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Thermohydraulic experimental design for the European Helium-Cooled-Pebble-Bed Test Blanket Module
Fusion Engineering and Design 83 (2008) 1253–1257
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Thermohydraulic experimental design for the European Helium-Cooled-Pebble-Bed Test Blanket Module M. Ilic´ a,∗ , B. Kiss b , T. Ihli a a b
Institut für Reaktorsicherheit, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany Institute of Nuclear Techniques, Budapest University of Technology and Economics, Muegyetem rkp. 3-9, Budapest, Hungary
a r t i c l e
i n f o
Article history: Available online 10 July 2008 Keywords: Test blanket module Heat transfer Flow distribution Experimental facilities
a b s t r a c t The peculiarities of the coolant flow in Helium-Cooled-Pebble-Bed Test Blanket Module (TBM) are (i) very intensive heating of the first wall from the plasma side and (ii) very complicated geometry of flow domain consisting of large coolant collectors with numerous flow obstacles and long narrow channels meandering in the first wall, cap, stiffening and cooling plates. In relation to this, at the Institute for Reactor Safety in Forschungszentrum Karlsruhe two thermohydraulic aspects of TBM coolant system are investigated: heat removal from the first wall in the framework of HETRA experiment and mass flow distribution among different components of the TBM coolant system in GRICAMAN experiments. This paper presents the design of corresponding experimental facilities. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The Helium-Cooled-Pebble-Bed Test Blanket Module (hereafter TBM) developed in Forschungszentrum Karlsruhe is one of two blanket concepts chosen in the Frame of the European Blanket Programme as a DEMO relevant Blanket [1,2]. This Blanket Module has as outer boundary a helium-cooled steel structure named the first wall. The first wall is reinforced with a stiffening grid structure involving 15 vertical and 12 horizontal plates with internal cooling. In this structure 18 breeding units each involving four cooling plates are inserted and fixed. In the back part of Blanket box three coolant collectors are arranged: manifold 1, manifold 2 and manifold 3. The fourth manifold consists of three collectors, so-called ships, which cross the other three manifolds. The Blanket box is closed with two internally cooled plates named caps. All these components belong to the coolant system of TBM in which the following flow distribution is imposed by the design. The coolant, helium at 8 MPa and 573 K, enters the manifold 1 with mass flow rate of 1.2 kg/s. From manifold 1 the helium is uniformly distributed among 12 parallel cooling channels in the first wall. The outflow from the first wall is collected in the manifold 2, from where 0.56 kg/s is through by-pass pipe taken out of
∗ Corresponding author. Tel.: +49 7247 82 29 49. ´ E-mail address: [email protected] (M. Ilic). 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.05.031
the system, 0.38 kg/s is uniformly distributed among 27 stiffening grid plates and 0.25 kg/s is equally shared between two caps. Within each cap eight different cooling channels with specified flow rates of the coolant are foreseen. The helium from grid and cap channels enters manifold 3 and is than uniformly distributed among 18 breeding units. The outflow from breeding units is led into the manifold 4 from where it, finally, leaves TBM. Taking into account the complexity of TBM flow domain it is of ultimate importance to examine whether such a flow distribution can take place. Beside the complex flow distribution the design of TBM coolant system imposes peculiar conditions for the heat removal from the first wall due to an extreme asymmetry of heat loads with the heat flux of 270 kW/m2 on the plasma facing side that in an excess case can reach 500 kW/m2 and the heat flux of only 60 kW/m2 on the side of breeding units. As such conditions cause steep temperature gradients and, therefore, strong thermal stresses, a reliable determination of temperature distribution in the first wall plays a deciding role in TBM design. In relation to the aforementioned, at the Institute for Reactor Safety of Forschungszentrum Karlsruhe two thermohydraulic aspects of TBM are currently under detailed investigation: The HETRA experiment in the framework of development activities for the first wall cooling and the GRICAMAN experiments in regard on the mass flow distribution among different as well as within individual components of the TBM coolant system. This paper presents the design of corresponding experimental facilities.
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Fig. 1. Main components of HETRA facility.
