Jet impingement cooling of a constant heat flux horizontal surface in a confined porous medium: Mixed convection regime A. Sivasamy a, * , V. Selladurai b , P. Rajesh Kanna c a Department of Mechanical Engineering, Sri Krishna College of Engineering and Technology, Coimbatore, Tamil Nadu 641008, India b Department of Mechanical Engineering, Coimbatore Institute of Technology, Coimbatore, Tamil Nadu 641014, India c Department of Mechanical Engineering, Kalasalingam University, Tamil Nadu, India article info Article history: Received 14 July 2009 Received in revised form 5 January 2010 Accepted 30 June 2010 Available online 21 August 2010 Keywords: Porous medium Mixed convection Impinging slot-jet abstract In the present study, numerical investigation of jet impingement cooling of a constant heat flux horizon- tal surface immersed in a confined porous channel is performed under mixed convection conditions with the limitation of the Darcy model. The results are presented in the mixed convection regime with wide ranges of the governing parameters: Péclet number (1 6 Pe 6 1000), Rayleigh number (10 6 Ra 6 100), half jet width (0.1 6 D 6 1.0), and the distance between the jet and the heated portion (0.1 6 H 6 1.0). It is found that the average Nusselt number increases with increase in either Rayleigh number or jet width for high values of Péclet number. The average Nusselt number also increases with decrease in the distance between the jet and the heated portion. The correlation for Nu avg in the forced convection regime is suggested. It is shown that mixed convection mode can cause minimum average Nusselt num- ber unfavorably due to counteraction of jet flow against buoyancy driven flow. Hence, careful consider- ation must be given while designing a system of jet impingement cooling through porous medium. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The jet impingement cooling through horizontal porous layer are important from theoretical as well as application points of view. The buoyancy driven phenomena in porous media has at- tracted many researchers interests due to a large number of tech- nical applications, such as, fluid flow in geothermal reservoirs, insulation of buildings, separation processes in chemical indus- tries, dispersion of chemical contaminants through water satu- rated soil, solidification of casting, migration of moisture in grain storage system, crude oil production, solar collectors, electronic components cooling, etc. Comprehensive literature survey con- cerned with this subject is given by Gebhart et al. [1], Kaviany [2], Nield and Bejan [3], Pop and Ingham [4], Bejan and Kraus [5], Ingham et al. [6]. Bejan et al. [7] and Vafai [8]. The literature shows that the jet impingement through pure (non-porous) fluid has been studied extensively (see for example Al-Sanea [9], Chou and Hung [10], Seyedein et al. [11], Chiriac and Ortega [12], Chung and Luo [13], Sahoo and Sharif [14] and Sivasamy et al. [15]). Recently, many researchers considered the impinging jet through porous media. Fu and Huang [16] investigated numerically the effects of a laminar jet on the heat transfer performance of three different shape (rectangle, convex and concave) porous blocks mounted on a heated plate. They neglected the buoyancy effects and considered the forced convection mode only. Their results show that the heat transfer is mainly affected by a fluid flowing near the heated region. For a lower porous block, the three types of porous block enhance the heat transfer. However, for a higher porous block, the concave porous block only enhances heat transfer. A detailed flow visualization experiment was carried out by Prakash et al. [17] to investigate the effect of a porous layer on flow patterns in an overlying turbulent flow without heat transfer. They studied the effect of the parameters such as the jet Reynolds num- ber, the permeability of the porous foam, the thickness of the por- ous foam and the height of the overlying fluid layer. Jeng and Tzeng [18] studied numerically the air jet impingement cooling of a por- ous metallic foam heat sink in the forced convection mode. They found the porous aluminum foam heat sink could enhance the heat transfer from the heated horizontal source by impinging cooling. Their results show that the heat transfer performance of the alumi- num foam heat sink is 2–3 times larger than that without it. Saeid and Mohamad [19] studied numerically the jet impingement cool- ing of heated portion of an isothermal horizontal surface immersed in a fluid saturated porous media in the mixed convection regime. It was found for high values of Péclet number that increasing either Rayleigh number or jet width lead to increase the average Nusselt number. Narrowing the distance between the jet and the heated portion could increase the average Nusselt number. In many application the hot surface may be emitting constant heat flux instead of being isothermal, for example, embedded electronic component on a circuit board. Whenever, there is a large 0017-9310/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijheatmasstransfer.2010.07.063 * Corresponding author. E-mail addresses: a_sivasamy@yahoo.com, a.sivasamy@gmail.com (A. Sivasamy). International Journal of Heat and Mass Transfer 53 (2010) 5847–5855 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt