High Temperature Water Research Articles

The effect of chromium-based coatings on corrosion behavior of alloy Zr1Nb in 70ppm Li+ water environment

Recent research indicates that one of the leading candidates for Accident Tolerant Fuels (ATF) are chromium-based coatings deposited on the commercially used zirconium alloys. The chromium-based coatings seem to improve the corrosion kinetics of underlying zirconium in both primary water and steam, where zirconium fails to meet the safety requirements. It is well known that the corrosion kinetics of zirconium can be negatively influenced by high concentrations of lithium ions. To evaluate the effect of chromium-based coatings on corrosion behavior of zirconium alloys in water containing elevated concentrations of lithium, Cr and CrN/Cr multilayer coated Zr1Nb alloy was tested in high temperature water containing 70 ppm Li+. Using Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDX), we have found that the chromium coating could have a positive effect on the underlying material as it behaves as a good diffusion barrier for oxygen and Li+ions. On the other hand, CrN/Cr coating, due to not sufficient structural integrity of the multilayer, showed non-protective behavior to the Zr1Nb alloy. Our results suggest that certain chromium coatings can significantly enhance corrosion resistance in lithium containing water environments.

Computational Fluid Dynamics Modelling of the Temperature Distribution in Power Plant's Cooling Canal

Seawater used as a heat exchanger in the coal-fired power plant condenser system has a higher water temperature than the natural temperature of seawater. There was an increase in the temperature of the waters around the coal-fired power plant due to the discharge of boiling water reaching 6.50C. According to the regulations in force in Indonesia, the hot water temperature at the water discharge outlet should not be more than 20C of the natural temperature of seawater. The purpose of this study is to predict the pattern of temperature decrease in the temperature of the boiling water along the cooling line. The method used to predict temperature drop patterns along the cooling line uses a 3-dimensional CFD (Computational Fluid Dynamics) modelling approach with the Ansys Fluent 2023 RI application. The K-Epsilon turbulence model was chosen to describe the effect of flow turbulence on temperature changes. The modelling results were validated by comparing the actual measurements of the water temperature field data representing along the cooling line. The results showed that the performance of reducing the temperature of the water increased when passing through the cascade aeration downstream of the channel. The flow of water along the channel tends to be on the lower side, and downstream, the flow is on the left–middle side. The error calculation using MAPE resulted in 9.49%.

Comparative evaluation of the antihyperglycemic effects of three extracts of sea mustard (Undaria pinnatifida): In vitro and in vivo studies

Undaria pinnatifida (UP) contains multiple bioactive substances, such as polyphenols, polysaccharides, and amino acids, which are associated with various biological properties. This study aimed to evaluate the antihyperglycemic effects of three extracts obtained from UP. UP was extracted under three different conditions: a low-temperature water extract at 50 °C (UPLW), a high-temperature water extract at 90 °C (UPHW), and a 70 % ethanol extract (UPE). Nontargeted chemical profiling using high-performance liquid chromatography-triple/time-of-flight mass spectrometry (HPLC−Triple TOF−MS/MS) was conducted on the three UP extracts. Subsequently, α-glucosidase inhibitory (AGI) activity, glucose uptake, and the mRNA expression of sodium/glucose cotransporter 1 (SGLT1) and glucose transporter 2 (GLUT2) were evaluated in Caco-2 cell monolayers. Furthermore, an oral carbohydrate tolerance test was performed on C57BL/6 mice. The mice were orally administered UP at 300 mg/kg body weight (B.W.), and the blood glucose level and area under the curve (AUC) were measured. Compared with glucose, UPLW, UPHW and UPE significantly inhibited both glucose uptake and the mRNA expression of SGLT1 and GLUT2 in Caco-2 cell monolayers. After glucose, maltose, and sucrose loading, the blood glucose levels and AUC of the UPLW group were significantly lower than those of the control group. These findings suggest that UPLW has antihyperglycemic effects by regulating glucose uptake through glucose transporters and can be expected to alleviate postprandial hyperglycemia. Therefore, UPLW may have potential as a functional food ingredient for alleviating postprandial hyperglycemia.

