ABSTRACT
The invention of the steam engine in the eighteenth century ushered in the Industrial Revolution. This revolution was made by practical engineers, most of whom, like Thomas Edison a century later, “measured everything by the size of a silver dollar” (or, since many of them were British, the size of a gold sovereign), and had little use for what Edison called “the bulge-headed fraternity of the savanic (sic) world.” However, Carnot1 was an exception: He founded the science of thermodynamics in an attempt to hnd out if there is a fundamental limit to the e^ciency with which heat can be converted into work. This search led to the discovery of the second law of thermodynamics, which does indeed impose such a limit, and he was able to enunciate the second law even before the hrst law was recognized. A heat engine is any device that converts heat (usually generated by
burning some fuel) into work. An idealized model of a heat engine is shown in Figure 15.1(a). While the hgure is based on the steam engine, we
Figure 15.1. (a) Schematic heat engine. Energy 4ow is represented by labelled arrows, substance 4ow by unlabelled ones. The work needed to drive the compressor comes from the engine. (b) Idealization of the essential processes of the Carnot cycle: in one cycle the engine takes in heat Q1 at T1, rejects heat Q2 at T2, and delivers net work W = Q1 Q2.
