Validation of Two-group IAT (Interfacial Area Transport) Model for Droplet Field in SPACE Code

In SPACE (Safety and Performance Analysis Code for Nuclear Power Plant) code model, interfacial area concentration of the droplet field is of importance for estimation of the interfacial momentum and heat transfer between the droplet and the vapor phases. In this study, to enhance the prediction capability for the interfacial area and reflect the dynamic behavior of interface between the droplet and the spacer grid, IAT (Interfacial Area Transport) model was implemented in the SPACE code. Two-group IAT equation model was implemented in the SPACE code to mechanistically estimate dynamic behavior of the interfacial area for the droplet. The breakup of the droplet by impacting on the spacer grid was considered as major source terms in the equation. Variation of the interfacial area for the large and small droplets could be quantitatively estimated with separated transport equations for two groups. The IAT model for the droplet field in the SPACE code was validated with comparison to FLECHT-SEASET experiment. The calculation result proved that the droplet IAT model has estimated the dynamic behavior of the droplet interfacial area and reduced the vapor temperature by increasing the amount of the vaporization. For the further study, development of more precise model for the droplet breakup is required with comparison of the droplet size to the test result