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Design of distribution system for cryogenic subcooled research platform
Fusion Engineering and Design 137 (2018) 172–176
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of distribution system for cryogenic subcooled research platform Maofei Geng a b
a,b
a
a,⁎
a
T
a
, Yuntao Song , Qiyong Zhang , Anyi Cheng , Hansheng Feng
Insitute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People’s Republic of China University of Science and Technology of China, Hefei 230026, People’s Republic of China
A R T I C LE I N FO
A B S T R A C T
Keywords: Subcooled helium Cold compressor Distribution system Helium pump
To improve the efficiency of the Experimental Advanced Superconducting Tokamak (EAST) subcooled helium cryogenic system, the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), is manufacturing a cryogenic subcooled research platform (CSRP). The CSRP system consists of a helium refrigerator with a capacity of 1200 W/4.5 K + 720 W/3 K and a distribution system that provides a supercritical forced flow cooling by using a helium circulation pump and 3 K subcooled helium generated using a two-stage cold compressor (CC) for the superconducting magnet and other devices. The distribution system not only distributes refrigeration to the cold components, but also serves as a test platform for some key equipment, such as the helium pump, CC, and venturi flow meter.
1. Introduction With the development of cryogenic technology and the requirement for stronger magnetic fields, increasing numbers of helium cryogenic systems with a cold compressor (CC) are being used to obtain subcooled/superfluid helium [1–5]. The Experimental Advanced Superconducting Tokamak (EAST) at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) is an advanced, steady-state plasma physics experimental device. The cryogenic system of EAST is designed with a capacity of 1050 W/3.5 K + 200 W/4.5 K + 13 g/s liquid helium (LHe) + 13 kW/80 K, which is approximately equivalent to a helium refrigerator with a capacity more than 2 kW at 4 K [6]; the toroidal field (TF) coils of EAST are cooled using supercritical helium to work at 3.5 K. Subcooled helium (3.5 K) is obtained using an oil ring pump (ORP) at ambient temperatures by pumping saturated LHe. However, the helium refrigerator is usually operated in the 4.4 K refrigeration mode, and it is difficult to ensure reliable long-term operation of the subcooled helium cryogenic system [7]. As the preliminary technical storage for the EAST subcooled helium improvement project, ASIPP is manufacturing a CSRP system to distribute refrigeration to cold components and test crucial equipment, including the CC, helium pump, and venturi flow meter. In the present work, the design of the distribution system of CSRP is discussed. The distribution system consists of a distribution box, two compressors, a helium pump, and 14 cryogenic control valves. A schematic flow sheet of the distribution system is shown in Fig. 1. Liquid helium is precooled as it flows through a HX into the
⁎
subcooled LHe vessel. The temperature of the subcooled LHe vessel decreases when the CC pumps saturated helium gas. The gas helium flows through the HX, CC, and the compressor in one cycle. To reach the subcooled temperature of 3 K, two CCs can produce the required pressure ratio (about 4.3). 2. Cryogenic distribution box As shown in Fig. 2, the cryogenic distribution box, a vertical vacuum dewar, consists of 80 K thermal shields cooled by liquid nitrogen, a subcooled liquid helium vessel, and a sub-atmosphere heat exchanger (HX). From the viewpoint of developing the 1.8 K superfluid helium system in future, two standby interfaces for CCs and a standby interface for the helium pump in the distribution box are provided. The cold box consists of an outer box and an inner box. The interfaces of the transfer lines, measuring leads, and other equipment are set atop the outer box, but the interfaces of the transfer lines to the cold components and safety valves are set on the flank of the outer box, and the vacuum interface is set on the inner box. The specifications of the cold box are listed in Table 1. 2.1. Thermal shields The 80 K thermal shields are used to reduce heat radiation from the vacuum vessel to the subcooled helium vessel. The copper thermal shield is divided into three parts, namely, outer thermal shield, rightlower thermal shield, and left-lower thermal shield, which are cooled
Corresponding author. E-mail address: [email protected] (A. Cheng).
https://doi.org/10.1016/j.fusengdes.2018.09.008 Received 12 March 2018; Received in revised form 22 August 2018; Accepted 13 September 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 1. Schematic flow sheet of the distribution system.
Fig. 2. Distribution box.
