Quenching characteristics of metallic vertical rod with an internal heater has been investigated in pure water and water-based nanofluid with alumina nanoparticles of 0.001% by volume. Initial temperature of the testing rod (12 mm diameter and 10 0 0 mm length) ranges from 200 °C to 250 °C. The internal heater may be used to simulate the decay heat generated by the nuclear fuel rod after the power plant shut- down. Tests have been performed with varied range of experimental conditions of decay heat, constant water and nanofluid flow rates. The cooling curves follow a general trend of a rapid temperature drop up to almost 100 °C of the rod surface temperature irrespective of the operating parameters and the location of the thermocouple. The obtained results during quenching process indicated that HTC (heat transfer coefficient) for nanofluids are more than de-ionized water. It was also observed that in identical circum- stances, the quenching time of the specimen in Al 2 O 3 nanofluid considerably decreased as compared to water. The results exhibit that nanofluids can enhance the reflood heat transfer performance in terms of quenching rate for a long vertical rod causing liquid-droplets-induced depositions of nanoparticles result- ing in making a pre-coating effect characterized by higher wettability.
Flow boiling of Al2O3-Water nanofluid has been investigated numerically using the Eulerian multiphase model in ANSYS FLUENT. The physical properties have been computed using the two phase mixture model. In the Eulerian multiphase model, Rensselaer Polytechnic Initiative (RPI) nucleate boiling model has been used for modeling boiling. Axial vapor fraction has been computed in case of flow boiling of water and heat transfer coefficient has been computed in case of flow boiling of Al2O3-Water nanofluid. The numerical results obtained were in good agreement with experimental results. The RPI model predicts the heat transfer characteristics quickly.
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