Extended Heating Time Research Articles

Characterization of an Induction Heating System Used as Solar Simulator

This report delves into the thermal behaviour of solar receiver tubes under induction heating, a key component in concentrated solar power (CSP) technology. Experimental investigations were conducted to understand the temperature distribution and challenges associated with induction heating. A stainless-steel tube was heated using an inductor and subjected to airflow. Initial tests revealed temperature deviations caused by the electromagnetic field and thermocouple interference. Adjustments were made in subsequent trials, including thermocouple repositioning, extended heating times, and consistent camera calibration. Additional experiments explored the effects of inserting iron plates in between the tube and the inductor coil. Results showcased varying temperature profiles for different configurations. In all the cases analysed, there is penetration of the magnetic field within the thickness of the tube walls, simplified as volumetric heat generation. Overall, these findings enhance our comprehension of induction heating dynamics to test CSP components in a small-laboratory scale that would potentially offer insights for system optimization.

Sodium salicylate as a green fluorescent probe for ultrasensitive determination of vonoprazan fumarate via fluorescence switch off strategy; greenness assessment

A green, simple and sensitive spectrofluorometric approach for determining vonoprazan fumarate in bulk and pharmaceutical dosage form by turning off the fluorescence of sodium salicylate is developed. The addition of vonoprazan fumarate reduced linearly the fluorescence intensity of 0.4 mM sodium salicylate at λem 408 nm and at λex 330 nm. The approach was found to be linear in the 50.0–3000.0 ng/mL range. The limits of detection and quantification were 10.97 and 33.23 ng/mL, respectively. The presented method proved its suitability in determination of vonoprazan fumarate in its pure and pharmaceutical dosage form. This method employs water as the exclusive solvent and utilizes safe reagents, evaluated using the Analytical Eco Scale, Green Analytical Procedure Index (GAPI), and carbon footprint. In contrast, previous methods relied on toxic reagents and required extended heating times, resulting in higher environmental impact. The novel method not only enhances analytical efficiency but also aligns with green chemistry principles, offering a sustainable solution for routine pharmaceutical analysis.

Improved Design and Fabrication of a Compression Moulding Machine with Performance Evaluation

This study explores the advancements in the design and performance of an improved compression moulding machine aimed at efficiently recycling various plastic wastes, with an emphasis on Polyethylene Terephthalate (PET). With global plastic waste accumulation posing severe environmental challenges, enhancing recycling technologies is imperative. The re-designed machine was tested at operating temperatures of 200°C, 250°C, and 300°C, highlighting the critical role of temperature and processing duration in determining product quality. Theoretical heating times were found to be shorter than actual times due to real-world inefficiencies such as heat loss and thermal conductivity variations. Weight loss during heating, attributed to the evaporation of volatile components and thermal degradation, was observed. The formation of air pores in samples with extended heating times underscored the necessity for precise process control. The PET melting process initiated effectively at approximately 250°C. The improved machine demonstrated significant potential in enhancing recycling efficiency and versatility.

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.

Effects of the use of raw or cooked chickpeas and the sausage cooking time on the quality of a lamb-meat, olive-oil emulsion-type sausage

Reformulation of cooked sausages using high-protein plant-based food such as chickpea as meat extenders and vegetable oils to replace animal fat can be a suitable approach to promote the consumption of smaller portions of meat. The pre-processing of chickpea and the sausage cooking intensity can potentially affect the quality of reformulated sausages. In this study, an emulsion-type sausage made with lamb meat, chickpea and olive oil was prepared in triplicate following three different formulations containing the same targeted levels of protein (8.9%), lipids (21.5%), and starch (2.9%): control sausage (CON; control, without chickpea), and raw (RCP) and cooked chickpea (CCP) sausages (both with 7% chickpea). Sausages were cooked at 85 °C for two heating times (40 min or 80 min) and were analysed for weight loss, emulsion stability, colour, texture, lipid oxidation and volatile composition. Compared to CON sausages, the use of raw chickpea reduced the elasticity and significantly increased lipid oxidation during the sausage-making process resulting in major changes in the volatile composition. The use of previously cooked chickpea, however, resulted in the sausages having greater cooking loss, hardness and chewiness than CON sausages, while there was no difference in lipid oxidation, and differences in volatile compounds were scarce. The reformulation with cooked chickpea could provide a sausage with more similarity to the CON sausage. The extended heating time of 80 min at 85 °C did not significantly affect the quality traits in either CON or reformulated sausages except for a higher cooking loss.

