Heat Addition Research Articles

Variable and Assured Peak Electricity Production from Base-Load Light-Water Reactors with Heat Storage and Auxiliary Combustible Fuels

In a low-carbon world (nuclear, wind, solar, and hydro) there is the need for assured dispatchable electricity to replace the historical role of fossil fuels. Base-load reactors can provide variable electricity to the grid by (1) sending some of their output (steam) to storage at times of low electricity prices and (2) using stored heat to produce added peak electricity at times of high electricity prices. Heat storage (steam accumulators, sensible heat, etc.) is less expensive than electricity storage (batteries, hydro pumped storage, etc.). The added cost of incrementally larger or standalone turbine generators for peak electricity production is small. However, energy storage systems (heat or electricity) can’t provide assured capacity for extreme events, be it supply side (extended low-wind or low-solar conditions in systems with high wind or solar capacity) or demand side (long periods of cold or hot weather). With heat storage systems there is the option to provide peak electricity output when heat storage is depleted by heat addition with a water-tube boiler using natural gas, biofuels, or ultimately hydrogen. Fuel consumption for assured peaking capacity is small because most of the time the heat storage system meets peak electricity demands. The same systems enable reliable low-cost heat production for industry. Such systems enable an all nuclear or nuclear/hydro/wind/solar/geothermal low-carbon electricity grid.

Control-oriented modeling and real-time simulation method for a dual-mode scramjet combustor

The control-oriented modeling and real-time simulation method for a dual-mode scramjet combustor has been conducted in this paper. The 1-D unsteady model coupled with isolator shock train model and oblique shock wave modification can treat variable area, fuel addition, combustion heat release, variable specific heat, inflow air vitiation component, wall friction and mixing efficiency. Combustion is simplified into mass and heat addition process. So this paper discusses heat release distribution obtaining method which can be applied in scramjet combustor 1-D flowfield simulation in detail. It is fit for certain scramjet combustor configuration and acceptable over a wide range of inflow conditions. By mixed programming of C and Matlab, the code of model solving is capsuled into S-Function which can be used in SIMULINK. The control-oriented model is built on SIMULINK platform. When the model runs in a single-core 3.6 GHz Intel Core i7-4790 processor, computation time-consuming is found to require 5–10 ms within a control period. The computing speed indicates very promising, because model is compact enough to run in real time, and it can be used as an embedded model in control system research. This model can also be used to analyze unsteady and steady flowfield characteristic. The safety boundary codetermined by unstart and over-temperature is conducted using this model.

CFD Modeling Development for DNB Prediction of Rod Bundle with Mixing Vanes Under PWR Conditions

Critical heat flux (CHF) is a primary parameter for nuclear fuel design and plant operation safety. CHF values are normally obtained from fuel bundle integral departure from nucleate boiling (DNB) or dryout experiments. These experiments are expensive, and detailed measurements (bubble dynamics, void fraction distribution, etc.) are difficult to obtain, particularly under typical pressurized water reactor (PWR) conditions of high pressure and temperature. Therefore, it is highly desirable that computational tools such as computational fluid dynamics (CFD) provide detailed flow and heat transfer information that will efficiently facilitate design improvements of PWR fuel designs.For the CFD studies described in this paper, an Eulerian-Eulerian two-phase modeling approach was adopted to predict DNB in a fuel assembly with mixing vane grids. Subcooled flow boiling was simulated using heat flux partition modeling and phase interactions. Direct addition of heat to the vapor was activated when the local vapor volume fraction reached a specified critical value. Emphases were placed on bubble departure diameter, phase interactions, and pressure drop for two-phase modeling development. Simulations were conducted in steady state. Solution convergence was closely monitored for physical variables in terms of local and global scales. A multi-indicator approach was used to judge DNB occurrence, and a new integrated DNB indicator is proposed.For validation, this CFD-based DNB modeling methodology was applied to two 5 × 5 rod bundle tests equipped with mixing vane grids and uniform axial power shape. The tests were performed under PWR conditions (16.5 MPa) and produced an exit quality of −4% and 11%. The CFD results show the validity of the new DNB indicator and the improved reliability with the multi-indicator approach. Correctly predicted DNB occurrence locations show the promise of the current modeling approach. Utilization of measured pressure drop and fluid temperature data may permit some bottom-up validations, and this effort may prompt further improvements for experimental measurements, particularly under high-pressure conditions.

