engleski

Cooling characteristics of the water based nanofluids in quenching

Nanofluids are the new quenching media with colloidal suspensions of nanoparticles in base fluids, offering new possibilities for enhancement of the heat transfer characteristics. The recent investigations show that the addition of the metals oxides particles, such as CuO, Al2O3 and TiO2, or graphite particles result in better cooling abilities and higher impact toughness and smaller dimension changes of steels, compared with the traditionally used quenching media. This paper presents the preliminary results of the investigation of cooling characteristics of water and 30 % Polyalkylene Glycol (PAG) particle water solution based fluids. The investigated fluids were prepared by the addition of Al2O3 and TiO2 powders with different particle sizes - from less than 50 nm to 100 μm and concentrations between 0.1 and 0.4 %wt. The cooling curve measurements have been conducted by IVF smart quench system using stainless steel probe with 12.5 mm diameter. Derived from these data, the cooling rate vs. temperature and the heat transfer coefficients have been determined using the IVF’s SQintegra software. Alumina particles suspended in water based polymer solution caused shortening of the full film phase. Smaller size particles exhibit greater effect on the start of nucleate boiling phase than solutions with larger particles or without any. This results in shorter quenching process even though the maximum cooling rate is similar for all the media. At lower concentrations of TiO2 nanoparticles dispersed in water there is no significant difference between cooling curves for deionized water and TiO2 nanofluid.

nanofluid; quenching; heat transfer coefficient

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