M Frogheri

Analysis of single-phase natural circulation experiments by system codes

In this paper, the results of simulations of natural circulation loop performance, obtained by Cathare and Relap codes, are reported. Both series of results are analyzed and compared with experimental data gathered in the MTT-1 loop, a rectangular natural circulation loop realized by DITEC at the University of Genova. Both Cathare and Relap codes, in absolute terms, show poor agreement with experimental data. At low power, the Cathare code shows a good capability to predict the steady state quantities, after the initial transient. On the other hand, no unstable behavior is predicted at each analyzed power level. The Relap code is able to show oscillating quantities, but not at the same power levels as in the experiments.

Influence of pressure drops on the behavior of a single-phase natural circulation loop: Preliminary results

Single phase natural circulation is of interest in various energy systems, including solar heaters, nuclear reactors, geothermal power production, engine and computer cooling. The present paper deals with an experimental study on the influence of pressure drops on the behavior of a single-phase natural circulation loop. In a simple rectangular loop (MTT-1) located at DITEC, three series of tests have been carried out, with localized pressure drops (orifices of 6 mm, 10 mm and 14 mm diameter in the vertical legs) and different power levels. The experimental data are analyzed and compared with previous results obtained with smooth pipes, demonstrating the stabilizing effect of the pressure drops on the overall behavior of the loop.