Melt Fraction Research Articles

Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

Elucidating the role of sulfur on the structure of silicate glasses and melts at elevated pressures and temperatures is important for understanding transport properties, such as electrical conductivity and viscosity, of magma oceans and mantle-derived melts. These properties are fundamental for modeling the evolution of terrestrial planets and moons. Despite several investigations of sulfur speciation in glasses, questions remain regarding the effect of S on complex glasses at highly reducing conditions relevant to Mercury. Glasses were synthetized with compositions representative of the Northern Volcanic Plains of Mercury and containing quantities of S up to 5 wt%. Multiple spectroscopic methods and microprobe analyses were employed to probe the glasses, including in situ impedance spectroscopy at 2- and 4-GPa pressures and temperatures up to 1740 K using a multi-anvil press, 29Si NMR spectroscopy, and Raman spectroscopy. Electrical activation energies (Ea) in the glassy state range from 0.56 to 1.10 eV, in agreement with sodium as the main charge carrier. The electrical measurements indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. The glass transition temperature lies between 700 and 750 K, and for temperatures up to 970 K Ea decreases (0.35–0.68 eV) and the conductivities of the samples converge (∼5–8 × 10−3 S/m). At Tquench, the melt fraction is 50–70% and melt conductivity varies from 0.7 to 2.2 S/m, with the sample containing 5 wt% S the most conductive among the set. 29Si NMR spectra reveal that a high fraction of S bonds with Si in these complex glasses, a characteristic that has not been recognized previously. Raman spectra and maps reveal regions rich in Ca–S or Mg–S bonds. The evidence of sulfide interactions with both Si and Ca/Mg suggest that alkaline earth sulfides can be considered weak network modifiers in these glasses, under highly reduced conditions.

Effect of fin design and continuous cycling on thermal performance of PCM-HP hybrid BTMS for high ambient temperature applications

In the present work, the thermal performance assessment of fins for a Phase Change Material-Heat Pipe (PCM-HP) based hybrid battery thermal management system (BTMS) for maintaining the average temperature of the battery surface below the safe temperature limits during continuous discharge and charge cycles is presented. A 2D computational model is used for fin design selection and to investigate the thermal performance of the PCM-HP hybrid BTMS. Two base designs and twelve fin designs with varying geometry are studied. The optimal design is chosen based on the effectiveness of the fins, the maximum battery temperature, and the PCM melt fraction. With the optimized fin design, the PCM-HP hybrid BTMS reduces the maximum battery surface temperature by 2.95 °C from 62.85 °C to 59.9 °C as compared to PCM-HP BTMS without fin. Using the selected fin the maximum battery surface temperature is maintained below 60 °C with minimum PCM melt fraction at a heat transfer coefficient of 90 W/m2K for three continuous cycles at an ambient temperature of 40 °C. Experiments are performed to verify the thermal performance of the optimized design. Further, it is observed that increasing the latent heat and thermal conductivity enhances the thermal performance of the PCM-HP hybrid BTMS.

Energy and exergy analysis of latent heat storage with heat pipe encased in phase change material

Loop heat pipe (LHP) encased in phase change material (PCM) incorporated annular to catalytic converter (CC) is proposed to augment the performance of the “thermal energy storage” (TES). LHP are designed to extract surplus heat from the exhaust discharge, thereby reducing the amount of exhaust heat emitted into the atmosphere. A four-cylinder IC engine’s CC is considered with Mg70Zn24.9Al5.1, paraffin oil as PCM and working fluid for the heat pipe are evaluated. A comparative experimental investigation was performed considering two models for CC with and without heat pipe integrated in the TES for (i) distribution of average PCM temperature (ii) energy, exergy efficiency and distribution (iii) effectiveness (iv) instantaneous waste heat recovered during heat storage. Transient cycles at 2000 r/min with varying load conditions were run considering city drive conditions. Heat storage for CC with heat pipe encased in TES was found to be 35% faster, whereas discharge time for CC without heat pipe developed in TES was found to be longer. For melt fraction 1, maximum exergy efficiencies of 71% and 69% were observed for the TES unit with and without heat pipe. Heat pipes are observed to help extract a considerable amount of surplus heat from exhaust and reduce the exhaust gas outlet temperature released into the atmosphere by nearly 130 – 40°C under various load circumstances.

