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Report RSE 18000039

Development of simulation methods for the study of fluidodynamic phenomena in innovative configuration of superconductive cable cryostats

Report

2017

Request Document (6.13 MB, .pdf)

M. Bocchi (RSE SpA), G. Angeli (RSE SpA)

MAT4-GRID 2017 - Equipment and components for electricity grids

Development and implementation in calculation programs of mathematical models to simulate the thermo-fluid dynamic behavior of new cryostat types for superconducting cables that require the simultaneous use of several different cryogenic fluids. The results related to the simulation of the case of a double-chamber cryostat that uses two fluids in forced convection: gaseous helium, as "cold" fluid, and liquid nitrogen, as "hot" fluid are reported.

The main objective achieved with this work has been the development (and implementation in dedicated codes) mathematical models that allow to simulate the thermo fluido-dynamic behavior of cryogenic fluids. These fluids are conveyed in forced convection within the new types of cryostat for superconducting cables that provide for the simultaneous use of several different cryogenic fluids. In particular, it is important to evaluate the stability of the behavior of the superconducting cable when conditions which may affect the efficiency of its refrigeration change. This behavior can affect the electromagnetic behavior and therefore the reliability and safety of the cable itself.

In this study, starting from the derivation of the fundamental equations of fluido-dynamics, a new mathematical model was developed that describes the coupled thermo-fluid dynamic behavior of cryostats with more than one fluid. Starting from this model a calculation code was implemented. In this code, numerical methods were implemented for the solution of the non-linear differential equations system that constitute the core of the model. The code is parametric and therefore it is possible to effectively perform sensitivity analysis of the behavior of cryogenic fluids respect to the variation of the operating parameters in the cryostat of the superconducting cable.

The simulations carried out with the abovementioned model and the code relate to a superconducting cable cryostat with a double-chamber, which, therefore, employs two fluids in forced convection: gaseous helium, as "cold" fluid, and liquid nitrogen, as "hot" fluid. In particular, the results reported in this report concern the simulations performed varying four input parameters:

• the liquid nitrogen flow rate in the external pipe;
• the gaseous helium flow rate in the inner pipe;
• the value of the thermal inputs through the internal casing;
• the value of the thermal inputs through the external casing.

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