Document Type : Article
Authors
1
Islamic Azad University ،Science And Research Branch
2
Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
3
Department of Mechanical Engineering,/Faculty of Mechanics, Electricity and Computer (Islamic Azad University of Science and Research), Tehran , Iran
Abstract
In recent decades, considerable efforts have been made by thermal fluid specialists to investigate the boiling heat transfer process. Pool boiling of pure liquids and nanofluids has been widely studied in the last decade, but the existing knowledge on modeling of nanofluids pool boiling process is still limited. The boiling of fluids containing tinny solid particles is very complicated due to the interaction between the existing phases, their interface and the heating surface Some new research shows that many factors are effective in pool boiling of nanofluids. Among these factors, we can mention particle size, concentration, the structure of the boiling surface, and the dynamics of bubbles. In this research, the film pool boiling process of pure ethanol was numerically simulated. Then, the film pool boiling of nanofluids including two types of nanoparticles 〖Al〗_2 O_3, SiO_2 and ethanol base fluid with two volumetric concentrations of 0.1% and 0.3% have been simulated. The results show that in film boiling, the presence of nanoparticles in the base fluid has increased the heat transfer coefficient. The highest value coefficient for alumina and silica nanofluids with a volumetric concentration of 0.3% was obtained, respectively 0.32 (kW/m2°C) and 0.3 (kW/m2°C). In addition, the presence of nanoparticles in the boiling process has significantly increased the minimum heat flux. According to the results of numerical simulation, the minimum heat flux value in boiling of pure ethanol is 28.99 (kW/m2), in boiling of alumina-ethanol nanofluid with volumetric concentrations of 0.1% and 0.3%, is 37.11 (kW/m2) and 38.84 (kW/m2), respectively and in boiling of silica-ethanol nanofluid with volumetric concentrations of 0.1% and 0.3%, is 35.81 (kW/m2) and 38.31 (kW/m2), respectively. The highest heat transfer coefficient is achieved by alumina nanofluid with 0.3% concentration, while the highest minimum heat flux is achieved by silica nanofluid with 0.3% concentration. The numerical results are in good agreement with the experimental results. By comparing these values with the experimental results, there is a good consistency between the results.
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