Ek for a quick start I would learn the equal friction method of sizing ducts and get familiar with a ductulator. If you want to become a master learn the static regain method for a duct sizing. The majority of designers use the equal friction method for duct sizing while also not exceeding max velocity limits, some use the static regain but this is more time consuming even though it is a better method as good as the others. Good luck.
Kay is correct on Mannual D and you should get it and study it. It has the various duct designing methods in therel ASJRAE also has a chapter on duct design which is also ecellant in I beleve there Applications Hand Book (they have 4 handbooks). Thank you very much
"I could have ended the war in a month. I could have made North Vietnam look like a mud puddle."
"I have little interest in streamlining government or in making it more efficient, for I mean to reduce its size. I do not undertake to promote welfare, for I propose to extend freedom. My aim is not to pass laws, but to repeal them. It is not to inaugurate new programs, but to cancel old ones that do violence to the Constitution."
Sen. Barry Goldwater