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Two-dimensional, steady, mixed convection flow in an enclosure filled with a Darcian fluidsaturated uniform porous medium is considered. Both the left wall and the right wall are moving upwards with same velocity. They are maintained at cold and hot constant temperatures respectively. The top and the bottom walls are fixed and are thermally insulated. The governing equations are normalized and solved numerically with boundary conditions by finite volume approach using third order accurate upwinding scheme (deferred QUICK). To validate the code, comparisons are made with previously published work and are found to be in excellent agreement. The study is conducted by varying the key parameters i.e., Richardson number (Ri ¼ Gr=Re 2 ), Darcy number (Da ¼ j=H 2 ) and Grashof number (Gr ¼ gbH 3 DT=n 2 ) and fixing Prandtl number (Pr ¼ 0:71). A parametric study is conducted and a set of streamline and isotherm plots are presented. The average Nusselt number reaches a value of 1 asymptotically when the Ri is gradually increased for Gr up to 10 3 . For Gr ¼ 10 4 , the asymptotic value is 1.5. An empirical heat transfer correlation is also presented.

Purpose -The purpose of this paper is to consider a two-dimensional, steady, mixed convection flow in an enclosure filled with a fluid-saturated uniform porous medium. The left wall is moving down and the right wall is moving up and are maintained at cold and hot constant temperatures, respectively. The top and the bottom walls are fixed and are thermally insulated. Design/methodology/approach -The governing equations are normalized and solved numerically with appropriate boundary conditions by finite-volume approach using third-order accurate scheme (deferred QUICK). Findings -The study is conducted by varying the key parameters, i.e. Richardson number (Ri ¼ Gr=Re 2 ), Darcy number (Da ¼ =H 2 ) and Grashof number (Gr ¼ gH 3 ÁT= 2 ) and fixing Prandtl number at (Pr ¼ 0:71). A parametric study is conducted and a set of streamline and isotherm plots are presented. The average Nusselt number reaches a value of 1 asymptotically when the Ri is gradually increased for Gr up to 10 3 . The asymptotic value is 1.5 for Gr ¼ 10 4 . A heat transfer correlation is also presented. Originality/value -The study of the mixed convection problem with lid-driven flows in enclosures will be useful in cooling of electronic devices, lubrication technologies, chemical processing equipment, etc.

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