A distributed heat transfer model for thermal-hydraulic considerations in sewer networks

Abstract

Thermal-hydraulic considerations in urban drainage networks are essential to utilise available heat capacities from waste- and stormwater. However, available models are either too detailed or too coarse; fully coupled thermal-hydrodynamic modelling tools are lacking. To accurately predict water-energy dynamics across an entire urban drainage network, we suggest the SWMM-HEAT model, which extends the EPA-StormWater Management Model with a heat-balance component. This enables conducting more advanced thermal-hydrodynamic simulation at full network scale than currently possible. We demonstrate the usefulness of the model by predicting temperature dynamics in two independent real-world cases under dry weather conditions. We furthermore screen the sensitivity of the model parameters to guide the choice of suitable parameters in future studies. The results of our study shows that sewer temperatures are particularly sensitive to soil temperature, sewer headspace temperature and humidity under specific conditions. Comparison with measurements suggest that the model predicts temperature dynamics adequately, with RSR values between 0.71 and 1.1. Simulation runs were generally fast; a five-day period simulation at high temporal resolution of a network with 415 nodes during dry weather was completed in a few minutes. Future work should assess the performance of the model for different applications and perform a more comprehensive sensitivity analysis under more scenarios. To facilitate the efficient estimation of available heat budgets in sewer networks and the integration in urban planning, the SWMM-HEAT code is made publicly available.