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The cooling test platform design for iter radial x-ray camera
Fusion Engineering and Design 128 (2018) 163–167
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
The cooling test platform design for iter radial x-ray camera a,b
Bin Zhang , Sheng Zhang Jinlong Zhaoa a b
a,b
a,⁎
a
a
a
T a
, Yebin Chen , Liqun Hu , Shi Li , Keping Wu , Zhigang Zhu ,
Institute of Plasma Physics Chinese Academy of Sciences, Hefei, 230031, China University of Science and Technology of China, Hefei, 230026, China
A R T I C L E I N F O
A B S T R A C T
Keywords: Radial X-ray camera Cooling test platform EPICS
The Radial X-ray Camera (RXC) is a diagnostic in Equatorial Port 12 (EQ#12) of International Thermonuclear Experimental: Reactor (ITER). Normally, the operating temperature of detector on RXC system shall be lower than 75 °C. But the detectors on some part of RXC system will have to face a high temperature of 250 °C during baking of ITER, as a result of which case detectors will be easily damaged. Due to the harsh environment, cooling for RXC system is necessary. In order to verify the effect of gas cooling, the related research and experiments are being carried out. This article focuses on the analysis of the architecture and heat transfer capacities of the cooling test platform. According to the analysis results, the solution of the cooling platform is introduced and a cooling test platform is established. Also, a Data Acquisition (DAQ) system is developed based on Experimental Physics and Industrial Control System (EPICS) framework. The experiment results based on the cooling test platform provide support for the cooling system design of RXC system.
1. Introduction
built based on this scheme. The standard ITER Instrument and Control (I&C) architecture is deployed for data acquisition and control system of the cooling test platform. The test results show that the detectors’ temperature can be limited to under 75 °C. It also provides support and reference for the cooling system design of RXC system.
A radial x-ray camera (RXC) will be installed in the ITER EPP #12(middle drawer, DSM02) to measure the poloidal profile of the plasma x-ray emission [1]. RXC consists of internal and external camera modules. The detector on the RXC is a normal linear silicon semiconductor photodiode (Series 5T of Centronic Ltd., Craydon. United Kingdom), whose operating temperature shall be lower than 75 °C [2]. The main vacuum vessel where the internal camera will be installed would reach 250 °C during baking of ITER. Even in the normal operation phase, the environment temperature will be higher than 75 °C in which case the detectors could not survive. Normally, for each 10 °C increase on the detector, the dark current will be doubled [3]. Excessive temperature will not only damage the detectors of the internal camera, but also affect the performance of the detectors. Therefore, cooling system should be adopted to keep the detectors at room temperature. Gas cooling is one of the cooling methods. Helium is recommended by ITER as cooling medium in the cooling system for its good conduction of heat. In this paper, a cooling test platform is developed so as to meet the cooling requirement for the internal camera detectors of RXC. Thermal load of the internal camera detectors is estimated. Also, the solution of equipment selection and test plan of the cooling test platform is presented. In order to verify the actual effect, a cooling test platform is ⁎
2. Cooling test platform requirements analysis During the baking of ITER, the ambient temperature of internal camera is about 250 °C. As the upper limit temperature of detector is 75 °C, for a safety margin, it is assumed that the temperature of detector should be reduced to 50 °C. Generally, there are three different ways affecting the heat of the detectors, the first one is the heat radiation from vacuum space, the second one is the heat conduction from stents that is used to fix the heat exchanger on the detector housing, and the last one is the heat convection. As the detectors of internal camera will be installed in the second vacuum vessel of ITER, the heat convection is negligible. It should be noted that in order to protect the detector and limit the light path of X-Ray from the plasma, a detector housing which is molded with 316L stainless steel is used to hold the detector. The temperature of detectors will rise when detector housing absorbs the heat from vacuum space. Therefore, the surface of the detector housing is polished to improve heat reflection from vacuum space. To further
Corresponding author. E-mail address: [email protected] (Y. Chen).
https://doi.org/10.1016/j.fusengdes.2018.01.057 Received 21 January 2017; Received in revised form 28 September 2017; Accepted 23 January 2018 Available online 10 February 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 128 (2018) 163–167
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Fig. 1. Heat exchanger and ceramic.
reduce heat absorption, Multi-layer insulation (MLI) with high reflectivity and low emissivity is applied to reflect thermal radiation from vacuum space [4–7]. The heat exchanger fixed tightly with the ceramic detector module is used to exchange the heat from detector by cooling medium. Meanwhile, the heat exchanger is fixed on the detector housing by four long and thin stents.
Fig. 2. Stents structure.
