الملخص

A model of fluid flow with heat transfer by conduction , convection and radiation has been discussed for stability with respect to restricted parameters (k,a,r,T*) which are proportional to: wave numbers, thermal expansion coefficient, combination of many numbers (Re,Pr,Ec,Bo,W,)and the ratio of walls temperatures, respectively using analytical technique which illustrates that the stability of the system depends on these parameters  and the disturbances with a larger wave number, grows faster than that with smaller wave number .A clear picture of the flow is shown in the velocity field,tables and figures.