Investigation on heat transfer characteristics of tapered cylinder pin fin heat sinks Paisarn Naphon * , Anusorn Sookkasem Thermo-Fluid and Heat Transfer Enhancement Laboratory (TFHT), Department of Mechanical Engineering, Faculty of Engineering, Srinakharinwirot University, Ongkharak, Nakhon-Nayok 26120, Thailand Received 8 September 2006; accepted 29 April 2007 Available online 2 July 2007 Abstract In the present study, experimental and numerical results of the heat transfer characteristics of the in line and staggered taper pin fin heat sink under constant heat flux conditions are presented. An experimental apparatus is set up to analyze the problem. The tapered pin fin heat sink is fabricated from square aluminium with length, base and tip diameters of 67, 13 and 7.24 mm, respectively. Experiments are performed at various air Reynolds numbers in the range of 1000–9000 and heat fluxes in the range of 0.91–3.64 kW/m 2 . The number of pin fins for the in line and staggered configurations are 16 and 17, respectively. The k–e standard turbulence model is employed to simulate the turbulent heat transfer characteristics. A finite volume method with an unstructured non-uniform grid system is employed for solving the model. The predicted results are validated by comparing with measured data. The predicted results are in reasonable agreement with the experiments. Ó 2007 Published by Elsevier Ltd. Keywords: Heat transfer characteristics; Heat sinks; Tapered pin fin 1. Introduction In order to maintain a satisfactory temperature level of electronic components with high heat flux level, heat sinks have been extensively employed for cooling enhancement of electronics components. Numerous researchers have studied the heat transfer characteristics of various heat sinks configurations. Haq et al. [1] experimentally investi- gated the steady state forced convective cooling of a hori- zontally based pin fin assembly. Das and Razelos [2] analyzed the heat dissipation and performance of trapezoi- dal pin fins. Yeh [3] analytically investigated the heat trans- fer coefficients and heat transfer from the fin tip, the optimum dimensions of rectangular fins and cylindrical pin fins. Li et al. [4] investigated the heat transfer and flow resistance characteristics in rectangular ducts with stag- gered arrays of short elliptic pin fins. Hwang and Lui [5,6] studied the heat transfer and pressure drop character- istics between pin fin trapezoidal ducts with straight and lateral outlet flows. The effect of pin arrangement for the ducts of different direction outlet flows was also examined. Maveety and Jung [7] studied the heat transfer of the pin heat sink with air impingement cooling. Tahat et al. [8] experimentally and numerically simulated turbulent air impingement flow on a square pin fin heat sink. Experi- ments were conducted using an aluminum heat sink under uniform heat flux. The numerical method incorporates the k–z turbulence model. Sara et al. [9] investigated steady state heat transfers from pin fin arrays for staggered and in line arrangements of the pin fins. Chen et al. [10] pre- sented the heat transfer and friction characteristics and the second law analysis of convective heat transfer through a rectangular channel with square cross section pin fins. Various clearance ratios and inter-fin distance ratios were considered. Willett and Bergies [11] applied the conjugate gradient method to estimate the heat flux of a pin fin. The accuracy of the inverse analysis was examined by using 0196-8904/$ - see front matter Ó 2007 Published by Elsevier Ltd. doi:10.1016/j.enconman.2007.04.020 * Corresponding author. E-mail address: paisarnn@swu.ac.th (P. Naphon). www.elsevier.com/locate/enconman Energy Conversion and Management 48 (2007) 2671–2679