Experimental and numerical investigation of surfactant effects on the thermal conductivity of carbon nanotube nanofluids

Dursunkaya, Erdem
Nanofluids are suspensions of nanometer sized particles in base fluids. They have been of great interest in heat transfer applications for their unexpectedly superior thermal properties, especially their thermal conductivity. For almost two decades, scientists have been preparing nanofluids with various base fluids and particles, and have been observing their thermal properties and stability. Despite all the research, nanofluids are yet to achieve widespread use because of incoherent research results, stability issues and cost concerns. Carbon nanotubes as nanofluid ingredients seem to offer the highest thermal conductivity enhancement while being also the most challenging ones in terms the maintenance of stability. This thesis aims to experimentally and numerically investigate the stability and thermal conductivity of carbon nanotube (CNT)-water nanofluids with gum-Arabic as the surfactant. For the experimental part of the study, the transient hot wire and 3-omega methods have been utilized for the thermal conductivity measurements. The stability of the nanofluids have been investigated using sediment photography capturing and scanning electron microscope images. It has been shown that for CNT-in-water nanofluids the use of surfactant is essential for a stable suspension, and that the addition of the surfactant adversely affects the thermal conductivity. For the numerical investigations, Renovated Maxwell and Hamilton Crosser methods have been adapted for the thermal conductivity estimations. The effect of surfactant layer has been included in the mathematical models. The experimental and numerical results have been compared and a reasonable agreement has been demonstrated.
Citation Formats
E. Dursunkaya, “Experimental and numerical investigation of surfactant effects on the thermal conductivity of carbon nanotube nanofluids,” M.S. - Master of Science, Middle East Technical University, 2016.