Summary
Objective
To demonstrate that an insulation system incorporating a low thermal conductivity screen mesh between a pipe and an interior liner can be an effective passive thermal insulation solution for deepwater flowlines and risers.
Approach
It has been established that a thermal resistance (due to the metrology of the contacting surfaces) is created an interface between two materials, in this case a pipe and a liner. If the two contacting surface are further separated by a screen wire or mesh at the pipe and liner interface, then a higher thermal interface resistance will result, which will significantly increase the resistance to thermal transport characteristics. The screen wire reduced the heat transfer by restricting the path available for conduction and forms a stagnant air gap to minimize radiation and convective heat transfer. Heat transfer can be further reduced by adding a Mylar film to the exterior of the liner and the interior of the pipe. Such an Interstitially Insulated Coaxial Pipe is illustrated below.
Interstitially Insulated Coaxial Pipe may offer a thermally superior, cost effective and robust insulation system for deepwater pipelines, flowlines, and risers.
Experiments will be performed to verify the thermal resistance properties and the influence of selected variables (e.g., mesh size and material, contact pressure, air or vacuum in the interstices, addition of Mylar film layers) throughout a range of temperatures.
Deployment of Results
The results of these experiments are expected to prove the effectiveness of Interstitially Insulated Coaxial Pipe as an insulation system for deepwater pipeline, flowlines, and risers. Results will be confidentially disclosed to interested parties (pipe and riser manufacturers, oil and gas companies) to determine interests in potential application of this technology and needs for further testing. It is expected that, eventually, this technology will be commercially licensed with a royalty bearing agreement, either exclusively or non-exclusively, via the TAMU System Technology Licensing Office.
Project Plan
Scope of Work: Experiments will be conducted to determine the thermal properties of Interstitially Insulated Coaxial Pipe as a means to insulate pipe under a realistic temperatures conditions. The experimental arrangement is shown below.
Phase 1 The test matrix will consist of the measurement of thermal joint resistance for several size wire screens (Meshing size) as a function of joint interface pressure (e.g., 10 to 500 psi) and mean interface temperature (e.g., 32oF to 175oF). An appropriate pressure and temperature interval will be chosen between the two bounding limits so that the full effects on thermal joint resistance can be elucidated (e.g., the transition from contact to bulk thermal resistance dominance which would control the overall joint resistance). A minimum of three mesh numbers (e.g., # of openings per lineal inch) will be investigated along with two different metallic material types (these materials constitute the bulk wire screen construction). This portion of the experimental study will also include the surface characterization (e.g., metrology) and measurement of thermophysical properties for either X-60 or X-80 pipe steel. These properties will be needed to enumerate the heat flux rate and temperature drops across the joint. Machined flux meters made from X-60 or X-80 will help achieve these computed parameters.
Phase 2 Laboratory experiments on a small scale prototype IICP will be conducted to validate the IICP concept in the prototype geometry (i.e. pipe versus coupon), and demonstrate its effectiveness as a means to insulate deepwater pipelines, flowlines, and risers. A small prototype IICP (diameter = 6 -12 inches, length = several feet) will be built. The IICP design parameters (wire screen diameter size, mesh number and Mylar film thickness, joint interface pressure) will be based on learnings from the Phase I experiments. A small test loop will be fabricated and will include the IICP section, hot and cold reservoirs to simulate subsea water temperatures (~34 degrees F) and hot oil temperatures (~ 175 degrees F), pumping apparatus, thermal sensors, volumetric flow sensors, and data acquisition instrumentation. The experimental loop arrangement is shown below with the IICP technology (Fig.4). The thermal resistance of the IICP will be determined under conditions representing (1) steady state flow of hot oil through an operating pipeline, and (2) transient conditions following a pipeline shut down to demonstrate the change in thermal resistance of a pipeline with time following the flow stoppage.
A model to estimate the thermal performance of the IICP system for pipeline, flowline, and riser examples under realistic conditions will be developed and calibrated with experimental data. The model will be used to assess the performance of the IICP system in a variety of steady flow and transient shut-down scenarios. Results will be used to determine the needs for further development and optimization of the IICP system and to illustrate ICCP technology to interested parties in the oil and gas industry.
Efforts will be made to engage the oil and gas industry for input and interest in the continued development and testing of IICP technology. Manufacturing methods will also be addressed.
Phase 3: Further experiments will be conducted to optimize the thermal insulating properties of the IICP to insulate pipe under a realistic temperatures and conditions. The optimization of the IICP parameters could include the (1) Mylar film thickness; (2) screen wire diameter mesh size, and material; and (3) use of insulation on the pipe exterior to provide additional insulation if needed. Manufacturability would also be investigated through discussions with industry and contractors to determine the impact of manufacturability and installation needs on the IICP parameters.
Phase 3 would also include fabricating a larger scale prototype pipe and testing in a thermal and flow/thermal loop to further confirm the IICP system thermal performance under field conditions and the manufacturability of IICP pipe.
Anticipated Results: The data will be presented as a family of curves which will feature the joint thermal resistance as a function of applied interface pressure and mean interface temperature for the various configurations. These curves can be incorporated as design tools for the fabrication of a metallic sleeve which will encompass the wire screen for enhancement of thermal resistance in Interstitially Insulated Coaxial Pipe for offshore ultra deep water applications. The effectiveness of the IICP pipe would be demonstrated to the industry, and its use would be licensed to interested parties.
Related Publications
Dong (Keun) Kim, Carlos Silva, Egidio (Ed) Marotta, and Leroy (Skip) Fletcher, “Characterization of Wire Screen Insulation for Deep Water Pipe Applications”, Proceedings of the 2006 AIAA/ASME Joint Heat Transfer Conference, June, 5-8, 2006, San Francisco, California .
“Characterization/Modeling of Wire Screen Insulation for Deep-Water Pipe”; Dong (Keun) Kim, Egidio (Ed) Marotta, and Leroy (Skip) Fletcher, Journal of Thermophysics and Heat Transfer, AIAA, Sept. 2006, accepted.
