Analysis of fluid flow and heat transfer in a channel with staggered porous blocks H.Y. Li a , K.C. Leong a, * , L.W. Jin a , J.C. Chai b a School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Republic of Singapore b Mechanical Engineering Department, The Petroleum Institute, Abu Dhabi, United Arab Emirates article info Article history: Received 14 June 2009 Received in revised form 21 October 2009 Accepted 7 January 2010 Available online 6 February 2010 Keywords: Fluid flow Local heat transfer Porous media Staggered porous blocks abstract Fluid flow and heat transfer characteristics in a channel with staggered porous blocks were numerically studied in this paper. The NaviereStokes and BrinkmaneForchheimer equations were used to model the fluid flow in the open and porous regions, respectively. Coupling of the pressure and velocity fields was resolved using the SIMPLER algorithm. The local thermal equilibrium model was adopted in the energy equation to evaluate the solid and fluid temperatures. The effect of Darcy number, Reynolds number, porous block height and width on the velocity field were studied. In addition, the effects of the above parameters as well as the thermal conductivity ratio between the porous blocks and the fluid on the local heat transfer were analyzed. The pressure drops across the channel for different cases were discussed. The results show that the flow behavior and its associated local heat transfer are sensitive to the variation of the above parameters. It is predicted by the present study that an increase in the thermal conductivity ratio between the porous blocks and the fluid results in significant enhancement of heat transfer at the locations of the porous blocks. Ó 2010 Elsevier Masson SAS. All rights reserved. 1. Introduction The investigation of forced convection heat transfer in a channel filled with porous media is of practical interest in the industry. It has been demonstrated that heat sinks made of porous media with high thermal conductivity and large surface area improve heat transfer performance and thus are widely used in various industry applica- tions such as heat exchangers, chemical reactors and heat pipes [1e4]. The fundamentals of heat transfer in porous media have been studied extensively in the past decades [5e8]. Recent investigations of heat transfer in porous media with spherical open cell micro- structure such as metal and graphite foams indicate that such materials offer more promising prospects for use in heat sinks [9e14]. A channel can either be partially or fully filled with a porous medium. In the fully filled case, the channel would be completely occupied by the porous medium. If it were to be partially filled, the channel would usually be inserted with porous layers [Fig. 1(a)] or discrete porous blocks [Fig. 1(b)]. Many experimental and numer- ical studies have been performed to investigate the transport phenomena in channels fully filled with a porous medium [9,15]. However, it was reported that substantially high pressure drop will occur in these channels [11,16] while those partially filled with porous media have much lower pressure drops [11,16,17]. Studies of channels partially filled with porous media [16,18e20] showed that it may not be necessary to completely fill the channel with the porous medium to derive the maximum heat transfer. Fu et al. [21] and Zhang and Zhao [22] numerically studied the convection heat transfer in a channel with a single porous block mounted on the heated wall. In the work of Fu et al. [21], various parameters including the geometry of the porous block and Reynolds number were studied. Their results showed that heat transfer was enhanced by using a porous material with higher porosity and particle diameter and with a height of the porous block which is half that of the channel. Zhang and Zhao [22] also showed that heat transfer is significantly enhanced in the channel with single porous block. Many studies have been reported on the channel with multiple porous blocks arranged on one side of the wall [23e26]. Among them, the pioneer study involving a channel with multiple porous blocks attached on the external surface of a plate was carried out by Huang and Vafai [23]. Their results showed that the presence of porous blocks significantly changes the characteristics of fluid flow and heat transfer. A detailed study of forced convection enhance- ment in a channel with multiple porous blocks arranged on the bottom wall was reported by Huang and Vafai [24]. The stream function-vorticity method was adopted to simulate the fluid flow in the composite geometry. The effects of various parameters such as Darcy number, Reynolds number, Prandtl number on the flow field and heat transfer were investigated. Their results showed that the local heat transfer was closely related to the velocity field. The vortices that occurred in the flow field have significant effects on * Corresponding author. Tel.: þ65 6790 5596; fax: þ65 6792 4062. E-mail address: mkcleong@ntu.edu.sg (K.C. Leong). Contents lists available at ScienceDirect International Journal of Thermal Sciences journal homepage: www.elsevier.com/locate/ijts 1290-0729/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ijthermalsci.2010.01.006 International Journal of Thermal Sciences 49 (2010) 950e962