Effects of inbreeding and elevated rearing temperatures on strategic sperm investment.

Males often strategically adjust the number of available sperm based on the social context(i.e. sperm priming response), but it remains unclear how environmental and genetic factors shape this adjustment. In freshwater ecosystems, high ambient temperatures often lead to isolated pools of hotter water in which inbreeding occurs. Higher water temperatures and inbreeding can impair fish development, potentially disrupting sperm production. We used guppies (Poecilia reticulata) to investigate how developmental temperature (26 °C, 30 °C) and male inbreeding status (inbred, outbred) influence their sperm priming response. We also tested if sperm priming was affected by whether the female was a relative (sister) and whether she was inbred or outbred. There was no effect of rearing temperature; male inbreeding status alone determined the number of available sperm in response to female presence, her inbreeding status, and her relatedness. Inbred males produced significantly more sperm in the presence of an unrelated, outbred female than when no female was present. Conversely, outbred males did not alter the number of sperm available in response to female presence or relatedness. Moreover, inbred males produced marginally more sperm when exposed to an unrelated female that was outbred rather than inbred, but there was no difference when exposed to an inbred female that was unrelated versus related. Together, a sperm priming response was only observed in inbred males when exposed to an outbred female. Outbred females in our study were larger than inbred females, suggesting that inbred males strategically allocated ejaculate resources toward females in better condition.

Palliative effect of abalone insulin-related peptide 2 on emersion stress-induced hyperglycemia in the Pacific abalone (Haliotis discus hannai)

The Pacific abalone (Haliotis discus hannai), an economically important marine mollusk in East Asia, is often exposed to extreme environments, such as high water temperatures during summer and air exposure during handling or transportation. These stressful conditions lead to hyperglycemia and the generation of reactive oxygen species (ROS), resulting in oxidative stress and subsequent cell damage in the organism. To understand the role of insulin-related peptides in the regulation of elevated hemolymph glucose, hyperglycemia was confirmed in abalone under high water temperature and air (emersion) exposure (p < 0.05). To prove the existence of a glucose regulatory system in abalone, changes in hemolymph glucose were measured after bovine insulin injection, and hemolymph glucose was lowered by bovine insulin injection in hyperglycemia caused by both stressors (p < 0.05), supporting the existence of a glucose regulatory system functionally similar to that of vertebrates. Among the three abalone insulin-related peptides (AIPs), which were previously reported to be upregulated along with hemolymph glucose levels upon feeding, the relative mRNA expression of AIP2 in the cerebral ganglion showed a close correlation with high water temperature and emersion stress, which peaked 12 h after treatment (p < 0.05). Based on these results, we focused on the function of AIP2 in glucose homeostasis and characterized the localization of AIP2 mRNA-expressing cells in the cerebral ganglion using in situ hybridization. Positive signals from RNA probes were detected in neural cortex cells in the cerebral ganglion. Furthermore, suppressing AIP2 mRNA expression using RNA interference with double-stranded RNA (dsRNA) revealed that dsRNA-AIP2 injected abalone maintained high hemolymph glucose levels after 24 h of recovery following 1 h of emersion stress (p < 0.01). In contrast, abalones that received dsRNA-GFP and molluscan saline showed relatively rapid clearance of hemolymph glucose. This study demonstrates that AIP2 gene expression affects the recovery rate from emersion stress-induced hyperglycemia by regulating hemolymph glucose.

