Multi-Site Nucleate Boiling Predictions for Cryogenic Cooling of High-Power Linear Collider Structures

Efficient thermal management is critical for high-power systems such as next-generation high-energy e⁺e^- linear colliders based on cryogenically cooled copper technology. In this concept, a cryogenic copper distributed-coupling accelerating structure enables reduced operating costs while maintaining high efficiency and compactness. Achieving the required operating conditions demands reliable and economical cooling, for which cryogenic two-phase flow is a promising solution, provided its boiling behavior is well characterized. Here, we present three-dimensional simulations of liquid nitrogen nucleate pool boiling using a multiphase, interface-tracking CFD framework with adaptive mesh refinement. The model incorporates conjugate heat transfer and a specialized microlayer formulation, with nucleation sites randomly distributed and activated based on experimentally calibrated temperatures. The performance of the model and its validation against previous benchmark data for heat transfer coefficients and bubble dynamics will be discussed. Parametric studies reveal the effects of surface superheat and nucleation site density on heat transfer enhancement, providing mechanistic insights into cryogenic boiling behavior.