Thermal Analysis of Buried Insulated Pipes

Abstract

This paper evaluates the temperature distribution along the pipe–soil interface of a polyurethane insulated steel carrier pipe with a polyethylene jacket used to transport up to 160 °C hot oil emulsion in conditions typically encountered in the Boral forests of Canada. The evaluation includes a parametric study using finite element models of these buried pipes and the development of a pipe–soil interface temperature relationship, to quantify the dependence on insulation thickness, pipe cover depth, carrier pipe diameter, and emulsion temperature. The derived temperature along the pipe–soil interface follows a sinusoidal distribution with the maximum temperature occurring at the bottom of the pipe and the minimal temperature at the top of the pipe as heat is conducted to the cooler-free ground surface. The benefit of this analytical expression is that classical heat transfer analysis can now be utilized to evaluate similar systems as the coupling with the soil has now been explicitly stated for variations in pipe diameter, cover depth, insulation thickness, and emulsion temperature. The paper also discusses the usage of this pipe–soil interface temperature relationship in the design of insulated pipes and provides some design guidelines for these pipe systems.