maybe this would help

http://soar.wichita.edu/bitstream/handle/10057/5374/t12003_Ahmed.pdf;sequence=1

If possible please send the current picture of the mesh and the various parameters which you have used.

I am using a negative pressure of one bar at outlet, and the mold is a rectangular plate 100x300x5 mm. What other parameters are required?

Additionally, the flow is laminar and at room temperature

Dear Khubab,

I would like to know the program which is used to solve the case and tell me if your interest to find the velocity distribution or the temperature distribution too. Note that you have to define the energy equation for temperature distribution.

You can use the Bernoulli equation using the first point in the entry section and the second point in the exit section. The known parameter in the inlet will be pressure and elevation and the unknown is the velocity.

In addition, the exit section will have the level and pressure as known parameters and the velocity difference can be calculated. 

Good luck