Superheated Steam Research Articles

Experimental Study of Influence of Initial Air Temperature on Characteristics of Combustion of Diesel Fuel Atomized by Jet of Superheated Steam

Experimental Study of Influence of Initial Air Temperature on Characteristics of Combustion of Diesel Fuel Atomized by Jet of Superheated Steam

Combined effects of low pressure superheated steam drying and vacuum drying on sugar reduction and quality attribute in mango (Mangifera indica L.) slices

Abstract Consumers paying more attention to physical health has led to an increasing market demand for low-sugar dried fruit products. The quality of products dried via low pressure superheated steam drying (LPSSD) is not only superior to those dried via conventional hot air or vacuum drying (VD), but also has the potential to reduce sugar content. In order to elucidate the mechanism of reducing the sugar of mango slices by LPSSD and obtain low-sugar dried mango slices, the combined effect of LPSSD–VD on mango slices was studied and an evaporation experiment of a sugar solution in a low pressure superheated steam environment was performed. This study revealed that the sugar reduction of mango slices was mainly due to the superheated steam carryover phenomenon in the second half of the constant-temperature stage and the occurrence of Maillard reaction during LPSSD. The quality attributes of mango slices dried using LPSSD–VD was improved compared with LPSSD and VD. As a result, LPSSD–VD could be used to regulate the sugar content in dried fruit and provide a theoretical basis for the production of low-sugar preserved fruits.

The hygroscopic behavior of surface compressed wood in response to superheated steam treatment at varying steam pressures

Superheated steam treatment has been shown to be an efficient strategy for enhancing the dimensional stability of compressed wood. This study evaluated the hygroscopic behavior of surface compressed (SC) wood subjected to superheated steam treatment (SHTSC wood) at varying steam pressures (0.1 MPa, 0.3 MPa, 0.5 MPa, and 0.7 MPa). As the steam pressure increased, the equilibrium moisture content (EMC) of SHTSC wood showed a gradual decrease throughout the hygroscopic range, indicating improved hygroscopic stability. The reduction in EMC for SC wood was associated with a decrease in polylayer moisture content (Ms) from 0% to 95% RH, while the EMC reduction for SHTSC wood was attributed to the combined effect of diminished monolayer (Mh) and Ms. The superheated steam treatment resulted in a range of chemical alterations in the SHTSC wood, including a decrease in hemicelluloses content and the quantity of sorption sites (–OH, C–O groups). Concurrently, there was a relative augmentation in the content of cellulose and extractives, alongside a heightened degree of lignin cross-linking. Furthermore, the superheated steam treatment also affected the cellular structure of the SHTSC wood, resulting in an increased ratio of macropores to mesopores, as well as the formation of microcracks within the cell wall. These changes became more pronounced as the steam pressure elevated, contributing to the reduced hygroscopic characteristics and improved dimensional stability of SHTSC wood.

Experimental and Numerical Study of Superheated Steam Drying for Sliced Avocado

AbstractSuperheated steam drying (SSD) of sliced avocado is studied by both experiment and theory. An experimental system is built to evaluate the effects of drying temperature and gas velocity on the evaporation rate and color change of the product. Experiments are conducted for ripened Booth avocado from Daklak province of Vietnam. Experimental results show that evaporation is faster at higher temperatures and velocities, but the effect of temperature decreases at higher velocities. At temperatures below 130 °C, the product is not brown, but at a temperature in the range of 130–150 °C, the dried sample is burned. The experimental model is fitted with high accuracy to predict the moisture rate as a function of time. The evaporation processes of SSD are also compared with hot air drying at the same drying conditions. To extend the application ability of the result, the theoretical model is developed on the basis of Fick's law in which the spatial distributions of temperature and moisture are taken into account. The effective diffusivity is determined by an optimization tool with good agreement. This parameter is constant for all drying conditions, so the model can be applied to a huge range of drying conditions. The numerical results show that the temperature is almost uniform in the sample because of high thermal conductivity, but the moisture gradient is significant.

