Pressure In static Fluids Fluid Mechanics Pressure In static Fluids CHE 312/CHE315

Introduction Objectives Define and classify fluids Define static Fluids vs. Dynamic Fluids Explain pressure in a static fluid Derive the equation of pressure in a static fluids Show examples of applications of static pressures. CHE 312/CHE315

Introduction Fluid: A continuous substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas. CHE 312/CHE315

Introduction Types of Fluids: 1.Incompressible Fluids: Effect of pressure on the fluid is neglected (small) Most liquids are incompressible CHE 312/CHE315

Introduction Types of Fluids: 2.Compressible Fluids Gases are compressible CHE 312/CHE315

Introduction static Fluids vs. Dynamic Fluids CHE 312/CHE315

Introduction Pressure in A Static Fluid CHE 312/CHE315 Furnace ductPipe or tube Pressure is a Normal Force (acts perpendicular to surfaces) It is also called a Surface Force Dam

Introduction P=F/A Pressure in A Static Fluid F =mg P=  gh h P = h ρ g + P 0 P0P0 CHE 312/CHE315 P

Introduction the vertical height of a fluid that determines the pressure in fluid, the shape of the vessel does not affect the pressure. CHE 312/CHE315

Introduction CHE 312/CHE315

Introduction CHE 312/CHE315

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Introduction Summary CHE 312/CHE315

Pressure In static Fluids CHE 312/CHE315 Pressures units: Pascal (N/m 2 ), Psi, dynes/cm 2, etc… A common method of expressing pressure, is in terms of head (h) in meter (m) or feet (ft) of a particular fluid: 2.2C HEAD OF A FLUID ……………………………………………………………………. …………………………………………………………………….. …………………………………………………………………….

Pressure In static Fluids CHE 312/CHE315 h (m) = P/(  *g) h (ft) = P*g c /(  *g) in SI units in English units ……………………………………………………………………. …………………………………………………………………….. …………………………………………………………………….

Pressure In static Fluids CHE 312/CHE D DEVICES TO MEASURE PRESSURE AND PRESSURE DIFFERENCES In industrial processing, it is important to measure and control the pressure and/or the liquid level in a vessel or process. For Flowing pipes, flow rate is also needed. Thus, pressure measurements are important.

Pressure In static Fluids CHE 312/CHE315 SIMPLE U-TUBE MANOMETER Density of Fluid A > Density of Fluid B A and B are immiscible P a is exerted on one arm of the tube and P b is exerted on the other arm. Z R Fluid A Fluid B P a P b

Pressure In static Fluids CHE 312/CHE315 Pressure difference between P a and P b : Pressure at point 1: P 1 =P a Pressure at point 5: P 5 =P b At point 2: P 2 =P a +(Z+R)  B g (R: reading of the manometer) Z R Fluid A Fluid B P a P b

Pressure In static Fluids CHE 312/CHE315 At point 3: P 3 =P 2 Also, P 3 = P b +Z  B g + R  A g Therefore, P 3 = P a +(Z+R)  B g = P b +Z  B g + R  A g Z R Fluid A Fluid B P a P b P a -P b = R  A -  B ) g (SI ) P a -P b = R  A -  B ) g/g C (English )