Heat transfer from a 2×2 wire-wrapped rod bundle to supercritical pressure water

An experiment has been completed to study the heat transfer characteristics of supercritical water in a 2×2 wire-wrapped rod bundle. The rod-bundle simulated a fuel assembly with four heated rods and was installed inside a square channel with rounded corners. A wire of 1.2mm outer diameter was helically wrapped around the outer surface of each heated rod at an axial pitch of 200mm. The experimental parameters covered the pressure of 23–28MPa, mass flux of 400–1000kg/m2s and heat flux range on the rod surface of 200–1000kW/m2. Wall temperatures obtained at each heated rod were examined and average heat transfer coefficients were calculated at each measuring location of the rod and compared against those obtained with a 2×2 bare rod bundle. Heat transfer characteristics of supercritical water in the 2×2 rod bundle were analyzed with respect to the variations of heat flux, mass flux and pressure. Eleven heat transfer correlations were assessed against the current set of test data. The results showed that the correlations of Jackson and Krasnoshchekov–Protopopov give the best predictions on average Nusselt number.