.TRANSFORM.Fluid.ClosureRelations.PressureLoss.Functions.SpacerGrids.K_spacerGrid_Rehme

Information

Spacer-grid pressure-loss coefficient for a rod bundle by the Rehme (1973) modified drag-coefficient method:

K = Cv·ε²,  referenced to the undisturbed bundle velocity head (dp = K·m_flow²/(2ρA_bundle²))

where ε is the blockage ratio (spacer projected frontal area / bundle flow area, valid ~0.15–0.5) and Cv is the modified drag coefficient. Rehme gives Cv as a chart vs Reynolds number; here the semi-empirical fit of that chart (Cigarini & Dalle Donne 1988; Schikorr et al. 2010) is used:

Cv = 3.5 + 73.14/Re^0.264 + 2.79×10¹⁰/Re^2.79, capped at 2/ε

(e.g. Cv≈10 at Re=10⁴, ≈5.8 at Re=5×10⁵).

References

Rehme, K. Pressure Drop Correlations for Fuel Element Spacers, Nuclear Technology 17 (1973) 15–23.

Schikorr, M., Bubelis, E., Mansani, L. & Litfin, K. Proposal for pressure drop prediction for a fuel bundle with grid spacers using Rehme pressure drop correlations, Nucl. Eng. Des. 240 (2010) 1830–1842.

Interface

function K_spacerGrid_Rehme
  extends TRANSFORM.Icons.Function;
  input Units.NonDim epsilon "Blockage ratio = spacer frontal (projected) area / bundle flow area";
  input SI.ReynoldsNumber Re "Bundle Reynolds number";
  output Units.NonDim K "Resistance coefficient (ref. bundle velocity head)";
end K_spacerGrid_Rehme;