Advanced diagnostics to resolve long-lasting controversies in boiling heat transfer

Abstract

Boiling heat transfer has been investigated for several decades, but still there are many open questions and controversies about the mechanisms associated with this process and particularly its limit, known as critical heat flux (CHF). This lack of understanding often arose from the absence of experimental capabilities to perform measurements at the space and time scales characteristic of these phenomena. However, improvements have been possible in the last decade thanks to the rapid development of InfraRed (IR) thermometry diagnostics to measure temperature distributions on the boiling surface [1-13]. In this work, we discuss first-of-a-kind investigations enabled by advanced IR diagnostics developed in the Nuclear Science and Engineering (NSE) department at the Massachusetts Institute of Technology (MIT). Specifically, a new technique has been developed [14], requiring the solution of a couple conduction/radiation inverse problem, to measure temperature and heat flux distributions on the boiling surface with a space resolution of approximately 100 μm, and frame rates from 2500 to 4000 fps. This technique is being leveraged to shed light on many phenomena still debated within the boiling heat transfer community. The list of controversial issues addressed in this talk includes but is not limited to: CHF in steady-state [15] and transient conditions, such as power escalations; onset of nucleate boiling (ONB) temperature in steady-state and transient conditions [16,17]; and CHF enhancement on micro- and nano- engineered surfaces. Here, a specific controversy is addressed, about the partition of the wall heat flux in flow boiling heat transfer.