Abstract: The film thickness distribution and average thickness outside a horizontal test tube were measured by using a film-thickness meter. The effects of liquid load, evaporation boiling point, evaporation temperature difference and tube diameter on film thickness, waving intensity and, as a result, the heat-transfer film coefficients outside the horizontal-tube were studied experimentally. Experiments of the heat-transfer coefficient of horizontal-tube evaporation were conducted with various operation parameters. Wave function G(δ⁺) for describing the wave characteristics of the film on the surface of horizontal-tube and dimensionless evaporation heat-transfer film coefficient h(α⁾⁺₂ were specifically defined. Equations of evaporation heat-transfer coefficient were set up by regression of experimental data. Some literature models of evaporation heat-transfer coefficients do not give satisfactory results, because film waving is not considered in the models. This shortcoming is overcome in the present models. These results provide a basis for further developing high efficiency heat-transfer process and novel evaporators.