LAUSR

Abstract The following paper presents the results of experimental research on the condensation of R134a and R404A refrigerants in horizontal tubular mini-channels during impulsive hydrodynamic instabilities. Due to the complexity of the problem, it will be presented in two parts. The first part covers the results of experimental research on the influence of impulsive instabilities during the development of condensation of R134a and R404A refrigerants in mini-channels. The second part will cover the decay of condensation for similar conditions. The paper also provides a definition and conditions of the initiation and propagation of impulsive instabilities. Special attention was paid to the possible occurrence of characteristic instabilities during condensation in mini-channels, so-called capillary blocking. The experimental investigation was based on the condensation of R134a and R404A refrigerants in horizontal tubular mini-channels with internal diameters of D = 0.64; 0.90; 1.40; 1.44; 1.92; 2.30 and 3.30 mm. Propagation of impulsive instabilities was a result of a sudden change in the refrigerant flow-rate inside mini-channels.