# 14.1: Introduction

Thermodynamics plays an important role in science and engineering. Most physical processes of engineering interest operate on thermodynamic principles. Thermodynamics is the science dealing exclusively with the principles of energy conversion. This message is conveyed by the word itself: “thermo” means “heat” — a manifestation of energy — and “dynamics” deals with “motion.”

Often times, we do not use thermodynamics as much as we should. This is either because we do not know how useful a tool it can be, or, simply because we do not know how to use it.

The basic ingredients for the utilization of thermodynamics are:

• The ability to identify and define the system that best characterizes a given process
• The availability of relevant information
• Sound engineering judgment

The goal of this module, combined with all the background that we already have built on fluid behavior, is to establish a foundation for us to cultivate a culture of the appropriate utilization of thermodynamics.

What kinds of problems can be solved with thermodynamics? There are three general classes of thermodynamic problems.

1. System property variation determination. In this case, we are given a process that takes place under certain known constraints. We are required to determine how the system properties vary.
2. Interactions that cause change. In these kinds of problems, the changes desired in the system properties are prescribed. We are required to determine the amount of external interactions that are needed to cause these changes — i.e., how to vary constraints to obtain the required final system state.
3. The best-path problem. Here we are given a system with constraints and a desired variation. We are required to determine the best way to accomplish the change — i.e., the best way to reach a goal.

In science and engineering, mathematical rigor is of essence. The next sections will take us through the mathematics of thermodynamics.

## Contributors

• Prof. Michael Adewumi (The Pennsylvania State University). Some or all of the content of this module was taken from Penn State's College of Earth and Mineral Sciences' OER Initiative.