Film boiling heat transfer from a vertical cylinder in forced flow of liquids under saturated and subcooled conditions at pressures

Forced convection him boiling heat transfer on a vertical 3-mm diameter and 180-mm length platinum test cylinder located in the center of the 40-mm in ner diameter test channel was measured. Saturated water, and saturated and subcooled R113 were used as the test liquids that flowed upward along the c ylinder in the test channel. Flow velocities ranged from 0 to 3 m s(-1), pr essures from 102 to 490 kPa, and liquid subcoolings for R113 from 0 to 60 K . The heat transfer coefficients for a certain pressure and liquid subcooli ng are almost independent of flow velocity and of a vertical position on th e cylinder for the flow velocities lower than approximate to 1 m s(-1) (the first range), and they become higher for the velocities higher than approx imate to 1 m s(-1) (the second range). Slight dependence on a vertical posi tion being nearly proportional to z(-1/4), where z is the height from the l eading edge of the test cylinder, exists for the flow velocities in the sec ond range. The heat transfer coefficients at each velocity in the first and second ranges are higher for higher pressure and liquid subcooling. Correl ation for the forced convection film boiling heat transfer with radiation c ontribution on a vertical cylinder was derived by modifying an approximate analytical solution for a two-phase laminar boundary layer model to agree b etter with the experimental data. It was confirmed that the experimental da ta of film boiling heat transfer coefficients in water and R113 were descri bed by the correlation within +/- 20% difference. (C) 2000 Elsevier Science S.A. All rights reserved.