Ghidersa, Bradut Eugen

Starflinger, Jörg

Stieglitz, Robert

Wen, Wen

Wolfgang, Hering

English

KITopen

KIT – The Research University in the Helmholtz AssociationDEMO-Divertor Heat Pipe Concept (DIV-HP)• Divertor Heat Pipe target is made out of 230mm long cylindrical Heat Pipes (HPs) forming a staggered arrangement through which the target coolant flows. • HP capillary structure uses sintered porous in evaporator and open grooves for the restExperiment for evaluation of the boiling limit• The experiment aims to evaluate the boiling limit;• Specific Heat Pipe mock-ups focus on the evaporator performance(HPEE) under similar operating conditions as for DIV-HP.• Due to the manufacturing issues, the original porous structure (Cu with grain radius 118µm and 0.42 porosity) is replaced by one made out of bronze (CuSn10 with grain radius 400µm and 0.47 porosity).   • 2 sintered porous evaporator designs: - HPEE-1: a 2mm thick plain sintered porous structure- HPEE-2: a 2mm thick porous structure with 1mm depth grooves• Heat loading was applied using an electric cooper heater;• HPEE’s temperature variation was monitored by 9 thermocouples;• Power evaluated calorimetrically on the heat sink coolant side.Experimental heat transfer performance evaluation➢ Method• Water content is evaluated for three heat load ranges:• The heat sink’s coolant flow rate was set in 3 different ways :• (a) fixed flow rate (90l/h) maintained during different heating steps,• (b) flow rate adjusted to keep the coolant temperature increase constant (8°C ),• (c) flow rate adjusted to keep the condenser temperature constant at 80°C.• Each HPEE was filled initially with 1.5ml and had its performance evaluated by increasing the heat flux from 0.2 MW/m2stepwise with typical jump of 0.2MW/m2, until there were signs of dry-out, the flow rate increased to next level. Then, the water content was increased to the next quantity and the investigation repeated.➢ Experimental results• The 𝛥𝑇evaporator−condenser of both HPEEs were smaller than one from pure conductive heat transfer; • The difference reduced when liquid inventory increased until 2.0ml; • HPEE-2 didn’t show unstable temperature behavior with 2ml until 4.3MW/m2• Evaporator Heat Transfer characteristic is a function of the heat flux and 𝛥𝑇wall−H04: the temperature difference between the evaporator sintered porous and CuCrZr plate interface and the vapor temperature at HP04.• The Evaporator Heat Transfer characteristic reduced when the unstable behavior is observed. For the same loading conditions, HPEE-2 show better performance.• For HPEE-1, at the same heat flux, the difference between the measured temperature at evaporator wall and vapor was lower with higher water content. • 𝛥𝑇wall−H04 of HPEE-2 was lower than one of HPEE-1, except for the 1.5ml case.• The flow rate changes show less impact on the boiling curve. Experimental investigation of operating limits of a porous evaporator for a Heat Pipe-based DEMO Divertor Target concept Wen Wena, Bradut-Eugen Ghidersaa, Hering Wolfganga, Jörg Starflingerb, Robert StieglitzaObjectives• To evaluate the capability of a water-based Divertor Heat Pipe designed for heat fluxes as high as 20MW/m², the first experiment focused on the boiling limit of its evaporator with different sintered porous structures, (water) filling situations and heat sink conditions.Conclusions • HPEE-2 with grooves on sintered porous evaporator has better performance than HPEE-1;• Maximum heat flux 4.3MW/m2 was reached with HPEE-2 filled 2ml water, and there was no sign of the localized dry-out. However, the electric copper heater reached its operation limit.Individual Heat Pipea: Institute for Neutron Physics and Reactor Technology, Karlsruhe Institute of Technology , Karlsruhe, Germanyb: Institute of Nuclear Technology and Energy Systems , University of Stuttgart, Stuttgart, GermanyInstitute for Neutron Physics and Reactor Technology (INR) Karlsruhe Institute of Technology (KIT), Campus NordHermann-von-Helmholtz-Platz 176344 Eggenstein-Leopoldschafen, Germanyhttp://www.inr.kit.edu/(HPEE-1)                                                                  (HPEE-2)Temperature difference between evaporator and condenser (the solid line indicates a pure conductive heat transfer)EvaporatorDivertor Heat Pipe evaporator and Experiment mock-up modelGroovesPorousCondenser view inside Evaporator view insideJet impingement cooling at the condenser side  Electric copper heaterwith inserted 6 heater rods• 3 TEs : 5mm under the condenser surface• 2 TEs : in HPEE body for vapor temperature • 4 TEs : evaporator surfaceDivertor cassette assembly with a Heat Pipe-based targetMock-up with 9 thermal sensorsCoolant InletCoolant OutletCoolant InletCoolant OutletT_HP11T_HP09T_HP10T_HP08Heat load range Liquid inventory0-1MW/m2 1.5ml1-5MW/m2 1.7ml5-20MW/m2 2.0ml(HPEE-1)       Evaporator Heat Transfer characteristic (HPEE-2)(HPEE-1)                       Boiling curves (HPEE-2)UnstablebehaviorUnstable behaviorT_HP05T_HP06T_HP07T_HP03Filling lineT_HP04UnstablebehaviorUnstablebehaviorHPEE-1 HPEE-2VaporGravityαinclinexCoolant 130°CQEnvelopeCapillary part with groovesPorous medium z15 mm100TungstenCapSintered porous evaporator: with plain shape; with groovesGrooves width: 1mmGrooves depth:1mmDiameter: 26mmThickness: 2mm

Experimental investigation of operating limits of a porous evaporator for a Heat Pipe-based DEMO Divertor Target concept

https://publikationen.bibliothek.kit.edu/1000163055/151500092

Experimental investigation of operating limits of a porous evaporator for a Heat Pipe-based DEMO Divertor Target concept

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