Conventional External Heating Research Articles

Enhanced post-combustion CO2 capture and direct air capture by plasma surface functionalization of graphene adsorbent

Graphene has enormous potential to capture CO2 due to its unique properties and cost-effectiveness. However, graphene-based adsorbents have drawbacks of lower CO2 adsorption capacity and poor selectivity. This work demonstrates a one-step rapid and sustainable N2/H2 plasma treatment process to prepare graphene-based sorbent material with enhanced CO2 adsorption performance. Plasma treatment directly enriches amine species, increases surface area, and improves textural properties. The CO2 adsorption capacity increases from 1.6 to 3.3 mmol/g for capturing flue gas, and from 0.14 to 1.3 mmol/g for direct air capture (DAC). Importantly, the electrothermal property of the plasma-modified aerogels has been significantly improved, resulting in faster heating rates and significantly reducing energy consumption compared to conventional external heating for regeneration of sorbents. Modified aerogels display improved selectivity of 42 and 87 after plasma modification for 5 and 10 min, respectively. The plasma-treated aerogels display minimal loss between 17% and 19% in capacity after 40 adsorption/desorption cycles, rendering excellent stability. The N2/H2 plasma treatment of adsorbent materials would lower energy expenses and prevent negative effects on the global economy caused by climate change.

Battery-Operated and Self-Heating Solid-Phase Microextraction Device for Field Detection and Long-Term Preservation of Mercury in Soil.

The application of headspace solid-phase microextraction (HS-SPME) for mercury preservation and detection still has several shortcomings, including the use of high-temperature desorption chamber, the consumption of expensive reagent (NaBEt4 or NaBPr4), and analyte loss during sample storage. Herein, a self-heating HS-SPME device using a gold-coated tungsten (Au@W) fiber was developed for the field detection of mercury in soil by miniature point discharge optical emission spectrometry (μPD-OES). Hg2+ was reduced to Hg0 with NaBH4 solution and then preconcentrated with the Au@W fiber. The adsorbed Hg0 could be rapidly desorbed by directly heating the fiber with a mini lithium battery and subsequently detected by μPD-OES. A limit of detection (LOD) of 0.008 mg kg-1 was obtained with a relative standard deviation (RSD) of 2.4%. The accuracy of the self-heating HS-SPME was evaluated by analyzing a soil certified reference material (CRM) and nine soil samples with satisfactory recoveries (86-111%). Compared to the conventional external heating method, the proposed method reduces desorption time and power consumption from 80 s and 60 W to 20 s and 2.5 W, respectively. Moreover, the self-heating device enables the μPD-OES system to remove the high-temperature desorption chamber, making it more compact and suitable for field analytical chemistry. Interestingly, the Au@W SPME fiber can be also used for the long-term preservation of mercury with a sample loss rate <5% after 30 days of storage at room temperature.

UV-Laser ablation enhanced Joule-heating catalyst support for electrified MSR in microreactor

Methanol is a promising hydrogen carrier, where hydrogen-rich gas can be produced by methanol steam reforming (MSR). However, this method of releasing hydrogen is highly energy consuming. Herein, the Joule-heating catalyst support (JHCS) was fabricated by a FeCrAl metal to enhance the efficiency of electrification, replacing the conventional external heating method. The heat can be provided for the reforming reaction directly inside the microreactor by the Joule-heating method. The Joule-heating reactor showed a faster thermal response than the externally heated reactor; the start-up heating time and the time of a start-stop cycle are about 75 % and 50 % of those for external heating, respectively. The methanol conversion rate of the Joule-heating microreactor was 91.45 % at 280 °C, improved by nearly 30 % than the external heating counterpart. The consumed power density of the Joule-heating microreactor was 2 W/cm3, only 15.8 % of external heating (12.61 W/cm3). The reforming efficiency reached 51.91 % without any waste heat recovery measures, about 4 times of the external heating method. Heat transfer simulation verified the minimal radial temperature gradient in the microreactor eliminated by JHCS. The proposed JHCS method demonstrates a uniform microreactor temperature distribution and superior hydrogen production performance with lower power consumption.

