Heating Device Research Articles

3D internal crack propagation in brittle solids under non-uniform temperature field: Experimental and numerical simulation

In the field of engineering, elevated temperatures often induce thermal stress. Especially in brittle materials, the propagation of internal cracks under such thermal stress is frequently the primary cause of failure. We utilize the 3D internal laser-engraved crack technology to create internal cracks at various locations inside the half-Brazilian disk specimens. By precisely controlling the power of the heating device, we achieved temperature non-uniformity of the external heat source, resulting in uneven heating of the material’s surface. Simultaneously, by adjusting the geometry of the material and using semi-Brazilian disk specimens, we generated uneven temperature gradients and thermal capacities along different heat conduction paths. The internal cracks at different locations also affect the distribution of thermal stress in the material, further influencing the formation of the non-uniform temperature fields (NUTF). Through the above methods, we successfully conducted physical experiments on the 3D propagation of internal cracks in brittle materials under NUTF. Additionally, we utilized J-integral and the finite element method for thermal analysis to conduct thermo-mechanical coupled 3D numerical simulations. Furthermore, we employed a polarising microscope to analyze the microscopic morphology of 3D internal cracks. Finally, we revealed the mechanism of 3D internal crack propagation under NUTF. The results show that prefabricated internal cracks in group A produce “n-shaped” crack at a height of 15 mm and “u-shaped” cracks at heights of 25 mm and 35 mm. Meanwhile, in group B, the eccentric prefabricated internal cracks ultimately produce “s-shaped” cracks. Through analysis, it was determined that the differential formation occurred due to relative sliding between the upper and lower surfaces of the crack under longitudinal shear stress induced by NUTF. Group A cracks have smooth surfaces, which are mode I-II cracks. group B generated “lance-like” fractures with obvious “anti-binary tree”, which are mixed mode I-II-III cracks. These findings provide an experimental and theoretical basis for the study of 3D internal crack propagation modes under NUTF and deepen the understanding of fracture mechanics in brittle materials.

Modeling and research on high-frequency AC heating system for lithium-ion battery based on bidirectional buck-boost topology

Lithium-ion battery (LIB) performance decreases in cold climates, preheating is necessary to improve the output power and life decay of low-temperature LIB. At present, a variety of internal alternative current (AC) heating methods are used to achieve fast and temperature-consistent heating. However, existing AC heating devices are constrained by the problems of changing the battery structure, and also need for an additional power supply to power the battery, which have effect on the battery life. Meanwhile, the conventional model is not suitable for AC preheating simulation, especially at high frequencies. Under above scenarios, a high-frequency AC heating method using a bidirectional boost converter is designed and a high-frequency thermoelectric model based on lithium-ion transmission is developed. In the paper, the proposed high-frequency AC heating structure and thermal-electrical coupling model are verified by experimental results to test the validity of different AC heating frequencies, which solves the lack of comprehensive theoretical and experimental verification in the field of high-frequency AC heating. The experimental results show that increasing the AC heating frequency at the same current multiplicity can significantly increase the heating rate. An optimal frequency is acquired, the optimal heating rate can reach 4.65 K/min at 800 Hz without affecting the service life of the battery. The high-frequency AC heating method provides a new solution framework for the LIB performance enhancement in cold climates.

On the design of manifolds for parallel channel systems

In the design of high-performance heat and mass transfer devices such as liquid-cooled heat sinks, catalytic reactors, and catalytic convertors, parallel mini/microchannels are favored owing to their special potentials. Offering low pressure drop, providing high transfer surface area to volume ratio, and being easy to manufacture and optimize have been drawing thermal and chemical engineers attention to parallel channels for past decades. When working with parallel channels, the challenge of flow maldistribution is commonly faced which decreases their efficiency significantly. System total pressure drop and flow uniformity are two parameters that determine the system performance. In the present study, a variety of practical ideas, aiming to enhance parallel channels performance, are studied numerically. Inventive manifold designs with high hydraulic performance are created through the course of this study. The results of these designs are compared with basic conventional designs which show substantial enhancement. Analyzing less successful designs lead us to deep understanding of fluid dynamics in parallel channel heat and mass transfer devices.

