The thermodynamic calculation of the exploited heat H ex for melting glass is the effective approach to analyze the energy used in the melting furnace. The efficiency of the furnace can be estimated by H ex /H in . Knowing the characteristic of the furnace such as the efficiency and the heat or power consumption of the furnace is very useful for planning the energy conservation direction. Results Furnace A is operated at a lower capacity than the furnace B (Fig. 2) . The efficiency of the

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... e can be determined by the ratio of H ex /H in . In this case the efficiency of the furnace A is about 20% and furnace B is about 30%. Thus, furnace A should produce more glass in order to increase the efficiency. The total loss in the furnace is independent on the pull. The total loss of furnace A is about 1300 kWh and furnace is about 2500 kWh. This implies that the furnace B is rather old compared to the furnace A. The improvement of the wall losses may be needed. Abstract In this study H ex for melting the soda-lime glass is examined by thermodynamic calculations. Then, the heat balances of two furnaces, which are operated under difference conditions, are calculated. The output of this project will be used as a guideline for the industry to optimize the melting energy as well as to encourage glass technologists to use of thermodynamic calculations in analyzing their processes.