Aerothermodynamic effects of controlled heat release within the hypersonic shock layer around a large angle blunt cone

Effects of controlled heat addition into the high temperature, chemically reacting shock layer of a large angle (60°) blunt cone with a spherical nose have been experimentally investigated. The exothermic oxidation of ablated chromium from the surface of the cone at hypersonic Mach numbers triggers the heat release process. A conical skirt with a base diameter of 70 mm and a semi-apex angle of 30°, culminating into a nose of radius 30 mm, has been used as the test model. An in-house hypersonic free-piston driven shock tunnel facility, HST3, was used for the experiments at a stagnation enthalpy of 6.31 MJ/kg and a freestream Mach number of 9.84. The temperature distribution in the shock layer was experimentally measured by the two-color ratio pyrometry technique, using a Digital Single Lens Reflex (DSLR) camera as a pyrometer. The temperature field was corrected for discrete radiative line emissions obtained through emission spectroscopy. Surface heat flux measurements were taken using carefully calibrated thin film platinum heat transfer gauges mounted on an insulating Macor substrate. Shock stand-off distances were measured through Schlieren imaging of the flow using a high-speed camera at 20 000 frames per second, and also by a new intensity-scan based method using the processed color image from the DSLR camera. Calculations showed a 173 K rise in the temperature of the gas layer in the stagnation region due to chromium oxidation. The net surface heat flux on the blunt cone was also found to increase by about 31 W/cm2. The shock stand-off distance, as ascertained from Schlieren images, increased from about 3.82 mm (±1.4%) to 4.45 mm (±1.5%), a 17% rise. Analytical calculations, taking chromium oxidation reaction kinetics into consideration, to relate the total exothermic heat release to its distribution into various processes demonstrated that chromium oxidation releases about 78 W/cm2 energy in the stagnation region of the shock layer. 1.9% of this energy increases the temperature of the gas layer, 40% is convected back into the airframe, 0.4% is lost from the rear of the Macor substrate by conduction, and about 8% is radiated into the model. The remaining 50% of the heat was used up in pushing the shock layer away from the body by raising its density, thereby increasing shock stand-off distance.

Cavity flameholding in an optical axisymmetric scramjet in Mach 4.5 flows

The dynamics of an optical axisymmetric scramjet, preferred for generic combustion and flameholding studies without the corner boundary-layer effects that distort the freestream and flame propagation in rectangular scramjets, is investigated at Mach 4.5. Ethylene fuel is injected into supersonic flow via sixteen sonic fuel nozzles equally spaced in a circumferential direction and inclined at 45° to the freestream. The gaseous fuel is auto-ignited by high-enthalpy flows that are compressed and decelerated by shockwaves and boundary layers while passing through the scramjet inlet and isolator. An axisymmetric cavity located downstream of fuel injectors achieves flame holding by providing slow flow recirculation regions and inducing shockwaves at cavity leading edge and ramp to redirect and recompress flows. Flow and flame behaviors are characterized by high speed flame chemiluminescence imaging and static pressure measurement, while the detailed flame structures are resolved by instantaneous ground-state hydroxyl radical (OH) distributions using planar laser-induced fluorescence (PLIF). Numerical simulation is employed to aid the inlet/isolator design to avoid unexpected unstart introduced by shock-boundary layer interactions in the shock train region. The Mach number profiles in the radial direction are measured using a Pitot probe at the combustor exit. We demonstrate supersonic flameholding with the presence of a cavity at ethylene fueled conditions where stable combustion is achieved without scramjet unstart under both mass and heat loading. The heat addition from the cavity-stabilized flame mainly reduces the flow Mach number in the near-wall flow region. In the core flow region, the flow Mach number is decreased by the jet- and cavity-induced shockwaves and minimally affected by heat addition.