On corrosion of zirconium alloy in dissolved oxygen water: The role of Cu addition

It is significantly important to improve the corrosion resistance of Zr-Sn-Nb alloys in dissolved oxygen (DO) high temperature water by compositional modification. Here, the effect of Cu addition on the corrosion behaviors of Zr-0.5Sn-0.2Nb-0.4Fe-0.2Cr alloy was studied by using an autoclave circulating water loop at 360 °C/20 MPa up to 250 days. The oxide microstructures were characterized by a combination of SEM, TEM, STEM-EELS and PED. The results showed that compared with 0Cu alloy and 0.07Cu alloy, 0.13Cu alloy shows better corrosion resistance and its final weight gain after 250 days exposure is even lower than that of commercial Zr-4 alloy. The oxides for 0.07Cu and 0.13Cu alloys show more ordered crystals, thinner oxide and less lateral cracks, and the columnar grains show a stronger {10–3} texture, compared to Cu-free counterpart. The t-Zr2Cu SPPs have oxidized in the oxygen-rich layer below the O/M interface. The Cu ions tend to diffuse towards the grain boundary of dense columnar grains and maybe strengthen the grain boundaries, avoiding the defect generation under intrinsic stress in the oxide.

Migration patterns of the Japanese sardine in the Sea of Japan by combining the microscale stable isotope analysis of otoliths and an ocean data assimilation model

The Japanese sardine (Sardinops sagax melanostictus) is a small pelagic fish found in the Sea of Japan, the marginal sea of the western North Pacific. It is an important species for regional fisheries, but their dispersal and migration patterns during early life stages remain unclear. In this study, we analyzed the stable oxygen isotope ratios of otoliths of young-of-the-year (age 0) Japanese sardines collected from the northern offshore and southern coastal areas of the Sea of Japan in 2015 and 2016. The ontogenetic shifts of the geographic distribution were estimated by comparing the profiles of life-long isotope ratios and temporally varying isoscape, which was calculated using the temperature and salinity fields produced by an ocean data assimilation model. Individuals that were collected in the northern and southern areas hatched and stayed in the southern areas (west offshore of Kyushu) until late June, and thereafter, they can be distinguished into two groups: one that migrated northward at shallow layer and one that stayed around the southern area in the deep layer. A comparison of somatic growth trajectories of the two groups, which was reconstructed based on otolith microstructure analysis, suggested that individuals that migrated northward had significantly larger body lengths in late June than those that stayed in the southern area. These results indicate that young-of-the-year Japanese sardines that hatched in the southern area may have been forced to choose one of two strategies to avoid extremely high water temperatures within seasonal and geographical limits. These include migrating northward or moving to deeper layers. Our results indicate that the environmental variabilities in the southern area could critically impact sardine population dynamics in the Sea of Japan.

Triple-objective optimization using ANN+NSGA-II for an innovative biomass gasification-heat recovery process, producing electricity, coolant, and liquefied hydrogen

A novel thermal integration approach is introduced for a biomass-driven gas turbine power plant that generates electricity, coolant, and liquefied hydrogen. The designed scheme encompassed an organic flash cycle, a bi-evaporator ejector refrigeration unit, a high-temperature water electrolyzer for hydrogen production, a multi-effect desalination cycle for supplying water for electrolysis process, and a Claude cycle for hydrogen gas liquefaction. The designed system's importance comes back to using biomass feedstock as the input fuel and utilizing the hydrogen liquefaction method. In addition to the possibility of deploying the system in remote areas, it provides the opportunity for hydrogen storage in a smaller volume for more accessible storage and transportation. On the other hand, using a comparative method for selecting an environmentally friendly fluid for the heat recovery subsystem is another crucial aspect of the present study from the environmental aspect. It is found that R161 is the appropriate choice among the seven studied working fluids. Subsequently, a comprehensive evaluation of the entire system's thermodynamic and environmental aspects is performed using an intelligent process. By considering energy and exergy efficiencies along with CO2 emissions as the objective functions, a thorough sensitivity analysis and a triple-objective optimization are carried out. Hence, artificial neural networks for the objectives are developed and integrated into the NSGA-II optimization method. Employing LINMAP decision-making, the values of objective are attained, exhibiting 39.6 % for energy efficiency, 36.1 % for exergy efficiency, and 631.7 kg/MWh for CO2 emissions. Considering the optimum solution, the proposed system is capable of producing electricity, cooling, and liquefied hydrogen with capacities of 4526 kW, 1875 kW, and 21.22 m3/day, respectively. Additionally, the scenario yields an exergoenvironmental index of 0.579 and an exergetic stability index of 0.61. and a liquefied hydrogen generation rate of 21.22 m3/day.