2. HETRA experiment for investigation of heat transfer in the first wall of Helium-Cooled-Pebble-Bed Test Blanket Module The HETRA experiment has been motivated by corresponding three-dimensional numerical analyses [3] which revealed significant effects of the asymmetrical heat loads on the cooling of the first wall. It has been found that the heat transfer coefficient in the first wall is ∼15% lower than the one predicted by one-dimensional heat transfer evaluations based on Dittus-Boelter-like correlations and that satisfactory cooling of the first wall can be achieved only with hydraulically rough channels. Additionally, due to strong temperature gradients in the cross-section of the first wall, the procedure for heat transfer evaluations applied in codes for stress analyses has to be modified in order to obtain reliable predictions of thermal stresses. The verification of the developed methods will be done on the basis of the results of the HETRA experimental campaign. The main components of HETRA experimental facility are presented in Fig. 1. The facility involves only one U sweep of the first wall channel with belonging steel structure because the corresponding computational results show similar behaviour of the mean heat transfer coefficient along all three channel sections. The cooling channel in HETRA test section will be fabricated from EUROFER by milling channel halves and their welding with electron beam. The long straight section representing plasma facing part of the first wall will be connected by flanges to the two channel bends to enable tests with different roughness of the channel surface. The first tests will be done with the absolute roughness of the chan-
Fig. 2. Cross-section through HETRA test section.
nel wall of 20 m as the numerical results have shown that this magnitude provides reliable cooling of the first wall. The test section will be heated only on the side representing plasma facing side of the first wall. The heating of the back side of the first wall which in TBM comes from breeding units is in HETRA experiments neglected due to its multiple lower magnitude. The heat flux of 270 kW/m2 at the plasma facing side of the first wall is in HETRA experiments simulated by a set of eight flat ceramic heaters. To ensure uniform heat flux and to diminish effects of imperfect thermal contact, surface of both, the heaters and the first wall, is covered by thin graphite layers (thickness of 0.5 mm) between which a 10-mm layer of copper is placed (see Fig. 2). The whole facility is covered with 10 mm thick insulation. The tests will be done in a Helium cycle at 8 MPa for mass flow rate of 0.1 kg/s and inlet temperature of 573 K. As the temperature measurements within the flow domain would disturb the fluid stream significantly due to high coolant velocities, the computational results will be verified only via experimentally determined
Fig. 3. Planes along HETRA test section at which sets of temperature measurements are defined.
M. Ili´c et al. / Fusion Engineering and Design 83 (2008) 1253–1257
1255
steel temperatures. For that purpose eight sets of temperature measurements will be performed along the heated section (see Fig. 3). Within each set the temperature of the steel will be measured at five positions. The measurements will be done applying thermocouples with diameter of 0.5 mm. The thermocouples will be inserted orthogonally to the heat flux (from bottom/top side of heated section) in order to minimize temperature gradients along the thermocouple cable. The measuring planes will be positioned in the middle of the heating elements to avoid the effects of the discrete heaters.
3. GRICAMAN experiments for investigation of flow distribution in Helium-Cooled-Pebble-Bed Test Blanket Module The main goals of GRICAMAN experiments are (i) to investigate whether the mass flow distribution in the manifold 2 among the caps and stiffening grid channels corresponds to the designed one, (ii) to investigate whether individual stiffening grid and cap channels are supplied with designed portion of coolant flow and (iii) to investigate whether the mass flow distribution among breeding units is uniform. In relation to this, the flow domain to be investigated in GRICAMAN experiments is defined to be the upper toroidal–poloidal half of TBM bounded at the outlets of first wall channels, at the outlets of by-pass pipes and at the inlets of breeding units, i.e. involving one half of the manifold 2, cooling channels in six horizontal and eight vertical stiffening grid plates, cooling channels within one cap and one half of the manifold 3. Significant simplifications of the experimental facility and numerical models are achieved (i) assuming that the flow is adiabatic, (ii) replacing helium at 8 MPa