Fractal Induced Turbulence and Its Effects on Plate-Fin Heat Sink Heat Transfer

Low, Han Liang (2022) Fractal Induced Turbulence and Its Effects on Plate-Fin Heat Sink Heat Transfer. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Heating, ventilation and air conditioning (HVAC) consumes high amount of electric energy, and the energy consumption can be reduced by increasing the efficiency of heat exchanger in HVAC. Fractal grid, a good passive flow control device, is used to increase the thermal efficiency of the heat exchanger by generating turbulent flow across the heat sink. In this research, the effects of fractal thickness ratio TR, streamwise thickness SWT, and inlet velocity on plate-fin heat sink thermal dissipation are explored. The fractal grid with TR15 and SWT20 which has the highest blockage ratio contributes to the highest Nusselt number as compared to TR 5 and TR 10. Besides, the higher the inlet velocity, the greater the Nusselt number, but with a higher pressure drop. Besides, with the same blockage ratio and inlet velocity, the fractal grid conducts 6.43% higher in Nusselt number and 19.38% in pressure drop than the regular grid. This is because there are more and stronger wake interations created by the fractal grid. Even though fractal grid results in a higher pressure drop, but the 4Pa increment in pressure drop is considered insignificant in the HVAC industry. By observing the velocity profile and turbulence intensity in ANSYS simulator, it is discovered that plate fins with greater turbulence intensity and velocity coverage contribute to greater thermal dissipation and higher Nusselt number. Furthermore, the streamwise thickness of fractal grid, SWT does not affect Nusselt number and pressure drop in this study.