TITLE.PM5

480 ENGINEERING THERMODYNAMICS

dharm

\M-therm\Th10-2.pm5

15 Cº 25 Cº

D B T

1 2

W

75% RH

41% RH

h(kJ/kg)

h = 35.4 1

h = 45.2 2

Fig. 10.21
Example 10.18. It is required to design an air-conditioning plant for a small office room
for following winter conditions :
Outdoor conditions ...... 14ºC DBT and 10ºC WBT
Required conditions ...... 20ºC DBT and 60% R.H.
Amount of air circulation ...... 0.30 m^3 /min./person.
Seating capacity of office ...... 60.
The required condition is achieved first by heating and then by adiabatic humidifying.
Determine the following :
(i)Heating capacity of the coil in kW and the surface temperature required if the by pass
factor of coil is 0.4.
(ii)The capacity of the humidifier.
Solve the problem by using psychrometric chart.
Solution. Refer Fig. 10.22.
l Locate the points ‘1’ and ‘3’ on the psychrometric chart.
l Draw a constant enthalpy line through ‘3’ and constant specific humidity line through
‘1’.