Minqiang Pan

An Innovative Fabrication Process of Porous Metal Fiber Sintered Felts with Three-Dimensional Reticulated Structure

A novel porous metal fiber sintered felt (PMFSF) with a three-dimensional reticulated structure has been produced by the solid-state sintering of copper fibers. The copper fibers, with several microstructures distributed onto the surface, were fabricated using the cutting method. The Scanning Electron Microscope (SEM) results revealed that there were two kinds of sintering joints present in the PMFSFs: fiber-to-fiber surface contact and crossing fiber meshing. In the sintering process, the surface microstructures of the fibers helped to improve the forming process of the PMFSFs, as a result of high surface energy. Furthermore, the effect of different sintering parameters on the forming process of the PMFSFs was studied in detail, including the sintering temperature and holding time. The sintering temperatures had a significant influence on the surface microstructures of single fiber and specific surface area of the PMFSFs, but the holding time did not. The optimal PMFSF with a three-dimensional reticulated structure and larger specific surface area was produced by sintering copper fibers at 800°C for 30 minutes in the reduction atmosphere.

CFD-based Study of Velocity Distribution among Multiple Parallel Microchannels

A three-dimensional computational fluid dynamics (CFD) model was used to calculate the velocity distribution among multiple parallel microchannels with triangle manifolds. The influences of structural parameters on velocity distribution among microchannels were analyzed. The simulation results showed that the velocity distribution became more uniform with larger microchannel length, depth or smaller width. Larger horizontal ordinate, longitudinal ordinate and radius of inlet/outlet, smaller lengths of bottom and side of symmetrical manifolds could favor obtaining narrow velocity distribution among microchannels. Symmetrical manifold structure could achieve more uniform velocity distribution among microchannels than that asymmetrical manifold structure.

Hydrogen production via autothermal reforming of ethanol over noble metal catalysts supported on oxides

Abstract Hydrogen was produced over noble metal (Ir, Ru, Rh, Pd) catalysts supported on various oxides, including γ-Al 2 O 3 , CeO 2 , ZrO 2 and La 2 O 3 , via the autothermal reforming reaction of ethanol (ATRE) and oxidative reforming reaction of ethanol (OSRE). The conversion of ethanol and selectivites for hydrogen and byproducts such as methane, ethylene and acetaldehyde were studied. It was found that lanthana alone possessed considerable activity for the ATRE reaction, which could be used as a functional support for ATRE catalysts. It was demonstrated that Ir/La 2 O 3 prevented the formation of methane, and Rh/La 2 O 3 encumbered the production of ethylene and acetaldehyde. ATRE reaction was carried out over La 2 O 3 -supported catalysts (Ir/La 2 O 3 ) with good stability on stream, high conversion, and excellent hydrogen selectivity approaching thermodynamic limit under autothermal condition. Typically, 3.4 H 2 molecules can be extracted from a pair of ethanol and water molecules over Ir(5wt%)/La 2 O 3 . The results presented in this paper indicate that Ir/La 2 O 3 can be used as a promising catalyst for hydrogen production via ATRE reaction from renewable ethanol.

Preparation of oriented linear copper fiber sintered felt and its performance

Long metal fibers were manufactured in horizontal lathe with a multi-tooth tool. Based on the coarse antler surface structure of copper fibers, a new sintering technology was put forward to manufacture a kind of oriented linear copper fiber sintered felt. The sintering mechanism of oriented linear copper fiber sintered felt was studied. Compared with sintered copper-wire felt, the characteristics of sintered copper-fiber felts were analyzed in details. Owing to the coarse antler surface structure of copper fibers, oriented linear copper-fiber felt was sintered under the condition of micro/nano scale range, and copper fibers easily bonded together in the sintering process. Microchannels with micro-scale coarse antler surface structure were constructed. These characters give oriented linear copper fiber felt some new merits: high filtration accuracy, high flow capability, low resistance loss, good capability to resistance pressure, stable and uniform pore, high specific surface area. The properties of oriented linear copper fiber sintered felt were analyzed.

Fabrication and Characterization of Aluminum Fibers by Peripheral Milling

A novel peripheral milling process with an end milling cutter for manufacturing aluminum fibers is proposed. Most of the cutting is done by the peripheral teeth of the cutter and the chips removed by the teeth form aluminum fibers, while the cutter end has little effect on aluminum fibers. The machining principle and the formation mechanism of aluminum fiber cross-section are presented. The feasibility of this new fabrication process is experimentally investigated under different machining conditions. In addition, influences of cutting parameters on the equivalent diameter, the length, and surface morphology of aluminum fibers are analyzed. Experimental results indicate that aluminum fibers can be successfully manufactured by peripheral milling and the productivity can be improved by increasing the rotational speed n. Smaller radial depth of cut a e , larger rotational speed n, and smaller feed speedv f are in favor of obtaining slim aluminum fibers. The length of aluminum fibers is theoretically determined by the axial depth of cut a p and also actually affected by other cutting parameters. Of all the cutting parameters considered in these experiments, the optimum parameters of a e , n, and v f are 0.3 mm, 118 r/min, and 60 mm/min, respectively.

