared with a solid circular rod, the hollow circular tube has better structural stability under the same heat transfer cross-sectional area. Secondly, the upper and lower ends of the liquid helium chamber suspension rod are connected to the vacuum flange cover and the liquid helium chamber respectively using a hoisting upper pad and a hoisting lower pad made of a low thermal conductivity material, which increases the heat transfer thermal resistance and reduces the heat leakage of the hoisting structure; in addition, a hoisting thermal bridge is used to connect the cold shield with the liquid helium chamber suspension rod, so that the heat leakage of the liquid helium chamber along the hoisting structure is changed from 300K to 4.2K to 77K to 4.2K, which greatly reduces the heat leakage of the liquid helium chamber suspension rod to the liquid helium chamber.

[0013] Furthermore, the vacuum flange cover is provided with a liquid helium filling pipe, a helium reflux pipe, a helium gas return pipe, a liquid nitrogen inlet pipe and a nitrogen outlet pipe;

[0014] The liquid helium filling pipe, the helium reflux pipe and the helium gas return pipe are all connected to the liquid helium cavity; the liquid nitrogen inlet pipe and the nitrogen outlet pipe are all connected to the liquid nitrogen cavity.

[0015] Furthermore, the heat exchange coil inlet pipe, heat exchange coil outlet pipe, liquid helium filling pipe, helium reflux pipe, helium gas return pipe, liquid nitrogen inlet pipe and nitrogen gas outlet pipe are all vacuum insulation pipes.

[0016] Furthermore, valves are provided on the heat exchange coil inlet pipe, the liquid helium filling pipe, the helium reflux pipe, the helium gas return pipe and the liquid nitrogen inlet pipe.

[0017] Furthermore, the vacuum flange cover is provided with a vacuum extraction port.

[0018] Furthermore, a safety valve and a pressure sensor are provided on the vacuum flange cover; the safety valve and the pressure sensor pass through the vacuum flange cover through a pipeline and are connected to the liquid helium chamber.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] 1. The utility model utilizes the liquid helium in the liquid helium cavity to cool the helium working medium in the heat exchange coil to the liquid helium temperature. After the helium working medium flows out of the cooler, it is throttled and its temperature is further reduced. It is then used to cool the experimental sample. After that, it flows back to the liquid helium cavity from the helium return pipe to participate in cooling the helium working medium in the heat exchange coil. The heat leakage of the liquid helium cavity improves the utilization rate of the cooling capacity.

[0021] 2. The utility model utilizes a liquid helium chamber suspension rod to connect the vacuum flange cover, the liquid helium chamber connection, and the cold screen, thereby ensuring low heat leakage while having good structural strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the front view of the utility model.

[0023] Figure 2 For the utility model structure along Figure 1 Cross-sectional view along the AA direction.

[0024] Figure 3 It is a top view of the structure of the utility model.

[0025] In the figure: 1-vacuum chamber, 2-vacuum flange cover, 3-cold shield, 4-liquid helium chamber, 5-liquid nitrogen chamber, 6-liquid helium chamber suspension rod, 7-heat exchange coil, 8-coil tray, 9-lifting upper pad, 10-lifting lower pad, 11-cold shield coil, 12-cold shield fixing block, 13-lifting thermal bridge, 14-valve, 15-heat exchange coil inlet pipe, 16-heat exchange coil outlet pipe, 17-liquid helium filling pipe, 18-helium reflux pipe, 19-helium return pipe, 20-liquid nitrogen inlet pipe, 21-nitrogen outlet pipe, 22-vacuum extraction port, 23-liquid level gauge, 24-safety valve, 25-pressure sensor. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0027] like Figure 1 to Figure 3 As shown, a helium cooler for liquid helium temperature zone includes a vacuum chamber 1, a vacuum flange cover 2, a cold shield 3, a liquid helium chamber 4, a liquid nitrogen chamber 5 and a liquid helium chamber suspension rod 6. The vacuum chamber 1 and the vacuum flange cover 2 together form an internal vacuum space, which plays a role in heat insulation for the low-temperature components such as the cold shield 3, the liquid helium chamber 4 and the liquid nitrogen chamber 5 therein.

[0028] The vacuum flange cover 2 is provided with a heat exchange coil inlet pipe 15 , a heat exchange coil outlet pipe 16 , a liquid helium filling pipe 17 , a helium reflux pipe 18 , a helium gas return pipe 19 , a liquid nitrogen inlet pipe 20 and a nitrogen gas outlet pipe 21 . The heat exchange coil inlet pipe 15 and the heat exchange coil outlet pipe 16 are both connected to the heat exchange coil 7 in the liquid helium chamber 4, and are responsible for the filling and discharge of the helium working medium in the heat exchange coil 7; the liquid helium filling pipe 17, the helium reflux pipe 18 and the helium gas return pipe 19 are all connected to the liquid helium chamber 4, wherein the liquid helium filling pipe 17 is used for pre-filling and replenishing the liquid helium in the liquid helium chamber 4, the helium reflux pipe 18 is used for the helium working medium discharged from the heat exchange coil 7 to flow back to the liquid helium chamber, and the helium gas return pipe 19 is used for discharging the helium gasified by heat in the liquid helium chamber 4; the liquid nitrogen inlet pipe 20 and the nitrogen gas outlet pipe 21 are both connected to the liquid nitrogen chamber 5, wherein the liquid nitrogen inlet pipe 20 is used for filling the liquid nitrogen in the liquid nitrogen chamber 5, and the nitrogen gas outlet pipe 21 is used for discharging the nitrogen gasified by heat in the liquid nitrogen chamber 5.

