Flow boiling instabilities in microchannels and their promising solutions - A review

- A comprehensive review of literatures on flow boiling instabilities in microchannels.
- Overview of instabilities, their causes, and its suppression methods have been discussed.
- Influence of several factors on instabilities such as bubble dynamics, parallel channel interaction etc.
- Prominent techniques to suppress flow boiling instabilities have been thoroughly explained.

The present work has been undertaken with an aim to address major challenges during two-phase flow boiling in microchannels. A comprehensive review of literatures has been presented that highlights the problems of two-phase flow boiling and its suppression techniques. Emphasis has been given to the recent literatures addressing the issues of flow boiling instabilities in microchannels. The broad aspects that have been covered are overview of instabilities, their causes, consequences and suppression techniques. Major attention has been paid to highlight the promising solutions that have been investigated to mitigate the instabilities. Study revealed that inception of instabilities is inherent during flow boiling. Nevertheless, it is more sensitive to trigger-out in microchannels compare to macro or conventional channels. Researchers have common agreement over the causes of instabilities and their consequences such as pressure and temperature fluctuations, severe unstable flow boiling, flow reversal, early CHF (critical heat flux) and dry out. It has been identified that instabilities during flow boiling depends on mass flow rate, flow regimes, bubble dynamics, inlet subcooling, inlet compressibility and coolant properties. Study also revealed that in the recent year's more attention has been paid to overcome the instability and issue has been addressed simultaneously with heat transfer enhancement studies. In order to suppress the instability various techniques have been investigated however, geometrical modification has been prominently considered to overcome the instability phenomenon.