ABSTRACTThe manufacturing tolerances of rib turbulators lead to variations in the cooling of internal ribbed passages because the manufacturing tolerances cause the actual geometry to differ some from the design which affects the flow structure as well as the coolant mass flow rate. Such variations may significantly affect the system cooling performance, and may lead to the failure of hot components. Thus, it is necessary to determine the effects of manufacturing tolerances on the cooling performance for such variations in rib turbulators in internal passages. This study numerically investigates the cooling of internal rib turbulated passages using the relationship between the geometric parameters and the coolant mass flow rate using the three-dimensional Reynolds-averaged Navier–Stokes equations for various rib heights, rib widths, wall thicknesses, and coolant mass flow rates. Correlations are developed to predict the cooling performance in response to geometric variations of the internal passages due to manufacturing tolerances. The variations in the design parameters of the internal rib turbulated cooling system has differing effects on the cooling performance, even within the same range of manufacturing tolerances.