173
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Table 1 Cold box specifications. Parameters
Values
Cold box Outer box Inner box Weight of distribution box Cold vacuum pressure
φ2020 mm × 3150 mm φ2020 mm × 495 mm φ2020 mm × 2580 mm 5100 kg (not including pipes) ≤10−3 Pa
Table 2 Specifications of coiled-HX. Coiled-tube HX
Number
DN (mm)
Length (m)
HX-B4000-1 HX-B4000-2 HX-B4000-3
10 10 10
φ16 × 1.5 φ16 × 1.5 φ16 × 1.5
13 7 6
Fig. 4. Saturated pressure at different temperature.
by liquid nitrogen. The cooling LN2 copper pipe (Φ16 × 1.5) is welded intermittently on the thermal shield in a zig-zag type shape, and the spacing is 250 mm. The dimensions of the outer thermal shield and the inner thermal shields are Φ1896 mm × 387 mm and Φ1896 mm × 2587 mm, respectively.
refrigerator, a counter-flow aluminum plate-fin HX is used. The operating pressure and the area of hot helium are 135 kPa and 2.6 m2, respectively, and the operating pressure and area of cold helium are 24 kPa and 9.6 m2. The HX must operate at full capacity in the nominal operation mode of the CC, as well as at low capacity in the reduced operation mode. As shown in Fig.1, in the reduced operation mode, a part of the helium gas from the CC2 outlet will flow through the CC bypass and return to helium vessel to increase the mass flow rate to CCs. In the low-pressure stream, the pressure drop must remain lower than 7 kPa; this restrictive specification is imposed by the CCs. In the highpressure stream, the maximum pressure drop in any operation mode must not exceed 10 kPa. The HX parameters are listed in Fig. 3.
2.2. Helium vessel The volume of the helium vessel is about 2000 L. Three coiled-tube HXs are installed in the liquid helium vessel and used for heat transfer of supercritical helium (SHe) and liquid helium. The coiled-HX specification is listed in Table 2. The HX-B4000-1 transfers the heat load of the helium coming from the refrigerator for precooling the devices. The HX-B4000-2 transfers the heat load of the helium pumps to liquid helium. The HX-B4000-3 is installed for removing the heat load of the superconductor and the transfer lines and for providing stable SHe inlet conditions to the pumps.
3. Cold compressor The CCs are crucial equipment in distribution system, and two compressors are used to pump gas helium from the liquid helium vessel. As shown in Fig. 4, the refrigeration temperature of 3 K requires that the pressure of the helium vessel be reduced to 23.73 kPa by using two-
2.3. Sub-atmosphere HX To decrease the cooling loss of the helium originating from the
Fig. 3. HX parameters.
174
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 5. Scheme of CC.
stage compressors to reduce the suction pressure to 16.4 kPa. The scheme of CC is shown in Fig.5, the mass flow rate is 32.8 g/s. The CCs, powered by high speed electro-motor housed ceramic ball bearings, are cooled by a closed water circuit. The bearings are designed to operate 8000 h without maintenance, and bearing vibration are checked using vibration sensors. To reduce axial heat conduction from the motors to the CCs, titanium is selected as the material of the motor shaft, and a thermal anchor cooled by LN2 is employed. We expect the efficiency to reach 65%. The design parameters of the CCs are listed in Table 3.
Fig. 6. SHe pump.
specifications of the helium pump are listed in Table 4, and the preliminary results are shown in Fig. 7.
5. Conclusions
4. SHe pump
A distribution system can provide a supercritical forced flow cooling by using a helium circulation pump and 3 K subcooled helium obtained using two-stage CCs for the superconducting magnet and other devices. On-site tests of the helium pump and CCs will be based on the EAST 2 kW cryogenic system. Presently, the distribution system is being fabricated for the CSRP, and it is expected to be completed in October 2018.
When the cryogenic system requires more SHe to cool the superconducting magnets, the distribution system provides a forced flow of SHe by using the helium pump. The helium pump can increase the SHe mass flow rate to cool the superconducting magnets and doing so has little influence on the mass flow rate from refrigerator. Compared to directly increasing the SHe mass flow rate of the refrigerator, the use of a helium pump is more economical. The helium pump is shown in Fig. 6. It is designed to achieve a helium mass flow rate of 200 g/s and a delta-P of 180 kPa with an efficiency of 50%–53%. Three valves are used for pre-cooling the pump and controlling the delta-P. The
Table 4 Specifications of helium pump.
