Convection heat transfer of alkali liquid metals and LBE in hexagonal bundles of uniformly heated tubes with helical spacers

Both correlations agree with the majority of the compiled experimental and numerical data to within ±15%. Nuww is consistently lower than Nub,ww, and the difference is independent of P/D, but increases from 38% at low Pe (<100) to as much as 52% at Pe = 1100. Nuww, is also higher than that reported earlier by the authors for bare heated tubes, Nus, with the difference increasing from 42% to 111% with increased Pe from 300 to 1100, and decreased P/D from 1.3 to 1.1.