Drop shape analysis system model SL200HP is designed for measurement of contact angle, surface tension (liquid-gas) or interfacial tension (liquid-fluid) under such special conditions as ultra-high pressure (max 75Mpa) and high temperature (max 200℃) . Thanks for its heating cell for such viscous sample as crude oil, SL200HP is the only instrument that can be used for application of tertiary oil recovery (EOR) especially for measurement of interfacial tension between ASP-crude oil.

1, Measurement of contact angle / surface tension under ultra-high pressure and high temperature environment
Contact angle, θ, is defined as the angle between tangent of gas-liquid interface and that of solid-liquid interface formed at the three phases' boundary where liquid, vapor and solid intersect.
1. Contact angle measurement: The drop formed under high pressure is usually shaped into an approximate ellipsoid in 3D due to its gravity, hence we adopt Young-Laplace equation fitting technology（ADSA?）to fit its shape in 2D, and then calculate its contact angle between liquid drop and solid under gas or fluid surroundings.
2.?Surface?tension?measurement?under?pressure and high?temperature: For drop under high pressure and high temperature, its surface chemical properties can be characterized by its drop shape profile; hence we here analyze it using Young-Laplace equation fitting method (ADSA?) via sessile drop method; volume and surface tension can be calculated then by pendant drop, sessile drop or constrained sessile drop method.
Young-Laplace equation and software CAST?3.0
First, single or several dynamic images of drop/bubble are captured for us to analyze its key information like drop shape edge and geometric dimension via sub-pixel image recognition technology; By inputting some important parameters like density, gravitational acceleration, magnification and others, we compare and fit the real drop shape profile with theoretical curve generated by sophisticated mathematical analytical models (such as circle, ellipse, polynomial, spline curve and especially Young-Laplace equation fitting) using least square method; and finally surface tension of liquid-gas, interface tension of liquid-liquid, contact angle of solid-gas/liquid-liquid-solid are calculated.
Our great achievement is: initiating ADSA based Young - Laplace equation fitting method and apply it into analysis of interfacial chemical properties after our 3 decades endeavor. Equation of Young-Laplace is as below:
γ(1/R_1 +1/R_2 )=Δρgz+2γ/b