Effect Of Heating Conditions Research Articles

The structure and in vitro starch digestibility of wheat starch-glycerol monopalmitin complexes: the effect of heating conditions and water content

The effects of the heating conditions and water content on the structure and digestibility of wheat starch (WS)-glycerol monopalmitin (GMP) complexes were investigated. The results showed that the higher water content and the heating conditions of 90°C for 60 min after 100°C for 10 min favor the formation of more WS-GMP complexes with the greater short-range order, although the thermal transition temperatures of GWS-GMP-100 complexes are not significantly affected by the water content. Only the type I complexes were formed under the heating conditions of 90°C for 60 min. The heating conditions of 90°C for 60 min after 100°C for 10 min facilitates the formation of type II complexes, and the amounts of type II complexes increased with increasing water content. The digestion rates of WS-GMP complexes decreased slightly with increasing water content, and the extent of starch amylolysis of WS-GMP complexes significantly decreased after heating further at 90°C compared with that only heating at 100°C. The digestibility of complexes is mainly related to structural order rather than the number of complexes. This study is helpful to further understand starch-lipid complexes by showing that heating conditions and water content influence the formation of WS-GMP complexes.

Evaluation of Tropane Alkaloids in Teas and Herbal Infusions: Effect of Brewing Time and Temperature on Atropine and Scopolamine Content.

Atropine and scopolamine belong to the tropane alkaloid (TA) family of natural toxins. They can contaminate teas and herbal teas and appear in infusions. Therefore, this study focused on analyzing atropine and scopolamine in 33 samples of tea and herbal tea infusions purchased in Spain and Portugal to determine the presence of these compounds in infusions brewed at 97 °C for 5 min. A rapid microextraction technique (µSPEed®) followed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to analyze the selected TAs. The results showed that 64% of the analyzed samples were contaminated by one or both toxins. White and green teas were generally more contaminated than black and other herbal teas. Of the 21 contaminated samples, 15 had concentrations above the maximum limit for liquid herbal infusions (0.2 ng/mL) set by Commission Regulation (EU) 2021/1408. In addition, the effects of heating conditions (time and temperature) on atropine and scopolamine standards and naturally contaminated samples of white, green, and black teas were evaluated. The results showed that at the concentrations studied (0.2 and 4 ng/mL), there was no degradation in the standard solutions. Brewing with boiling water (decoction) for 5 and 10 min allowed for higher extraction of TAs from dry tea to infusion water.

Intelligent Construction Technology of Hyperbolic Curtain Wall

Taking the hyperbolic glass curtain wall project of the Wuhan Jinyinhu Commercial Plaza as an example, the characteristics of different curved glass forming technologies were analyzed in this paper. Combined with the actual engineering situation, the curved steel process is selected to produce the hyperbolic glass curtain wall, and the application of BIM technology in the quality control of hyperbolic glass curtain wall in the production process was analyzed, and the effects of heating condition, bending time, cooling condition, and bending tempering error in the manufacturing accuracy of the curved glass curtain wall were studied, in hope that this project can provide practical reference for similar curtain wall design construction in the future.

Effect of heating conditions on the magnetic properties of micron-sized carboxyl modified-magnetite particles synthesized by a spray pyrolysis and heating process

Superparamagnetic carboxyl (COOH) modified-magnetite (Fe3O4) (COOH-Fe3O4) micrometer-sized porous particles were synthesized by the spray pyrolysis of a 0.1 M Fe(NO3)3·9H2O and 0.2 M citric acid solution and a subsequent heating process in either an Ar + 1% H2 (PO2 = 10−20 Pa) or N2 (PO2 = 1 Pa) gas atmosphere. Fe3O4 formed due to carbon and hydrogen gas generation of thermal decomposition of citric acid, even under reduction conditions with a PO2 below 10−23 Pa. The COOH-Fe3O4 particles heated in an Ar + 1% H2 or N2 atmosphere were porous (40% porosity) and about 1.2 to 1.3 μm in diameter. The particles consist of nano-sized COOH-Fe3O4 crystallite about 7 nm in diameter. The specific surface area increased from 116 to 127 m2/g by increasing the heating time in an Ar + 1% H2 atmosphere from 10 to 20 h. The saturation magnetization of the COOH-Fe3O4 particles (38.7 A·m2/kg) heated in Ar + 1% H2 for 10 h was much higher than that of commercial magnetic microbeads (17 A·m2/kg) and the coercivity was 0 kA/m. These superparamagnetic COOH-Fe3O4 particles dispersed in distilled water were attracted to a NdFeB magnet for 7–10 s under a 400 Mt external magnetic field, compared with 10 s for commercial magnetic microbeads.