2.2. Thermal conduction power calculation Heat conduction is one of the important factors which lead to temperature rising. As shown in Fig. 2, heat is transferred from detector housing to heat exchanger through four stents between them. The thermal conduction power of three heat exchangers can be calculated using the following formulas:
2.1. Thermal radiation power calculation A testing camera is mounted inside the baking cell. Inside the testing camera there are 3 detector modules made with ceramic (see in Fig. 1) which is the same material as the package material of the detector. To obtain better effect of thermal reflection, more MLI are added to the outer surface and inner surface of detector housing. The heat of ceramic detector modules comes from the radiation of MLI and it is exchanged by helium in cooling copper pipe. In this design, QHE represents the meaning of the thermal radiation power of a single heat exchanger. In order to calculate the maximum thermal power of the heat exchanger, it is assumed that the heat of the detectors is all transferred to the heat exchangers. Theoretically, the heat radiation power of heat exchanger can be quantified in terms of its heat transfer coefficient U11, temperature gradient ΔT1 and area of ceramic(0.074 m × 0.015 m × 0.014 m) ACE, so the total heat radiation power in three heat exchangers can be calculated as:
3 × QHE = 3U1A CEΔT1 = 3 × 4σT1 3
1 A CEΔT1 ≈ 1.08W ( 1 ϵCE + 1 ϵM - 1)
3×4×
Q1 = 3 × QHE + QCT + 3 × 4 ×
1 ( 1 ϵCT + 1 ϵM - 1)
(4)
3. Cooling test platform design In order to meet the cooling requirements of RXC, a cooling test platform composed of cooling test circuit and its data acquisition system is developed. Devices in the cooling test platform need to be selected carefully according to the pressure of helium and the temperature of cooling water provided by ITER. The combination of gas cooling and water cooling is adopted in the design. Furthermore, a Data Acquisition (DAQ) system is designed based on Experimental Physics and Industrial Control System (EPICS) framework, which implemented functions for real-time data acquisition, temperature control, supervision and archiving [8].
layers, ACE = 0.00375 m2 is the area of ceramic, ΔT1 = (250 − 50)K = 200K is the temperature gradient, εCE = 0.69 is the emissivity of ceramic, εM = 0.028 is the emissivity of MLI under vacuum condition, T1 = 523.15 K+ 323.15K 2 = 423.15K is the mean temperatures of MLI and ceramic, σ = 5.7 × 10−8 Wm−2 K−4 is the Stefan-Boltzmann Constant. The thermal radiation power of the copper pipe can be calculated as:
Where U2 = 4σT2 3
ΔQ = 36.39W Δt
(1)
( εCE + εM - 1)
1 A CT ΔT2 ≈ 14.21W ( 1 ϵCT + 1 ϵM - 1)
(3)
where k is the material’s thermal conductivity, A is the cross-sectional surface area, ΔTis the temperature difference between the ends, Δx is the distance between the ends, In conclusion, the total thermal power of three heat exchangers and copper pipe can be calculated as:
Where QHE is the radiation power of a single heat exchanger, 1 U1= 4σT3 1 is the heat transfer coefficient between two 1
QCT = U2 A CT ΔT2 = 4σT2 3
ΔQ ΔT = 3 × 4 × kA ≈ 21.10W Δt Δx
3.1. Platform architecture (2) Cooling test platform is designed for RXC cooling test which requires helium and water as cooling medium. Considering constraints of helium in ITER, the closed-loop platform is adopted. Cooling test platform is mainly composed of one compressor which plays the role of pressed gas source, one water-cooled unit which provides cooling water and two water-cooled heat exchangers in which helium is cooled by water (as shown in Fig. 3). The heat generated in the experiment is carried away by helium which is recycled in closed loop. In addition, helium can be controlled by an electric valve from a tank for supplying when the pressure in cooling loop is lower than the set point. Helium can be recycled into the tank after experiment. For achieving control of the main circuit flow, an electric bypass valve is used. Meanwhile, heating equipment is used for temperature simulation.
is the heat transfer coefficient between two
layers, ACT = 2πrl = 2π × 0.008 × 3 ≈ 0.151 m2 is the area of cooling copper pipe, ΔT2 = (250 − 50)K = 200K is the temperature gradient between the MLI and cooling copper pipe, εCT = 0.5 is the emissivity of cooling copper pipe, εM = 0.028 is the emissivity of MLI under vacuum condition, T2 = 523.15 K+ 323.15K 2 = 423.15K is the mean temperatures of MLI and cooling copper pipe, σ = 5.7 × 10−8 Wm−2 K−4 is the Stefan-Boltzmann Constant. 164
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Fig. 3. Cooling test platform.
