Abstract
Two theoretical models are developed to predict evaporation heat transfer in horizontal microfin tubes in the annular flow regime. The first model is based on the Carnavos equation for liquid flow and the equivalent Reynolds number is introduced to extend it to the annular flow regime. The second model considers the structure of liquid film and the heat transfer coefficient is determined as a sum of the contributions of the substrate film region and the disturbance wave region. Generally, the first model gives a good agreement with available experimental data for four tubes and three refrigerants at a high mass flux. The second model shows a smaller dependence on the quality than the experimental data, which is due to the lack of information on the structure of disturbance wave. On the basis of the first model and a previously proposed stratified flow model, a generalized prediction method applicable to a wide range of mass flux is also proposed.