Transforming micropores to mesopores by heat cycling KOH activated petcoke for improved kinetics of adsorption of naphthenic acids

Formation of activated carbon from petroleum coke by KOH, results in high specific surface area materials that are predominantly microporous. This initial microporosity means that the adsorption kinetics of target species are not as rapid as they could be, thus limiting environmental remediation applications for the material. To address this problem a series of additional heat cycles with no additional chemical inputs were applied after activation but prior to the removal of activating agents. This process resulted in the oxidation of residual potassium metal from the initial activation which allows it to function again as an activating agent for the subsequent cycles. The heat cycling resulted in an increase in mesoporosity by 10–25% with each successive cycle independent of the KOH to feedstock ratio. This was shown to be demonstrably different than equivalently extended heating times, thus identifying the importance of thermal cycling. Adsorption kinetics of three model naphthenic acids showed faster kinetics for the pore widened activated carbon. The t1/2 times dropped from 20 to 6.6 min for diphenyl acetic acid, 34.3 to 4.5 min for cyclohexane acetic acid, and 51.4 to 12.0 min for heptanoic acid.

Experimental performance of a small solar system for adsorption cooling in summer and heating in winter

Solar energy is a kind of renewable energy with abundant resources and enormous reserves. Meanwhile, adsorption cooling technology can utilize natural refrigerants, thus also making this technology environmentally friendly. If solar energy can be effectively collected and utilized for heating in winter, then the environmental pollution caused by electricity and fossil energy consumption can be reduced. More importantly, considering engineering, the same solar device could provide cooling in the summer and heating in the winter. This study used parabolic trough and glass–metal vacuum heat collectors to conduct solar adsorption cooling and solar air heating experiments in summer and winter, respectively, to facilitate the complete and appropriate use of solar energy. Experimental results of solar adsorption cooling with silica gel as the adsorbent revealed that the coefficient of performance of the system reached 0.329. In addition, the influences of air flow rates and heat storage medium on the performance of the solar air heating system were investigated. Results revealed that the average and instantaneous efficiencies of the system considerably increased with the heat storage medium (i.e., water) filling in the annular cavity of the evacuated tube. The extended heating time also markedly increased by up to 170 min and was therefore of considerable practical value.

Effect of a Novel Microwave-Assisted Induction Heating (MAIH) Technology on the Quality of Prepackaged Asian Hard Clam (Meretrix lusoria).

The microwave-assisted induction heating (MAIH) method—an emerging thermal technique—was studied to heat the prepackaged raw hard clam (Meretrix lusoria). The cooking effects on microbial and physiochemical qualities of clam were investigated. After the heating of the clam meat samples, the aerobic plate count (APC), psychrotrophic bacteria count (PBC), and total volatile basic nitrogen (TVBN) levels decreased with increasing heating time, but the shucking ratio, area shrinkage, and texture (hardness, cohesiveness, and chewiness) increased. In addition, the L* (lightness) and W (whiteness) of the clam meat samples increased significantly at the beginning of the heating period, whereas they decreased significantly with extended heating time. However, a* (redness) had the opposite trend. This study found that when clams were heated for more than 120 s at 130 °C or 150 s at 90 °C, they displayed obvious shrinking and a yellow-brown appearance, indicating that they are overcooked. After heating by MAIH for at least 110 s at 130 °C or 130 s at 90 °C, the samples were cooked well and gains a completely shucking, along with no microbial count detected. Therefore, the results indicated that the optimum heating conditions for prepackaged hard clams subjected to an MAIH machine were 130 °C for 110 s or 90 °C for 130 s.

