Building a unique test section for local critical heat flux studies in light water reactor like accident conditions

Abstract

Critical heat flux (CHF) has been studied for almost a century and yet there is no indisputable consensus reached on governing physical phenomena behind, not to mention, on modelling agreement of different correlations. When we are compelled to run our system at the safe distance from the CHF, and we can use all the accumulated knowledge so far, we will quite possibly cling to look-up tables delivered with that particular system. If this is not the case, than we will certainly stick to the system-specific correlation, which cannot be applied with confidence elsewhere. In the last two decades there were significant advancements applied both in numerical simulation capabilities and in unintrusive measuring techniques, which shed light on anticipated advancements in modelling the phenomenon. However, there are few reliable experimental measurements of instantaneous velocity and temperature fields in the wall boundary layer, and they are nil where local heat transfer coefficients are acquired. Therefore, at Reactor Engineering Division of Jožef Stefan Institute, a unique test section for local critical heat flux studies is under construction. The selected geometry and the test conditions will resemble light water reactor – like accident conditions. Moreover, to understand the phenomenon better, the design of the test section enables local measurements of heat transfer coefficients, and allows for control over the diabatic wall temperature. Measurements of single-phase convective heat transfer, conjugate heat transfer, flow boiling, convective condensation, and condensation-induced liquid hammer were all part of the test section’s design basis. In this context, the design and construction of the device is herein presented in considerable detail.