Understanding bubble dynamics and related heat transfer characteristics in multiple parallel microchannels with and without inlet restrictions*

Flow boiling inside a microchannel heat sinks have been recognized as one of the efficient ways of cooling advanced electronic devices which generate high heat such as micro-electronic chips, micro-electro-mechanical systems (MEMS), and fuel cells. Extensive research has been carried out in the past to understand the bubble dynamics and associated heat transfer characteristics inside a single microchannel using numerical simulations [1,2]. In practical scenarios, however, multiple microchannels arranged in parallel are used for effective cooling. Bubble dynamics in such microchannel heat sinks with multiple parallel channels are considerably different from those in single channels and are relatively poorly understood. In the present work, three-dimensional numerical simulations are performed to understand the bubble dynamics, the interaction between the bubbles nucleating in two different channels, and its effect on wall temperature and heat transfer characteristics. For this purpose, direct numerical simulations are carried out using the volume-of-fluid method with an additional model to handle liquid-vapour phase change. Furthermore, one of the major problems associated with the flow boiling in multiple parallel microchannels is instability in boiling arising due to sudden expansion of vapour bubbles formed in the channels which leads to flow reversal and early critical heat flux. An attempt is made to address this instability by using channels with inlet restrictions in a multiple parallel microchannel setup.

References

 

[1] A. Mukherjee, S.G. Kandlikar. “Numerical simulation of growth of a vapor bubble during flow boiling of water in a microchannel”. Microfluid Nanofluid, 1 (2005), pp. 137–145.

[2] M. Magnini, O.K. Matar. “Numerical study of the impact of the channel shape on microchannel boiling heat transfer”. International Journal of Heat and Mass Transfer, 150 (2020), pp. 119322.