Reassessing Operational Strategies for Wax Management Reduces Expenses

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 27532, “The Importance of Periodic Reassessment of Operational Strategies for Wax Management,” by David M. Lavenson, SPE, Rama Venkatesan, SPE, Michelle K. Young, and Neal Kebert, Chevron, prepared for the 2017 Offshore Technology Conference, Houston, 1–4 May. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. This paper presents a case study that is an example of how reassessing a flow-assurance risk-management strategy for operating assets can identify opportunities for optimization. Too often, flow-assurance risks are examined only after problems occur. In the absence of these events, many may assume the flow-assurance risks are managed optimally. Periodic reassessment of the risk-management strategies is a key concept for full life-cycle flow-assurance engineering. Introduction Flow-assurance risks for offshore fields can be managed in a variety of ways that can be defined generally into risk-management or risk-avoidance strategies. As offshore developments progress into deeper waters with more-challenging technical issues, more-costly risk-avoidance strategies can jeopardize overall project economics. In contrast, risk-management strategies are considered through means of mechanical, thermal, operational, or chemical adjustments to manage the flow-assurance risk rather than attempting to remove it entirely. Waxy crude oils are fairly common in offshore operations. As system temperatures drop below the wax appearance temperature (WAT), wax crystals will precipitate and cause deposition issues because of the thermal gradient between the bulk fluid and the pipe wall. A variety of mitigation techniques can reduce the effects of wax deposition on flowlines and pipelines offshore, including insulation, addition of heat, pigging, and the addition of paraffin inhibitors. In the development stages of a project, these risks are quantified by use of fluid properties and additional laboratory testing in order to estimate the required risk level and economic options for risk mitigation. The selected methods for managing the risk are used for first oil and adjusted and optimized while minimizing risk of compromising safe and reliable operations. Given the dependence of flow-assurance risks on various fluid and system properties, these risk-management strategies require periodic reassessment to ensure an optimized approach. This paper will present a case study where reassessment of a flow-assurance risk-management strategy resulted in an optimized approach that generated significant operational-expenditure savings. An offshore, brownfield development in West Africa has two subsea export pipelines that transport a medium-gravity waxy crude oil to an intermediate platform and eventually onshore. The crude in the export lines is from multiple wells and commingled, with each crude featuring varying amounts of wax, resulting in a combined oil that has a WAT ranging from 70 to 85°F. Ambient water conditions are less than 50°F, resulting in a temperature gradient across the fluid and pipe wall to the seawater. Because of the length of the export pipelines and lack of insulation, the oil cools to temperatures below the WAT well before the export line terminates at the intermediate platform.

Advanced Concepts in Modular Coal and Biomass Gasifiers

The program involves the application of a novel gasification concept, termed a modular allothermal gasifier (MAG) to produce syngas from coal, biomass, and waste slurries. The MAG employs a steam-driven gasification process using a pressurized entrained flow reactor wherein the external wall surfaces are catalytically heated to 1000 °C via heterogeneous combustion of a portion of the produced syngas. The MAG can be fed by a hydrothermal treatment reactor for biomass and waste feedstocks, which employs well-developed hydrothermal processing technology using the addition of heat and water to provide a uniform slurry product. The hydrothermal treatment reactor requires no preprocessing and a clean syngas is produced at high cold gas efficiency (80%). Importantly, the MAG can operate over a wide range of positive pressures up to 3 MPa (30 bar) which provides process control to vary the output to match end-use needs or feedstock rate. The system produces minimal emissions and operates at significantly higher efficiency and lower energy requirements than pyrolysis, plasma gasification, and carbonization systems. The system is compact and modular, making it easily transportable, for example, to a variety of sites, including those where remoteness, inaccessibility, and space limitations would preclude competing systems. The system can be applied to small gasification systems without the increase in heat losses that plague conventional small scale gasifiers. Test results and model simulations are presented on a single tube system and analyses of a variety of configurations presented.

Investigation and recent developments in aerodynamic heating and drag reduction for hypersonic flows

Investigation on new methods of drag reduction and thermal protection for hypersonic velocities are proposed based on the new technologies for shock reconstruction. In principle, a blunt vehicle flying at high speeds generates a strong bow shock wave ahead of its nose, which is responsible for the high drag and aero heating levels. There have been a number of efforts devoted towards reducing both the drag and the aero heating by modifying the flow field ahead of the vehicle’s nose. An introduction to the philosophy and recent development in hypersonic aerodynamic heating and drag reduction techniques are presented. These techniques are classified in four major group. Geometrical, mass injection, energy deposition, and magneto aerodynamic techniques. In this review, these new techniques and investigation of the philosophy and development procedure of these techniques are brought to the table and then the effects of each method on drag wave and aerodynamic heating reduction is shown. Geometrical techniques such as structural spike and aerodisk, cavity, multi-row disk (MRD) use to drag reduction. Mass injection techniques like arrays of micro jets, spike and jet, heat addition and plasma injection are very useful to aerodynamic heating reduction. Energy deposition techniques by using laser and plasma can reduce aerodynamic heating and wave drag of hypersonic flows. Magneto aerodynamic technique can reduce drag and aerodynamic heating, by the addition of the magneto technology in hypersonic flows. The present paper is devoted to surveying these studies and illustrating the contributions of the authors in this field. Not only do the paper criticize the previous investigations but also raises some of the areas in the field that need further investigations.