Impact-related chemical modifications of the Chang’E-5 lunar regolith

Impact events on the Moon have been recognized as modifying the composition of surface materials through processes such as shock metamorphism and mixing with exotic components. Previous studies have indicated that the regolith sampled by the Chinese Chang’E-5 mission was primarily evolved from local mare basalts, likely originating from a single episode of effusive volcanism. The relatively simple and monotonic protolith of the Chang’E-5 regolith presents a unique opportunity to investigate the chemical modifications induced by impact events. In this study, we conducted detailed petrographic and mineralogical analyses on a diverse set of lunar regolith samples, including thirty-three small impact glass particles (39–227 μm), one large agglutinate (∼1.6 mm), and sixteen basaltic clasts (0.1–1.6 mm). Numerical modeling was also conducted to quantitatively assess the melting behavior of basaltic clasts under different impact conditions. Our primary objective was to evaluate the chemical variations of impact glass in relation to lithic clasts. While the majority of homogeneous impact glass spherules and larger basaltic clasts (≥1 mm) exhibit similar bulk compositions (e.g., Al2O3, CaO and FeO) to the local regolith, we recognize additional effects of impact processes, including impact comminution, impact melting and crystallization, differential volatilization, and potentially selective melting. These processes have modified the texture and geochemistry of lunar regolith components. The chemical signatures of small clasts in the Chang’E-5 regolith indicate that the fine size fractions (e.g., those with diameters of ≤ 300 μm) are predominantly composed of lithic and monomineralic fragments with a substantial proportion being dominated by mesostasis. Melting of these sub-millimeter fractions may lead to the formation of impact glass with chemical compositions deviating from the average local regolith. These results have implications for understanding the compositional evolution of the Chang’E-5 regolith. Notably, our study suggests that impact glasses spherules with different major (e.g., TiO2, MgO) and minor (e.g., REEs, Zr, Th and U) element compositions could be derived from the same protolith of local mare basalts, instead of being exclusively attributed to exotic impact ejecta. In this case, small-scale local impacts may have played a crucial role in the impact history of the Chang'E-5 landing site.

Prediction of transient melt fraction in metal foam - nanoparticle enhanced PCM hybrid shell and tube heat exchanger: A machine learning approach

Phase change materials (PCMs) have gained popularity in storing thermal energy due to their high energy storage capacity per volume. However, the low performance of the PCM heat exchanger (HX) is primarily due to poor thermal conductivity. The performance of these systems can be improved by using metal foams, nanoparticles, fins, etc. In the present work, the melt fraction (MF) in PCM shell and tube (ST) heat exchanger (HX) with a hybrid combination of metal foam + Graphene nanoplatelets (GNP) nanoparticles (NPs) is predicted using the Machine learning (ML) algorithms. This study analyzes 0.93, 0.95, and 0.97 porosity copper metal foams and 0.5% and 1% volume fraction GNP NPs considering the orientation (0°, 30°, 45°, 60° and 90°) effects of HX. Numerical simulations are carried out to collect the data, to train, cross-validate, and testing. Linear regression (LR), support vector regression (SVR), XGBoost (XGB), and K nearest neighbor (K NN) ML algorithms are used to predict the MF of the PCM in HX with respect to time. MF is predicted during both the melting and solidification processes. Among the ML models selected, the LR model has predicted the transient variation of MF with the highest accuracy during both melting and solidification.

Petrological models of magma evolution on the formation of mafic-felsic igneous complexes of the Emeishan large igneous province, SW China

Many Late Permian world-class Fe-Ti oxide-bearing layered intrusions in the Pan-Xi region, SW China are commonly considered to be fractionation products of the Emeishan mantle plume-related high-Ti basaltic melts. These layered intrusions coexist spatially and temporally with A-type granitoids, which consist of syenites and granites and are further classified into isotopically depleted metaluminous to peralkaline and isotopically enriched peraluminous to metaluminous groups. The petrogenesis of these mafic-felsic igneous complexes has been controversial. This study investigates geochemical correlations of the microgabbros at the margin of the Baima layered intrusions and the intruding isotopically enriched granitoids. The amphiboles at both sides of the contact zone are calcic (CaO = 10.4 to 12.5 wt.%) and display obvious mixing trends. Thermodynamical modeling using the MAGEMin program indicates that fractionation of basaltic melts compositionally similar to the Baima microgabbros seems incapable to crystallize olivine compositions comparable to those of the layered intrusions, but can be reconciled by early separation of 7.5 to 10 wt.% Fe-Ti-rich melts. Continued differentiation of the basaltic melts may lead to formation of the isotopically depleted granitoids, among which perthite accumulation in water-rich environments could result in the formation of metaluminous granitoids with high Na, K and Al contents and positive Eu anomalies. The isotopically enriched granitoids, on the other hand, can be produced by anatexis of the juvenile mafic lower crust together with the Yangtze ancient lower crust. Our study therefore provides a panoramic view on the complicated petrogenesis of the igneous complexes related to Emeishan mantle plume impingement through thermodynamic modeling.

