TABLE OF CONTENTS Fluid mechanics is the study of the behavior of fluids at rest, fluid statics, and in motion, fluid dynamics, and of the properties of fluids insofar as they affect the fluid motion. A fluid may be either a gas or a liquid. The molecules of a gas are much farther apart than those of a liquid. Hence a gas is compressible while a liquid is relatively incompressible.
A vapor is a gas whose temperature and pressure are such that it is very near the liquid phase. Steam is considered a vapor because its state is normally not far from that of water. A gas may be defined as a highly super-heated vapor, that is, its state is far removed from the liquid phase. Air is considered a gas because its state is normally very far from that of liquid air.
The volume of a gas or vapor is greatly affected by changes in pressure or temperature or both. It is usually necessary to take into account the changes in volume and temperature in dealing with gases or vapors. Whenever significant temperature or phase changes are involved in dealing with vapors and gases, the subject is largely dependent on heat phenomena, thermodynamics.
The objective of this chapter is to introduce the reader to certain terminology, concepts, laws, and equations that are directly applicable to the design of air-cooled heat exchangers and cooling towers.
Consider the flow of a fluid over a flat plate...
