[EsinDerin]

Hello, I'm trying to do CFD analysis for a solar chimney. I did everything according to paper called "Numerical performance modelling of solar chimney power plants: Influence of chimney height for a pilot plant in Manzanares, Spain." But still get the result for mass flow rate negative. Then I did the half of the size of Manzanares model with 1600 W/m^2 irridance, but this time my mass flow rate is too low for the model. I used k-epsilon 2 eqn model. I don't know where I'm doing wrong, could someone help me please? Thank you already.