Effect of orientation for phase change material (PCM)-based heat sinks for transient thermal management of electric components ☆ Xiang-Qi Wang, Arun S. Mujumdar ⁎ , Christopher Yap Department of Mechanical Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore, 119260, Singapore Available online 25 April 2007 Abstract Phase change material (PCM)-based heat sink, consisting of a conventional, extruded aluminum sink embedded with appropriate PCMs, can potentially be used for cooling of mobile electronic devices such as personal digital assistants (PDAs) and notebooks which are operated intermittently. During the use of such mobile devices, the orientation changes from time to time. A numerical investigation was carried out to study the effect of orientation of heat sink on the thermal performance of the combined cooling system to determine if it affects the thermal performance of a PCM-based cooling system significantly. © 2007 Elsevier Ltd. All rights reserved. Keywords: Heat sink; Phase change material; Electronic cooling; Orientation 1. Introduction Thermal management is one of the most significant bottlenecks in the development of advanced microprocessors for mobile devices [1], such as personal digital assistants (PDAs), mobile phones, notebooks, digital cameras, etc. which are operated intermittently. Gong and Mujumdar [2–4] carried out a series of numerical studies on heat transfer during melting and freezing of single and multiple PCMs. Casano and Piva [5] investigated the periodic phase change process of a plane PCM slab numerically and experimentally. Jiji and Gaye [6] examined analytically one-dimensional solidification and melting of a slab with uniform volumetric energy generation. The low thermal conductivity of PCMs presents a significant challenge in the design of PCM-based electronic cooling systems. In order to overcome this drawback, researchers have proposed various heat transfer enhancement techniques e.g. use of partitions/fins, graphite/metal matrices, dispersed high-conductivity particles in the PCM, and micro-encapsulation of PCM [7,8]. Use of PCM-based heat sinks is an effective way for cooling applications for electronic devices, as discussed by Pal and Joshi [9]. Tan and Tso [10] experimentally studied the cooling of mobile electronic devices using a heat storage unit filled with n-eicosane inside the unit. Krishnan et al. [11] proposed a hybrid heat sink which combined an active plate fin heat sink with the tip immersed in a passive PCM. Using scaling analysis of the governing two dimensional unsteady energy equations, Akhilesh et al. [12] presented a thermal design procedure to maximize the energy storage and operating time for a composite heat sink consisting of an elemental heat sink, PCM, and highly conductive base material. Recently, International Communications in Heat and Mass Transfer 34 (2007) 801 – 808 www.elsevier.com/locate/ichmt ☆ Communicated by A.R. Balakrishnan and S. Jayanti. ⁎ Corresponding author. E-mail address: mpeasm@nus.edu.sg (A.S. Mujumdar). 0735-1933/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.icheatmasstransfer.2007.03.008