Alhowaity, Awatif
(2018)
*Solidification caused by under-cooling.*
Doctoral thesis, University of East Anglia.

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## Abstract

Many crude oils contain dissolved waxes that can cause significant problems,

such as blockage of pipeline, because of the precipitation and deposition of wax

particles during the production and transportation of the oil. The waxy oils

are transported through very long pipelines from warm natural reservoirs to

cooler conditions in the surrounding of the pipe. An important phenomenon

occurring during the under-cooling of the pipeline is the formation of solid

matter inside the pipe. The wax deposition is one of the most serious problems,

potentially restricting flow and plugging the pipe. Wax deposits begin to form

when the temperature is below the wax appearance temperature. We model

a particle's growth in the oil pipe once the temperature falls below the wax

appearance temperature. We determine the temperature distribution in the oil,

formulate and solve a self-similar problem of wax particle growth from a single

point. A corresponding initial boundary value problem is studied numerically

by a time-stepping numerical algorithm. The numerical algorithm is used

to compute the non-linear solution of an initial value problem of diffusion and

transport of wax towards the particle. The numerical solution is compared with

and validated against the self-similar solution derived for specific conditions.

Then the boundary value problem is formulated for the general case. A coupled

diffusion/flow problem of a single wax particle is formulated. An asymptotic

analysis is used to describe the motion and growth of the wax particle. At the

leading order, we consider a spherical wax particle and assume the velocity of

the particle to be close to the local velocity of the flow. The flow relative to

the wax particle is negligible in the leading order problem. In the first-order

correction problem, the wax particle is treated as spherical initially, and the

correction to the particle shape is caused by a small difference between the

wax particle speed and the speed of the local flow. We draw conclusions and

recommendation for further work at the end of this thesis.

Item Type: | Thesis (Doctoral) |
---|---|

Faculty \ School: | Faculty of Science > School of Mathematics |

Depositing User: | Jackie Webb |

Date Deposited: | 06 Aug 2018 10:41 |

Last Modified: | 06 Aug 2018 10:41 |

URI: | https://ueaeprints.uea.ac.uk/id/eprint/67960 |

DOI: |

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