Experimental Study on the Effect of Localized Blockages on the Friction Factor of a 61-Pin Wire-Wrapped Bundle

Abstract

The thermal-hydraulic behavior of the flow in rod bundles has motivated numerous experimental and computational investigations. Previous studies have identified potential for accumulation of debris within the small subchannels of typical wire-wrapped assemblies with subsequent total or partial blockage of subchannel coolant flow. A test campaign was conducted to study the effects of localized blockages on the bundle averaged friction factor of a tightly-packed wire-wrapped rod bundle. Blockages were installed within the bundle, and fluid pressure drop was measured across one wire pitch for a Reynolds number range of 500-17,200. The Darcy-Weisbach friction factor of the perturbed rod bundle geometry was compared with that of the unblocked bundle, as well as with the predictions of a well-established friction factor correlation. Differing effects based on blockage size and location for various flow regimes were studied. A number of conclusions can be made about the effects of the blockages on the friction factor, such as: an increasing effect of the blockage on friction factor with an increase in Reynolds number, a change in flow behavior in the turbulent transition flow regime near Reynolds number 3,000, differences in effect on friction factor for different types of subchannel blockage, and a nonlinear trend in friction factor variation with flow area impeded for edge subchannels. To this end, all data and quantified uncertainty produced in the present study are made available comparison and validation of advanced computational tools.

CFD Benchmark of Pressure Drop in a 61-Pin Wire-Wrapped Assembly with Blocked Channels Using NekRS

“…The full-edge blockages that are installed on the outside of the fuel bundle were chosen. Blockages 1 and 2 are designed to cover four edges and two half-corner subchannels, which corresponds to a symmetric sixth of the peripheral flow area in the test section [4]. The blocked flow area A b of this blockage type is 6.4% of the total unblocked one.…”

“…Extensive experimental work has been performed investigating wire-wrapped fuel assemblies. This includes significant work at Texas A&M University (TAMU) on adiabatic assemblies with unblocked channels [2], blockages on two interior subchannels [3], and larger blockages both on interior and exterior subchannels [4]. The studies at TAMU used a surrogate fluid due to the difficult nature of working with liquid metals.…”

“…To further that goal, a subset of the available pressure drop measurements [4] was chosen for the initial benchmark efforts. The experimental facility consisted of 61 pins of 15.88 mm diameter helically wrapped with a 3 mm diameter wire.…”

“…Pressure measurements were taken at one helical pitch, apart from the blockages centered between the measurement locations. Further details on the experimental setup can be found in [4]. Of the available blockage configurations, the full edge blockages, which are installed on the outside of the bundle, were chosen.…”

Applicability of RANS models and pressure drop in edge subchannels for 19-pin wire-wrapped fuel bundle channel in CiADS

“…The SST k-ω cubic model fitted well for both transition and fully turbulent flow regimes. Bovati et al [ 26 ] applied three turbulent models for the accident of local blockage in a 61-pin wire-wrapped hexagonal duct model, and compared their results with experimental data in the previous work [ 27 ]. Their comparison results recommended employing Reynolds Stress Model (RSM) and Realizable k-ε to the turbulent regime, and SST k-ω to the transition regime.…”