Owing to the recent advances in nanotechnology, one significant progress in energy technology is increased cooling ability. It has recently been shown that nanowires can improve pool boiling heat transfer due to the unique features such as enhanced wetting and enlarged nucleation sites. Applying such nanowires on a flow boiling, which is another major class of boiling phenomenon that is associated with forced convection, is yet immature and scarce despite its importance in various applications such as liquid cooling of energy, electronics and refrigeration systems. Here, we investigate flow boiling heat transfer on surfaces that are coated with SiNWs (silicon nanowires). Also, we use highly-wetting dielectric liquid, FC-72, as a working fluid. An interesting wetting behavior is observed where the presence of SiNWs reduces wetting and wicking that in turn leads to significant decrease of CHF (critical heat flux) compared to the plain surface, which opposes the current consensus. Also, the effects of nanowire length and Reynolds number on the boiling heat transfer are shown to be highly nonmonotonic. We attempt to explain such an unusual behavior on the basis of wetting, nucleation and forced convection, and we show that such factors are highly coupled in a way that lead to unusual behavior.
Bibliographical noteFunding Information:
The authors thank H. A. Stone for valuable comments and discussions. This work was supported by the National Research Foundation of Korea (NRF) under a grant funded by the Korea government (MEST) (No. 2011-0017673 ) and the Human Resources Development program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) under a grant funded by the Korea government Ministry of Trade, Industry and Energy (No. 20144030200560 ). S. Shin acknowledges the NRF for supporting through the Basic Science Research Program (No. 2013R1A6A3A03020179 ).
All Science Journal Classification (ASJC) codes
- Civil and Structural Engineering
- Building and Construction
- Mechanical Engineering
- Industrial and Manufacturing Engineering
- Electrical and Electronic Engineering