Interfacial area concentration correlation for boiling steam-water two-phase flows in annulus flow channels

The investigation of boiling two-phase flows in annulus flow channels has garnered increasing significance given its extensive utilization in various heating devices and its crucial contribution as a fundamental basis for comprehending boiling two-phase flow behavior in intricate flow channels, such as rod bundle flow channels. Accurate modeling of Interfacial Area Concentration (IAC) in boiling steam-water two-phase flows is essential for enhancing the predictive performance of the two-fluid model in simulating complex two-phase behaviors in a diverse range of practical boiling systems. The present study evaluates the predictive performance of seven representative IAC correlations using available typical experimental IAC data from boiling steam-water two-phase flows in annulus flow channels. Although some representative IAC correlations exhibit favorable predictive performance for specific experimental databases, none of the reviewed existing correlations consistently maintain acceptable predictive performance across all collected experimental data. In order to enhance the accuracy and reliability of IAC predictions under boiling flow conditions, a novel IAC correlation has been proposed grounded in physical-based considerations to effectively model the IAC contributions of small (group-1) and large (group-2) bubbles in boiling steam-water two-phase flows in annulus flow channels. The newly proposed two-group bubble IAC correlation has been validated through the examination of 303 boiling steam-water data obtained from annulus flow channels, demonstrating satisfactory predictive performance with the mean relative error of 0.216. Moreover, the applicability of the newly proposed IAC correlation to rod bundle flow channels has been evaluated using 53 boiling steam-water data taken from a 3 × 3 rod bundle flow channel, yielding a favorable prediction result with a mean relative error of 0.173. The anticipated improvement in the accuracy of predicting IAC for steam-water two-phase flows through the newly proposed correlation is expected to provide a scientific foundation for enhancing the performance and safety of thermal systems.

Temperature rising and anti-freezing performance of gravel-clay mixed with PCM applying infrared radiation during winter construction

Freeze–thaw cycles could easily cause the structural damage and mechanic performance deterioration of clay. In order to prevent the freeze–thaw cycles problem in the core-wall zone of the high core-wall rock-fill dam in cold regions, gravel-clay mixed with phase change material (GC-PCM) can be used as damming material and present a certain level of anti-freezing performance during winter construction. However, GC-PCM construction work area is still likely to run a risk of freezing under the severe cold and strong wind weather. In order to solve the freezing problem of GC-PCM, this study developed an infrared radiant heating device without interfering with the original construction procedure and conducted an indoor test to investigate the temperature rising performance of GC-PCM after receiving infrared radiation. Also, a numerical simulation method was proposed for the temperature rising and anti-freezing performance of the GC-PCM construction work area and the effects of different factors (including radiant pass, moving speed of infrared device and wind speed) on the anti-freezing performance were analysed subsequently. Main results show that: (1) the effectiveness of proposed numerical simulation method is validated by the indoor test; (2) after receiving 8-pass infrared radiation, the GC-PCM construction work area at 4 % PCM content remains unfrozen in 24 hours under the typical weather in December; and (3) instead of increasing radiant passes, reducing the moving speed of infrared device can better improve the anti-freezing performance of GC-PCM. This study validates the feasibility of applying infrared radiant heating method on GC-PCM, providing a potential technical means for gravel-clay anti-freezing during winter construction.

PCR compatible miniprep DNA isolation in rice using microwave and dry bath based heating devices

PCR compatible miniprep DNA isolation in rice using microwave and dry bath based heating devices

Glass frit and method of forming electrical insulating coatings on steel substrates of film heaters

Electric film heaters (EFHs) applied on flat steel substrates show promising potential in the production of heating devices. The basis for manufacturing EHFs is heat-resistant steel, the surface of which is coated with a heat-resistant electrical insulation coating. These coatings are glass crystalline and are applied mainly by screen printing. Compared to screen printing, the electrophoretic method of coating is more productive. In this work, glass in the MgO–CaO–B2O3–SiO2 oxide system was chosen for obtaining glass crystalline coatings. The paper provides a description of the material composition and the method used to prepare a suspension for еру electrophoretic deposition of coating. The main technological parameters for forming electrophoretic coatings with a specific thickness are determined based on experimental results. Utilizing calculated data on the properties of the selected glass, the study substantiates the most rational temperature and time regime for coating firing. These conditions promote crystallization and result in the production of heat-resistant coatings with sufficient electrical insulating properties for steel substrates of EFHs.

