Transitional natural convection flow and heat transfer in an open channel

► We study experimentally transitional natural convection flow in a vertical channel. ► We focus on the kinematic characteristics of the flow and wall heat transfer rates. ► Performed under UHF conditions, the assumption of an intermittent flow is favored. ► The flow exhibits a high sensitivity to the ambient conditions. ► The identified flow mechanisms suggest a possible control of the wall heat transfer.