Code validation (CFX EM) and methodology development of system code for numerical analysis of liquid metal breeder flow in KO TBM

MasterPressure loss of Magnetohydrodynamics (MHD) of liquid metal breeder flow is key issue in the Test Blanket Module (TBM) development. To reduce the load from the Lorentz force formed by interaction between liquid metal breeder flow and external magnetic field confining plasma, many researches about the MHD physics and design study of TBMs have been performed for a few decades in nuclear fusion engineering application. In the same context, this study is also to figure out the MHD physics, validate the ability of MHD calculation through commercial code (CFX) and suggest a methodology of development for system code which is able to reflect MHD on the channel flow. The commercial code, which is CFX EM module, will be employed to simulate the liquid metal flow in the KO TBM after this validation works, and it is used to consider and design the TBM concepts. System code, called MARS-FR, will be adopted to calculate bulk system flow and consider the safety and system load. In order to verify the MHD calculation, benchmarking problem comparison with previous experimental studies of the MHD channel flow is implemented. Among the experimental studies, cases, which are related with nuclear fusion engineering, are selected to be compared with CFX calculation. Those experiments have characteristics of strong magnetic field (~2T) and liquid lithium as a working fluid. Through the comparison procedure with several previous studies, both aspects of pressure loss and heat transfer of channel flow are investigated. In order to suggest the methodology of system code development, MHD calculation schemes and pilot, a test version of MARS, were surveyed and studied. According to semi-implicit calculation scheme of pilot, miyazaki MHD pressure loss calculation scheme is adopted to develop the one dimensional system code. CFX EM calculation of MHD pressure loss shows very good agreement with experimental results, while heat transfer could not agree very well. Pilot code is developed to reflect MHD pressure calculation, and it shows very good agreement with miyazaki solution. And, based on the validated result of CFX MHD calculation, the development methodology of system code is validated

Pool Boiling Study on Designed Microstructure Surface

DoctorThe effectiveness of microstructured surfaces in enhancing boiling heat transfer (BHT) and critical heat flux (CHF) was investigated with an experimental setup and fundamental bubble growth analysis. A set of pool boiling experiments was designed with microstructured surfaces and a bare surface. Samples were fabricated using microelectromechanical systems (MEMS) techniques. The samples were tested using pool boiling experiments under saturated and atmospheric pressure conditions. The bubble growth characteristics on the structured surface were visualized with high temporal and spatial resolution optical and infrared cameras. Boiling performance results showed that BHT increased with surface roughness, defined as the ratio of the rough surface area to the projected area, but this enhancement gradually slowed. The heat transfer coefficient of the structured surface was more than 300% greater than that of the bare surface. The increase in the heating surface area due to the roughness ratio improved nucleate BHT, and the enhancement was analyzed in terms of the fin effect of the microstructured surface. In terms of CHF, the structured surface showed a 350% improvement in CHF over the bare surface. However, through an analysis of the capillary flow rate on the structured surface, a critical gap size that limits CHF enhancement was found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF. Furthermore, a fundamental analysis of bubble growth on the structured surface was performed. Through a visualization technique, characteristics of bubble growth on the structured surface were analyzed, and the physical role of the designed microstructures on boiling performance enhancement was examined. Finally, the boiling performance of the designed microstructures was evaluated by comparison with other pool boiling research that showed performance enhancement by surface modification. The comparative analysis not only gave a reasonable explanation for the performance trend but also illustrated the excellent performance of the structures designed in this study

Pool boiling on hydrophilic and hydrophobic nano/microstructure with different wetting surfaces

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Pool boiling heat transfer on heterogeneous wetting surface with hydrophobic dots

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Visualization of thermal configuration of boiling phenomena on a heterogeneous wetting surface by the infrared camera

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Pool boiling experiments on modified heterogeneous wetting surfaces with teflon dots

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Numerical analysis of a liquid metal breeder flow in the korea helium cooled molten lithium TBM

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The study of bubble nucleation on a smooth oxidized silicon surface without microscopic cavities

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Numerical Analysis Code Validation and System Code Development for MHD Analysis in the Liquid Metal Breeder Flow in Korean TBM

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Bubble Nucleation on a Smooth Heating Surface with the Thermal Boundary Layer

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