A reasonable heat transfer coefficient correlation for a finned-tube air cooler was established by applying the methods of dimensional analysis and function analysis. This approach focused on an air cooler design in which the refrigerant phase changes in the tube. A pump-feeding ammonia air cooler was chosen as the experimental study object. Further

a multi-factor and multi-level experimental scheme was designed for this machine type. The scheme included the structure parameters

face velocity

ambient temperature

driving temperature

and circulation ratio. The heat transfer coefficients were tested under various conditions using a calibrated-box method according to the scheme. Moreover

the heat coefficient correlation of the pump-feeding ammonia air cooler was obtained through a nonlinear fitting method based on the test results. It was found that the relative errors between the calculated correlation values and the test values range from ?10% to +10%. Furthermore

the tube side heat coefficient is larger than the outside heat coefficient

which is consistent with practical experiments. These results show that the established correlation is reasonable and sufficiently accurate for use in practice. The calculated correlation values are 1.11 to 1.30 times the experimental values at the common design points for the pump-feeding ammonia air cooler. Thus

the heat transfer surface can be reduced by 11%-30% when the correlation is applied in the design of this type of air cooler. This correlation is helpful for reduction of the machine dimensions and to enhance its economic efficiency.