On the development of a grid-enhanced single-phase convective heat transfer correlation

A new single-phase convective heat transfer augmentation correlation has been developed using single phase steam cooling experimental data obtained from the Penn State/NRC Rod Bundle Heat Transfer (RBHT) facility. New findings of physical significance have been identified in evaluating the RBHT steam cooling data. The results clearly indicate that the grid-enhanced heat transfer depends not only on the grid blockage ratio but also on the flow Reynolds number. The latter is found to have a strong effect on the process of flow restructuring. Existing correlations currently employed in transient analysis codes, though accounted for the effect of grid blockage ratio, did not include the Reynolds number effect. The new correlation developed in the present study which adequately accounts for the effect of Reynolds number on the maximum heat transfer augmentation at the grid and the rate of decay of the grid-enhanced heat transfer in the downstream locations correctly captures the physics of flow restructuring as the flow passes through a spacer grid. The present work represents the first attempt to quantitatively account for the dependence of the grid-enhanced heat transfer on the flow Reynolds number that had not been considered in previous studies.