Dr.-Ing. Sebastian Ruck (sebastian.ruck@kit.edu)

Institute of Neutron Physics and Reactor Technology (INR)

Group: Thermal and Fluid-Dynamic System Design

Master thesis: Double Wall Heat Exchanger

The tritium produced in the fusion reactor leads to its accumulation in the primary circuit, necessitating both recovery strategies and effective barriers against tritium release. In addition to ensuring fuel self-sustainability, this serves to protect the environment. Due to high operating temperatures and large heat transfer surfaces, the intermediate heat exchangers in particular represent a critical path for tritium migration into the downstream heat transport circuit. Double-walled heat exchangers are being considered as a potential countermeasure; their use has already been discussed in early inertial fusion reactor concepts and in magnetic confinement fusion power plants (tokamak designs with FLiBe breeding blanket concepts). Initial investigations confirm the principle of using a purge gas flow in the interwall gap for tritium removal, but are limited to simplified studies. The applicability of these concepts to power plant-type shell-and-tube heat exchangers under realistic, fusion-specific boundary conditions has not yet been demonstrated or validated. Likewise, design guidelines for shell-and-tube heat exchangers with double-walled tubes (hereinafter referred to as double-walled heat exchangers (DWHX)) are lacking. The objective of this master's thesis is to investigate the convective heat transfer in a He-He-molten salt (HITEC) double-wall heat exchanger array using CFD. The aim is to analyze in detail the influence of geometric variations (diameter, gap width) and the Reynolds number on convective heat transfer.

The following tasks are planned as part of the master thesis:

• Familiarization with the topic: numerical fluid mechanics, turbulent flows, turbulence modelling, heat transfer
• Mesh adaption/generation, perform and supervise CFD simulations
• Analyzing, evaluation and discussion of the results in the context of the state of the art
• Written elaboration of the master thesis
• Presentation of results in a scientific colloquium at INR, KIT

Duration: Full-time 6 month at the INR

Starting Date: immediately

Institute of Neutron Physics and Reactor Technology (INR)

Group: Thermal and Fluid-Dynamic System Design

Contact and Supervisor: Dr.-Ing. Sebastian Ruck (sebastian.ruck@kit.edu)