Design and preparation of 3D and 2D axisymmetric multiphysics models for an inductive instant boiler simulation

Abstract

This paper presents the design and comprehensive validation of 3D and 2D axisymmetric Multiphysics models for a novel 100 kHz inductive instant boiler achieving 97% thermal efficiency. The research introduces a bidirectionally coupled electromagnetic-thermal finite element model implemented in COMSOL Multiphysics, incorporating temperature-dependent material properties and a ferromagnetic double-cylinder workpiece that forms a water channel for flow optimization. The 3D model demonstrates accurate prediction of skin depth effects (δ = 0.2 mm in steel at 100 kHz) with boundary layer meshing achieving <1% energy balance error. A computationally efficient 2D axisymmetric model reduces simulation time by 78% while maintaining accuracy within 2.3% of 3D results. Experimental validation confirms temperature predictions within ±1.8°C across the 30 °C to 95°C operating range. Grid Convergence Index analysis validates mesh independence with GCI < 0.8% for critical thermal parameters. The models are released 'ready for simulation' and constitute a foundation for future work on conjugate heat transfer., design optimization., and compliance., including MATLAB Simulink co-simulations.