細線巻きつけによる水平管外凝縮の伝熱促進 : 蒸気流速の影響に関する理論的検討

抄録

Numerical solutions are presented for combined shear and gravity-controlled condensation on a horizontal tube, around which a fine wire is coiled, by using a simplified physical model. The local Nusselt number distribution represents that the effect of surface tension upon heat transfer decreases with the increase of vapour velocity. The avarage Nusselt number can be expressed by a rule of forth-power combination of the equations for shear-condensation and gravity-controlled condensation. The heat transfer enhancement ratio against a smooth tube decreases with the increase of vapor velocity, because the decrease of effective heat transfer surface becomes more significant than the heat transfer enhancement due to surface tension. The Nu-equation for gravity-controlled condensation can be applicable in the velocity range where the heat transfer enhancement is achieved.