Thermal and Bonding Shear Strength of Polymer Based and Cementitious Grouts for Pipe-in-Pipe and Geothermal Heat Pump Systems

Abstract

Pipe-in-Pipe (PIP) configuration is considered as a practical solution to deep-water oil production to prevent hydrate formation and paraffin deposition during the transportation of crude oil to production facilities. The grout material used in the annular space in the PIP configuration must be a good insulator. On the other hand for Geothermal Heat Pump systems (GHPS), the grout material has to promote the heat transfer between the heat exchanger and the surrounding media and hence must be a good conductor. Along with thermal conductivity aspect, these applications demand higher bonding shear strength for stress transfer as well as to minimize heat transfer because of contact resistance. Hence, there is interest in developing grouting materials with varying thermal and bonding properties for onshore and offshore applications. The overall objective of this study was to investigate the effects of various fillers on the thermal conductivity of a polyurethane based polymer grout for PIP application and cementitious materials for GHP systems. Hot wire method was used to measure thermal conductivity. Effect of fillers on the thermal conductivity of materials were quantified. The average transient thermal conductivity of polymer was 0.091 W/mK, which was reduced with the addition of microspheres and increased with the addition of aggregates and sand. Thermal conductivity of cementitious materials was studied with curing time and it was observed that thermal conductivity decreases with time. Along with cement paste and mortar, carbon fiber reinforced cement mortar (CFRCM), concrete, self compacting concrete (SCC) were studied. The effect of adding bentonite on the thermal properties of SCC was investigated.