and 643 K with air pressurized at 0.3 MPa and ambient temperature and (iii) representing real grid and cap channels by simplified channels that have the same flow resistance (hereafter called equivalent grid/cap channels). The GRICAMAN facility designed using the aforementioned assumptions is presented in Fig. 4. The measuring scheme with all auxiliary components included is given in Fig. 5. Note that the upper halves of the manifold 2 and the manifold 3 are for an easier connection rotated for 180◦ . At the sides of manifold 2 outlet parts of six first wall channels with real geometry of the channel cross-section are connected. These channels are supplied with pressurized air in the following way. Air flow rate of 912.6 Nm3 /h taken from the main supply line of pressurized air in Forschungszentrum Karlsruhe is first led into a buffer tank and then filtered so that all the particles larger than 0.01 m are eliminated. The air pressure at the inlet of GRICAMAN facility is kept constant applying an electro-pneumatic pressure regulator. After the pressure regulator the air is led into an inlet distributor which feeds first wall channels with pressurized air via corresponding supply lines. At each supply line a calorimetric flow meter and a needle valve are arranged to control and adjust the air flow rate of 152.5 Nm3 /h required for each first wall channel. At the front side of the manifold 2 the by-pass openings are set. The flow rate taken out through these openings is controlled via a calorimetric flow meter and a needle valve. At the back side of the manifold 2 in total 14 equivalent grid channels are connected. Each equivalent grid channel involves three sections: (i) an inlet part with real cross-section of grid channels to provide a realistic connection to the manifold 2, (ii) a circular pipe of DN 3/4 in. at which a flow meter and a pinch valve are arranged and (iii) an outlet part connected to the manifold 3 with real cross-section of grid channels. At the lower side of the manifolds equivalent cap channels are connected. These channels are designed similar to the equivalent grid channels: real cross-section of cap channels is kept at sections connected to manifolds and the middle part is replaced by
Fig. 4. Main components of GRICAMAN experimental facility.
circular tubes. The length and shape of equivalent grid/cap channels is chosen to provide ∼2/3 of the total pressure drop in real cooling channels within grid/cap. The remaining 1/3 should be performed by local throttling with the pinch valve. At the back side of the manifold 3 in total nine equivalent breeding unit pipes are connected. Each of them involves a flow meter and a needle valve for adjustment of the corresponding hydraulic resistance. The air leaving equivalent breeding unit pipes is collected in an outlet collector and led out of the system. Measurements of the following flow quantities are of special interest in GRICAMAN experiments: (i) air flow rate in individual grid/cap channels and in equivalent breeding unit pipes to determine flow rate distribution in manifold 2 and manifold 3 respectively and (ii) differential pressure measurements to determine pressure distribution in manifold boxes, i.e. conditions at inlets of cooling channels in stiffening grids, caps and breeding units. Air flow rate will be measured by flow meters inserted in each of 22 equivalent grid/cap channels and by calorimetric flow meters arranged at each of nine equivalent breeding unit pipes. The prerequisite that these measurements reveal the flow distribution in TBM manifolds is that an equivalent channel/pipe has the same flow resistance as the real one. For that reason, before assembled in GRICAMAN facility each equivalent channel will be calibrated. The calibration will be done by adjusting pinch valve at equivalent grid/cap channels, i.e. needle valves at equivalent breeding unit pipes to achieve the pressure drop determined by detailed experimental/numerical investigations of the fluid flow in corresponding real channels. The pressure measurements in manifold 2 have been motivated by numerical simulations of fluid flow in GRICAMAN facility which revealed low pressure domains in regions where air with high velocity enters from the first wall and in the region surrounding by-pass openings. To verify these results differential pressure in manifold 2 will be measured along: the line parallel with the axis
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Fig. 5. Flow diagram and measuring scheme for GRICAMAN experimental facility.
of by-pass openings, the line lying in the middle between the upper vertical grid inlets and the line lying in the middle between the lower vertical grid inlets (denoted respectively as Line I, Line II and Line IIIin Fig. 5).
