Efficient Heating Method Research Articles

Efficient conversion of ethanol to acetaldehyde with induction heating at low temperature

The application of induction heating (IH) to provide heat for chemical reactions has received great attention due to its potential to electrify chemical reactions. Biomass-based production of acetaldehyde from ethanol has gained rising interest since it provides an alternative sustainable method instead of the fossil-fuel-based output using acetylene and formaldehyde in the presence of a catalyst. The dehydrogenation of ethanol can be catalyzed by supported copper catalysts. The reaction is typically carried out at high temperatures, around 250–300 °C, without oxygen. The resulting product mixture usually contains acetaldehyde, as well as other byproducts such as ethylene and hydrogen gas. The acetaldehyde can be separated from the other components using distillation or other separation techniques. In this work, we studied the catalyst activity with IH for the first time and achieved high ethanol conversion and acetaldehyde selectivity at a temperature of 30 ˚C lower than that with conventional furnace heating (CFH). A transport model was applied to design the catalyst bed configuration and improve the catalyst activity, stability, and energy efficiency by minimizing the temperature gradient. Our work suggests that the temperature distribution and the fast compensation of heat loss through IH are critical for the catalyst behavior. Both high production efficiency and energy efficiency can be achieved with IH, such that it can be an efficient and environment-friendly heating method for the chemical industry.

Standing wave-moving and sample-rotating effect of microwave heating on ceramic in a single-model cavity

This study designs a metal surface movable-microwave heating cavity with a turntable to choose an efficient and uniform microwave heating method according to the shape of the ceramic. The movement of the metal surface affects the standing wave in the cavity, causing the electric field in the cavity to change constantly during heating due to the rotating turntable and metal surface motion. This results in the absorption mode of ceramic is not constant. However, it is challenging to mesh the dynamic position of ceramic; therefore, this study proposes a transform optics method to simulate the rotating motion of the turntable and the moving motion of the metal surface. Experiments verify the correctness of the simulation model. The heating effects of fixed heating, turntable rotating and metal surface moving are compared. Finally, the effects of microwave heating on ceramics at different speeds and moving rates are discussed.

Droplet Formation and Energy Input during Induction Wire Melting with Pulsed and Constant Generator Power

Induction heating is a fast, reproducible, and efficient heating method used in various manufacturing processes. However, there is no established additive manufacturing (AM) process based on induction heating using wire as feedstock. This study investigates a novel approach to AM based on inductive heating, where a steel wire is melted and droplets are detached periodically using a two-winding induction coil. The process parameters and energy input into the droplets are characterized. The induction generator exhibits a sluggish response to the excitation voltage, resulting in a lag in the coil current. The process is captured using a high-speed camera, revealing a regular droplet formation of 14 Hz and uniform shapes and sizes between 2.11 and 2.65 mm in diameter when operated within an appropriate process window. Larger drops and increased spatter formation occur outside this window. The proposed method allows for the production of droplets with almost spherical shapes. Further analysis and characterization of droplet formation and energy input provide insights into process optimization and indicate an overall efficiency of approximately 10%.

High pressure turbine rotor blades heating duration experimental estimates prior to the bypass turbofan engine start for reducing thermal stresses

Reducing the durability cost of an aircraft product is an issue either addressed at the design stage or causing significant design modifications. Turbine preheating of a gas turbine engine (GTE) allows for the thermal stress of the rotor blades (RB) to be reduced at the engine start without making design changes, but only by implementing the engine heating technology into the operational process. Values of thermal stresses on rotor blades of a high-pressure turbine of a bypass turbofan engine (TFE) with and without heating allow us to determine the change in the total HPT RB damage rate. In the concept of preheating a GTE prior to the start in order to comply with the preheating technology, it is necessary to know the duration within which the RB will heat up to the required temperature. Thus, the research objective, presented in the paper, is to empirically determine the HPT RB heating time, using thermocouples and pyrometers on a full-scale body depending on the methods of air supply for heating and rotor spinning. A distinctive feature of this work is the application of the empirical approach to determine HPT RB heating time to evaluate the feasibility of the GTE preheating technology application prior to the start and the selection of the most efficient heating method according to the duration criterion. Several methods of engine heating prior to the start, using different sets of equipment and the method of supplying hot air to the turbine, were considered. The results of RB heating time measurements made it possible to establish the method of heating with minimal time expenditure prior to the engine start.

