- Evaporation and boiling heat-transfer coefficients are presented for thin water films flowing over the outside of horizontal, electrically heated brass tubes. Tests were conducted with a 5.08-cm-dlameter smooth tube, a 5.08-cm-diameter circumferentially grooved tube, and a 5.08-cm-dlameter axially grooved tube. Both local and average heat-transfer data were obtained for nonboHIng and boiling conditions corresponding to feed-water temperatures ranging from 49 to 127 C and heat-flux values ranging from 30 000 to 80 000 W/m2. Flow rates ranged from 1.16 to 3.79 cm3/s per centimeter length of tube. Correlations of the average heat-transfer coefficients for nonbolllng and bofllng conditions were developed and compared. The results Indicate that both enhanced tubes provided higher heat-transfer coefficients than the smooth tube. 1985, American Chemical Society. All rights reserved.