Air conditioner and Duct sizing question

[jakb21599]

Hello friends, got a question about sizing an air conditoner and duct sizes for a 20 ft. x 20 ft. room with a 13 ft ceiling. The room will be used for a commercial kitchen. I`m a refrigeration tech by trade, but i am not up to speed on sizing a unit for a kitchen with heavy heat load , so i`m hoping you AC guys out their can help me out.
The room will be insulated and have an exhaust vent over the stoves that will be in thier. The total length of the supply duct would be 33 feet from the package unit outside to the end of the run inside the building. The return duct would be 20 feet from the package unit outside to the inside wall. I`m thinking maybe running the supply trunk down the center of the room and branching off 3 drops on each side of the room ( total of 6 drops) The length of the drops will be 6 ft. from main supply trunck line. I`m thinking maybe a 3 ton unit will be enough to handle the load. ( Any advice would be great on sizing the unit also ) So what size unit do you think i need to keep the room semi comfortable ( i know it wont be very comfortable because its a kitchen, just looking for whats average for a kichen area) Do you think a 3 ton will be enough or should i go higher ? You guys are more familiar with this kind of stuff than i am What ever your suggestion is on sizing of the unit, can you tell me also what size the supply trunk will be and the return trunk will be. What size will the branch offs from the supply trunk need to be ?
Thanks for your help

[Magoo]

Full extract from over ovens vats etc., balanced with supply fresh air make-up , run extract and minimal negative pressure so as not to spread cooking smells. Use a hood arrangement over cooking area, add fat and activated carbon filters within the hood for ease of cleaning. Fresh air is the most economical form of cooling add a cooling package to supply air system if necessary, capacity will not be large dependant on local ambient conditions, if winter conditions are cold then restrict supply air volume, and allow pressure balance with static louvers. As a check walk into a McD's and sit and look at system they adapt to all there outlets.

[cool_tech]

I have only seen Evap cooling in comercial kitchens if any cooling at all. You know what they say... If you cant stand the heat get out of the kitchen. What ever you put in has to match whats going out so you dont over pressurise the area letting smells and smoke out. Magoo has the right idea sounds like he has worked on theese systems.