Fluid Temperature Fluctuations Research Articles

Free Vibration of Thermally Loaded FG-GPLRC Nanoplates Integrated with Magneto-Electro-Elastic Layers in Contact with Fluid

This work investigates the free vibrations of innovative thermally loaded nanoplates constructed by integrating magneto-electro-elastic (MEE) layers with functionally-graded graphene platelet-reinforced composite cores (FG-GPLRC) and accounting for viscous fluid interactions. An advanced multiphysics model is developed using the Navier–Stokes equations to capture fluid structure coupling effects, Halpin–Tsai, and the rule of mixtures micromechanics to predict the non-uniform effective properties, third-order shear deformation plates theory (TSDPT) to incorporate thickness stretching, and the nonlocal strain gradient theory (NSGT) to characterize size dependencies. The Galerkin technique is used to solve the governing equations, which are derived from the Hamilton’s principle. Parametric analyses quantify the influences of fluid depth, temperature fluctuations, temperature profiles, nonlocal and strain gradient parameters, electric and magnetic potentials, graphene distribution patterns, graphene weight fractions, and boundary conditions on the vibration response. The outcomes of this study provide design guidelines and predictive tools enabling active vibration control systems for next-generation thermally-loaded nanocomposite structures with widespread applications from aerospace vehicles to nanoelectronics.

Heat Transfer and Pressure Drop in Plate Fin Heat Exchangers: A Numerical Approach

An apparatus for transferring thermal energy across an impermeable barrier between two or more fluids is a heat exchanger. The effective transmission of heat from a hot fluid to a cold fluid is its primary goal. The temperature differential between the two fluids directly affects this heat transfer. Using CFD study with FLUENT 2020 R1, the performance characteristics of the compact plate fin heat exchanger's improved surfaces are examined. The simulation of heat transfer and flow encompassed a variety of velocities including completely turbulent regions. The pressure, temperature, and velocity contours were taken from the Fluent simulations. To determine the heat exchanger's flow and heat transfer performance, numerical analysis has been done. Since boundary conditions are crucial to CFD, they have been carefully chosen. The flow field, heat transfer, thickness, and wavelength were all predicted using the software code for a range of air to water velocities. Three distinct wavelengths of numerical simulations for a plate-fin heat exchanger were used in the study (10, 20, and 30). There were changes to the fin thickness, entry locations, and air and water entry velocities. Solid Works and Ansys were used to create the geometry for the three-level fin models that were placed inside the heat exchanger, both with and without a cover. For determining the heat exchanger's geometry and fin isometry, three levels measuring 19.6 mm in height and 53.64 mm in width were constructed. The fins have a thickness of 0.2 to 0.4 mm. As the air and water velocities vary, so does the temperature inside the heat exchanger. Because the topmost layer is a warm stream's flow channel, the temperature rises there, whereas the opposite effect is seen close to the bottom layer. Convection heat transmission to the surroundings and conduction heat transfer through the heat exchanger's side plates are the causes of fluid temperature fluctuations in the depth direction.

Heat transfer process for penetration flow into a branch pipe causing thermal fatigue at a T-junction

The heat transfer process between a fluid and a wall at a T-junction was investigated for impinged penetration flow in which the hot mainstream flow impinged on the branch pipe wall and penetrated into the branch pipe on the downstream side. The temperature distributions of the fluid near the branch pipe wall and the pipe inner surface were simultaneously measured using thermocouples. The fluid temperature close to the branch pipe wall fluctuated as a result of the hot mainstream flow penetrating into the branch pipe, and these fluctuations caused temperature fluctuations on the pipe inner surface. However, the temperature fluctuation range on the inner surface did not exceed 40% of the range of the fluid temperature fluctuation, because fluctuations were attenuated due to the heat transfer process from fluid to structure. The power spectrum method was used to the heat transfer coefficient on the pipe inner surface. The evaluated heat transfer coefficient was 1.62 times larger than that calculated using the Dittus-Boelter equation. The temperature fluctuation range on the inner surface was successfully estimated by leveraging the derived heat transfer coefficient and the measured fluid temperature.

