Experimental study of single-phase natural circulation heat transfer in a narrow, vertical, rectangular channel under rolling motion conditions

Experimental studies of single-phase, natural circulation heat transfer characteristics in a narrow, vertical, rectangular channel under static and rolling motion conditions were performed and the effects of rolling motion on the heat transfer characteristics were obtained. The experimental results show that the natural circulation flow rate varies periodically in rolling motion conditions. Furthermore, rolling motion leads to the reduction of the cycle-averaged flow rate. In rolling motion conditions, the cycle averaged heat transfer characteristics are enhanced in the transition regime. However, in laminar and turbulent regimes, the cycle-averaged heat transfer characteristics do not show a significant difference compared to that under static conditions. The effect of velocity oscillation on the heat transfer pulsation amplitude in a narrow rectangular channel is suppressed compared to that in conventional channels because of the restriction of flow by the channel wall. Furthermore, by analyzing the effect of the heat capacity of the heating plate theoretically in rolling motion, the inner-wall temperature and heat flux are obtained. The cycle-averaged Nusselt number in rolling motion can be predicted by using the correlation in the static state, and based on the experimental data, the amplitude of the Nusselt number in rolling motion is obtained by using the thermal-hydraulic parameters in the static state. Thus, the instantaneous Nusselt number in rolling motion conditions predicted by the thermal-hydraulic parameters in the static state is developed. (C) 2016 Elsevier Ltd. All rights reserved.