A new efficiency figure of merit for induction heating appliances operating under highly variable operating conditions

Induction heating is an efficient and high-performance heating method which already has a significant market penetration and economic impact due to its benefits inherent to contactless energy transfer systems such as quickness, cleanness, and safety. Efficiency is a key design parameter since it determines not only the appliance performance but also its environmental impact, with significant socio-political implications. However, it is not easy to determine and compare the actual power converter efficiency operating under highly variable conditions typical of IH. This paper proposes an averaged efficiency parameter elaborated based on technical and typical IH usage conditions that offers a useful value to compare power converters operating under realistic operation conditions. The proposed parameter has been evaluated in some of the most significant power converter topologies used in reported state-of-the-art induction heating systems.

Study on temperature field distribution state of carbon fiber reinforced polymer wound circular tube via electromagnetic induction heating

The variation of temperature fields during the winding process of CFRP (Carbon Fiber Reinforced Polymer) due to fiber winding is a key factor influencing its curing and shaping. Traditional heating methods result in energy wastage and environmental pollution during the heating process. Electromagnetic induction technology, as a non-contact, pollution-free, and efficient heating method, is playing an increasingly significant role in the process of heating and curing CFRP. This study focuses on two heating methods, internal and external, for CFRP wound circular tubes. It establishes finite element analysis models for induction heating with different coil structures. The heating mechanisms of different coil-induced CFRP wound circular tube models are explained, and the effects of external arc-shaped coils and external/internal annular coils on the temperature field distribution of CFRP wound circular tubes are investigated. By comparing simulations with experiments, the correctness of the numerical analysis model in this study is demonstrated. It offers viable heating methods for different conditions in industrial production, providing theoretical support and empirical data for the induction heating of CFRP wound circular tubes.

Microwave-assisted Synthesis of Bioactive Six-membered O-heterocycles

Abstract: Microwave radiation has been utilised since the late 1970s as an alternative thermal energy source for chemical reactions. Initially used in inorganic chemistry, its potential for organic chemistry was revealed in 1986. Convertion of electromagnetic energy into heat, with frequencies ranging from 0.3-300 GHz using microwave irradi-ation, is an efficient heating method. The microwave heating method has significant potential for industrial processes, reducing reaction times and enhancing yields and se-lectivity. It finds applications in peptide and organic synthesis, materials science, pol-ymer chemistry, biochemical processes, and nanotechnology. Microwave-assisted or-ganic synthesis is environmentally friendly and beneficial for producing bioactive het-erocyclic compounds. Oxygen-containing heterocycles are abundant and possess vari-ous biological functions, making them essential for developing new drugs. Microwave technology facilitates the synthesis of these compounds, including bioactive six-mem-bered o-heterocycles such as pyrones, oxazolones, furanones, oxetanes, oxazoli-dinones, and dioxetanes. By utilizing modern organic transformations, microwave-as-sisted chemistry enhances the efficiency of synthetic processes, leading to the discovery of more beneficial molecules. The review provides an up-to-date analysis of the syn-thesis and medicinal properties of O-heterocycles, emphasizing the strengths and needs of this field. It guides researchers, facilitating microwave-assisted green synthesis re-actions and offering a flexible platform for forming bioactive heterocyclic rings.