Hybridizing a geothermal power plant with concentrating solar power and thermal storage to increase power generation and dispatchability

Geothermal power plants often deploy less than their full power capacity due to declining geothermal resources. Integrating heat from a concentrating solar power (CSP) collector field increases the power output at low cost. This article considers five methods of solar heat addition in a double-flash geothermal plant. The most promising solution converts solar heat into electrical work with an efficiency of 24.3%. The economic feasibility and optimal sizing of the solar field and thermal stores are evaluated. A hybrid plant that increases power generation from 22 to 24 MWe has a Levelized Cost of Electricity (LCOE) of 0.07 ± 0.01 $/kWhe. Adding three hours of storage increases the LCOE to 0.08 ± 0.01 $/kWhe. Photovoltaic systems are considered to be a low-cost renewable technology, but an equivalent photovoltaic system with battery storage costs 0.15 ± 0.07 $/kWhe due to the high cost and replacement rate of batteries compared to thermal storage. The hybrid plant also has a lower LCOE than a conventional CSP plant. If the dispatchability that thermal storage provides is rewarded with higher electricity prices, calculations indicate storage becomes an attractive investment when discharged power receives 1.75 times the typical price of electricity.

Plutons and domes: the consequences of anatectic magma extraction—example from the southeastern French Massif Central

Anatectic magmas form plutons or accumulate in the core of anatectic domes. Both scenarios have distinct implications on the behaviour of the continental crust during orogenic evolution from collision to collapse. Considering a stepwise extraction of melt, we simulate the evolution of anatectic melt and of solid residues produced in the crust from collision to collapse using thermodynamic modelling. We also simulate the effect of entrainment of source material (restite-unmixing and peritectic assemblage entrainment) on the compositional range of the resulting magmas. The results are then compared to the compositions of lower crustal xenoliths and of peraluminous granites in both plutons and anatectic dome in the southeastern French Massif Central (SE-FMC). From our calculations, we identify two type of anatectic melts (1) cool-and-wet produced at low-temperature ( 750 °C) which only release fluids at the end of crystallisation. When emplaced around 0.4 GPa, cold-and-wet melts are produced by muscovite-dehydration melting reactions; hot-and-dry are produced by biotite-dehydration melting. In the SE-FMC, the Velay dome is cored by the Velay granite, intruded by small bodies of Velay leucogranite and surrounded by plutons made of either two mica leucogranite (MPG) or cordierite-bearing granite (CPG). MPG and Velay leucogranite compositions are best reproduced by cool-and-wet magmas. CPG and Velay granite compositions are best reproduced by hot-and-dry magmas. Melt extraction after biotite dehydration melting leaves residues that are similar in composition to lower-crustal xenoliths. Magmas forming plutons migrate freely toward the upper crust forming plutons with distinct compositions. On the contrary, to form a dome, magmas are retained on the way up. The emplacement and accumulation of magma at deeper level enhances (or trigger) melting due to the addition of heat (from hot-and-dry) and fluids (from cool-and-wet). The accumulation of magma and the in situ melting increases melt fraction and has consequence to weaken the middle crust and leads to the formation of an anatectic dome. We suggest that magmas are retained due to lithological heterogeneities in the crust. In the case of the Velay dome, a large orthogneiss formation similar to the Velay orthogneiss formation may have played that role.

Anthropogenic heat flux in English Bazar town and its surroundings in West Bengal, India

Increasing use of energy consumption, carbon emission, thermal uncomfortability in densely populated metropolitan centre is not only an emerging challenge but also in the meso and micro level towns. The present work wants to investigate is the anthropogenic heat flux as additional heat in radiation energy balance carried an important role to alter the thermal environment of the English Bazar town and its peripheral areas? Is this heat flux increasing over advancing of time? Is this heat flux distinguishable over different land use/ land covers? Calculated anthropogenic heat flux from remotely sensed satellite data reveals that maximum anthropogenic heat flux is increased from 54.52 W/m2 to 188 W/m2 in between 1990 and 2017. Core urban area, commercial units, high rise densely populated built up areas discharge maximum anthropogenic heat flux (>120 W/m2). Clear heat flux gradient is observed from urban mainland to peripheral sub urban areas. Natural units like vegetated areas, water bodies are recorded zero anthropogenic heat flux. Increasing trend of anthropogenic heat addition to the urban climate will make the situation more uncomfortable in coming days and therefore, stress should be given on clean technologies and use of solar energy to slacken down thermal annoyance.

