It is required to maintain the air in a building at 20oC and 40%saturation when the
outside conditions are 28oC, 50% saturation with a barometricpressure of 1.01325
bar. The total heat gains to the room (sensible plus latent) are 15kW, and the latent
heat gains are 3 kW. There is no reciculation and the fresh airpasses over a cooling
coil to dehumidify it, and then a heater, before entering the room.The cooling coil by
pass factor is 0.2; the volume flow of fresh air is 5 m3/s,calculate:
a. The temperature of the air leaving the cooling coil;
b. The refrigeration load for the coil;
c. The heat supplied in the heater
d. If the air-con system is to be adapted for use in winter withthe same room
conditions of 20oC and 40% saturation. The mass flow rate of dryair from
the heater is to be kept the same as in summer. The outsideconditions are
-5oC, 100% saturation, and the sensible heat loss from theconditioned
space is 34.5 kW with the same latent heat gain of 3 kW. A savingin
energy is obtained by recirculating a portion of the room air usinga mixing
box and dispensing with the washer. Calculate
i. The ratio of room air to fresh air that must be used for thesystem to
operate satisfactory;
ii. The heat supplied in the heater under these conditions.