Experimental study on high-energy fluid jets from a pipe: Jet cone morphology and impact force on flat plates

Owing to potential adverse effects such as fatigue, vibration, scouring, and inherent defects, high-pressure pipelines in chemical processes may fail during operation. After failure, high-energy fluid jets into the surrounding space, causing damage to the surrounding equipment and personnel. In extreme cases, the load generated by the jet exerts a reaction force at the pipeline failure point, which causes the pipeline to produce a strong whip, further endangering surrounding systems. To prevent such fundamental and secondary damages, it is important to study the magnitude of the impact force caused by the jetting process and the extent of the impact of the jet cone on surrounding objects.In this study, an experimental visualization system was utilized that allowed for a continuous and stable heating-jetting-cooling-recovery process for the working fluid. The distance between the nozzle and the impacted target plate can be adjusted on purpose. In this system, deionized water was heated to various conditions (1–8 MPa; 20–344 ℃) and different states, such as sub-cooled water, two-phase flow, and superheated steam, and then discharged into an atmospheric-pressure environment through pipes of different diameters (2.4–9.2 mm) and length-to-diameter ratios (20–120). Subsequently, the jet cone expanded freely or impacted plates of various sizes and at different distances. Based on the stability and flexibility of this experimental system, new details regarding the jetting process were obtained. Ultimately, a series of experimental data on the jet impact force were obtained, and the expansion morphology of the fluid in the atmospheric-pressure environment was recorded via a high-speed camera.The experimental results indicate that the water state parameters and the nozzle/pipe structural dimensions significantly affect the shape of the jet cone as well as the magnitude and variation pattern of the jet impact force. Additionally, the jet impact force varies with the distance from the outlets and the plate dimensions.

Study on the corrosion mechanism of Zr-1Sn-xFe-0.2Cr-0.02Ni alloy in 500 °C super-heated steam with oxygen

Zr-1Sn-xFe-0.2Cr-0.02Ni (x=0.3, 0.45, wt%) alloys were exposed in 500 °C super-heated steam with oxygen to investigate the effect of oxygen concentrations in the corrosion environment and Fe contents in the alloys on the corrosion behavior. Results showed that increasing the Fe contents from 0.3 % to 0.45 % and the oxygen concentrations from deaeration to 1000 ppb can both accelerate the corrosion of the alloys, and the mechanism was explored from the perspective of Fe and oxygen affecting the oxidation of alloying elements and the microstructure evolution of the oxide film.

Comparative study on physicochemical, nutritional and cooking properties of different pigmented dehusked rice varieties influenced by superheated steam treatment

Superheated steam (SS) treatment has emerged as a pivotal technique for improving cereal quality, specifically rice quality in the present studies. This study investigated the effects of SS treatment on the physicochemical characteristics and cooking attributes of pigmented dehusked rice, focusing on three rice varieties: black rice (BLR), red rice (RR), and brown rice (BR). Employing SS treatment was found to not only preserve the desirable appearance of pigmented dehusked rice but also to significantly reduce its cooking duration and overall hardness. A notable preservation of total phenolic content is observed in BLR, contrasting with a pronounced reduction ranging from 41.96% to 46.38% in RR and 26.13%–48.14% in BR. Flavonoid levels across all rice varieties declined to varying extents, from 1.42% to 8.03% in BLR, 8.20%–16.39% in RR, and 28.61%–46.50% in BR, accompanied by a significant reduction in anthocyanin content. Furthermore, SS treatment substantially elevated the total volatile organic compounds in cooked BLR. This study highlights the nuanced impact of SS treatment across different rice varieties, offering insights into its potential for enhancing the culinary and nutritional value of pigmented cereals.

Ambient Temperature and Relative Humidity Remained Stable after Prolonged Application of Superheated Steam in Enclosed Spaces

Ambient Temperature and Relative Humidity Remained Stable after Prolonged Application of Superheated Steam in Enclosed Spaces

A Novel Designation of Solid Oxide Fuel Cell-Integrated System Using LPG as Fuel for Marine Vessels

A Novel Designation of Solid Oxide Fuel Cell-Integrated System Using LPG as Fuel for Marine Vessels

Failure analysis of steam superheater boiler tube made of ASTM T22 steel

This study investigates the failure of T22 grade steel boiler tube, as per ASTM A 213/A A213M standards, which experienced significant plastic deformation with a characteristic 'fish mouth' appearance. Analysis revealed an increase in outer diameter up to 18 percent, coupled with a reduction in wall thickness from 8.8 mm to around 3 mm at the rupture site. Microstructural examination of samples taken away from the rupture site revealed a structure composed of ferrite and partially decomposed bainite, attributed to prolonged annealing, along with fine spherical carbide precipitates. Samples from the rupture area displayed ferritic-bainitic structure without secondary carbide precipitates, indicating exceeded transformation temperatures. Additionally, increased hardness in the rupture area suggested transitions of overcooled austenite into ferrite and bainite. Thickened scale, particularly on the inner surface, heightened the risk of overheating. Based on these findings, it was concluded that the tube failure resulted from short-time overheating.