Table 3 Design parameters of CCs. Parameters
Units
CC 1
CC 2
Helium flow rate Inlet total pressure Inlet total temperature Outlet total pressure Outlet total temperature Total to total compression ratio Isentropic efficiency Rotor speed Wheel diameter
g/s kPa, a K kPa, a K – % rpm mm
32.8 17.985 3.865 69.268 7.446 3.85 ≥65 43000 66
32.8 65.00 7.5 130.00 11.1 2 ≥65 43000 66
175
Parameters
Values
Fluid Volume flow Mass flow Inlet pressure Inlet temperature Discharge pressure Delta-P Head (SHe) Inlet density Rotational speed Heat load
SHe 96.5 L/min 200 g/s 320 kPa 4.8 K 500 kPa 180 kPa 147.67 meters 124.3 kg/m3 9859 rpm 581 W
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 7. Delta-P and efficiency at different pump mass flow.
Acknowledgment [3]
This work is supported by the Special Funds for the Repair and Purchase in Chinese Academy of Sciences (NO. Y65YZ18291).
[4]
References
[5] [6] [7]
[1] S. Claudet, G. Ferlin, P. Gully, et al., A cryogenic test station for the pre-series 2400 W @ 1.8 K refrigeration units for the LHC, Biochim. Biophys. Acta 2 (3) (2002) 181–189 1538. [2] S. Hamaguchi, et al., Operation and control of helium subcooling system of LHD
176
helical coils during change of rotational speed of cold compressors, IEEE Trans. Appl. Supercond. 20 (3) (2010) 2051–2053. C. Dhard, et al., Refrigerator operation during commissioning and first plasma operations of Wendelstein 7-X, Fusion Eng. Des. 123 (2017) 111–114. D. Henry, The TORE SUPRA cryogenic system behaviour during long plasma discharges with a high injected energy, AIP Conference Proceedings 823 (2006) 1412–1419. A. Cheng, et al., Process design of cryogenic distribution system for CFETR CS model coil, Plasma Sci. Technol. 18 (2) (2016) 202–205. H. Bai, et al., Cryogenics in EAST, Fusion Eng. Des. 81 (23) (2006) 2597–2603. Z. Zhu, et al., Present status and one upgrading method with a cold compressor of the EAST sub-cooling helium cryogenic system, Plasma Sci. Technol. 19 (5) (2017) 102–108.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of distribution system for cryogenic subcooled research platform Maofei Geng a b
a,b
a
a,⁎
a
T
a
, Yuntao Song , Qiyong Zhang , Anyi Cheng , Hansheng Feng
Insitute of Plasma Physics, Chinese Academy of Science, Hefei 230031, People’s Republic of China University of Science and Technology of China, Hefei 230026, People’s Republic of China
A R T I C LE I N FO
A B S T R A C T
Keywords: Subcooled helium Cold compressor Distribution system Helium pump
To improve the efficiency of the Experimental Advanced Superconducting Tokamak (EAST) subcooled helium cryogenic system, the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), is manufacturing a cryogenic subcooled research platform (CSRP). The CSRP system consists of a helium refrigerator with a capacity of 1200 W/4.5 K + 720 W/3 K and a distribution system that provides a supercritical forced flow cooling by using a helium circulation pump and 3 K subcooled helium generated using a two-stage cold compressor (CC) for the superconducting magnet and other devices. The distribution system not only distributes refrigeration to the cold components, but also serves as a test platform for some key equipment, such as the helium pump, CC, and venturi flow meter.
