Temperature during rapid depressurization of CO₂ in a pipe: ​ experiments and flow modelling

We analyse and model the temperature evolution during pipe depressurizations of CO₂ from the dense phase for four different initial temperatures between T0 = 4.6°C and T0 = 40°C. All the experiments showed an analogous temperature evolution, reaching similar minimum temperatures along the pipe. The warmer the initial temperature, the earlier dry-out and faster temperature recovery was observed. ​ We employ the homogeneous equilibrium model (HEM) and a two-fluid model (TFM) with different slip models in order to understand the observed data. The results indicate that the heat transfer changes significantly with different thermodynamic states for the CO₂. None of the tested models were able to fully describe the strong spatial and temporal gradients observed along the pipe during the depressurization.​