3.2. Device selection
FHE =
Generally speaking, helium pressure is up to 0.5 MPa and cooling water is 6 °C–12 °C in the real scenario of ITER. It is assumed that the inlet pressure of copper pipe is 0.5 MPa, the pressure loss in the copper pipe is 0.01 MPa according to the structure design, and thus the outlet pressure of copper pipe is 0.49 MPa. According to the system design, the inlet temperature is 12 °C, assuming the outlet temperature is 30 °C. So, the helium flow rate q1 can be derived from:
q1 =
Q1 ≈ 7.85m3/h ρ*(H1Out − H1In)
Where Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, ρ = 0.1786 g/L is the density of helium at 0 °C, 1 atm, H1Out = 1581.07 KJ/Kg is the outlet enthalpy of the test section in 0.49 MPa, 30 °C, H1In = 1487.63 KJ/Kg is the outlet enthalpy of the test section in 0.5 MPa, 12 °C. Enthalpy can be calculated according to National Institute of Standards and Technology (NIST) Isothermal Properties for Helium [9]. A compressor with up to 0.5 MPa exhaust pressure and 30 m3/h (bigger than q1) volume flow is selected not only for simulating actual status, but also considering the flow resistance and pressure loss of external pipeline (Table 2). Heat exchanger is selected according to the heat exchange area which can be derived from:
Q
QRC =
Quantity
Temperature Acquisition (Inside the baking cell) Temperature Acquisition (Cooling pipe Inlet/outlet) Vacuum Acquisition Flow Acquisition Pressure Acquisition (Cooling pipe Inlet/outlet) Baking temperature Control Loop flow Control
Thermocouple
20
Temperature sensor
2
Vacuum gauge Flow meter Pressure sensor
2 1 2
Heating equipment Valve
4 1
1 SH*De* 1.163*60*DT *DT SH*De*F*DT = ≈ 0.037KW 60 60
(7)
Where QRC is the cooling consumption of cooling water, SH = 4.2Kg/KJ℃ is the specific heat of water, De = 1 kg/L is the specific gravity of water, Q1 F= 1.163 * 60 ≈ 0.043L/min is the chilled water flow, * DT DT = 12°C is the temperature gradient of cooling water between inlet and outlet, Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, So, a water-cooled unit with 1.6 KW refrigerating capacity, 4.6 L/ min chilled water flow is selected, and the 7 °C–12 °C cooling is provided by the water-cooled unit. A gas tank is selected in the design to maintain stability of compressor exhaust pressure and store helium.
Table 1 DAQ parameters. Device
(6)
Where FHE is the heat exchange area of heat exchanger, Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, K= 280W/m2°C is the heat transfer coefficient of water and gas, Th1 = 30°C and Th2 = 12°C is the inlet and outlet temperature of hot fluid (helium), Tc1 = 12 °C and Tc2 = 24°C is the inlet and outlet temperature of cold fluid (water), For improving cooling effect, two heat exchangers each with 0.03 m2 heat exchange area are selected. Water-cooled unit is selected according to its refrigerating capacity which can be derived from:
(5)
Description
Q1 Q1 = ≈ 0.043m2 ((Th − Tc 2) + (Th2 − Tc1)) K*ΔT K* 1 2
3.3. Data acquisition and control system Cooling testing system is running with a data acquisition (DAQ) system which implemented functions for real-time data acquisition, control, supervision and archiving. Experiment parameters such as the temperature of detectors, the temperature and the pressure of cooling inlet/outlet, the vacuum of baking cell, the flow of cooling inlet and the opening of valve are collected. Meanwhile, heating temperature and opening of valve can be controlled according to experiment requirement. The list of the parameters is shown in Table 1. Since the outcome 165
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easy to monitor and control the state of cooling testing system on a dedicated Human-Machine Interface (HMI).
Table 2 Experiment results. Experimental conditions
data
inlet flow of the test section (m3/s) inlet temperature of the test section (K) inlet pressure of the test section (MPa) outlet temperature of the test section (K) outlet pressure of the test section (Mpa) inlet enthalpy of the test section (KJ/Kg) outlet enthalpy of the test section (KJ/Kg) baking cell temperature of bottom (K) baking cell temperature of up, left and right (K)
0.003 288.15 0.3 307.65 0.29 1505.7 1603.8 483.15 523.15
3.4. Cooling test plan In order to simulate the actual environment of ITER, vacuum of tank should be pumped to under 10−2 pa firstly, and then with the start of gas cooling system, the baking cell is heated by electrical heating system. With a steady heating, the cell temperature shall be locked at 250 °C. Related experiment parameters will be recorded by DAQ system. The test lasts for 24 h. If the final detector temperature is higher than 75 °C, the cooling test platform should be redesigned [11].
