Xiaoshuo Liu

Electronic devices that dissipate high heat flux need compact cooling solutions featuring low thermal resistance and high temperature uniformity. This study proposes a novel hybrid cooling configuration integrating array jet impingement with microchannel heat sinks (MCJHSs) for high-performance electronic thermal management and investigates its flow and thermal performance numerically. The proposed design synergizes the exceptional local convective heat transfer of array jet impingement with a large specific surface area of microchannel structures, while a porous skeleton of 0.15 mm thickness is embedded in the crossflow channel, providing a volumetric enhancement of the heated base. The incorporated porous framework effectively enhances fluid mixing and establishes continuous high-efficiency thermal conduction pathways, thereby delivering a substantially improved overall cooling capacity compared with conventional standalone microchannel and jet impingement cooling schemes. A prototype of the MCJHS was fabricated and tested; the measured outlet velocity and liquid temperature agree well with the simulation results, with the deviations within the respective sensor accuracies, verifying the reliability of the numerical model. On this basis, a comprehensive parametric analysis is performed to systematically quantify the thermal–hydraulic performance of the MCJHS across a wide operational range tailored to electronic cooling scenarios, covering jet velocity, porous filling thickness, and applied heat flux. Key performance metrics, including maximum surface temperature, temperature uniformity, average heat transfer coefficient, and pressure drop, are thoroughly evaluated to elucidate the coupled interaction mechanisms between jet momentum and porous filling thickness. The validated model reveals that the optimal combination of jet velocity and porous filling ratio augments the heat transfer coefficient by approximately 15% and reduces the wall temperature by 18 °C relative to the configuration without the porous skeleton, with the flow resistance remaining within a practically acceptable range. The validated model provides a feasible design strategy and technical reference for the advanced thermal management of next-generation high-power electronic components.

This study aims to investigate the feasibility of ethanol-digested calcium oxide (CaO-E) as a novel dechlorination sorbent for the efficient removal of hydrogen chloride (HCl) from coal-fired flue gas and further evaluate its influence on mercury speciation and transformation in flue gas, thereby addressing the low efficiency and limited multi-pollutant control capability of conventional dry dechlorination technologies. Based on a laboratory-scale injection reaction system, ethanol-digested calcium-based sorbents were injected into simulated coal-fired flue gas to systematically examine the effects of key factors, including Ca/Cl molar ratio, SO₂, and fly ash, on dechlorination efficiency. Density functional theory (DFT) calculations were further employed to elucidate the reaction mechanisms. Meanwhile, mercury-laden flue gas was introduced to investigate the removal characteristics of elemental mercury (Hg⁰) and oxidized mercury (Hg²⁺) by CaO-E. The experimental results demonstrated that ethanol-digested CaO exhibited significantly superior performance compared with untreated samples, and the formation of a porous calcium hydroxide structure was identified as the key factor responsible for its high dechlorination efficiency. When the Ca/Cl molar ratio reached 4.0, the dechlorination efficiency could be stably maintained above 80%. SO₂ showed a pronounced inhibitory effect on the dechlorination process, whereas fly ash exhibited a slight promoting effect. Mercury removal experiments revealed that CaO-E had limited removal capability toward Hg⁰ but effectively reduced the concentration of Hg²⁺. Specifically, when the Ca/Cl molar ratios were 3 and 5, the Hg²⁺ concentrations decreased to 1.4 and 0.6 μg/m³, respectively. This behavior can be attributed to the fact that Hg²⁺ mainly exists in chlorinated forms such as HgCl₂, which possess strong polarity and can be readily adsorbed by the alkaline active sites on the CaO-E surface. In addition, as the dechlorination process proceeded, chlorine-containing species in the flue gas were gradually consumed, suppressing the oxidation conversion of Hg⁰ to Hg²⁺ and thereby further reducing the Hg²⁺ concentration. Theoretical calculations indicated that both HCl and SO₂ could undergo chemisorption on calcium active sites, while HCl possessed a lower reaction energy barrier and therefore dominated the competitive adsorption process, exhibiting preferential reactivity. Overall, ethanol-digested calcium oxide not only demonstrates excellent HCl removal performance, but also shows the capability to regulate mercury speciation in flue gas to a certain extent, providing both theoretical insights and technical support for the synergistic control of multiple pollutants in coal-fired flue gas.

Though spatial arrangement between metal and acid has proven efficiency for enhancing catalytic performance, their precise regulation on controlling the product selectivity and revealing related catalytic mechanism remains scarce. Herein, we report a class of Pd nanoparticles integrated into isoreticular UiO-66-type metal-organic frameworks with or without sulfonic acid groups (denoted UiO-S and UiO), which allows for precise distance tuning between Pd and acid site by controlling UiO-66 interlayer thickness. Unlike traditional studies focusing on substrate/intermediate diffusion by dual-site regulation, we herein demonstrate that significant modulation of electron transfer and proton concentration around Pd over UiO-S@UiO ₂₅ @Pd@UiO switches reaction pathways and profoundly tunes selectivity in acetophenone hydrodeoxygenation. Specifically, we show that UiO-S@UiO ₂₅ @Pd@UiO with a 25 nm separation between Pd and acid sites achieves the highest selectivity (~94%) to phenylethanol via homolytic H ₂ cleavage, mitigating prevalent overhydrogenation pathway; whereas UiO-S@Pd@UiO and UiO@Pd@UiO-S, with closely positioned dual sites, dramatically enhance hydrodeoxygenation activity, and display >99% selectivity to high-energy-density ethylbenzene. Notably, a proton-assisted mechanism involving H ₂ heterolysis is elucidated over UiO@Pd@UiO-S, particularly significant for implementing the catalytic process under mild conditions.