Heat transfer in thin liquid films flowing over horizontal tubes

Results are presented for an experimental investigation of the evaporation heat transfer characteristics of thin water films flowing over 2.54 cm and 5.08 cm diameter smooth heated horizontal brass tubes. Data were obtained for subcooled and saturated conditions corresponding to feed water temperatures ranging from 49 to 127 C and heat flux values ranging from 15,760 to 78,000 W/sq m. Flow rates ranged from 2.78 to 5.85 cu cm/s per centimeter length of tube for the 2.54 cm tube and from 4.65 to 7.62 cu cm/s per centimeter length of tube for the 5.08 cm tube. A laminar analysis involving both an integral approach with a cubic polynomial velocity profile and a finite difference scheme with a stagnation point boundary layer profile were used to determine the film thickness and evaporation heat transfer coefficients. Results of these analyses were found to be in excellent agreement with the report data.