Large scale experimental investigation on storage tank breathing during sudden cold heavy rain event

In this study, unique large-scale experiments were performed, to measure the resulting breathing volume flow during cooldown through sprinkling on an air-filled horizontal storage tank with a volume of 191 m3. The tank had a length of 20 m, a diameter of 3.6 m and a weight of approx. 25 tons. Within 9 experiments in total, the sprinkling intensity, the sprinkling time, the initial temperature of the tank atmosphere, the sprinkling temperature and the breathing conditions with an inlet port of DN25 (open tank/closed tank/tank with valve) have been varied. The main objective was, to analyse local phenomena during cooldown of the tank that may impact the breathing volume flow. With this information it is possible to develop a breathing model including local phenomena, to prevent storage tanks from damage by inadmissible vacuum. Since current breathing models are derived for vertical tanks only, it was examined, if assumptions from literature are also applicable for horizontal tanks. In addition, it was verified whether the assumptions from the literature models are conservative for the sizing of tank breathing devices. The literature models from Fullarton et al. 1987) and Moncalvo et al. 2016) were compared to the experimental data.