How do I find the supply air condition from psychrometric chart?

[Zapperosini]

I saw the solution from FAQ but I would like know why we have to intersected the 95% curve on the chart, at 95%Rh (read 50 Deg.F.DB) by SHR slope line.

Thank u

 

[imok2]

When ever air is cooled below it's dew point the cooled air becomes saturated therefor it's relative humidity goes up. So if air is cooled to 55 degrees it is usually in a saturated condition. For example: if the room temperature is 75*F and 50% RH the dew point is ~ 58*F so if the cooling coil is cooling the air below that temperature it will become saturated or close to it. We could go on with this discussion but I'm sure you get the point. Others may have a better explanation

 

[Zapperosini]

Thank u imok2!! Your help makes me more understand about the psychrometric. But, how could I select the proper value for my design (Ambient 95Deg.F,74%Rh , Room 77Deg.F,50%Rh ,SHR = 0.9)

 

[imok2]

To maintain the room temperature at about 75*F and 45 -60% relative humidity you should have an air off the cooling coil of about 55-57degrees with about 400 CFM +or- 10%