The influence of the surface structuring type on heat transfer in falling films of the refrigerant mixture

摘要

The paper considers the influence of enhanced surfaces on heat transfer during evaporation and boiling of a falling laminar-wave liquid film. A mixture of R114/R21 refrigerants was used as a test fluid. The liquid film flowed on the outer surface of verticallyoriented cylinders. To intensify the evaporation process, the authors used the mesh coatings with variable mesh sizes, whereas the surfaces with variable characteristics of microstructure obtained by deformational cutting were used to enhance boiling. The report makes a conclusion about the studied types of structured surfaces, most effective for enhancement of heat transfer in different regimes. It is shown that the mesh coatings intensify heat transfer at evaporation twice as compared to a smooth surface; the microstructured coatings with partlyclosed micropores obtained by deformational cutting allow fourfold heat transfer intensification at boiling.