Furnace, Kiln, and Oven Heat Losses

Lower flue gas exit temperature saves fuel Better heat transfer rate lowers gas exit temperature Lower firing rate lowers gas exit temperature Excess air can absorb heat intended for the load 

Long flames or added burners near the flue raise flue temperature, and thus waste fuel 

Low firing rate may reduce circulation and create nonuniformities that cost more fuel 

Limited amounts of excess air may enhance circulation or complete mixing at low firing rates 

Regenerative burners save fuel with very low exit gas temperatures Inerts in flue gas recirculation endanger flame stability and steal heat 

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