An NEA/OECD benchmark-experiment for the validation of CFD for mixing and thermal fatigue in T-junction dead leg flows

The current screening criteria for thermal fatigue used in isolated branch lines at nuclear power plants are based on simplified approaches, which, on one hand, tend to be overly conservative, and on the other hand, appear to miss important physics. This is demonstrated by the fact that a number of affected pipes were missed by the current screening methods.The purpose of the present work is to produce novel and accurate experimental data, which can be used for a benchmark of Computational Fluid Dynamics (CFD) in order to advance the prediction capabilities of thermal mixing and fatigue in dead leg T-junctions and improve the accuracy of the screening criteria. The ultimate value creation is increased safety and availability at nuclear power plants. This is of great interest and utmost importance to the nuclear reactor safety community.A new pressurized experimental setup of a T-junction has been designed and constructed for the purpose. The experimental setup, with a temperature difference of 120 °C, more closely resembles plant conditions than in earlier experiments. The boundary conditions in terms of the flowrates and temperatures are controlled and stable within their measurement uncertainty – a prerequisite for CFD-grade experiments.The novelty of the present work is measurements of the temperature fluctuations both in the near wall fluid mixing region and throughout the solid pipe wall material.It has been shown that the interaction between the swirl penetration of hot water and the stratified layer in the cold dead leg has an intermittent character and that random clusters of bursts of hot water penetrate into the stratification and the stagnant cold water below. The average time scale of this process is of the order of hundreds of seconds.The stratification between the hot and the cold water in the dead leg has also shown to have a low frequency oscillation of the order of 0.1 Hz, which wiggles in the circumferential direction. After hot water has penetrated downward and excited the instability, the temperature falls back to the initial one in a manner similar to a damped oscillation.The vertical temperature profiles have shown to be self-similar, for moderate temperatures, when scaled with the temperature difference between the hot and the cold water and with the penetration length.The penetration length increases with the velocity in the hot leg confirming earlier reported correlations.A small (less than 0.1 % of the hot main flow) cold leakage flow into the T-junction is sufficient to suppress the swirl penetration and substantially reduces the penetration length. However, the temperature fluctuations have a larger amplitude and range across the whole mixing zone. The fluid temperature fluctuations are shifted towards a more high frequency content, however, the low frequency nature of the swirl penetration is still present.The obtained novel dataset will be provided for a blind CFD benchmark exercise as part of an OECD/NEA project in 2023 and 2024.

Modeling and experimental analysis of high-efficiency fluid temperature fluctuation attenuator based on phase regulator

Temperature fluctuation attenuators are important passive components for disturbance rejection in precise temperature control system, but previous attenuator researches mainly focused on increasing effective heat capacity to achieve better attenuation. In this paper, the temperature phase regulator (TPR) model is proposed as a superior method to reduce fluid temperature disturbances with less capacity. It achieves output temperature fluctuation attenuation by shifting the phase of the delay side temperature signal and mixing it with the normal side. Similar to the principle that notch filters can highly attenuate signals in specific frequency bands, we constructed TPR theoretical models under equal flow ratios and non-equal flow ratios. Different bandwidths, attenuation depths and target center frequencies can be achieved by changing the two parameters of equivalent heat capacity and flow ratio, and the mechanism of parameters affecting the TPR amplitude-frequency characteristics was analyzed. In terms of effect evaluation, we verified the correlation between the frequency domain and the time domain data, and compared the TPR with the thermal capacity attenuator and other popular attenuators in terms of MSE, MAE and Max-min of temperature data. In a typical temperature attenuation test, TPR can achieve 40% and 35% of MAE and Max-min value attenuation rates, which are exceeding the ideal upper limit of other attenuators and far superior to typical attenuators. The experimental data confirmed the feasibility of the heat capacity of the pipe to support the TPR delay side as a pure delay. The experimental results of non-equal flow ratios verified the model reference-ability of changing flow ratio. In the equal flow ratio test, the fit of the actual data curve and the theoretical curve showed the accuracy of the theoretical model, and the MAE attenuation ratio better than 70% reflected the excellent attenuation performance.

