Study of heat dissipation process from heat sink using lensless Fourier transform digital holographic interferometry

Single-shot phase-shifting image-plane digital holography with tri-focal Fibonacci-Billet split lens

Phase-shifting holography has been widely applied in the field of non-destructive testing and interference imaging. Compared to the previous single-shot phase-shifting holography, here tri-focal Fibonacci-Billet split lens was introduced into Mach-Zehnder interferometer, in which the upper half of the Fibonacci-Billet split lens can realize three phase-locking copies of the planar reference wave and the lower half is used to generate three identical copies of object. The interference pattern is recorded by a detector in one single exposure. The test object can be reconstructed by three-step phase-shifting interferometry. The corresponding experiment is carried out to verify the effectiveness of this method. With advantages of real-time reconstruction and amplitude-only diffraction lens, it is very useful for fast imaging and optical element detection.

Acceleration of the Measurement Time of Thermopiles Using Sigma-Delta Control

This work presents a double sliding mode control designed for accelerating the measurement of heat fluxes using thermopiles. The slow transient response generated in the thermopile, when it is placed in contact with the surface to be measured, is due to the changes in the temperature distributions that this operation triggers. It is shown that under some conditions the proposed controls keep the temperature distribution of the whole system constant and that changes in the heat flux at the thermopile are almost instantaneously compensated by the controls. One-dimensional simulations and experimental results using a commercial thermopile, showing the goodness of the proposed approach, are presented. A first rigorous analysis of the control using the Sliding Mode Control and Diffusive Representation theories is also made.

Thermal hydraulic performance of a microchannel heat sink for cooling a high-power diode laser bar

Numerical and analytical methods are employed to investigate the thermal and fluid flow performance of a microchannel heat sink for cooling a high-power diode laser bar. Heat transfer characteristics and pressure drop in the microchannel under different flow rates are studied. A thermal resistance network, which is proved to have less than 5.4% error, is proposed to characterize the resistance components for the microchannel heat sink. Both numerical modeling and thermal resistance network analysis are verified by experimental results based on the wavelength shift method. Two new heat sinks with more uniform temperature distribution for laser emitters compared with the existing design are presented, and their performance is validated by numerical modeling and spatially resolved spectrum measurements.