Dynamic modeling of a particle/supercritical CO2 heat exchanger for transient analysis and control

A dynamic model of a moving packed-bed particle-to-sCO2 heat exchanger and control system for concentrating solar power (CSP) applications is presented. The shell-and-plate heat-exchanger model allows for numerically investigating the transient operation and control of the heat addition to the power cycle in a particle-based CSP plant. The aim of the particle-to-sCO2 heat exchanger is to raise the sCO2 temperature to 700 °C at a pressure of 20 MPa. The control system adjusts both the particle and sCO2 mass flow rates as well as an sCO2 bypass to obtain the desired sCO2 turbine inlet and particle outlet temperatures for a prescribed thermal duty. The control system is demonstrated for disturbances in particle and sCO2 inlet temperatures as well as changes in thermal duty for part-load operation. A feed-forward control strategy that adjusts the sCO2 and particle mass-flow rates as functions of measured inlet temperatures and a steady-state model solution was able to return the heat exchanger to the desired operating condition, but not without experiencing significant deviations in the sCO2 turbine inlet and particle outlet temperature (>40 °C) during the transient. To reduce both sCO2 and particle temperature deviations, a feedback control strategy was investigated, where sCO2 and particle mass-flow rates based on the steady-state model solution were corrected based on measured outlet temperature deviations. The feedback control strategy maintains sCO2 turbine inlet and particle outlet temperature to within 16 °C of the set points with a three-minute settling time for step changes in inlet conditions and thermal duty. This finding demonstrates the possibility of dynamically dispatching next-generation particle-based CSP plants driving sCO2 power cycles.

Earth Systems Thinking: Global Consumerism, Climate Change, and the Spiritual Value of the Earth

In this paper we consider the root cause of climate change to be the industrial waste heat by product of increasing global consumption. The embodied energy associated with the conversion of Earth’s resources into consumer goods has largely been driven by fossil fuel based energy. Using available data, we show how a) the rate of annual CO2 emissions to the atmosphere is increasing, b) the land+sea temperature anomaly index is increasing, particularly the last 3 years, c) the rate of heat addition to the world’s oceans is also accelerating as this is in direct response to a globally increasing consumption per capita. In short, all of our human induced rates related to consumption are accelerating with increasingly severe consequences to the Earth system that maintains us. This is occurring amidst the reality that humans are in a necessary physical partnership with nature. Despite this, many human cultures have pursued dominance over the Earth’s resources. This dominance is asserted by the mechanical philosophy of Descartes. Under this world view, the Earth is just a (soul-less) machine and man is distinct from nature and therefore entitled to dominate it; the Earth has no spiritual value. So this gives us license to dig up the planet to create the escalating distribution of products to global consumers and this is exactly what can be verified from the data. We refer to this as the business as usual trajectory. To correct this course trajectory, we propose two avenues: a) extend the concept and legality of the Public Trust Doctrine to all of Nature’s resources so that current generations have an obligation to ensure the future generations can same similar access to these resources, b) adopt a systems thinking approach that prioritizes human equity, dignity, environmental justice and environmental health over escalating global GDP. In short, global justice should be our priority, not global profit. From the systems thinking viewpoint, the Earth is not a market commodity subject to resource exhaustion, it is rather a sacred equilibrium system for the welfare of all.

The Impact of Different Forcing Agents on the Residual Circulation in a Tropical Estuary (Baía de Todos os Santos, Brazil)

ABSTRACT Santana, R.; Teixeira, C., and Lessa, G., 2018. The impact of different forcing agents on the residual circulation in a tropical estuary (Baia de Todos os Santos, Brazil). This study investigated the forcing of the residual circulation in a tropical estuary, Baia de Todos os Santos, Brazil (BTS). A numerical model (Regional Ocean Modeling System), forced with climatological means, was used to investigate the seasonal roles of the tide, wind, net heat, surface water fluxes, and river discharge on the residual circulation. The tide is the main driver of the circulation and its residual flow is structured at the bay mouth with a net-landward flow in the channel center and a net-seaward flow on the shoulders. The addition of wind drag affected the surface circulation, forcing W-bound (N-bound) currents in the spring–summer (fall–winter) months and generating a positive sea-level slope toward the continent. The addition of heat and surface water fluxes to the simulation established an incipient gravit...