[0029] The heat exchange coil inlet pipe 15, the heat exchange coil outlet pipe 16, the liquid helium filling pipe 17, the helium reflux pipe 18, the helium return pipe 19, the liquid nitrogen inlet pipe 20 and the nitrogen outlet pipe 21 are all vacuum insulation pipes to reduce heat leakage from the external environment to the cryogenic working medium in the pipe.

[0030] The heat exchange coil inlet pipe 15, the liquid helium filling pipe 17, the helium reflux pipe 18, the helium gas return pipe 19 and the liquid nitrogen inlet pipe 20 are all provided with valves 14 for controlling the filling and discharge of the cryogenic working medium.

[0031] The liquid helium chamber 4 is provided with a heat exchange coil 7, a coil tray 8 and a liquid level gauge 23. The coil tray 8 is welded and fixed to the bottom of the liquid helium chamber 4. The heat exchange coil 7 is tied to the coil tray 8 by copper wire and is restricted in displacement by a round tube in the vertical direction on the coil tray 8. The liquid level gauge 23 is used to monitor the liquid level of the liquid helium in the liquid helium chamber 4 and control the opening and closing of the valve 14 on the liquid helium filling pipe 17 according to the measured liquid level data. When the liquid helium level is low, the valve 14 on the liquid helium filling pipe 17 is opened to replenish the liquid helium chamber 4 with liquid helium. On the contrary, the valve 14 on the liquid helium filling pipe 17 is closed to stop replenishing the liquid helium chamber 4 with liquid helium.

[0032] The upper part of the liquid helium chamber hanger rod 6 is connected to the upper hoisting pad 9, and the lower part of the liquid helium chamber hanger rod 6 is connected to the lower hoisting pad 10. The upper side of the upper hoisting pad 9 is connected to the vacuum flange cover 2, and the lower side of the lower hoisting pad 10 is connected to the liquid helium chamber 4. The liquid helium chamber hanger rod 6 is a stainless steel hollow circular tube. Compared with a solid round rod, the hollow circular tube has better structural stability under the same heat transfer cross-sectional area. The upper hoisting pad 9 and the lower hoisting pad 10 are made of G10 material. The thermal conductivity of G10 is small, which can effectively reduce the heat leakage along the liquid helium chamber hanger rod 6.

[0033] A cold shield fixing block 12 and a hoisting thermal bridge 13 are installed in the middle section of the liquid helium chamber hanger 6, wherein the cold shield fixing block 12 is welded and fixed on the liquid helium chamber hanger 6, and the cold shield 3 is fixed on the cold shield fixing block 12 by bolts, thereby ensuring the structural stability of the cold shield; the hoisting thermal bridge 13 is an oxygen-free copper block, and its two ends are respectively connected to the cold shield 3 and the liquid helium chamber hanger 6, so that the cold energy of the cold shield 3 is introduced into the liquid helium chamber hanger 6, so that the heat leakage of the liquid helium chamber along the hoisting structure is converted from 300K to 4.2K to 77K to 4.2K, thereby greatly reducing the heat leakage on this path.

[0034] A cold shield coil 11 is installed outside the cold shield 3 , and the cold shield coil 11 is connected to the liquid nitrogen chamber 5 . The liquid nitrogen in the liquid nitrogen chamber 5 is used to cool the cold shield 3 to reduce the radiation heat leakage to the liquid helium chamber 5 .

[0035] A vacuum port 22, a safety valve 24 and a pressure sensor 25 are provided on the vacuum flange cover 2. The vacuum port 22 is used to connect a vacuum pump group to form a vacuum environment inside the vacuum chamber 1. The safety valve 24 and the pressure sensor 25 pass through the vacuum flange cover 2 through a pipeline and are connected to the liquid helium chamber 4. The pressure sensor 25 is used to monitor the pressure inside the liquid helium chamber 4 and control the opening and closing of the valve 14 on the helium return pipe 19 according to the measured data. When the pressure inside the liquid helium chamber 4 is too high, the valve 14 on the helium return pipe 19 is opened to discharge the helium in the liquid helium chamber 4 in time. If the helium is not discharged in time and the pressure in the liquid helium chamber 4 rises to a certain value, the safety valve 24 will be opened for rapid exhaust to avoid danger caused by excessive pressure in the liquid helium chamber 4.