Numerical study on latent heat storage systems with and without fins during simultaneous charging and discharging process

A numerical study is carried out on phase change material (PCM) impregnated in shell and tube heat exchangers with and without fins. The simultaneous charging and discharging (SCD) process is considered for the study, where the heat transfer occurs between heat transfer fluids (HTFs) and PCM simultaneously. The study intends to analyze the heat transport behavior of PCM and energy transport between the hot and cold HTFs. In the SCD process, the hot HTF is circulated through the hot tube, whereas cold HTF is made to simultaneously pass through the cold tube. The influence of the latent heat storage system (LHSS) inclination on the thermodynamic behavior of PCM with and without fins is inspected. To evaluate the effect of orientation four angles are considered. The angles include 90°, 60°, 30° and 0°. The investigation shows that the orientation significantly influences convective strength and melt fraction. An increase in melt fraction by 13.1% and 39.35% is observed when orientation is changed from 90° to 0° in finned and unfinned LHSS. It is also observed that the LHSS with fins gave an 18.31% higher melt fraction than without fins for vertical configuration. The LHSS with fins gave uniform temperatures and higher average Nusselt numbers. Among various configurations considered, LHSS with fins can be considered for 90° (vertical) and 60° orientations. In contrast, the LHSS without fins can be preferred for 30° and 0° (horizontal) positions.

Nano-enhanced phase change material using salt hydrate and cooper nanoparticles for battery thermal management system: Buoyancy-driven approach

Using computational fluid dynamic (CFD) simulation for battery thermal management system (BTMS) enables give a correct understanding of controlling battery temperature. The use of phase change material (PCM) is a popular option for managing the battery temperature in a certain range due to the solid-liquid transition, in which salt hydrate was used in this study. Also, adding nanoparticles with high thermal conductivity can compensate the low thermal conductivity of PCM, in which copper nanoparticles were used as PCM reinforcement in current work. In addition, the buoyancy force was considered in liquid phase, making the numerical results closer to physical ones. The present work focuses were on the effects of volume fraction of copper nanoparticle and discharge rate on battery temperature and melting fraction. Evidence indicated that the appropriate distance between the LIBs could set 0.1D, 0.2D, and 0.4D for C-rate of 2, 4, and 6, respectively. Additionally, most impacts of cooper nanoparticle with 3 % volume fraction was observed only in high SOC, e.g. 3 % volume fraction reduced the melting fraction from 38.5 % to 34.5 % in SOC = 100 %. Also, increase in C-rate from 2 to 6 warmed up LIB from 304 K to 319 K when zero volume fraction.

Microencapsulation of a salt hydrate phase change material by resorcinol formaldehyde through electrohydrodynamic disintegration of coaxially layered filament

Uniform microcapsules of size on the order of 100 nm with CaCl2.6H2O at the core and resorcinol formaldehyde as the shell was made by electro hydrodynamically disintegrating the coaxially layered filament. The shell thickness was varied by changing the flow ratio. The effect of shell thickness on the phase change temperature and the heat flow at its peak value during the DSC scan were reviewed to ascertain the extent of thermal equilibration, and the fraction of PCM melting at the peak value of heat flow. The integrity of the shell was evaluated by sustained dipping in deionized water for a month. The DSC scan was repeated after several heating-cooling cycles to understand the cycle life of the microcapsules.

Numerical simulation and analysis of heat transfer and melting rate of nano-enhanced PCM composite embedded in a concentrator photovoltaic system