of the cooling test will be the supply of the RXC cooling system, the ITER Instrument and Control (I&C) strategy is selected. The Plant Control Design Handbook (PCDH) provides design rules and guidelines with the design based on CODAC Core System (CCS). It allows building server applications that interact with the hardware and provides an interface to EPICS clients [10]. The DAQ system is designed based on the principle of ITER I&C, it consists of an Industrial Personal Computer (IPC) which plays the role of PSH, a D-Link Switch, a Siemens S7 PLC with analog input/output modules interfacing to sensors and actuator via signal interfaces. As illustrated in Fig. 4. In attempting to control the detectors’ temperature, a proportional valve and a Siemens analog output module are used to adjust the magnitude of gas flow rate. By proper design of relevant EPICS records, the DAQ system can also provide two control modes of manual and automatic, wherein the two modes are freely switched. For example, the opening of the proportional valve depends on its input value on HMI in manual mode. When switching to automatic mode, the opening of the proportional valve will be adjusted automatically according to the error between the setpoint temperature input on HMI and the readback temperature (the temperature of the detector). Also, some linear devices are used by the design of EPICS records. Moreover, it is
4. Results and discussion The detectors’ temperature reaches a steady state after 24 h. From the experimental data obtained by DAQ system and the inlet enthalpy (HIn) and outlet enthalpy (HOut) of the test section can be calculated according to National Institute of Standards and Technology (NIST) Isothermal Properties for Helium(Table 2). So the heat Q2 dissipated by the cooling testing system can be calculated as:
Q2 = M*(HOut − HIn) = q*ρ*(HOut − HIn) ≈ 52.562W
(8)
Where M is the mass flux of the test section, q is the inlet flow of the test section, ρ is the density of helium at 0 °C, 1 atm. Compare with the total thermal power of three heat exchangers Q1 estimated above which is 36.39 W, Q2 > Q1. Structural contact of heating part and thermal conduction part can cause this result. In Fig. 5, the steady temperature of detector 1 (red color) and detector 2 (blue color) is about 50 °C which is consistent with the expected results, but the temperature of detector 3 is about 60 °C since detector 3 is at the end of the cooling circuit. Thus, it is necessary to improve the
Fig. 4. DAQ architecture.
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testing system is capable of stable operation for a long time. A good agreement was observed between predicted and measured detector temperature profiles. The experiment proves the design is reasonable and feasible and the results will be employed to the final design of ITER RXC cooling system. Acknowledgments This work is supported by JSPS-NRF-NSFCA3 Foresight Program in the field of Plasma Physics under Contract No. 11261140328. We would like to thank all IO and DA team members for the help to the design of the ITER RXC diagnostics system. Fig. 5. Temperature plot of detectors.
References structure design to keep three detectors in the same working temperature.
[1] R. Barnsley, Annex B_55 E7_Radial X Ray Camera_V 1.0, ITER Document Management System., 97RVCA, (2013). [2] Centronic Series 5T, (2016) http://www.centronic.co.uk/products/1/generalpurpose (Accessed June, 2016). [3] Y. CHEN, Research of ITER X-Ray Camera, PhD Thesis (Sept. 2013), University of Science and Technology of China, school of physical sciences, 2013. [4] Multi-Layer Insulation, (2018) https://en.wikipedia.org/wiki/Multi-layer_ insulation (Accessed October, 2016). [5] L. Hu, K. Chen, Y. Chen, et al., Outline design of ITER radial X-Ray camera diagnostic, Fusion Sci. Technol. 70 (2016), http://dx.doi.org/10.13182/FST15-137. [6] L. HU, et al., Progress on the ITER diagnostic-radial X-ray camera, Proc. 25th IAEA Fusion Energy Conf, Saint Petersburg, Russian Federation, 13-18, October 2014, FIP/P 4-2, International Atomic Energy Agency, 2014. [7] S. Qin, L. Hu, K. Chen, et al., RAMI analysis for ITER radial X-ray camera system, Fusion Eng. Des. 112 (2016) 169–176, http://dx.doi.org/10.1016/j.fusengdes. 2016.08.019. [8] Experimental Physics and Industrial Control System Home Page, (2016) http:// www.aps.anl.gov/epics/. [9] National Institute of Standards and Technology, (2017) http://webbook.nist.gov/ chemistry/fluid/. [10] Ramesh Joshi, et al., EPICS based monitoring and control in data acquisition system, Int. J. Comput. Sci. Eng. 3 (02) (2014) 95. [11] Y. Chen, et al., Cooling Test Plan 55. E7-RXC, ITER Document Management System. SFD9GK, (2015).
