Heating Technology Research Articles

Microwave-assisted transforming of biosolids into engineered activated carbon employed for adsorption from wastewater

Biosolids, a prevalent by-product of wastewater treatment plants, contribute ∼350,000 tonnes annually to dry waste solids in Australia. Biosolids are valuable resources due to their high concentrations of carbon and other components. In line with Circular Economy principles, this study explores the potential conversion of biosolids into value-added products, specifically focusing on the feasibility of producing microstructure-engineered powdered activated carbon (AC) for wastewater treatment. Carbonization of biosolids using microwave (MW)-assisted heating technology, compared to traditional heating, presented reduced energy consumption (by 26%) and 38% higher surface area while attaining a similar carbonization yield. After the activation step, MW technology led to a 16% enhancement in surface area, achieving 1507 ± 60 m2/g. Subsequent diluted acid washing effectively reduced the ash content from 58 ± 2.3 to 14.4 ± 1.2 wt%. Then, the microstructure of the AC was tailored to adsorb methylene blue (MB, as a model molecule) and humic acid (HA, as a complex natural organic matter). Microstructure modifications attained an optimal blend of micro- and mesopores for adsorption. One of the ACs was assessed for methylene blue (MB) adsorption, demonstrating a remarkable adsorption capacity of 759 ± 46 mg/g, surpassing a commercial standard sample by 41.5%. The second AC displayed an adsorption capacity of 126.6 ± 5.1 g/mg of HA, a 22% improvement over the commercial sample with an adsorption capacity of 103.5 ± 4.1 mg/g. Kinetics analysis of both adsorption tests was conducted, and they fit well with the pseudo-second-order model. This study underscores upcycling wastewater biosolids using MW-assisted technology into sustainable ACs for the adsorption of different wastewater pollutants, exemplifying a path towards a circular economy and a more environmentally conscious and resource-efficient future.

Ohmic baking of gluten free sponge cake: Analysis of technological and quality characteristics

The demand of gluten-free bakery products is worldwide increasing. Simultaneously, ohmic heating is an alternative heating technology that still deserves further research and development. Therefore, the aim of this work was assessing different technological and quality characteristics of gluten free sponge cake baked by ohmic heating. A custom ohmic system was designed and built and different electric field strengths (1500, 2000 and 2500 V/m) were tested. Conventional baking was performed for comparison purposes. The conventional baking time was 24 min, whilst the ohmic heating time ranged from 3.51 min at 2500 V/m to 7.93 min at 1500 V/m. The ohmic system achieved significantly higher energy efficiencies, reaching nearly 60%, compared to only 4.1% for conventional baking. Additionally, specific energy consumption was significantly lower for ohmic heating. Weight loss was higher for ohmically processed samples, showing larger number of pores in their inner spongy structure. Ohmic heating resulted in a larger volume expansion and a cake with lower density. The remaining quality characteristics, such as color, hardness, cohesiveness, and elasticity, were not significantly different. Results demonstrated that ohmic heating is a suitable technology for baking gluten-free sponge cakes and that it is a promising technology for fast industrial baking of such products.

Ageism, welfare, and the energy transition: a comparative analysis of the perceptions among the elderly in Poland and Norway

BackgroundOne of the potential dimensions on which exclusion and injustice may occur in energy transitions is age. Age-based patterns of exclusion—ageism—has recently been conceptualized in the context of decarbonization as energy ageism. This paper offers a comparative empirical analysis of the senior citizens’ outlook towards an imminent energy transition as well as the impact of energy poverty in two European countries: Norway and Poland.ResultsDrawing on interviews and focus groups with Polish and Norwegian seniors, we present the differences and similarities between the two countries, and the determinants of energy ageism, as well as the concept’s overall applicability and empirical usefulness. We find that socioeconomic conditions outweigh ageism, that is, the resilience of senior citizens in dealing with energy poverty during a transition is conditioned by their material standing and welfare state robustness rather than age based. An important factor is household heating technology, combined with economic vulnerability can push some individuals into energy poverty, while others using alternative sources of heat can navigate through energy crises unscathed.ConclusionsWe note the importance of mainstreaming social inclusion considerations in energy policy and of targeted digital competence building which can enhance senior citizen integration in the energy transition. Lower levels of digital competences among senior citizens certainly play a role and need to be addressed with education programs to increase participation. In both countries, household heating is a major issue and heating sources are strong predictors of energy poverty and regulatory measures and subsidies should be designed at national, regional, and municipal level to assist vulnerable groups in this area.

