Experimental study of heat transfer at the transition regime between the natural convection and nucleate boiling: Influence of the heated wall tilt angle on the onset of nucleate boiling (ONB) and natural convection (ONC)

•A boiling-meter is designed and implemented in a new experimental set up.•This new device allows an original investigation of the heat transfer in natural and pool boiling regimes.•Time evolution of temperature and heat transfer characteristics of the boiling wall are provided for the first time.•Averaged heat transfer curves are carried out versus the orientation of the wall to the gravity.•The onset of nucleate boiling as well as the onset of natural convection is found to vary with the tilt angle of the wall.•An interpretation of the Onset of Nucleate Boiling (ONB) is provided based of the obtained original results.