STEADY-STATE AND STABILITY ANALYSIS OF NATURAL CIRCULATION WITH FLUIDS AT SUPERCRITICAL PRESSURE

Natural circulation of CO 2 at supercritical pressure is addressed in the present paper in order to assess the capabilities of linear and nonlinear analysis in-house codes developed for studying steady-state and transient behaviour of natural circulation loops. In past activities, the models have been developed, taking into account also the effect of the presence of heating structures, and have been equipped with a low diffusion numerical scheme, in order to minimise truncation error effects. In the present work, available heat transfer correlations were introduced in order to properly simulate heat transfer to supercritical fluids, though the present state-of-the-art in the field does not yet allow to reliably simulate relevant effects as the deteriorated of heat transfer occurring when buoyancy effects become dominant. The obtained transient and linear stability analysis codes were applied to published experiments performed at the Bhabha Atomic Research Centre in Mumbai, India, making use of carbon dioxide as working fluid. Both steady-state conditions and transient behaviour were addressed, obtaining interesting data in comparison to experimentally observed behaviour.