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: Molten salt cooling

The use of molten salt for high heat flux component cooling is a current research topic. Heat flux densities of up to 10 MW/m² and volumetric heat sources of several MW/m³ require the application of methods to enhance convective heat transfer in cylindrical tubes. Initial investigations of swirl tapes and wire coil inserts show promising results in this regard. It can be assumed that the use of internally structured fluid-structure interfaces for the cooling of asymmetrically heated cylindrical divertor tubes is promising, and that — despite additional pressure and friction losses (at the same molten salt mass flow rate) — the ratio of heat transfer to required pumping power can be further improved. An optimally tailored design of fluid-structure interfaces — adapted to the boundary conditions of the divertor — requires a detailed thermo-fluid dynamic investigation of the underlying flow processes. The aim of this master thesis is to investigate the influence of rib-roughness on secondary flow-driven three-dimensional turbulent flows in circular pipes in more detail. The influence of roughness-induced flow structures on heat transfer and the drag coefficient in round pipes, taking geometric parameters into account, in order to gain a deeper understanding of the fluid mechanics and thermo-fluid dynamics processes and to obtain insights for the thermohydraulic optimization of such structural elements to increase convective heat transfer. As part of the master thesis, the thermal flow in a round pipe with a structured surface will be investigated in more detail using large eddy simulation. The heat transfer fluid used will be molten salt. Based on the expected velocity and temperature data, it will be possible to quantify the effects of rib-roughness on the thermal-fluid-dynamic flow field and convective heat transfer in order to formulate statements on the application of such structures in energy and heat technology.

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

• Familiarization with the topic: numerical fluid mechanics, turbulent flows, large eddy simulation, 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)