Refrigerant film flow and heat transfer characteristics on the elliptical tube under constant wall temperature

• CFD models of falling film on horizontal tubes are verified by experimental data. • Effects of wall heating conditions on heat transfer of falling film are explored. • 11 refrigerants film flow and heat transfer under different temperature is studied. • Correlations of Nusselt number and film thickness for elliptical tubes are fitted. In this paper, the 2D model of the elliptical tube is established to simulate the film hydrodynamics and heat transfer performance. The volume of fluid (VOF) is used and the model is verified by the experimental data in the previous literature. The effects of the heating condition, fluid medium, inlet temperature ( T in ) on the film thickness and heat transfer coefficients are explored. The studied 11 refrigerants include ethane, propane, R123, R1234yf, R1234ze(E), R125, R134a, R143a, R152a, R227ea, R245fa at T in = –30, –10 and 10 °C. The results show at Re = 2000, the local heat transfer coefficients of the propane at T in = 10 °C under fixed heat flux are 19% greater than those under fixed wall temperature. Both the local film thickness and local heat transfer coefficients increase with Reynolds number ( Re ). The overall external heat transfer coefficients increase with Re , but the growth rate slows down at Re ≥ 1500. Fluids have different results of film thickness and heat transfer coefficients even they have a similar Kapitza number ( Ka ). Different from the water and seawater, the heat transfer coefficients reduce as the inlet temperature increases for the refrigerants. A correlation is proposed to predict local film thickness on both circular and elliptical tubes. A correlation is acquired by the fitting method to predict the overall external heat transfer coefficients under the heating condition of fixed wall temperature, which can capture 89% of 132 data within the deviations of ±10%.

Application and Effects of Ohmic-Vacuum Combination Heating on the Quality Factors of Tomato Paste.

Ohmic-vacuum combination heating is a common method used in the food industry as a concentration process. In the present study, an OH-VC combination heating system was developed for producing tomato paste at temperatures of 70, 80, and 90 °C and pressure of 0.3, 0.5, and 0.7 bar and electric field of 1.82, 2.73, and 3.64 V/cm using a central composite design. The effects of heating conditions on the quality and sensory evaluation of tomato paste were also evaluated. Each combination of temperature, pressure, and the electric field was quantified for specific energy consumption, energy efficiency, and productivity. A decrease of 35.08% in the amount of acid ascorbic and lycopene content 19.01%, using conventional heating compared to ohmic-vacuum heating under optimized conditions, was attained. The results also highlighted an increase in the amount of HMF (69.79%) and PME (24.33%) using conventional heating compared to ohmic-vacuum heating under optimized conditions. Ascorbic acid, lycopene, titratable acidity, productivity, energy efficiency was higher than conventional heating; on the other hand, HMF, PME, pH, SEC were lower than conventional heating at the applied OH-VC process. No significant effects between OH-VC and conventional heating on the TSS were observed. In addition, OH-VC heating was highly efficient in the inhibition of bacterial growth. Further, a minor effect on the sensory properties of tomato paste with OH-VC heating compared to the conventional treatment. The obtained results indicate a strong potential for an OH-VC combination heating system as a rapid-heating, high-efficiency alternative for saving electrical energy consumption and preserving nutritional value.

