Specific heat measurements of CNT nanofluids

Abstract

There have been numerous research studies regarding nanofluid for last two decades. The major topic was mostly focused on the thermal conductivity increase with small particle concentration. However, a conclusion regarding thermal conductivity increase and heat transfer mechanism was not achieved yet due to large discrepancies among the experimental results. In parallel with the thermal conductivity, the specific heat is a crucial thermal property in the application of the nanofluid but wide research has not been conducted. In this study, the specific heat of carbon nanotube (CNT) nanofluids were experimentally measured and the experimental results were compared with possible models to explain the results. The CNT nanofluids were produced with DI water and ethylene glycol (EG) as base fluids. Since CNTs are not mixed with DI water, gum Arabic was used as a surfactant. On the other hand, CNTs were mixed with EG without any surfactant. The specific heat was measured with Calvet calorimeter. Temperature and heat flow sensors of Calvet calorimeter were calibrated with reference materials. The experiment method was validated by comparing the base fluids with reference values showing very good agreement. The measured specific heat of CNT nanofluids decreased with particle concentration due to the lower specific heat of CNT than that of base fluids. It is found that the thermal equilibrium model of nanofluid specific heat successfully predicts the experimental results. This result can be very useful in generating desired working fluids in the diverse thermal systems because the control of the specific heat of nanofluid can be achieved.