5. Conclusions In the present study, a cooling test platform was developed in order to meet the cooling requirement of ITER RXC. Devices in the cooling test platform such as a compressor with up to 0.5 MPa exhaust pressure and 30 m3/h volume flow, two heat exchangers each with 0.03 m2 heat exchange area, a water-cooled unit with 1.6 KW refrigerating capacity, 4.6 L/min chilled water flow and 7 °C–12 °C cooling water were selected based on the thermal analysis and the cooling medium provided by ITER. Experiment in a cooling testing system for ITER RXC was carried out in order to investigate the effect of the cooling testing system and input helium flow on the performance of cooling. The experimental results showed that with 0.003 m3/s inlet helium flow, detectors’ temperature can be controlled under 75 °C while baking temperature is 250 °C in the cooling testing system. However, applying more effective cooling structure will increase the cooling performance. In addition, it was found that with the assistance of the DAQ system, the cooling
167
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
The cooling test platform design for iter radial x-ray camera a,b
Bin Zhang , Sheng Zhang Jinlong Zhaoa a b
a,b
a,⁎
a
a
a
T a
, Yebin Chen , Liqun Hu , Shi Li , Keping Wu , Zhigang Zhu ,
Institute of Plasma Physics Chinese Academy of Sciences, Hefei, 230031, China University of Science and Technology of China, Hefei, 230026, China
A R T I C L E I N F O
A B S T R A C T
Keywords: Radial X-ray camera Cooling test platform EPICS
The Radial X-ray Camera (RXC) is a diagnostic in Equatorial Port 12 (EQ#12) of International Thermonuclear Experimental: Reactor (ITER). Normally, the operating temperature of detector on RXC system shall be lower than 75 °C. But the detectors on some part of RXC system will have to face a high temperature of 250 °C during baking of ITER, as a result of which case detectors will be easily damaged. Due to the harsh environment, cooling for RXC system is necessary. In order to verify the effect of gas cooling, the related research and experiments are being carried out. This article focuses on the analysis of the architecture and heat transfer capacities of the cooling test platform. According to the analysis results, the solution of the cooling platform is introduced and a cooling test platform is established. Also, a Data Acquisition (DAQ) system is developed based on Experimental Physics and Industrial Control System (EPICS) framework. The experiment results based on the cooling test platform provide support for the cooling system design of RXC system.
1. Introduction
built based on this scheme. The standard ITER Instrument and Control (I&C) architecture is deployed for data acquisition and control system of the cooling test platform. The test results show that the detectors’ temperature can be limited to under 75 °C. It also provides support and reference for the cooling system design of RXC system.
A radial x-ray camera (RXC) will be installed in the ITER EPP #12(middle drawer, DSM02) to measure the poloidal profile of the plasma x-ray emission [1]. RXC consists of internal and external camera modules. The detector on the RXC is a normal linear silicon semiconductor photodiode (Series 5T of Centronic Ltd., Craydon. United Kingdom), whose operating temperature shall be lower than 75 °C [2]. The main vacuum vessel where the internal camera will be installed would reach 250 °C during baking of ITER. Even in the normal operation phase, the environment temperature will be higher than 75 °C in which case the detectors could not survive. Normally, for each 10 °C increase on the detector, the dark current will be doubled [3]. Excessive temperature will not only damage the detectors of the internal camera, but also affect the performance of the detectors. Therefore, cooling system should be adopted to keep the detectors at room temperature. Gas cooling is one of the cooling methods. Helium is recommended by ITER as cooling medium in the cooling system for its good conduction of heat. In this paper, a cooling test platform is developed so as to meet the cooling requirement for the internal camera detectors of RXC. Thermal load of the internal camera detectors is estimated. Also, the solution of equipment selection and test plan of the cooling test platform is presented. In order to verify the actual effect, a cooling test platform is ⁎
2. Cooling test platform requirements analysis During the baking of ITER, the ambient temperature of internal camera is about 250 °C. As the upper limit temperature of detector is 75 °C, for a safety margin, it is assumed that the temperature of detector should be reduced to 50 °C. Generally, there are three different ways affecting the heat of the detectors, the first one is the heat radiation from vacuum space, the second one is the heat conduction from stents that is used to fix the heat exchanger on the detector housing, and the last one is the heat convection. As the detectors of internal camera will be installed in the second vacuum vessel of ITER, the heat convection is negligible. It should be noted that in order to protect the detector and limit the light path of X-Ray from the plasma, a detector housing which is molded with 316L stainless steel is used to hold the detector. The temperature of detectors will rise when detector housing absorbs the heat from vacuum space. Therefore, the surface of the detector housing is polished to improve heat reflection from vacuum space. To further
Corresponding author. E-mail address: [email protected] (Y. Chen).
https://doi.org/10.1016/j.fusengdes.2018.01.057 Received 21 January 2017; Received in revised form 28 September 2017; Accepted 23 January 2018 Available online 10 February 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
Fusion Engineering and Design 128 (2018) 163–167
B. Zhang et al.
Fig. 1. Heat exchanger and ceramic.
reduce heat absorption, Multi-layer insulation (MLI) with high reflectivity and low emissivity is applied to reflect thermal radiation from vacuum space [4–7]. The heat exchanger fixed tightly with the ceramic detector module is used to exchange the heat from detector by cooling medium. Meanwhile, the heat exchanger is fixed on the detector housing by four long and thin stents.
Fig. 2. Stents structure.
