INTRODUCTION

In a recent book (Baker 1996), I provided an introduction to fluid mechanics and thermodynamics, particularly aimed at instrumentation. I do not, therefore, propose to repeat what is written there but rather to confine myself to essentials. In addition, Noltingk (1988) has provided a very valuable handbook on general instrumentation. In this book, I shall use the term fluid to mean liquid or gas and will refer to either liquid or gas only when the more general term does not apply.

ESSENTIAL PROPERTY VALUES

Flowmeters generally operate in a range of fluid temperature from −200°C (–330°F) to 500°C (930°F), with line pressures up to flange rating for certain designs. Typical values of density and viscosity are given in Table 2.1.

It should also be noted that liquid viscosity decreases with temperature, whereas gas viscosity increases with temperature at moderate pressures. In common fluids, such as air and water, the value of viscosity is not dependent on the shear taking place in the flow. These fluids are referred to as Newtonian in their behavior as compared with others where the viscosity is a function of the shear taking place. The behavior of such fluids, known as non-Newtonian, is very different from normal fluids like water and air. Newtonian fluid behavior is a good representation for the behavior of the bulk of fluids.