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چکیده
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Cooling nuclear power plants and ensuring effective heat transfer from the fuel rods to the heat transfer fluid are essential to ensure the optimal and safe operation of the power plant. After effectively absorbing heat from the reactor core, the fluid travels to the turbine and drives it to generate electrical energy. One of the new ideas for increasing heat transfer, especially in heat exchangers, is the use of porous materials, especially metal foams. These materials are of interest to thermal engineers as an effective method for improving heat transfer rates due to their important properties, such as high thermal conductivity, good strength, ability to intermix flow, and consequently eliminate the thermal boundary layer, and increasing the contact surface for heat transfer. In this study, using an experimental method and designing a setup, the effect of using metal foam tubes on the heat transfer coefficient of subcooled boiling of water and nanofluids of CuO/H2O and Al2O3/H2O has been investigated. For this purpose, the test section is a steel tube filled with an open-cell copper metal material. The porosity of the metal foam is 80% and its pore density is 5 PPI. The rig consists of a fluid storage tank, a preheater, a magnetic stirrer, a centrifugal pump, a turbine flow meter, two pressure gauges, thermocouples, and a condenser. Experimental results comparing the test section with a plain tube showed that the metal foam tube delayed the onset of nucleate boiling. The results also indicated that the metal foam improved heat transfer by 3.5-5.8 times. Also, in the comparison between water and nanofluids, the results showed that the deposition of nanoparticles weakened the heat transfer, and therefore, the use of water was more appropriate. Key operational parameters influencing subcooled flow boiling, including inlet subcooling temperature, mass flux, heat flux, and nanoparticle concentration, were systematically examined. Based on the analysis of the experimental data and considering the significant operational variables, an empirical correlation was developed to predict the Nusselt number for flow boiling within metal foam tubes.
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