The numerical calculation of heat transfer performance for annular flow of liquid nitrogen in a vertical annular channel

According to a separated phase flow model for vertical annular two-phase flow in an annular channel, the liquid film thickness, distributions of velocities and temperatures in the liquid layer are predicted in the range of heat fluxes: 6000-12000 W/m(2), mass flux: 500-1100 kg/m(2) s. The pressure drop along the flow channel and heat transfer coefficient are also calculated. The liquid film thickness is in the order of micrometers and heat transfer coefficient is 2800-7800 W/m(2) K of liquid nitrogen boiling in narrow annular channels. The measured heat transfer coefficient is 29% higher than the calculated values. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop and heat transfer coefficient increase. (C) 2001 Elsevier Science Ltd. All rights reserved.