Steam Desuperheater Performance Analysis
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1. Superheated Steam Properties
a. Pressure: 185 psig (199.696 psia)
b. Temperature: 525 F
c. Enthalpy: 1282.51 Btu/lb
d. Specific Volume: 2.8156 ft^{3}/lb
e. Mass Flow: 120,000 lb/hr
f. Energy Flow: 153,901,200 Btu/hr
2. Cooling Water Properties
a. Pressure: 325 psig (339.696 psia)
A rule of thumb is that the cooling water must be at least 75 psi higher than the pressure of the steam being desuperheated. Also the pressure of the water before
the control valve needs to be around 60 psi higher for the control valve pressure
drop. Thus the pressure before the control valve needs to be 185psig + 75 +60 =
320 psig minimum.
b. Temperature: 217 F
c. Enthalpy: 185.02 Btu/lb
d. Specific Volume: 0.01684 ft^{3}/lb
e. Mass Flow: Must be calculated
f. Energy Flow: Must be calculated
3. Desuperheated Steam Properties
a. Pressure: 185 psig (199.696 psia)
b. Temperature: 415 F
c. Enthalpy: 1219.80 Btu/lb
d. Specific Volume: 2.4229 ft^{3}/lb
e. Mass Flow: Must be calculated
f. Energy Flow: Must be calculated
4. Equation & Calculation
a. Equation:
m_{ss}(lb/hr) x h_{ss} (Btu/lb) + m_{water} (lb/hr) x h_{water} (Btu/lb) = (mss + m_{water})lb/hr x h_{desuperheated steam}
(120,000 x 1282.51) + (m_{water} x 185.02) = (120,000 x 1219.80) + (m_{water} x 1219.80)
153,901,500 + 185.02 m_{water} = 146,376,000 + 1219.80 m_{water}
7,525,500 = 1034.78 m_{water}
m_{water} = 7,272.56 lb/hr
GPM^{cooling water} = 7,272.56 lb/hr x 0.01684 ft^{3}/lb x 7.4805195 gal/ft^{3} x 1.0 hour/60min
= 15.27 gal/min
m_{desuperheated steam} = m_{superheated steam} + m_{cooling water}
= 120,000 lb/hr + 7272.56 lb/hr
= 127,272.56 lb/hr 
5. Computer Program Answers
a. Mass Flow of Cooling Water: 7253 lbs/hr
b. GPM_{cooling water} = 15.10 gal/min
Steam Desuperheater Computer Program Printout
DESUPER
1. Superheated Steam Input Data
a. Pressure: 185 psig
b. Temperature: 525 F
c. Mass Flow: 120,000 lb/hr
2. Cooling Water Input Data
a. Temperature: 217 F
3. Desired Desuperheated Steam Properties Input Data
a. Pressure: 185 psig
b. Temperature: 415 F
4. Program Output Data – Required Cooling Water
a. Cooling Water Mass Flow: 7253 lb/hr
b. Cooling Water Volume Flow: 15.10 gal/min
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