The primary objective of this research is to explore the impact of nanoparticles-infused PCM (phase change material) in the context of nano-PCM-PV technology (PV: photovoltaic panel). Computational investigations were conducted to evaluate the effectiveness of RT25HC, a paraffin wax PCM, in conjunction with various nanoparticles (MgO, TiO2, ZnO and CuO) in solar panel cooling. The study also considers the influence of PV module inclination angles (β: 0 to 90°). High-resolution numerical simulations using the ANSYS-Fluent CFD platform were employed. The findings highlight the intricate relationship between nanoparticle addition, melting kinetics, electrical efficiency and PCM enthalpy. Specifically, the melting rate of RT25HC PCM exhibits notable differences between horizontal (β = 0°) and inclined panels (β ≠ 0°), with a melting fraction of 12 % at t = 2 h for β = 0° compared to 40–44 % for β ≠ 0°. Nanoparticles maintain a higher electrical efficiency (11.6 %) for horizontal panels, whereas inclined panels (β ≠ 0°) experience declining electrical efficiency (7.5 % at t = 8 h). For β = 0°, the PCM system effectively maintains the surface panel's temperature constant at 44 °C for a long time (up to 8 h). However, when nano-PCM systems are introduced, this temperature stabilizes at a slightly lower value of 40 °C, representing a 4 °C reduction attributed to the presence of nanoparticles. Conversely, for β ≠ 0, the surface panel's temperature stabilizes at 44 °C for up to t = 2 h, then experiences a sharp increase, ultimately reaching 120 °C at t = 8 h, regardless of the type or absence of nanomaterials. Overall, the most effective application of nano-PCM for cooling the PV panel was predicted at a horizontal orientation of the panel, regardless of the nanomaterial type.

The quality indicators of ice cream upon the enzymatic hydrolysis of lactose

Ice cream is a popular type of dairy foods containing up to 6% of lactose. In connection with the lactose intolerance by many consumers and the possibility of its crystallization during storage of finished products, there is a need for a decrease in the content of this nutrient in the composition of ice cream. The aim of the research was to study an effect of the lactose hydrolysis process in ice cream with the fat mass fraction of 15% and different mass fractions of dry skim milk residue on technologically significant and sensory properties of its quality. The main objects of the study were samples of ice cream subjected to lactose hydrolysis at the stage of mixture maturation. The fat mass fraction in the samples was 15%, mass fractions of dry skim milk residue were 7, 10, 12 and 15%. The composition of sugars was determined by high-performance liquid chromatography, the dynamic viscosity of mixes and the consistency of ice cream by rheological methods and the dispersion of structural elements by microcopy. The effects of the mass fraction of dry skim milk residue and lactose hydrolysis on quality indicators of mixtures and ice cream were determined. As the mass fraction of dry skim milk residue rose from 7 to 15%, the residual content of lactose increased from 0.2 to 1.1%, while the dynamic viscosity of the mixture increased by 1.3 times. A decrease in the freezing point by 0.6–0.8 °C and an increase in melting resistance were also observed. The mass fraction of melt after 2 hours of holding decreased to 4.7–0.7%. Also, indicators of consistency (hardness, adhesiveness, adhesion force and rigidity) decreased by 1.1–1.7 times (upon a mass fraction of dry skim milk residue of 7 and 10%). The samples of ice cream subjected to lactose hydrolysis were characterized by a high dispersion of structural elements typical for a traditional product, and by improved texture and increased sensation of sweetness. The complex of investigations to study quality indicators of ice cream with the fat mass fraction of 15% showed that a change in the mass fraction of dry skim milk residue upon enzymatic hydrolysis of lactose results in formation of different structural-mechanical and sensory indicators that should be considered during the creation of assortment and development of formulations of low-lactose products.

Elastic limit and charging times of compressible microencapsulated phase change materials

Thermo-mechanical models of encapsulated phase change materials have been proposed throughout the literature. Heat transfer rates can be enhanced through the encapsulation of a phase change material. The improvement of heat transfer rates, constitutes a challenge that seeks to meet the energy demand in high temperature and cold energy storage applications. Thermo-mechanical models proposed in the literature, have been applied to estimate the effects of encapsulating shells on the dynamics of the phase transition and on the energy storage capacity of phase change materials. Modeling of the phase change dynamics allows to determine melting or solidification times, that constitute a key parameter in energy storage applications. Previous thermo-mechanical models constitute an attempt to understand the thermal kinetics of microencapsulated phase change materials. The mathematical models have been consistently neglecting density variations induced by the inner pressure within the encapsulating shell. In this work, a thermo-mechanical model that couples the pressure induced density changes with the elastic properties of the shell, is proposed. The effects of density changes are incorporated in the proposed model, through the compressibility of the liquid and solid phases. Three compressibility regimes are defined and significant differences in the melting dynamics between these regimes, are found. To the authors knowledge, the models found in the literature only describe the thermal kinetics of incompressible phase change materials. In this work, we consider a silicon carbide shell with a large Young’s modulus as the encapsulating material. We found that melting rates and thermal kinetics is considerably slower in phase change materials with compressible phases. The examples discussed in this work, show that melting times can be twice as long for materials with compressible phases than melting times when incompressible phases are assumed. Additionally, we found that the encapsulating shell always reaches the elastic limit at low melting fractions by assuming incompressible phases. However, when compressible phases are incorporated, a threshold thickness for which the encapsulating material will never reach the elastic limit, is found. Finally, we found that the appearance of steady states in phase change materials with incompressible phases, can reduce the thermal energy density at typical heating temperatures by as much as 30%.

