Simplified model for heat transfer in cover gas of SNR 2 (GASMO-code)

A simplified model to determine the heat transfer from the sodium pool through the cover gas to the roof of SNR 2 has been developed and embodied in a code named GASMO. The code implies steady state conditions. The convective heat transferred from the sodium surface to the cover gas is balanced against that transferred from the gas to the roof ceiling and that transferred by convection loops into the gaps of the roof. A one-dimensional approximation for the flow of the gas is used to determine the gas velocity. The heat exchange equation is solved separately for each section and for each wall bordering the flow path using heat transfer coefficients for mixed convection. The sodium aerosols in the cover gas may be treated as transparent to the radiation between pool surface and the roof ceiling; optionally the scattering with or without absorption according to an empirical CEA-formula can be calculated. An intertwined iterative process is used to attain a numerical solution. The results of the calculation are the mean temperatures in the cover gas and the gaps, the mean circumferential temperature difference in the gaps and the heat exchanged with the different walls and surfaces. (author)