Experimental investigation on the heat transfer characteristics of molten salt to subcooled boiling water

•this paper studies the heat transfer characteristics of solar salt to subcooled boiling water.•the heat transfer performance of solar salt is affected by pressure, flow flux, molten salt inlet temperature.•the ONB is affected by water mass flow rate, pressure and molten salt inlet temperature.•the fitting correlation is first obtained to describe the heat transfer performance of solar salt. In this study, an experiment was conducted to obtain the heat flux and heat transfer coefficient of a mixed molten salt (60% NaNO3, 40% KNO3) and water at subcritical pressure in a tube in tube heat exchanger. The control variable method was used in this study. Experimental parameters covered the molten salt and water flow fluxes of 283.1–305.9 kg/m2s, 38.7–64.4 kg/m2s, the water pressures of 15–19 MPa, the water and molten salt inlet temperature of 260 °C/ 360–560 °C, and heat fluxes of 43–266 kW/m2, respectively. The heat transfer performance of molten salt and water in the single-phase and subcooled boiling regions were analysed with respect to molten salt flow fluxes and inlet temperature, water flow fluxes and pressure. Based on the experimental data, the heat transfer characteristics of molten salt to subcooled water was compared to the classical Grimson correlation, with a maximum deviation of −20%. Finally, the fitting correlation of the thermal performance of molten salt to the subcooled boiling water was presented, the fitting values demonstrated good consistency with the experimental data, with a maximum deviation of –10%.