Yang Yan-hua

Study on the heat transfer of cross flow in vertical upward tubes

A special device was designed to measure temperature difference in this study of heat transfer of water and oil cross flow inside vertical upward tubes. A new heat transfer correlation was obtained for cross flow. The experimental results showed that the dependence of heat transfer on Reynolds is much smaller in a narrow space than that in a wide space. It was found that the heat transfer correlation of cross flow in a narrow space is obviously different from that in a wide space, and that the heat transfer correlation obtained in a wide space may not be applicable to the cross-flow heat transfer in a narrow space. Further, the single-phase heat transfer capability of water cross flow was compared with that of oil cross flow. The experimental results showed that the average heat transfer coefficient of water is about 2–3 times that of oil when they have the same superficial velocity.

Experimental investigation on the bursting of single molten droplet in coolant

Abstract An experiment facility for observing low-temperature molten tin alloy droplet into water was established to investigate mechanisms of vapor explosion occurring in severe accidents of a fission nuclear reactor. The vapor explosion behaviors of the molten material were observed by a high-speed video camera and the vapor explosion pressures were recorded by a pressure transducer mounted under the water surface. The results showed that the pressure reached a peak value when the molten metal temperature was 600°C–650°C, and the coolant temperature had an obvious decreasing effect on the droplet breakups. A model for single droplet fuel/coolant interaction is proposed. It considers that in the case of Rayleigh-Taylor instability, the coolant that jets from opposite direction penetrates into the fuel and the vapor explosion occurs because of the rapid evaporation. This model explained the effect of metal droplet temperature and coolant temperature on vapor explosion.