A surface condenser is required to deal with 15 000 kg/h wet steam. Wet steam temperature is 37 C and enters the condenser with 0.95 quality (dryness fraction is 0.95). The water used for cooling has the following data:
- Inlet pressure 1.20 bar, inlet temperature 7 C
- Outlet pressure 1.013 bar, outlet temperature 22 C
Calculate the flow rate of cooling water and tube surface of the condenser. Assume that the cooling water velocity through tubes is 1.5 m/s
| Inputs |
Units |
|
|
Wet steam inlet temperature |
37 |
C |
|
Steam quality |
0,95 |
. |
|
Cooling water inlet temperature |
7 |
C |
|
Cooling water inlet pressure |
1,2 |
bar |
|
Cooling water outlet temperature |
22 |
C |
|
Cooling water outlet pressure |
1,013 |
bar |
|
Steam mass flow |
15000 |
kg/h |
|
Cooling water speed |
1,5 |
m/s |
|
Outputs |
. |
. |
|
Wet steam pressure |
0,06274 |
bar |
|
Enthalpy of steam at inlet |
2448,28 |
kJ/kg |
|
Entropy of condense |
154,92 |
kJ/kg |
|
Rejected heat/hour |
34400441,72 |
kJ/h |
|
Rejected heat/second |
9555,68 |
kJ/s = kW |
|
Enthalpy of water at inlet |
29,53 |
kJ/kg |
|
Enthalpy of water at outlet |
92,31 |
kJ/kg |
|
Water mass flow |
547885,14 |
kg/h |
The overall heat transfer coefficient can be calculated according to BEAMA or HEI standards.
BEAMA: British Electrical and Allied Manufacturers Association
BEAMA publication on the recommended practice for design of surface type steam condenser
HEI: Heat Exchanger Institute
HEI standards for steam surface condensers
| Outputs |
Unit |
|
|
Heat transfer coeff.(BEAMA) |
2,95235 |
KW/m2,K |
|
Logarithmic mean temp. diff. |
49,83 |
degree K |
|
Required area |
64,96 |
m2 |
If we use the less conservative HEI method we obtain the following:
| Outputs |
Unit |
|
|
Heat transfer coeff.(HEI) |
3,60991 |
kW/m2,K |
|
Required area |
53,12 |
m2 |