Pool Boiling Characteristics of Carbon Nanotube Based Nanofluids Over a Horizontal Tube

Abstract

This paper is mainly concerned about the pool boiling heat transfer behavior of multiwalled carbon nanotube (CNT) suspensions in water and water containing 9.0% by weight of sodium lauryl sulfate anionic surfactant (SDS) has been carried out. Three different concentrations of 0.25%, 0.5%, and 1.0% by volume of CNT in base fluids, i.e., water and water containing 9.0% by weight of sodium lauryl SDS, were prepared and boiling experiments were conducted over a 115 mm long stainless steel horizontal tube heater of 9.0 mm outer diameter and 0.5 mm thickness. The test results show that the addition of carbon nanotubes increases the boiling heat transfer coefficient of base fluids. The enhancement of heat transfer coefficient was found at 1.75, 1.2, and 1.2 folds corresponding to 0.25%, 0.5%, and 1.0% concentration of CNT by volume in water at the critical heat flux of 961 kW/m2, 611 kW/m2, and 508 kW/m2, respectively. It was also observed that the enhancement factor was higher for lower heat fluxes, which decrease for higher heat fluxes. And also, the heat transfer coefficient enhancement in the water-CNT-surfactant nanofluids of 0.25%, 0.5%, and 1.0% of CNT concentrations are found to be 1.13, 1.44, and 1.5 times that of water at the critical heat fluxes of 295 kW/m2, 231 kW/m2, and 213 kW/m2, respectively. Foaming was found over the free surface of all water-CNT-surfactant nanofluids during the boiling experiments. Furthermore, it was observed that there was no fouling over the test-section. For further confirmation, however, a long term study needs to be carried out.