As numerical results have not indicated any strong pressure gradients in the manifold 3 the attention has been focused to the determination of pressure distribution at inlets of equivalent breeding unit pipes. In relation to this, Line IV, Line V and Line VI in Fig. 5
M. Ili´c et al. / Fusion Engineering and Design 83 (2008) 1253–1257
are defined along which pressure measuring positions are placed 50 mm away from the axis of corresponding breeding unit pipe where the pressure profiles are expected to be flat. It is, however, noted that two of the lines (Line V and Line VI) are not straight due to attachments of outlet grid channels that block access to left/right side of corresponding breeding unit. In such cases, pressure measuring positions are placed 50 mm up/down of the breeding unit axis. 4. Conclusions This paper presents design of two experimental facilities developed at the Institute for Reactor Safety in Forschungszentrum Karlsruhe for thermohydraulic analyses of Helium-Cooled-Test Blanket Module: (i) HETRA facility for studying the heat removal from the first wall and (ii) GRICAMAN facility for investigation of flow distribution in TBM coolant system. HETRA facility has been designed for verification of numerically found effects of asymmetrical heating on the cooling of the first wall. The investigations will be performed for a portion of the first wall containing one U sweep of the cooling channel. The tests will be done in a Helium cycle at 80 bars. The heat load of 270 kW/m2 on the surface representing plasma facing side of the first wall will be achieved by a set of electrical heaters. The numerical results will be verified through comparison with detailed temperature measurements in the steel structure. GRICAMAN flow domain involves the upper toroidal–poloidal half of TBM bounded at outlets of first wall channels, at the outlet of by-pass pipe and at outlets of breeding units. The facility is designed
1257
keeping real geometry of manifold 2 and manifold 3 and replacing complicated cooling channels within stiffening grids, caps and breeding units with simple equivalent channels having the same flow resistance. The flow distribution in manifold 2 will be determined measuring flow rates through each of 22 equivalent grid/cap channels. For experimental determination of flow distribution in manifold 3 flow rate will be measured in each of nine equivalent breeding unit pipes. In order to provide data for experimental verification of corresponding numerical model a number of pressure measurements are foreseen along manifold 2 and manifold 3. Acknowledgments This work, supported by the European Communities under the contract of Association between EURATOM and Forschungszentrum Karlsruhe, was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] L.V. Boccaccini, J.-F. Salavy, R. Lässer, A. Li Puma, R. Meyder, H. Neuberger, Y. Poitevin, G. Rampal, The European Test Blanket Module Systems: Design and Integration in ITER, Fusion Engineering and Design 81 (2006) 407–414. [2] Y. Poitevin, L.V. Boccaccini, A. Cardela, L. Fiancarli, R. Meyder, E. Diegele, R. Laesser, G. Benamati, The European Breeding Blankets Development and the Test Strategy in ITER, Fusion Engineering and Design 75–79 (2005) 741–749. ´ R. Meyder, R. Dolensky, B. Kiss, Analysis of Heat Transfer in the First Wall [3] M. Ilic, of the HCPB TBM of ITER, Jahrestagung Kerntechik, Aachen, 2006.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Thermohydraulic experimental design for the European Helium-Cooled-Pebble-Bed Test Blanket Module M. Ilic´ a,∗ , B. Kiss b , T. Ihli a a b
Institut für Reaktorsicherheit, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany Institute of Nuclear Techniques, Budapest University of Technology and Economics, Muegyetem rkp. 3-9, Budapest, Hungary
a r t i c l e
i n f o
Article history: Available online 10 July 2008 Keywords: Test blanket module Heat transfer Flow distribution Experimental facilities
a b s t r a c t The peculiarities of the coolant flow in Helium-Cooled-Pebble-Bed Test Blanket Module (TBM) are (i) very intensive heating of the first wall from the plasma side and (ii) very complicated geometry of flow domain consisting of large coolant collectors with numerous flow obstacles and long narrow channels meandering in the first wall, cap, stiffening and cooling plates. In relation to this, at the Institute for Reactor Safety in Forschungszentrum Karlsruhe two thermohydraulic aspects of TBM coolant system are investigated: heat removal from the first wall in the framework of HETRA experiment and mass flow distribution among different components of the TBM coolant system in GRICAMAN experiments. This paper presents the design of corresponding experimental facilities. © 2008 Elsevier B.V. All rights reserved.