Influence of pH, Temperature and Protease Inhibitors on Kinetics and Mechanism of Thermally Induced Aggregation of Potato Proteins.

Understanding aggregation in food protein systems is essential to control processes ranging from the stabilization of colloidal dispersions to the formation of macroscopic gels. Patatin rich potato protein isolates (PPI) have promising techno-functionality as alternatives to established proteins from egg white or milk. In this work, the influence of pH and temperature on the kinetics of PPI denaturation and aggregation was investigated as an option for targeted functionalization. At a slightly acidic pH, rates of denaturation and aggregation of the globular patatin in PPI were fast. These aggregates were shown to possess a low amount of disulfide bonds and a high amount of exposed hydrophobic amino acids (S0). Gradually increasing the pH slowed down the rate of denaturation and aggregation and alkaline pH levels led to an increased formation of disulfide bonds within these aggregates, whereas S0 was reduced. Aggregation below denaturation temperature (Td) favored aggregation driven by disulfide bridge formation. Aggregation above Td led to fast unfolding, and initial aggregation was less determined by disulfide bridge formation. Inter-molecular disulfide formation occurred during extended heating times. Blocking different protein interactions revealed that the formation of disulfide bond linked aggregation is preceded by the formation of non-covalent bonds. Overall, the results help to control the kinetics, morphology, and interactions of potato protein aggregation for potential applications in food systems.

Deterioration mechanism of concrete under long-term elevated temperature in a metallurgic environment: A case study of the Baosteel company

A long-term elevated temperature environment is typically found in the metallurgy industry, which has adverse effects on the properties and microstructure of concrete structures. A few studies investigated the effect of short-time high temperature on the properties and microstructure of concrete, but the effect of long-term elevated temperature is seldom analysed. In this study, the deterioration mechanism of concrete under long-term elevated temperature was investigated by determining the thermal stresses on basis of finite element model (FEM) and analyzing the changes in its chemical composition and microstructure through X-ray diffraction (XRD), pore structure analysis (PSA) and scanning electron microscope (SEM). The results indicated that the maximum temperature stress of surface concrete could exceed 4 MPa, which was close to the ultimate tensile strength of normal concrete. The results also showed that calcium hydroxide (CH) could decompose at less than 200 ℃ because of the crystallization of tiny CH crystals, doping with other ions, extended heating time, and xonotlite (α-C2SH), which was formed on the internal surface of the concrete and decomposed on its external surface. Owing to these reasons, cracks and holes were generated, resulting in severe deterioration of the concrete structure.

Formation of Maillard reaction products in bread crust-like model system made of different whole cereal flours

Free and protein-bound Maillard reaction products (acrylamide, 5-hydroxymethylfurfural, α-dicarbonyl compounds, N-e-fructosyllysine, N-e-carboxymethyllysine and N-e-carboxyethyllysine) and the reaction precursors (sugars and amino acids) were investigated in bread crust-like systems prepared with different cereal flours. Selected cereals were; whole and refined wheat, whole einkorn, whole rye, whole oat and whole corn. For all cereals, the concentrations of reducing sugars, free amino acids and protein-bound lysine increased significantly after dough fermentation (p < 0.05). Heating the bread crust-like model systems at 200 °C for different time periods (5, 15, 30 min) caused significant decrease in the concentration of sugars and amino acids (p < 0.05). Among α-dicarbonyl compounds, 3-deoxyglucosone and methylglyoxal were found in high amounts. However, extended heating time caused significant reduction in their concentrations (p < 0.05). Compared to 5 min of heating, higher amounts of 5-hydroxymethylfurfural formation were observed in samples heated for 15 and 30 min. However, prolonging the heating time resulted in a reduction in the amount of acrylamide formed in bread crust-like samples prepared with einkorn and oats. Heating for 5 min caused formation of early and advanced glycation products in bread crust-like samples prepared from all cereals. The amounts of early and advanced glycation products in the high molecular weight fractions of bread crust-like systems were significantly higher than those in bread-crust-like systems, but they decreased rapidly in samples heated for longer time (p < 0.05).

