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Show Introduction This paper focuses on the theoretical performance of thermal devices -- furnaces and engines -- with a particular emphasis on thermal efficiency. As we will show, the analytical description of furnace behavior commonly known as Furnace Analysis can be applied to the whole range of all furnaces and engines used in industry. This analysis is based on a simple first law integral procedure which gives a single operational or "Firing" equation that governs performance. This can be done without need to include the more practical details of design or operation of the engine, furnace, burner, and fuel supply system. The basis for this Furnace Analysis is to be found in treatments whose origins are generally attributed to Hudson in 1890 [1]. Hudson developed an empirical input/output equation to describe steam boiler performance that, in 1926, was modified and extended by Orrock to become the Hudson-Orrock equation [2]. This was substantially the origin and driver that initiated a number of other studies, both theoretical and experimental from the decades of the 1920' s and 30' s onwards. A landmark experimental study by Annstrong in 1927 was the fIrst to show the influence and importance of output (Hs) as a major factor in determining furnace efficiency [3]. Following that, theoretical studies were initiated, particularly by Wohlenberg and Wise [4] and by McAdams and Hottel [5] to provide a fundamental basis for the empirical Hudson-Orrock equation, and to extend that analysis. In the following decades, there were further contributions relating to a wide variety of systems including forge furnaces, melting and reheating furnaces, oil retorts, blast furnaces, and, particularly glass tanks. In a 1974 Review of Furnace Analysis studies and results, Essenhigh et al. were able to cite over 40 sources of both experimental and theoretical studies that were mostly. available in the archival literature, and it is known that there is a further major body of studies reported in Conference and other limited circulation reports, in addition to restricted company studies [6]. The operational behavior of these diverse thermal systems can all be described based on the inflows and outflows of energy across the system boundaries. The treatment is general and therefore can be applied to broad classes of thennal systems, regardless of whether the system is a "First Law" (e.g., materials processing) or a "Second Law" (e.q., heat engine) device. The primary description of the operational behavior is represented by the Firing Equation, which relates the energy consumed by the device and the useful output from the device. From the Firing Equation, two other "Perfonnance" equations are easily obtained that then describe: the actual or operational thermal efficiency; and the design or 2 |