3A - Fundamentals of Liquid Pipeline Hydraulics

Seite 1

Design disciplines: Hydraulics - mechanical - geotechnical - operations and maintenance

disciplines are closely interrelated

hydraulic--> pipeline route- pipe size- operating P and T- number of pump stations

mechanical --> pipe material selection- pipe specifications - burial depth requirements

geotechnical-->surface loads - water crossings - buoyancy control- geo-hazard management

operations and maintenance --> control systems - operating tasks while maintaining integrity

Flow dictated by three conservation laws - MASS - MOMENTUM - ENERGY

4 independent variable define hydraulic states - Pressure - temperature- flow rate - density

4 equations are required to relate 4 independent variables

mass, momentum, energy and EOS are the 4 equations

1D form used to describe flow in pipeline

mass conservation equation slide 6 3A

cross sectional area can change due to P or T

Cp has a large effect on acoustic speed of pressure wave? ( Cp is the specific heat capacity)

momentum equation slide 7-8 3A

first term force due to acceleration

second term is force due to kinetic energy

third term is force due to pressure difference

fourth term is force due to gravitation

fifth term is force due to friction on pipe

darcy weisbach equation to calculate pressure drop due to friction

frictional pressure drop linearly proportional to density and friction factor

frictional pressure drop squarely proportional to velocity

frictional pressure drop inversely proportional to pipe diameter

equation for frictional pressure drop in slide 8

friction factor function of reynolds and pipe roughness

3 flow regimes --> laminar, critical, turbulent (partially turbulent & fully turbulent)

Re=density x velocity x diameter/viscosity

ratio of inertial forces to viscous forces

Re increases with increase in velocity, density and diameter

kinematic viscosity used more because independent of density

laminar flow friction factor --> slide 9

critical flow 2400

laminar independent of pipe roughness

partially turbulent depends on Re and pipe roughness

fully turbulent depends on relative roughness

JAIN'S approximation (use this)--> slide 11

Energy equation--> slide 12

first term is temperature change over time

second term is temperature change due to net convection

third term is change in rate due to expansion/compression

forth term is heat flow due to conduction

fifth term is the effect of work due to gravity

sixth term is heat due to friction

EOS defines relation between density, pressure, and temperature

EOS --> Slide 13

Assumptions --> no chemical change takes place- single phase flow - steady state

steady state: no significant change in pressure and flow remain constant

parameters included in hydraulic design --> Slide 17