Experimental study and numerical simulation of heat transfer behavior based on silicone rubber/paraffin @SiO2 shape-stabilized phase change material

The leakage rate of solid-liquid phase change materials can be effectively reduced by shape-stabilized phase change material (SSPCM), but numerical simulations on SSPCM are less reported. This paper simulated the melting and solidification process of silicone rubber/paraffin@SiO2 shape-stabilized phase change material (SR/Pn@SiO2). The effects of heating conditions and the content of phase change microcapsules on the heat transfer process of SR/Pn@SiO2 were studied. The simulation results showed that thermal conductivity was the main factor affecting heat transfer during the melting process, while during the solidification process, enthalpy was the main factor. During the melting and solidification process, the heat transfer of SR/Pn@SiO2 composites mainly relied on heat conduction. The complete melting time of SR/Pn@SiO2 under heating conditions at 328 K took at most 280 s, while under 1000 W/m2 required at least 1700s. The specific heat transfer characteristics were elucidated by temperature, liquid fraction, flow rate, and total surface heat flux date.

Experimental and numerical study on collapse modes of single span steel portal frames under fire

This paper presents experimental and numerical investigations on the collapse modes of single span steel portal frames exposed to fire. A fire test on a scaled-down single span steel portal frame is conducted and measurements of deformation and collapse mode of the test frame are used to validate the numerical model for simulating the behavior of the single span steel portal frames subjected to fire. Four collapse modes of the portal frames, column lateral collapse, column buckling collapse, overall inward collapse and overall outward collapse, are revealed through parametric studies with the validated numerical model. The effects of heating conditions, stiffness of column base, temperature gradient, fire protection, load ratio, span-height ratio and column spacing on collapse modes of single span steel portal frames in fire are obtained. It is found that heating conditions, stiffness of column base and load ratio have a great impact on the portal frame collapse modes while temperature gradient and fire protection mainly affect the column collapse modes. The findings of this study lay the foundation for early-warning of fire-induced collapse of single span steel portal frames.

Experimental Study on Mechanical Property and Pore Distribution of Limestone Specimens after Heat Treatment under Different Heating Conditions

The thermal effect of rocks not only depends on the temperature level but also may be influenced by the factors including heating environment, heating rate, and cooling method. In this study, approximate vacuum (V) and air circulation (A) heating condition are, respectively, applied on the limestone specimens in the whole heating process. Then, physical, mechanical, and nuclear magnetic resonance (NMR) tests were carried out to investigate the effect of heating conditions on the rock properties. The results show that heating conditions have significant effects on mechanical properties of limestone specimens (including peak strength, elasticity modulus, secant modulus, and crack initiation stress), which are due to the interference effect on the oxidation and thermal decomposition. It is worth noting that the significant temperature range of the heating condition is 450 ∼ 750°C, during which the mechanical performances of heat‐treated specimens under V condition obviously outperform those under A condition. Combining the NMR results and the microstructure images from scanning electron microscope (SEM) technology, the evolution of pore distribution was revealed. As temperature increases from room temperature to 900°C, porosity increases gradually. However, pore distribution changes from small and medium pores dominating to large pore dominating and then to medium pore dominating. For limestone specimens after high‐temperature treatment above 450°C, mineral crystals may melt and reconsolidate, filling in some of the previously large pores generated by thermal decomposition.

High-frequency induction heating for increase of flow length in polymer/metal hybrid molding

Recent trends of miniaturization and multi-functionality in electrical parts have driven development of molded interconnect devices (MIDs) that contain conductive tracks on a nonconductive base. This study aims to develop polymer/metal hybrid molding technology to fabricate MIDs in a single manufacturing process, without an additional assembly procedure. For this purpose, injection molding was performed to fabricate a thermoplastic carrier that contained negative circuit channels, and die casting was used to fill the circuit channels with metal alloy of low melting point. To increase the flow length of the molten metal through the narrow circuit channel, high-frequency induction heating was used prior to the die casting stage. The effect of heating conditions on the mold temperature was investigated numerically, and the relevant induction heating conditions were determined accordingly. Induction heating was then applied to the die casting process to increase the flow length enough to be used as a circuit path for fabrication of MIDs.