1. Introduction The Helium-Cooled-Pebble-Bed Test Blanket Module (hereafter TBM) developed in Forschungszentrum Karlsruhe is one of two blanket concepts chosen in the Frame of the European Blanket Programme as a DEMO relevant Blanket [1,2]. This Blanket Module has as outer boundary a helium-cooled steel structure named the first wall. The first wall is reinforced with a stiffening grid structure involving 15 vertical and 12 horizontal plates with internal cooling. In this structure 18 breeding units each involving four cooling plates are inserted and fixed. In the back part of Blanket box three coolant collectors are arranged: manifold 1, manifold 2 and manifold 3. The fourth manifold consists of three collectors, so-called ships, which cross the other three manifolds. The Blanket box is closed with two internally cooled plates named caps. All these components belong to the coolant system of TBM in which the following flow distribution is imposed by the design. The coolant, helium at 8 MPa and 573 K, enters the manifold 1 with mass flow rate of 1.2 kg/s. From manifold 1 the helium is uniformly distributed among 12 parallel cooling channels in the first wall. The outflow from the first wall is collected in the manifold 2, from where 0.56 kg/s is through by-pass pipe taken out of
∗ Corresponding author. Tel.: +49 7247 82 29 49. ´ E-mail address: [email protected] (M. Ilic). 0920-3796/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2008.05.031
the system, 0.38 kg/s is uniformly distributed among 27 stiffening grid plates and 0.25 kg/s is equally shared between two caps. Within each cap eight different cooling channels with specified flow rates of the coolant are foreseen. The helium from grid and cap channels enters manifold 3 and is than uniformly distributed among 18 breeding units. The outflow from breeding units is led into the manifold 4 from where it, finally, leaves TBM. Taking into account the complexity of TBM flow domain it is of ultimate importance to examine whether such a flow distribution can take place. Beside the complex flow distribution the design of TBM coolant system imposes peculiar conditions for the heat removal from the first wall due to an extreme asymmetry of heat loads with the heat flux of 270 kW/m2 on the plasma facing side that in an excess case can reach 500 kW/m2 and the heat flux of only 60 kW/m2 on the side of breeding units. As such conditions cause steep temperature gradients and, therefore, strong thermal stresses, a reliable determination of temperature distribution in the first wall plays a deciding role in TBM design. In relation to the aforementioned, at the Institute for Reactor Safety of Forschungszentrum Karlsruhe two thermohydraulic aspects of TBM are currently under detailed investigation: The HETRA experiment in the framework of development activities for the first wall cooling and the GRICAMAN experiments in regard on the mass flow distribution among different as well as within individual components of the TBM coolant system. This paper presents the design of corresponding experimental facilities.
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Fig. 1. Main components of HETRA facility.
2. HETRA experiment for investigation of heat transfer in the first wall of Helium-Cooled-Pebble-Bed Test Blanket Module The HETRA experiment has been motivated by corresponding three-dimensional numerical analyses [3] which revealed significant effects of the asymmetrical heat loads on the cooling of the first wall. It has been found that the heat transfer coefficient in the first wall is ∼15% lower than the one predicted by one-dimensional heat transfer evaluations based on Dittus-Boelter-like correlations and that satisfactory cooling of the first wall can be achieved only with hydraulically rough channels. Additionally, due to strong temperature gradients in the cross-section of the first wall, the procedure for heat transfer evaluations applied in codes for stress analyses has to be modified in order to obtain reliable predictions of thermal stresses. The verification of the developed methods will be done on the basis of the results of the HETRA experimental campaign. The main components of HETRA experimental facility are presented in Fig. 1. The facility involves only one U sweep of the first wall channel with belonging steel structure because the corresponding computational results show similar behaviour of the mean heat transfer coefficient along all three channel sections. The cooling channel in HETRA test section will be fabricated from EUROFER by milling channel halves and their welding with electron beam. The long straight section representing plasma facing part of the first wall will be connected by flanges to the two channel bends to enable tests with different roughness of the channel surface. The first tests will be done with the absolute roughness of the chan-
Fig. 2. Cross-section through HETRA test section.
nel wall of 20 m as the numerical results have shown that this magnitude provides reliable cooling of the first wall. The test section will be heated only on the side representing plasma facing side of the first wall. The heating of the back side of the first wall which in TBM comes from breeding units is in HETRA experiments neglected due to its multiple lower magnitude. The heat flux of 270 kW/m2 at the plasma facing side of the first wall is in HETRA experiments simulated by a set of eight flat ceramic heaters. To ensure uniform heat flux and to diminish effects of imperfect thermal contact, surface of both, the heaters and the first wall, is covered by thin graphite layers (thickness of 0.5 mm) between which a 10-mm layer of copper is placed (see Fig. 2). The whole facility is covered with 10 mm thick insulation. The tests will be done in a Helium cycle at 8 MPa for mass flow rate of 0.1 kg/s and inlet temperature of 573 K. As the temperature measurements within the flow domain would disturb the fluid stream significantly due to high coolant velocities, the computational results will be verified only via experimentally determined
Fig. 3. Planes along HETRA test section at which sets of temperature measurements are defined.
