Role of bubble growth dynamics on microscale heat transfer events in microchannel flow boiling process

Abstract

For nearly two decades, the microchannel flow boiling heat transfer process has been the subject of numerous studies. A plethora of experimental studies have been conducted to decipher the underlying physics of the process, and different hypotheses have been presented to describe its microscopic details. Despite these efforts, the underlying assumptions of the existing hypothesis have remained largely unexamined. Here, using data at the microscopic level provided by a unique measurement approach, we deconstruct the boiling heat transfer process into a set of basic mechanisms and explain their role in the overall surface heat transfer. We then show how this knowledge allows to relate the bubble growth and flow dynamics to the surface heat flux.

Simulations of microlayer formation in nucleate boiling

“…with µ l the liquid viscosity and σ the surface tension coefficient. As the bubble grows outside of the cavity, Ca can be large enough to impede liquid motion at the wall and trap a thin liquid layer underneath the bubble: the liquid microlayer -see experimental evidence by Moore & Mesler (1961), Hendricks & Sharp (1964), Hospeti & Mesler (1965), Jawurek (1969), Foltz & Mesler (1970), Judd (1975), Judd & Hwang (1976), Koffman & Plesset (1983), Moghaddam & Kiger (2009), Golobic et al (2009), Kim & Buongiorno (2011), Gao et al (2013), Jung & Kim (2014), Jung & Kim (2015), Bigham & Moghaddam (2015), Yabuki & Nakabeppu (2014), Yabuki & Nakabeppu (2016), and Zou et al (2016a). Once the bubble has reached a certain size, referred to as departure diameter, the bubble departs from its initial position at the heated wall and additional cooling mechanisms can occur.…”

Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling

“…This has been discussed in details in authors’ prior studies1213. The thermal events associated with the vapor slug flow are the thin film evaporation and the surface partial dryout processes.…”

Can the heat transfer coefficients for single-phase flow and for convective flow boiling be equivalent?

“…This quest for unveiling the physics of the process has recently pushed the research towards the study of heat transfer at high spatial and temporal resolutions. 4 The complexity and challenge for predicting the heat transfer during convective flow boiling contrast with the simplicity of the single-phase heat transfer coefficient in pipes. The equation attributed to that proposed by Dittus-Boelter and McAdams, 5 following the equation proposed by Nusselt in 1910 (as cited in Ref.…”