Ideal temperature drop trough the cooling coil

[mbane]

I have difficuilty to determine the ideal temperature drop through the airconditioning coil. I have the passibility to measure temperature differnce (DB)trough the coil,RH of incoming air and CFM.I need something to compare this delta T with.Is it possible to get this information from the psychometric chart?Do I need any other information (air conditioning size, atmosveric pressurre...)?

Thanks

 

[hollandhvac]

Hint, the temperature can not go lower than the temperature of the refrigerant.

So your max temmp diff is on coil minus your refrigerant temperature. Than you have got to look at the efficiensy of the coil so get your real off coil temperature.

 

[imok2]

The temp drop across the coil is determined by the wet bulb on the coil,that is to say as the WB goes up the temperature difference goes up For example If the DB on the coil is 76*f at 65*F WB then the evaporator leaving temp would be ~58*F. If the DB were 76*F and 67*F WB the air off the coil would be~60*F The higher the wet bulb the less sensible heat removed. For air conditioning it goes something like this Refrigerant temp 45*F, air off the coil about 55*F air on the coil about 76*F temp difference about 20*F so if your getting about 16*F to 20*F you are probably ok depending on the wet bulb as I just explained. and yes there are charts that tell you what the approxmate temp should be. Go to page 30

http://www.udarrell.com/ACBasicsProctor1.pdf

 

[mbane]

Thanks everybody,
I saw the chart. It's nice. The only concern is the CFM. This chart is made for 400 CFM/Ton. In the field we have different CFM per ton - usualy from 350 to 450 sometimes even more. From my previous experience with CFM increasing and delta T decresing. Do you have any idea how they made this chart? Maybe I can modify it.

P.S. Is it meter? What is the size of the A/C when we calculate these valuas.

Thanks.

 

[imok2]

Yes it assumes a ~ 400 CFM and a full charge of refrigerant.
and Yes the delta T decreases with an increase in CFM because the by pass factor increases and the sensible heat
increases and latent heat decreases.AS far as I can determine 400 cuft/min/ton is an ARI standerd for a wet coil

 

[mbane]

Do you have any idea how they made this chart? Maybe I can modify it.