air leaving temperature-psychrometric
air leaving temperature-psychrometric
(OP)
The method of find out the actual leaving air temperature of cooling apparatus, here an example takes an FCU. The chilled water entering temperature 47F, bypass factor .20 and entering air temperature is 75F. Please see the calculation as per the psychometric formula
Tldb=Tadp+bf(Tedb-Tadp), then 47+.02(75-47)=52.6F( 11.4C) is it practical in field?
Tldb=Tadp+bf(Tedb-Tadp), then 47+.02(75-47)=52.6F( 11.4C) is it practical in field?





RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
Chicopee X = 49 by trial & error in excel.
RE: air leaving temperature-psychrometric
Apparatus dew point temperature is not equal to the entering chilled water temperature to the fan coil unit.
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
Apparatus dewpoint temperature and bypass factors are now not used in rating fan coils. Google Trane chilled water fan coils and see ratings base on unit size, CFM, EWT, WTR, Entering Air EDM/EWB. The ratings are given in TC (total capacity MBH), SC (sensible capacity MH), GPM, WTR (Water temperature rise, PD water pressure drop ft of water.
SC x 1000 = 1.1 x CFM x (Tedb - Tldb)
Tldb = Tedb - (SC x 1000)/ (CFM x 1.1)
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
RE: air leaving temperature-psychrometric
To me, this is minutia. As a general rule, if you need a space (e.g., pharmacy or OR) that wants a 68°F indoor temperature and less than 55% RH (dew point of 51°F), supply 52°F air during the summer and reheat the air to the desired room condition. The supply air temperature is the key; the fins per inch, bypass factor and other parameters matter, but are generally academic.
Wait, I might've answered the wrong question again... Sorry, I like going off on tangents.
RE: air leaving temperature-psychrometric
CFM dehumidified air = (Total Sensible Heat BTU/hr) / (1.08 x (TF ent clg coil - TF lvg clg coil)
CFM dehumidified air = (Total Latent Heat Btu/hr) / (0.68 x (W grains/lb ent clg coil - W grains/lb lvg clg coil)
Total Sensible Heat = Room Sens + OA Sens + Fan Heat Gain + Duct Heat Gain
Total Latent Heat = Room Latent + OA Latent
For space HVAC CFM dehumidified air is usually = Room Sensible Heat Btu/hr / (1.08 x 20) but this may be changed depending on the coil selection.
Select coil type, and fin arrangement and at maximum 500 fPM face velocity to avoid moisture carryover. Try out various available circuit arrangement to pick coil meeting desired leaving conditions with minimum air pressure drop and with less than 20 ft water pressure drop.