M. Ili´c et al. / Fusion Engineering and Design 83 (2008) 1253–1257
1255
steel temperatures. For that purpose eight sets of temperature measurements will be performed along the heated section (see Fig. 3). Within each set the temperature of the steel will be measured at five positions. The measurements will be done applying thermocouples with diameter of 0.5 mm. The thermocouples will be inserted orthogonally to the heat flux (from bottom/top side of heated section) in order to minimize temperature gradients along the thermocouple cable. The measuring planes will be positioned in the middle of the heating elements to avoid the effects of the discrete heaters.
3. GRICAMAN experiments for investigation of flow distribution in Helium-Cooled-Pebble-Bed Test Blanket Module The main goals of GRICAMAN experiments are (i) to investigate whether the mass flow distribution in the manifold 2 among the caps and stiffening grid channels corresponds to the designed one, (ii) to investigate whether individual stiffening grid and cap channels are supplied with designed portion of coolant flow and (iii) to investigate whether the mass flow distribution among breeding units is uniform. In relation to this, the flow domain to be investigated in GRICAMAN experiments is defined to be the upper toroidal–poloidal half of TBM bounded at the outlets of first wall channels, at the outlets of by-pass pipes and at the inlets of breeding units, i.e. involving one half of the manifold 2, cooling channels in six horizontal and eight vertical stiffening grid plates, cooling channels within one cap and one half of the manifold 3. Significant simplifications of the experimental facility and numerical models are achieved (i) assuming that the flow is adiabatic, (ii) replacing helium at 8 MPa and 643 K with air pressurized at 0.3 MPa and ambient temperature and (iii) representing real grid and cap channels by simplified channels that have the same flow resistance (hereafter called equivalent grid/cap channels). The GRICAMAN facility designed using the aforementioned assumptions is presented in Fig. 4. The measuring scheme with all auxiliary components included is given in Fig. 5. Note that the upper halves of the manifold 2 and the manifold 3 are for an easier connection rotated for 180◦ . At the sides of manifold 2 outlet parts of six first wall channels with real geometry of the channel cross-section are connected. These channels are supplied with pressurized air in the following way. Air flow rate of 912.6 Nm3 /h taken from the main supply line of pressurized air in Forschungszentrum Karlsruhe is first led into a buffer tank and then filtered so that all the particles larger than 0.01 m are eliminated. The air pressure at the inlet of GRICAMAN facility is kept constant applying an electro-pneumatic pressure regulator. After the pressure regulator the air is led into an inlet distributor which feeds first wall channels with pressurized air via corresponding supply lines. At each supply line a calorimetric flow meter and a needle valve are arranged to control and adjust the air flow rate of 152.5 Nm3 /h required for each first wall channel. At the front side of the manifold 2 the by-pass openings are set. The flow rate taken out through these openings is controlled via a calorimetric flow meter and a needle valve. At the back side of the manifold 2 in total 14 equivalent grid channels are connected. Each equivalent grid channel involves three sections: (i) an inlet part with real cross-section of grid channels to provide a realistic connection to the manifold 2, (ii) a circular pipe of DN 3/4 in. at which a flow meter and a pinch valve are arranged and (iii) an outlet part connected to the manifold 3 with real cross-section of grid channels. At the lower side of the manifolds equivalent cap channels are connected. These channels are designed similar to the equivalent grid channels: real cross-section of cap channels is kept at sections connected to manifolds and the middle part is replaced by
Fig. 4. Main components of GRICAMAN experimental facility.
