Thermal Properties of Composites Containing Metal Oxide Nanoparticles

We prepared a series of paraffin wax (PW) based phase change composite containing ZnO, Al2O3 and Fe2O3 nanoparticles, respectively. DSC results showed that there is a decrease trend in phase change latent heat capacity (Ls) with an increase of metal oxide nanoparticle loadings. ZnO/PW has higher Ls than those of Fe2O3/PW and Al2O3/PW with same metal oxide nanoparticle loadings. Transient short-hot-wire (SHW) method was used to measure thermal conductivity of these composites. The results showed that nanoparticle addition leads to substantial enhancement in the thermal conductivity of the composites. The highest thermal conductivity of the measured composites is about 0.27 W/(m•K) of Fe2O3/PW with 3.0 wt% nanoparticles and Al2O3/PW with 5.0 wt% nanoparticles at 15 oC, which higher than that of PW by about 30%. The lowest thermal conductivity of composites is that of Al2O3/PW and ZnO/PW with 1.0 wt% nanoparticles at 60 oC, which higher than that of PW by about 7%.

Thermal Conductivity Measurement of Hydrogen at High Pressure and High Temperature

The thermal conductivities and thermal diffusivities of hydrogen were measured with a transient short hot wire method for temperature range up to 300 °C and pressure range up to 100MPa. The measured thermal conductivities showed good reproducibility and agreed with the existing values within a deviation of ±2%.

Measurement of Effective Thermal Conductivity of CNT-Nanofluids by Transient Short-Wire Method

Thermal conductivity and thermal diffusivity of CNT-nanofluids and Al2O3-nanofulids were measured by the transient short-hot-wire method. The uncertainty of their measurements is estimated to be within 1% for the thermal conductivity and 5% for the thermal diffusivity. Three different shapes of Al2O3 particles were prepared for Al2O3–water nanofluids. For the thermal conductivity of Al2O3-water nanofluids, there are differences in the enhancement of thermal conductivity for differences in particle shapes. Hardly any enhancement of thermal conductivity was observed for SWCNT-water nanofluids because the volume fraction of SWCNT was extremely low. However, we consider by increasing the volume fraction of SWCNTs, it will be possible to enhance the thermal conductivity.