Thermodynamic analysis of hybrid Rankine cycles using multiple heat sources of different temperatures

Past studies of hybrid power cycles using multiple heat sources of different temperatures focused mainly on case studies and almost no general theory about this type of systems was developed. This paper is a first comprehensive study of their general thermodynamic performance, with their comparison to their corresponding single temperature heat source reference system, focusing on three types of power cycles: simple Rankine cycle, Rankine cycle with reheat and Rankine cycle with heat regeneration. The generalized expressions for the energy and exergy efficiency differences between the hybrid and the corresponding single heat source system were developed. A number of simulation case studies were performed to help the understanding and confirm the thermodynamic generalization of the results. The results show that the energy and exergy efficiencies of the hybrid systems are higher than those of their corresponding single heat source reference systems if and only if the energy andexergy conversion efficiency (defined in the paper) of the additional heat source (AHS) is larger than that of the original heat source. The conditions that defined the effects of the AHS temperature and heat addition rate on the energy and exergy efficiencies of the hybrid systems as convex or concave curves were described. Comparisons across the first two types of hybrid power cycles were made, showing that the energy and exergy efficiencies of the reheat Rankine cycle is generally higher than that of the simple Rankine cycle as AHS is changed. Recommendations were made for obtaining the maximal energy and exergy efficiency as a function of the AHS temperature, of the heat addition rate by the AHS, and of the AHS position in the power cycle flow sheet. For the hybrid power generation systems with heat regeneration it was found that when using an AHS to raise the net system power by a given amount, using it to replace the higher-pressure extracted steam will result in a higher system energy efficiency than when using it to replace lower-pressure extracted steam. Hybrid cycles can have significantly lower emissions, cost, and fuel depletion.

Effects of Temperature on the Density of Water Based Drilling Mud

Rheological properties are tested throughout a drilling operation as it is critical in the control and maintenance of rheological properties. This paper investigates the effects of temperature on the density of water based drilling mud. Water based mud was prepared with resistant additives and weighing materials for temperature conditions ranging 28 o C,30 o C,40 o C,50 o C,60 o C, 70 o C and the densities at these temperature ranges was determined. The experimental data obtained supports the idea that mud density being a rheological property decreases (8.85ppg - 8.49ppg) with increase in temperature (28 o C to 70 o C).This is as a result of the mud contents becoming degraded upon addition of heat at higher temperatures

Suppressing Aluminum Carbide in Welding Aluminum Silicon Carbide Composite

Weldability of aluminum-based metal matrix composite A359/SiC/10p using gas tungsten arc welding and R356.0 filler material is investigated. The welding current, welding speed, and preheat temperature affect the weld quality significantly. Finite element analysis is successfully applied to map the weldment temperature during preheating and welding. During mechanical testing of welded specimens, a crack propagates in the parent composite or in the weld, but not in the stronger zone between the weld and the parent material. The weld region contains reasonably uniform distribution of SiC particles due to high viscosity of the molten weld and its fast cooling rate. Proper control of heat input and addition of silicon-rich filler material hinder the interface reaction between aluminum matrix and the reinforcing SiC particles, and successfully suppresses the formation of harmful aluminum carbide flakes in the weld. The average tensile and flexural strengths of optimally welded specimens approach those of the parent composite while its ductility exceeds that of the parent material.

Estimating Two Heat-Conduction Parameters From Two Complementary Transient Experiments

A desirable feature of any parameter estimation method is to obtain as much information as possible with one experiment. However, achieving multiple objectives with one experiment is often not possible. In the field of thermal parameter estimation, a determination of thermal conductivity, volumetric heat capacity, heat addition rate, surface emissivity, and convection coefficient may be desired from a set of temperature measurements in an experiment where a radiant heat source is used. It would not be possible to determine all of these parameters from such an experiment; more information would be needed. The work presented in the present research shows how thermal parameters can be determined from temperature measurements using complementary experiments where the same material is tested more than once using a different geometry or heating configuration in each experiment. The method of ordinary least squares is used in order to fit a mathematical model to a temperature history in each case. Several examples are provided using one-dimensional conduction experiments, with some having a planar geometry and some having a cylindrical geometry. The parameters of interest in these examples are thermal conductivity and volumetric heat capacity. Sometimes, both of these parameters cannot be determined simultaneously from one experiment but utilizing two complementary experiments may allow each of the parameters to be determined. An examination of confidence regions is an important topic in parameter estimation and this aspect of the procedure is addressed in the present work. A method is presented as part of the current research by which confidence regions can be found for results from a single analysis of multiple experiments.

