Experimental investigation on condensation inside of storage tanks during rapid cooling in a heavy rain event

Abstract

Experiments have been performed on a 2.6 m3 gas and liquid filled vertical storage tank at ambient conditions that has been cooled with cold water. The breathing volume flow and main parameters, such as gas and wall temperatures, condensate masses generated and tank differential pressure have been measured. The experiments have been performed with dry air, water and methanol as storage media. The aim is to obtain validation data for future models and correlations for cooling of storage tanks. Additionally, the impact of fog formation in the tank atmosphere, dropwise and film condensation and rain intensity during heavy rain events on the maximum breathing flow rate have been investigated. As a result of the analysis of physical phenomena during the cooling of the tank, an increase in the maximum breathing volume flow for storage media with increasing vapor pressure was observed. Strong fog formation was visible in all experiments with condensable liquids. In contrast to alcoholic storage media, dropwise condensation on the wall is expected when storing aqueous media. Rain intensity and heat transfer models from literature were examined regarding the sizing of tank breathing valves. Deviations between experimental data and a typical manual calculation model for sizing of tank breathing devices varied between 13% and 143%. The validation on the experimental data clearly showed that current models are not suitable for describing the breathing volume flow rate that occurs during sudden heavy rain events with sufficient accuracy.