A Comparative Study on the Characteristics of the Pure water and Ethanol Carbon Nanofluids for Applying Solar Collector

태양열 집열기 적용을 위한 순수 물과 에탄올 탄소나노유체의 특성 비교 연구

In this study, for increasing the efficiency of solar collector, the thermal conductivities and viscosities of the pure water and ethanol oxidized multi-walled carbon nanofluids were measured. Nanofluids were manufactured by ultra-sonic dispersing oxidized multi-walled carbon nanotubes(OMWCNTs) in the pure-water and ethanol at the rates of 0.0005 ~ 0.1 vol%. the Thermal conductivities and viscosities of manufactured nanofluids were measured at the low temperature($10^{\circ}C$), the room temperature($25^{\circ}C$) and the high temperature($70^{\circ}C$). For measuring thermal conductivity and viscosity, we used Transient Hot-wire Method and Rotational Digital Viscometer, respectively. As a result, under given temperature conditions, thermal conductivity of the 0.1 vol% pure-water nanofluid improved 7.98% ($10^{\circ}C$), 8.34% ($25^{\circ}C$), and 9.14% ($70^{\circ}C$), and its viscosity increased by 37.08% ($10^{\circ}C$), 33.96% ($25^{\circ}C$) and 21.64% ($70^{\circ}C$) than the base fluids. Thermal conductivity of the 0.1 vol% ethanol nanofluids improved 33.72% ($10^{\circ}C$), 33.14% ($25^{\circ}C$), and 32.36% ($70^{\circ}C$), and its viscosity increased by 37.93% ($10^{\circ}C$), 31.92% ($25^{\circ}C$) and 29.42% ($70^{\circ}C$) than the base fluids.