2.2. Thermal conduction power calculation Heat conduction is one of the important factors which lead to temperature rising. As shown in Fig. 2, heat is transferred from detector housing to heat exchanger through four stents between them. The thermal conduction power of three heat exchangers can be calculated using the following formulas:
2.1. Thermal radiation power calculation A testing camera is mounted inside the baking cell. Inside the testing camera there are 3 detector modules made with ceramic (see in Fig. 1) which is the same material as the package material of the detector. To obtain better effect of thermal reflection, more MLI are added to the outer surface and inner surface of detector housing. The heat of ceramic detector modules comes from the radiation of MLI and it is exchanged by helium in cooling copper pipe. In this design, QHE represents the meaning of the thermal radiation power of a single heat exchanger. In order to calculate the maximum thermal power of the heat exchanger, it is assumed that the heat of the detectors is all transferred to the heat exchangers. Theoretically, the heat radiation power of heat exchanger can be quantified in terms of its heat transfer coefficient U11, temperature gradient ΔT1 and area of ceramic(0.074 m × 0.015 m × 0.014 m) ACE, so the total heat radiation power in three heat exchangers can be calculated as:
3 × QHE = 3U1A CEΔT1 = 3 × 4σT1 3
1 A CEΔT1 ≈ 1.08W ( 1 ϵCE + 1 ϵM - 1)
3×4×
Q1 = 3 × QHE + QCT + 3 × 4 ×
1 ( 1 ϵCT + 1 ϵM - 1)
(4)
3. Cooling test platform design In order to meet the cooling requirements of RXC, a cooling test platform composed of cooling test circuit and its data acquisition system is developed. Devices in the cooling test platform need to be selected carefully according to the pressure of helium and the temperature of cooling water provided by ITER. The combination of gas cooling and water cooling is adopted in the design. Furthermore, a Data Acquisition (DAQ) system is designed based on Experimental Physics and Industrial Control System (EPICS) framework, which implemented functions for real-time data acquisition, temperature control, supervision and archiving [8].
layers, ACE = 0.00375 m2 is the area of ceramic, ΔT1 = (250 − 50)K = 200K is the temperature gradient, εCE = 0.69 is the emissivity of ceramic, εM = 0.028 is the emissivity of MLI under vacuum condition, T1 = 523.15 K+ 323.15K 2 = 423.15K is the mean temperatures of MLI and ceramic, σ = 5.7 × 10−8 Wm−2 K−4 is the Stefan-Boltzmann Constant. The thermal radiation power of the copper pipe can be calculated as:
Where U2 = 4σT2 3
ΔQ = 36.39W Δt
(1)
( εCE + εM - 1)
1 A CT ΔT2 ≈ 14.21W ( 1 ϵCT + 1 ϵM - 1)
(3)
where k is the material’s thermal conductivity, A is the cross-sectional surface area, ΔTis the temperature difference between the ends, Δx is the distance between the ends, In conclusion, the total thermal power of three heat exchangers and copper pipe can be calculated as:
Where QHE is the radiation power of a single heat exchanger, 1 U1= 4σT3 1 is the heat transfer coefficient between two 1
QCT = U2 A CT ΔT2 = 4σT2 3
ΔQ ΔT = 3 × 4 × kA ≈ 21.10W Δt Δx
3.1. Platform architecture (2) Cooling test platform is designed for RXC cooling test which requires helium and water as cooling medium. Considering constraints of helium in ITER, the closed-loop platform is adopted. Cooling test platform is mainly composed of one compressor which plays the role of pressed gas source, one water-cooled unit which provides cooling water and two water-cooled heat exchangers in which helium is cooled by water (as shown in Fig. 3). The heat generated in the experiment is carried away by helium which is recycled in closed loop. In addition, helium can be controlled by an electric valve from a tank for supplying when the pressure in cooling loop is lower than the set point. Helium can be recycled into the tank after experiment. For achieving control of the main circuit flow, an electric bypass valve is used. Meanwhile, heating equipment is used for temperature simulation.
is the heat transfer coefficient between two
layers, ACT = 2πrl = 2π × 0.008 × 3 ≈ 0.151 m2 is the area of cooling copper pipe, ΔT2 = (250 − 50)K = 200K is the temperature gradient between the MLI and cooling copper pipe, εCT = 0.5 is the emissivity of cooling copper pipe, εM = 0.028 is the emissivity of MLI under vacuum condition, T2 = 523.15 K+ 323.15K 2 = 423.15K is the mean temperatures of MLI and cooling copper pipe, σ = 5.7 × 10−8 Wm−2 K−4 is the Stefan-Boltzmann Constant. 164
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Fig. 3. Cooling test platform.
