Estudo teórico e experimental da perda de pressão em curvas de retorno com escoamento bifásico da mistura zeotrópica R-407C

Abstract

Evaporators and condensers of modern cooling systems are becoming increasingly compact. Therefore, the tubes of these heat exchangers present a large amount of return bends. Thus, the effect of singularities on the hydrodynamic performance becomes more important. In this work, a test bench was developed to study the pressure drop in return bends with tube diameter (D) of 4,77 mm and the curvature ratio (2R/D) from 4,40 to 10,83. The experimental data set was obtained varying the refrigerant mass flux within the range from 100 kg/m²s to 600 kg/m²s, for a pressure of 12 bar. This work aims to collect results by experimental tests with R-407C flowing in return bends and compare the experimental values with corresponding theoretical values obtained through correlations available in the literature. Based on the data obtained from the tests, it was possible to evaluate the pressure drop for different flow configurations. It was observed that the Padilla correlation showed the best accuracy, and that flow parameters (vapor quality and mass velocity) and geometry (curvature radius) lead to important influence on pressure drop results.