1. Introduction With the development of cryogenic technology and the requirement for stronger magnetic fields, increasing numbers of helium cryogenic systems with a cold compressor (CC) are being used to obtain subcooled/superfluid helium [1–5]. The Experimental Advanced Superconducting Tokamak (EAST) at Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) is an advanced, steady-state plasma physics experimental device. The cryogenic system of EAST is designed with a capacity of 1050 W/3.5 K + 200 W/4.5 K + 13 g/s liquid helium (LHe) + 13 kW/80 K, which is approximately equivalent to a helium refrigerator with a capacity more than 2 kW at 4 K [6]; the toroidal field (TF) coils of EAST are cooled using supercritical helium to work at 3.5 K. Subcooled helium (3.5 K) is obtained using an oil ring pump (ORP) at ambient temperatures by pumping saturated LHe. However, the helium refrigerator is usually operated in the 4.4 K refrigeration mode, and it is difficult to ensure reliable long-term operation of the subcooled helium cryogenic system [7]. As the preliminary technical storage for the EAST subcooled helium improvement project, ASIPP is manufacturing a CSRP system to distribute refrigeration to cold components and test crucial equipment, including the CC, helium pump, and venturi flow meter. In the present work, the design of the distribution system of CSRP is discussed. The distribution system consists of a distribution box, two compressors, a helium pump, and 14 cryogenic control valves. A schematic flow sheet of the distribution system is shown in Fig. 1. Liquid helium is precooled as it flows through a HX into the
⁎
subcooled LHe vessel. The temperature of the subcooled LHe vessel decreases when the CC pumps saturated helium gas. The gas helium flows through the HX, CC, and the compressor in one cycle. To reach the subcooled temperature of 3 K, two CCs can produce the required pressure ratio (about 4.3). 2. Cryogenic distribution box As shown in Fig. 2, the cryogenic distribution box, a vertical vacuum dewar, consists of 80 K thermal shields cooled by liquid nitrogen, a subcooled liquid helium vessel, and a sub-atmosphere heat exchanger (HX). From the viewpoint of developing the 1.8 K superfluid helium system in future, two standby interfaces for CCs and a standby interface for the helium pump in the distribution box are provided. The cold box consists of an outer box and an inner box. The interfaces of the transfer lines, measuring leads, and other equipment are set atop the outer box, but the interfaces of the transfer lines to the cold components and safety valves are set on the flank of the outer box, and the vacuum interface is set on the inner box. The specifications of the cold box are listed in Table 1. 2.1. Thermal shields The 80 K thermal shields are used to reduce heat radiation from the vacuum vessel to the subcooled helium vessel. The copper thermal shield is divided into three parts, namely, outer thermal shield, rightlower thermal shield, and left-lower thermal shield, which are cooled
Corresponding author. E-mail address: [email protected] (A. Cheng).
https://doi.org/10.1016/j.fusengdes.2018.09.008 Received 12 March 2018; Received in revised form 22 August 2018; Accepted 13 September 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 1. Schematic flow sheet of the distribution system.
Fig. 2. Distribution box.
173
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Table 1 Cold box specifications. Parameters
Values
Cold box Outer box Inner box Weight of distribution box Cold vacuum pressure
φ2020 mm × 3150 mm φ2020 mm × 495 mm φ2020 mm × 2580 mm 5100 kg (not including pipes) ≤10−3 Pa
Table 2 Specifications of coiled-HX. Coiled-tube HX
Number
DN (mm)
Length (m)
HX-B4000-1 HX-B4000-2 HX-B4000-3
10 10 10
φ16 × 1.5 φ16 × 1.5 φ16 × 1.5
13 7 6
Fig. 4. Saturated pressure at different temperature.
by liquid nitrogen. The cooling LN2 copper pipe (Φ16 × 1.5) is welded intermittently on the thermal shield in a zig-zag type shape, and the spacing is 250 mm. The dimensions of the outer thermal shield and the inner thermal shields are Φ1896 mm × 387 mm and Φ1896 mm × 2587 mm, respectively.
refrigerator, a counter-flow aluminum plate-fin HX is used. The operating pressure and the area of hot helium are 135 kPa and 2.6 m2, respectively, and the operating pressure and area of cold helium are 24 kPa and 9.6 m2. The HX must operate at full capacity in the nominal operation mode of the CC, as well as at low capacity in the reduced operation mode. As shown in Fig.1, in the reduced operation mode, a part of the helium gas from the CC2 outlet will flow through the CC bypass and return to helium vessel to increase the mass flow rate to CCs. In the low-pressure stream, the pressure drop must remain lower than 7 kPa; this restrictive specification is imposed by the CCs. In the highpressure stream, the maximum pressure drop in any operation mode must not exceed 10 kPa. The HX parameters are listed in Fig. 3.
2.2. Helium vessel The volume of the helium vessel is about 2000 L. Three coiled-tube HXs are installed in the liquid helium vessel and used for heat transfer of supercritical helium (SHe) and liquid helium. The coiled-HX specification is listed in Table 2. The HX-B4000-1 transfers the heat load of the helium coming from the refrigerator for precooling the devices. The HX-B4000-2 transfers the heat load of the helium pumps to liquid helium. The HX-B4000-3 is installed for removing the heat load of the superconductor and the transfer lines and for providing stable SHe inlet conditions to the pumps.
