Experimental determination of gas–liquid interfacial tension for POE ISO 10/R-134a mixtures using the maximum bubble pressure method

This paper presents the development of an experimental apparatus designed for measuring the interfacial tension of a POE ISO 10/R-134a mixture under varying solubility conditions using the maximum bubble pressure method (MBPM). The apparatus features two capillary tubes immersed in a liquid volume against which a vapor bubble expands to determine interfacial tension. Key parameters of the MBPM, including bubble formation frequency and chamber volume, were meticulously fine-tuned for accurate calibration. Calibration was performed using a water/ \(\hbox {N}_2\) ${\text{N}}_2$ mixture within the same apparatus, and the results were validated against established literature data. The experimental setup exhibited high sensitivity to bubble formation frequency, requiring precise maintenance at a constant rate of 1.0 Hz. Notably, the two-capillary model demonstrated superior performance compared to classical constant-adjusted models. A satisfactory fit for the R-134a/POE ISO 10 system was achieved with a mixing-law coefficient of \(r=1/7\) $r=1/7$ , highlighting significant deviation from ideal mixture behavior ( \(r=1\) $r=1$ ).