Performances of electrically heated microgroove vaporizers

Abstract An electrically heated microgroove vaporizer was proposed. The vaporizer mainly comprised an outer tube, an inner tube and an electrical heater cartridge. Microgrooves were fabricated on the external surface of the inner tube by micro-cutting method, which formed the flow passage for fluid between the external surface of the inner tube and the internal surface of the outer tube. Experiments related to the temperature rise response of water and the thermal conversion efficiency of vaporizer were done to estimate the influences of microgrooves direction, feed flow rate and input voltage on the performances of the vaporizer. The results indicate that the microgrooves direction dominates the vaporizer performance at a lower input voltage. The longitudinal microgroove vaporizer exhibits the best performances for the temperature rise response of water and thermal conversion efficiency of vaporizer. For a moderate input voltage, the microgrooves direction and the feed flow rate of water together govern the vaporizer performances. The input voltage becomes the key influencing factor when the vaporizer works at a high input voltage, resulting in the similar performances of longitudinal, oblique and latitudinal microgroove vaporizers.

Manufacturing Heat Pipe by Combined Ploughing-Extrusion Process

Since the capillary structures in the internal wall of heat pipe dominate the heat transfer performance, the research of surface heat functional structure is being gradually extended to the fields of metastructure and microstructure. This paper proposes a combined ploughing-extrusion method with a multi-tooth tool to form the micro-groove structures in the internal surface of copper pipe. Experiments indicate that the combined ploughing-extrusion process can create rougher surface than the single ploughing-extrusion process, and some phoenix-feather-like structures appear. The capillary force comparative experiment indicates that the heat pipe manufactured by the combined method can absorb 0.2ml more liquid than the one made by single process, supposing there is 90ml liquid in the container. The heat transfer testing experiment also indicates this heat pipe can transfer more heat when the inclination angle is small, but with the increase of inclination angle, this superiority becomes not so evident due to the increased reflow resistance. The combined process that comprises more than two processes makes metal yield and generates cracks in the internal wall.Copyright

Sintering formation of oriented linear cutting copper fibers

Abstract The formation mechanism of oriented linear cutting copper sintered felt was analyzed. The influences of sintering temperature, sintering atmosphere and sintering time on the sintering formation were investigated. And the tensile mechanical properties of sintering fibers under different sintering conditions were also analyzed. The results indicate that the formation of sintered necks in the contacted area due to the materials migration of microstructures on the surfaces of fibers promotes the tight connection of oriented linear cutting copper fibers. It is also found that both sintering temperature and sintering atmosphere show important effects on the sintering formation while the influence of sintering time is not so obvious. Sintering at 800 °C for 60 min under low temperature reduction can produce sintered necks to make fibers tightly connect together and maintain the coarse microstructure on the surface of fibers, and the best tensile mechanical property can be obtained as well.

Forming method of wick structure for heat column

Abstract The intensified boiling and condensation wick structures of heat column were designed and manufactured by ploughing-extrusion (P-E) machining method. The forming process and mechanism were analyzed. The results show that the P-E depth plays a decisive role in forming of wick structure. The larger the P-E depth is, the better the surface characteristics are. Only when the groove spacing is in a certain range, superior surface structure can be formed in the wick. The better enhancement boiling structure forms at P-E depth of 0.3 mm, ringed groove spacing of 0.4 mm, and interior angle of radial groove of 3°; the better enhancement condensation structure forms at P-E depth of 0.3 mm, ringed groove spacing of 0.4 mm, and axial grooves spacing of π3 mm.

Fabrication of sintered wick in micro -grooved pipe

The sintering heat pipe is an ideal component in solving the heat dissipation of high heat flux chips. The heat pipe with sintered wick structure in micro-grooved pipe was featured with low heat resistance, high bond strength and hard to dryout. According to the sintering theory, the manufacturing process of sintered wick could be divided into four phases: reduction phase, sintering starting phase, sintering preservation phase and sintering cooling phase. The sintering temperature, sintering time and sintering atmosphere about fabrication of the innovative sintered wick were also inspected. The result was discoveried that 100 mesh spherical copper powders had high porosity and low radial shrinkage at the sintering temperature of 950°C for 3 hours and the mandrel could be easily pulled out. It was also found that the oxidation reduction process could manufacture new micro structure—the segmentation cracks structure on the surface of copper powders.