Experimental study on single-phase heat transfer of natural circulation in circular pipe under rolling motion condition

•The effect of rolling motion on natural circulation flow pulsation is studied.•The effect of flow pulsation on natural circulation cycle-averaged heat transfer is studied.•The relationship between the cycle-averaged flow rate before and after rolling motion is studied.•The instantaneous heat transfer coefficient of natural circulation pulsating flow is obtained.

Experimental investigation of the single-phase natural circulation heat transfer characteristic in static and rolling motion conditions are conducted. The results show that rolling motion leads to the reduction of cycle-averaged flow rate compares to that in the static state with the same thermal–hydraulic parameters. And the flow rate changes cyclically with the same period of the rolling motion. In addition, the results also indicate that the flow pulsation enhances the cycle-averaged heat transfer characteristic. Furthermore, the relative pulsation amplitude of the Nusselt number increased linearly with the relative pulsation amplitude of Reynolds number. Based on the relationship between the cycle-averaged flow rate before and after rolling motion start, and the relationship between rolling motion parameters, the relative pulsation amplitude of Nusselt number and cycle-averaged Reynolds number, the instantaneous Nusselt number under rolling motion condition can be predicted using the thermal–hydraulic parameter in static condition.