Steady-State Thermoelastic Analytical Solutions for Insulated Pipelines

M Fraldi,A Cutolo,L Nunziante,L Esposito,F Carannante

doi:10.1155/2016/6274509

M Fraldi, A Cutolo + Show 3 more

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https://doi.org/10.1155/2016/6274509

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Abstract

A steady-state thermoelastic analytical solution for a multilayer hollow cylinder, composed of an arbitrary number of phases and subject to both radial pressure and temperature gradient, is presented. By assuming each phase to be homogeneous and thermally isotropic and by varying the mechanical and thermal constitutive parameters, a sensitivity analysis has been performed with the aim of finally applying the study to the mechanical behaviour of an industrial pipeline composed of three phases (steel, insulating coating, and polyethylene) under the action of the above-mentioned load conditions. By making reference to a classical Hencky-von Mises criterion, the stress profiles along the thickness of the layers have been carried out, also localizing the onset of plasticity as a function of the temperature variations, material properties, and geometrical features characterizing the composite structure of interest. At the end, some numerical results of practical interest in the engineering applications have been specialized to three different insulated coating materials (expanded polyurethane, laminate glass, and syntactic foam), to highlight the cases in which thermal properties and loads can significantly interfere with the mechanical response in pipes, in terms of stresses, in this way suggesting possible strategies for avoiding unexpected failure and supporting the optimal structural design of these systems.

Highlights

In the last years, a growing demand for insulated pipes operating at higher temperatures has addressed a need of insulation materials able to withstand thermal degradation and physical stress
De facto, multilayered insulated pipelines can be considered as laminate composites
Shao [9] derived analytical solutions of a circular hollow cylinder composed of different homogeneous fictitious layers in the radial direction, finding mechanical and thermal stresses for the two-dimensional thermoelastic problems

Summary

Introduction

A growing demand for insulated pipes operating at higher temperatures has addressed a need of insulation materials able to withstand thermal degradation and physical stress. Either inadequate thickness or deterioration of existing insulation causes high energy consumptions, so that retrofitting or reinsulation techniques, strictly related to the development of higher performances at lower prices insulating materials, are becoming a very attractive energy saving method In this framework, multilayer insulated pipes could be a suitable alternative, in which different materials can be used to enhance energetic performances of pipelines. Shao [9] derived analytical solutions of a circular hollow cylinder composed of different homogeneous fictitious layers in the radial direction, finding mechanical and thermal stresses for the two-dimensional thermoelastic problems. By using a multilayered approach based on the theory of laminated composites, a steady-state thermoelastic analytical solution for a multilayer hollow cylinder, composed of an arbitrary number of phases and subject to both radial pressure and temperature gradients, is proposed. A numerical example is reported considering the insulate coating composed of expanded polyurethane, laminate glass, and syntactic foam

Basic Equations for the Steady-State Problem

Numerical Example of an Insulated Pipeline Subject to Temperature Gradient

10 Case 3