Calculations for AC used as dehumdifier in large building

[fastline]

We are working on sort of a green technology building where we will have other sources of heat removal but we still will have the issue of humidity that needs controlled. I have never developed any good calcs to quantify the btu/ton (or whichever relation) required for dehumidification only? HOWEVER, our design goal is actually to just use an AC without recirculation of supply air over the condenser coil. In a nut shell, an undersized AC that will mostly function as a dehumidifier.

I need to better understand the energy calcs to dehumidify air please!

[Brian_UK]

My friend Google found this......
http://www.way-technovation.com/Dehumidifier/calculat.htm#CALCULATING HUMIDITY LOAD

[moideen]

My friend Google found this......
http://www.way-technovation.com/Dehumidifier/calculat.htm#CALCULATING HUMIDITY LOAD

thank you brian,
nice link, helpful

[fastline]

Unless I missed something, these are all calculations of how much water is in the air and how much needs removed per qty time to maintain the target RH.

However, what I am trying to drive at is the power requirement in an AC system to do this. I can calculate the moisture in the air, I can calculate the BTUs required per the manual J or heat gain, but I need to determine how much power is required for the separate components of cooling air and reducing moisture.

I am probably not explaining this well and probably over thinking this.

[frank]

To remove moisture from air you need to cool the air below it's Dew point, and this is normally achieved by passing the air across a surface which is colder than the Dew point.

To achieve a surface colder than Dew point in a controlled situation normally involves mechanical cooling.

To determine the amount of moisture to be removed from the air and the temperatures to achieve this, we use the Psychrometric Chart http://www.psychrometric-calculator.com/aboutpsychrometrics.aspx

I don't know of any other method that is more accurate

[fastline]

I appreciate that. However, all these are doing is calculating the climate conditions and not the energy required to remove the water. Yes, I realize you need to calculate your conditions to determine dew point, as long as the evap is below dew point, you will be removing moisture. But how much? What affect does that have on BTUs for cooling capacity?

IE, you calculate the BTUs air cooling with simple air density, temp, evap temp, etc to arrive at how much heat is transferred to the evap. However, When you are also condensing water at the evap, that has to be taken into account.

I am trying to arrive at dividing these two modes unless you can say that when air crosses the evap, if the evap temp is lower than th dew point, ALL of the available energy will go into condensing the water before any air cooling is realized.



I think after thinking about this for a bit, the solution seems rather obvious. The latent heat of condensation of water?