Hello i am getting this error message: 'Cannot change pump to fan because there is only one adjacent cell thread.' When i include the fan as (pump=boundary condition name) as boundary condition

Since the fan is considered to be infinitely thin, it must be modeled as the interface between cells, rather than a cell zone. Thus the fan zone is a type of internal face zone (where the faces are line segments in 2D or triangles/quadrilaterals in 3D). In other words, for a 3D problem, on both sides of the fan boundary zone you have to put some cells. If, when you read your grid into FLUENT, the fan zone is identified as an interior zone, use the Boundary Conditions panel to change the appropriate interior zone to a fan zone.

MfG, Karl

What Karl said is right. Just refining your grids can solve this problem

thanks to all of you