Surface porosity is an important means of enhancing boiling heat transfer. In this paper, two kinds of composite porous structures of surface micropore + square channel and framework micropore + ...square channel were prepared by selective laser melting technology using AlSi10Mg as the powder material. The effect of composites with different pore forms on boiling heat transfer was investigated in pool boiling experiments. It was found that controlling the thickness of the powder layer manufactured by selective laser melting can change the surface roughness of the sample, and the sandblasting treatment reduced the surface roughness of the samples. The average heat transfer coefficient of the rough surface composite porous structure sample was increased by 40% compared to the sandblasted sample. The micropores on the surface of the sample and inside the framework significantly enhanced the heat transfer coefficient of the composite porous structure. The presence of surface micropores increased the heat transfer area and the vaporization core density of the composite porous structure and exhibited excellent heat transfer coefficient improvement in the low heat flux region. The framework microporous composite porous structure can form effective gas–liquid diversion at high heat flux and obtain higher heat transfer performance. The large channel in the composite porous structure is the key control factor of the critical heat flux.
The characteristic flavor of the enzymatic hydrolysate of Lentinus edodes, which was involved in the Maillard reaction by xylose, fructose, glucose, sucrose, mannose, maltose, vitamin C (VC) and ...L-arabinose, was determined and analyzed by gas chromatography-ion mobility spectroscopy (GC-IMS). The characteristic flavor fingerprints of Maillard reaction products (MRPs) of L. edodes enzymatic hydrolysate were constructed. The differences in the characteristic flavors of Maillard reaction with different reducing sugars and VC were compared. The main characteristic flavor, characteristic peak, characteristic marker substance and content were determined, a principal component analysis (PCA) of volatile organic compounds (VOCs) was carried out. The results showed that there were 42 kinds of monomers and some dimers of volatile compounds in the samples including 17 aldehydes, 5 alcohols, 7 ketones, 2 esters, 2 acids, 7 other compounds and 2 ethers. The volatile VOCs of the sample with added sucrose, VC and L-arabinose were significantly higher than those of the enzymatic hydrolysate of L. edodes. After the Maillard reaction, the flavor of the hydrolysate was significantly improved, and the main components changed significantly.
Understanding and solving the problem of hydrogen damage due to the degradation of service performance of high-strength steel caused by hydrogen penetration is a milestone for the reliability ...improvement of high-end hydrogen energy equipment. From the perspective of microscopic hydrogen movement behavior, this study investigated the permeability of hydrogen in base metal (BM) and welded metal (WM) of 2.25Cr–1Mo–0.25 V steel welded joint through electrochemical hydrogen permeation test, and the analytical models of hydrogen penetration and hydrogen diffusion in the welding zone were established, and the effect of adding hydrogen-resistant coatings (HRCs) on hydrogen movement behavior in steel substrate was studied. The results showed that the diffusivity of hydrogen in WM of the welded joint was significantly lower than that in BM, and the hydrogen concentration in BM was higher than that in WM at the beginning of hydrogenation without the addition of HRCs protection, while it tended to be consistent at the later stage. However, the hydrogen concentration in WM was lower than that in BM after adding HRCs and would be always higher than that in BM after a certain period of time, and the difference was directly related to the hydrogen resistance of the coatings. Additionally, the difference between the intermediate and outer layers for the welding zone steel substrate with and without HRCs presented a trend of rapid increase followed by a slow decrease. These findings could provide an important reference value for hydrogen damage protection measures and related researches on HRCs.
Graphic Abstract
•Uniform porous structures (with single pore size) and Composite porous structures（with two different pore sizes) are fabricated by selective laser melting.•Composite porous structure has the best ...heat transfer performance.•Critical heat flux enhancement of up to 3.2 times is achieved.•Gas-liquid flow characteristics of the composite porous structure is analyzed.