Effect of Internal AC Heating on the Temperature Homogeneity of Different Size Battery Cells

Rapidly warming up batteries is an important challenge both for conventional lithium-ion batteries, which operate best over 15 °C, and for most solid-state batteries, which currently require operating temperatures over 60 °C. Internal heating using an alternating current (AC) has been proposed as a possible solution in automotive applications, with faster heating rates possible than conventional external heating methods. This paper investigates the performance of internal AC heating on cells of different sizes, for both cylindrical and pouch formats. A novel experimental arrangement is used in which two cells are tested in series while connected with opposing polarity to create a zero-voltage string, allowing the use of less expensive testing equipment. The results show that larger cells exhibit a considerably greater distribution of surface temperature than smaller format cells during internal heating. This is likely due to the more extreme spatial variation in current density in the current collectors, causing an uneven distribution of internal heat generation. This highlights a significant difference compared to external heating methods, which are not affected by this, and has important implications for temperature measurement and battery management if this type of internal heating is to be used, since temperature sensors must be placed in hot spots or supplemented by validated models to ensure all parts of the battery stay within safe temperature limits.

Localized induction heating of metallic spacers for energy-efficient membrane distillation

Despite membrane distillation (MD) being well acknowledged as a green technology for water treatment, it remains unattractive for commercial implementation due to limited energy efficiency, and temporal fluctuations in sustainable energy sources like waste heat and solar. The induction heating of metallic spacers addresses these shortcomings. In this study, we harnessed the high thermal conductivity of nickel (Ni) spacers and their capacity to be inductively heated to improve the energy efficiency of direct contact MD, and benchmarked the performance against the conventional external heating of the bulk feed and the use of polypropylene (PP) spacers. Both simulations and experiments were performed. Noteworthy results include: (i) induction heating gave higher flux and energy efficiency than the conventional external heating and use of PP mesh, particularly at lower flowrates; and (ii) induction heating was able to supplement external heating without a decrease in energy efficiency, which makes it a promising method to circumvent the problem of temporal fluctuations of waste or solar heat. This study demonstrated the feasibility of localized induction heating of metallic spacers in MD, which has potential for further improvements through optimizations of the thermal conductivity and geometry of the spacer, and energy efficiency of the induction heater.

10-Min Fast Charging of Automotive Li-Ion Batteries at an Elevated Temperature

Fast charging technology is widely recognized as a critical factor in bolstering consumer appeal of battery electric vehicles (BEVs). The U.S. Department of Energy (DOE) has set a goal of developing extreme fast charging (XFC) battery technology that can recharge a 200-mile BEV in 10 minutes. A key barrier to XFC of automotive Li-ion batteries is the issue of lithium plating, which drastically deteriorates battery life and even induces hazardous consequences. Fundamentally, lithium plating is affected by the rate capability of ion transport in the electrolyte, intercalation reaction at graphite surface, and solid-state diffusion in graphite particles. Research in the literature, accordingly, has been focusing on improving electrolyte transport properties, enhancing charge transfer kinetics, or utilizing smaller particles. Li-ion battery is well known for its trade-off nature. Improving one property without sacrificing others is always challenging. An alternative approach to suppressing lithium plating is to elevate charge temperature. Indeed, an increase in temperature can boost the rate capability of the above three processes simultaneously. However, an elevated temperature, on the other hand, accelerates the solid-electrolyte-interphase (SEI) growth. Owing to the interplay between lithium plating and SEI growth, it is universally believed that Li-ion batteries have an optimal life at room temperature. [1] In 2018, our group presented a numerical study revealing that the optimal temperature of a Li-ion battery, in contrary to the conventional wisdom, actually increases with an increase of charge rate and/or energy density.[2] Enlightened by this finding, we proposed a heated-charge method [2, 3] to charge a Li-ion cell at an elevated temperature of 40-60oC to enable XFC without Li plating. Very recently, Tesla has applied this concept in its V3 superchargers. Using an ‘On-route Battery Warmup’ strategy, Tesla vehicles are designed to arrive at a fast charging station at a temperature of ~40oC, demonstrating the commercial viability of charging a BEV at an elevated temperature. Nevertheless, a potential issue of Tesla’s on-route warmup strategy is the slow heating speed, making a battery stay at a high temperature for a long period of time and hence incurring excessive SEI-induced degradation. Currently, we are developing an XFC battery based on the heated-charge method. With a novel structure, our battery has >100x faster heating than conventional external heating methods, thereby limiting the duration of heating to a matter of seconds. More profoundly, we will present in this talk that our battery, having an energy density of 210 Wh/kg, could sustain 2,000 cycles of 10-min (6C) charge to 80% state of charge with only 7% capacity loss.

(E)-3-[4-(Pent-4-en-1-yloxy)phenyl]acrylicc Acid

(E)-3-[4-(Pent-4-en-1-yloxy)phenyl]acetic acid is one of the useful components of liquid crystal materials which can be produced through Williamson ether synthesis by synthesizing 4-hydroxy-cinnamic acid and 5-bromo-1-pentene. Although Williamson ether synthesis is generally slow under conventional external heating conditions, microwave irradiation was effective for significant acceleration of the etherification. Furthermore, we demonstrated the rapid and continuous synthesis of (E)-3-[4-(pent-4-en-1-yloxy)phenyl]acetic acid, using a microwave-assisted flow reactor developed by us, in which the blockage by salt precipitation was suppressed by the continuous addition of an aqueous methanol solution after the reaction cavity.