High-Performance Microwave Heating Device for Tubular Loads Using a Quasi-Coaxial Structure

High-Performance Microwave Heating Device for Tubular Loads Using a Quasi-Coaxial Structure

Comparing Warm and Cold Gutta-Percha Techniques for Root Canal Filling: An In Vitro Study

ABSTRACT Background: Gutta-percha is commonly used in endodontic therapy for obturating root canals after cleaning and shaping procedures. Warm and cold gutta-percha techniques are two common methods employed for obturation, each with its own advantages and limitations. Materials and Methods: Twenty extracted human teeth with single-rooted canals were selected and divided into two groups: warm gutta-percha obturation and cold gutta-percha obturation. In the warm gutta-percha group, gutta-percha was heated to a predetermined temperature using a warm gutta-percha heating device and injected into the root canal using a heated carrier. In the cold gutta-percha group, gutta-percha was applied directly to the root canal without prior heating. Root canal obturation quality was assessed using radiographic imaging to evaluate the presence of voids, completeness of obturation, and adaptation to the canal walls. Micro-computed tomography (micro-CT) analysis was also performed to quantify the volume of obturating material and assess the three-dimensional distribution of gutta-percha within the root canal space. Results: Both warm and cold gutta-percha techniques demonstrated effective obturation of root canals, with comparable outcomes in terms of void formation, completeness of obturation, and adaptation to canal walls. However, micro-CT analysis revealed differences in the volume and distribution of gutta-percha within the root canal space. Warm gutta-percha obturation exhibited more uniform distribution of gutta-percha material and higher volumetric filling compared to cold gutta-percha obturation. Additionally, the warm gutta-percha technique demonstrated superior flowability and adaptation to irregularities within the root canal system. Conclusion: In this in vitro study, warm gutta-percha obturation demonstrated advantages over cold gutta-percha obturation in terms of volumetric filling, distribution within the root canal space, and adaptation to canal irregularities.

Measuring Dielectric Properties of MARDI 76 (MRQ76) Rice at the Frequency of 915 MHz and 2.45 GHz

The microwave heating system has been widely used in the food processing and postharvest handling of rice. However, to develop efficient heating energy for the heating and drying process, the knowledge of permittivity or dielectric properties of the MARDI 76 (MRQ76) rice is quite important. The penetration and power dissipation of microwave inside the MARDI 76 (MRQ76) rice is strongly dependent on its dielectric properties or permittivity. Furthermore, characterisation of changes in permittivity or dielectric properties of MARDI 76 rice at elevated temperatures is essential for designing the microwave heating device and system. The permittivity or dielectric properties of MARDI 76 rice (MRQ76) were measured using Agilent open-ended coaxial-line probe and Agilent E5071C Network Analyser. The temperature of the MRQ 76 rice sample was regulated using a WiswCircu Circulator Water bath between temperatures of 27ºC to 70ºC. MARDI MRQ 76 rice sample was placed into the temperature-controlled stainless steel sample holder with water jacket assembly which was designed for permittivity measurement at different temperatures. The effect of temperature on dielectric properties of MARDI 76 rice, power dissipation and penetration depth of microwave radiation at the Industrial, Scientific, and Medical (ISM) heating frequency of 915 MHz and 2.45 GHz was assessed. Results indicated that both dielectric constant and dielectric loss of MARDI 76 rice samples increased with increasing temperature. Power dissipation of microwave radiation inside MARDI 76 rice increases with an increase in temperature. On the other hand, the penetration depth of microwave radiation into the MARDI 76 rice decreased with the increase in temperature. The result of this study shows dielectric properties and heating temperature of MARDI MRQ 76 rice play an important role in designing the microwave heating system for MARDI MRQ 76 rice.

