Thermal-Conductivity Enhancement of Microfluids With Ni3(μ3-ppza)4Cl2 Metal String Complex Particles

The thermal conductivity of microfluids comprising Ni-3(mu(3)-ppza)(4)Cl-2 metal string complex (MSC) microparticles in an aqueous glycerol solution was investigated using the transient hot-wire method. A comparative analysis of the thermal-conductivity enhancements of microfluids and nanofluids revealed that the best results were achieved using microparticles of monocrystalline MSCs Ni-3(mu(3)-ppza)(4)Cl-2 as well as Ni-5(mu 5-pppmda)(4)Cl-2 micro-and copper nanoparticles. Compared to the base fluid, the thermal-conductivity enhancements were 72% for Ni-3-water-glycerol, 53% for Cu-water-glycerol, and 47% for Ni-5-water-glycerol. It is shown that the high thermal-conductivity enhancement achieved with Ni-3 microfluids is a result of higher stability in compare with nanofluid due to the lower density of the microparticles and the formation of particle assemblies. Therefore, the formation of hydrogen bonds between the MSC particles (through their organic fragments) and water molecules, takes place. Colloidal structure of Ni-3-microfluids has a significant impact on their thermophysical properties.