Natural convection laminar flow between two vertical walls with a nonlinear variation of density and viscosity with temperature

AbstractUnder the combined influence of buoyancy force and constant pressure gradient, the free convection flow and heat transmission inside a channel placed vertically and consisting of two parallel walls are examined. Through the application of the Runge–Kutta fourth‐order approach and the shooting procedure, the modeled equations of the problem including nonlinear density–temperature and quadratic viscosity–temperature change at constant but different wall temperatures are numerically solved. For distinct values of the embedded parameters, the fluctuations in fluid's velocity and temperature are examined. For various situations of linear, quadratic, and nonlinear dependence of density on temperature, numerical values for heat transmission rate, volume flow rate and skin friction are determined and tabulated. The fluctuations of the Nusselt number with the Grashof number corresponding to thermal expansion coefficients are depicted through graphical interpretations. It was found that the combined effect of thermal expansion coefficients raises the values of the physical entities, Nusselt number, volume flow rate, and heat transmission rate. For the lower Reynolds number values, the Nusselt number value stays around one, indicating the same impact of conduction and convection on heat transmission.

Investigating the effect of obstacle presence on argon fluid flow characteristics in rough nanochannels using molecular dynamics method

This study investigates the molecular dynamics behavior of argon Poiseuille flow in copper nanochannels with two-dimensional geometry (with two solid walls) and three-dimensional geometry (with four solid walls) utilizing the LAMMPS software. This study explores the combined existence of obstacles on the surface (with index R) and in the regions above the surface of the nanochannel wall (with index P) at varying numbers, along with applying an external force in the flow direction. The aim is to examine the velocity, density, and temperature fields, as well as the heat flux and thermal conductivity coefficient for 10,000 time steps, using the hybrid Lennard-Jones Embedded Atom Method (EAM) potential function. The findings of this study suggest that alterations in wall and fluid temperature, the impact of wall force, and the existence of obstacles have noteworthy impacts on flow parameter behavior. The fluctuations in fluid temperature, density, velocity, and thermal conductivity coefficient are influenced by modifications in the kinetic behavior of flowing atoms resulting from the collision and atomic diffusion mechanism. The number density of argon atoms displays relatively intense fluctuations when obstacles are present near the nanochannel walls. However, the fluctuations are comparatively lower compared to the case without obstacles. Conversely, placing an obstacle inside an ideal nanochannel reduces the amplitude of fluid atoms' motion fluctuations in the proximity of the walls. Compared to a smooth nanochannel, the maximum heat transfer reaches 72 percent, which occurs with an increase in the number of obstacles in the nanochannel. In conclusion, the presence of P-structured obstacles in the two-dimensional nanochannel leads to a 2.8-fold surge in the thermal conductivity coefficient compared to a smooth nanochannel of the external force.

Improving mining development modelling based on the thermal methods

Introduction. The problem of oil recovery growth and oil reserves management improvement in active oil fields is growing annually. It is possible to increase oil recovery and improve oil reserves management by introducing the thermal methods of oil production. This method was applied at the Yarega oil field. The thermal mining development technology is currently being implemented at the Yarega territory on an industrial scale. Lyael territory is developed by SAGD technology. Heat capacity and thermal conductivity are crucial characteristics of rocks. Reference books and databases lack reliable data on sedimentary rocks thermal properties. The traditional experimental base of thermal petrophysics cannot provide representative information on the thermal properties of rocks, considering rock heterogeneity and anisotropy, various fluid saturation, and pressure and temperature fluctuations. Results. According to special petrophysical studies of the Yarega highly viscous oil field core, ambiguity has been revealed in the thermal properties of rocks, including anisotropy, heat capacity and thermal conductivity. When applying laboratory results in modeling, divergence in oil production and cumulative steam oil ratio can reach 60%. Main ambiguity arising in the course of thermal mine development modeling has been identified. The ambiguity is associated with the account of production for a well, a large number of underground wells, and low reservoir pressure (lower than atmospheric pressure). These problems are successfully solved by specialists of the Yarega field, who maintain highly viscous oil development. At low reservoir pressures, the simulator encounters errors on low pressure values during well operation. Conclusions. At the Yarega field, permanent geological and technological model is currently actively being implemented. It is aimed at solving technological problems of ambiguity in the development of highly viscous oil by thermal methods using advanced software.

