flow rate vs rate of flow

flow rate and rate of flow both are nouns.

Word	Noun	Adjective	Verb	Adverb
flow rate	Yes	No	No	No
rate of flow	Yes	No	No	No

As nouns, flow rate and rate of flow are synonyms defined as:

flow rate and rate of flow: the amount of fluid that flows in a given time

Other synonyms of flow rate include flow.

flow rate (noun)	rate of flow (noun)
the amount of fluid that flows in a given time	the amount of fluid that flows in a given time