It is essential to enhance the efficiency of the furnace through the reduction of high fuel consumption for obtaining required temperature of the furnace. A significant improvement in one of the furnace components that will improve overall efficiency of the furnace. Six Sigma DMAIC methodologies were implemented in the furnace manufacturing company to reduce the thermal energy in exhaust flue gas which extremely impacts the efficiency of the furnace. Thus, DMAIC phases revealed that, the best solution to the shell and tube heat exchanger by increasing heat transfer rate and reducing thermal energy in the waste flue gas through implementation of circular fins over bare tubes. The sigma level was improved from1.34 to 2.01. The monetary savings was achieved about Rs.0.34million per year.