A regressive model for dynamic impulsive instabilities during the condensation of R134a, R1234ze(E) and R1234yf refrigerants

摘要

This article presents a proposal for a regressive model describing dynamic pressure v_p and temperature v_T impulsive instabilities during condensation of R134a refrigerant and isomers R1234yf and R1234ze(E) in minichannels. The model was verified in relation to the obtained experimental results. In the development of the model, a dimensionless analysis using Buckingham's PI theorem was applied to obtain the dependence on dimensionless values of the propagation velocities of the pressure instability v_P~+ related to the acoustic speed v_P and of the temperature instability v_T~+ related to the condensation front v_(FC). Experimental studies were carried out with the use of miniature tubes of circular cross-section with hydraulic internal diameter dh = 3.30, 2.30, 1.92, 1.44, and 1.40. The comparison of the computational results obtained from the model with experimental results showed a satisfactory compliance of ±25%.