1.Convert actual steam rating into From and At 100 C
Steam capacity from and at 100 C (212 F) is equivalent steam capacity if operating conditions are reduced to atmospheric pressure.
Steam capacity = 8000 kg/hr at 10.5 kg/cm2 saturated
Feed water inlet = 30 C
Heat load = 8000 (664-30) Kcal/hr
= 5.072e06 Kcal/hr = 20.127e06 btu/hr = 5.8976 MW
where Sat steam enthalpy = 664 Kcal/kg
Inlet water enthalpy = 30 Kcal/kg
Steam enthalpy at 100C and 1 atm pressure = 540 Kcal/kg
Therefore, steam capacity F&A 100 C = 5.072e06/540
= 9392 Kg/hr
2. Heat Duty Calculations :
Let us calculate heat duty of a boiler generating 50,000 kg/hr at 65 bar and 485 C
Water inlet temperature = 105 C
Steam & water properties:
Superheated steam enthalpy at 65 bar & 485 C = 808 Kcal/kg
Saturated water enthalpy = 295 Kcal/kg
Heat Duty = 50000 x (808 - 105)
= 35.15e06 Kcal/hr (139.48e06 Btu/hr or 40.87 MW)
Usually 1 – 3% of the water flow is used for blowdown.
Considering 2% blow down , heat in blowdown water = 50000 x 0.02 x (295 – 105)
= 0.19e06 kcal/hr
Total heat duty = (35.15 + 0.19) e06 = 35.34e06 kcal/hr
= 140.24e06 Btu/hr = 41.09 MW
In case of Hot water generator or hot water boiler,
Heat duty = Water flow x Cp of water x Temp gain
For example, 200,000 kg/hr of water is heated from 70 to 90 degC,
Heat Load = 200,000 x 1 x (90-70)
= 4.0e06 Kcal/hr
= 15.873e06 Btu/hr or 4.651 MW
3. Heat Transfer calculations:
Over all heat transfer coefficient,
Uo = 1/(1/Ho+Rm+1/Hi*(TubeOD/TubeID)+Ro+Ri*(TubeOD/TubeID))
Where Ho = Outside heat transfer coefficient
Hi = Inside heat transfer coefficient
Rm = tube metal resistance
Ro = Fouling resistance on outside tubes
Ri = Fouling resistance on inside tubes
Inside Heat Transfer coefficient can be calculated using the following correlation :
NuInside=0.023* (ReInside^0.8)*(PrInside^0.4)
Where NuInside = Hi x TubeID / Gas Cond
Outside heat transfer coefficient during boiling is very high and so resistance offered is negligibly small. There are many correlations available to predict Ho, but Ho can be safely assumed to be about 10000 Kcal/hr/m2/C.
Steam capacity from and at 100 C (212 F) is equivalent steam capacity if operating conditions are reduced to atmospheric pressure.
Steam capacity = 8000 kg/hr at 10.5 kg/cm2 saturated
Feed water inlet = 30 C
Heat load = 8000 (664-30) Kcal/hr
= 5.072e06 Kcal/hr = 20.127e06 btu/hr = 5.8976 MW
Publish Post
where Sat steam enthalpy = 664 Kcal/kg
Inlet water enthalpy = 30 Kcal/kg
Steam enthalpy at 100C and 1 atm pressure = 540 Kcal/kg
Therefore, steam capacity F&A 100 C = 5.072e06/540
= 9392 Kg/hr
2. Heat Duty Calculations :
Let us calculate heat duty of a boiler generating 50,000 kg/hr at 65 bar and 485 C
Water inlet temperature = 105 C
Steam & water properties:
Superheated steam enthalpy at 65 bar & 485 C = 808 Kcal/kg
Saturated water enthalpy = 295 Kcal/kg
Heat Duty = 50000 x (808 - 105)
= 35.15e06 Kcal/hr (139.48e06 Btu/hr or 40.87 MW)
Usually 1 – 3% of the water flow is used for blowdown.
Considering 2% blow down , heat in blowdown water = 50000 x 0.02 x (295 – 105)
= 0.19e06 kcal/hr
Total heat duty = (35.15 + 0.19) e06 = 35.34e06 kcal/hr
= 140.24e06 Btu/hr = 41.09 MW
In case of Hot water generator or hot water boiler,
Heat duty = Water flow x Cp of water x Temp gain
For example, 200,000 kg/hr of water is heated from 70 to 90 degC,
Heat Load = 200,000 x 1 x (90-70)
= 4.0e06 Kcal/hr
= 15.873e06 Btu/hr or 4.651 MW
3. Heat Transfer calculations:
Over all heat transfer coefficient,
Uo = 1/(1/Ho+Rm+1/Hi*(TubeOD/TubeID)+Ro+Ri*(TubeOD/TubeID))
Where Ho = Outside heat transfer coefficient
Hi = Inside heat transfer coefficient
Rm = tube metal resistance
Ro = Fouling resistance on outside tubes
Ri = Fouling resistance on inside tubes
Inside Heat Transfer coefficient can be calculated using the following correlation :
NuInside=0.023* (ReInside^0.8)*(PrInside^0.4)
Where NuInside = Hi x TubeID / Gas Cond
Outside heat transfer coefficient during boiling is very high and so resistance offered is negligibly small. There are many correlations available to predict Ho, but Ho can be safely assumed to be about 10000 Kcal/hr/m2/C.
2 comments:
Hello Dude..
Nice informations on Heat Transfer Coefficient system.It Monitoring a heat exchanger, by using the heat transfer coefficient.Heat transfer in a steam generator involves convection from the bulk of the reactor coolant to the steam generator inner tube surface, conduction through the tube wall, and convection from the outer tube surface to the secondary side fluid.
Thanks for sharing..
Heat Transfer Coefficient
The formulas above may look very difficult to read, especially for those who are afraid of numbers. But those studying industrial engineering should make it a habit to memorize these for them to achieve accuracy.
Jasmin Shakespeare
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