Modeling of a Two-Phase Region Length of the Condensation of R134a and R404A Refrigerants in Pipe Minichannels With Periodic Hydrodynamic Instabilities

Abstract

The heat removal process of a compact condenser in a refrigeration compressor system, constructed on the basis of pipe minichannels, occurs in three regions: the removal region of superheat, the two-phase proper condensation region, and the liquid subcooling region. The intensity of heat removal in the two-phase region depends on the heat efficiency of the condenser. The length of this region is determined by the process parameters and the external influences. This paper analyzes the influence of periodically generated hydrodynamic disturbances on the length of the condensation region for R134a and R404A refrigerants. Experimental tests were conducted for six diameters of pipe minichannels: 0.64, 0.90, 1.44, 1.92, 2.30, and 3.30 mm. A range of frequencies from 0.2 to 5 Hz of periodically generated disturbances showed an explicit and unfavorable influence on the decrease of the length of the proper condensation region. This influence reduced the efficiency of the process. A computational model was developed to calculate the length of the two-phase region under disturbance conditions. The model proposed was verified by the results of the experiment, and compliance was obtained in the range of ±15%.