Technology of flame‑induction heating of ferrous metal shavings in hot briquetting installations

As a result of the study of flame‑induction heating of steel and cast iron shavings, optimal heating modes, dimensions of the furnace and the ratio of the sizes of its components (gas‑flame and induction heaters) were established, which served as the basis for the development of a new heating technology, which ensures minimization of dimensions in comparison with known analogues, increasing the productivity and efficiency of the furnace. It has been established that at the stage of evaporation and removal of water vapor and light oil fractions from the chips in the temperature range of 100–550 °C until the optimal oil concentration of 1.5–3.0 % is achieved, among all known methods of muffle heating, gas‑flame heating is the most economical and productive heating, and subsequently, when heating a dehydrated porous mass of metal with a density of 1100–1700 kg/m3 to 850 °C – induction heating in an atmosphere of products of thermal sublimation and destruction of coolant. It is advisable to carry out induction heating with a current frequency of 2.0–2.4 kHz with a ratio of the lengths of the gas‑flame and induction heating zones of 2.0–2.5 and the dimensions of the inductor (height to hole diameter) of 3.7–4.0. The degree of oxidation of hot‑pressed briquettes corresponds to the initial oxygen content in the chips: for steel – 1.3–1.7 %, for cast iron – 0.46–0.47 %. The data obtained made it possible to develop a technology for flame‑induction heating of ferrous metal shavings, as well as the design of a small‑sized furnace with a specific productivity of 6500–9500 kg/m2·h and an efficiency of 40–45 %.

Dielectric gene engineering on biochar for ultrawide-band microwave absorption with a rational double-layer design

Biomass char is very promising in developing microwave absorbing materials with low minimum reflection loss (RLmin) and ultrawide effective absorption bandwidth (EAB) owing to its low cost and natural availability of various pores, but however is facing a dilemma between the conduction loss and interface polarization loss where new heating technology is highly desirable. In this work, a microwave confined plasma/microwave hybrid heating technology is developed based on the unique interaction between porous carbon and microwave for simultaneous enhancement of conduction loss and interface polarization loss of cellulose char. Compared to the conventional heating product at the same temperature, the as-prepared microwave char showed almost doubled conductivity which is beneficial for conduction loss, higher content of C–O bond that has longer bond length and dielectric susceptibility than CO bond, and more condensed carbon nanoparticles embedded in the carbon matrix which is responsible for increasing the heterointerface polarization loss. As such the tangent loss of MW900-40 % ranges from 0.69 to 0.97 while that of CH900-40 % only ranges from 0.34 to 0.64 in the frequency range of 2.0–18.0 GHz. Further, based on multilayer impedance gradient principle, a double-layer absorber is constructed with products of different MW900 loading, yielding a RLmin of −59.0 dB at 15.9 GHz with an EAB of 10.0 GHz at 4.0 mm, whose working mechanism is comprehensively studied by simulations in terms of impedance matching and microwave dissipation distribution.

Research status of laser powder bed fusion Al–Li alloys and its improvement measures

Laser powder bed fusion (LPBF) Al–Li alloy technology demonstrates adaptability to the development requirements of structural complexity and functional integration, making it a promising area of research in additive manufacturing for the aerospace, defense industry, and other fields. However, challenges such as microstructure anisotropy and metallurgical defects inevitably arise during the LPBF process of lightweight alloys, significantly impeding further enhancements in their formability properties. Some improvement measures offer a viable solution to enhance the microstructure, mitigate metallurgical defects, and optimize residual stress distribution in additive structures, thereby enabling high–performance Al–Li alloy production by LPBF. This paper first introduces the fundamental principle of LPBF and discusses the process of parameter optimization for LPBF Al–Li alloys. It then describes the typical microstructures and common metallurgical defects of LPBF Al–Li alloys, along with examining the evolution process of microstructures and formation mechanism of metallurgical defects. Specifically, it focuses on discussing the influence of Li element on solidification structure. On this basis, it presents the mechanical properties and anisotropy of mechanical properties for LPBF Al–Li alloys. Afterward, a comprehensive review is provided of the current research status regarding LPBF improvement measures, including powder alloying, heat treatment, and other technologies. Emphasis is placed on improvements in microstructure anisotropy and reductions in metallurgical defects through these improvement measures. Finally, this article summarizes the research progress made in LPBF Al–Li alloys and its improvement measures while also prospecting future research work.

