In an air conditioning plant, airflow rate of 2 kg/s passes through a spray water humidifier with a contact factor 0.7. The calorifier provides 40 kW. Determine the moisture content and temperature of the air leaving the humidifier and the amount of make-up water needed. The dry and wet-bulb temperatures of the inlet air are 9 C and 3 C respectively.
| Inputs |
Units |
|
|
Inlet air, DBT |
9,00 |
C |
|
Inlet air, WBT |
3,00 |
C |
|
Inlet air, mass flow rate |
2,00 |
kg/s |
|
Contact factor of the humidifier |
0,70 |
. |
|
Heat provided by the calorifier |
40,00 |
kW |
|
Atmospheric pressure |
1,01 |
bar |
The contact factor of a humidifier is defined as the efficiency for humidification. A 100% efficient humidifier will bring the moisture content of the air to the saturation moisture content at the apparatus dew-point, mcC. The contact factor of the humidifier can be defined by the moisture content differences:
cf = (mcB - mcA)/(mcC - mcA)
or
cf = (hB - hA)/(hC - hA)
| Output | |||
|
moisture content of inlet air |
0,0022 |
. |
|
|
Spec. enthalpy at inlet |
14,5 |
kJ/kg |
|
|
Spec. enthalpy at outlet |
34,4999 |
kJ/kg |
|
|
Spec. enthalpy at ADP |
43,0713 |
kJ/kg |
|
|
Temperature at ADP |
15,3825 |
C |
Assumed |
|
moisture content at ADP |
0,0109 |
. |
|
|
Estimate spec. enthalpy at ADP |
43,0712 |
kJ/kg |
|
|
Diff = Estimated(h) - h = 0 |
0,0001 |
. |
Goal |
|
Use solver to reach the goal |
. |
. |
|
|
moisture content of outlet air |
0,0083 |
. |
|
|
make-up water req. |
0,0122 |
kg/s |
|
|
Dry-bulb temp at outlet |
13,50 |
C |