Modeling of the propagation of a pressure wave during the condensation process of R134a refrigerant in a pipe minichannel under the periodic conditions of hydrodynamic disturbances

The present paper covers the results of theoretical and experimental investigations concerning the propagation of a pressure wave triggered by external hydrodynamic influences in the condensation process of R134a refrigerant in pipe minichannels with an internal diameter of d = 0.64–3.30 mm. An ensemble-averaged gas-liquid two-fluid model with slippage of the velocity of phases was used when there was no thermodynamic equilibrium between the phases. The momentum and mass conservation equations were used for the analysis. In the model, the average values of parameters were assumed for the individual phases that describe the state of the system. The influence of the friction resistances of the flow in minichannels was also taken into consideration. The heat transfer between phases in the condensation process was described with Fourier’s one-dimensional equation. With the use of the author’s self-developed computational code, the following were defined in the MATLAB 8 program: the propagation velocity of the pressure wave cTPF, the attenuation coefficient η of this wave and the dependence of these quantities on the angular frequency ω of disturbances generated and on the void fraction α. The results of the model calculations were compared with the results of the experimental investigations, and satisfactory compliance was obtained.