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Il rapporto tecnico fornisce dettagli sulla specifica del “benchmark” LACANES, organizzato dalla OECD-NEA, dedicato alla validazione di codici di sistema per la simulazione dinamica di circuiti termoidraulici a metallo liquido. Ne illustra la metodologia, le caratteristiche dei codici utilizzati e i risultati degli studi preliminari dedicati alla valutazione dei coefficienti di perdita di pressione del circuito (Fase I). Alla prima fase del benchmark hanno contribuito sette istituti di ricerca di varie nazioni, anche extraeuropee.
Utilising HELIOS facility, a thermal-hydraulic benchmark study has been conducted for the prediction of pressure loss in lead-alloy-cooled advanced nuclear energy systems (LACANES). The motivations of this benchmarking are to gain a better understanding about thermal-hydraulic behaviour of lead-alloy-cooled system and furthermore to construct the good guidelines for thermalhydraulic modelling of it. Participants include representations of Germany, Italy, Republic of Korea, Russian Federation and IAEA. The LACANES benchmarking consists of forced convection (Phase-I) and natural circulation (Phase-II). This report describes the results of phase-I and recommendations for best practice for the pressure loss prediction for LACANES. Through the LACANES benchmarking phase-I, best practice guidelines for pressure loss prediction are established. Experimental tests are conducted to obtain the pressure loss in the core, the gate valve, the orifice, the heat exchanger region, and the expansion tank region. Predictions are also performed by participants using correlations from handbooks. Furthermore, to improve the prediction for the complicated geometry and to solve the uncertainty of prediction from correlations, CFD simulations for all components are conducted. Benchmarking regions consist of eleven components: core, orifice, gate valve, expansion tank, heat exchanger, 45o elbow, 90o elbow, tee-straight, tee-branch, gasket, and straight pipe. In the LACANES benchmarking phase-I, the following summary has been made:1. In the core region, the predictions based on handbook correlations have uncertainty. The Rehme correlation was used for the prediction of a pressure loss on the spacers but it underestimated the results, while orifice empirical correlation for spacers has the highest agreement with measured data. Two CFD simulations using the Star-CD® and the CFX® have shown good agreement with the measured data.2. The predictions based on handbook correlations have shown good agreement with the measured data in the orifice region. The empirical orifice correlation from the Idelchik handbook could be recommended for prediction of pressure loss in the orifice region.3. The predictions of pressure losses on the gate valve obtained by the Borda-Carnot correlation overestimated the measured data. On the other hand, the CFD simulation has shown good agreement with the measured data.4. In the expansion tank region, predictions by correlations and CFX® have shown good agreement with the measured data.5. In the heat exchanger region, large discrepancies were caused by different correlations for the entrance and discharge region. As a best practice guideline for entrance and discharge region, Idelchik handbook correlations which showed good agreement with measured data were introduced.6. Based on CFX® simulation in the gasket and tee-straight regions, the effect of gasket and tee-straight to pressure loss was low enough to neglect. In the gasket region, prediction by Idelchik recess correlation is recommended. On the other hand, it is recommended in the tee-straight region that tee-junction effect should be neglected.7. In the tee-branch region, VDI handbook correlation was in good agreement with CFX® result.8. In the 45o elbow, 90o elbow and the straight pipe region, all predictions including CFX® simulation are very similar.9. For the benchmarking regions based on the measured data, CFD simulations provided more reliable results than any other correlations. CFD simulations could be recommended to obtain a high accuracy prediction of the pressure loss in LACANES. In the tee-straight, tee-branch, and the gasket, which have large discrepancies between predictions without measured data, CFD stimations are regarded as good guidelines to predict pressure losses.
31 Dicembre 2012
Sviluppo del Sistema e della Rete Elettrica nazionale (RETE 2012)