3. Cold compressor The CCs are crucial equipment in distribution system, and two compressors are used to pump gas helium from the liquid helium vessel. As shown in Fig. 4, the refrigeration temperature of 3 K requires that the pressure of the helium vessel be reduced to 23.73 kPa by using two-
2.3. Sub-atmosphere HX To decrease the cooling loss of the helium originating from the
Fig. 3. HX parameters.
174
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 5. Scheme of CC.
stage compressors to reduce the suction pressure to 16.4 kPa. The scheme of CC is shown in Fig.5, the mass flow rate is 32.8 g/s. The CCs, powered by high speed electro-motor housed ceramic ball bearings, are cooled by a closed water circuit. The bearings are designed to operate 8000 h without maintenance, and bearing vibration are checked using vibration sensors. To reduce axial heat conduction from the motors to the CCs, titanium is selected as the material of the motor shaft, and a thermal anchor cooled by LN2 is employed. We expect the efficiency to reach 65%. The design parameters of the CCs are listed in Table 3.
Fig. 6. SHe pump.
specifications of the helium pump are listed in Table 4, and the preliminary results are shown in Fig. 7.
5. Conclusions
4. SHe pump
A distribution system can provide a supercritical forced flow cooling by using a helium circulation pump and 3 K subcooled helium obtained using two-stage CCs for the superconducting magnet and other devices. On-site tests of the helium pump and CCs will be based on the EAST 2 kW cryogenic system. Presently, the distribution system is being fabricated for the CSRP, and it is expected to be completed in October 2018.
When the cryogenic system requires more SHe to cool the superconducting magnets, the distribution system provides a forced flow of SHe by using the helium pump. The helium pump can increase the SHe mass flow rate to cool the superconducting magnets and doing so has little influence on the mass flow rate from refrigerator. Compared to directly increasing the SHe mass flow rate of the refrigerator, the use of a helium pump is more economical. The helium pump is shown in Fig. 6. It is designed to achieve a helium mass flow rate of 200 g/s and a delta-P of 180 kPa with an efficiency of 50%–53%. Three valves are used for pre-cooling the pump and controlling the delta-P. The
Table 4 Specifications of helium pump.
Table 3 Design parameters of CCs. Parameters
Units
CC 1
CC 2
Helium flow rate Inlet total pressure Inlet total temperature Outlet total pressure Outlet total temperature Total to total compression ratio Isentropic efficiency Rotor speed Wheel diameter
g/s kPa, a K kPa, a K – % rpm mm
32.8 17.985 3.865 69.268 7.446 3.85 ≥65 43000 66
32.8 65.00 7.5 130.00 11.1 2 ≥65 43000 66
175
Parameters
Values
Fluid Volume flow Mass flow Inlet pressure Inlet temperature Discharge pressure Delta-P Head (SHe) Inlet density Rotational speed Heat load
SHe 96.5 L/min 200 g/s 320 kPa 4.8 K 500 kPa 180 kPa 147.67 meters 124.3 kg/m3 9859 rpm 581 W
Fusion Engineering and Design 137 (2018) 172–176
M. Geng et al.
Fig. 7. Delta-P and efficiency at different pump mass flow.
Acknowledgment [3]
This work is supported by the Special Funds for the Repair and Purchase in Chinese Academy of Sciences (NO. Y65YZ18291).
[4]
References
[5] [6] [7]
[1] S. Claudet, G. Ferlin, P. Gully, et al., A cryogenic test station for the pre-series 2400 W @ 1.8 K refrigeration units for the LHC, Biochim. Biophys. Acta 2 (3) (2002) 181–189 1538. [2] S. Hamaguchi, et al., Operation and control of helium subcooling system of LHD
176
helical coils during change of rotational speed of cold compressors, IEEE Trans. Appl. Supercond. 20 (3) (2010) 2051–2053. C. Dhard, et al., Refrigerator operation during commissioning and first plasma operations of Wendelstein 7-X, Fusion Eng. Des. 123 (2017) 111–114. D. Henry, The TORE SUPRA cryogenic system behaviour during long plasma discharges with a high injected energy, AIP Conference Proceedings 823 (2006) 1412–1419. A. Cheng, et al., Process design of cryogenic distribution system for CFETR CS model coil, Plasma Sci. Technol. 18 (2) (2016) 202–205. H. Bai, et al., Cryogenics in EAST, Fusion Eng. Des. 81 (23) (2006) 2597–2603. Z. Zhu, et al., Present status and one upgrading method with a cold compressor of the EAST sub-cooling helium cryogenic system, Plasma Sci. Technol. 19 (5) (2017) 102–108.