Furnace efficiency
Consider a fuel fired furnace used to heat the charge at the temperature  . The furnace attains a steady state temperature at certain ratio of mass of fuel/mass of air. At steady state operation of the furnace, a certain amount of heat Hin is generated at the adiabatic flame temperature by combustion of fuel. Heat is being carried out by the products of combustion (HPOC) at temperature  . The heated charge carries heat (Hu) at temperature . Some amount of heat  is lost at temperature  through the walls of the lining. The inputs and output of heat are shown in the figure
| Figure 39.1: |
Heat balance of a furnace at steady state |
Steady stale heat balance at the constant furnace temperature and constant fuel input rate is
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