Water Transport Modelling

  • View
    3

  • Download
    0

Embed Size (px)

DESCRIPTION

Water Transport Modelling

Text of Water Transport Modelling

  • 1

    POLITECNICO DI TORINO

    WATER AND OIL

    PIPELINES SIZING

    Master of Science: Petroleum Engineering

    Course: Oil and Gas Transportation

    Prof. Coordinator: Student:

    Guido Sassi Frincu Iuliana Aurora

    S196092

    2014

  • 2

    TABLE OF CONTENTS

    INTRODUCTION.....3

    I. WATER PIPELINE... 4

    I.1. Geometry and elevation...5

    I.2. Water properties...... 5

    I.3. Water pipeline sizing....6

    I.4. Water pipeline pressure profile... 8

    I.5. Pumps and valves.... 9

    I.6. Other considerations.... ..15

    II. OIL PIPELINE.......16

    II.1. Oil properties......16

    II.2. Oil pipeline sizing......16

    II.3. Other considerations.......23

    III. CONCLUSIONS.........24

    Bibliography

  • 3

    INTRODUCTION

    Transport or transportation is the movement of people, animals and good from one location to

    another. Modes of transport include air, rail, road, water, cable, pipeline and space. Transport is

    important because it enables trade between people, which is essential for the development of

    civilizations.[1]

    Pipeline transport sends goods through a pipe; most commonly liquid and gases are sent. Short-

    distance systems exist for sewage, slurry water and beer while long-distance networks are used for

    petroleum and natural gas.

    A water pipeline will pump water from a large source and transfer it across a great distance to

    areas in need. Water pipelines are large in diameter and the purpose is to pump without causing

    erosion.[2]

    Figure 1. Water pipeline

    Friction loss is the loss of energy or head that occurs in pipe flow due to viscous effects

    generated by the surface of the pipe. Friction loss is considered as a major loss and it is not to be

    confused with minor loss which includes energy lost due to obstructions.

    This energy drop is dependent on the wall shear stress between the fluid and pipe surface. The shear

    stress of a flow is also dependent on whether the flow is turbulent or laminar. For turbulent flow, the

    pressure drop is dependent on the roughness of the surface, while in laminar flow the roughness effects

    are negligible. This is due to the fact that in turbulent flow, a thin viscous layer is formed near the pipe

    surface, which causes a loss in energy, while in laminar flow the viscous layer is non-existent. [3]

    In the present report will be calculated all parameters for dimensioning in the first row a water

    pipeline, then an oil pipeline. Flow type, pressure profile and different parameters influecing the

    pressure profile will be presented.

  • 4

    I. WATER PIPELINE

    The case study is done on a waterworks pipeline which has to serve a city of 100,122

    inhabitants. The pipeline is coming from a natural source situated in mountains, serving the city

    situated at the basis of the mountain.

    Figure 1. Water pipeline pathway

    Considering an average consumption of 24 m3/year/inhabitant, we will a need a water supply

    structure able to provide a water flow of:

    QH2O= 0,0762 m3/s

    Also, we will consider a flow variation of 4 m3/year/inhabitant, so we have to chose a proper

    diameter for the pipeline which will transport the water without any problem regarding the flow

    variation issues.

  • 5

    I.1. Geometry and elevation We will consider the distance from the delivery point and the city to supply of 130,9 km.

    Figure 2. Altrimetry Profile

    I.2. Water Properties We assume a constant temperature along the pipeline, which is not subject to seasonal changes.

    Also, we consider constant properties even with the temperature variations.

    Table 1. Water properties

    Propriety Value Unit

    Temperature 21 Density 1000 Kg/m3

    Viscosity 0,0015 Pa.s

    Vapor pressure 0,0087 bar

    0 22.8478 53.4188 78.3583 117.7788

    Heigh

    t [m]

    Distance [km]

  • 6

    I.3. Water pipeline sizing We will assume liquid velocities from 0.5 to 2 m/s with a spacing of 0.25 m/s. Then, according to the velocity interval assumed, we can calculate the diameter using following formula:

    D = !! !!!

    After calculating pipe diameter, we can choose from standards the commercial size of the

    diameter. Also, maximum allowable pressure can be calculated using data provided by the

    standardization table of commercial steel pipes.

    Table 2. Diameter calculation

    If friction is neglected and no energy is added or given, the total head H is constant for any

    point in the pipeline. But in the real systems, flow is creating always energy losses due to friction. The

    energy losses can be measured with two gauges along the pipeline.

