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A study on bubble growth mechanisms and underlying physical phenomena of flow boiling in silicon nanowire (SiNW) microchannels has been performed and compared these results with plainwall microchannels. A new approach in studying bubble dynamics and forces acting on liquid–vapor (L–V) interface of growing bubble has been proposed based on theoretical, experimental and visual studies. Bubble size, liquid film thickness, interfacial properties are measured and L–V interfaces are detected from high speed visualization data and results are analyzed by vision-based approach. Force analysis during instantaneous bubble growth from bubble nucleation to formation of annular flow regime has been performed for both the SiNW and plainwall microchannel configurations. Results from force analysis show the dominance of surface tension at L–V interface of growing bubble which resulted higher heat transfer contact area, lower thermal resistance and higher thin film evaporation. Whereas, inertia force is dominant at L–V interface of fully grown bubble and it helps in bubble removal process and rewetting before flow reversal. Significant differences between SiNW and plainwall microchannels have been observed in bubble growth mechanism, heat transfer mode and forces acting on L–V interface. [ABSTRACT FROM AUTHOR]

• Bubble dynamics in one single confined microchannel was experimentally investigated. • The effects of hydraulic diameter (D h) of channel, flow rate and heat flux on bubble dynamics are discussed. • The velocity and acceleration of L- V interface were estimated through the analysis of recorded videos using vision-based technique. • The interfacial heat transfer (Nu c) changes with re b during bubble growth and bubble shrinking. • An analysis of energy distributions by bubble dynamics is conducted, heat flux through interface counts over 96% of total input power. Bubble dynamics are fundamental to understand boiling heat transfer mechanism at microscale. In this study, bubble dynamics in one single confined microchannel was experimentally investigated through vision-assisted technique. Experimental studies were performed to understand the effects of hydraulic diameter (D h) of channel, flow rate and heat flux on bubble dynamics, which highly affect the boiling heat transfer performance. First of all, experimental results show that D h has a vital effect on the volume change rate of confined bubble, which can be used to compute the heat flux transported by single bubble. The liquid-vapor (L- V) interfaces were tracked by non-rigid image registration and the velocity and acceleration of L- V interface were estimated through the analysis of recorded videos using vision-based technique. To quantitatively evaluate the impact of bubble dynamics, transient heat transfer rates were presented at different flow rates. Furthermore, the interfacial heat transfer (Nu c) influenced by bubble dynamics was evaluated. Nu c changes with Re b during bubble growth and bubble shrinking. Finally, an analysis of energy distributions by bubble dynamics is conducted. Compared to energy transported by bubble and kinetic energy of bubble, heat flux through interface is significant, dissipating over 96% of total input power. [ABSTRACT FROM AUTHOR]