Background: Hybrid nanofluids are considered as an extension of conventional nanofluids which are prepared through suspending two or more nanoparticles in the base fluids. Previous studies on hybrid nanofluids have measured their thermal conductivity overlooking other thermophysical properties such as viscosity and electrical conductivity.
Objective: An experimental investigation is undertaken to measure thermal conductivity, viscosity, and electrical conductivity of a hybrid nanofluid prepared through dispersing alumina nanoparticles and multiwall carbon nanotubes in salt water. These properties are the main important factors that must be assessed before performance analysis for industrial application.
Method: The experimental data are collected for different values of the nanoparticle volume fraction, temperature, salt concentration, and pH value. Attention is focused to explore the consequences of these parameters on the nanofluid’s properties and to find optimal conditions to achieve the highest value of the thermal conductivity and the lowest values of the electrical conductivity and the viscosity.
Results: The results demonstrate that although the impacts of the pH value and the nanoparticle volume fraction on the nanofluid’s thermophysical properties are not monotonic, optimal conditions for each of the properties is reachable. It is found that the inclusion of the salt in the base fluid may not change the thermal conductivity noticeably. But, considerable reduction in the viscosity and substantial elevation in the electrical conductivity occur with increase in the salt concentration.
Conclusion: With addition of salt to a base fluid, thermophysical properties of a nanofluid can be controlled.