Forced convection heat transfer of subcooled liquid nitrogen in horizontal tube

Tatsumoto, Hideki; Shirai, Yasuyuki*; Hata, Koichi*; Kato, Takashi; Shiotsu, Masahiro*

The knowledge of forced convection heat transfer of liquid hydrogen is important for the cooling design of a material of a cold neutron moderator. An experimental apparatus that obtain forced flow without a pump was developed. As a first step of the study, the forced flow heat transfer of subcooled liquid nitrogen in a horizontal tube, instead of liquid hydrogen, was measured for the pressures (0.3 to 2.5 MPa). The inlet temperature was varied from 78 K to around its saturation temperature. The flow velocity was varied from 0.1 to 7 m/s. The heat transfer coefficients in non boiling region and the DNB heat fluxes were higher for higher flow velocity and higher subcooling. The measured values of Nu/Pr in non-boiling region were proportional to Re to the power of 0.8. With decrease in Re, they approached a constant value corresponding to that in a pool of liquid nitrogen. The correlation of DNB derived here can describe the experimental data within 15% difference was derived.