Influence of nanoparticles on boiling heat transfer

Two sets of experiments are performed in this work to reveal the potential effect of nanoparticles on boiling heat transfer: i) pool boiling of nanofluids on two well-defined boiling surfaces and ii) bubble formation in a quiescent pool of nanofluids under adiabatic conditions. Different to the conventional thoughts that the modification of boiling heat transfer is the result of solid surface modification by particle sedimentations forming a porous or coating layer, the result suggests that both the particle deposition effect, and the collective effect of particles suspending in liquid could affect the boiling heat transfer significantly. The particle deposition effect is influenced by the relative size between particles suspended in the liquid medium and the surface geometry, and their interactions. Nanoparticles suspended in the liquid alone can affect bubble formation significantly by modifying bubble dynamics such as bubble departure volume and departure frequency. Both roles are likely co-existent in a typical nanofluids boiling system. Depending on different applications, properly surface engineering could minimize the particle deposition effect yet still contribute to the modification of heat transfer through the second mechanism.

► Two experiments are performed to reveal the effect of nanoparticles on boiling. ► Well characterisation of boiling surface shows the importance of particle deposition. ► Single adiabatic bubble growth reveals the unique role of nanoparticles in the liquid. ► Both roles should be considered in a nanofluid boiling system.