[0036] The workflow of this utility model:

[0037] Open the vacuum port 22 and connect the vacuum pump to draw the vacuum degree inside the vacuum chamber 1 to 1×10 -2 Pa or less, and continue to evacuate for more than 2 hours, and close the vacuum port 22. Use nitrogen to replace the gas in the liquid nitrogen chamber 5, and use helium to replace the gas in the liquid helium chamber 4 and the heat exchange coil 7. After the replacement is completed, fill the liquid nitrogen chamber 5 and the cold screen coil 11 with liquid nitrogen from the liquid nitrogen inlet pipe 20. At this time, the cold screen 3 begins to cool down. After the temperature of the cold screen 3 stabilizes, fill the liquid helium chamber 4 with liquid helium from the liquid helium filling pipe 17, observe the reading of the liquid level gauge 23, until the liquid helium completely immerses the heat exchange coil 7, and stop filling the liquid helium chamber 4 with liquid helium. Start to fill the heat exchange coil 7 with helium medium from the heat exchange coil inlet pipe 15, so that the helium medium in the heat exchange coil 7 is cooled by the liquid helium in the liquid helium chamber 4, and then it is discharged from the heat exchange coil outlet pipe 16 for cooling the experimental sample. During use, pay attention to the reading of the liquid level gauge 23. When the liquid level of liquid helium in the liquid helium chamber 4 is too low, liquid helium needs to be replenished in time.

[0038] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A helium cooler for liquid helium temperature zone, characterized in that: It comprises a vacuum chamber (1) and a vacuum flange cover (2) sealed and fixed on the top thereof; a cold shield (3), a liquid helium chamber (4), a liquid nitrogen chamber (5) and a liquid helium chamber suspension rod (6) are arranged inside the vacuum chamber (1); The liquid helium chamber (4) and the liquid nitrogen chamber (5) are both arranged inside the cold shield (3), and the liquid nitrogen chamber (5) is located above the liquid helium chamber (4); the upper end of the liquid helium chamber suspension rod (6) is fixed to the vacuum flange cover (2), the lower end of the liquid helium chamber suspension rod (6) is fixed to the liquid helium chamber (4), and the middle section of the liquid helium chamber suspension rod (6) is fixed to the inner side of the cold shield (3); A heat exchange coil (7) and a liquid level gauge (23) are installed inside the liquid helium chamber (4), a cold shield coil (11) is installed outside the cold shield (3), and the cold shield coil (11) is connected to the liquid nitrogen chamber (5); The vacuum flange cover (2) is provided with a heat exchange coil inlet pipe (15) and a heat exchange coil outlet pipe (16), and the heat exchange coil inlet pipe (15) and the heat exchange coil outlet pipe (16) are respectively connected to the two ends of the heat exchange coil (7).

2. The helium cooler for liquid helium temperature zone according to claim 1, characterized in that: The heat exchange coil (7) is fixed to the bottom of the liquid helium chamber (4) via a coil tray (8).

3. The helium cooler for liquid helium temperature zone according to claim 1, characterized in that: The liquid helium chamber suspension rod (6) is a hollow circular tube. The upper end of the liquid helium chamber suspension rod (6) is fixed to the vacuum flange cover (2) through a hoisting upper pad (9), the lower end of the liquid helium chamber suspension rod (6) is fixed to the liquid helium chamber (4) through a hoisting lower pad (10), and the middle section of the liquid helium chamber suspension rod (6) is fixed to the inner side of the cold shield (3) through a cold shield fixing block (12) and a hoisting thermal bridge (13).

4. The helium cooler for liquid helium temperature zone according to claim 1, characterized in that: The vacuum flange cover (2) is provided with a liquid helium filling pipe (17), a helium reflux pipe (18), a helium gas return pipe (19), a liquid nitrogen inlet pipe (20) and a nitrogen outlet pipe (21); The liquid helium filling pipe (17), the helium reflux pipe (18) and the helium gas return pipe (19) are all connected to the liquid helium chamber (4); the liquid nitrogen inlet pipe (20) and the nitrogen gas outlet pipe (21) are all connected to the liquid nitrogen chamber (5).

5. The helium cooler for liquid helium temperature zone according to claim 1, characterized in that: The heat exchange coil inlet pipe (15), the heat exchange coil outlet pipe (16), the liquid helium filling pipe (17), the helium reflux pipe (18), the helium gas return pipe (19), the liquid nitrogen inlet pipe (20) and the nitrogen gas outlet pipe (21) are all vacuum insulation pipes.

6. The helium cooler for liquid helium temperature region according to claim 1, characterized in that: Valves are provided on the heat exchange coil inlet pipe (15), the liquid helium filling pipe (17), the helium reflux pipe (18), the helium gas return pipe (19) and the liquid nitrogen inlet pipe (20).

7. The helium cooler for liquid helium temperature region according to claim 1, characterized in that: The vacuum flange cover (2) is provided with a vacuum extraction port (22).

8. The helium cooler for liquid helium temperature region according to claim 1, characterized in that: The vacuum flange cover (2) is provided with a safety valve (24) and a pressure sensor (25); the safety valve (24) and the pressure sensor (25) pass through the vacuum flange cover (2) through a pipeline and are connected to the liquid helium chamber (4).

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