Modelling the dynamic thermal response of turbulent fluid flow through pipelines

The transient behaviour of pipe systems is important in many forms of thermal system such as domestic hot water, building heating, cooling and district thermal networks. In this study, different approaches to modelling the dynamic thermal response of pipelines are investigated through applying three forms of discretized one-dimensional flow and heat transfer model. These were further compared with fully three-dimensional finite volume method (FVM) calculations. Firstly, the models were examined to predict the pipe thermal response considering the thermal capacity and longitudinal dispersion of turbulent fluid flow to step changes in the inlet temperature of a ideally insulated pipe. A model is proposed combining features of plug-flow n-continuously stirred tanks and treatment of the nodes to take into account the effect of thermal capacitance of the pipe wall as well as the convective heat transfer from the pipe outer surface. The results elucidated that the proposed model is not only able to capture the outlet temperature changes due to a step change in the very good agreement against the detailed 3D model but also offers advantages in computational cost compared with the 3D model. The proposed model can be simply implemented in dynamic system simulation tools. The model is to be extended to include dynamic ground heat transfer effects.