Effects of Ohmic Heating, Including Electric Field Intensity and Frequency, on Thermal Inactivation of Bacillus subtilis Spores

Methods for microbial inactivation are important in the food industry; however, conventional external heating (CH) reduces food quality. Accordingly, the nonthermal effects of ohmic heating (OH) on Bacillus subtilis spores in a sodium chloride aqueous solution at 101°C (i.e., the boiling point), as well as the effects of electric field intensity and frequency during OH, were investigated. Survival kinetics were compared between OH and external CH. The inactivation effect on B. subtilis was greater for all electric field conditions (5, 10, and 20 V/cm) than for CH. In particular, 20 V/cm showed a significantly higher inactivation effect (P < 0.05) on B. subtilis than those of CH at 8, 10, 12, 14, and 16 min. The survival data were fitted to various primary kinetic models. In the Weibull model and the log-linear model, there were significant differences (P < 0.05) in the rate parameters δ and kmax between OH at 20 V/cm and CH. However, there were no significant differences (P > 0.05) in survival kinetics between 20, 40, and 60 kHz; B. subtilis spores were inactivated more efficiently as the frequency increased. B. subtilis spores were almost completely inactivated at 14 to 16 min for the 60-kHz treatment, but spores were still alive at 20 and 40 kHz for the same treatment times. These results demonstrated that OH inactivates B. subtilis spores more effectively than CH. OH conditions with high electric field intensities and high frequencies resulted in efficient B. subtilis spore inactivation.

Catalytic performances of perovskite oxides for CO oxidation under microwave irradiation

Microwave-assisted heterogeneous catalytic oxidation of CO over ABO3 type perovskite oxides (A: La; B: Mn, Fe, Co) was carried out and the factors controlling the catalytic properties were investigated. The heating behavior of perovskite oxides depended on the physical state of catalyst particles and catalyst compositions. Catalytic activity of the perovskite oxide decreased in the order of LaCoO3>LaMnO3>LaFeO3 under conventional heating, although LaMnO3 exhibited similar activity to LaCoO3 under microwave heating. The partial substitution of A site cation La by Sr enhanced the heating and catalytic properties under microwave heating conditions. Catalytic properties of the perovskite oxides under microwave heating were compared with those under conventional external heating.

Polymer optical fiber tapering without the use of external heat source and its application to refractive index sensing

We perform a pilot trial of the highly convenient taper fabrication of perfluorinated graded-index polymer optical fibers. Instead of conventional external heating, we utilize internal heating caused by high-power propagating light (500 mW in this experiment). An approximately 4-mm-long section of a polymer fiber is tapered, and the outer diameter of the ∼2-mm-long waist around its midpoint is approximately 200 µm, which is quite uniform with a standard deviation of 4.3 µm. The polymer fiber taper fabricated by this technique is shown to be capable of generating evanescent waves and thus measuring the refractive indices of liquids from 1.333 to 1.410.

Modeling of fish boiling under microwave irradiation

A traditional method of cooking fish known as fish boiling in which microwave irradiation was used instead of conventional external gas heating was investigated, and the microwave cooking process was studied and simulated via a three-dimensional finite element computational model.Although this cooking method is complex in that it contains both liquid and solid materials, and convection occurs inside the liquid during processing, the changes in temperature were successfully predicted by coupling the analysis of the electromagnetic field and heat transfer. We proposed an easier way to simulate the temperatures of the liquid inside which free convection occurred during heating. The appropriate value of the thermal conductivity of the liquid material for microwave cooking was validated by the experiment. On the basis of simulated temperature profiles and the parameters deduced from Differential Scanning Calorimetry (DSC) experimental data, the time-dependent degrees of protein denaturation during cooking were also estimated.The temperature and denaturation information were finally formatted in Femap and animated so that they could be investigated easily.