Design of Pelton Turbine Test Stand in Plateau Environment

Abstract In recent years, with the continuous development of China’s hydropower projects, Pelton turbines are gradually being valued, and the focus of development has shifted from plain areas to plateau areas. Environmental impacts such as high altitude, water temperature, and high sediment content in the plateau area have caused serious interference to equipment that originally worked in a stable environment, for example, the failure of the cooperation between the parts of the turbine and the mutual seizure, the increased wear of the nozzle needle, the decrease of the flow rate and the water outlet speed of the nozzle, and the decrease of the air pressure in the plateau environment lead to the change of the flow state of the nozzle. In view of the above problems, this paper puts forward the design scheme of impulse turbine test-bed, using the method of changing specific speed to determine the basic parameters of impulse turbine unit, so as to eliminate the influence of plateau environment on the normal operation of turbine, obtain the efficiency condition of model experiment under low ambient pressure, and improve the operation efficiency and reliability of turbine unit.

Interfacial multilayer self-assembly of protein and polysaccharides: Ultrasonic regulation, stability and application in delivery lutein

In this study, the layer-by-layer adsorption behavior of sodium caseinate, pectin, and chitosan on the oil-water interface was illustrated using multi-frequency ultrasound. We investigated the impact of ultrasound on various factors, such as particle size, zeta potential, and interfacial protein/polysaccharide concentration. It was observed that ultrasound has significantly decreased droplet size and increased the surface area at the interface, hence promoting the adsorption of protein/polysaccharide. In the sonicated multilayer emulsion, the concentrations of interface proteins, pectin, and chitosan increased to 84.82 %, 90.49 %, and 83.31 %, respectively. The findings of the study indicated that the application of ultrasonic treatment had a significant impact on the emulsion's surface charge and the prevention of droplet aggregation. As a result, the stability of the emulsion system, including its resistance to salt, temperature, and storage conditions, has been significantly improved. Moreover, the emulsion showed an increase in the retention rate of lutein by 21.88 % after a high-temperature water bath and by 19.35 % after UV irradiation. Certainly, the multilayer emulsion treated with ultrasound demonstrated a superior and prolonged releasing behavior. These findings demonstrated the suitability of the ultrasound treatment for the preparation of emulsions to deliver bioactive compounds.

Impact of myristic acid on novel designed manifold assimilated with domestic solar water heater: An experimental approach

In this study, myristic acid as heat storage material was assimilated with a novel designed manifold of evacuated tube solar collector (EVTSC). The foremost advantage of this design is that the integration of myristic acid in the manifold does not affect the vacuum tube’s strength and does not occupy extra roof space. Also, the advantageous thermal and chemical properties of myristic acid improve the performance of the system. The proposed system was tested for two different charging operations of storage material i.e. half-day charging operation and whole-day charging operation for water flow of 0.066, 0.133, and 0.20 LPM (liter per minute). These charging operations were selected to optimize the performance of the proposed system for daytime and nighttime hot water demand. The heat transfer analysis of the proposed system during both charging operations is also determined and compared. In addition to this, the machine learning approach is used to predict the hot water temperature. Concerning experimental results, the daily efficiency during HD-CHO is almost 62.42 %, 69.17 %, and 79.12 % respectively for the water flow of 0.066, 0.133, and 0.20 LPM. Whereas, during WD-CHO, daily efficiency was approximately 71.49 %, 80.42 %, and 85.21 % respectively for corresponding flow rates. Furthermore, the daily efficiency of the proposed system during HD-CHO and WD-CHO is found to be 42.85 % and 61 % higher than conventional systems. The higher and lower flow rates during both charging operations are recommended in terms of high daily efficiency and high hot water temperature respectively. Hence, the proposed system is designed to improve thermal performance, fulfill the hot water demand during late evening time, and decrease the overheating concern as compared to the conventional one.

