CHAPTER 10 CONSIDERED MIXTURES OF ideal gases. In this chapter, we will apply a mixture analysis to investigate air–water mixtures, referred to as moist air. Since the water content in the air is relatively low, the partial pressure of the water is low. At low partial pressures, the water vapor can be approximated as an ideal gas and the moist air is an ideal-gas mixture. This chapter will first define some terms commonly used for moist air: specific humidity, relative humidity, and dew point. The analysis of moist air will then be used in several common applications: evaporative coolers, humidifiers, air conditioners, dehumidifiers, and cooling towers.

CHAPTER 10 CONSIDERS IDEAL gas mixtures. We will apply the ideal-gas properties from Chapter 2 to calculate the thermodynamic properties of nonreacting ideal-gas mixtures. These mixture properties will then be used in the conservation equations from Chapter 5 and entropy calculations from Chapter 7. With this analysis, we can study the mixing of two or more gases, the heating/cooling or compression/expansion of a mixture, and the operation of steady-state devices that use a mixture of ideal gases. Until this point, we have considered air as a simple ideal gas. In this chapter, we will look at the air properties considering the composition of the air.

WITH THE DISCLAIMER that we will consider neither situations involving nuclear transformations nor situations where relativistic effects are important, this chapter presents general and specific statements of mass conservation. We consider, first, closed thermodynamic systems. Before extending the mass conservation principle to open systems (control volumes), the concept of a flow rate and its relationship to the average velocity of a flowing fluid is introduced. The concept of steady-state, steady flow for open systems is presented. The principle of mass conservation is then applied to both steady and unsteady flows for single and multiple streams into and out of the system.

IN THIS CHAPTER, we introduce and define the subject of thermodynamics. We also introduce three complex practical applications of our study of thermodynamics: the fossil-fueled steam power plant, jet engines, and the spark-ignition reciprocating engine. To set the stage for more detailed developments later in the book, several of the most important concepts and definitions are presented here. These include the concepts of: open and closed thermodynamic systems; thermodynamic properties, states, and cycles; and equilibrium and quasi-equilibrium processes. The chapter concludes with an organizational overview of engineering thermodynamics and presents some ideas of how you might optimize the use of this textbook based on your particular educational objectives.

THE CHAPTER EXAMINES the principles of chemical equilibrium and phase equilibrium as extensions of the second law. We revisit entropy and define two other second-law properties: the Gibbs function and the Helmholtz free energy. The chapter explores how equilibrium relates to these three properties. The chapter focuses on the conditions of fixed temperature and pressure to explore chemical equilibrium. The equilibrium constant is defined and used to determine the detailed composition of a system. Simple, single, equilibrium reactions (dissociations) are investigated. The equilibrium constant approach is extended to multiple equilibria. The chapter also develops how minimization of the Gibbs function establishes the conditions for liquid–vapor (nonreacting) equilibrium.

THE FIRST LAW OF THERMODYNAMICS can be mathematically expressed in a variety of ways. All these expressions, however, are easily viewed as rearrangements of the statement that energy can neither be created nor destroyed but only converted from one form to another. In contrast, there is no single universally agreed statement of the second law of thermodynamics. Kline [1] indicates that many seemingly different statements have been accepted as the second law, all of which, however, can be shown to be equivalent after careful and sometimes subtle application of logic. This multiplicity of apparently disparate statements can lead to confusion in understanding the second law.

IN THIS CHAPTER, we see how steady-flow devices combine to form complex systems for power production, propulsion, heating, and cooling. Not only are such systems important from an engineering perspective, but more generally, they are essential to everyday life in industrialized societies. Here we analyze these systems to understand their basic operation and to determine various performance measures. Thermodynamic cycle efficiency, first introduced in Chapter 6, provides a dominant theme for this chapter. Here we investigate in some detail the energy conversion efficiency of the various systems just listed. In some sense, this chapter is the culmination of all the preceding chapters. Chapter 9 not only provides an opportunity to integrate knowledge gained from previous chapters but also provides interesting applications that can be explored in parallel with earlier chapters.illustrates the key role that Chapter 9 plays in our study. The system analysis is shown as bridging, or using, all the previous topics.