Gold nanorods coated with a thermo-responsive poly(ethylene glycol)-b-poly(N-vinylcaprolactam) corona as drug delivery systems for remotely near infrared-triggered release

Poly(ethylene glycol)-b-poly(N-vinylcaprolactam) (PEG-b-PNVCL) copolymers are prepared from a PEG macro-chain transfer agent in DMF at 65 °C via reversible addition–fragmentation chain transfer (RAFT) polymerization. The well-defined PEG114-b-PNVCL237 copolymer with a cloud point temperature of 39 °C is used for the formation of a thermo-responsive polymer corona on the surface of gold nanorods (GNRs) via a “grafting-to” approach. Thermo-responsiveness and thermo-dependent optical properties of the as-obtained GNR@PEG-b-PNVCL nanoparticles are studied with dynamic light scattering and UV/vis spectroscopy techniques. Near infrared (NIR)-induced heating of GNR@PEG-b-PNVCL is also explored in aqueous suspension under NIR laser irradiation (802 nm, up to 250 mW). The potential of these GNR@PEG-b-PNVCL nanoparticles to be used as smart drug delivery systems (DDS) is then studied. A hydrophilic drug model, Rhodamine® B, is used to assess the guest loading capacity, and triggered release behaviours are then evaluated under conventional external heating or internal heating induced by remote NIR irradiation. Cytotoxicity evaluation of the GNR@PEG-b-PNVCL against the fibroblast-like L929 cell line is carried out via the MTS assay in order to confirm the improved biocompatibility of the GNRs after polymer coating. These thermo-responsive GNR@PEG-b-PNVCL nanoparticles are promising DDS that combine the chemotherapeutic and phototherapeutic functions.

Ohmic heating as a new efficient process for organic synthesis in water

A new and efficient process for organic synthesis in aqueous media based on a direct ohmic heating reactor is described. Four representative organic transformations, a Diels–Alder cycloaddition, a nucleophilic substitution, an N-alkylation and a Suzuki cross-coupling reaction, were performed using this process. The results, when compared with those obtained under conventional external heating (oil bath) and microwave heating, showed that ohmic reactor allows faster and more uniform heating and an induced increase of dynamics/mobility of charged species leading in several cases to higher reaction yields and shorter reaction times.

Mechanism of synthesis of metallic oxide powder from aqueous metallic nitrate solution by microwave denitration method

The process for synthesizing metallic oxide powders by the microwave denitration method was investigated using hexahydrated nickel nitrate and trihydrated copper nitrate aqueous solutions, and the electrical field and the temperature distributions in the reactor were numerically simulated. Although CuO powder can be obtained from a trihydrated copper nitrate aqueous solution by the microwave denitration method, a hexahydrated nickel nitrate aqueous solution cannot be heated up to over 270°C by microwave irradiation. It was also found that the reaction routes for microwave heating are the same as those for conventional external heating. This finding indicates that the success of producing oxide particles by microwave denitration depends not only on the microwave absorptivity of the intermediate and the metallic oxide, but also on the temperature difference between the completion of the conversion to the intermediate and the beginning of the significant conversion to metallic oxide. Furthermore, the simulation results suggest that the reactor has a radially inhomogeneous temperature distribution with the highest temperature at the center, which causes the denitration reaction to produce CuO powder to progress concentrically from the center of the reactor.

Static Formation and Dissociation of Methane+Methylcyclohexane Hydrate for Gas Hydrate Production and Regasification

AbstractThe formation and decomposition of methane+methylcyclohexane (MCH) hydrate in a static batch reactor, which was also designed as a high‐pressure microwave reactor, were investigated. The addition of 300 ppm sodium dodecyl sulfate (SDS) provides continuous formation of CH4+MCH hydrate under static conditions. Increasing the initial pressure within the narrow range of 2.7 to 4.6 MPa at 274 K enhances the formation rate by even several times. The gas storage capacity can be largely improved with partial coexisting of sI CH4 hydrate. Unlike a stirred formation, an increase of nonaqueous MCH inhibits the static formation of sH hydrate. The following regasification by 2.45 GHz microwave heating indicates that the dissociation is rate‐controlled by the parallel connection of efficient internal heating and conventional external heating. The multiphase convection characterized by osmotic dehydration and driven by intensified regasification is considered as the dominant mechanism affecting the quiescent dissociation.

Deplasticization and dechlorination of flexible polyvinyl chloride in NaOH solution by microwave heating

This study investigated the deplasticization and dechlorination of flexible polyvinyl chloride (PVC) containing 59.2% PVC, 29.7% dioctyl phthalate (DOP), and approximately 12% stabilizers. Flexible PVC was treated with NaOH solutions at concentrations in the range 2–16 mol/l and heated by microwaves to temperatures between 100° and 250°C for 0–120 min. DOP was extracted from flexible PVC into the NaOH solution as a phthalic acid salt; the remaining PVC was subsequently dechlorinated by increasing the temperature. On internal heating using microwaves, the plasticizer was 100% extracted during processing at 150°C for 30 min, whereas the chlorides were 100% removed during processing at 235°C for 30 min; the residue was converted into hydrocarbon compounds. The maximum weight loss ratio was 71% compared to the pretreatment state. It was also found that 100% deplasticization and dechlorination was possible using 8 mol/l NaOH solution, which is almost half the concentration employed when using conventional external heating systems.