Non-uniform boiling heat transfer characteristics and calculation evaluation in U-tube steam generator tube bundle

U-tube steam generator, as one of the core equipment in nuclear power plants, has lateral non-uniform heating on the secondary side, which complicates the progress of heat transfer on the secondary side of the evaporator by causing fluid cross mixing. However, there is relatively little research on the properties of transverse non-uniform heat transfer in the secondary side tube bundle of the evaporator under natural circulation conditions with the free liquid surface. Therefore, to conduct comparative experiments and studies between uniform and non-uniform heating, an experimental setup with the natural circulation of the free liquid surface and the ability of transverse non-uniform heating was constructed, considering the characteristics mentioned above for the secondary side of the evaporator. The results indicate that higher proportions of gas-phase distribution are frequently found in the tube bundle on the high-power side, and corresponding positions usually have higher water temperature, heat transfer capacity, and heat transfer coefficient. Besides, four heat transfer correlations that are suitable for pool boiling are estimated, and the results show that the Rohsenow correlation has the best applicability to compute the heat transfer coefficient for uniform heating experiments while performing worse in non-uniform heating experiments. The main reason is the lack of consideration for the factors of fluid cross mixing in traditional correlations.

How the fertility of males and females is affected by stress, lifestyle and pharmaceutical agents

Background: Infertility in men is the most discussed issue among couples. It is generally believed that about half of infertility in couples is due to the men side, mainly due to frustrations in the process of spermatogenesis. Currently it has been found that lifestyle modifications are vital to improve infertility and interest in this area has increased. Examples include maturation, mental stress, diet, active work, high temperature of scrotum, hot water, caffeine, and mobile phone use. This review will examine the effects of personal satisfaction (a modifiable lifestyle factor) and mental stress on infertility in male. It will also show the effects of high scrotal temperature and unhealthy views of exercise on infertility in male. Materials and Methods: Forty of the 118 (34%) men patients who underwent IVF agreed to participate in this review. Only patients having IVF for the first time were recalled for re-examination to reduce the adjustments to the sperms sample screening process that would occur in men with some experience of IVF. Of these, 31 completed the retest and eight decided not to proceed after the initial testing period; one patient's cycle was cancelled prior to ovulation. Conclusion: Our study found that IVF patients had significantly lower sperm quality when they collected their eggs, which suggests a link between sperm quality and psychological stress. Whether physical (frozen reserve sperm samples) or psychological (evacuation preparation, targeted morphology, treatment groups) interventions are effective in reducing stress in male IVF patients and controlling stress-related changes in sperm quality is still unknown. Further studies are awaited to light some further developments.

Compound database for gaseous metal hydroxides and oxyhydroxides

In this study computational methods are used to derive thermochemical data for Sc, Fe, Co, Ni, and Hf hydroxides and oxyhydroxides. As done previously, molecular geometries and vibrational modes were derived with DFT methods; for the enthalpies of formation more computationally intensive coupled cluster methods were necessary. For each species ΔfHo(298), So(298), and Cp in the form A + BT + CT2 + D/T + E/T2 with A, B, C, D, and E fitted constants are presented. These are combined with previously reported calculations for Al, Cr, Si, Ta, Al, Zr, Y, Yb, Gd, and Mn to build a compound database for metal hydroxides and oxyhydroxides. Sample calculations for applications where high temperature water vapor is encountered are shown. The majority of the database was generated from ab initio calculations; however, experiments were critical benchmarks for many of the species.

Experimental study on performance and compressor characteristics of transcritical CO2 heat pump system

The accelerated advancement of the economy has led to a heightened focus on the issue of energy conservation and reduced consumption within heat pump systems. An experimental investigation was conducted to analyze the impact of discharge pressure and outlet water temperature on the performance of the transcritical CO2 single-stage heat pump system and vapor injection heat pump system. The experimental results show that the heating capacity first increases and then tends to be constant or even slightly decreases with the increase of discharge pressure in single-stage heat pump system. When subjected to the same operating conditions, the coefficient of performance of vapor injection heat pump system exceeds that of single-stage heat pump system. Compared with single-stage heat pump system, the performance coefficient of vapor injection heat pump system has increased by an average of 6.21% and the heating capacity has increased by an average of 9.54%. Additionally, the volumetric efficiency of the compressor substantially decreases when producing high-temperature hot water. Semi-empirical models for evaluating the compressor performance in both single-stage heat pump system and vapor injection pump system are established through the parameterization of the volumetric efficiency with respect to the pressure ratio and compressor speed. These models effectively forecast compressor performance.

