Heat transfer of air expansion in surge vessels using large eddy simulation (LES)

Abstract

Surge vessels are important for pipeline system resilience, especially for large drinking water mains. Optimal modeling of the heat transfer in these vessels in, often low-dimensional, hydraulic models can enable an optimal design and reduce material usage. In this work, Large Eddy Simulation (LES) of heat transfer for air expansion in surge vessels is performed and a 0D numerical model is devised. The flow as found in the LES is elaborately described. Four cases (one small scale and three full scale) are analyzed. The LES simulations and the 0D model agree very well for the volume average air temperature, hinting at relatively conventional convective heat transfer at the vessel walls, despite downflow and stratification in the bulk. A remarkable observation regarding the behavior of the polytropic number with time is made. Furthermore, the temperature is compared to experimental measurements for two different vessels. The comparison with the experimental data for the first vessel shows a large difference in temperature at sensor locations, whereas the comparison with the experimental data for the second vessel agrees up to 10% of the temperature drop, where both numerical models (the LES and the 0D model) predict a lower temperature than the physical measurement indicates. The differences are discussed. Future work will focus on modeling condensation.