Heat transfer in a reciprocating curved square duct fitted with longitudinal ribs

A set of experimental heat transfer data generated from a reciprocating square-sectioned curve duct fitted with longitudinal ribs along centerlines of duct walls is analyzed. Augmented Nusselt numbers in the static rib-roughened curve duct fall in the range of 1.2-1.45 times of smooth-walled curve-tube values as the longitudinal ribs trip the curvature induced vortices. Coupling effects of inertial, centrifugal and reciprocating forces in the rib-roughened reciprocating curved duct interact with buoyancy to exhibit synergistic influences on heat transfer. Local Nusselt numbers in the reciprocating test duct are in the range of 0.7-1.3 times of the non-reciprocation levels. Without buoyancy interaction, reciprocating Nusselt numbers decrease with the increase of the relative strength of reciprocating force within the present parametric conditions tested. Reciprocating buoyancy impacts enhance heat transfer and are inter-correlated with the pulsating force-effects. A set of empirical heat transfer correlation is derived to evaluate the individual and interactive effects of inertial, centrifugal and reciprocating forces, with and without buoyancy interaction, on overall heat transfer performance for piston cooling applications.