Microwave-Assisted Synthesis of Biologically Relevant Six-Membered N-Heterocycles

Abstract: One of the most efficient non-conventional heating methods is microwave irradiation. In organic synthesis, microwave irradiation has become a popular heating technique as it enhances product yields and purities, reduces reaction time from hours to minutes, and decreases unwanted side reactions. Microwave-assisted organic synthesis utilizes dielectric volumetric heating as an alternative activation method, which results in rapid and more selective transformations because of the uniform heat distribution. Heterocyclic compounds have a profound role in the drug discov-ery and development process along with their applications as agrochemicals, fungicides, herbi-cides, etc., making them the most prevalent form of biologically relevant molecules. Hence, enor-mous efforts have been made to flourish green routes for their high-yielding synthesis under mi-crowave irradiation as a sustainable tool. Among the different clinical applications, heterocyclic compounds have received considerable attention as anti-cancer agents. Heterocyclic moieties have always been core parts of the development of anti-cancer drugs, including market-selling drugs, i.e., 5-fluorouracil, doxorubicin, methotrexate, daunorubicin, etc., and natural alkaloids, such as vinblastine and vincristine. In this review, we focus on the developments in the microwave-assisted synthesis of heterocycles and the anti-cancer activities of particular heterocycles.

Microwave-assisted Synthesis of Heterocycles and their Anti-cancer Activities

Abstract: One of the most efficient non-conventional heating methods is microwave irradiation. In organic synthesis, microwave irradiation has become a popular heating technique as it enhances product yields and purities, reduces reaction time from hours to minutes, and decreases unwanted side reactions. Microwave-assisted organic synthesis utilizes dielectric volumetric heating as an alternative activation method, which results in rapid and more selective transformations because of the uniform heat distribution. Heterocyclic compounds have a profound role in the drug discovery and development process along with their applications as agrochemicals, fungicides, herbicides, etc., making them the most prevalent form of biologically relevant molecules. Hence, enormous efforts have been made to flourish green routes for their high-yielding synthesis under microwave irradiation as a sustainable tool. Among the different clinical applications, heterocyclic compounds have received considerable attention as anti-cancer agents. Heterocyclic moieties have always been core parts of the development of anti-cancer drugs, including market-selling drugs, i.e., 5-fluoroura-cil, doxorubicin, methotrexate, daunorubicin, etc., and natural alkaloids, such as vinblastine and vincristine. In this review, we focus on the developments in the microwave-assisted synthesis of heterocycles and the anti-cancer activities of particular heterocycles.

A Novel and Efficient Collagen Extraction Method Assisted by Microwave Irradiation

A new and efficient microwave heating method was developed to extract intact Type I collagen from bovine limed splits. Orthogonal experiment was conducted to optimize the parameters of extraction, and the extraction yield was measured by ultraviolet spectra (UV). The hierarchical structures of the obtained collagen were determined by amino acid analysis, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), UV, Fourier transform infrared spectra (FT-IR), circular dichroism spectra (CD), fluorescence spectra (FL) and ultra-sensitive differential scanning calorimetry (US-DSC). The results indicated the optimal conditions for this microwave assisted extraction were 37°C for 7 h by using solid to liquid ratio of 1:45. The resultant yield of collagen was 14.35% under the optimal conditions, which is 1.5 times higher than that obtained by the control water bath-heating method. Amino acid analysis, UV and SDS-PAGE revealed that the primary structure of collagen extracted with microwave assistance was type I collagen. Although the extraction yield was promoted drastically with microwave assisting, the secondary structure of the collagen involving triple helix still maintained according to FT-IR, CD, FL and VP-DSC results. In brief, microwave irradiation could be a new routine for collagen extraction with advantages of fast and effective. Moreover, this study might offer a potential choice for utilizing hide or skin limed split wastes.

Microwave-Assisted Synthesis of Room Temperature Long Persistent Luminescent Materials and Their Imaging Applications

In this study, we utilized a simple and efficient microwave heating method with polyethyleneimine (PEI) and phosphate as raw materials to synthesize room temperature persistent luminescence (RTPL) materials that emit phosphorescent light for up to 10 s. Our investigation revealed that the optimal synthesis conditions were a microwave radiation power of 560 W and a heating time of 5 min. The synthesized RTPL materials had an average particle size of 2 nm and exhibited excellent RTPL performance, with optimal excitation and emission wavelengths of 360 nm and 544 nm, respectively. Additionally, these materials displayed good water solubility. We conducted mapping experiments and in situ phosphorescent imaging of plants to showcase the potential applications of RTPL materials in the fields of biological imaging and anti-counterfeiting. Overall, our findings demonstrate the promising potential of these RTPL materials as versatile tools for various practical applications.

