Forced flow boiling heat transfer of liquid hydrogen for superconductor cooling

超伝導冷却のための液体水素の沸騰強制熱伝達

白井 康之*; 達本 衡輝; 塩津 正博*; 畑 幸一*; 小林 弘明*; 成尾 芳博*; 稲谷 芳文*; 木下 勝弘*

Shirai, Yasuyuki*; Tatsumoto, Hideki; Shiotsu, Masahiro*; Hata, Koichi*; Kobayashi, Hiroaki*; Naruo, Yoshihiro*; Inatani, Yoshifumi*; Kinoshita, Katsuhiro*

液体水素が内径6mmの電流加熱垂直円管内を上向きに上昇する場合の円管内面における強制対流熱伝達を流速,液温を変えて測定した。各流速における沸騰開始にいたる非沸騰熱伝達はDittus-Boelter式とよく一致、この実験システムで採用した高精度ディジタルはかりによる質量流量測定法の有効性が確かめられた。さらに、これまで全くと言ってよいほど実験データのなかった強制対流沸騰臨界熱流束の流速,サブクール度依存性を初めて明らかにした。

Heat transfer from inner side of a heated vertical pipe to liquid hydrogen flowing upward was first measured at the pressure of 0.7 MPa for wide ranges of flow rates and liquid temperatures. The heat transfer coefficients in non-boiling regime for each flow velocity were well in agreement with the Dittus-Boelter equation. The heat fluxes at the inception of boiling and the DNB heat fluxes are higher for higher flow velocity and subcooling. It was found that the trend of dependence of the DNB heat flux on flow velocity was expressed by the correlation derived by Hata et al. based on their data for subcooled flow boiling of water, although it has different propensity to subcooling.