An experimental study on geysering phenomena induced by buoyancy in a heating system

The geysering phenomenon caused by the interaction of buoyancy of vapor and resistance of piping, include initial heat up process, intermittent vapor venting, periodically significant fluctuation of flow parameters and alternative flow patterns, influenced by the factors, including different height of upper plenum, diameter of vertical column, initial subcooling, coolant inventory and heating power, which is experimentally investigated by using a small scale experiment facility. The experimental results show that the geometry of the rising pipe and heating power are the key influence factors based on quantitative statistical analysis of the experimental data, and the geysering phenomenon is more obvious under greater ratio of height to diameter of vertical pipe and larger heating power. A dimensionless number GEY defined by the normalized pressure difference to relative temperature difference ratio of the vertical column is proposed to identify the venting and reflux in the geysering and to determine the period of geysering, and the reciprocal GEY crest factor can be the indicator of geysering. Based on the mechanism analysis, the system internal heat models are developed to obtain the heat transfer capacity of the system, and the results of which agree with the experimental data.