Experimental study of natural convection from vertical cylinders with branched pin fins

•Vertical cylinders with branched pin fins are experimentally investigated.•Branched pin fins exhibit reduced thermal resistance compared to plate fins.•The maximum reduction in thermal resistance is approximately 20%.•A correlation for predicting the Nusselt number is proposed. In this study, the natural convection heat transfer phenomena from vertical cylinders with branched pin fins are experimentally investigated. Experiments are conducted to measure the heat transfer rates from finned cylinders to the surrounding air at various cylinder wall temperatures, fin pitch angles, and fin heights. The experimental results indicate that the thermal resistance of vertical cylinders with branched pin fins is 20% smaller than that of conventional vertical cylinders with plate fins. The thermal resistance per unit fin volume of the former is 40% smaller than that of conventional finned cylinders. Moreover, a correlation for the Nusselt number is obtained from the calculated thermal resistance values. The error between the predictions from the correlation and experimental results is less than 20%. In addition, the effects of fin length and fin pitch angle on the thermal resistance are investigated using the proposed correlation.