マイクロ波特異効果はあるのか？ 有機合成反応における実験的検証

Highly polar compounds are generally heated by absorbing microwave energy. Since 1986, microwave irradiation has been applied to various organic syntheses as an efficient heating method. On the other hand, an additional effect called “microwave specific effect”, that cannot be explained by the simple heating effect, has been observed. In a solvent that absorbs less microwave, microwave energy can be directly provided to the reaction substrate, and microwave-specific effects can be expected. Some microwave-assisted asymmetric synthetic reactions have been observed to accelerate while maintaining enantioselectivity. Based on this working hypothesis, we experimentally confirmed the microwave-specific effect in several organic synthetic reactions.

Development and Optimization of 3D-Printed Flexible Electronic Coatings: A New Generation of Smart Heating Fabrics for Automobile Applications.

Textile-based Joule heaters in combination with multifunctional materials, fabrication tactics, and optimized designs have changed the paradigm of futuristic intelligent clothing systems, particularly in the automobile field. In the design of heating systems integrated into a car seat, conductive coatings via 3D printing are expected to have further benefits over conventional rigid electrical elements such as a tailored shape and increased comfort, feasibility, stretchability, and compactness. In this regard, we report on a novel heating technique for car seat fabrics based on the use of smart conductive coatings. For easier processes and integration, an extrusion 3D printer is employed to achieve multilayered thin films coated on the surface of the fabric substrate. The developed heater device consists of two principal copper electrodes (so-called power buses) and three identical heating resistors made of carbon composites. Connections between the copper power bus and the carbon resistors are made by means of sub-divide the electrodes, which is critical for electrical-thermal coupling. Finite element models (FEM) are developed to predict the heating behavior of the tested substrates under different designs. It is pointed out that the most optimized design solves important drawbacks of the initial design in terms of temperature regularity and overheating. Full characterizations of the electrical and thermal properties, together with morphological analyses via SEM images, are conducted on different coated samples, making it possible to identify the relevant physical parameters of the materials as well as confirm the printing quality. It is discovered through a combination of FEM and experimental evaluations that the printed coating patterns have a crucial impact on the energy conversion and heating performance. Our first prototype, thanks to many design optimizations, entirely meets the specifications required by the automobile industry. Accordingly, multifunctional materials together with printing technology could offer an efficient heating method for the smart textile industry with significantly improved comfort for both the designer and user.

Experimental investigations on thermo-stamping of carbon fiber reinforced polyamide 6 hat-shaped components with self-resistance electrical heating: Influence on microscopic and macroscopic properties from temperature related processing parameters

Thermo-stamping is a widely used forming process for automotive components made from fiber reinforced thermoplastic composites, but it still suffers from a variety of challenges such as long cycle time and high energy consumption. In this paper, self-resistance electrical (SRE) heating, an internal efficient heating method with the advantages of rapid heating speed and low energy consumption, was introduced into thermo-stamping for the rapid manufacturing of carbon fiber reinforced polyamide 6 (CFR-PA6) hat-shaped components. The impacts of the temperature related process parameters, preheating temperature (90 °C ∼ 220 °C) and mold temperature (20 °C ∼ 130 °C) on the shape accuracy, surface quality, microscopic morphology and mechanical properties of obtained hat-shaped components were investigated through experimental characterization. Besides, the energy-saving effect of SRE heating was also revealed compared with radiant heating, an external heating method. It is found that the defects such as fiber bundle cracks, matrix cracks and interface cracks caused by SRE heating are more serious than those caused by radiant heating, which is attributed to the effect of Joule heating, Lorentz force and dielectric breakdown. However, a high mold temperature can reduce these defects owing to the reconsolidation behavior of the hat-shaped component during the thermo-stamping process. The results show that the hat-shaped components possess a good formability and forming quality at a preheating temperature at 200 °C and mold temperature at 130 °C. Moreover, the total cycle time of thermo-stamping with SRE heating is less than 1 min and the energy consumption by SRE heating is about 9.86 % ∼12.09 % compared with radiant heating, which provides a more energy-efficient option for industrial production.

