Comparison of One-Dimensional and Quasi-Two-Dimensional Friction Models for Hydraulic Transient Response and Energy Dissipation in Viscoelastic Pipelines at Different Water Temperatures

Abstract In chemical process systems, high-density polyethylene (HDPE) piping is widely used for conveying thermally conditioned liquids because of its corrosion resistance and operational flexibility; however, its pronounced viscoelastic response during hydraulic transients can strongly affect pressure regulation, process safety, and pipeline integrity, particularly under temperature-varying operating conditions. The temperature-dependent evolution of viscoelastic parameters, the differences between transient-flow models, and the associated energy-dissipation mechanisms remain insufficiently clarified for chemical engineering applications. In this study, transient-flow experiments in HDPE pipes at 20–40 °C were combined with numerical simulations using a one-dimensional quasi-steady friction model and a quasi-2D (quasi-two-dimensional) friction model. The first-peak occurrence time remained nearly constant at 0.1179 ± 0.0129 s, while the later response, particularly the third peak, was progressively delayed. The identified effective creep-compliance parameters increased overall with temperature and exhibited finite model-conditional admissible ranges. Model-based energy decomposition indicated that the calculated temperature-induced increase in total dissipation was governed primarily by the viscoelastic term WP, whereas the calculated frictional term Df varied comparatively little; the kinetic–elastic energy-exchange process also became shorter at elevated temperatures. The quasi-two-dimensional model did not yield a uniformly lower pressure-history RMSE, but its radial resolution of axial velocity and near-wall shear revealed model-dependent Df/WP partitions that became pronounced at 35–40 °C. These findings clarify the coupled effects of temperature and viscoelasticity on transient flow in polymer process pipelines and provide a mechanistic basis for model selection, pressure-surge control, and the safe operation of chemical-engineering piping systems.