Magmatism in the Shapinggou district of the Dabie orogen, China: Implications for the formation of porphyry Mo deposits in a collisional orogenic belt

The Shapinggou molybdenum deposit is located in the Qinling-Dabie Orogen, which hosts the world's largest molybdenum belt. The igneous rocks at Shapinggou can be divided into two stages (136–127 Ma and 118–114 Ma), the early suite of felsic (136–127 Ma, SiO2 = 58.0 to 72.9 wt%) and mafic rocks (133–128 Ma, SiO2 = 45.2 to 57.0 wt%), and a later suite comprising syenite (117 Ma, SiO2 = 64.2 to 65.0 wt%), quartz syenite porphyry (116 Ma, 62.5 to 70.0 wt%), granite porphyry (112 Ma, SiO2 = 75.5 to 77.6 wt%) and diorite porphyry (111 Ma, SiO2 = 56.6 to 59.7 wt%). The early-stage felsic rocks display high SiO2, Al2O3, Na2O, K2O, Sr, LREE contents, and Sr/Y, (La/Yb)N ratios, initial Sr isotope ratios of 0.7076 to 0.7089, but low MgO, FeOT, Y, Yb contents and negative εNd(t) values, consistent with partial melting of the lower continental crust. The early-stage mafic rocks exhibit low SiO2, high MgO, Ni and Cr contents, consistent with an upper mantle source, but trace element and isotope data suggest a role for crustal contamination. The late-stage syenite and quartz syenite porphyry show high abundances of Na2O, K2O, Al2O3, HFSEs (e.g., Th, U, Zr, Hf) and significant negative Eu anomalies. The late-stage granite porphyry displays high SiO2 contents, and depletions in Ba, Sr, Eu and Ti. The geochemical features of the late-stage intrusions are similar to A-type granites. Crystal fractionation of plagioclase, K-feldspar, biotite/ muscovite, amphibole/ garnet and Fe-Ti oxides controlled the evolution of the magma. The geochemical and isotopic data suggest that the rocks at Shapinggou were likely derived from a mixed source of lithospheric mantle, subducted continental crust of the Yangtze Block (Kongling Group) and partial melts of the Dabie Complex. Early stage rocks represent melts of the source with a lower proportion of Dabie Complex materials, whereas late stage rocks were derived from a source with a higher proportion Dabie Complex component. The geochemical and isotopic variations of the intrusions at Shapinggou were controlled by both source characteristics and fractional crystallization. Although the Shapinggou deposit is located in a continental collision orogen, the magmas formed in an intraplate extension setting, with an increase in the amount of extension from the early to late stages. As well, both stages intrusions at Shapinggou were generated by the addition of heat, due to lithospheric delamination, mantle upwelling and rapid mantle convection, related to the far-field effects of the westward subduction of the paleo-Pacific Plate beneath the Asian continent. The geochemistry and setting suggest that the formation of a giant Mo deposit does not require a Mo-rich magma source, but rather an efficient convection mechanism for the transport of volatiles and Mo in a granitic magma system. The fluids derived from the granite porphyry at Shapinggou were more oxidised than that from the barren intrusions.

Natural circulation in a rectangular loop with vertical heater below vertical cooler

Abstract Many upcoming new generation reactors employ natural circulation for heat transfer in normal mode of operation. Natural circulation systems are simpler and safer than their forced circulation counterparts. However, these systems are prone to flow instability which are undesirable due to several reasons. In the present work, a rectangular glass loop, wherein cooler is just above the heater, has been considered for experimental and numerical investigation at atmospheric pressure. Heat addition from room conditions has been studied to understand the natural circulation loop dynamics, checking the possibility of occurrence of instability with the new orientation of the heater and the cooler. Experiments were performed at different power levels and coolant flow rates. CFD analyses were performed for all the cases investigated experimentally using the commercial CFD code ANSYS FLUENT 14.0. No instability was observed during the experiments and none during the simulations done for the duration of the experiments.