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Pressure •For air to flow there must be a pressure difference and air will flow from the higher pressure to the lower pressure • Pressure is considered to have two forms: –static pressure (P s) – velocity pressure (P v) With the sum of these being total pressure (P t).
Purpose and Learning Objectives. The purpose of this presentation is to provide industry professionals with an overview of the basic concepts and relationships between airflow and pressure, and how these concepts are affected by various outside factors in regard to fans.
Dynamic pressure is the kinetic energy of a flowing fluid - liquid or gas - per unit volume - and can be expressed as. p d = 1/2 ρ v2(1) where. p d = dynamic pressure (N/m2(Pa), lbf /ft2(psf)) ρ = density of fluid (kg/m3, slugs /ft3 ) v = velocity (m/s, ft/s)
This curve shows the relationship between the air flow rate and the pressure of an air system. Complex systems with branches and junctions, duct size changes, and other variations can be broken into sections or sub-systems.
Units of Pressure. Pressure has engineering units of N m or Pascals (Pa) in the SI system or lb ft (pounds per square foot) in the U.S. customary (USC) system. In practice, kilo-Pascals (kPa) units may be used because a Pascal is a small pressure value.
Static pressure graphical presentation throughout a fluid flow system. Pressure Units - Online Converter Convert between pressure units like Pa, bar, atmosphere, pound square feet, psi and more.
Units of pressure. As stated earlier, the SI unit for pressure is the pascal (Pa), where \[1\; Pa = 1\; N/m^{2} \ldotp\] In addition to the pascal, many other units for pressure are in common use (Table \(\PageIndex{1}\)). In meteorology, atmospheric pressure is often described in the unit of millibars (mb), where
