Nozzle spacing is based on calculations performed by the manufacturer's software. There is not a standard (like 13) that can be used for clean agent. You must meet concentration and discharge distances when designing.
There is not any "standard" oriface diameters that I am aware of.
There is no standard orifice for clean agent nozzles. They are sized according to the calculation program specific to that agent. The basic nozzle size matches the pipe size as determined by the program and the orifice sizes are custom drilled to meet the calculation results.
As mentioned previously the number of nozzles is determined by the listed coverage per nozzle. What you have to watch though is areas with suspended ceilings. If the coverage is ok with one nozzle you may very easily "overpressurize" the area in the vicinity of the nozzle and blow out tiles. To retain ceiling tile in place, and thus retain the agent, you generally have to spread out the discharge to more nozzles. I don't think the manufacturer design manuals tell you this.
KCfpe is correct except I might add that a room has to pass 'room integrity testing'. Ceiling tiles coming out is not an option and they must be pinned in place. A system isn't designed to compensate for tiles blowing out.
