Heat transfer to thin water films on horizontal tubes

Evaporation heat transfer characteristics are determined for thin water films flowing over one inch and two inch diameter smooth brass heated horizontal tubes. Experimental and theoretical studies include the effects of feedwater temperature, flow rate, concurrent steam shear and heat flux on the subcooled and boiling heat transfer coefficients. Experimental results for the subcooled evaporation heat transfer coefficients indicate decreasing values with increasing tube diameter and increasing values with increases in flowrate and feedwater temperature. The results obtained for boiling water films are characterized by large variations in the tube wall temperatures. Surface condition and aging were observed to have a marked effect on the boiling conductance. The stabilized coefficients were found to be ten to forty percent greater than the corresponding subcooled coefficients.