technical reference for sizing high velocity a/c system

Unico and SpacePak

both have on-line literature available last time I checked.

Guidelines as to outlets per ton, CFM per outlet and so-on are well published and recognized. Both system manufacturers are similar enough that one will stand in for the other in terms of principles of operation, layout and installation considerations.

I think you understand that sizing still requires a calculated heat gain load. The AC is sized to absorb the sensible (temperature based) load. The latent or moisture-related load takes care of itself with these systems and then some.

Tip:

One think I would recommend if you can afford to do so is make the supply duct a loop or ring duct. Plenty of pressure in reserve and the airflows tend to be more even at each outlet.

Unico offers especially good and complete technical information.

To access click "Technical Library and Notes" at the left and create a user account (free). Organization isn't the best, but the information is VERY complete. I suggest that you print out most everything.

As Brad mentioned, a "loop" system is the ideal and you should strive for such layout. Little excuse for not using such a layout in new construction, but may be impractical or even impossible in retrofits. Pay particular attention to balancing! Reference branch length is 10' and shorter should not be used due to noise issues. Longer increases restriction and reduces flow so compensation must be made.

When a loop layout of the main trunk cannot be used, engineering can become quite complex. Pay strict attention to recommendations of outlet positions and percentages of any branches to the main. Simple and well-labeled sketches will aid you GREATLY until you home in on the "best" design.