20–35%
Energy saving from recuperation
LMTD
Log mean temperature method
NTU-ε
Effectiveness-NTU method
< 2 yr
Typical payback period

Calculations Available

  • Recuperator thermal duty from flue gas temperature and flow rate
  • LMTD (log mean temperature difference) for counter-flow and parallel-flow
  • Heat transfer area required (Q = U × A × LMTD)
  • Combustion air preheat temperature prediction
  • Fuel saving from preheat — % reduction in gas consumption
  • Annual energy cost saving and simple payback period
  • Effectiveness-NTU method for compact heat exchangers
  • Flue gas dew point check — acid condensation risk

Combustion Air Preheat Savings

Preheat Temp Fuel Saving Flue Temp
150°C ~8% 700°C furnace
250°C ~15% 900°C furnace
350°C ~22% 1100°C furnace
450°C ~28% 1200°C furnace
600°C ~35% 1300°C furnace

Approximate — varies by flue gas composition and excess air. Use calculator for accurate results.

Furnace Heat Recovery — The Business Case

Industrial furnaces lose 30–60% of their energy input through flue gas waste heat — the largest single energy loss in most heat treatment operations. A recuperator (air-to-air heat exchanger) captures some of this heat and uses it to preheat combustion air, directly reducing gas consumption. At current gas prices, a well-sized recuperator typically pays back within 18–30 months.

The heat exchanger calculator takes your furnace operating temperature, gas consumption, and flue gas exit temperature, then calculates the available heat recovery potential, required exchanger size, predicted preheat temperature, and estimated payback period. Bloor Engineering designs and supplies recuperators for industrial furnaces and can provide detailed quotations based on your specific process data.

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Related: Heat Treatment Calculators · Maintenance Checklist · Energy Efficiency Guide