Answer Happy

P5.10 A dual-duct multi-zone air conditioning system, consisting of
a
heating coil and a cooling coil, supplies air to 3 identical
zones,
maintained at 24°C db-temperature and 17°C wb-temperature. For
each
zone the sensible and latent heat loads are 34 kW and 22 kW
respectively. Of the total return air mass flow from the zones, 25%
is
discharged and replaced with outdoor air at 35°C db-temperature
and
40% relative humidity. The air leaving the heating coil is at 40°C
dbtemperature. At the exit of the cooling coil the air is at 10°C
dbtemperature and 90% relative humidity. The pressure is constant
at 101.3
kPa. (a) Draw a schematic diagram of the system. (b) Determine (i)
the
mass flow rate of air through the heating coil, (ii) the heat input
by the
heating coil, (iii) the mass flow rate of air through the cooling
coil, and
(iv) the refrigeration capacity of the cooling coil. Check the
overall
energy balance for the system.
[Answers: (i) 5.31 kgsí1, (ii) 71.76 kW, (iii) 13.2 kgsí1 (iv)
347.2 kW]