Experimental study on flow split and pressure drop characteristics in a 3 x 3 dual-cooled annular rod bundle

In this paper, flow split and pressure loss experiments were performed in a 3 x 3 dual-cooled annular rod bundle. A novel experimental methodology was developed to obtain the flow split between the internal and external channels. The flow split ratio was close to the flow area ratio of the internal channel to the external channel but didn't change significantly with the increase of flow rate and inlet temperature. An approximate mathematical expression was proposed to analyze the flow split mechanism. The overall and local pressure drops were also measured. The friction factor in bare rod bundle and pressure loss coefficient at the spacer grid were examined. An assessment of existing correlations for predicting the friction factor and the pressure loss coefficient at the spacer grid was carried out against the experimental data. Correlations for predicting friction factor and spacer loss coefficient were developed, which agreed well with the experimental results.