水平2重円管を流れる液体窒素の沸騰熱伝達

抄録

Forced convection boiling of liquid nitrogen flowing in a horizontal annulus has been studied. The heat transfer test section consists of an electrically heated core tube 0.85cm O.D.×50cm long and an insulated outer tube. Three sizes of outer tube having inner diameter of 1.24, 1.45 and 2.23cm were used to investigate the effect of diameter ratio on heat transfer coefficient. The temperature of the heated tube were measured by eight copper-constantan thermo-couples immersed along the heated length. The experiment was carried out at an atmospheric pressure and in low quality range and the mass flow rate was varied from 45.8 to 208 grams per second. The flow pattern in a horizontal annulus is more complicated than in a horizontal tube, therefore visual studies were made of the flow pattern of the fluid boiling in horizontal annulus.
Experimental data were well correlated by Lockhart-Martinelli parameter, Reynolds number and diameter ratio in convective region. The maximum heat flux in the horizontal annulus was well correlated with mass flow rate for the present study.