Effects of tube shape on flow and heat transfer characteristics in falling film evaporation

Highlights: • Two-dimensional numerical model with different tube shapes is established. • Error between simulation and experiment on heat transfer coefficient is within 9.5%. • Distribution of film thickness and velocity along four tubes are revealed. • Heat transfer characteristics of four tubes are compared. -- Abstract: Horizontal tube falling film evaporators are widely used in refrigeration and chemical industry. Two-dimensional numerical model with different tube shapes is established in this paper to simulate heat and mass transfer process with CFD method, and the heat transfer coefficient of simulation is also validated by experimental data. Flow and heat transfer characteristics of falling film evaporation on a circular tube and three flat tubes are investigated, respectively. It is confirmed that the liquid film becomes thinner and thinner as height-width ratio increases and average film thickness of three flat tubes is nearly 2.9–16.5% smaller than that of circular tube 1. Additionally, the cross sections of flat tube have a lower dimensionless temperature and a thinner thermal boundary layer, which means a better heat transfer performance compared with the circular tube 1. The average heat transfer coefficient of three flat tubes is approximately 2.2%, 4.2% and 11.2% higher than that of the circular tube, respectively.