曲円管内の沸騰熱伝達の実験研究 : サブクール沸騰熱伝達とバーンアウト熱流束

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The purpose of the present investigation is to study on the boiling heat transfer and burnout characteristics of water flow in horizontal curved pipes and horizontal straight pipes under subcooled or low quality conditions. This experimental works were done at Ship Reserch Institute, using electrically heated test sections in the low pressure loop with 275-kilowatt D.C. power supply and with a main circulation pump having an exit pressure of 6.0kg/cm^2G and maximum flow rate of 0.2m^3/min. Two groups of herical curved pipes and some straight pipes of 347 stainless steel, all with the same total length of 800mm and O.D. 13.0mm×I.D. 10.0mm, were used as the test sections of this study. The pitch diameters of the herical curved pipes were either 200mm or 400mm, the formers are bent in 360 deg. and latters are bent in 180 deg. The conditions of the experiment of subcooled boiling heat transfer of the curved pepes were as follows: Loop pressure nearly atmospheric. Inlet velocity of water was varied from 1.5 to 3.0m/sec. Local liquid subcool temterature was varied from 0 to 12 deg. Heat flux was varied from 2×10^5 to 10^6kcal/m^2hr. With above conditions the heat transfer coefficients in various points of the test section were measured by the thermocouples attached on the pipe walls. In the case of burnout experiments, these conditions were as follows: Loop pressure was varied frou 2.0 to 5.0kg/cm^2abs. Mass flow rate of water was varied from 1.0×10^6 to 7.3×10^6kg/m^2hr. Test section inlet liquid subcool temperature was varied from 29 to 63 deg. Exit steam quality was varied from 10 to 45% With above conditions burnout experiments were conducted. The results obtained from these experiments can be summerized as follws: (1) The heat transfer coefficient in subcooled boiling region increases, as the pitch diameter is decreased. These effects might be explained as a influence of the secondary flow induced in the curved pipe. (2) The heat transfer coefficient on the outer surface, h_0 is greater than that on the inner surface h_i. In the experiments of the curved pipe of 200mm pitch diameter of helix, the ratio h_0/h_i is between 1.5 and 2.0, while in the case of 400mm pitch diameter, h_0/h_i is between 1.2 and 1.5. (3) The effect of change in pitch diameter of helix to the value of burnout heat flux q_<B0> are not so remarkable as anticipated, but the position of the burnout initiation depends on whether in curved pipes or straight pipes. In the case of the curved pipes, the position of burnout initiation exists on the inner side of curve, while in the straight pipes, they exist on the upper side. The reason of this could be explained by the eccentric concentrarion of the steem void. (4) Experimental values of the burnout heat flux can be correlated fairly well with the pressure drop between inlet chamber and outler chamber.
独立行政法人海上技術安全研究所の論文
1970-07-15

曲円管内の沸騰熱伝達の実験研究 : サブクール沸騰熱伝達とバーンアウト熱流束

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