Freeze-Thaw Characteristics of Water-Based Copper Oxide Nanofluid

Abstract

This research examined the freeze-thaw characteristics of a water-based copper oxide (CuO) nanofluid for its successful application in cold regions, where freezing of heat transfer fluids can occur. The enhanced thermal conductivity (k) of nanofluid makes it valuable as a heat transfer fluid, but k diminishes as the average particle size (APS) of the dispersed nanoparticles grows. Therefore, experiments were conducted to determine the effect of freezing on the APS of nanofluid suspensions due to agglomeration. Additionally, it was studied, if the freezing point of the nanofluid was elevated or depressed as the volumetric concentration of nanoparticles in the suspension was increased from 1 % to 5%. Another objective of this experimental study was to compare the time required for precooling, freezing and subcooling of different concentrations of nanofluids and the base fluid. The results showed that the APS grew by as much as 51.2% larger due to the phenomenon of freezing, which would reduce the heat transfer performance. The addition of nanoparticles did not affect the freezing point of the nanofluids, tested for two particle volumetric concentrations of 1 and 5 %. It was observed that the precooling time of 5% CuO concentration was the longest. For the complete solidification process, the water and 1% CuO had comparable freezing times, while the 5% nanofluid had the shortest freezing time. The subcooling time was increased with particle volumetric concentration.