Calculating Fuel Consumption for a Boiler at 2.1 MN/m2 Pressure

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Discussion Overview

The discussion revolves around calculating the fuel consumption for a boiler producing superheated steam at a specified pressure and temperature. Participants are exploring the thermal efficiency of the boiler, the relevant equations, and the necessary parameters for the calculation, including the calorific value of the fuel oil and the enthalpy values for steam and water.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a homework statement involving the calculation of fuel consumption based on steam production, thermal efficiency, and calorific value.
  • Participants question the initial calculations, suggesting that the results seem too low and prompting a review of the formula used.
  • There is a discussion about the need to account for the heat contained in the superheated vapor and the heat from the feedwater, indicating that these factors are essential for an accurate calculation.
  • Another participant emphasizes the importance of understanding the difference between the heat of vaporization and the additional heat required for superheating.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to the calculation, with some expressing uncertainty about the formula and others highlighting the need for additional considerations in the calculations.

Contextual Notes

Participants note missing elements in the calculations, such as the heat contribution from the superheated vapor and the feedwater, which are not fully addressed in the initial attempts.

Who May Find This Useful

This discussion may be useful for students or professionals interested in thermodynamics, boiler operations, and fuel consumption calculations in engineering contexts.

0drt9
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Homework Statement


A boiler is to produce 6250 kg/h of steam superheated by 40 oC at a pressure of 2.1 MN/m2. The temperature of the feedwater is 50 oC. If the thermal efficiency of the boiler is 70%, how much fuel oil will be consumed in one hour? The calorific value of the fuel oil used is 45000 kJ/kg, cp of superheated steam is 2.093 kJ/kg K.
for pressure 2.1 Mn/m2
hfg = 1880 kJ/kg
hf = 920 kj/KG
sat temp - 214.9

Homework Equations


in my notes i have efficiency as [generated steam * hfg] / [fuel consumed * CV ]

The Attempt at a Solution


my attempt gave me the answer of 373 which i found to be to small of a value
 
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Show your work.
 
gneill said:
Show your work.

i used efficiency = [generated steam * hfg] / [fuel consumed * CV ]
for efficiency i used 0.70, for generated steam 6250, hfg 1880, CV as 45000
and i found for the fuel consumed
 
0drt9 said:

Homework Statement


A boiler is to produce 6250 kg/h of steam superheated by 40 oC at a pressure of 2.1 MN/m2. The temperature of the feedwater is 50 oC. If the thermal efficiency of the boiler is 70%, how much fuel oil will be consumed in one hour? The calorific value of the fuel oil used is 45000 kJ/kg, cp of superheated steam is 2.093 kJ/kg K.
for pressure 2.1 Mn/m2
hfg = 1880 kJ/kg
hf = 920 kj/KG
sat temp - 214.9

Homework Equations


in my notes i have efficiency as [generated steam * hfg] / [fuel consumed * CV ]

The Attempt at a Solution


my attempt gave me the answer of 373 which i found to be to small of a value
I don't know about the formula in your notes.

Remember, hfg is the difference in the amount of heat contained in saturated vapor and saturated liquid.

What about the extra amount of heat which is contained in the superheated vapor? Where does that come from?
What about the heat which is brought into the boiler from the feedwater at 50° C? How is that accounted for?
 

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