The laminar flow Q' [m³/s] through a pipe with circular cross section is calculated using:

pipeflow calculator >>

Where D_h is the hydraulic diameter, which is the inner diameter of the pipe. For different cross sections the hydraulic diameter D_h is calculated using:

where A is the area of the cross section and S the wetted perimeter. For a rectangular groove with sides a and b the diameter D_h becomes:

and the space formed between two concentric pipes:

The flow through a thin film is calculated using:  

filmflow calculator >>