Numerical analysis of temperature fluctuation characteristics associated with thermal striping phenomena in the PGSFR

Thermal striping is a complex thermal–hydraulic phenomenon caused by fluid temperature fluctuations that can also cause high-cycle thermal fatigue to the structural wall of sodium-cooled fast reactors (SFRs). Numerical simulations using large-eddy simulation (LES) were performed to predict and evaluate the characteristics of the temperature fluctuations related to thermal striping in the upper internal structure (UIS) of the prototype generation-IV sodium-cooled fast reactor (PGSFR). Specific monitoring points were established for the fluid region near the control rod driving mechanism (CRDM) guide tubes, CRDM guide tube walls, and UIS support plates, and the normalized mean and fluctuating temperatures were investigated at these points. It was found that the location of the maximum amplitude of the temperature fluctuations in the UIS was the lowest end of the inner wall of the CRDM guide tube, and the maximum value of the normalized fluctuating temperatures was 17.2%. The frequency of the maximum temperature fluctuation on the CRDM guide tube walls, which is an important factor in thermal striping, was also analyzed using the fast Fourier transform analysis. These results can be used for the structural integrity evaluation of the UIS in SFR.

Microfluidic manipulation by spiral hollow-fibre actuators

A microfluidic manipulation system that can sense a liquid and control its flow is highly desirable. However, conventional sensors and motors have difficulty fitting the limited space in microfluidic devices; moreover, fast sensing and actuation are required because of the fast liquid flow in the hollow fibre. In this study, fast torsional and tensile actuators were developed using hollow fibres employing spiral nonlinear stress, which can sense the fluid temperature and sort the fluid into the desired vessels. The fluid-driven actuation exhibited a highly increased response speed (27 times as fast as that of air-driven actuation) and increased power density (90 times that of an air-driven solid fibre actuator). A 0.5 K fluid temperature fluctuation produced a 20° rotation of the hollow fibre. These high performances originated from increments in both heat transfer and the average bias angle, which was understood through theoretical analysis. This work provides a new design strategy for intelligent microfluidics and inspiration for soft robots and smart devices for biological, optical, or magnetic applications.

Modulation of fluid temperature fluctuations by particles in turbulence

Modulation of fluid temperature fluctuations by particles due to thermal interaction in homogeneous isotropic turbulence is studied. For simplicity, only thermal coupling between the fluid and particles is considered, and momentum coupling is neglected. Application of the statistical theory used in cloud turbulence research leads to the prediction that modulation of the intensity of fluid temperature fluctuations by particles is expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the fluid thermal relaxation time. Direct numerical simulations are conducted for two-way thermal coupling between the fluid temperature field and point particles in homogeneous isotropic turbulence. The simulation results are shown to agree well with the theoretical predictions.

Fatigue Life Assessment for Variable Strain in a Mixing Tee by Use of Effective Strain Range

Abstract Mixing flow causes fluctuations in fluid temperature near a pipe wall and may result in fatigue crack initiation. Movement of the hot spot, at which the pipe inner surface was heated by hot flow from the branch pipe, causes thermal stress fluctuations. In this study, the effect of the loading sequence on thermal fatigue in a mixing tee was investigated. In addition, the prediction method of the fatigue life for the variable thermal strain in the mixing tee was discussed. The time histories of the strain around the hot spot were estimated by finite element analysis for which the temperature condition was determined by wall temperature measured in a mockup test. The accumulated fatigue damage around the hot spot obtained by Miner's rule was less than 1.0. Since the strain around the hot spot had waveforms with periodic overload, the loading sequence with periodic overload caused reduction of the fatigue life around the hot spot. Crack growth tests showed that a single overload decreased crack opening strain and increased the effective strain range. The increment of the effective strain range accelerated the crack growth rate after the overload. The accumulated fatigue damage for the strain in the mixing tee was calculated using Miner's rule and the strain ranges, which added the maximum increment of the effective strain range. The accumulated fatigue damage was larger than 1.0 under most conditions. The proposed procedure is suitable to predict the conservative fatigue life in a mixing tee.

