Pin bundle heat transfer

Lead cooled fast reactor design assumes the subassembly with fuel pins arranged in square lattice with large pitch-to-diameter ratio (s/d 1.4-1.5). In LMFR a more tight arrangement of fuel pins is adopted (s/d 1.1-1.18)  

Both experimental and analytical studies of heat transfer in Hg, PbBi, NaK and Na coolants have been carried out. The following relationships for evaluation of heat transfer in triangular lattice bundle were obtained experimentally  

Zhukov (rod bundles with spacers, square arrays) [6.22]  

It has been demonstrated that Nusselt number for square lattice is lower than that for triangular lattice bundles [6.17, 6.18]. This is illustrated by the data in Fig. 6.2. 

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