MODELAGEM TRANSIENTE DA TRANSFERÊNCIA DE CALOR EM DUTOS DE PETRÓLEO OU GÁS, TERMICAMENTE ISOLADOS / TRANSIENT HEAT TRANSFER MODELING OF THERMALLY INSULATED OIL OR GAS PIPELINES

AUTOR(ES)

JHOANY JHORDANN BARRERA ESCOBEDO

DATA DE PUBLICAÇÃO

2005

RESUMO

Subsea pipelines are employed not only for production but also for transportation. In both situations, warm oil loses heat to the cold sea water. The heat loss to the ambient is controlled by means of thermal insulation, which is designed for steady state operations. During shutdowns, the stagnant fluid in the pipeline loses heat to the cold surrounding, eventually reaching some critical temperature. As a result, several problems can occur, such as formation of hydrates or deposition of high molecular weight paraffins on the inner wall of the subsea line, which can lead to flow line blockage and production shutdown. Restart of very viscous fluid after shutdown is also critical, since viscosity increases significantly with the reduction of the temperature. This work presents an analysis of the influence of the pipe wall thermal capacitance on the transient behavior of heavily insulated lines. The heat loss from the pipeline is determined, by solving the transient heat conduction equation for the pipewall layers, utilizing a simple one-dimensional model in the radial direction. The finite volume method is employed to solve the transient flow inside the pipeline, from the time instant that a valve at the end point of the line is closed, coupled with the pipe wall thermal transient. Comparisons with the prediction of commercial softwares were performed and their limitations are addressed. Numerical results obtained for flows of both liquid and gases, considering and neglecting the thermal capacitance, revealed that accounting for the thermal capacity of the wall is relevant to the determination of cooldown times

ASSUNTO(S)

cooldown capacidade termica linhas submarinas resfriamento thermal model subsea pipelines linhas submarinas transiente termico heat capacity sub-sea lines

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