Investigation on the Preparation and Performances of Epoxy-Modified Asphalt Binder and Its Mixtures.

Epoxy-modified asphalt binder has been widely used in steel deck pavement due to its excellent properties and it is a potential candidate for long life pavements. However, its short reserve time limits its widespread application in pavement engineering. Therefore, this work developed a novel epoxy-modified asphalt binder composed of a laboratory-made curing agent as a solution. Firstly, optimization of preparation temperature of this new material was studied to balance the requirements of enough construction time and the material strength and elongation. The epoxy-modified asphalt binder, prepared at the optimal temperature of 140 °C, had a reserve time exceeding 120 min, whereas the tensile strength and the elongation at failure were 2.22 MPa and 216%, respectively, which satisfied the standard requirements of paving epoxy material well. Secondly, the asphalt mixture property tests demonstrate excellent high-temperature rutting resistance, water stability and low-temperature anti-cracking ability. Additionally, the compatibility and colloidal stability of this epoxy-modified asphalt binder were analyzed in terms of microphase structure. The uniform microphase distribution of this binder showed by the laser confocal microscope observation in both short-term aging case and long-term aging case, indicates the great compatibility between asphalt and epoxy resin during paving process and service life. Furthermore, fatigue tests were conducted to evaluate the long-term durability. The fatigue life of epoxy-modified asphalt mixtures increased by 435%, 427%, 342%, and 276% under the stress ratios of 0.3, 0.4, 0.5, and 0.6, respectively, compared to those of SBS-modified asphalt mixtures. All these results indicate that the new epoxy-modified asphalt material is promising for applications in pavement engineering, especially suitable for long-life road pavement.

Corrosion of 316L stainless steel in high temperature water and steam: Mechanisms of corrosion

316L stainless steel was exposed to 320 °C hydrogenated or aerated water and 480 °C steam for up to 72 h to determine the aqueous corrosion mechanisms. The thermodynamics of the corrosion process are interpreted using a new concept called the excess volume which predicts stable formation of pores in the inner oxide layer. Corrosion rates are found to be correlated with inner oxide porosity. Inner oxide thicknesses were measured, and thermodynamic modelling was used to determine that the rate-limiting step of corrosion is fluid transport of oxygen via pores in the inner oxide layer.

Spatio-temporal variation of mesozooplankton in the northern coastal waters of Bay of Bengal

Mesozooplankton (MSP) are significant primary and secondary consumers in aquatic ecosystems that influence biogeochemical cycles and are considered important bioindicators of ecosystem functioning. Data on the spatio-temporal variability of the MSP population from the estuarine and coastal waters of northwestern Bay of Bengal (BoB) is scarce. The present study is the first detailed investigation on the spatio-temporal dynamics of MSP along the estuarine and coastal waters of northwestern BoB from two contrasting seasons over a period of three years based on univariate and multivariate statistical analyses. The crucial drivers for spatio-temporal variability in the MSP community were water temperature, salinity, dissolved oxygen (DO) concentration, nutrient (nitrate, phosphate, silicate) concentrations, and Chlorophyll (Chl) a concentration. The highest mean MSP abundance was obtained during summer monsoon (SM). The results of this study state that there is a significant seasonal difference in the hydrographical parameters that change the community dynamics of MSP inhabiting the estuarine and coastal waters of BoB. The MSP species assemblages during winter monsoon (WM) were governed by high salinity and DO levels while those during SM were associated with high water temperature, nutrients, and Chl a concentration. A clear seasonal shift from the gelatinous community in WM to the crustacean community in SM was documented. A total of 172 MSP species were identified during WM, and 200 MSP species during SM, with 37 species being exclusively detected during WM and 65 species being exclusively recorded during SM. The most abundant species during WM were Chrysaora caliparea, Cyanea nozakii, Sagitta bipunctata, Pleurobrachia pileus, and Acromitus flagellatus to name a few and those during SM consisted of Undinula vulgaris, Acartia (Odontacartia) spinicauda, Oithona simplex, Oithona similis, and Oncaea venusta. Copepoda was the most dominant taxa during all sampling seasons, while ichthyoplankton and meroplankton fauna were low during WM and comparatively higher during SM, indicating the top-down control of their population by gelatinous taxa. Biodiversity indices reflected well to excellent diversity patterns of MSP. In the current scenario of global warming and climate change, our research highlights the need for comprehensive long-term monitoring of estuarine and coastal waters of western BoB, which harbour a rich marine faunal diversity, to identify the bioindicators of seasonal variability among major MSP groups.