Towards highly homogeneous self-regulating heating of smart nanocomposites

Smart self-regulating heating devices utilising the positive temperature coefficient (PTC) effect have shown great potential in advancing applications across healthcare, soft robotics, and energy-efficient manufacturing. However, achieving homogeneous resistive heating within such temperature self-controllable nanocomposites remains a significant challenge, falling short of meeting the requirements of advanced heating systems. This study explores and evaluates multiple innovative strategies aimed at enhancing the temperature uniformity of PTC nanocomposites. By identifying and analysing the primary physical mechanisms behind the inhomogeneous heating observed in conductive polymer composites, we propose a series of targeted strategies, ranging from customised material formulations to novel electrode configurations. Recycled carbon fibres have also been explored and upcycled as an effective solution for homogenous self-regulating heating. Through a comprehensive analysis of experimental results, the effectiveness of each strategy has been evaluated with a significantly improved temperature uniformity (from 32.6 to 2.7 % variation at 125 °C), providing valuable insights for the design and development of advanced self-regulating heating devices based on conductive polymer nanocomposites, while offering promising prospects for achieving more energy-efficient and uniform heating in various industrial applications.

A novel approach for environmentally benign synthesis and solid-state polymerization of fluorinated polyimides in aqueous co-solvent

This study presents a novel approach that enables an environmentally benign water-based co-solvent synthesis of fluorinated polyimides (FPIs) using conventional fluorine-based monomers such as 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2′-bis(trifluoromethyl)benzidine (TFMB). The high surface tension inherent in fluorine-based materials, which inhibits water solubility, can be overcome by mixing water with an alcohol-based solvent. The surface tension of the co-solvent decreases proportionally with the alcohol content, facilitating synthesis from fluorine-based monomers that were previously inaccessible in water. Oligomeric fluorinated poly(amic acid) salt (FPAAS) can be rapidly synthesized in aqueous solutions containing alcohol, particularly 1-propanol (PrOH). Subsequent coating and thermal treatment processes allow high molecular weight FPI films to be produced by solid-state polymerization. A comprehensive analysis of the resulting FPI films shows excellent physical properties comparable to conventionally synthesized FPI films. The 6FDA-TFMB-based FPI exhibits remarkable thermal stability up to 570 °C (Td,5%), low yellow index of 1.37, high transparency of 92.9 % and tensile strength of 116.5 MPa. The presented synthetic strategy allows the adoption of monomers with different fluorine-based substituents, thus providing insights for future aqueous synthesis. The thermal, mechanical, and optical qualities of FPIs can be utilized to create optically clear heating devices. The transparent heater, fabricated on the FPI film utilizing a laser patterning technique to create electrodes from silver nanowires, was capable of increasing the temperature up to 100 °C under a 9 V voltage application.

Temperature Controller of Infant Incubator using Arduino

The factors affect the child within incubator are mainly the temperature, humidity. The organization of temperatures one of the basic criteria for building a stable environment for the child. This digital temperature controller uses an Arduino board as its primary controller. It can regulate any heating device's temperature within predetermined ranges and shows the device's status, including on and off, as well as its current temperature. A temperature controller is an instrument that regulates temperature, as the name suggests. The temperature controller receives data from a temperature sensor and outputs data to a control element, like a fan or heater. In order to regulate process temperature precisely and with minimal operator intervention, a temperature control system uses a controller that receives input from a temperature sensor (such as a thermocouple, RTD, or DHT22). After comparing the actual temperature to the set-point—the desired control temperature—it outputs the result to a control element.

Experiment on the Excitation of Vapor Behavior and the Vibration by Thermal Flow Under C-Tube Pool Boiling Model

