An innovative method for prediction of liquid metal heat transfer rate for rod bundles based on annuli

An annulus can be seen as a rod bundle with a single rod, which has no thermal–hydraulic interaction with other rods. Thus the interaction in rod bundles can be obtained with the help of certain annuli. The heat transfer rates of both triangular and square lattices were studied based on the correlation of annuli, and modifications were done to take into account the influences of temperature difference, hydraulic diameter, interaction and shape difference, etc. The temperature difference correction was calculated with the section temperature distribution experimental data for annuli, while the other three were determined with geometric parameters. Correlations for both lattices were compared with available experimental data and the results showed good agreement. Comparison of these two correlations indicated that there were important differences between the two arrangement patterns if the pitch-to-diameter ratio was less than 1.25. Furthermore, the interaction correction was found to be generally equal to the thermal mixing length scale used in the sub-channel analysis, which may be used as a new correlation for the interaction correction.

► A new method to obtain heat transfer rate for rod bundles from annuli is developed.
► Two correlations are proposed for triangular and square arranged bundles respectively.
► There are important differences in heat transfer between triangular and square lattices for small pitch-to-diameter ratios.
► The interaction correction is found to be similar to the thermal mixing length scale used in sub-channel analysis.