Conference Proceedings Paper
COMPARISON BETWEEN THE HEAT TRANSFER CHARACTERISTICS OF SUPERCRITICAL PRESSURE WATER IN HORIZONTAL TUBES AND INCLINED TUBES
The 5th International Symposium on SuperCritical Water-cooled Reactors - 2011 March 13-16
Shuiqing Yu (Xi'an Jiaotong University)
Huixiong Li (Xi'an Jiaotong University)
Xianliang Lei (Xi'an Jiaotong University)
Yifan Zhang (Xi'an Jiaotong University)
Tingkuan Chen (Xi'an Jiaotong University)
This paper is devoted to elucidate the effect of flowing orientation on the flow and heat transfer characteristics of supercritical pressure water in the large specific heat region (LSHR) where significant thermo-physical property variations occur and may cause heat transfer enhancement or deterioration. In order to get insight into the mechanism governing heat transfer enhancement or heat transfer deterioration, experimental results of flow and heat transfer of supercritical pressure water in inclined upward smooth tube of Φ25×2.5mm and Φ32×3mm with an angle of a＝20° are compared to that in horizontal smooth tubes with a diameter of Φ32×3mm over a wide range of parameters such as pressures ranging from 23 to 28MPa, average heat fluxes up to 600kW/m2, and mass fluxes in the range of 200 to 1000 kg/m2×s, and emphasis is placed on the effect of flowing orientation on the flow and heat transfer characteristics of supercritical pressure water, especially in the LSHR. It is found that there exists distinct difference in heat transfer processes between the horizontal tubes and the inclined tubes, strikingly illustrated by the difference in both the temperature distribution and heat transfer coefficients distribution on the top and bottom surface of the tubes. In the enthalpy region which far away from the LSHR, the temperature on the top wall of the horizontal tube and the inclined tube slightly exceeds the temperature on the bottom wall of the corresponding tubes; while in the LSHR , there exist huge differences in temperature on the top wall and the bottom wall of the horizontal tubes under moderate and high heat fluxes, and the temperature difference between the top wall and bottom wall of the inclined tubes is small in comparison to that of the horizontal tubes. Difference in heat transfer coefficients between the horizontal tube and the inclined tube exhibits a trend similar to that of the wall temperature of the corresponding tubes. The reasons that cause such differences are analyzed. Results obtained in this study may be useful for the design of boilers and nuclear reactors operated at supercritical pressures.
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