Comparative study of ohmic vacuum, ohmic, and conventional-vacuum heating methods on the quality of tomato concentrate

Abstract In the present research, tomato juice was concentrated via Ohmic heating with two modes of operation, namely atmospheric condition (OHAC) and vacuum condition (OHVC), and conventional vacuum heating (CVH) as the control mode. The effect of heating conditions on the quality of tomato concentration (lycopene, turbidity, pH and acidity) and electrical conductivity were evaluated. The OHVC reduced the concentration time in the range of 10–30%, compared with the OHAC. The comparison of the mean value of the heating rate indicated that the vacuum application reduced the heating rate by 0.8%. The electrical conductivity of OHAC changed from 0.68 S/m at initiate point to 1.25 S/m at the boiling point then decreased to 1.05 S/m at the end of the process, the corresponding values for OHVC was 0.7, 1.13 and 1.11 S/m. The mean percentage change of pH, acidity, lycopene, and turbidity for OHVC were 0.47, 24.03, 7.99, and −30.77 respectively which were lower to the corresponding value for OHAC and CVH. It appears that the application of vacuum condition in the ohmic heating treatment of tomato juice can preserve juice quality. Industrial relevance Due to the high energy consumption of heating in the conventional processing methods, energy efficient systems are demanded for thermal concentration of juices. Ohmic heating is an emerging technology and a very promising in food industries. Comparing with conventional heating processes, ohmic heating can save energy and provide a rapid and uniform heating of pumpable food, resulting a product with a higher quality. The results showed that vacuum coupled with ohmic heating had a significant effect on quality. One of the keys to reducing the thermal damage to products during manufacture is the shortening of the heating time and reducing the boiling point, ohmic-vacuum heating required a lower time and boil at lower temperature, thereby is more advisable for thermal processing from the point of view of energy saving and quality aspects.

Effect of heating condition with steam convection oven on the properties of pumpkin and diffusion of food substrates

Effect of heating condition with steam convection oven on the properties of pumpkin and diffusion of food substrates

Hot stamping of high-strength aluminium alloy aircraft parts using quick heating

To improve the formability and productivity in conventional cold stamping of high-strength aluminium aircraft parts, a hot stamping process of heat-treatable aluminium alloy sheets using quick heating below the solution treatment temperature was developed. Quick heating just before forming has the function of producing sufficient strength increase in subsequent artificial ageing. This leads to the elimination of solution treatment and sizing processes for cold stamping. The effect of heating conditions was evaluated in hot hat-bending of A2024-T4 aluminium alloy sheets. In addition, an aluminium alloy aircraft part having high strength and dimensional accuracy was successfully produced by the present process.

Theoretical Investigations of the Effects of Isothermal and Non-isothermal Heating Conditions on the Pyrolysis Kinetics of Biomass Particle

There has been a growing interest in renewable energy sources from various part of the world over the past decades. One of the promising alternatives to fossil fuels is biomass and in all the common technologies of its conversion, pyrolysis is present atleast as a first stage of the conversion process. As part of the scientific studies and understanding of this very important process in the thermochemical conversion of the solid fuel, the development of good mathematical models which in consequent leads to the design of pyrolysis reactors and biomass gasifiers is paramount. However, due to the complexities of the biomass reaction scheme, the pyrolysis of biomass is generally modeled on the basis of apparent kinetics. Moreover, most of the past works were based on the overall pyrolysis kinetics, and studies concerning pyrolysis products are much less common. Therefore, this work presents the analytical solutions of the kinetics of pyrolysis of biomass particle under non-isothermal and isothermal heating conditions. The developed models were used to investigate the effects of heating conditions and heating rates on the pyrolysis of wood products. The comparison of the simulated results with the available results reported in literatures show good agreements were found. This work could be used in predetermining the biomass products concentrations under different heating conditions and the estimating the optimum parameters in the pyrolysis of biomass and in the design of some pyrolysis reactors/units.

Development of polyol method for the synthesis of concentrated colloids of PVP-stabilised Ru nanoparticles

In the current work narrowly distributed and stable Ru nanoparticles (NPs) with mean diameters within 1.7 to 2.8 nm interval were prepared by reduction of RuCl3 with ethylene glycol (EG) as a solvent and a reducing agent as well as polyvinylpyrrolidone (PVP) as a stabiliser in the temperature range from 170°C to 198°C. Besides a typical polyol technique, Ru NPs synthesis using microwaves as well as sodium borohydride reduction at room temperature was applied as an effective alternative approach. The effect of heating conditions, Ru/PVP ratio, reducing agent and metal precursor concentrations on the particle size was studied. Microstructure of Ru NPs was characterised by UV Vis, XPS and HRTEM. Higher PVP/Ru ratios and reduction temperature gave slightly smaller nanoparticles with narrower size distributions, while no clear effect was observed when the initial ruthenium concentration was varied.