Thermocline vs. two‐tank direct thermal storage system for concentrating solar power plants: A comparative techno‐economic assessment

This paper concerns the ongoing studies on a Concentrated Solar Power (CSP) plant in operation in Ottana (Italy), comprising a 629 kW organic Rankine cycle (ORC) unit fed by a linear Fresnel solar field. Hexamethyldisiloxane (MM) and “Therminol SP-I” are used respectively as ORC working fluid and heat transfer fluid in the solar receivers. A two-tank direct Thermal Energy Storage (TES) system is currently integrated in the CSP plant, serving as a direct interface between solar field and ORC. With the view of improving the solar facility, two alternative TES configurations were proposed in this study: a one-tank packed-bed TES system using silica as solid storage media and another similar one including encapsulated phase-change material (molten salt). Comprehensive mathematical models were developed for simulating daily behaviour as well as for assessing yearly performance of the various TES technologies. Furthermore, a preliminary economic analysis was carried out. Results showed poorer response of the one-tank TES system to large fluctuations in the ORC inlet fluid temperature, leading to reduction in the mean ORC efficiency (18.2% as against 19.7% obtained with the two-tank TES). Conversely, higher energy storage density and lower thermal losses were obtained adopting the one-tank TES, resulting in about 5% more annual solar energy yield. Invariably, equivalent annual ORC energy production of 0.92 GWh/year was obtained for the three TES configurations. Additionally, adopting a one-tank TES system meant that the purchase costs of a second tank and its storage medium (thermal oil) could be saved, resulting in investment costs about 45% lower and, ultimately, levelized cost of storage about 48% lower than what obtains in the two-tank TES system.

Heat transfer coefficient suitable for thermal fatigue assessment at a T-junction

Thermal fatigue cracks have been found at T-junctions where high and low temperature fluids flow in. In this study, the heat transfer coefficient at a T-junction was investigated. The obtained heat transfer coefficient was then validated by estimating the temperatures on a pipe inner surface. The temperatures of the fluid and the pipe inner surface were measured by mock-up tests in which high and low temperature water was mixed. The fluid temperature fluctuation near the boundary between the hot jet flow and the cold main flow caused the temperature on the pipe inner surface to fluctuate. The heat transfer coefficient was obtained by the power spectrum method for the pipe inner surface where the temperature fluctuation was relatively large. The estimated heat transfer coefficient was 3.3 times larger than that calculated by the Dittus-Boelter equation. The temperature on the pipe inner surface was successfully estimated using the obtained heat transfer coefficient and the measured fluid temperature in the vicinity of the inner surface. The prediction error was less than ±20% for the temperature fluctuation range.

Trace element chemistry of hydrothermal quartz and its genetic significance: A case study from the Xikuangshan and Woxi giant Sb deposits in southern China

Trace element concentration and distribution in hydrothermal quartz from the giant Xikuangshan and Woxi Sb deposits in southern China have been investigated in order to discuss the trace element differences between Sb deposits and shed new insights into their genetic processes. The LA-ICP-MS data reveal that Al, Sb, Li, Na, and K are the most important elements in quartz with concentrations of >10 ppm, which may primarily occur as solid solution within the crystal lattice in quartz, and are probably controlled by the coupled substitution of (Al3+, Sb3+) + (Li+, Na+, K+) ↔ Si4+. However, the significant differences in trace element composition are suggestive of different precipitation mechanism of hydrothermal quartz at two giant Sb deposit. The higher and relatively homogenous Al concentrations suggest that quartz from the Xikuangshan deposit may have precipitated from more acidic fluids at presumably relative stable pH compared to the Woxi deposit. In contrast, the lower but variable Al concentration in quartz at Woxi is suggestive of a less acidic fluid with significant fluid pH fluctuations that may have driven metal-sulfide precipitation from ore fluids. Moreover, the higher and relatively variable Ti and Ge concentrations in quartz at Woxi are indicative of a higher and dramatic change of fluid temperature during precipitation processes; whereas quartz at Xikuangshan has lower and homogeneous Ti and Ge concentrations, reflecting smaller temperature fluctuations during quartz formation. Additionally, the quartz from the Xikuangshan deposit contains higher Li, Na, K, and Ca concentrations compared to that of the Woxi deposit, suggesting that the quartz-precipitating fluids at Xikuangshan are more enriched in alkali metals. The significant difference in trace element composition of hydrothermal quartz is good evidence for different precipitation mechanisms for two giant Sb deposits: quartz precipitation at Woxi deposit may have resulted from fluid mixing that would lead to dramatic changes of the fluid pH and temperature; whereas fluid boiling is likely the primary mechanism of quartz and sulfide-metal precipitation at Xikuangshan, which caused a smaller fluctuation of fluid temperature during quartz precipitation, and the stable fluid pH was buffered by interaction of boiling ore fluids with wall-rock carbonates.