Abstract As an important safety equipment in nuclear system, the passive residual heat removal heat exchanger (PRHR HX) with C-tube is responsible for timely removing heat from the reactor core in accident. A C-tube heating device was setup to investigate the flow characteristics of the in-containment refueling water storage tank (IRWST), which is of the PRHR HX shell-side flow field and the vibration characteristics of the heat exchanger tube. The temperature of the flow field and the acceleration signal of the C-tube were measured. The C-tube frequency in the pool boiling condition is 0–0.660 Hz. There is no resonance with the first natural frequency of 8.98 Hz. The IRWST temperature field can be divided into slow-heating period, fast-heating period, and boiling period. Steam vapor exists in three periods, condensation and collapse of vapor concentrate on horizontal tube. The fast-heating period exists the subcooling degree ΔTsub for the most intense vapor excitation, ΔTsub is in the range of 13–16 °C. In term of thermal flow excitation vibration, the existence of the cross flow with C-plane direction is in the transition period from the slow-heating period to the fast-heating period, which excites the maximum root mean squares (RMS) amplitude 0.039 mm and 0.034 mm at the midpoint of upper horizontal tube and vertical tube. When the fluid enters fast-heating period, the direction of flow changes into the normal C-plane. Normal RMS amplitude reached maximum 0.02 mm at upper 1/4 of the vertical tube in boiling period. The above research provides important data support for the safety and reliability of PRHR HX.

Combustion Efficiency of Various Forms of Solid Biofuels in Terms of Changes in the Method of Fuel Feeding into the Combustion Chamber

This study analyzes the combustion of pellets and briquettes made of plant biomass in low-power heating devices powered periodically with fuel being placed on the grate, as well as after modification using an automatic fuel feeding system in the gutter burner. The use of herbaceous biomass in the form of pellets in low-power heating devices with automatic fuel feeding and combustion in a gutter burner is not widely promoted and popular. Therefore, this study used four types of herbaceous waste biomass (wheat straw, rye straw, oat straw and hay) and one type of woody waste biomass (birch sawdust) for testing. The basic chemical characteristics were determined for the raw materials. After appropriate preparation, the selected starting materials were subjected to briquetting and pelleting processes. Selected physical properties were also determined for the obtained biofuels. Biofuels made from birch sawdust had the lowest heat value (16.34 MJ·kg−1), although biofuels made from wheat, rye and hay straw had a slightly lower calorific value, respectively: 16.29; 16.28 and 16.26 MJ·kg−1. However, the calorific value of oat straw biofuels was only 15.47 MJ kg−1. Moreover, the ash content for herbaceous biomass was 2–4 times higher than for woody biomass. Similar differences between herbaceous and woody biomass were also observed for the nitrogen and sulfur content. To burn the prepared biofuels, a domestic grate-fired biomass boiler was used, periodically fed with portions of fuel in the form of pellets or briquettes (type A tests), which was then modified with a gutter burner enabling the automatic feeding of fuel in the form of pellets (type B tests). During the combustion tests with simultaneous timing, the concentration of CO2, CO, NO and SO2 in the exhaust gases was examined and the temperature of the supplied air and exhaust gases was measured. The stack loss (qA), combustion efficiency index (CEI) and toxicity index (TI) were also calculated. The research shows that the use of automatic fuel feeding stabilizes the combustion process. The combustion process is balanced between herbaceous and woody biomass biofuels. Disparities in CO2, CO and Tgas emissions are decreasing. However, during type B tests, an increase in NO emissions is observed. At the same time, the research conducted indicates that the combustion of herbaceous biomass pellets with their automatic feeding into the combustion chamber is characterized by an increase in combustion efficiency, indicating that when the combustion process is automated, they are a good replacement for wood biofuels—both pellets and briquettes.

Parameterization of Four Models to Estimate Crop Evapotranspiration in a Solar Greenhouse.

Working to simplify mechanistic models on the basis of reliability for estimating crop evapotranspiration (ET) in a greenhouse is still worthwhile for horticulturists. In this study, four ET models (Penman-Monteith, Priestley-Taylor, and Shuttleworth-Wallace models, and the Crop coefficient method) were parameterized after taking the restriction effect of resistance parameters in these models on ET into account, named as PA-PM, PA-PT, PA-CC, and PA-SW, respectively. The performance of these four parameterized models was compared at different growth stages, as well as the entire growing season. Tomatoes that were ET-grown in a solar greenhouse without a heating device were measured using weighting lysimeters during 2016-2017 and 2019-2021, in which data from 2016 were used to adjust the model parameters, and data from the other four study years were used to examine the model performance. The results indicated that the PA-PT and PA-CC models have a better performance in estimating tomato ET at four growth stages, while the PA-PM and PA-SW performed well only at the development and middle stages. Compared to the ET that was measured with the weighting lysimeters, the ET that was predicted using the PA-PM model was 27.0% lower at the initial stage, and 8.7% higher at the late stage; the ET that was computed using the PA-SW model was 19.5% and 13.6% higher at the initial and late stages, respectively. The PA-PT model yielded the lowest root mean square error and the highest index of agreement against the other models over the entire growing season, indicating that the PA-PT model is the best recommended model for estimating tomato ET in a solar greenhouse.

