Estudo experimental da perda de pressão em canais convencionais com o refrigerante R1234yf em ebulição convectiva

Abstract

New legislation in Europe, limit the use of refrigerants with high global warming potential (GWP). Currently the most widely used refrigerant medium temperature equipment is the R134a with GWP of 1430, which therefore must be replaced. The main substitute is the fluid R1234yf, which is already being used in the automotive industry. The R1234yf has a GWP lower to 1. This work presents the theoretical and experimental study of the pressure drop of the refrigerant R1234yf on boiling in a horizontal smooth tube. Tests were carried out to pressure drop into two-phase flow in convective boiling of refrigerant R1234yf for vapor quality (0% to 100%), velocity mass (200 kg/m²s, 300 kg/m²s and 400 kg/m²s), heat flux (0 kW/m², 7 kW/m², 14 kW/m²) and two evaporation temperatures (20°C and 30°C). The test sections were used with four internal diameters: 3.2 mm, 4.8 mm, 6.4 mm 8.0 mm. The experimental results were compared with 19 correlations of literature. The correlation suggested by Xu and Fang in the year 2012, was the best with a mean absolute error of 20%. A new correlation based on the parameter Martinelli was proposed based on the results obtained for the R1234yf fluid under the conditions studied. The correlation presented a mean absolute error of 17%. In addition, a multilayer neural networks model has been developed. The model showed a mean absolute error of 6%. Finally, it was shown that the pressure drop in convective boiling of R1234yf is 20% lower when compared with R134a in the experimental conditions tested.