Because energy can take several different forms, it is necessary for us to understand the forms that are of primary interest to a chemical engineer. These forms are briefly described in the following section.
7.1.1 Forms of Energy
Three primary forms of energy are encountered in a chemical process [1]:
1. Kinetic energy (KE)—Energy associated with motion. Kinetic energy of a body of mass m and velocity v is ½mv2. Clearly, a body moving at a higher velocity has higher kinetic energy than one of equal mass but lower velocity.
2. Potential energy (PE)—The energy associated with position. Potential energy of a body of mass m is mgh, where g is acceleration due to gravity and h, its distance from the earth’s surface.
3. Internal energy (U)—Stored energy associated with atomic and molecular structure and characteristics.
Other forms of energy, such as electric and magnetic field energies, are typically not of interest in chemical processes [2] and are not included in the analysis presented in this book. The energy of a system, E, comprises these three primary forms. The first two forms of energy (kinetic and potential) constitute the mechanical energy of the system.
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