Inactivation of Bacillus cereus spores by ohmic heating: Efficiency and changes of spore biological properties

Bacillus cereus spores pose a significant concern during food processing due to their high resistance to environmental stress. Ohmic heating (OH) is an emerging and alternative heating technology with potential for inactivating such spores. This study evaluated the inactivation effects and the biological property changes of Bacillus cereus spores during OH treatments. OH effectively inactivated spores in milk, orange juice, broth, rice soup, and buffer solution in less time than oil bath heating (OB). A decrease in NaCl content improved spore inactivation at the same temperature. Spores were more sensitive to acid at 80–85 °C with OH treatment. Furthermore, OH at 10 V/cm and 50 Hz could reduce the spore resistance and inhibit an increase in spore hydrophobicity and spore aggregation. Both heating methods resulted in significant dipicolinic acid (DPA) leakage and damage to the cortex and inner membranes of the spores. However, OH at 10 V/cm and 50 Hz had the lowest DPA leakage and inflicted the least damage to the inner membrane. The damage to the spore's inner membrane was considered the primary reason for inactivation by OB and OH treatments. Still, OH at 10 V/cm and 50 Hz might also block the germination or outgrowth of treated spores or cause damage to the spore core.

Regulation Mechanism and Optimization Strategy of Microbial Metabolism in Bioreactor

In this study, the metabolic regulation mechanism of microorganisms in bioreactor was discussed, and a series of optimization strategies were proposed based on this. The key effects of metabolic regulation on the performance of bioreactors were revealed through the overview of microbial metabolic pathways and the analysis of regulatory mechanisms. In view of this, the optimization strategy based on metabolic regulation was proposed from the aspects of metabolic engineering transformation, genetic engineering technology application, metabolic pathway reconstruction and optimization. At the same time, the operating conditions of the reactor, such as temperature, pH value, dissolved oxygen, substrate concentration and mixing effect were optimized in detail. In terms of reactor design and scale-up strategy, the scale effect, reactor configuration and flow field optimization, and heat and mass transfer enhancement technology were mainly considered. This study provides important theoretical and practical guidance for the improvement of bioreactor performance and the progress of biotechnology industry.

Enhancing coffee sensory quality: unleashing synergistic effects of selected microorganism starter cultures and ohmic heating technology

Abstract The sensory characteristics of coffee play a pivotal role in determining its consumer appeal and global market potential. The flavor quality of coffee is influenced by a range of factors, including genetic attributes, geographic variables, agricultural practices, and post-harvest processes. Among these, the post-harvest phase, which includes fermentation, stands out as a critical determinant of coffee quality. Notably, controlled wet fermentation techniques and the introduction of specialized starter cultures have demonstrated a significant capacity to enhance the flavor and unique sensory profiles of coffee, capturing the interest of consumers. Utilizing yeast cultures, such as Saccharomyces cerevisiae and Torulaspora delbrueckii, alongside lactic acid bacteria like Lactobacillus sp., has been scientifically substantiated as a means to elevate coffee quality. The application of ohmic heating technology during the coffee fermentation process presents an innovative approach to maintaining the fermentation process at the desired temperature. When synergistically applied in tandem with carefully selected microorganism starter cultures, this approach holds the promise of delivering a substantial enhancement in coffee quality.

Study on temperature field in the process of induction heat treatment with current assisted weld double side method

At present, in the process of weld induction heat treatment, the common method is to carry out centralized induction heating in the weld area, which will lead to large radial temperature difference of the weld, poor controllability of temperature distribution and easy to cause the defects of residual stress concentration in the weld area. To solve the above problems, this paper adopts the two-sided method to conduct induction heating on both sides of the weld, and at the same time, the auxiliary pulse current is passed into the weld to improve the quality of the weld. ANSYS finite element software is used to establish a multi-field coupling prediction model of electric-magnetic-thermal structure, and explore the distribution law of the auxiliary pulse current and the temperature field of the weld. Finally, an experimental study of pulsed current assisted two-sided induction heating is carried out. Temperature test and metallographic test were carried out respectively to verify the effectiveness of pulsed current assisted induction heating technology.

