A simple steady-state thermal energy balance can be constructed around a constant-pressure combustion system (such as a boiler), which is useful in a number of contexts. Figure 4.1 shows the energy flows into and out of the system which are considered. Before the energy balance is developed it is worth looking more closely at the terms involved:
  1. (a)

    H R, H P and CV are all related to the standard temperature of 25°C. The enthalpy of the entering air is considered to be sensible heat only (i.e. the fuel/air is considered to be a dry mixture).

  2. (b)

    The enthalpy of the flue gas must be consistent with the calorific value of the fuel which is used in the balance. If the gross calorific value is used, then H R should contain a latent heat term equal to the mass of water produced per kilogram of fuel multiplied by the latent heat of evaporation of water at 25°C (h fg). If the net calorific value is used, then the flue gas enthalpy will consist of sensible heat terms only. In this chapter we are concerned with predicting the temperature reached within the flame, hence the net calorific value/sensible heat terms system is the more appropriate.



Combustion Product Flame Temperature Bituminous Coal Gross Calorific Value Heat Term 
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    Mayhcw YR, Rogers GFC (1984). Thermodynamic and Transport Properties of Fluids. Blackwell, OxfordGoogle Scholar
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    Spencer HM (1945). Empirical heat capacity equations. J Amer Chem Soc 67: 1859–60CrossRefGoogle Scholar
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    Stoecker WF (1989). Design of Thermal Systems, 3rd edn. McGraw-Hill, New YorkGoogle Scholar

Copyright information

© Springer-Verlag London Limited 1994

Authors and Affiliations

  • Victor Ian Hanby
    • 1
  1. 1.Department of Civil EngineeringUniversity of TechnologyLoughborough, LeicestershireUK

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