Ricerc@Sapienza

The proposed research activity is to enlarge the knowledge of the pool boiling heat transfer mechanism in relevant condition for the Isolation Condenser (IC), at atmospheric conditions, high heat flux and industrial grade of the surface roughness.
In the nuclear framework, the characterization of the power exchanged during all the working phases of this component is fundamental to guarantee enough safety margins avoiding unplanned changes in the temperatures. In particular, the evaluation of the heat transfer, obviously, is mainly correlated to the right prediction of all the heat transfer coefficient (HTC) into the pool during the boiling and inside the tubes (condensation). This experimental research is focused on filling the existing gap knowledge evidenced in the pool boiling for all the possible IC conditions, actually not available in any public research. Available data are focused on other pool boiling conditions or on an overall HT evaluation, but with low accuracy due to the difficulties in the measure of the power exchanged in two-phase. Then, this separate effect test will enhance our version of the thermal-hydraulic transient simulation code RELAP5 (reference code for these phenomena) on the prediction of the IC component.
This will be realized through the realization of a small experiment in our laboratory. After that, it is expected to analyze the experimental results and to obtain a new HTC correlation suitable for the assessment of safety and reliability of passive systems, inserting this in a modified version of the transient simulation code RELAP5.
The experiment will investigate pool boiling on the outer surface of cylindrical heater submerged in a water pool at atmospheric conditions. This activity is important as preparatory work for our possible contribution in a future Horizon Europe project on the increase of the TRL of the IC.