Nusselt number and bulk temperature in turbulent Rayleigh--B\'enard convection

We present an algorithm to calculate the Nusselt number ($Nu$) in measurements of the heat transport in turbulent Rayleigh--B\'enard convection under general non-Oberbeck--Boussinesq (NOB) conditions (Shishkina, Weiss, Bodenschatz, Phys. Rev. Fluids, 2016). We further critically analyze the different ways to evaluate the dependences of $Nu$ over the Rayleigh number ($Ra$) and show the sensitivity of these dependences to the reference temperatures in the bulk, top and bottom boundary layers (BLs). Finally we propose a method to predict the bulk temperature and a way to calculate the reference temperatures of the top and bottom BLs and validate them against the G\"ottingen measurements (Ahlers, He, Funfschilling, Bodenschatz, New J. Phys., 2012).