Cross scale composite porous structures have been proved to have a better effect on enhanced boiling heat transfer. Accurate control of composite pore size and porous structure thickness is important for the study of enhanced boiling heat transfer. In this study, composite porous structures were manufactured with selective laser melting (SLM) technique from aluminum alloy (AlSi10Mg) powder. The heat transfer characteristics of a composite porous structure with composite pores (0.6 mm small pores and 2 mm large pores) for pool boiling under atmospheric pressure were investigated. A comparative analysis was performed with the uniform porous structure (0.6 mm pores) and the composite porous structure. The results shown that the composite porous structure can significantly increase the critical heat flux (CHF) compared to the plain copper surface. The CHF of the composite porous structure was higher than that of the uniform porous structure with the same height. As the height increases, the nucleate boiling heat transfer performance with composite porous structures will decrease, due to the larger gas–liquid resistance as a result of the height increment. In the range of 1.5–4.5 mm studied in this research, the 1.5 mm high composite porous structure achieves the maximum increase in CHF. The maximum CHF was 346.6 W/cm2, which was 3.2 times that of the plain surface. The large pores in the composite porous structure can play a role of shunting to reduce the escape resistance of the bubbles, which can further enhance CHF.
•Groove structure was fabricated by selective laser melting technique.•Optimum groove length for maximum boiling enhancement is identical to bubble departure diameter.•Maximum critical heat flux ...increased 3.1 times and heat transfer coefficient increased 2 times.•Boiling heat transfer coefficient and critical heat flux decrease with the increase of sample height.
Groove structures were fabricated by selective laser melting (SLM) technique to enhance saturated boiling heat transfer at atmospheric pressure. Prepared groove structures have different groove lengths and heights, and the printing material used is AlSi10Mg. Pool boiling experiments were explored with deionized water as the working fluid, and the heat transfer performance of different groove structures was compared based on smooth surface. It was found that the groove structure can significantly increase the boiling heat transfer coefficient (HTC) and critical heat flux (CHF) compared with the smooth surface. With the increase of groove length, the CHF of the groove structure gradually increases until it reaches the maximum at the groove length of 2.2 mm, which corresponded to the bubble departure diameter. Maximum CHF and HTC improvements were 3.1 times and 2 times, respectively. The HTC and CHF of groove structure decrease with the increase of groove height, which is due to the increase of liquid and vapor flow resistance in the groove. Difference of HTC of samples with the same structure size and different height declines with the increase of groove length. Groove structure facilitates gas-liquid flow and separation, thereby enhancing boiling heat transfer. The semi-melted powder bonding on the surface of the 3D-printed skeleton and the groove structure work together to improve the boiling heat transfer performance.
•High-activity 3D printing AlSiMg monolith catalysts were prepared.•High thermal conductivity of AlSiMg increased the heat transfer capacity.•A distributed parameter model with a reactor scale was ...used.•The activity and thermal conductivity of the catalyst should be optimized synchronously.
3D printing AlSiMg monolith catalysts are more suitable for Fischer-Tropsch synthesis due to their high thermal conductivity and thermally connected nature compared to the rolling FeCrAl monolith catalysts. In this paper, the effects of the catalyst activity and thermal conductivity on the reaction and thermal performance were studied by experiment and simulation. Two catalysts were prepared based on the rolling FeCrAl and 3D printing AlSiMg substrate and were designated as ROL-FeCrAl-MC and 3DP-AlSiMg-MC, respectively. The C5+ yield of 3DP-AlSiMg-MC reached 0.98 g/(gcat•h), 4.44 times that of ROL-FeCrAl-MC. The simulation results indicated that the catalyst activity should be improved synchronously with thermal conductivity to keep the balance between the reaction heat and the heat transfer capacity. The catalyst activity of 3DP-AlSiMg-MC was 67% higher than that of ROL-FeCrAl-MC. It was suited to the high thermal conductivity of 3DP-AlSiMg-MC while that of ROL-FeCrAl-MC was well below expectations.
Extracellular vesicles (EVs) hold great potential in both disease treatment and drug delivery. However, accurate drug release from EVs, as well as the spontaneous treatment effect cooperation of EVs ...and drugs at target tissues, is still challenging. Here, an engineered self‐activatable photo‐EV for synergistic trimodal anticancer therapy is reported. M1 macrophage‐derived EVs (M1 EVs) are simultaneously loaded with bis2,4,5‐trichloro‐6‐(pentyloxycarbonyl) phenyl oxalate (CPPO), chlorin e6 (Ce6), and prodrug aldoxorubicin (Dox‐EMCH). After administration, the as‐prepared system actively targets tumor cells because of the tumor‐homing capability of M1 EVs, wherein M1 EVs repolarize M2 to M1 macrophages, which not only display immunotherapy effects but also produce H2O2. The reaction between H2O2 and CPPO generates chemical energy that activates Ce6, creating both chemiluminescence for imaging and singlet oxygen (1O2) for photodynamic therapy (PDT). Meanwhile, 1O2‐induced membrane rupture leads to the release of Dox‐EMCH, which is then activated and penetrates the deep hypoxic areas of tumors. The synergism of immunotherapy, PDT, and chemotherapy results in potent anticancer efficacy, showing great promise to fight cancers.