Effect of severe torrefaction by superheated steam on pinewood pyrolysis kinetics and pyrolytic oil compounds

Hemicellulose, cellulose, lignin and extractives generally contribute a variety of compounds to pyrolytic oil during pyrolysis. Severe torrefaction process to remove those compounds may influence the diversity and quality of pyrolytic oil. In this study, pinewood, as a frequently studied biomass for pyrolysis research, was firstly torrefied by superheated steam (SHS) in different intensities prior to both slow pyrolysis and Py-GCMS. The kinetic study demonstrated that the activation energy of pyrolysis for the biomass increased greatly from 172.66 kJ mol−1 to a maximum of 400.18 kJ mol−1 after SHS torrefaction. The pyrolytic oil from both slow pyrolysis and Py-GCMS were analyzed. The content of hemicellulose and cellulose biomass reduced with increasing SHS torrefaction intensities. As a result, the light oxygenates, sugars and furans in pyrolytic oil decreased greatly, whereas the concentration of phenol and aromatics improved. In addition, the phenolic compounds shifted to smaller molecular weight and the acetic acid as an adverse factor in pyrolytic oil decreased and even disappeared under severe torrefaction. SHS torrefaction provide a new insight for biomass pretreatment for further pyrolysis.

Assessing parabolic trough collectors and linear Fresnel reflectors direct steam generation solar power plants in Northwest México

Concentrating solar power (CSP) systems offer promising solutions for harnessing solar energy. Parabolic trough collectors (PTC) are prevalent in CSP, but direct steam generation (DSG) in solar fields is an innovative alternative that eliminates the need for thermal oils. This study compares EuroTrough PTC and optimized linear Fresnel reflector (LFR) geometries for DSG for Mexican operating conditions. Two 10 MW Rankine cycles with two and three steam extractions are considered. The study evaluates 16 solar field configurations capable of delivering 400 °C superheated steam at 100 bar. Assessment parameters include effective concentration area, nominal loop inlet pressure, energy and exergy efficiency, and hypothetical thermal storage size. The findings strongly favor PTC solar fields with 14 loops, exhibiting superior performance. However, three-loop LFR configurations are suggested where pressure reduction prevails. Three-loop LFR arrays minimize land utilization for spatially constrained installations, while larger five-loop configurations optimize efficiency. Employing 14 PTC loops prioritizes thermal energy storage. In contrast, 8 PTC loops maximize storage capacity. The study underscores the advantages of Fresnel reflectors over parabolic troughs in specific scenarios, presenting avenues for future exploration. This analysis lays the groundwork for assessing these technologies in the distinctive context of Mexican operations, offering valuable insights into sustainable energy applications.

Effect of superheated steam treatment on enzyme inactivation, morphostructural, physicochemical and digestion properties of sand rice (Agriophyllum squarrosum) flour

The lipase (LA) and peroxidase (POD) activities, as well as morphological structure, physicochemical and digestion properties of sand rice flour (SRF) treated with superheated steam (SS), were investigated. SS treatment at 165 °C completely deactivated LA and resulted in a 98% deactivation of POD activities in SRF. This treatment also intensified gelatinization, induced noticeable color alterations, and decreased pasting viscosities. Furthermore, there was a moderate reduction in crystal structure, lamellar structure, and short-range ordered structure, with a pronounced reduction at temperatures exceeding 170 °C. These alterations significantly impacted SRF digestibility, leading to increased levels of rapidly digestible starch (RDS) and resistant starch (RS), with the highest RS content achieved at 165 °C. The effectiveness of SS treatment depends on temperature, with 165 °C being able to stabilize SRF with moderate changes in color and structure. These findings will provide a scientific foundation for SS applicated in SRF stabilization and modification.

