Experimental investigation on heat transfer characteristic of TiO2-H2O nanofluid in microchannel for thermal energy storage

In order to enhance the heat transfer performance of phase change material (PCM) for thermal energy storage (TES) in tiny devices, such as battery thermal management, light-emitting diode and electronic device cooling, TiO2-H2O nanofluids and the microchannel were combined in this paper. Two crystal forms of TiO2-H2O nanofluids were prepared by using a two-step method. And paraffin was used as PCM. The stability and thermophysical properties of the above two nanofluids were tested and compared. It can be found that R TiO2-H2O nanofluid has better stability, and its thermal conductivity increases maximally by 3.27%, while the value is 2.88% of A TiO2-H2O. Besides, R TiO2-H2O nanofluid increases the viscosity by a maximum of 4.87%, while A TiO2-H2O increases by 7.45%. Considering these properties, R TiO2-H2O nanofluid was chosen to study the heat transfer characteristics in the microchannel within a TES unit. The results indicate that R TiO2-H2O nanofluid with 1.0 wt% increases Nu by 19 similar to 41% and 6 similar to 14% during the melting process and solidification process respectively. In addition, the melting time of paraffin decreases by a maximum of 32.90% and the solidifying time of paraffin decreases by a maximum of 22.57%. During the whole TES process, there is an increase in pressure drop of no more than 8%.