CFD study of heat transfer in Stirling engine regenerator

A three dimensional rhombic-drive beta-type Stirling engine is computationally studied with the utilization of ANSYS Fluent software. Research is mainly focused on the characteristics of heat transfer between the working fluid and the regenerator matrix. The regenerator is divided in several sections. The variation of gas and matrix temperature, as well as heat transfer during one cycle of the engine are presented and discussed. The fluctuation of fluid temperature is higher than that of the matrix, while fluid and matrix temperatures in each section are almost equal at the respective instances of flow reversal. Moreover, Nusselt number increases with Reynolds number by a linear trend. The derived correlation for Nusselt number is representative of the total engine cycle.Working gas and metal matrix temperature profile is linear in the biggest part of the regenerator, while at the regenerator ends it is approximated by a 2nd order polynomial equation. The spatial and temporal variation of temperature, as well as the heat transferred between gas and matrix is well approximated by derived equations that incorporate time and length as independent variables and can calculate the value of the studied quantities at a given time instance and a location in the regenerator. These findings can be used as input in a simple analytical model for the specific engine and improve the model outcomes.

Cladding design on lower head of the central measuring shroud in a fast reactor against thermal striping

The central measuring shroud in a fast reactor has the function to support the in-vessel measuring equipment and control rods. It is necessary to keep its integrity for safe operation of the reactor. Since the lower head of central measuring shroud (LHCMS) is located above the core outlet, it bears thermal striping caused by mixture of cold and hot coolant flowing out of the core channels. Thermal striping is one of the factors to cause initial crack or even damage of the LHCMS. As it is a common phenomenon in thermal engineering, it has been studied by many researchers. In order to protect the LHCMS, it is necessary to determine the moderate thickness of cladding. In this process, they usually need to calculate the fluid temperature fluctuations or structural stress by numerical simulation. However, this process may occupy a lot of computing resources. A simplified procedure is expected to achieve rapid calculation of thermal striping fatigue and to ensure a conservative result.In the paper, a simplified procedure is proposed to assess thermal striping fatigue of the LHCMS, in which heat transfer equation, frequency response function and stress are evaluated with some simplified formulas. If temperature fluctuation curve is given, the surface’s temperature, von Mises stress and fatigue damage factors of the LHCMS can be obtained by the procedure. Meanwhile, FEM models for LHCMS without cladding and LHCMS with cladding are established respectively to calculate temperature and stress of the LHCMS. By comparing the computational results of the simplified procedure and those obtained by FEM, it is found that the deviation factors are both around 0.1, which indicates the fatigue assessment procedure can quickly and conservatively obtain fatigue damage factors of different cladding thicknesses. Therefore, it can quickly and conservatively design for the LHCMS when properly programmed.Using the simplified procedure, we analyzed the fatigue damage factors of the LHCMS in a fast reactor. It is shown that during the designed life period of 45 years the LHCMS without cladding will fail, while its integrity can be ensured if the cladding is added with the thickness of 1 mm.

Piezoelectrically excited MEMS sensor with integrated planar coil for the detection of ferrous particles in liquids

We present a novel MEMS sensor which allows the detection of ferrous particles in liquid environments. The device is based on a resonantly excited silicon microcantilever with an integrated planar coil on its surface, which attracts and accumulates ferrous particles on the sensor viamagnetophoresis. The additional mass leads to a shift in resonance frequency of the microcantilever, which in turn can be used to deduce the accumulated particle mass. A reference microcantilever of the same design, which does not actively accumulate particles, is operated in close vicinity to cancel out any parasitic environmental influences, such as fluid temperature fluctuations on the viscosity. The sensor performance is determined by measuring the sensor response to 250 nm iron oxide (Fe3O4) particles, dispersed in deionized water. After a measurement duration of 100 min., a differential resonance frequency shift of 5916 Hz is found, which corresponds to a total accumulated mass of approximately 0.49 μg and a mass responsivity of 82.85 pg/Hz. Based on this result, the detection limit for the sensor in the current design is derived to about 4 ng. Besides its compact and robust architecture, these results promise the successful operation in a broad range of industrial applications, such as predictive maintenance in lubricated machinery.