    After choosing the commercial size of the steel pipes, we can recalculate the velocities and

    choose the diameters which give us a velocity in our considered range, regarding the flow variations.

    We will choose the last four diameters, keeping into account that one diameter is the same. = 4 !

    Table 3. Velocity calculation

    D [m] 0.440 0.360 0.311 0.279 0.254 0.235 0.220 D [in] 11.188 9.135 7.911 7.076 6.460 5.980 5.594

    D comercial [m] 0.502 0.423 0.340 0.300 0.261 0.261 0.219 D comercial [in] 12.75 10.75 8.63 7.63 6.63 6.63 5.56

    Wall thickness [in] 0.41 0.37 0.32 0.32 0.28 0.28 0.28

    Velocities Qmin [m3/s] 0.32086 0.45135 0.70034 0.89712 1.18839 1.18660 1.68544 Qnorm [m3/s] 0.38503 0.54162 0.84041 1.07654 1.42607 1.42392 2.02252 Qmax [m3/s] 0.44920 0.63189 0.98048 1.25597 1.66374 1.66124 2.35961

    D1 D2 D3 D4 D5

  • 7

    We must determine the type of flow we have in the pipeline and also the relative roughness.

    Re= vD

    For laminar flow regime Re < 2000, friction factor can be calculated, but for turbulent regime

    with Re>4000 are used experimentally obtained results.

    The relative roughness is the absolute

    roughness of the pipe compared with the diameter.

    The pipes are manufactured from steel, which has an

    absolute roughness of = 50 m. Internal absolute

    pipe roughness is actually independent of the size

    diameters. So pipes with smaller diameter will have a

    higher relative roughness, while the pipes with bigger

    diameter of the same material will have a lower

    relative roughness. On Moody Diagram friction factor

    is expressed in function of value of Reynolds number

    and relative roughness. Because relative friction is a

    function of diameter, we can observe that Reynolds

    number will reduce while the diameter and the

    friction number will increase.

    Figure 3. Moody Diagram

    The minimum pressure inside the pipe will be consider equal with the atmospheric pressure in

    order to avoid cavitation due to the bubble gas formed at vapour pressure. For calculating the

    maximum allowable operating pressure inside the pipeline, I will consider a design factor equal to 0.7:

    Pmax= 20.7stD Pmin= 1.01325 bar

  • 8

    I.4. Water pipeline pressure profile

    The first set of calculation is done in a system without pump or valves.

    If we use Bernoullis equation, assuming incompressible fluid, adiabatic conditions, we can calculate

    the pressure drop inside the pipeline.

    P= p + v22 +gH

    As I said before, the pressure drop due to friction in the pipeline can be determines with

    Fanning equation.

    P= f v22 LD The pressure profile equation without pump or valve is as follows; ! = ! + (! !) 8! !! (! !)

    The pressure profile was calculated using equation of pressure loss due to friction considering all

    assumed velocity and their corresponding diameters in equation above. First, I calculate pressure

    profile for the normal water flow using all the velocities from the considered range.

    Figure 4. Effect of velocity on pressure profile

    -150 -100 -50 0

    50 100

    0 20 40 60 80 100 120 140

    Pressu

    re [b

    ar]

    Distance [km]

    v = 0.5 m/s v = 0.75 m/s v = 1 m/s v = 1.25 m/s v = 1.5 m/s v = 1.75 m/s v = 2 m/s

  • 9

    I.5. Pumps and valves

    A pump is a device that moves fluids by mechanical action. Pumps consume energy to perform

    mechanical work by moving the fluid. They operate via many energy sources, including manual

    operation, electricity, engines or wind power, come in many size from microscopic for use in medical

    application to large industrial pumps.

    Pump performance calculations:

    Head(m) = !!!! + h+ !!!! P! + gH! + Pump head = P! + gH! + P! P! = g Pump head + g H! H! + (P! P!)

    We calculate the total energy of our profile in terms of head using the new parameters i.e.

    pressure loss due to friction and elevation !"!" =0 since water is to be delivered at atmospheric pressure. The ideal pump for any give pipe system will produce the required flow rate at the required pressure.

    The maximum efficiency of the pump will occur at these conditions. If a given pump is to work with a

    given system, the operating point must be common to each. In other words H=h at the required fl