Study on a high-performance heat-driven thermoacoustic heat pump

Heat-driven thermoacoustic heat pump (HDTAHP) is a promising heating technology with high reliability. Current HDTAHP face the challenge of being relatively inefficient and not capable of further improvement. This study aims to address this problem by introducing an innovative energy matching tube (EMT) into the conventional thermoacoustic heat pump to realize more reasonable acoustic power matching between the engine and heat pump units, further greatly improve the system efficiency. The key reason for the limited performance of HDTAHP is first explored and lies in the constraints that exist between temperatures. Through Sage modeling and calculations, the comparison between the proposed system and the conventional thermoacoustic heat pump system verifies that the introduced EMT can dramatically increase the system performance. At a heating temperature of 700 K, the overall Coefficient of Performance (COPh) of the system is improved by 43.7 % compared to the conventional thermoacoustic heat pump without EMT. The performance under different working temperatures is then investigated and demonstrated a strong adaptability of the proposed system under different heating temperature objectives. The comparison with existing thermoacoustic-Stirling heat pumps further indicate the high-performance improvement by EMT and promising potential of thermoacoustic heat pumps in domestic heating domain.

Catalytic infrared radiation dry-peeling Technology for non-Frozen and Frozen Grapes: Effects on temperature, peeling performance, and quality attributes

This study introduces catalytic infrared radiation (CIR) heating technology as an eco-friendly alternative to conventional grape lye peeling (LP). The effects of heating time and distance on non-frozen and frozen grapes were assessed for temperature, peeling performance, and quality attributes. The findings indicate that CIR heating achieves complete dry-peeling of grapes. Extended heating times and reduced distances improve peeling performance, with more favorable results observed in frozen grapes compared to non-frozen ones. Grapes peeled using CIR demonstrated enhanced hardness, color, sugar-acid ratio, bioactive compounds, and antioxidant capacity, compared to those peeled using LP. Importantly, the frozen samples preserved their quality after CIR dry-peeling treatment. Based on peeling performance and quality attributes, the optimum heating times are established at 160 s for non-frozen grapes and 50 s for frozen grapes, at a heating distance of 5 cm. Therefore, CIR dry-peeling is recommended as an eco-friendly and quality-enhancing sustainable grape processing technology.

Local non-similar solutions for EMHD nanofluid flow with radiation and variable heat flux along slandering stretching sheet

Nanofluids are the next-generation energy-transfer substrate due to their exceptional thermodynamic properties. The study of heat transfer on stretched surfaces is important due to its applications in industry, manufacturing, and medicine. The flow across a nonlinear stretched surface with different thicknesses is examined in this study to analyze the impacts of magnetic and electrical field, joule heating, viscous dissipation, and thermal radiation by considering Cu/water as nanofluid. To explore the physical characteristics, initially the mathematical model of the problem is evaluated and cataloged all of its features. Basic flow equations and fundamental rules were used to formulate the considered problem. The flow-controlling “partial differential equations” (PDEs) are transformed into a set of non-dimensional ordinary differential equations” (ODEs) via appropriate non-similar transformations. By utilizing the local non-similarity procedure operating bvp4c, the mathematical model is reconstructed. Physical representations of temperature as well as velocity profiles show how various emerging parameters interact with the flow. It is perceived that when the strength of the magnetic field grows, the velocity of nanoparticles decreases. However, as the electric field’s strength progresses and the velocity distribution does as well, the temperature profile for the nanomaterials rises. The radiation factor enhances the temperature field. The presence of time- and space-dependent characteristics for radiation, heat production increases as the fluid temperature rises. The authors investigate the procedure for replicating the dimensionless non-similar framework adopting the local non-similarity procedure. As per the author’s observations, there is currently no comparable study available in the literature for the flow model under consideration. This research holds significant potential for researchers engaged in the exploration of industrial applications of nanofluids, particularly within geophysical and geothermic domains, solar water heating technologies, biomedical applications, and other interdisciplinary fields.

