Experimental analysis of convective boiling heat transfer and nanoparticle deposition effect of TiO2-H2O nanofluids in microchannels

The convective boiling heat transfer characteristics of TiO2-H2O nanofluids in microchannels were experimentally investigated in this paper. The effects of the mass flow rate, mass fraction and nanoparticle size on the average flow boiling heat transfer coefficient were examined at heat fluxes of 138.4-220.5 kW/m2. The results have shown that the average flow boiling heat transfer coefficient of TiO2-H2O nanofluids increases with the increase of the mass flow rate and nanoparticle size. When the mass fraction of TiO2-H2O nanofluids ranges from 0.01 % to 0.1 %, the maximum heat transfer efficiency has reached with the mass fraction of 0.025 %. Considering the movement and deposition of the TiO2 nanoparticles in the convective boiling process, the difference of the absorbance value of TiO2-H2O nanofluids and heating surface morphology after boiling were observed. It proved that the distribution density of the nanoparticle deposition gradually increases along the flow direction of the microchannel. Furthermore, the mass fraction of TiO2-H2O has great influence on the nanoparticles deposition morphology and the nucleation condition of the boiling surface.