Progress Reports: December 2005 June 2005 December 2004
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.
ANTICIPATED PROJECT DURATION: 1 year
PROJECT PLAN FOR YEAR 1 (2004-2005):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 In addition, once the measurements have been completed with bare contacts between the metallic substrates (in this case X-60) and wire screen (e.g., either Stainless Steel or other suitable metal), then a coated, reflective polymeric film such as Mylar XMC110 or Mylar MC2 with be introduced in conjunction with the wire screen. Both these Mylar films have a vacuum deposited aluminum layer on one side and over-coated on both sides with a heat sealable copolymer. The introduction of the Mylar film will add an additional thermal barrier, in this case to radiation thermal transport, and thus decrease the overall thermal energy transport across the joint.
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.
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): Dr. Ed Marotta, Dr. L. Fletcher
Date: June 2005
Project Title: Interstitially Insulated Coaxial Pipe
MMS Project: 509 TO Number: 35663
PI: Ed Marotta
COTR: Mik Else
Estimated Completion Date: July, 2005
Project Description:
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 pipelines, flowlines, and risers.Progress:
Phase 1 of this experimental investigation to demonstrate the viability of Interstitially Insulated Coaxial Pipe (IICP) insulation system is complete. The thermal conductance of various wire meshes for the IICP system was measured for a range of parameters. The test matrix included wire meshes of several materials (Stainless Steel, Titanium, and Tungsten), a variety of mesh sizes, pressures at the mesh/pipe interface ranging from 10 - 500 psi, and interface temperatures ranging from 32 -175 F. The thermal conductance was also measured for the pipe material and a layer coupon of pipe-mesh-pipe to simulate the IICP insulation system. The pipe material was P110 4140 tubular steel.Results for the Stainless Steel wire meshes were previously reported. The thermal conductance for the Titanium and Tungsten coupons are shown in Figures 1 and 2. These thermal conductances are higher than those for Stainless Steel because of the larger thermal conductivities of these materials.
Finally, tests were run to demonstrate the performance of wire mesh as it would be inserted between a pipe and a liner. Coupons were formed by layering P110 4140 steel, SS 5 wire mesh, and P110 4140 steel to measure the thermal conductance of the mesh as it would be place between the pipe and liner walls. These coupons were 19 mm thick. A thin (12µ) Mylar film was included in one coupon. A coupon of solid P110 4140 steel that was 19 mm thick was also tested to represent the thermal conductance of the pipe without wire mesh. Results are shownin Figure 3. The thermal conductances for the coupons with the wire mesh are about 50X lower than the basic pipe. The addition of the Mylar film reduced the thermal conductance by an additional 20 percent. The lowest thermal conductance was 42.5 W/m2-K (5 SS mesh with Mylar)
The effective thermal conductivity coefficients computed from these results are shown in Figure 4. The thermal conductivity for the base pipe material is 45W/m-K. The use of SS mesh 5 with Mylar reduced the conductivity to 0.8. This compares very favorably with the present technology insulation systems now used by the industry.
Phase 1 has demonstrated the viability of a wire mesh as an effective insulation technology based on experiments using coupons. The screen wire reduces 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.
Phase 2 will extend this investigation to an actual pipe configuration to demonstrate the viability and examine the effectiveness for subsea pipelines, flowlines, and risers.
Reports & Publications: N/A
Date: December, 2004
Project Title: Interstitially Insulated Coaxial Pipe
MMS Project: 509 TO Number: 35663
PI: Ed Marotta
COTR: Mik Else
Estimated Completion Date: July, 2005
Project Description: 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. 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. Figure 1 shows a typical Interstitially Insulated Coaxial Pipe.
Fig. 1: Sketch of Interstitially Insulated Coaxial Pipe
Progress: Phase 1 of the experimental investigation, which consist of a test matrix where the measurement of thermal joint resistance for several size wire screens (Meshing size) and materials as a function of joint interface pressure (e.g., 10 to 500 psi) and mean interface temperature (e.g., 32oF to 175oF), is nearly completed. At present all testing for Stainless Steel wire screen have been completed with Titanium and Tungsten still to be conducted. The thermophysical properties as a function of temperature and metrology data for P110 (4140 Steel) have been measured. The results of the thermophysical properties of the steel are shown by Fig. 2. The thermal interface conductance of stainless steel wire-screens as a function of interface pressure and temperature is shown in Fig. 3. The results indicate that number of contacts and wire-screen diameter, which dictates the air gap between the two surfaces; have a large influence on the measured values. The experimental data does not include the coated, reflective polymeric film, which in conjunction with the wire screen will add an additional radiation thermal barrier.
Fig. 2 Thermal Conductivity Data
Fig. 3: Thermal Conductance Data
Modeling results have shown an improvement in overall thermal resistance (lower overall conductance) can be attended when the insulated coaxial pipe contains the additional interstitial wire-screen mesh. A comparison of the overall thermal conductance has been modeled for a design which incorporates the interstitial wire-screen with and without existing insulation material. Moreover, calculated effective thermal conductivities are plotted as a function of applied pressure for each mesh number and compared with present solution for deep sea applications. These trends are shown in Figs. 4-5, respectively.
Fig. 4 Overall Thermal Conductance with and without Mesh in Pipe with Insulation
Fig. 5: Ke for the Various Mesh Numbers as a Function of Pressure
Reports & Publications: N/A
