h i g h l i g h t sMean bubble size, and size distribution in vertical gas-liquid Taylor vortex flow. Mass transfer coefficients for vertical gas-liquid Taylor vortex flow. Wall-driven shear produces prolate rather than oblate bubble shapes. Bubble size and spatial distribution explains low mass transfer coefficients. High wall area in annular geometry has significant impact on mass transfer. a b s t r a c tExperimental measurements of the volumetric liquid mass transfer and bubble size distribution in a vertically oriented semi-batch gas-liquid Taylor-Couette vortex reactor with radius ratio g = r i /r o = 0.75 and aspect ratio C = h/(r o À r i ) = 40 were performed, and the results are presented for axial and azimuthal Reynolds number ranges of Re a = 11.9-143 and Re H = 0-3.5 Â 10 4 , respectively. Based on these data, power-law correlations are presented for the dimensionless Sauter mean diameter, bubble size distribution, bubble ellipticity, and volumetric mass transfer coefficient in terms of relevant parameters including the axial and azimuthal Reynolds numbers. The interaction between wall-driven Taylor vortices and the axial passage of buoyancy-driven gas bubbles leads to significantly different dependencies of the mass transfer coefficient on important operating parameters such as inner cylinder angular velocity and axial superficial gas velocity than has been observed in horizontally oriented gas-liquid Taylor vortex reactors. In general, the volumetric mass transfer coefficients in vertical Taylor vortex reactors have a weaker dependence upon both the axial and azimuthal Reynolds numbers and are smaller in magnitude than those observed in horizontal Taylor vortex reactors or in stirred tank reactors. These findings can be explained by differences in the size and spatial distribution of gas bubbles in the vertically oriented reactor in comparison with the other systems.

Dielectric materials with good thermal transport performance and desirable dielectric properties have significant potential to address the critical challenges of heat dissipation for microelectronic devices and power equipment under high electric field. This work reported the role of synergistic effect and interface on through-plane thermal conductivity and dielectric properties by intercalating the hybrid fillers of the alumina and boron nitride nanosheets (BNNs) into epoxy resin. For instance, epoxy composite with hybrid fillers at a relatively low loading shows an increase of around 3 times in through-plane thermal conductivity and maintains a close dielectric breakdown strength compared to pure epoxy. Meanwhile, the epoxy composite shows extremely low dielectric loss of 0.0024 at room temperature and 0.022 at 100 ℃ and 10−1 Hz. And covalent bonding and hydrogen-bond interaction models were presented for analyzing the thermal conductivity and dielectric properties.

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