ABSTRACT

This paper summarizes the results of the experiments conducted in a cylindrical horizontal test section called the "pulser" (L/D = 2), where condensation implosion events can be initiated in a controlled and reproducible manner It is shown that such event can be generated solely by modulating the degree of turbulence in the stratified liquid region. The turbulence level is influenced by the rate of subcooled water supply into the pulser volume filled by saturated vapor. The rising and expanding surface leads to an increased condensation rate, vapor flow and condensation-induced shear initiate surface waves and when these exceed a critical growth rate a complete interface disruption leading to a rapid condensation implosion event occurs. The presented experimental results show that the vapor-water interface perturbation required for the initiation of such condensation implosions can be generated internally and depends solely on the rate at which liquid is supplied to the pulser. Four distinct condensation modes have been identified. The influence of residual amounts of non-condensables during development of the condensation implosion event is analyzed. It is shown that the influence of non-condensables is of an equivalent importance as the liquid side turbulence that is modulated by the rate of liquid supply. Based on the experimental results the sequence of physical phenomena that lead to a condensation implosion event is described and the heat-transfer coefficient in different condensation modes is estimated and compared.