Ultra‐fast, low‐cost, and green regeneration of graphite anode using flash joule heating method

AbstractGraphite is the state‐of‐the‐art anode material for most commercial lithium‐ion batteries. Currently, graphite in the spent batteries is generally directly burned, which caused not only CO2 emission but also a waste of precious carbon resources. In this study, we regenerate graphite in lithium‐ion batteries at the end of life with excellent electrochemical properties using the fast, efficient, and green Flash Joule Heating method (FJH). Through our own developed equipment, under constant pressure and air atmosphere, graphite is rapidly regenerated in 0.1 s without pollutants emission. We perform a detailed analysis of graphite material before and after recovery by multiple means of characterization and find that the regenerated graphite displays electrochemical properties nearly the same as new graphite. FJH provides a large current for defect repair and crystal structure reconstruction in graphite, as well as allowing the SEI coating to be removed during ultra‐fast annealing. The electric field guide the conductive agent and binder pyrolysis products to form conductive sheet graphene and curly graphene covering the graphite surface, making the recycled graphite even better than new commercial graphite in terms of electrical conductivity. Regenerated graphite has excellent multiplier performance and cycle performance (350 mAh g−1 at 1 C with a capacity retention of 99% after 500 cycles). At cost, we get recycled graphite that displays the same performance as new graphite, costing just 77 CNY per ton. This FJH method is not only universal for the regeneration of spent graphite generated by various devices but also enables multiple use‐failure‐regeneration steps of graphite, showing great potential for commercial applications.image

Scalable Synthesis of High Entropy Alloy Nanoparticles by Microwave Heating

High entropy alloy nanoparticles (HEA-NPs) are reported to have superior performance in catalysis, energy storage, and conversion due to the broad range of elements that can be incorporated in these materials, enabling tunable activity, excellent thermal and chemical stability, and a synergistic catalytic effect. However, scaling the manufacturing of HEA-NPs with uniform particle size and homogeneous elemental distribution efficiently is still a challenge due to the required critical synthetic conditions where high temperature is typically involved. In this work, we demonstrate an efficient and scalable microwave heating method using carbon-based materials as substrates to fabricate HEA-NPs with uniform particle size. Due to the abundant functional group defects that can absorb microwave efficiently, reduced graphene oxide is employed as a model substrate to produce an average temperature reaching as high as ∼1850 K within seconds. As a proof-of-concept, we utilize this rapid, high-temperature heating process to synthesize PtPdFeCoNi HEA-NPs, which exhibit an average particle size of ∼12 nm and uniform elemental mixing resulting from decomposition nearly at the same time and liquid metal solidification without diffusion. Various carbon-based materials can also be employed as substrates, including one-dimensional carbon nanofibers and three-dimensional carbonized wood, which can achieve temperatures of >1400 K. This facile and efficient microwave heating method is also compatible with the roll-to-roll process, providing a feasible route for scalable HEA-NPs manufacturing.

Research on the mechanism of magnetic flux concentrator in the gap-to-gap induction heating of wind power gear

Gear quality is one of the factors that determine the stability of the wind turbine. Electromagnetic heating is a green and efficient heating method, which has been used to heat wind power gears. Good mechanical properties could be obtained by induction hardening on the surface of wind power gears. And a uniform hardened layer along the tooth profile is needed. In this paper, research on the effect of the Magnetic Flux Concentrator (MFC) in gap-to-gap induction heating of wind power gear was carried out. The study and the experimental tests refer to the heat treatment of an inner gear ring of a wind turbine transmission of modulus m = 16 at frequency 6000 Hz. The calculated hardened depth is 3 mm inward from the side of the tooth profile, and reaches 2 mm at root of the tooth. The mechanism of the concentrator, and the relationship between MFC characteristics and the heating results are explored. The study found the heating time and quality could be significantly affected by the geometrical dimensions thickness "t", height "h" and material of the MFC. The Magnetocaloric Capacity "Mc" was proposed to describe the ability of the MFC to influence the heating process. The characteristics of the magnetic flux concentrator that affect the heating quality and efficiency are discussed. Meanwhile, this study found that the heating efficiency is related to the strength of the magnetic field in the MFC and the distribution of magnetic field lines. By adjusting t, h and the materials, the heating efficiency and quality could be significantly changed. The maximum temperature difference along the tooth contour was changed to 39.6%, and the average temperature was changed to 6%. When the relative permeability of the material is matched with the frequency, a better heating quality and higher speed could be obtained. The research provides a theoretical support for the precise control of the gap-by-gap induction heating of wind power gear, especially for quality control by the MFC.

