NUMERICAL SIMULATION OF TURBULENT HEAT TRANSFER IN AN ANNULAR FUEL CHANNEL AUGMENTED BY SPACER RIBS

摘要

Thermal-hydraulic characteristics of fuel channels with three-dimensional trapezoidal spacer ribs for high temperature gas-cooled reactors were investigated under the same coolant conditions as the reactor operation, maximum fuel channel outlet temperature of 1000°C and pressure of 4 MPa, and analytically by numericalsimulations using the k-ε turbulence model. The turbulent heat transfer coefficients in the spacer ribbed fuel channel were 20 to 100% higher than those in a concentric smooth annulus for a region of Reynolds number exceeding 2000. Furthermore, the predicted Nusselt number in the spacer ribbed fuel channel was in good agreement with the empirical correlation obtained from the present experimental data within an error of 10% with Reynolds number of more than 5000. On the other hand, the friction factors in the spacer ribbed fuel channel were higher than those in the smooth duct in the turbulent region , and also they could be predicted with sufficient accuracy. In addition, the present numerical simulation could clarify quantitatively the effects of the heat transfer augmentation due to the spacer ribs and the axial velocity increase due to a reduction in the annular channel cross-section.