Electrodynamic properties of a rectangular waveguide with a dielectric plate located in the center of its wide wall

A rectangular waveguide with a dielectric plate located in the E-plane is the basic element of devices for microwave heat treatment of sheet materials. In this regard, it is relevant to study the processes of propagation and transformation of electromagnetic waves in such a system. The purpose of the work is to study the influence of the transformation of the electromagnetic field in the air medium of a rectangular waveguide in the zone of propagation of the slow wave H10 on the distribution of electric field energy in the dominant wavelength range and determining the wavelength, at which its maximum value is reached. The range properties of the intrinsic electrodynamic parameters and the field structure of a rectangular waveguide with a dielectric plate located in the E-plane in the middle of its wide wall have been studied. The wavelength at which the maximum energy level of the electric field in the dielectric plate is achieved is determined. The results obtained can be used in the design of microwave heating devices for dielectric materials.

Hydrogen in the Natural Gas Network—Relevance for Existing Fire Precautions

Power-to-gas technology can be used to convert excess power from renewable energies to hydrogen by means of water electrolysis. This hydrogen can serve as “chemical energy storage” and be converted back to electricity or fed into the natural gas grid. In the presented study, a leak in a household pipe in a single-family house with a 13 kW heating device was experimentally investigated. An admixture of up to 40% hydrogen was set up to produce a scenario of burning leakage. Due to the outflow and mixing conditions, a lifted, turbulent diffusion flame was formed. This led to an additional examination point and expanded the aim and novelty of the experimental investigation. In addition to the fire safety experimental simulation of a burning leakage, the resulting complex properties of the flame, namely the lift-off height, flame length, shape and thermal radiation, have also been investigated. The obtained results of this show clearly that, as a consequence of the hydrogen addition, the main properties of the flame, such as lifting height, flame temperature, thermal radiation and total heat flux densities along the flame, have been changed. To supplement the measurements with thermocouples, imaging methods based on the Sobel gradient were used to determine the lifting height and the flame length. In order to analyze the determined values, a probability density function was created.

EOC 76 - Universal Use of Heating Devices in Sink Drainpipes Reduced Clinical bacteremia in a Real-world Intensive Care Unit

EOC 76 - Universal Use of Heating Devices in Sink Drainpipes Reduced Clinical bacteremia in a Real-world Intensive Care Unit

Single-tube, single-strip lateral flow assays utilizing loop-mediated isothermal amplification for simultaneous hepatitis B and C viral detection.

Globally, hepatitis B virus (HBV) affects over 250 million people, whereas hepatitis C virus (HCV) affects approximately 70 million people, posing major public health challenges. Despite the availability of vaccines and treatments, a lack of comprehensive diagnostic coverage has left many cases undiagnosed and untreated. To address the need for sensitive, specific, and accessible diagnostics, this study introduced a multiplex loop-mediated isothermal amplification assay with lateral flow detection for simultaneous HBV and HCV testing. This assay achieved exceptional sensitivity and was capable of detecting HBV and HCV concurrently in a single tube and on a single strip within 25 min, achieving the required clinical sensitivity (10 and 103 genomic copies/reaction for HBV and HCV, respectively). The method was validated in clinical samples of various viral genotypes, achieving an equivalent limit of detection. Additionally, a custom portable heating device was developed for field use. The assay developed here, capable of direct viral detection on the strip, shows promise in supplanting current methods that solely identify antibodies and necessitate additional qPCR for viral activity assessment. This economical and rapid assay aligns with point-of-care testing needs, offering significant advancements in enhancing viral hepatitis diagnostics in settings with limited resources.