Pool Boiling Heat Transfer Mechanisms in Low Gravity: Numerical Experiments of MABE and NPBX Data

The primary objectives for this PSI grant include establishing a deeper mechanistic understanding of nucleate boiling under low-gravity conditions by conducting high-fidelity numerical simulations that replicate the flight conditions of prior ISS-based boiling experiments, specifically MABE and NPBX. The investigation seeks to characterize key mechanisms governing bubble growth, waiting time, vapor spreading, coalescence, and detachment under variable gravity levels, degrees of wall superheat, and levels of liquid subcooling. Central to the objectives is quantifying how heat flux divides between nucleate boiling and natural convection modes, evaluating how the contact angle modulates wall adhesion forces, and determining the precise contribution of microlayer evaporation to heat transfer during low-gravity operation. By leveraging validated direct-numerical-simulation approaches tied to empirical MABE and NPBX measurements, this objective generates fundamental physics-based insights that enable predictive modeling of boiling processes relevant to spacecraft systems and advanced thermal architectures.