Author(s): Kays A Al-Tae’y

Abstract: The natural convection heat transfer system in nuclear reactor systems may be subject to several external sources such as vibration. Thus, the natural convection due to buoyant force results from the interaction of density gradients with the acceleration field. In the present study, the numerical investigation of periodic oscillation thermal natural convection of a liquid metal gallium inside the internally uniform heated square enclosure. The enclosure is subjected to a sinusoidal oscillation vibration at low frequency. A time dependent governing equations were solved using a finite volume method based on a pressure-correction equation of the unsteady SIMPLE algorithm technique, and a collocated arrangement for scalar and vector variables in a non-uniform grid system. The top and bottom walls of the two-dimensional enclosure were isolated, whereas the side walls were isothermal cooled. The numerical simulations were performed on two case problems: uniform vibration amplitude at a constant frequency, and nonuniform vibration amplitude at a constant frequency. The results obtained for the internal Rayleigh number were 106. The results show that when the uniform vibration amplitude was increased from 0.01 mm to 100 mm at a frequency value equal to 1 Hz the natural periodic oscillation flow transitioned to a quasi-periodic flow. When uniform vibration amplitude values at 0.01 mm and 1.0 mm with frequency value 1 Hz, the time series at a certain time value appeared a sudden fall in counterclockwise streamfunction value and an unanticipated jump in clockwise streamfunction value. The result also indicates a rapid change in counterclockwise and clockwise streamfunctions values when the nonuniform vibration was applied with two different amplitude values ​​in a sequential pattern at a certain frequency value. Therefore, the vibrations distort the original velocity and temperature field for oscillation thermal natural convection and new distributions appear, even at low vibration frequency and amplitude. The results showed that the heat transfer rate of thermal flow in the enclosure is proportional to vibration frequency and amplitude.

DOI: 10.22271/27078043.2025.v6.i1a.77

Pages: 53-73 | Views: 794 | Downloads: 214

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