A review on thermal performance of CuO-water nanofluids applied to heat pipes and their characteristics

Nanofluids are basically made of a base fluid and a volume fraction of dispersed nanoparticles. In order to consider any fluid as a nanofluid, it must contain particle sizes within the range from 1nm up to 100nm. Nanofluids studies and analysis have been both increasing during the last years due to the fact they are able to provide great thermal conductivity enhancements compared to the base fluid alone. One of the most commonly used nanofluids are made of water as base fluid and oxides as nanoparticles. The CuO-water nanofluid is one of these oxide nanofluids also called as ceramic or non-metallic nanofluids, which is under studies for some different volume fractions (vol.%) and particle sizes. The CuO-water nanofluids are relatively easy to be prepared by using the two-steps method, which provides a reasonable stability and particle dispersion. The nanofluid stability and particle dispersion are both important parameters for having thermal conductivity enhancements. Heat pipes are thermal devices able to efficiently transport great amount of heat for long distances through a saturated working fluid by using capillary pressure generated in an internal wick structure. Thus, the application of nanofluids in heat pipes has been one of interesting researches lately. Considering that nanofluids applied in heat pipes may bring alternatives for thermal conductivity enhancements for aerospace and also other industry fields, this paper specifically considers a review on some CuO-water nanofluid papers. The objective is to evaluate correlations between some results from thermal performances standpoint and also their main characteristics which may affect thermal conductivity enhancements.