Microwave Heating Induces Oxidative Degradation of Extra Virgin Olive Oil

Heating vegetable oil in a microwave oven can lead to the formation of reactive free radicals, which are responsible for causing lipid oxidation. The thermo-oxidative stability of olive oil has previously been studied under microwave heating for short processing periods that simulate typical cooking times. This study compares the effect of the oxidative degradation of extra virgin olive oil (EVOO) during extended heating times under different microwave powers (150 and 500 W) or conventional heating. The results showed that intense microwave heating of EVOO significantly increased the free acidity and specific extinction coefficients (K270), and resulted in more severe loss of phenolic compounds, compared with conventional heating. Microwave treatment also resulted in higher amounts of acrolein in EVOO after a short processing period compared with conventional heating. These results demonstrate that intene microwave heating has a more severe effect on EVOO compared with conventional heating.

Determining aromatic and aliphatic carboxylic acids in biomass-derived oil samples using 2,4-dinitrophenylhydrazine and liquid chromatography-electrospray injection-mass spectrometry/mass spectrometry

Converting biomass to a useful fuel commonly incorporates the pyrolysis of the biomass feed stock. The base liquid fraction usually contains high concentrations of ketones, aldehydes and carboxylic acids, of which each can cause detrimental issues related to the storage and upgrading process. Knowing the carbonyl species and the concentration of each will provide value information to the pyrolysis researchers, specifically as that community branches into more targeted end-products such as jet fuel or biogenic-derived oxygenate-containing fuel products. The analysis of aldehydes, ketones and small alkyl carboxylic acids using 2,4-dinitrophenylhydrazine (DNPH) derivation method has been well documented and the method is commonly used the analytical community. By using liquid chromatograph coupled to tandem mass spectrometry, biomass sample analysis can be complete with identification of most carbonyl species. The issue of identifying isobaric ketone and aldehyde compounds can be resolved by utilizing differences in retention time or characteristic fragment ions of ketones and aldehydes. One issue which could not resolved using published methods was identifying aromatic or large non-aromatic carboxylic acids from their corresponding hydroxyl aldehyde or ketone analogs. By modifying the current method for determining carbonyls in biomass samples, carboxylic and hydroxyl-carbonyl can be determined. A careful adjustment of the pH during the extraction procedure and extended heating time of the DNPH solution allowed for the successful derivation of aromatic carboxylic acids. Like other dinitrophenylhydrazones, carboxylic acid derivatives also produce a unique secondary ion pattern, which was useful to distinguish these species from the non-acid analogs.

The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO

In this study, the temperature dependence of Cr(VI) formation and reduction in the presence of CaO was examined during the thermal treatment of sludge that contains chromium. thermogravimetry–differential scanning calorimetry and X-ray diffractometry were used to characterize the thermal behavior and phase transformation, respectively. Na2CO3 leaching procedure was employed to determine the amount of Cr(VI). The result showed that CaO promoted Cr(III) oxidation, however, its influence is very dependent on heating temperature, with the extent of the effect varying with temperature. From 200–400°C, the presence of CaO facilitated formation of intermediate product Cr2O3+x containing Cr(VI) during dehydration of chromium hydrate, while Cr2O3+x would decompose as temperature over 400°C, accompanied by part of Cr(VI) being reduced to Cr(III). From 500 to 900°C, Cr(III) reacted with CaO to form a leachable CaCrO4 product. This product was stable and a prolonged heating time did not reduce the amount of Cr(VI) significantly. At 1000–1200°C, part of CaCrO4 was reduced to Ca(CrO2)2 in 1h. While extended heating time above 1h resulted in the Ca(CrO2)2 being oxidized reversibly to CaCrO4 at 1200°C. Since CaCrO4 is thermodynamically less stable over 1000°C, MgO could induce CaCrO4 to be reduced into MgCr2O4 at around 900°C, lower than that for the reduction from CaCrO4 into Ca(CrO2)2. It suggested that adding MgO might be a potential approach for inhibiting Cr(VI) formation during heating sludge containing chromium.