Finding the gaps in design strategies and technological advancements for net-zero energy buildings development in India

The climate-adaptive net-zero energy building design is an effective trend for achieving a carbon-neutral environment and reducing global energy demand, especially, in India where building energy consumption recorded substantial growth in the past decade. This review article focuses on the development of net-zero energy buildings in tropical climates through the analysis of 44 real case studies. This study investigates the building envelope parameters, advance technologies, and their effectiveness on the building energy models. In the first phase of this study, fourteen net-zero energy buildings or high-performance buildings in the USA, China, and India considering energy-efficient design features and their significant effect on energy consumption have been examined. Moreover, the role of building simulation tools in improving energy efficiency is discussed. The second phase investigates the thirty best practices of net-zero energy buildings in tropical climates worldwide based on envelope choices, heating, cooling, and lighting features. Furthermore, this review discusses the evolving definitions, challenges, and inconsistencies in terminologies of net-zero energy building and illustrates India's initiatives towards net-zero development. The objectives of this review study are to highlight the challenges in building material research, advanced lighting, heating, ventilation, and air conditioning technologies, and integration of renewable energy compared to developed nations. Additionally, the gaps that are the barriers to the development of net-zero energy building in India have been identified. The review eventually concludes by providing policy recommendations and suggesting areas for future research to facilitate net-zero energy-building development in India.

Improved performance of a fiber-optic hydrogen sensor based on a controllable optical heating technology.

A novel, to the best of our knowledge, and compact fiber-optic hydrogen sensor based on light intensity demodulation and controllable optical heating technology is proposed and experimentally investigated. This system employs three photodetectors for optic signal transformation. The first PD is used to receive a little fraction of the amplified spontaneous emission (ASE) for calibration, and the second PD is utilized to detect optic signal reflected by a single mode fiber deposited with WO3-Pd2Pt-Pt composite film. The last PD is utilized to receive the optical power reflected by the short fiber Bragg grating (SFBG) with a central wavelength located in a steep wavelength range (the intensity decreases approximately linearly with the increase of the wavelength) of the ASE light source. A 980 nm laser and proportion integration differentiation (PID) controller were employed to ensure the hydrogen sensitive film working at an operating temperature of 60°C. This sensing system can display a quick response time of 0.4 s toward 10,000 ppm hydrogen in air. In addition, the detection limit of 5 ppm in air can be achieved with this sensing system. The stability of this sensor can be greatly enhanced with a controllable optical heating system, which can greatly promote its potential application in various fields.

Numerical analysis of microwave-enhanced oil shale pyrolysis by rotation turntable based on the Arbitrary Lagrangian-Eulerian method

Microwave heating technology has great potential for efficient pyrolysis of oil shale. However, the inhomogeneous heating characteristics of microwave heating can lead to secondary cracking of pyrolysis products, thus reducing the overall oil yield. In order to address this issue, a rotational movement of oil shale under microwave heating has been proposed to obtain a uniform temperature distribution of the oil shale. Then, a new coupled three-dimensional electromagnetic-thermal-chemical-hydraulic model incorporating the Arbitrary Lagrangian-Eulerian (ALE) method was developed to investigate the temperature distribution and pyrolysis characteristics of oil shale under the rotational motion during microwave pyrolysis. The effects of rotational speed, rotational direction, and microwave power on the pyrolysis process of oil shale were explored through this model. The results showed that the introduction of rotational movement effectively addressed the uneven temperature distribution within the oil shale. Compared with the static condition, the rotational condition reduced the secondary reactions of oil products during microwave pyrolysis and increased the oil yield of oil shale to 50.12 %. As the rotation speed increased, the temperature distribution within the oil shale became more uniform, but the total oil yield reached its peak at a moderate speed of 180 s/r. Research on microwave power indicated that rotation increased the maximum usable power and highlighted that reducing the residence time of pyrolysis products within the oil shale was key to increasing oil yield. This study provides a novel approach and numerical simulation method for enhancing the microwave pyrolysis efficiency of oil shale, and the findings of this study are applicable to both the ex-situ and in-situ exploitation of oil shale.

Heat and the planning system: how can local authorities encourage deployment of low and zero-carbon heating?

