ABSTRACT

This chapter deals with fundamentals of thermal methods for sensing and measuring mass fluid flows. he working range for any mass flux sensor is somewhat dependent on the fluid properties, such as thermal conductivity, specific heat, and density, but not on the physical state of the fluid. The chapter discusses the principles of conventional thermal mass flow sensors. The dependence of the heat loss between a fine wire as well as a thin film and the surrounding fluid has traditionally been the most accepted method for measuring a fluid flow. The hot-film method uses film sensors for detecting the flow. The displacement of the temperature profile caused by the fluid flow around a heating element can be used for measuring very small mass flow. Depending on the location of the heating and sensing elements, there are two types of calorimetric sensors: the intrusive sensors that lie in the fluid and the nonintrusive sensors that are located outside the flow.