Experimental and numerical investigation of natural convection heat transfer of semicircular-finned radial heat sink at various

The effect of fin shapes in heat sinks under free convection was investigated both numerically and experimentally. The thermofluid characteristics of semicircular fin heat sinks were analyzed using three-dimensional numerical simulations. Parametric studies were conducted to examine the effects of geometrical parameters, particularly orientation angles (0°, 15°, and 30°) and input heat rates. A structured, non-uniform computational mesh was employed, and numerical simulations were performed using ANSYS Fluent 2021R2, based on the Finite Volume Method (FVM). A 210-mm diameter semicircular fin was used in the CFD simulations. Experimentally, three heat sink models (SC-0, SC-40, and SC-50) were compared to identify the optimal reference model. The study investigated the impact of fin shape, fin number, and heat flow on thermal resistance and the overall heat transfer coefficient. The parametric study applied a design of experiments (DOE) approach, including the design and execution of 18 experiments, empirical model analysis, and factor optimization. Optimization followed a general factorial design (GFD) framework, where factor ranges were coded between +1 and -1, with adjustments for unit variability across independent variables. Using GFD, regression analysis was applied to derive a new model, incorporating Nusselt number and thermal resistance. Experimental data from the literature on semicircular radial fins under natural convection were included. Key determinants for the best transfer function were R², adjusted R², predicted R², coefficient of variation (C.V.), and parameter proximity to optimal values. Results showed that airflow velocity was higher at a 0° orientation angle. However, airflow parallel to the fins at this angle caused minimal obstruction, resulting in a heat transfer coefficient 3.9% to 7.3% lower than those at 15° and 30°, respectively. The Nusselt number was highest at the 30° orientation. Experimentally, the heat transfer coefficient increased by up to 30% between SC-0 and SC-40, and 27% between SC-0 and SC-50, while thermal resistance was 17% lower for SC-40 and 19% lower for SC-50 compared to SC. A larger number of fins enhanced heat dissipation under natural convection. CFD simulation results closely matched experimental data, with temperature differences within ±4.9%, indicating strong qualitative agreement. DOE results revealed the best performance for the Nusselt number with R² (98.15%), predicted R² (97.08%), adjusted R² (94.87%), and C.V. (2.44%). For thermal resistance, the corresponding values were R² (97.91%), predicted R² (96.70%), adjusted R² (94.21%), and C.V. (3.33%). These findings demonstrate that the proposed model accurately predicts the performance of semicircular radial heat sinks and holds promise for future designs.