Pool boiling heat transfer on deformable structures made of shape-memory-alloys

More and more fixed geometry structures are being manufactured to enhance the boiling heat transfer (BHT). However, they usually perform well at a special heat load and don't always have good BHT properties. Applying shape memory alloy (SMA) material to change the geometry is a new solution to achieve optimal effect at different boiling condition. Pool boiling heat transfer on deformable structures made of SMA in three fluids (ethanol, FC-72, water) with different thermal properties was explored. Comparing heat flux versus wall superheat and heat transfer coefficient (HTC) at different fluxes with fixed geometry, it was found that deformable structure combines the merits of closed-tunnel and open-tunnel. At low heat fluxes, it can increase the number of nucleation sites inside the closed tunnels with bent fins and after reverting to the original shape, the nucleation sites are activated and the bubble growth and departure is accelerated to enhance the HTC significantly. So by choosing the appropriate time and opportunity for different fluids to open the tunnels, the deformable structures can be used to achieve adaptive-control of boiling heat transfer. In terms of theoretical analysis, the existing correlations for fixed structures have not been fit for deformable structures, because large-scale deformation make the heat transfer mechanism different from the fixed geometry structure. Thus experimental results are compared with fitting curves and a new correlation was deduced.