ABSTRACT
The general term fluid conveys any substance that does not have a form. Liquids and gases are both fluids. Further, to differentiate liquids from gases, liquids have a surface, whereas a gas will expand to fill a volume. Liquids are generally considered nearly incompressible, whereas gases are readily compressible. The vast majority of coolant flows are of the incompressible type. However, the equations may require correction for the properties of a compressible fluid due to the altitude. This text emphasizes incompressible flow.
