Phase Change Materials for Subsea Pipeline Insulation

Photo of Harrison Xue, Chieh Yin, David Zummo Students: Harrison Xue, Chieh Yin, David Zummo

Sponsor: Shell Global Solutions

Date: Fall 2010

Requirements:
Constraints on insulation design include stress limits from the properties of the materials involved and manufacturing feasibility. The thermal performance of the insulation must meet the requirements of any subsea pipeline. Namely, the composite insulation must have enough thermal resistance to keep the petroleum above the desired arrival temperature along the entire length of flow. Under these conditions, the insulation designs are compared to find the most cost-effective method of providing a desired cool-down time.

Problem:
Subsea petroleum flow line insulation design represents a complex engineering design challenge. Two thermal properties of the insulation must be balanced. Under steady state conditions, low thermal conductivity is necessary to keep the crude oil above the desired arrival temperature as it flows from the reservoir to the riser. Under transient conditions when the flow is stopped during a shut down, the insulation must provide enough heat capacity to maintain the crude oil above the critical temperature at which blockages form.

Solution:
Heat transfer, stress tolerance, manufacturing feasibility, and economic effectiveness aspects for eleven concepts were analyzed and benchmarked to find the best design for incorporating phase change materials (PCMs) in the insulation system. The goal was to identify a design that balances thermal resistance with heat capacity to perform under both steady state and transient conditions. The study centered on a heat transfer algorithm written in MATLAB that simulates the insulating performance of the design concepts and benchmarks them against existing solutions. We recommend a syntactic PCM polypropylene composite that can be layered under current composite insulators. This system provides a balance between incorporating solid PCMs, which offer high efficiency for storing heat but also have many manufacturing challenges, and encapsulated PCM, which in its own layer presents unique fabrication obstacles, resulting in higher initial cost. Although further research is necessary, PCMs represent a promising addition to the arsenal of technology necessary to allow safe efficient production of increasing remote petroleum reservoirs.

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