Heat Transfer in Flow Boiling Conditions for Swirl Tube Elements Customizing the ANSYS Software

A heat transfer model with water coolant in flow boiling conditions for swirl tube elements is simulated customizing a programmable routine and relinking the ANSYS code. The standard ANSYS features calculate the film coefficient for forced convection conditions in the singlephase flow without possibility of take into account flow boiling conditions. The heat transfer coefficient is redefined in a general way customizing ANSYS by a user programmable routine to simulate the actual heat transfer in forced convection and flow boiling conditions. The modified routine is called for each iteration, once per element, and during each sub-step of each load-step. The heat transfer coefficient is calculated as a function of heat flux, surface and coolant temperatures, water saturation curve, fluid dynamic properties of coolant, twist tape pitch, and location. A special function is implemented in the customized routine to reduce significantly the number of solution iterations. This function mitigates the heat flux instabilities due to nucleate boiling in the near-wall surface elements. The customized ANSYS code is used to carry out thermo-hydraulic and thermo-structural analyses for the design of high heat flux components of the neutral beam injector for the international thermonuclear experimental reactor ITER.

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