Dipentaerythritol: a novel additive for the precipitation of dispersed Ni particles in polyols

Highly dispersed uniform Ni particles ranging in size from 0.1 to 1.2 μm were synthesized by reducing nickel carbonate in polyols in the presence of dipentaerythritol (DPE) and noble metal salts. DPE was essential in preventing the aggregation of nickel particles, while the noble metal (‘seeding’ approach) effectively tailored their size. Ferromagnetic particles with a cubic closed packed (ccp) crystal habit were obtained using short reduction times at temperatures below 200 °C. Non-magnetic particles with hexagonal closed packed (hcp) structure were obtained after extended heating times (>16 hours) at temperatures above 220 °C. The temperature of the reduction and heat-treatment process was adjusted by using polyols with different boiling points.

Thermal/Optical Methods for Elemental Carbon Quantification in Soils and Urban Dusts: Equivalence of Different Analysis Protocols

Quantifying elemental carbon (EC) content in geological samples is challenging due to interferences of crustal, salt, and organic material. Thermal/optical analysis, combined with acid pretreatment, represents a feasible approach. However, the consistency of various thermal/optical analysis protocols for this type of samples has never been examined. In this study, urban street dust and soil samples from Baoji, China were pretreated with acids and analyzed with four thermal/optical protocols to investigate how analytical conditions and optical correction affect EC measurement. The EC values measured with reflectance correction (ECR) were found always higher and less sensitive to temperature program than the EC values measured with transmittance correction (ECT). A high-temperature method with extended heating times (STN120) showed the highest ECT/ECR ratio (0.86) while a low-temperature protocol (IMPROVE-550), with heating time adjusted for sample loading, showed the lowest (0.53). STN ECT was higher than IMPROVE ECT, in contrast to results from aerosol samples. A higher peak inert-mode temperature and extended heating times can elevate ECT/ECR ratios for pretreated geological samples by promoting pyrolyzed organic carbon (PyOC) removal over EC under trace levels of oxygen. Considering that PyOC within filter increases ECR while decreases ECT from the actual EC levels, simultaneous ECR and ECT measurements would constrain the range of EC loading and provide information on method performance. Further testing with standard reference materials of common environmental matrices supports the findings. Char and soot fractions of EC can be further separated using the IMPROVE protocol. The char/soot ratio was lower in street dusts (2.2 on average) than in soils (5.2 on average), most likely reflecting motor vehicle emissions. The soot concentrations agreed with EC from CTO-375, a pure thermal method.

Kinetic Pathway of Palladium Nanoparticle Sulfidation Process at High Temperatures

A significant issue related to Palladium (Pd) based catalysts is that sulfur-containing species, such as alkanethiols, can form a PdSx underlayer on nanoparticle surface and subsequently poison the catalysts. Understanding the exact reaction pathway, the degree of sulfidation, the chemical stoichiometry, and the temperature dependence of this process is critically important. Combining energy-filtered transmission electron microscopy (EFTEM), X-ray diffraction (XRD), and X-ray absorption spectroscopy experiments at the S K-, Pd K-, and L2,3-edges, we show the kinetic pathway of Pd nanoparticle sulfidation process with the addition of excess amount of octadecanethiol at different temperatures, up to 250 °C. We demonstrate that the initial polycrystalline Pd-oleylamine nanoparticles gradually become amorphous PdSx nanoparticles, with the sulfur atomic concentration eventually saturating at Pd/S = 66:34 at 200 °C. This final chemical stoichiometry of the sulfurized nanoparticles closely matches that of the crystalline P16S7 phase (30.4% S), albeit being structurally amorphous. Sulfur diffusion into the nanoparticle depends strongly on the temperature. At 90 °C, sulfidation remains limited at the surface of nanoparticles even with extended heating time; whereas at higher temperatures beyond 125 °C, sulfidation occurs rapidly in the interior of the particles, far beyond what can be described as a core-shell model. This indicates sulfur diffusion from the surface to the interior of the particle is subject to a diffusion barrier and likely first go through the grain boundaries of the nanoparticle.