Thermal Hydraulic Analysis of Turbulent Flow of Superheated Steam Through Multiple Configurations of 3D Angular Piping Bend in Power Plant Installations

Abstract One of the most vulnerable parts in high-pressure and temperature pipeline networks in steam turbine power plant installations is pipe bends, due to intense fluctuation of velocity and pressure of the superheated steam flowing through the piping bend. On the other hand, because of unique chemical and physical properties, the transportation of superheated steam can adversely effect on the integrity of the pipe bends in the piping network. Therefore, the potential risk of pipeline failure becomes more probable at bends. Therefore, to ensure the survivability of the piping network, thorough investigations of the superheated steam flowing through pipe bends are of great significance in better understanding its flow behavior. However, to predict flow behavior at piping bend, intensive research by direct experiment at high temperature and pressure might not be possible to some extent. In that case, computer codes and models can help us analyze flow behavior of superheated steam at pipe bends. The current work is a computational fluid dynamics investigation, where numerical examination is carried out by commercial code ansys fluent for thermal hydraulic analysis of flow behavior of superheated steam through multiple configurations of 3D angular piping bend: 90 deg, 120 deg, and 135 deg. Validation of credibility of the computational approach is done against Sudo et al.'s experiment. With relatively good agreement between the experiment and numerical result using air flowing through 90 deg elbow, single-phase turbulent flow of superheated steam is examined by the application of realizable turbulence model (k–ɛ). The final assessment of the computed results has been done using qualitative and quantitative analyses. The study reveals that unlike the pressure profiles, the radial velocity profiles at the bend exit are noticeably different from those at the bend inlet, since they exhibit more rounded peaks and gentler velocity gradients. The study also shows that the radial pressure and velocity profiles do not display any sign of the existence of a pair of vortices.

Catalytic aquathermolysis of contaminated polyolefin plastic waste over an in situ iron hydroxide/oxide nanocatalyst derived from an oil-soluble iron precursor

With the substantial increase in global plastic consumption over the past 50 y, society faces the challenges of managing and recovering resources from considerable amounts of plastic waste. A promising strategy for use in addressing this problem is to upcycle plastic waste into valuable materials via thermochemical conversion, and hydrothermal liquefaction, which uses low-cost and green H2O, has attracted attention as a sustainable technology. In this study, we introduced an aquathermolysis system using oil-soluble Fe-2-ethylhexanoate (Fe-2EH) as a catalyst precursor under superheated steam conditions to convert highly contaminated polyolefin plastic waste to liquid fuel. The excellent dispersibility and decomposition behavior of Fe-2EH facilitated the formation of highly dispersed in situ Fe-based catalysts, enabling their involvement in the early stages of aquathermolysis. The presence of H2O and the in situ catalyst significantly promoted the decomposition of C–X bonds (X = Cl, S, N, or O) rather than C–C bonds, and C–C cleavage was driven by thermal energy. Moreover, the presence of H2O with the catalysts reduced the proportion of non-paraffinic products, including olefins and aromatics that cause char/coke formation. During the reaction, the in situ catalyst particles comprised nanosized Fe oxide cores with Fe hydroxide-rich surfaces, preventing the accumulation of metal contaminants. Based on deuterium tracing studies, the H transfer index of the catalyst was closely related to the catalytic performance. These results indicated that catalytic aquathermolysis using Fe-2EH is an efficient system for use in improving product quality by effectively removing contaminants and suppressing char/coke formation.

The effect of the inlet steam superheat degree on the non-equilibrium condensation in steam turbine cascade

Due to the high steam velocity and low thermal parameters at the turbine's final stage, steam generates non-equilibrium condensation and forms a large number of small droplets during the process of pressure expansion. The wet steam mixed with droplets impinges on the turbine blades, endangering turbine operation safety and reducing turbine work efficiency. This article modifies the non-equilibrium condensation control equation and embeds it into the numerical simulation software to make the numerical calculation results more accurate. By modifying the inlet steam superheat in the classical experiments, the condensation characteristics of wet steam in Moses–Stein nozzles and Dykas cascades are studied. The results show that increasing inlet superheat can effectively suppress the generation of non-equilibrium condensation and reduce outlet liquid mass fraction. The minimum supercooling temperature of non-equilibrium condensation is only related to the working fluid characteristics (the steam model used in this article is around 20 K). When the inlet superheat of the cascade is large, the rapid condensation region is mainly near the suction surface. In contrast, when the superheat is low, the rapid condensation zone is mainly near the pressure surface. The condensation location is mainly affected by the intensity of internal condensation shock waves in the cascade. Increasing inlet superheat not only increases the shock wave intensity but also decreases the shock wave angle in the passage. When the inlet temperature increases by 20 K, the heat efficiency of the cascade increases by about 1%.

