Durability of District Heating Pipelines Exposed to Thermal Aging and Cyclic Operational Loads
Publication: Journal of Pipeline Systems Engineering and Practice
Volume 12, Issue 1
Abstract
Fourth generation district heating networks (4GDH) must be designed for future energy systems, integrating renewable volatile energy sources, with lower operation temperatures, and consequent reduction of heat losses and increased energy efficiency. The lower levels of operating temperature and the greater amount of cyclic loading, influence aging, and the service life of 4GDH pipelines, differently from traditional district heating (DH) networks, and thus require proper investigation of the system response at the cross-sectional level. To evaluate the material durability of 4GDH pipelines, we have analyzed the behavior of the service steel pipe, the insulation foam, and their adhesive interaction, using an innovative analytical and experimental procedure. This paper describes the influence of traditional and future operational loading conditions on the performance of preinsulated bonded single-pipe systems, representing the majority of currently operating DH pipelines. The performed fatigue analysis of the steel service pipe showed that the lifetime of 4GDH pipelines is expected to increase because of the lower operating temperature, and the low impact of thermal loading volatility in the network, compared to conventional DH. The accelerated aging tests of DN pipes demonstrated that the combined effect of cyclic mechanical loading and thermal aging accelerates the rate of chemical degradation of the PUR foam, leading to a faster deterioration of the mechanical adhesion strength. The shear strength tests of naturally aged DH pipes revealed that, besides the initial pipe system characteristics and aging period, the residual shear strength of the polyurethane (PUR) foam depends on the temperature history, decreasing with the level of operating temperature and amount of fluctuation. The obtained results give a better understanding of the performance of traditional and 4GDH pipelines in operation that need to be appropriately considered in the engineering design standards of DH networks toward a more sustainable and energy-efficient infrastructure.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Some or all data, models, or code used during the study were provided by a third party. Direct requests for temperature data, measured from fourth generation district heating in Chemnitz, in Germany may be made to the provider as indicated in the Acknowledgements.
Acknowledgments
The work presented herein is part of the research project “Effects of loads on asset management of the 4th generation district heating networks” funded by the International Energy Agency Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power (IEA DHC), that is greatly acknowledged. The authors would like to thank Prof. Thorsten Urbaneck from the Department of Mechanical Engineering at the Chemnitz University of Technology, and Mr. Thomas Göschel from inetz GmbH, for providing helpful guidance and information on the collected temperature data from 4GDH. Thanks are extended to Powerpipe Systems AB, Gothenburg Energy, Hafslund Varme AS, Jönköping Energy AB, Vattenfall AB, for the valuable discussions, manufacturing of pipes and support ideas. Moreover, the authors would like acknowledge the colleagues at RISE, especially Mr. Anders Persson for helping on experimental set up. Thanks are extended to Mr. Eun Sick Kang from the Pipeteckorea Co. Ltd., for the cooperation in the axial shear strength test of naturally aged pipes in Korea.
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Published In
Journal of Pipeline Systems Engineering and Practice
Volume 12 • Issue 1 • February 2021
Copyright
© 2020 American Society of Civil Engineers.
History
Received: May 16, 2020
Accepted: Aug 28, 2020
Published online: Nov 12, 2020
Published in print: Feb 1, 2021
Discussion open until: Apr 12, 2021
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