Hygrothermal and energy performance assessment of a passive building wall integrating PCM and bio-based hygroscopic material

Phase change material (PCM) and hygroscopic material (HM) in building walls are promising passive technologies for temperature and humidity regulation, respectively. Integrating the two materials allows for hygrothermal environment regulation and energy savings. However, the joint effect of the temperature dependence of the HM's hygroscopic properties and the location dependence of the PCM's thermal properties has not been mentioned or demonstrated. This study experimentally assessed the hygrothermal and energy performance of a shell enclosed by a PCM-HM wall. Different wall scenarios were proposed to study the effect of the HM, PCM, and PCM's location. The results highlighted the dominance of temperature and the significance of the PCM on performance. For PCM walls, the thermal and hygric inertia were enhanced, the characteristic times of temperature/relative humidity were increased, and the variation was dampened. Under a sinusoidally varying climate, the peak temperature, thermal load, and fluctuations in temperature, relative humidity, and vapor pressure were reduced, and the peak temperature was delayed. Additionally, the repositioning of the PCM further improved the performance. When the PCM was repositioned from the outside to the middle, the temperature, relative humidity, vapor pressure fluctuations, and thermal load were reduced by 25.0 %, 45.8 %, 54.6 %, and 33.1 %, respectively, in warm to hot climates, and by 12.5 %, 63.6 %, 41.9 %, and 66.0 %, respectively, in cold to temperate climates. The PCM properties are important as the PCM in the PCM-middle wall has a higher melt fraction in the solid–liquid state, which utilizes more PCM latent heat energy and improves wall performance.

Fitting Thermal Evolution Models to the Chronological Record of Erg Chech 002 and Modeling the Ejection Conditions of the Meteorite

The history of accretion and differentiation processes in the planetesimals is provided by various groups of meteorites. Sampling different parent body layers, they reveal the circumstances of the metal–silicate segregation and the internal structures of the protoplanets. The ungrouped achondrite Erg Chech 002 (EC 002) added to the suite of samples from primitive igneous crusts. Here we present models that utilize thermochronological data for EC 002 and fit the accretion time and size of its parent body to these data. The U-corrected Pb–Pb pyroxene, Pb–Pb phosphate, and Ar–Ar ages used imply a best-fit planetesimal with a radius of 20–30 km that formed at 0.1 Ma after calcium-aluminum-rich inclusions. Its interior melted early and differentiated by 0.5 Ma, allowing core and mantle formation with a transient lower mantle magma ocean and a melt fraction of <25% at the meteorite layering depth. EC 002 formed from this melt at a depth of 0.8 km in a partially differentiated region covered by an undifferentiated crust. By simulating collisions with impactors of different sizes and velocities, we analyzed the minimum ejection conditions of EC 002 from its original parent body and the surface composition of the impact site. The magma ocean region distinct from the layering depth of EC 002 implies that it was not involved in the EC 002 genesis. Our models estimate closure temperatures for the Al–Mg ages as 1030–1200 K. A fast parent body cooling attributes the late Ar–Ar age to a local reheating by another, late impact.

Numerical Analysis of The Multilayer Structures Melting with Different Hole Network with Phase Change Material

Phase change materials (PCM) are used with different geometries to increase thermal performance. The thermal performance of the geometries on phase change materials have been investigated. For thermal energy storage systems (TES), porous structures are widely used to increase the thermal performance of the PCM. In addition, geometric parameters affect heat transfer, flow and melting solidification. In this work, the thermal performance of multilayer structures with different surface geometries and the control of the melt fraction of the PCM was investigated in terms of energy efficiency. The results were obtained by modeling the studies in the Computational Fluid Dynamics (CFD) program. The physical model was obtained by creating a multi-layer porous structure with different surface geometries in each layer thanks to the additive system. Modeling was carried out for natural convection depending on time. Paraffin was used as the PCM. The melting temperature of the paraffin used is 41 °C and the latent heat of fusion is 165 kJ/kg. In the present work, the distribution of melting isotherms gives more homogeneous results for the selected geometry. The results of PCM multilayer structure and other geometries were compared under the same conditions and it was seen that the multilayer structure improved the thermal performance. All melting graphs range from 0-1 (0: solid, 1: liquid). The results obtained for the selected geometry show that the melting value is between 0.8-0.9. In addition, the proposed physical model is a subject that can be encountered in engineering applications, thermal design engineering. In this respect, it is thought that the results obtained from the study, especially in the field of energy storage, will fill an important gap.

