Experimental investigation of single bubble growth in the boiling of the superheated liquid mixed refrigerants

The reduction of the bubble growth rate in mixed liquid refrigerants is one of the main reasons for the reduction of the boiling heat transfer coefficient. To study the mass diffusion effect and the reduction of the bubble growth rate in boiling of non-azeotropic mixtures, an experiment was conducted to investigate the bubble growth rates of R142b, R134a, isobutane and R142b/R134a mixtures in a vertical transparent quartz tube. The pressure used in this experiment ranged from 0.2 to 0.47 MPa, and the superheats ranged from 1.5 to 23.3 degrees C. Moreover, in order to obtain a uniformly superheated liquid, the bubbles were grown at a single nucleation site, and the departure frequency for the successive bubbles was lower than 20 Hz. Experimental bubble growth constants were obtained, and the reliability of the experimental study was supported by theoretical models for pure refrigerants. Additionally, for the study of bubble growth rate in binary mixtures, the attenuation factors for superheat were calculated and compared with different proposed models. The experimental attenuation factors were much smaller than the calculated results. Thus, a correlation was identified, and the errors were primarily in the range of -30% to +30%. (C) 2018 Elsevier Ltd. All rights reserved,