Beef, chicken and lamb fatty acid analysis — a simplified direct bimethylation procedure using freeze-dried material

When fractionation of meat lipids is not required, procedures such as saponification can be used to extract total fatty acids, reducing reliance on toxic organic compounds. However, saponification of muscle fatty acids is laborious, and requires extended heating times, and a second methylation step to convert the extracted fatty acids to fatty acid methyl esters prior to gas chromatography. Therefore the development of a more rapid direct methylation procedure would be of merit. The use of freeze-dried material for analysis is common and allows for greater homogenisation of the sample. The present study investigated the potential of using freeze-dried muscle samples and a direct bimethylation to analyse total fatty acids of meat (beef, chicken and lamb) in comparison with a saponification procedure followed by bimethylation. Both methods compared favourably for all major fatty acids measured. There was a minor difference in relation to the C18:1 trans 10 isomer with a greater (P<0.05) recovery with saponification. However, numerically the difference was small and likely as a result of approaching the limits of isomer identification by single column gas chromatography. Differences (P<0.001) between species were found for all fatty acids measured with no interaction effects. The described technique offers a simplified, quick and reliable alternative to saponification to analyse total fatty acids from muscle samples.

Effects of thermal processing and various chemical substances on formaldehyde and dimethylamine formation in squid Dosidicus gigas

Trimethylamine oxide (TMAO) in squid is demethylated to dimethylamine (DMA) and formaldehyde (FA) during storage and processing. This study examined the effects of thermal processing and various chemical substances on FA and DMA formation in squid. The thermal conversion of TMAO was assessed by analysing four squid and four gadoid fish species, which revealed that FA, DMA and trimethylamine (TMA) were gradually produced in squid, whereas TMA increased and FA decreased in gadoid fish. A significant increase in both FA and DMA levels was observed in the supernatant of jumbo squid with increased heating temperature and extended heating time at pH 6-7. Ferrous chloride combined with cysteine and/or ascorbate had a significantly positive effect on FA formation in the heated supernatant of jumbo squid. No significant difference was observed in the levels of Cu and Fe in squid and gadoid fish. The capability of Fe(2+) to promote the formation of FA and DMA was not completely attributable to its reducing power in squid. Non-enzymatic decomposition of TMAO was a key pathway during the thermal processing of jumbo squid, and Fe(2+) was a crucial activator in the formation of FA and DMA.

Antioxidant activity of polyphenol and anthocyanin extracts from fruits of Kadsura coccinea (Lem.) A.C. Smith

Abstract Polyphenols and anthocyanins were extracted from Kadsura coccinea fruit. The contents of total phenolics and anthocyanins, influences of pH and temperature on anthocyanins, and antioxidant activities of extracts were further analyzed. The results showed that the total phenolic content of peel extracts was superior to that of pulp extracts. The total anthocyanin content of peel extracts was 180 ± 2.91 mg/100 g of fresh peel tissues. K. coccinea anthocyanins were stable below pH 4, whilst high temperature and extended heating time induced their degradation. Metal-chelating capacity (MCC) assay indicated that no ortho-dihydroxy aromatic moiety existed in the B-ring of the anthocyanin molecules, but there might be a catechol group in the B-ring of the polyphenol molecules. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and reducing power of extracts decreased in the following order: peel polyphenol extracts > anthocyanin extracts > pulp polyphenol extracts. It would be worthwhile to introduce this rare fruit into more countries.