Application of the First and Second Laws to Fuel Minimization in a Batch Furnace

This paper presents results for the minimization of fuel consumption in a batch furnace. Several different criteria are used and minimized with respect to time- dependent process and control variables. As would be expected, the results show that globally there is no significant difference between the solutions found (i.e., the same minimum fuel consumption results) when the choice of criterion is either energy exergy, exergy destruction, entropy creation of the system and entropy creation of the system plus environment. However, the specific details or local results of each solution (i.e., the heating strategies) are, in fact, quite different. These differences cannot simply be attributed to numerical error (round-off and truncation). What they show is that multiple optimum strategies satesfy the same global optimum. The advantage of one over the other may simply be that from a practical standpoint some are easier to implement than others. Nonetheless, regardless of the strategy used, employing an optimum one raises the possibility of significant reductions in overall fuel consumption in these and other types of furnaces.