ID 65

High Pressure Measurements of Interfacial Tension Comparing Two Techniques

 

Abstract:

Two measurement techniques, the pendant droplet and the capillary wave method, have been used to measure the interfacial tension (IFT) of heptane-CO2 and dodecane-CO2 in pressurized and heated environments. The motivation of this work is to discuss IFT changes that occur in hydrocarbon mixtures as the critical point is approached and to compare the two measurement techniques. Understanding high pressure, transient-temperature processes involving atomization and mixing is of critical importance to the prediction of spray combustion, which is utilized in rocket, turbine and diesel engines. This paper presents measurements of IFT over a range of temperatures (20-270C) and pressures (0.7-5.5 MPa). The pendant droplet technique involves measuring the shape of a hanging droplet while the capillary wave method measures waves excited on the surface of a pool. Associated uncertainties and differences in experimental environments for both methods will be described. The two techniques have different advantages and enable us to examine different local environments, e.g. near-interface species concentrations, providing complementary data but different absolute values. Differences in IFT measurements for both techniques will be discussed.