Author(s)

H. Bellerová & M. Pohanka

Abstract

An experimental investigation of spray cooling performed with water based nanofluid containing multi-walled carbon nanotubes and Fe nanoparticles was carried out. The concentrations of carbon nanotubes in the liquid used in the experimental program were 1 wt.%, 0.1 wt.%, 0.01 wt.%, the concentrations of Fe nanoparticles were 40 wt.%, 10 wt.%, 1 wt.%. The liquid was sprayed on the surface by a full cone nozzle from distances of 40, 100 and 160 mm with flow rates of 1 to 2 kg/min (liquid impingement densities of 1 to 40 kg/m2s). A steel sensor measuring temperature history was cooled by spraying from 190 °C. The heat transfer coefficient was calculated at an interval of the surface temperature from 100 °C to 50 °C by inverse modelling, and compared with the heat transfer coefficient of water cooling. Using Fe nanoparticles showed a decrease of the heat transfer coefficient on the cooled surface. The majority of experiments with carbon nanotubes also showed a decrease of the heat transfer coefficient. However, there were some conditions during which an increase was observed. Keywords: nanofluids, multi-walled carbon nanotubes, Fe nanoparticles, heat transfer, spray cooling, experimental. 1 Introduction It was anticipated that some fluid heat qualities would be improved by adding metal parts, metal oxides parts, or generally those parts from materials which have suitable heat transfer characteristics. Some attempts focused on cooling were made by liquid additives in water, with particles sized in mm or μm mixed into the fluids and with nanofluids. Nanofluid is a suspension of fluid (water, ethylene glycol, oil, bio-fluids, polymer solution, etc.) and particles (metals,

Keywords

nanofluids, multi-walled carbon nanotubes, Fe nanoparticles, heat transfer, spray cooling, experimental