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Show "Intrinsic" efficiency. These three equations provide a complete integral description of the thennal perfonnance of relevant devices. Since it is available elsewhere, the general derivation of the three Perfonnance equations is only summarized here [6-9] . Instead, this paper discusses the application of this approach to internal combustion engines, making note of similarities between furnace and engine behavior and of necessary extensions to the analysis to properly describe perfonnance. Development of the Firing Equation Using the flISt law of thennodynamics, an analysis of the energy flows across a control volume surrounding a combustion device leads to an analytical relationship between energy inputs (fuel) and useful outputs (process or power). Examples of systems that can be considered in this way range from glass melting furnaces to internal combustion engines. The total schema of input, combustion device, and output is illustrated in Fig. 1. This Figure includes representation of appropriate preparation processes for the fuels and raw materials and makes clear the common features shared by all combustion systems. The outputs may include a wide range of effluents as co-products, including ash and liquid waste streams such as cooling water, in addition to the air pollutants, if any, in the products of combustion. The essential feature is that a fuel is consumed and a useful output is produced. The analysis focuses on the integrated thennal behavior of the combustionchamber/ furnace shown as the central component of Fig. 1 and is based on a First Law energy balance applied to a control volume (CV) enclosing the furnace or engine . . For this purpose, the energy inflows and outflows, shown as bands in Fig. 1 and defmed in enthalpy flow tenns of energy per unit time, can be reduced to only four: (1) H r the thennal input, generally from firing the fuel; (2) Hs' the useful thennal output defmed as either sensible heat in the process product or as delivered power from an engine; (3) Hg, the loss in the exhaust gases to the stack or exhaust; (4) "wall" losses, H w' that in the case of engines can include frictional and similar losses; and (5) Hso, the input enthalpy of the processed material. Conservation of energy of the CV yields: (1) Relating the input HI to the output Hs requires the elimination of the other tenns in Eq. (1). This is accomplished by linearizing the wall and exhaust gas losses with respect to the output. For boilers, linearizing the wall with respect to output or assuming the wall 3 |