Tese
Estudo experimental da perda de pressão em canais convencionais com o refrigerante R1234yf em ebulição convectiva
Fecha
2018-05-25Autor
Juan Jose Garcia Pabon
Institución
Resumen
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.