Thermodynamics

Chapter 13GAS MIXTURESUp to this point, we have limited our consideration tothermodynamic systems that involve a single puresubstance such as water. Many important thermodynamicapplications, however, involve mixtures of several puresubstances rather than a single pure substance. Therefore, itis important to develop an understanding of mixtures andlearn how to handle them.In this chapter, we deal with nonreacting gas mixtures.A nonreacting gas mixture can be treated as a pure substancesince it is usually a homogeneous mixture of differentgases. The properties of a gas mixture obviously depend onthe properties of the individual gases (called components orconstituents) as well as on the amount of each gas in themixture. Therefore, it is possible to prepare tables of propertiesfor mixtures. This has been done for common mixturessuch as air. It is not practical to prepare property tables forevery conceivable mixture composition, however, since thenumber of possible compositions is endless. Therefore, weneed to develop rules for determining mixture properties froma knowledge of mixture composition and the properties of theindividual components. We do this first for ideal-gas mixturesand then for real-gas mixtures. The basic principles involvedare also applicable to liquid or solid mixtures, called solutions.ObjectivesThe objectives of Chapter 13 are to:• Develop rules for determining nonreacting gas mixtureproperties from knowledge of mixture composition and theproperties of the individual components.• Define the quantities used to describe the composition of amixture, such as mass fraction, mole fraction, and volumefraction.• Apply the rules for determining mixture properties to idealgasmixtures and real-gas mixtures.• Predict the P-v-T behavior of gas mixtures based onDalton’s law of additive pressures and Amagat’s law ofadditive volumes.• Perform energy and exergy analysis of mixing processes.| 681