Zhongmin Wan

Anhydrous Proton Conducting Materials Based on Sulfonated Dimethylphenethylchlorosilane Grafted Mesoporous Silica/Ionic Liquid Composite

Efficient membrane proton conductivity at elevated temperatures (>100 °C) and reduced humidification conditions is a critical issue hindering fuel cell commercialization. Herein, proton conducting materials consisting of high surface area acid catalyzed mesoporous silica functionalized with sulfonated dimethylphenethylchlorosilane was investigated under anhydrous conditions. The organic moiety covalently bonded to the silica substrate via active hydroxyl groups on the silica pore surface. The structure and dynamic phases of the attached organic molecule were characterized and qualitatively determined by XRD, TEM, FT-IR, and solid state NMR. The amount of grafted organic molecules was estimated to be 2.45 μmol m(-2) by carbon elemental analysis. The so-formed composite materials showed adequate thermal stability up to 300 °C as determined by TGA. Under anhydrous conditions, ionic conductivity of the composite material upon ionic liquid impregnation reaches a peak value of 1.14 × 10(-2) S cm(-1) at 160 °C associated with the activation energy of 9.24 kJ mol(-1) for proton transport.

Conjugate Numerical Investigation of a Miniature Flat Plate Evaporator of Capillary Pumped Loop

The capillary pumped loop (CPL) is a two-phase thermal control device, which has become more active and interesting in the domain of electronics cooling. A two-dimensional conjugate numerical model for the miniature flat plate capillary evaporator is presented to describe liquid and vapor flow, heat transfer and phase change in the porous wick structure, liquid flow and heat transfer in the compensation cavity and heat transfer in the vapor grooves and metallic wall. The entire evaporator is solved with SIMPLE algorithm as a conjugate problem. The shape and location of vapor-liquid interface inside the wick are calculated, and side wall effect heat transfer limit is introduced to estimate the heat transport capability of capillary evaporator. The influences of different wall materials on the performance of miniature flat plate evaporator are discussed in detail, and the results show that evaporator with combined wall is capable of dissipating high heat flux and stabilizes the electronics devices temperature at a moderate temperature level.

Conjugate Numerical Investigation of Flow and Heat Transfer in a Novel Porous Micro Heat Sink

A novel porous micro heat sink system is presented for dissipating high heat flux of electronic devices. Numerical model for the micro heat sink is proposed to describe heat transfer in the metallic wall and liquid flow and heat transfer in the porous wick structure, and it is solved with SIMPLE algorithm as a conjugate problem. The numerical results showed that the heated surface temperature of porous micro heat sink is low at high heat fluxes. Increasing inlet fluid velocity can greatly decrease the temperatures of the heated surface temperature and bottom surface. The temperature of the heated surface can maintain good isothermal characteristic when inlet located in the bottom of micro heat sink.

Phase change driving mechanism and model for Capillary Pumped Loop and Loop Heat Pipe

A capillary pumped loop (CPL) for the cooling of electronic apparatus was presented, and its operation principle and characteristics were analysed. This paper has pointed out the driving mechanism of the interface which is from phase change of fluid in Capillary Pumped Loop (CPL) and Loop Heat Pipe (LHP). A mathematical model has been developed to describe the driving mechanism. According to the theoretical analysis, there will be an effect on the Yang-Laplace equation and the phase change of the interface because of the heat added to the system. The formulas reflecting relations of the real operating capillary radius with the evaporating temperature and the heat density have been developed to quantitatively evaluate the system characteristic. The model will be a newly driving mechanism for all the capillary wick or micro-groovy channel.