critical flow, critical flow rate, supercritical parameters, chocking characteristics, flow chocking


An interest of the problems of various thermophysical and hydrodynamic phenomena in the nuclear industry, determined by the real application in the field of analysis of the accident scenarios related to the loss of coolant accident. For the generic super critical water reactor the meaning of the problem at the initial stage of the critical flow process, is the existing of the uncertainty in the accepting boundary conditions to predict the flow characteristics. The article provides an analytical review of existing approaches for describing the critical flow phenomenon of the medium and to focus on the current predictive models. A description of the physical nature of such a phenomenon is provided. The scope of consideration includes information from the literature for single and two-phase flow, taking into account their physical basis and the assumptions made. The task of the work was to analyze the information found and to evaluate and update the data on the application of the models to obtain the critical characteristic. It was supposed to highlight the physical aspects and peculiarities of this phenomenon, as applied to the coolant at supercritical parameters. To formulate important requirements to the representative critical flow model for the possibility of its use in the system codes for evaluation of the nuclear safety problems of promising fourth generation nuclear reactors.


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