номограма

This method may be applied in two situations: when the total air pressure drop for the system is given and when some values for the so-called economical velocity are imposed along the successive ducts. In the first case, the method consists in determining the necessary diameters for some ducts and for all the system. Thus, in this case, the total available pressure is divided to the total length of the main duct, giving as result the friction loss per meter of duct, also known as friction loss factor or specific linear pressure drop [Pa/m], which includes both major and minor losses.