Principal Investigator Jacopo Buongiorno
Revolutionary advances in the analysis of boiling phenomena are within reach through the systematic use of multi-phase Computational Fluid Dynamics (CFD), specifically Interface Tracking Methods (ITM). With such methods the geometry of the vapor-liquid interface is not assumed (e.g., bullet-shaped bubbles), but actually calculated from ‘first principles.’
Moreover, CFD can resolve (through Direct Numerical Simulation or Large Eddies Simulation) the velocity and temperature gradients near the interface, so prediction of the exchange of momentum and heat at the interface requires no empirical closure relations. The key issue is the availability of high-quality experimental data to validate the CFD codes. My lab has state-of-the art capabilities, i.e., infra-red thermometry, high-speed imaging and optical probe, that have been used to obtain detailed and fundamental time- and space-resolved data on pool boiling heat transfer, specifically bubble departure diameter and frequency, growth and wait times, nucleation site density and near-wall void fraction. If successful, the application of ITMs to the complex two-phase phenomena encountered in the core and other major components of nuclear reactors may result in significantly improved accuracy in the predictions of the reactor behavior. Elimination of unnecessary conservatism in the analysis could lead to power uprates and/or safety margin enhancement.
Recent experiments have revealed that nano-engineered surfaces can enhance boiling heat transfer dramatically. However, the role of nano-scale structures in boiling heat transfer is not at all understood, since according to the traditional theory of boiling, it is the liquid-vapor-solid interactions at the micro-scale that dominate bubble nucleation and boiling heat transfer. Using custom-fabricated nano-patterned surfaces, studied with the high-speed infrared imaging technique and molecular dynamic simulations, we are probing the fundamental mechanisms of boiling heat transfer at the nanoscale.