Well, the problem is that i am using the source term only because i did not get good results when using a heat flux boundary condition on r2 so i don't know why i am not able to get good results when applying W/m2 on r2 ?
yes i am using boussinesq approx, and the operating temperature is the same i am imposing at pressure boundaries (278k)
i changed the inlet and outlets as you said, now i am getting heat balance around 1%,, and the velocity field is not really logical,
any suggestions please why i am getting this strange velocity field ? and every time i increase iterations (5000 to 7000) the velocity field change
for the rayleigh number, based on the water properties, and temperature difference (2 deg, between r3 and fluid wall temp, and length scale i have(length of the square side) , i got a value of 3.4 e7
and for reynolds number, i dont know which velocity to take , since it is varying from different boundaries