Single- and two-phase heat transfer enhancement in a curved, rectangular channel subjected to concave heating

An experimental program was undertaken to examine single- and two-phase heat transfer enhancement provided by streamwise curvature. Curved and straight rectangular flow channels were fabricated with 5.0 x 2.5-mm cross-sections and heated lengths of 101.6 mm in which the heat was applied to only one wall--the concave wall (32.3 mm radius) in the curved channel and a side wall in the straight. Reynolds number ranged from 9,000 to 130,000 and fluid subcooling from 3 to 29;Single-phase convection coefficients were enhanced in the curved channel for all conditions tested. Critical heat flux was augmented due to flow curvature at all conditions with the enhancement decreasing as subcooling increased.;Flow visualization tests conducted in transparent channels identified important vapor characteristics and provided insight into two-phase enhancement. A model based on the interfacial lift-off criterion was developed to predict critical heat flux from straight and curved surfaces. The model provided excellent predictions for near-saturated conditions but was less accurate for subcooled flow.