Investigating the effects of synthesis parameter on textural and catalytic properties of ZnO–CuO–Al2O3–Cr2O3 mixed oxide in water gas shift reaction

The present study has investigated the influence of preparing conditions, including aging temperature and time, pH, and Tcalcination, on the co-precipitated ZnO–CuO–Al2O3–Cr2O3 mixed oxide at a high-temperature water gas shift reaction. XRD, BET, FTIR, TG-DTA, SEM, TEM, and H2-TPR were used to characterize the relationships between the synthesis parameters and the physicochemical features. The investigation proved that the activity in aging 5 h could be related to higher pore volume and lower crystalline size of 0.24 cm3g-1 and 6.4 nm, respectively. Also found that increasing the aging temperature to 60 °C results in a rise in the surface area and particle size of less than 6 nm, enhancing the catalyst activity. The findings showed that raising the Tcalcination reduced the surface area from 132 to 65 m2 g−1. It has been concluded that the CO conversion of 70 % was obtained when aged at 60 °C and calcination temperature of 400 °C.

Representative High-Temperature Hydrothermal Activities in the Himalaya Geothermal Belt (HGB): A Review and Future Perspectives

Southern Tibet and western Yunnan are areas with an intensive distribution of high-temperature geothermal systems in China, as an important part of the Himalayan Geothermal Belt (HGB). In recent decades, China has conducted systematic research on high-temperature geothermal fields such as Yangbajing, Gudui, and Rehai. However, a comprehensive understanding has not yet been formed. The objective of this study was to enhance comprehension of the high-temperature geothermal system in the HGB and to elucidate the hydrogeochemical characteristics of geothermal fluids. This will facilitate the subsequent sustainable development and exploitation of domestic high-temperature hydrothermal geothermal resources. To this end, this study analysed geothermal spring and borehole data from the Yangbajing, Gudui, and Rehai geothermal fields. Based on previous research results, the source, evolution, and reservoir temperature characteristics of geothermal fluids are compared and summarised. The main high-temperature geothermal water in the geothermal field is derived from the deep Cl-Na geothermal fluid. Yangbajing’s and Gudui’s geothermal waters are primarily recharged by snow-melt water, while Rehai’s geothermal water is mainly recharged by local meteoric water. The average mixing ratios of magmatic water in the Yangbajing, Gudui, and Rehai geothermal fields are 17%, 21%, and 22%, respectively. The Yangbajing and Gudui geothermal fields have a relatively closed geological environment, resulting in a stronger water–rock interaction compared to the Rehai geothermal field. As geothermal water rises, it mixes with shallow cold water infiltration. The mixing ratios of cold water in the Yangbajing, Gudui, and Rehai geothermal fields are 60–70%, 40–50%, and 20–40%, respectively. Based on the solute geothermometer calculations, the maximum geothermal reservoir temperatures for Yangbajing, Gudui, and Rehai are 237 °C, 266 °C, and 282 °C, respectively. This study summarises and compares the hydrogeochemical characteristics of three typical high-temperature geothermal fields. The findings provide an important theoretical basis for the development of high-temperature geothermal resources in the Himalayan Geothermal Belt.