Resources for designing new HVAC
This conference presentation (PDF) seems to lay out the process fairly well. It also mentions a few resources that go into more detailed calculations and considerations.

The Sheet Metal and Air Conditioning Contractors’ National Association has an overview guide available here (PDF) for improving efficiency. They also have entire standards available for download for a fairly hefty price tag too.

There's also this seemingly in-depth duct loss calculator here.

It's by no means comprehensive, but you may be able to get a basic understanding of the design process.