Heat transfer from a dimple-imprint downstream of boundary-layer trip-wire

Abstract

Abstract Dimples are widely known to increase heat transfer coefficients in internal passages with a minimal pressure drop. The naphthalene sublimation method was used to measure local heat transfer coefficient variations of single dimple imprint channel with the analogy between heat and mass transfers. The effect of a boundary layer trip-wire with different diameters was compared under different flow conditions (1000 S h / S h 0 ). However, under the laminar flow (Re ~ 1000), the flow was re-laminarized, resulting in a negligible effect of the trip-wire. Without a trip-wire, the heat and mass transfer increase was limited to the downstream of dimple cavity. With installation of a trip-wire, even the upstream of dimple cavity exhibited increased heat and mass transfer variations with enhanced turbulent intensity. As the diameter of a trip-wire increased, the area-averaged Sherwood number ratio ( S h ¯ ¯ / S h 0 ) under the transitional and turbulent flow conditions (3000