Experimental investigation is carried out to study the thermal performance of a heat sink with finned U-shape heat pipes which is a contemporary central processing unit (CPU) cooler compatible for a wide range of high-frequency microprocessors. The optimum range of operating heat load based on thermal resistance analysis of the heat sink is characterized. The convection heat transfer coefficient between the fins and the ambient air is estimated by using Bessel's modified equation in conjunction with the results obtained through the experimental investigation. The thermal optimization of the heat sink involves the determination of the optimized L-ratio (ratio of the evaporator section length to the condenser section length) of the U-shape heat pipe, by evaluating the minima of the thermal resistance function, in which case the empirical convection heat transfer coefficient is applied in the calculation. In conjunction with this, the optimal L-ratio of a U-shape heat pipe is found to be dependent on other geometrical parameters such as the heat pipe diameter and the fin spacing, which are of practical engineering importance in the optimum design of the heat sink. (C) 2010 Elsevier Ltd. All rights reserved.