Abstract
Harnessing energy by nuclear fusion has progressed into technological developments as a result of sufficient progress made in the theoretical investigations. Fueling a tokamak by pellet injection is reported to be most efficient among other fueling techniques. It is thus important to produce a solid hydrogen filament by extrusion process using an extruder-die setup. It is required to arrive at an optimum configuration of the die as the pressure drop in the die decides the load on the extruder. The present analysis focuses on developing a CFD model of a die taking into account the complex rheological behavior of solid hydrogen. A systematic parametric analysis is performed to study the influence of die geometry on the flow behavior. The un-yielded regions are identified from the simulation results. It has been found that the un-yielded region decreases as the contraction ratio and contraction angle is decreased. The un-yielded zone is predominantly present in the region before contraction. However, at lower flow rates, the un-yielded zone appears even after the contraction.
Highlights
Nuclear fusion promises to be a viable alternative for the ever rising energy demand
The present analysis focuses on developing a CFD model of a die taking into account the complex rheological behavior of solid hydrogen
As it is tedious to develop a numerical model for the extruder and the die together due to intricacies involved in meshing the flow geometry, the modelling of the die and extruder are carried out separately and their pressure-flow rate characteristics are superimposed to obtain the operation point[2]
Summary
Nuclear fusion promises to be a viable alternative for the ever rising energy demand. Mitsoulis and Abdali[3] developed a FEM model to study the flow of visco-plastic fluids through extrusion die to identify the un-yielded zone and its influence on pressure drop. The above mention work reveals the influence of geometry, rheology and flow morphology on the pressure characteristics This present work intends to develop a robust 3D non-Newtonian CFD model for solid hydrogen flow through die. Another objective of this paper is to arrive at a geometric configuration with minimized viscous dissipation rate for a given flow rate of 500 mm3/s. Assuming Newtonian behavior (equation (2)) of solid hydrogen, Vinyar and Lukin[7] related pressure drop and flow rate using the Buckingham formula (equation (1)) for the die with constant cross section. The die characteristics obtained using the above correlations are presented in results and discussions section
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