Category: Basic Concepts

Note: Some of the steam table homework problems involve enthalpy, H, which is defined for convenience using properties discussed in this chapter, H ≡ U + PV. The enthalpy calculations can be performed by reading the tabulated enthalpy values from the tables in an analogous manner used for internal energy. We expect that students will be…

P1.1. Estimate the average speed (mph) of hydrogen molecules at 200 K and 3 bars. (ANS. 3532) P1.2. Estimate the entropy (J/g-K) of steam at 27.5MPa and 425C. (ANS. 5.1847)

Years from now you may have some difficulty recalling the details presented in this text. On the other hand, the two basic premises outlined in this introductory section are so fundamental to technically educated people that you really should commit them to long-term memory as soon as possible. Formally, we may state our two basic…

The thermodynamic behavior of real fluids differs from the behavior of ideal gases in most cases. Real fluids condense, evaporate, freeze, and melt. Characterization of the volume changes and energy changes of these processes is an important skill for the chemical engineer. Many real fluids do behave as if they are ideal gases at typical process conditions. P-V behavior…

The System A system is that portion of the universe which we have chosen to study. A closed system is one in which no mass crosses the system boundaries. An open system is one in which mass crosses the system boundaries. The system may gain or lose mass or simply have some mass pass through it. An isolated system is one devoid of…

To be fair to both of the central concepts of thermodynamics, we must mention entropy at this point, in parallel with the mention of energy. Unfortunately, there is no simple analogy that can be drawn for entropy like that for potential energy using the gravitational forces between the Earth and moon. The study of entropy…

Energy is a term that applies to many aspects of a system. Its formal definition is in terms of the capability to perform work. We will not quantify the potential for work until the next chapter, but you should have some concept of work from your course in introductory physics. Energy may take the form…

These considerations should give you some idea of the potential range of applications possible within the general study of thermodynamics. This text will try to find a happy medium. One general unifying principle about the perspective offered by thermodynamics is that there are certain properties that are invariant with respect to time. For example, the…