Self‐activatable photo‐extracellular vesicles are constructed by loading M1‐macrophage‐derived EVs with bis2,4,5‐trichloro‐6‐(pentyloxycarbonyl)phenyl oxalate, chlorin e6, and prodrug aldoxorubicin. These skillfully engineered extracellular vesicles can actively target tumors owing to their inherent tumor‐homing ability, wherein they exhibit potent trimodal therapy effects in an intersynergistic and self‐controllable way, attributed to the interaction between the engineered EV and the special tumor microenvironment.
The hydrogen production technology based on the in-situ electrically heated structured catalyst (EHSC) has the advantages of compact structure, fast response, and less CO2 emissions. However, there ...is still a lack of research on the temperature distribution of the reactor filled with EHSC. Based on the problem, a CFD model was established, and the temperature distribution was revealed. To further reduce the large temperature difference in axial direction, the effects of the gradient-pitch design and segmented-voltage-control design for the EHSC on the temperature distribution and methanol conversion were studied numerically. The results showed that segmented-voltage-control design can significantly reduce the maximum axial temperature difference, due to the fact that the reaction heat and corresponding Joule heat supplied at each axial section were flexibly well matched. When reaction temperature was 275 °C, the maximum temperature difference decreased from 84.7 °C to 31.1 °C. Moreover, when GHSV was 13000 ml/(g h), methanol conversion was improved by up to 10.9%. The segmented voltage control method for the EHSC provides an opportunity to design an isothermal endothermic reactor under any reaction conditions in the case of further optimization of segmented-voltage-control design.
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•The temperature distribution of the EHSC bed was revealed numerically.•Segmented voltage control method can obviously reduce axial temperature difference.•The maximum axial temperature difference decreased from 84.7 °C to 31.1 °C.•An isothermal endothermic reactor has an opportunity to be approximately realized.•EHSC provides an opportunity to design an isothermal endothermic reactor.
•A novel aluminum-based bionic wick vapor chamber was proposed.•Adjusted the parameters to integrally fabricate a hydrophilic and hydrophobic wicks.•Gyroid bionic structure enhanced heat transfer ...performance of vapor chamber.•Optimized cooling parameters to enhance vapor chamber transfer.
Given the lightweight nature and excellent thermal conductivity of aluminum, it offers significant potential for light-weighting of phase-change cooling components. To further enhance the thermal performance of aluminum-based vapor chambers, this study utilized selective laser melting (SLM) to design and integrally manufacture the slightly oleophilic wick for the condenser of the aluminum-based vapor chamber, along with three different superoleophilic wick structures for the evaporator: the gyroid bionic composite porous wick vapor chamber (GBCPVC), the groove composite porous wick vapor chamber (GCPVC), and the uniform porous wick vapor chamber (UPVC). A water-cooling experimental setup was established, and the effects of wick structure, cooling water flow rate, and cooling water temperature on the maximum heat load, temperature uniformity, and thermal resistance of vapor chambers were systematically investigated. The results indicated that the gyroid bionic porous wick structure significantly enhanced the thermal performance of the vapor chamber. Under the same conditions, GBCPVC exhibited lower thermal resistance and superior temperature uniformity, achieving a higher heat load than GCPVC and UPVC. When the cooling water temperature was decreased, its maximum heat load significantly increased. Specifically, at 15 °C, the maximum heat load for GBCPVC reached 300 W, an increase of 33.33 % and 53.33 % compared to 25 °C and 35 °C, respectively. Conversely, a rise in cooling water temperature enhanced the temperature uniformity and reduced thermal resistance of CBCPVC. At 35 °C and a heat load of 120 W, GBCPVC achieved a minimum thermal resistance of 0.034 K/W and a maximum temperature difference of 1.46 °C. Additionally, an increased flow rate enhanced the maximum heat load of GBCPVC, and under high heat loads, it could also reduce the thermal resistance and improve temperature uniformity. This study provides new insights and solutions for the thermal management of phase-change cooling components in aerospace electronic devices.