circular tubes. The length and shape of equivalent grid/cap channels is chosen to provide ∼2/3 of the total pressure drop in real cooling channels within grid/cap. The remaining 1/3 should be performed by local throttling with the pinch valve. At the back side of the manifold 3 in total nine equivalent breeding unit pipes are connected. Each of them involves a flow meter and a needle valve for adjustment of the corresponding hydraulic resistance. The air leaving equivalent breeding unit pipes is collected in an outlet collector and led out of the system. Measurements of the following flow quantities are of special interest in GRICAMAN experiments: (i) air flow rate in individual grid/cap channels and in equivalent breeding unit pipes to determine flow rate distribution in manifold 2 and manifold 3 respectively and (ii) differential pressure measurements to determine pressure distribution in manifold boxes, i.e. conditions at inlets of cooling channels in stiffening grids, caps and breeding units. Air flow rate will be measured by flow meters inserted in each of 22 equivalent grid/cap channels and by calorimetric flow meters arranged at each of nine equivalent breeding unit pipes. The prerequisite that these measurements reveal the flow distribution in TBM manifolds is that an equivalent channel/pipe has the same flow resistance as the real one. For that reason, before assembled in GRICAMAN facility each equivalent channel will be calibrated. The calibration will be done by adjusting pinch valve at equivalent grid/cap channels, i.e. needle valves at equivalent breeding unit pipes to achieve the pressure drop determined by detailed experimental/numerical investigations of the fluid flow in corresponding real channels. The pressure measurements in manifold 2 have been motivated by numerical simulations of fluid flow in GRICAMAN facility which revealed low pressure domains in regions where air with high velocity enters from the first wall and in the region surrounding by-pass openings. To verify these results differential pressure in manifold 2 will be measured along: the line parallel with the axis
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Fig. 5. Flow diagram and measuring scheme for GRICAMAN experimental facility.
of by-pass openings, the line lying in the middle between the upper vertical grid inlets and the line lying in the middle between the lower vertical grid inlets (denoted respectively as Line I, Line II and Line IIIin Fig. 5).
As numerical results have not indicated any strong pressure gradients in the manifold 3 the attention has been focused to the determination of pressure distribution at inlets of equivalent breeding unit pipes. In relation to this, Line IV, Line V and Line VI in Fig. 5
M. Ili´c et al. / Fusion Engineering and Design 83 (2008) 1253–1257
are defined along which pressure measuring positions are placed 50 mm away from the axis of corresponding breeding unit pipe where the pressure profiles are expected to be flat. It is, however, noted that two of the lines (Line V and Line VI) are not straight due to attachments of outlet grid channels that block access to left/right side of corresponding breeding unit. In such cases, pressure measuring positions are placed 50 mm up/down of the breeding unit axis. 4. Conclusions This paper presents design of two experimental facilities developed at the Institute for Reactor Safety in Forschungszentrum Karlsruhe for thermohydraulic analyses of Helium-Cooled-Test Blanket Module: (i) HETRA facility for studying the heat removal from the first wall and (ii) GRICAMAN facility for investigation of flow distribution in TBM coolant system. HETRA facility has been designed for verification of numerically found effects of asymmetrical heating on the cooling of the first wall. The investigations will be performed for a portion of the first wall containing one U sweep of the cooling channel. The tests will be done in a Helium cycle at 80 bars. The heat load of 270 kW/m2 on the surface representing plasma facing side of the first wall will be achieved by a set of electrical heaters. The numerical results will be verified through comparison with detailed temperature measurements in the steel structure. GRICAMAN flow domain involves the upper toroidal–poloidal half of TBM bounded at outlets of first wall channels, at the outlet of by-pass pipe and at outlets of breeding units. The facility is designed
1257
keeping real geometry of manifold 2 and manifold 3 and replacing complicated cooling channels within stiffening grids, caps and breeding units with simple equivalent channels having the same flow resistance. The flow distribution in manifold 2 will be determined measuring flow rates through each of 22 equivalent grid/cap channels. For experimental determination of flow distribution in manifold 3 flow rate will be measured in each of nine equivalent breeding unit pipes. In order to provide data for experimental verification of corresponding numerical model a number of pressure measurements are foreseen along manifold 2 and manifold 3. Acknowledgments This work, supported by the European Communities under the contract of Association between EURATOM and Forschungszentrum Karlsruhe, was carried out within the framework of the European Fusion Development Agreement. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] L.V. Boccaccini, J.-F. Salavy, R. Lässer, A. Li Puma, R. Meyder, H. Neuberger, Y. Poitevin, G. Rampal, The European Test Blanket Module Systems: Design and Integration in ITER, Fusion Engineering and Design 81 (2006) 407–414. [2] Y. Poitevin, L.V. Boccaccini, A. Cardela, L. Fiancarli, R. Meyder, E. Diegele, R. Laesser, G. Benamati, The European Breeding Blankets Development and the Test Strategy in ITER, Fusion Engineering and Design 75–79 (2005) 741–749. ´ R. Meyder, R. Dolensky, B. Kiss, Analysis of Heat Transfer in the First Wall [3] M. Ilic, of the HCPB TBM of ITER, Jahrestagung Kerntechik, Aachen, 2006.