Temperature and velocity field mappings for micro-scale heat and mass transport phenomena

Flow and thermal characteristics are studied for capillary pores with free surfaces ranging from 10-mm to 10-μm diameter. A standard finite volume method (FVM), in association with the well-established boundary-fitted coordinate transformation (BFCT), is used to numerically solve the governing equations for primitive scalar variables of velocity components, pressure and temperature. Calculation results show that the convection-driven circulation dominates the flow and thermal fields of large pores, larger than 1.0-mm diameter, and the thermocapillary phoresis effect is significant over the viscous effect. With a diameter of less than 1.0-mm, the flow circulation diminishes and the interfacial evaporation dominates to establish nearly stratified flow patterns, parallel to the pore wall.; A two-color laser induced fluorescence (LIF) technique has been developed and examined for use in full-field temperature mapping of a micro-scale field-of-view in water. The ratiometric technique, using two fluorescence emission intensities, provides a formidable correlation with temperature that does not depend on the laser illumination intensity variation and is free from possible bias occurring from background noise. An extensive calibration for the intensity ratio versus temperature has been performed using a constant-temperature bath and the calibration results have been statistically analyzed to estimate measurement uncertainties. The developed technique measures thermally stratified fields with known temperature distributions that are established inside 10-mm, and 1-mm path cuvettes to ensure measurement accuracy and spatial resolution for potential microscale applications.; Finally, comprehensive measurements for velocity and temperature fields have been conducted. A Micro PIV system has been setup to measure the buoyancy driven velocity fields in a 1-mm heated channel. Fluorescence microscopy is combined with an MPIV system to obtain enough intensity images and clear pictures from nano-scale fluorescence particles. The spatial resolution of the Micro PIV system is 512-nm and the error due to Brownian motion is estimated 1.05%. Measured velocity and temperature fields are compared with numerical results to examine the feasibility of development as a diagnostic technique.