A fundamental model based on thermal balances for core oil temperature and wax layer development with axial distance in a pipe transporting heated oil

Abstract In this paper, we make the next fundamental extension to the thermal model introduced in Needham et al. (QJMAM 67:93–125, 2014) and Mason et al. (JEM 131:7, 2021) for considering the formation and structure of a precipitated wax layer on the externally cooled interior wall of a straight circular pipe transporting heated oil. Specifically we consider the key mechanisms allowing for axial variation in core oil temperature from the pipe inlet, and its subsequent, and principal, influence on the formation and structure of the wax layer on the cooled interior wall of the pipe as axial distance from the pipe inlet increases. A detailed analysis of the implications of this model is made, and illustrative numerical examples are presented. This determines that the model captures the key features of the axial development of wax layers as seen in the field measurements recorded from the Heimdal Brae De-Waxing Operation and reported, amongst other data, in a Statoil PPSA Seminar in 2013 by Fahre-Skau et al.