Papers by Author: Yong Tang

Abstract: This study explores the feasibility of using a novel process, micro planing with multi-cutter, to fabricate graphite composite bipolar plates of proton exchange membrane fuel cells (PEMFCs). Through the use of multi-cutter, this study succeeds in machining micro flow channels with dimensions of 0.2 mm×0.23 mm×0.4 mm (channel width × rib width × depth size) on graphite composite bipolar plate (21 mm × 80 mm × 1.5 mm), in a reaction area of 10 mm × 60 mm. The graphite composite plates fabricated by multi-cutter are tested for cell performance under varying back-pressures. Results show that the cell performance increase with the rising back-pressures and can be promoted apparently by decreasing the size of flow channels.

Abstract: Metallic bipolar plates with unique wave-like microstructure on the bottom of microflow channel have shown promising prospects for the application in proton exchange membrane microfuel cell. A novel method—milling with special thin slotting cutters is developed for fabrication of wave-like microstructure on the bottom of microflow channels. The special thin slotting cutter is manufactured by removing one or several teeth every one tooth of the traditional slotting cutter regularly. Forming mechanism of wave-like microstructure is presented and experimental tests have been conducted for validation of the feasibility of the novel method. Results show that the wave-like microstructure can be successfully fabricated on the bottom of microflow channel. The bottom of bipolar plates with wave-like microstructure is not a flat plane, but a wavy groove. The wavelength and amplitude of wave-like microstructure increase with the increase of feed speed and the number of removed teeth.

Abstract: This paper reports on thermal characterization of edge illumination type LED backlight integrated with heat pipes. Heat pipe is integrated with the panel by phase change flattening and expanding process. Thermal capabilities, including the steady-state working temperature and the temperature uniformity along the panels with heat pipes and without heat pipes are compared and analyzed. Results show that the steady-state working temperature on the panel with heat pipes is 1~6°C lower than that on the panel without heat pipes under power range of 15W to 51W of the LED arrays. And the temperature uniformity along the panel with heat pipes is controlled within 2.0°C.

Abstract: In this work, a solar flat-plate collector test system is developed. The solar flat-plate collectors with anodic coating, chromium coating and blue core coating are tested. The experimental results indicate that the relative absorption ration α/ε of blue core coating is up to 19. The efficiency of collector with blue core coating is 78.66%, which is 5% higher than collectors with the other two types of coatings. In addition, collector with blue core coating has smaller total thermal loss coefficient. The blue core coating can effectively improve the performance of solar flat-plate collectors.

Abstract: The influence of microstructures on wettability on stainless steel was investigated. Two kinds of different microstructures were manufactured by a laser processing method with micro parallel grating and square pillars array. The experimental and theoretical values of contact angle (CA) were obtained. Furthermore, within the groove spacing processing size range in micron scale, the experimental results agreed with the theoretical predictions based on the Wenzel. By the influence of machining and measuring conditions, the experimental values of CA were smaller than the predicted theoretical values. A linear relationship between the CA and the micro-scale structures was obtained, which showed the CA was increased with an increase of groove spacing. With the same structural parameters, the CA of square pillars array microstructures was larger than parallel grating microstructures.

Abstract: This study provides a series of investigation on the morphological characteristics and related mechanisms of a porous metal-fiber sintered felt (PMFSF). Multi-tooth cutting and high-temperature solid-phase sintering are used to create the PMFSF. Based on both modeling and experimental methods, the results suggest that the produced fiber has rough surface and curled shape due to cutting deformation. The processing parameters and material mechanical property both have significant effects on formation of fiber morphology. Results also reveal that the fibers in a PMFSF is randomly distributed and connected with each other by forming sintering necks. Besides, the influences of sintering parameters are also analyzed in this work.

Abstract: A mathematical model for predicting liquid flow velocity in a rectangular microchannel driven by capillary force and gravity is derived. The model takes into account the additional driving force arising from the wettability gradient on inner surface of a microchannel. The results of model prediction show that the velocity of liquid flow decreases with the length of microchannel and the wettability gradient on channel surface will accelerate the motion of the liquid when the flow-front approaches to the end of the microchannel. The analysis of driving force along the moving path matches well with the flow velocity predicted by the model.

Abstract: The porous metal fiber sintered felt (PMFSF), a new catalyst support, was successfully used to construct a methanol steam reforming microreactor for hydrogen production. To study the transport characteristics of PMFSFs, a three-dimensional model with the cubic pore cell structure for PMFSFs was established. Using computational fluid dynamics fluent software, the velocity and pressure distribution when the fluid through the PMFSFs was investigated by changing the porosity of PMFSFs and inlet velocity of the fluid. In addition, fluid temperature distribution was analyzed under different inlet velocities by setting the temperature of fluid and wall. The result shows that the PMFSFs greatly enhance the transport characteristics because of its three-dimensional network structure and microchannel structure, it will become an ideal candidate for catalyst support material.

Abstract: A three-dimensional “fin-groove” composite structure copper current collector was fabricated by micro-ploughing process. 3D and common 2D carbon anodes for lithium- ion batteries were prepared. The electrochemical properties of these electrodes were studied by linear sweep cyclic voltammetry (CV) and charge-discharge (C-D) test. 2D anode showed high contact resistance, high coulombic efficiency but poor cycle performance. In contrast, 3D anode showed the structure superiority in reinforcing bonding force between active materials and copper substrate, improving the conductive environment and alleviating volume changes. It was believed that 3D anode can keep high coulombic efficiency and improve the cycle performance of lithium- ion batteries.

Abstract: A novel heat sink was fabricated for packaging cooling of high power LED. Enhanced boiling structures in the evaporation surface were processed by ploughing-extrusion (P-E) and stamping methods, respectively. The cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. The experimental results showed that phase change heat sink was provided with a good heat transfer capability and the temperature of phase change heat sink reached 86.8°C under input power of 10W LED at ambient temperature of 20°C.