Effect of nanoparticle concentration and surfactants on nanofluid pool boiling

Silica nanofluids are prepared with a concentration varying from 0.001 vol.% to 0.003 vol.%, and pool boiling of the nanofluids is experimentally investigated. It is found that critical heat flux and heat transfer coefficient increase by a maximum of 62.66% and 45.88% compared with deionized water. The best boiling performance is achieved with the nanofluid of 0.002 vol.%. In addition, the paper further investigated the effect of surfactants on nanofluid boiling, i.e., cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polysorbate 20 (Tween 20). The heat transfer coefficients of the nanofluids with CATB and with SDS increase by 55.45% and 9.73% compared to the nanofluid without surfactant. However, the heat transfer coefficient of the nanofluid with Tween 20 is lower than that of the nanofluid without surfactant. Finally, surface characterizations and bubble dynamics are carried out to reveal the mechanism of nanofluid boiling enhancement, as well as the effect of surfactants on nanofluid boiling. The results show that nanoparticles deposited on the surface during boiling, which increases surface roughness and reduces surface contact angles, promoting bubble nucleation and departure as well as liquid supply.