Effects of Microwave Irradiation on Water-soluble Polysaccharides of the Fruiting Body of Hericium erinaceum

To examine the applicability of microwave irradiation for the extraction of polysaccharides in the fruiting body of Hericium erinaceum, structures of polysaccharides obtained by microwave irradiation in water were compared to those obtained by hot water extraction using conventional external heating. A major polysaccharide obtained by microwave irradiation in water (140°C, 5 min) was (1→3;1→6)-β-D-glucan rich in (1→3) linkages, whereas polysaccharides obtained by hot water extraction using conventional external heating (100°C, 6 h) were fucogalactan and (1→3;1→6)-β-D-glucan rich in (1→6) linkages. In the case of microwave irradiation in water, fucogalactan was suggested to be depolymerized during heating. Microwave heating in water has an advantage over the conventional external heating for extraction of β-glucan rich in (1→3) linkages from the fruiting body of H. erinaceum.

Optimization of Microwave-assisted Extraction of Polysaccharides from the Fruiting Body of Mushrooms

Microwave irradiation in the presence of water was applied for extraction of polysaccharides from the fruiting body of Hericium erinaceum, a mushroom called Yamabushitake. In this study, the effects of microwave irradiation temperature and time on solubilization of polymers in H. erinaceum were investigated. The results indicated that the degree of solubilization of polymers proceeded with an increase in heating temperature up to 200°C, although the polymers solubilized gradually depolymerized with the increase in heating temperature. The results also suggested that lengthening irradiation time had effects on solubilization of polymers similar to the increase in heating temperature. Comparison of the results obtained by microwave-assisted extraction with those obtained by extraction using conventional external heating indicated that extractability of the former extraction for 5 min at 140°C was almost equivalent to that of the latter extraction for 6 h at 100°C. This result suggests that microwave irradiation has an advantage for extraction of polysaccharides from the fruiting body of mushrooms in terms of extraction time.

Environmental remediation by an integrated microwave/UV illumination technique. 8. Fate of carboxylic acids, aldehydes, alkoxycarbonyl and phenolic substrates in a microwave radiation field in the presence of TiO2 particles under UV irradiation.

Thermal and nonthermal effects originating when a system is subjected to a microwave radiation field in the TiO2-photocatalyzed transformation of model substances containing various functional groups (e.g., benzoic acid, phthalic acid, o-formylbenzoic acid, phthalaldehyde, succinic acid, dimethyl phthalate, diethyl phthalate, and phenol) have been examined under simultaneous irradiation by ultraviolet (UV) and microwave (MW) radiations. Characteristics of the microwave effects and the fate of each substrate during the microwave-assisted photocatalytic process were monitored by UV absorption spectroscopy, HPLC methods, total organic carbon assays, and identification of intermediates using electrospray mass spectral techniques. Microwave thermal and nonthermal effects were delineated by comparing results from MW-generated internal heat versus conventional external heating, and at constant ambient temperature under a microwave field. Factors involved in the nonthermal component of the microwave radiation were inferred for the initial adsorption of the substrate and its subsequent degradation occurring on the surface of TiO2 particles. Microwave effects bear on the mechanism through which a model substrate undergoes oxidative degradation. A characteristic feature of these effects was briefly examined by considering the behavior of polar (dipole moments) substrates in a microwave radiation field.

OS08W0211 A Study on the mechanical properties of silicon nitride ceramics sintered by 28 GHz millimeter-wave heating method

We study the application of the millimeter wave heating method to the silicon nitride, which includes Ytterbium oxide (Yb_2O_3) and alumina (Al_2O_3) as additives. Millimeter wave heating method has capability in enhancing densification of sintered bodies. As a result, we successfully obtained high-density sintered bodies with 5-wt% Yb_2O_3 and 3-wt% Al_2O_3. The sintering temperature was 1650℃, which was 200℃ lower compared with the conventional external heating method. Moreover, the annealing at 1220℃ with millimeter wave heating method after the sintering was proved to be effective. The sintered bodies showed excellent mechanical properties at room and high temperatures. The Vickers hardness was 7.5 GPa at 1400℃ in a vacuum, 17.4 GPa at room temperature in the air, and fracture toughness K_<IC> was 9.3 MPa m^<1/2> at room temperature in the air. These experimental results showed that the application of the millimeter wave heating method to the silicon nitride is very effective.