There is widespread recognition of the need for new homes to feature only low or zero-carbon (LZC) heating. However, residential developers continue to choose conventional high-carbon options such as natural gas boilers over net-zero compatible alternatives. This study explores how UK local authorities (LAs) within the English planning system can encourage residential developers to deploy LZC heating systems within their projects. We adopt an embedded case study design and analyse 30 residential project proposals within two LA areas. Our study examines local planning policies and interactions between developers and LA officers, along with the resultant outcomes, through documentary analysis and expert interviews with local stakeholders. We find that LAs can encourage developers to adopt LZC heating technologies above and beyond what is required nationally. The conditions for this to occur are (1) a planning policy which restricts allowable heating technology options, (2) empowering LA officers to enforce policies, (3) advice and support for developers to consider alternatives, and where necessary, (4) political backing to challenge unwilling developers. Study findings highlight the important role of LAs in creating the conditions for the transition to LZC heating, which show how they can use powers within the planning system to encourage developers to make low carbon choices without the need for direct investment.

Effects on dimensioning of heat supply technologies for district heating under consideration of future developments regarding investment costs and emission factors

Municipalities and energy suppliers are facing the challenge of transforming space heating supply from fossil fuels to energy sources with low greenhouse gas emissions as part of the heating sector transition. Redesigning and planning future heat generation portfolios for district heating networks involves uncertainties such as energy prices, investment costs, district heat sales, and building energy efficiency. This study presents an optimisation model based on multi-objective mixed-integer linear programming to address economic and ecological needs. The model considers economic and emission objectives to find optimal solutions for heat generation unit dimensioning under different growth scenarios and different emission factors for district heat demands. The results show different pareto optimal solutions, providing a range for heat generation unit dimensioning and heat generation over the investigated time horizon. Additionally, the results include commissioning timepoints which are compared within different heat demand growth scenarios.

Preparation and oxygen-evolution-reaction performance of sulphur-doped flower-like NiFe-based composites supported on biomass porous carbon

Hydrogen gas generated through water electrolysis can replace fossil fuels. Thus, developing cost-effective and efficient water-splitting electrocatalysts for oxygen evolution reaction is highly important. Herein, biomass-porous-carbon-supported sulphur-doped flower-like NiFe-based alloy composites are prepared using an in situ impregnation–heat treatment technology. The spherical flower (diameter ≈ 1 μm, petal thickness ≈ 20 nm) main components are Ni0.5Fe0.5 and Fe9Ni9S16. The 800 °C heat-treated catalyst demonstrates outstanding catalytic performance in oxygen evolution reactions. At a current density of 10 mA cm−2 , it exhibits a minimal overpotential of 298.62 mV

Effect of free volume and hydrophilicity on dehumidification performance of 6FDA-Based polyimide membranes

6FDA-based polyimide air-dehumidification membrane has been considered as one of the most advanced technologies for the energy-saving heating, ventilation, and air-conditioning systems due to their excellent solubility and processing. Nevertheless, there are few reports about the effect of free volume and hydrophilic groups on dehumidification performance. Herein, we propose to tune the free volume and hydrophilicity of 6FDA-based polyimides by tuning the hydrophilicity/hydrophobicity of diamines and/or introducing of hydrophilic carboxylic acid groups, and thus to develop a system that would support high H2O/N2 separation performance for dehumidification and retain excellent mechanical properties. It is found that 6FDA/mPDA membrane shows much higher H2O/N2 separation performance (i.e., H2O permeability 12480 Barrer and H2O/N2 separation factor of 13867) than that of the 6FDA/TFDB and 6FDA/DAM membranes even though its lower FFV. It is suggested that the FFV had a negligible effect on the H2O/N2 separation performance. Although the introduction of highly hydrophilic –COOH groups could significantly increase the H2O/N2 separation performance of hydrophobic 6FDA/TFMB and 6FDA/DAM membranes, the performance is still lower than that of 6FDA/mPDA membrane with similar hydrophilicity. In addition, we found that more –COOH groups to polymers can lead to the possible formation of hydrophilic/hydrophobic separation in membrane which will result in the rapid water vapor condensation and thus unstable air-dehumidification. Thus, the excessive hydrophilicity of 6FDA/mPDA-DABA showed a decreased H2O/N2 separation performance compared with 6FDA/mPDA membrane. These results indicated that the excellent H2O/N2 separation performance mainly depends on reasonable hydrophilicity of polyimide membrane without excessive hydrophilic groups and high FFV.