Thermophysical properties of water based Cu nanofluid used in special type of coil heat exchanger

The study shows the results of the investigation into thermophysical properties of water based copper nanofluid designed for a special type of coil heat exchanger requiring a specific working liquid. The nanofluid considered, characterized by low particle concentrations, was proposed as this liquid. The exact determination of its properties was the basis for further experimental and numerical examination of the exchanger. One of the exchanger's heating coils was filled with a refrigerant. In order to prevent a possible refrigerant leakage a special buffer layer filled with the water based Cu nanofluid was mounted in the coil. The thermophysical properties of the nanofluid might lead to heat transfer enhancement in the buffer layer and thus improve the thermal characteristics of the exchanger. The density, viscosity and thermal conductivity of the Cu/water nanofluid were measured experimentally. Spherical copper nanoparticles of about 40 nm in diameter were suspended in distilled water to produce test nanofluids. Three nanoparticle volume concentrations: 0.011%, 0.055% and 0.101% were examined. The dependencies associated with density, dynamic viscosity and thermal conductivity on temperature and particle volume concentration were determined. The experimental results obtained were compared with those which were calculated based on theoretical models. It was found that there was no compatibility of the measurements results with theoretical data in the case of viscosity and thermal conductivity. An attempt to explain this discrepancy was made.