Implementation of a transmission line model for fast simulation of fluid flow dynamics

Abstract

n implementation of a lumped and 1-dimensional pipeline model for simulation of fast pressure and flow transients such as water-hammer effects is presented. It is an extension of the classical Transmission Line Model (TLM), a transfer matrix representation of a pipeline, relating pressure and volume flow rates at the extremities of a pipeline. The proposed model has extended previous work in different aspects. The extensions were developed for the detailed operational investigation of a pipeline for the transport of carbon dioxide from a carbon capture plant to a suitable location for the geological storage of supercritical, dense phase carbon dioxide. A lumped temperature model, derived as the TLM model by integrating the distributed dynamics, has been added to describe the effect of heat losses in long pipelines. A dynamic friction model that is explicit in the medium and pipeline characterisitcs has also been included. Finally, it is shown that, with simple adjustments, the model can reasonably well describe the pressure dynamics in turbulent flow conditions. Some simulations have been carried out to compare the performance of the proposed model to the one from the Modelica Standard Library, and the results were also compared to measurement results from the literature. The resulting model has become useful for a wide variety of engineering applications: pipelines for gas and oil, district heating networks, water distribution networks, wastewater systems, hydro power plants and more. In the lumped, constant temperature version, there are no discretization artifacts, and even in the discretized version taking into account spatial and temporal changes in temperature, discretization artifacts are much smaller than for the standard finite volume model. Moreover, the short simulation times make the model suitable for real-time applications.