Effect of radio frequency-assisted hot-air drying on drying kinetics and quality of Sichuan pepper (Zanthoxylum bungeanum maxim.)

Radio frequency (RF) is an efficient uniformity heating method that can be used for pasteurization. Information on how RF heating influences the physicochemical properties of agricultural product is limited. In this study, the effect of RF heating treatment combined with hot-air (HA) drying (50 °C, 55 °C and 60 °C) on the physicochemical properties of Sichuan pepper was assessed. Sichuan pepper was subjected to RF treatment combined with HA drying, and the performance was compared with HA drying alone (50 °C, 55 °C and 60 °C) in terms of drying kinetics, volatile components, non-volatile components (OH-α-sanshool, polyphenols and flavonoids) and antioxidant activity (ABTS and ferric reducing antioxidant power). RF heating had no negative effects on OH-α-sanshool for the 50 RF-HA group but it could significantly reduce the loss of polyphenols (12.27% at 55 °C, RF-HA group) and flavonoids (15.08% at 60 °C, RF-HA group). Compared with fresh Sichuan pepper, the 50 RF-HA group retained a similar aroma profile. RF heating treatment followed by HA drying is a prospective technique for obtaining high-quality dried Sichuan pepper.

Thermodynamic and economic analysis of the air source heat pump system with direct-condensation radiant heating panel

The air source heat pump (ASHP) system with the direct-condensation radiant heating panel (DRHP) is an efficient space heating method. To evaluate the energy and exergy efficiencies of the system, a thermodynamic model was established. The effects of external air temperature, indoor air temperature and condensation temperature on the system efficiencies were investigated comprehensively. Results indicate that the low compression ratio is beneficial to the improvement of the energy and exergy efficiency of the system. The efficiency superiority of the system is corroborated in comparison with other ASHP systems. Meanwhile, the economic performances of the system are investigated with the initial cost, operating cost and several economic indicators. To examine the operating cost of the system, a reliable system model is proposed and the hourly heating load rates of a case study are presented. Results show that the dynamic investment pay-back period and the internal rate of return of the proposed system are 7.3 years and 11.2%, respectively. The economic competitiveness of the proposed system is demonstrated in comparison with other traditional ASHP heating systems.

Characteristics Analysis of the Heat-to-Power Ratio from the Supply and Demand Sides of Cities in Northern China

Combined heat and power (CHP), an efficient heating method with cascades use of energy, accounts for approximately 50% of the heat sources in northern China. Many researchers have made significant efforts to improve its energy efficiency and environmental effects with important achievements. Given that the system produces heat and electricity at the same time, this study focuses on the role of CHP in the holistic urban energy system and points out the mismatch between the demand and supply sides of urban energy systems by using the heat-to-power ratio as a parameter. The calculation method and characteristics of the supply side heat-to-power ratio of eight heating methods and the maximum demand side heat-to-power ratio for 19 cities in northern China are displayed. After the analysis, it is concluded that (1) the maximum demand side heat-to-power ratio in the cities varies from 1.0 to 5.9, which is affected by the location and social, economic, and industrial structures. (2) In most of the cities, with the current energy structure, the demand side heat-to-power ratios are always larger than the supply side heat-to-power ratios. (3) The reduction in heating demand, surplus heat recovery, and the use of a highly efficient electric heating method, such as the heat pump, can help solve the mismatch of the heat-to-power ratio between the demand and supply sides. These conclusions can guide the urban energy planning and system construction.