Pre-gelatinization phenomenon and protein structural changes in rice quality modification by superheated steam treatment

This study aimed to investigate the effects of superheated steam treatment (SST) on the physicochemical properties, cooking characteristics, and protein structure of rice. According to the results, SST significantly increased the degree of gelatinization, decreased all pasting viscosities and gelatinization enthalpy of rice. Additionally, SST increased the hardness and viscosity of the rice samples. The taste value of SST rice at 155 °C for 10 s increased from 78.5 to 84. Furthermore, SST led to a reduction in the extraction rate of rice proteins, and their secondary structure became ordered. This study also studied the aggregation behavior of rice proteins. These results provide a new perspective on the effects of SST on rice quality modification, especially on pasting characteristics and taste quality, which will contribute to the promotion of SST as a sterilization and modification method in the fresh instant rice industry.

Stress corrosion cracking susceptibility of a new nickel‐based alloy in different environments

AbstractStress corrosion cracking (SCC) susceptibility of a new nickel‐based alloy C‐HRA‐2 under two types of superheated steam (SHS) (0.1 and 8 MPa) and supercritical water (SCW) (25 MPa) at 650°C was studied through slow strain rate tensile tests at a strain rate of 5 × 10−7 s−1. The results indicate that C‐HRA‐2 exhibits SCC susceptibility in both SHS and SCW, and the susceptibility increases with increasing pressure. Transgranular fracture (located inside) characterized by dimples/micropores and intergranular fracture (located at the edge) characterized by rock‐sugar‐like morphology was observed in all specimens. The brittleness of the alloy increases with the increase of medium pressure. A large number of cracks perpendicular to the loading axis were noticed on the gauge surface. The SCC mechanism of C‐HRA‐2 under steam and SCW is dynamic embrittlement.

Registration of the atmospheric effect of the Hunga Tonga volcano eruption

The paper presents the results of recording of acoustic waves, caused by the Hunga Tonga volcano eruption in the South Pacific Ocean on January 15, 2022, in Eastern Siberia at a distance of about 11230 km from the eruption. The received acoustic signal is interpreted as a set of atmospheric waves in a wide range of oscillations. The structure of the signal is similar to signals from the previously known powerful sources: the thermonuclear explosion on Novaya Zemlya in 1961 and the explosion of the Tunguska meteorite in 1908. The acoustic signal was preceded by three trains of low-frequency damped oscillations. We assume that these three trains of oscillations are associated with three important stages in the Hunga Tonga volcano eruption: 1) destruction of Tonga island and formation of an underwater caldera; 2) release of hot magma from the caldera to the ocean surface and release of a large volume of superheated steam into the atmosphere 3) formation of a layered structure from a mixture of superheated steam, ash, and tephra on the ocean surface and formation of an eruptive convective column. Successive phases of the eruption might have contributed to the excitation of acoustic vibrations in a wide range of periods including Lamb waves, internal gravity waves (IGW), and infrasound. We compare the structure of the acoustic signal received in Siberia at a distance of more than 11000 km from the volcano and that of the acoustic signal recorded in Alaska at a distance of more than 9300 km. Using the solution of the linearized Korteweg — de Vries equation, we estimate the energy released during the volcanic eruption.

О регистрации атмосферного эффекта извержения вулкана Хунга-Тонга

The paper presents the results of recording of acoustic waves, caused by the Hunga Tonga volcano eruption in the South Pacific Ocean on January 15, 2022, in Eastern Siberia at a distance of about 11230 km from the eruption. The received acoustic signal is interpreted as a set of atmospheric waves in a wide range of oscillations. The structure of the signal is similar to signals from the previously known powerful sources: the thermonuclear explosion on Novaya Zemlya in 1961 and the explosion of the Tunguska meteorite in 1908. The acoustic signal was preceded by three trains of low-frequency damped oscillations. We assume that these three trains of oscillations are associated with three important stages in the Hunga Tonga volcano eruption: 1) destruction of Tonga island and formation of an underwater caldera; 2) release of hot magma from the caldera to the ocean surface and release of a large volume of superheated steam into the atmosphere 3) formation of a layered structure from a mixture of superheated steam, ash, and tephra on the ocean surface and formation of an eruptive convective column. Successive phases of the eruption might have contributed to the excitation of acoustic vibrations in a wide range of periods including Lamb waves, internal gravity waves (IGW), and infrasound. We compare the structure of the acoustic signal received in Siberia at a distance of more than 11000 km from the volcano and that of the acoustic signal recorded in Alaska at a distance of more than 9300 km. Using the solution of the linearized Korteweg — de Vries equation, we estimate the energy released during the volcanic eruption.