A room in a building has the following characteristics: Sensible heat gain: 90,000 Btu/hr, Latent heat gain: 40,000 Btu/hr, Supply air: 3,600 cfm @ 55 deg. F db
Air ventilation: 700 cfm, The room is kept at 78 deg. F db and 45% rh. Outdoor air is 92 deg. F db 76 deg. F wb.
What is the wet bulb wb air temperature entering EAT and wb temperature of air leaving the cooling coils LAT in the room?
[LAT = 55 deg. F db, given, need to calculate EAT db, LAT wb. The EAT db of the air entering the cooling coils is the mixed temperature = [(room temp db)(2,900) cfm + (outside air temp db)(700)]/3,600 cfm. Find EAT wb and h of EAT from chart. Find h of outside air from chart. Then Q for outside air = (4.5)(?h)(cfm) where cfm is outside air ventilation = about 26,800 Btu/hr (show this), then total Q = (sensible heat gain) + (latent heat gain) + (outside air heat gain) = about 157,000 Btu/hr (show this), then total Q = (4.5)(?h)(total cfm), then find (?h) from total Q, then find h of leaving air from ?h, then find wb temp of leaving air LAT wb from chart. We get EAT = 80.7 deg. F db/66.2 deg. F wb, LAT = 51.7 deg. F wb.]
