Numerical investigation of counter flow microchannel heat exchanger with MEPCM suspension Mushtaq I. Hasan * Mechanical Engineering Department, College of Engineering, Thi-Qar University, Thi-Qar, Iraq article info Article history: Received 12 March 2010 Accepted 28 November 2010 Available online 7 December 2010 Keywords: Counter flow Microchannel heat exchanger MEPCM Phase change material Thermal performance abstract The aim of this paper is to study the flow and heat transfer of microencapsulated phase change material (MEPCM) suspension in counter flow microchannel heat exchanger (CFMCHE) and it’s effect of the performance of this heat exchanger when using this suspension as a coolant instead of pure fluid. The hydrodynamic and thermal characteristics of this suspension flows in microchannels of CFMCHE is numerically investigated. The MEPCM suspension used in this paper consists of microcapsules con- structed from n-octadecane as a phase change material (PCM) and the shell material is poly- methylmethacrylate, these capsules are suspended in water in a concentration of (0e20)%. From the results, using of MEPCM suspensions as a cooling fluid lead to modify thermal performance of a CFMCHE by increasing its effectiveness but it also lead to increase the pressure drop. From heat transfer (thermal performance) point of view it is better to use this type of fluid to increase cooling efficiency of a CFMCHE, but due to extra increase in pressure drop it leads to reduce the overall performance compared with pure fluids. Therefore its use depends on the application at which this heat exchanger is used. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Microchannel heat exchangers are of interest because they can remove large amount of heat over a small volume. This ability makes it well suited for highly specific applications that require compact high heat energy removal solutions such as, biomedical processes, metrology, telecommunications, cooling of high heat flux high density microelectronics, automotive industries, nuc- lear reactor barriers, fuel processing, aerospace and chemical industries. Cooling fluids play an important role in cooling applications, and its thermo physical properties considered as key parameters that affect its cooling abilities. All the observed literature used pure fluids (liquids and gases) as cooling fluids in a CFMCHE. Using microencapsulated phase change material (MEPCM) suspensions has attracted more and more interest due to their capabilities of enhancing convective heat transfer and thermal storage performance. This heat transfer enhancement results from the latent heat absorption by the PCM in the suspended MEPCM particles during the melting process. Microchannel heat sink was first proposed by Tuckerman and Pease [1] for electronic cooling. They built a water cooled integral heat sink with microscopic flow channels, and demonstrated that extremely high power density with a heat flux as high as 790 W/ cm 2 could be dissipated . Following the work of Tuckerman and Pease, many researches have been conducted for microchannels and microchannel heat sinks. Klein et al. [2] studied experimentally the effects of surfac- tants solution on heat transfer of a single phase and boiling flows in microchannel heat sinks. The surfactant used is Alkyl Poly Glyco- sides (APG). The results were compared with the heat transfer in water flow under similar conditions. For single phase flow, no significant difference was observed between heat transfer in water and surfactant solutions at various mass concentrations. For boiling flow of surfactant solutions, the optimal value of mass flux was found in which the heat transfer enhancement reached its maximum. The experiment has also revealed that at low mass fluxes, an optimal mass concentration of APG additives may be found for which a two phase flow heat transfer significantly increases. These findings lead to the conclusion that the use of surfactants should be considered as a method for improving two phase boiling flow heat transfer. Yu et al. [3] experimentally investigated the laminar flow characteristics of suspensions with microencapsulated phase * Tel.: þ9647801140094. E-mail address: mushtaq76h@yahoo.com. Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng 1359-4311/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.applthermaleng.2010.11.032 Applied Thermal Engineering 31 (2011) 1068e1075