Comparison of fluid processes in coexisting wolframite and quartz from a giant vein-type tungsten deposit, South China: Insights from detailed petrography and LA-ICP-MS analysis of fluid inclusions

Abstract Granite-related wolframite-quartz veins are the world's most important tungsten mineralization and production resource. Recent progress in revealing their hydrothermal processes has been greatly facilitated by the use of infrared microscopy and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis of both quartz- and wolframite-hosted fluid inclusions. However, owing to the paucity of detailed petrography, previous fluid inclusion studies on coexisting wolframite and quartz are associated with a certain degree of ambiguity. To better understand the fluid processes forming these two minerals, free-grown crystals of intergrown wolframite and quartz from the giant Yaogangxian W deposit in South China were studied using integrated in situ analytical methods including cathodoluminescence (CL) imaging, infrared microthermometry, Raman microspectroscopy, and fluid inclusion LA-ICP-MS analysis. Detailed crystal-scale petrography with critical help from CL imaging shows repetition of quartz, wolframite, and muscovite in the depositional sequence, which comprises a paragenesis far more complex than previous comparable studies. The reconstruction of fluid history in coexisting wolframite and quartz recognizes at least four successive fluid inclusion generations, two of which were entrapped concurrently with wolframite deposition. Fluctuations of fluid temperature and salinity during precipitation of coexisting wolframite and quartz are reflected by our microthermometry results, according to which wolframite-hosted fluid inclusions do not display higher homogenization temperature or salinity than those in quartz. However, LA-ICP-MS analysis shows that both primary fluid inclusions in wolframite and quartz-hosted fluid inclusions associated intimately with wolframite deposition are characterized by strong enrichment in Sr and depletion in B and As compared to quartz-hosted fluid inclusions that are not associated with wolframite deposition. The chemical similarity between the two fluid inclusion generations associated with wolframite deposition implies episodic tungsten mineralization derived from fluids exhibiting distinct chemical signatures. Multiple chemical criteria including incompatible elements and Br/Cl ratios of fluid inclusions in both minerals suggest a magmatic-sourced fluid with the possible addition of sedimentary and meteoric water. Combined with microthermometry and Raman results, fluid chemical evolution in terms of B, As, S, Sr, W, Mn, Fe, and carbonic volatiles collectively imply fluid phase separation and mixing with sedimentary fluid may have played important roles in wolframite deposition, whereas fluid cooling and addition of Fe and Mn do not appear to be the major driving factor. This study also shows that fluid inclusions in both wolframite and coexisting quartz may contain a substantial amount of carbonic volatiles (CO2 ± CH4) and H3BO3. Ignoring the occurrence of these components can result in significant overestimation of apparent salinity and miscalculation of LA-ICP-MS elemental concentrations. We suggest that these effects should be considered critically to avoid misinterpretation of fluid inclusion data, especially for granite-related tungsten-tin deposits.

Dynamic modeling and behavior of parabolic trough concentrated solar power system under cloudy conditions

As a promising application of solar energy, parabolic trough concentrating solar power with indirect thermal energy storage has been widely used in concentrating solar power plants constructed in China. The dynamic modeling and behavior of the power plants were important for achieving fast start-up and shut down and to overcome weather disturbances. This study investigated the dynamic characteristics of a 50 MW parabolic trough concentrating solar power plant with indirect thermal energy storage. Simplified cloud disturbances were simulated to obtain the dynamic characteristics of a power block coupled with solar field and thermal energy storage. Simulation results indicated that the thermal inertia of solar field is an order of magnitude larger than that of power block and thermal energy storage subsystems, and the heat transfer fluid temperature at the solar field outlet fluctuates within a narrow range at rated value under the control scheme of solar field. The disturbances caused by heat transfer fluid temperature fluctuation were reduced by thermal energy storage operation. To minimize the generation load fluctuation under thick-cloud condition, the thermal energy stored in solar field could be used to moderate the fluctuation caused by the start-up of thermal energy storage discharging exchanger.