Can u someone give me good solution?
I have node. but it does not work.
The first problem is that you are feeding in a name, instead of an element, as required by this parameter (always check with Parameter.StorageType).
Try and see what you get. Probably the parameter is read-only.
I might be totally wrong, but while ducts can have different SystemType (you can pick supply, return etc…), the air terminals are usually not so free.
I.e. Supply Diffusers admit only supply, Exhaust Grills admit only exhaust etc…
Maybe you want change air terminal type? In this case pick the correct family type and use Family and Type as input for Element.SetParameterByName.