Measuring local heat transfer by application of Rainbow Schlieren Deflectometry in case of different symmetric conditions

Real‐Time Visualization of Internal and External Concentration Fields in Multiphase Systems via Laser‐induced Fluorescence and Rainbow Schlieren Deflectometry During and After Droplet Production

“…3. The setup is a slightly modified version of the one introduced in Schulz et al 22 where in combination with Schulz et al 23 its application for qualitative mass transfer measurements and quantitative heat transfer measurements has been shown successfully. The setup is based on an optical aluminum rail (type X95) as main axis where the optical components are aligned on.…”

“…2.3 the optical cage system is opened between the collimating and the collecting lens. In contrast to 22 the laser‐driven broadband light source (LDLS) Energetiq EQ‐99XFC is used for illumination and fiber‐coupled ( d = 230 µm, NA = 0.22, L =1 m) to a 30 µm wide slit aperture, which is fixed at the center of the optical cage and defines the main optical axis. An iris diaphragm is used to control the diameter of the light beam emitted through the apparatus to reduce optical aberration.…”

“…For RSD measurements a color scale filter is positioned in the focal plane of the collecting lens via a yz ‐translation mount for rectangular optics. Inspired by Greenberg et al 14 one‐dimensional color scale filters with linear change of hue value in one direction and constant hue values in the other direction are applied (see 22 for details and calibration of the system). A colored 4 MP CMOS‐highspeed camera (Vieworks VC‐4MC‐C180EO‐CM) is used in conjunction with a 12x Zoom lens (LaVision) for magnification.…”

“…3. The setup is a slightly modified version of the one introduced in Schulz et al [22] where in combination with Schulz et al [23] its application for qualitative mass transfer measurements and quantitative heat transfer measurements has been shown successfully. application of the calibration curve differences in hue values between the experimental and reference image can be correlated to the displacement on the filter in y or z direction.…”

“…1b) by application of Rhodamin 6G is not suitable due to an overlighting effect of the inside of the drop: The hydrophobic nature of the dye necessitates larger laser power for the visualization in the surrounding water, which in turn leads to the overexposure inside the drop. To circumvent this problem RSD is used for visualization of the concentration distribution outside of the droplet (as shown exemplarily in 9, 23), while LIF measurements are used inside the droplet 5, 6.…”