3.2. Device selection
FHE =
Generally speaking, helium pressure is up to 0.5 MPa and cooling water is 6 °C–12 °C in the real scenario of ITER. It is assumed that the inlet pressure of copper pipe is 0.5 MPa, the pressure loss in the copper pipe is 0.01 MPa according to the structure design, and thus the outlet pressure of copper pipe is 0.49 MPa. According to the system design, the inlet temperature is 12 °C, assuming the outlet temperature is 30 °C. So, the helium flow rate q1 can be derived from:
q1 =
Q1 ≈ 7.85m3/h ρ*(H1Out − H1In)
Where Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, ρ = 0.1786 g/L is the density of helium at 0 °C, 1 atm, H1Out = 1581.07 KJ/Kg is the outlet enthalpy of the test section in 0.49 MPa, 30 °C, H1In = 1487.63 KJ/Kg is the outlet enthalpy of the test section in 0.5 MPa, 12 °C. Enthalpy can be calculated according to National Institute of Standards and Technology (NIST) Isothermal Properties for Helium [9]. A compressor with up to 0.5 MPa exhaust pressure and 30 m3/h (bigger than q1) volume flow is selected not only for simulating actual status, but also considering the flow resistance and pressure loss of external pipeline (Table 2). Heat exchanger is selected according to the heat exchange area which can be derived from:
Q
QRC =
Quantity
Temperature Acquisition (Inside the baking cell) Temperature Acquisition (Cooling pipe Inlet/outlet) Vacuum Acquisition Flow Acquisition Pressure Acquisition (Cooling pipe Inlet/outlet) Baking temperature Control Loop flow Control
Thermocouple
20
Temperature sensor
2
Vacuum gauge Flow meter Pressure sensor
2 1 2
Heating equipment Valve
4 1
1 SH*De* 1.163*60*DT *DT SH*De*F*DT = ≈ 0.037KW 60 60
(7)
Where QRC is the cooling consumption of cooling water, SH = 4.2Kg/KJ℃ is the specific heat of water, De = 1 kg/L is the specific gravity of water, Q1 F= 1.163 * 60 ≈ 0.043L/min is the chilled water flow, * DT DT = 12°C is the temperature gradient of cooling water between inlet and outlet, Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, So, a water-cooled unit with 1.6 KW refrigerating capacity, 4.6 L/ min chilled water flow is selected, and the 7 °C–12 °C cooling is provided by the water-cooled unit. A gas tank is selected in the design to maintain stability of compressor exhaust pressure and store helium.
Table 1 DAQ parameters. Device
(6)
Where FHE is the heat exchange area of heat exchanger, Q1 = 36.39 W is the total thermal power of three heat exchangers and copper pipe, K= 280W/m2°C is the heat transfer coefficient of water and gas, Th1 = 30°C and Th2 = 12°C is the inlet and outlet temperature of hot fluid (helium), Tc1 = 12 °C and Tc2 = 24°C is the inlet and outlet temperature of cold fluid (water), For improving cooling effect, two heat exchangers each with 0.03 m2 heat exchange area are selected. Water-cooled unit is selected according to its refrigerating capacity which can be derived from:
(5)
Description
Q1 Q1 = ≈ 0.043m2 ((Th − Tc 2) + (Th2 − Tc1)) K*ΔT K* 1 2
3.3. Data acquisition and control system Cooling testing system is running with a data acquisition (DAQ) system which implemented functions for real-time data acquisition, control, supervision and archiving. Experiment parameters such as the temperature of detectors, the temperature and the pressure of cooling inlet/outlet, the vacuum of baking cell, the flow of cooling inlet and the opening of valve are collected. Meanwhile, heating temperature and opening of valve can be controlled according to experiment requirement. The list of the parameters is shown in Table 1. Since the outcome 165
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easy to monitor and control the state of cooling testing system on a dedicated Human-Machine Interface (HMI).
Table 2 Experiment results. Experimental conditions
data
inlet flow of the test section (m3/s) inlet temperature of the test section (K) inlet pressure of the test section (MPa) outlet temperature of the test section (K) outlet pressure of the test section (Mpa) inlet enthalpy of the test section (KJ/Kg) outlet enthalpy of the test section (KJ/Kg) baking cell temperature of bottom (K) baking cell temperature of up, left and right (K)
0.003 288.15 0.3 307.65 0.29 1505.7 1603.8 483.15 523.15
3.4. Cooling test plan In order to simulate the actual environment of ITER, vacuum of tank should be pumped to under 10−2 pa firstly, and then with the start of gas cooling system, the baking cell is heated by electrical heating system. With a steady heating, the cell temperature shall be locked at 250 °C. Related experiment parameters will be recorded by DAQ system. The test lasts for 24 h. If the final detector temperature is higher than 75 °C, the cooling test platform should be redesigned [11].
