Page 77 - Industrial Ventilation Design Guidebook

4 2 CHAPTER 4 PHYSICAL FUNDAMENTALS

4.3.8 Diffusion through a Porous Material 138
4.3.9 Example of Drying Process Calculation 141
4.3.10 Evaporation from a Multicomponent Liquid System 146
4.4 WATER PROPERTIES AND TREATMENT 148
ERIC F. CURD
4.4.1 Introduction 148
4.4.2 Common Water Impurities 148
4.4.3 Cooling Water Systems 152
4.4.4 Water Treatment 155
References 162

4.1 FLUID FLOW

It is essential that the engineer involved in industrial ventilation have a good
foundation in the subject of fluid mechanics, which involves the study of flu-
ids at rest or in motion.
The fields of application are wide involving computational fluid dynamics
(CFD), flow in ducts and pipes, pumps, fans, collection devices, pollution dis-
persal, and many other applications.

4.1.1 Fluid Properties

4.1.1.1 Fluid Classification
Matter is considered to exist in three states
• Solid
• Liquid
• Gaseous
The term fluid applies to both liquids and gases, including liquids and gases
containing particulate matter of various sizes.
When a shearing stress is imposed on a solid, deformation occurs, until a
point is reached when the internal stresses produced balance the shearing
stresses. Provided the elastic limit for the material is not exceeded the solid
will return to its original shape when the load is removed.
A fluid, on the other hand, flows under the action of a shearing stress no
matter how small this stress is. A fluid at rest has no shearing stresses, and all
forces are at right angles to the surrounding surfaces. Materials such as glass
and solid bitumen are fluids and, if stressed for a period of time, will tend to
flow.

Ideal Fluid
A theoretical ideal fluid situation, "a perfect fluid" having a constant den-
sity and no viscosity, is often used in a theoretical analysis.