Computational Fluid Dynamics Study of Heat Transfer in an Industrial Heat-carrier-free Regenerative Rotating Bed

Abstract In this paper, a comprehensive computational fluid dynamics model was built to study the heat transfer of coal in the Heat-Carrier-Free Regenerative Rotating Bed (HRRB). In comparison to the experimental data in the pilot scale HRRB, the model gave a satisfied prediction and was further extended to study the flow field and temperature distribution in the industrial HRRB. The effect of heating conditions on the temperature distribution of coal was also obtained. The results indicated a promising way to improve the output of upgraded coal in the industrial HRRB.

Effect of heating conditions on the formation of welded joints in fusion welding of small components for nuclear power engineering

Special features of the effect of fusion welding conditions of small components on the possibility of formation of high-quality welded joints are investigated. The concept of ‘small components’ is defined taking into account the quality criteria of welded joints. It is shown that the weldability of small components can be improved by restricting the thermal effect on the welding zone. Examples of components produced by the methods of argon-shielded welding by melting the end and laser welding in pulsed conditions, which restrict the thermal effect on the small components, are described.

Using Numerical Analysis to Develop and Evaluate the Method of High Temperature Sous‐Vide to Soften Carrot Texture in Different‐Sized Packages

The high-temperature sous-vide (HTSV) method was developed to prepare carrots with a soft texture at the appropriate degree of pasteurization. The effect of heating conditions, such as temperature and time, was investigated on various package sizes. Heating temperatures of 70, 80, and 90 °C and heating times of 10 and 20 min were used to evaluate the HTSV method. A 3-dimensional conduction model and numerical simulations were used to estimate the temperature distribution and the rate of heat transfer to samples with various geometries. Four different-sized packages were prepared by stacking carrot sticks of identical size (9.6 × 9.6 × 90 mm) in a row. The sizes of the packages used were as follows: (1) 9.6 × 86.4 × 90, (2) 19.2 × 163.2 × 90, (3) 28.8 × 86.4 × 90, and (4) 38.4 × 86.4 × 90 mm. Although only a moderate change in color (L*, a*, and b*) was observed following HTSV cooking, there was a significant decrease in carrot hardness. The geometry of the package and the heating conditions significantly influenced the degree of pasteurization and the final texture of the carrots. Numerical simulations successfully described the effect of geometry on samples at different heating conditions.

The effect of heating conditions on micropore formation during the carbonization of polyimide films

Carbon films were prepared by the heat-treatment of polyimide (PI) films at different temperatures between 400 °C and 900 °C. Heat-treatment was carried out by two methods (one-step and step-wise methods). In the one-step method, the temperature was increased directly to the pyrolysis temperature. In the step-wise method, the temperature was increased to the pyrolysis temperature in steps of 100 °C. The micropore surface area of the carbon films obtained was estimated from the α s -plots of the nitrogen-adsorption isotherms at-196 °C. In the one-step method, the micropore surface areas of the carbon films heat-treated at 800 °C and 900 °C were 400 m2 g−1 and 600 m2 g−1, respectively. Micropores were not formed for the carbon films heat-treated at 700 °C in the one-step method. On the other hand, in the step-wise method, the micropore surface areas of the carbon films heat-treated at 700, 800 and 900 °C were 340 m2 g−1, 440 m2 g−1 and 230 m2 g−1, respectively. These results suggested that heat treatment method largely affects the micropore structure of the carbon films derived from PI. [TANSO 2014 (No. 261), 14–18.]

Study of the Effect of Heating Conditions During Directional Crystallization on Structural Parameters of Intermetallic VKNA-4UMono Alloy

Comparative studies are provided for the effect of heating conditions for directional crystallization in two types of unit: with liquid-metal cooling (unit UVNK-9A), i.e., LMC process, and with radiation cooling (unit of the firm ALD), i.e., high rate solidification (HRC) process, on VKNA-4UMono alloy cast structure parameters. Comparative analysis is provide for microstructure and strength properties obtained with short-term tensile tests for castings of alloy VKNA-4UMono [111] from both units.