of the cooling test will be the supply of the RXC cooling system, the ITER Instrument and Control (I&C) strategy is selected. The Plant Control Design Handbook (PCDH) provides design rules and guidelines with the design based on CODAC Core System (CCS). It allows building server applications that interact with the hardware and provides an interface to EPICS clients [10]. The DAQ system is designed based on the principle of ITER I&C, it consists of an Industrial Personal Computer (IPC) which plays the role of PSH, a D-Link Switch, a Siemens S7 PLC with analog input/output modules interfacing to sensors and actuator via signal interfaces. As illustrated in Fig. 4. In attempting to control the detectors’ temperature, a proportional valve and a Siemens analog output module are used to adjust the magnitude of gas flow rate. By proper design of relevant EPICS records, the DAQ system can also provide two control modes of manual and automatic, wherein the two modes are freely switched. For example, the opening of the proportional valve depends on its input value on HMI in manual mode. When switching to automatic mode, the opening of the proportional valve will be adjusted automatically according to the error between the setpoint temperature input on HMI and the readback temperature (the temperature of the detector). Also, some linear devices are used by the design of EPICS records. Moreover, it is
4. Results and discussion The detectors’ temperature reaches a steady state after 24 h. From the experimental data obtained by DAQ system and the inlet enthalpy (HIn) and outlet enthalpy (HOut) of the test section can be calculated according to National Institute of Standards and Technology (NIST) Isothermal Properties for Helium(Table 2). So the heat Q2 dissipated by the cooling testing system can be calculated as:
Q2 = M*(HOut − HIn) = q*ρ*(HOut − HIn) ≈ 52.562W
(8)
Where M is the mass flux of the test section, q is the inlet flow of the test section, ρ is the density of helium at 0 °C, 1 atm. Compare with the total thermal power of three heat exchangers Q1 estimated above which is 36.39 W, Q2 > Q1. Structural contact of heating part and thermal conduction part can cause this result. In Fig. 5, the steady temperature of detector 1 (red color) and detector 2 (blue color) is about 50 °C which is consistent with the expected results, but the temperature of detector 3 is about 60 °C since detector 3 is at the end of the cooling circuit. Thus, it is necessary to improve the
Fig. 4. DAQ architecture.
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testing system is capable of stable operation for a long time. A good agreement was observed between predicted and measured detector temperature profiles. The experiment proves the design is reasonable and feasible and the results will be employed to the final design of ITER RXC cooling system. Acknowledgments This work is supported by JSPS-NRF-NSFCA3 Foresight Program in the field of Plasma Physics under Contract No. 11261140328. We would like to thank all IO and DA team members for the help to the design of the ITER RXC diagnostics system. Fig. 5. Temperature plot of detectors.
References structure design to keep three detectors in the same working temperature.
[1] R. Barnsley, Annex B_55 E7_Radial X Ray Camera_V 1.0, ITER Document Management System., 97RVCA, (2013). [2] Centronic Series 5T, (2016) http://www.centronic.co.uk/products/1/generalpurpose (Accessed June, 2016). [3] Y. CHEN, Research of ITER X-Ray Camera, PhD Thesis (Sept. 2013), University of Science and Technology of China, school of physical sciences, 2013. [4] Multi-Layer Insulation, (2018) https://en.wikipedia.org/wiki/Multi-layer_ insulation (Accessed October, 2016). [5] L. Hu, K. Chen, Y. Chen, et al., Outline design of ITER radial X-Ray camera diagnostic, Fusion Sci. Technol. 70 (2016), http://dx.doi.org/10.13182/FST15-137. [6] L. HU, et al., Progress on the ITER diagnostic-radial X-ray camera, Proc. 25th IAEA Fusion Energy Conf, Saint Petersburg, Russian Federation, 13-18, October 2014, FIP/P 4-2, International Atomic Energy Agency, 2014. [7] S. Qin, L. Hu, K. Chen, et al., RAMI analysis for ITER radial X-ray camera system, Fusion Eng. Des. 112 (2016) 169–176, http://dx.doi.org/10.1016/j.fusengdes. 2016.08.019. [8] Experimental Physics and Industrial Control System Home Page, (2016) http:// www.aps.anl.gov/epics/. [9] National Institute of Standards and Technology, (2017) http://webbook.nist.gov/ chemistry/fluid/. [10] Ramesh Joshi, et al., EPICS based monitoring and control in data acquisition system, Int. J. Comput. Sci. Eng. 3 (02) (2014) 95. [11] Y. Chen, et al., Cooling Test Plan 55. E7-RXC, ITER Document Management System. SFD9GK, (2015).
5. Conclusions In the present study, a cooling test platform was developed in order to meet the cooling requirement of ITER RXC. Devices in the cooling test platform such as a compressor with up to 0.5 MPa exhaust pressure and 30 m3/h volume flow, two heat exchangers each with 0.03 m2 heat exchange area, a water-cooled unit with 1.6 KW refrigerating capacity, 4.6 L/min chilled water flow and 7 °C–12 °C cooling water were selected based on the thermal analysis and the cooling medium provided by ITER. Experiment in a cooling testing system for ITER RXC was carried out in order to investigate the effect of the cooling testing system and input helium flow on the performance of cooling. The experimental results showed that with 0.003 m3/s inlet helium flow, detectors’ temperature can be controlled under 75 °C while baking temperature is 250 °C in the cooling testing system. However, applying more effective cooling structure will increase the cooling performance. In addition, it was found that with the assistance of the DAQ system, the cooling
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