04 - Pipeline Flow and Thermal Analysis

Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of [email protected]

ENGI 8673 Subsea Pipeline Engineering

Lecture 04: Pipeline Flow and Thermal Analysis

2 ENGI 8673 Subsea Pipeline Engineering – Lecture 04© 2008 S. Kenny, Ph.D., P.Eng.

Lecture 04 Objective

To provide an overview heat transfer mechanisms and simple engineering tool to assess thermal performance in context of pipeline hydraulics


Heat Transfer MechanismsConduction

Direct contact•

Relatively inefficient

ConvectionFlow or circulation•

Natural or forced (advection)

RadiationElectromagnetic energyEmissivity•

Ability to absorb and radiate energy


Thermal EffectsFlow Assurance

Viscosity effects on pressure dropProcess facilitiesWax, asphaltene, hydrate formation

Material behaviourReduced strengthCorrosion ratesCreep

Mechanical designThermal expansionUpheaval, lateral buckling

Shut-in & start-up operationsFlow assuranceAxial walking, ratcheting


Liquid Hydrocarbon Viscosity


Heat Transfer – Conduction

Fourier LawQ ≡ heat loss per unit length (W/m)t ≡ time (s)k ≡ material thermal conductivity (W/m/K)S ≡ surface area (m2)T ≡ temperature (K)U ≡ heat transfer coefficient (W/m2-K)

S

Q k TdSt

∂= − ∇

∂ ∫Q TkAt x

Δ Δ= −

Δ Δ


Heat Transfer – Conduction (cont.)

Steady State ConditionsIntegrate per unit length•

Annular layer

•

Temperature gradient QT

r dr, ΔT

Q TkAt x

∂ ∂= −

∂ ∂Q UA T⇒ = Δ

2

1

2

ln

k TQrr

π Δ=

⎛ ⎞⎜ ⎟⎝ ⎠

2

1

1 2ln

kU A rr r

r

π⇒ = =⎛ ⎞⎜ ⎟⎝ ⎠



Multiple Layer SystemHeat transfer coefficient

Q UA T= Δ

1 2 3

1 11 1 1TU

RU U U

= =+ +∑

1 2 2

1 2 2

TA TQ r r r

k k k

Δ=Δ Δ Δ

+ + +…



Buried Pipelineri ≡ inside pipe radiusro ≡ outside pipe

radius in contact with the soil

21

1 1

cosh ln 1

soil soilburied

i i

oo o

k kUr rH H H

r r r

−

⎡ ⎤⎢ ⎥⎢ ⎥= =⎢ ⎥⎛ ⎞ ⎛ ⎞⎛ ⎞⎢ ⎥⎜ ⎟ ⎜ ⎟+ −⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦ ⎜ ⎟⎝ ⎠⎝ ⎠


Thermal Conductivity Parameters

Common Materials (W/m/K)Steel 45Concrete 1.2Soil 1.0–2.0Neoprene 0.26PP syntactic 0.15–0.20PU syntactic 0.10–0.15PU light foam 0.02–0.03


Heat Transfer Coefficient, U (W/m2-K)

Non-insulated Single Wall25 W/m2KBurial decrease U by ~1/3

Pipeline Bundle≈ 1.5–2.5

Insulated Pipe-in-Pipe≈ 3.0.–6.0

Insulated Pipe-in-Pipe≈ 0.5–1.0 Ref: McKechnie and Hayes (2003)

Ref: Geertsenand Ofredi (2000)


Steady State Thermal Profile

Parametersm – mass flow rate (kg/s)U – heat transfer coefficient (W/m2-K)Cp – specific heat capacity (J/kg-K)•

Oil ≡

1800 and Gas ≡

2500

T0 – ambient temperature (°C)T1 – pipeline temperature at section 1 (°C)T2 – pipeline temperature at section 2 (°C)

( )-

= - +2 1 0 0p

U D dxmCT T T e Tπ

[ ]ρ=m Q


Design Considerations

Ref: Maksoud (2004)


Design Considerations (cont.)

Ref: Maksoud (2004)


Example 4-01

Calculate the heat loss coefficient (U) for an in-air, single wall, steel linepipe with no external or internal coatings.

Do = 508mmt = 12.7mmk = 45 W/m/K

22

1

451 1 3636

0.2413 0.254lnln0.2413

Wk WmKU

r m m Kmrmr

⎛ ⎞⎜ ⎟⎜ ⎟= = =⎜ ⎟⎛ ⎞ ⎛ ⎞⎜ ⎟⎜ ⎟ ⎜ ⎟

⎝ ⎠⎝ ⎠⎝ ⎠


Example 4-02

Compare heat transfer coefficientsNon-insulated pipeline versus pipeline with a 50mm concrete coating


Example 4-03Calculate the heat loss coefficient (U) for the following pipe-in-pipe system

Inner Pipe•

Do = 406.4mm

•

t = 17.5mm•

k = 45 W/m/K

Polypropylene Foam•

t = 45mm

•

k = 0.22 W/m/KCasing•

t =12.7mm

•

k = 45 W/m/K


Example 4-03 (cont.)Example 4-03

Determine U-value for multiple layer system

DEFINED UNITS

BBL 42gal:=

INPUT PARAMETERS

Pipeline System

Nominal Outside Diameter - Inner Pipe Do 406.4mm:=

Nominal Wall Thickness - Inner Pipe t1 17.5mm:=

Conductivity - Inner Pipe k1 45 W⋅ m 1−⋅ K 1−

⋅:=

Nominal Wall Thickness - PP Foam t2 45mm:=

Conductivity - PP Foam k2 0.22W m 1−⋅ K 1−

⋅:=

Nominal Wall Thickness - Outer Pipe t3 12.7mm:=

Conductivity - Outer Pipe k3 45W m 1−⋅ K 1−

⋅:=


Example 4-03 (cont.)


Reading List1.

Bell, J. and Geertsen, C. (2002). The McPIPETM

Extended Cooldown

System. Presentation, Deepwater Offshore Techology, 14-16 November, 20p.

[2002_Bell_McPipe_Extended_Cooldown_System.pdf]

2.

Geertsen, C. and Offredi, M. (2000). Highly Thermally Insulated and Traced Pipelines for Deepwater. 12th

Deep Offshore Technology Conference, New Orleans, USA, 13p.

[2000_Geertsen_Insulated_Traced_Deepwater_PL.pdf]

3.

Loch, K.J. (2000). Deepwater Soil Thermally Insulates Buried Flowlines. Deepwater Technology, www.pipeline.com, August 2000.

[2000_Loch_Deepwater_Soil_Insulation.pdf]

4.

Maksoud, J. (2004). Petro-Canada Investigates Flow Assurance Challenges. Offshore, pp.112-113.

[2004_Maksoud_ FA_Challenges_Petro_Canada.pdf]


ReferencesGeertsen, C. and Offredi, M. (2000). Highly Thermally Insulated and Traced Pipelines for Deepwater. 12th Deep Offshore Technology Conference, New Orleans, USA, 13p.Loch, K.J. (2000). Deepwater Soil Thermally Insulates Buried Flowlines. Deepwater Technology, www.pipeline.com, August 2000.Maksoud, J. (2004). Petro-Canada Investigates Flow Assurance Challenges. Offshore, pp.112-113.McKechnie, J.G. and D.T. Hayes (2003). Pipeline Insulation Performance for Long Distance Subsea Tie-backs. 14p.

04 - Pipeline Flow and Thermal Analysis

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