A New Method for Determining Interfacial Tension: Verification and Validation

Surface tension is a meaningful parameter influencing boiling and condensation in macroscopic scale, in confined spaces, or for nanofluids; it further affects boiling with surfactants. Surface, or interfacial, tension is an important property in the research into increasing heat transfer, enhancing efficiency of photovoltaic systems, improving engine operation, or forming drugs or polymers. It is often determined using axisymmetric drop shape analysis based on the differential equations system formulated by Bashforth and Adams. The closed-form expression of the interface shape states the radii defining the bubbles are the negative numbers, which causes the temperature profile drops along the heat transfer direction, e.g., in the Wisniewski formulas for the temperature in the vapor bubbles; moreover, the drop, or bubble, possesses only one main radius of curvature, which may reduce the number of the unknowns and equations in the Bashforth and Adams algorithm. An alternative method applying the closed-form expression for the droplet shape is validated for the water (denser) drop flowing down in octane (the lighter liquid); its spare equation is used for verifying the outcomes.