Detection based on rainbow refractometry of droplet sphericity in liquid–liquid systems

Abstract

The shape of droplets in liquid-liquid systems influences their mass and momentum transfer processes. The deviation from sphericity of rising droplets in liquid-liquid systems was investigated for different droplet sizes. Rainbow refractometry permits one to test, in this case, whether the use of laser-optical particle sizing will be correct or faulty. Since the assumption of spherical particle geometry is a general basis of laser-optical particle-sizing techniques such as rainbow refractometry or phase Doppler anemometry, deviation from the spherical shape results in a measuring error. A sphericity check based on rainbow refractometry is introduced.

Mass Transfer Processes in Liquid-Liquid Systems with Surfactants

“…The fundamental physics of RBR and the details of the experimental setup are described in [4] and [5] with great care for details. The light scattering theory that is relevant to RBR is further described in [8].…”

“…Homogeneous equilibrium concentration as well as timedependent concentration during the mass transfer process can be detected by RBR. Further more, droplet size and sphericity can be determined by evaluating the angular frequency of the rainbow [5]. Besides fluid dynamics and the gradients of concentration in-and outside the droplet, i.e., the conditions near the phase boundary, influence the mass transfer.…”

Supernumerary spacing of rainbows produced by an elliptical-cross-section cylinder II Experiment

“…22 Two experimental tests for asphericity have been proposed for rejecting rainbow refractometry measurements made on aspherical droplets. 23,24 It appears that the size of the error in n and a caused by either droplet asphericity or uncertainty in the measured values of a max and b max has not been studied systematically. We derive these errors as follows.…”

Instrumentation of rainbow refractometry: portable design and performance testing

“…As one of advanced optical measurement methods, rainbow refractometry [4][5][6][7] has attracted much attention. By recording and analyzing the elastic scattering light around the rainbow angle, it is capable of in situ simultaneous measurement of physical and thermochemical parameters of droplets such as size, refractive index (RI), RI gradient [8][9][10][11], temperature (or concentration [12][13][14][15]), non-sphericity [16][17][18][19][20], and droplet size variations at the nanoscale [21,22].…”