Electrical Response of a Reactivated Ancient Suture Revealed by Three‐Dimensional Magnetotelluric Inversion Across the Jinsha River Suture, Northern Tibetan Plateau

AbstractThe northern Tibetan Plateau offers an excellent opportunity to investigate continental collision involving the Indian and Asian plates in this remote, high‐altitude region. However, the deep structure of the region remains incomplete and controversial, which limits our understanding of the processes of continental convergence. This study presents a new 350‐km‐long magnetotelluric (MT) profile across the Northern Qiangtang and Hoh Xil terranes in the western part of the northern Tibetan Plateau to elucidate the lithospheric structure of the reactivated Jinsha River suture. We carry out a three‐dimensional inversion to acquire the electrical structure beneath the Jinsha River suture, and reveal the presence of large‐scale conductive anomalies in the middle‐lower crust of the Northern Qiangtang and Hoh Xil terranes. The high‐conductivity anomaly beneath the Jinsha River suture extends to &gt;80 km depth and is coincident with a zone of high melt fraction (&gt;5%) in the middle‐lower crust beneath the Jinsha River suture, thereby indicating that this suture has become a rheological channel. The convergence of Indian and Asian lithosphere beneath the northern Tibetan Plateau may be the driving mechanism for the reactivation of this ancient suture. Continental subduction leads to enhanced convection in the mantle. This reactivated suture, which is a tectonically weak zone, provides a conduit for the upwelling of hot mantle material to result in the subsequent melting of the middle‐lower crust. Moreover, our findings provide valuable insights into the geodynamic evolution of the northern Tibetan Plateau, as well as contribute to our understanding of continental convergence processes.

Asymmetric PCM melting and thermal convection in a rectangular enclosure with straight and wavy heat transfer passages

Experimental and numerical investigations of thermal convection in the vicinity of a straight and wavy horizontal heat transfer fluid passage (HTF)s placed in a rectangular enclosure filled with phase change material (PCM) are presented. The enthalpy-porosity-based finite volume solver is used to simulate the spatiotemporal evolution of the thermal convection, which is well-complemented by experimental visualization and thermocouple measurements. Heat transfer from the horizontal HTF exhibits asymmetrical melting. Heat diffusion is the dominating energy transfer mechanism on the bottom part of the HTF passage and is compared with the Stefan problem. The temporal evolution of thermal convection on the top part of HTF passage involves three distinct phases of melting, viz. initial conduction phase, Rayleigh–Bénard (R-B) convection with linear convection, and vortex coalescence effects. The final stage of the melting process is influenced by the topography of a peninsula of unmelt PCM, which is influenced by specific top-boundary conditions. Thermal convection in PCM above the wavy HTF passage exhibits restricted plume development leading to an improved melting rate and a higher average melt height. Augmentation of internal convection characteristics of HTF with the evolution of melting is also explored. A systematic investigation of the convection plume development and heat transfer characteristics in PCM by varying the HTF Reynolds (1700<Re<2750) and Stefan numbers (0.4<Ste<0.6) has been carried out, and analyzed the nature of thermal plumes, melt fraction, and average penetration length with the Fourier number. Additionally, novel correlations are proposed between Nusselt and Rayleigh numbers for straight and wavy tubes in the intermediate melting stage (1.3×104<Ra<4.7×107).

Thermal analysis of a cascaded latent thermal storage tank in a solar domestic water heating system

AbstractTo enhance the thermal characteristics of a solar collector storage system, this study investigates the performance of a rectangular thermal energy storage (TES) tank by incorporating cascade phase change materials (cascade‐PCMs). Three different commercially available PCMs (RT44HC, RT54HC, and RT62HC) with distinct melting temperatures are employed. These cascade‐PCMs are utilized as slabs in vertical rectangular modules, which are integrated into the water TES tank. The heat transfer fluid (HTF) in the flat‐plate solar collector captures solar energy and transfers it to the TES tank, where it is stored as latent thermal energy. A two‐dimensional (2D) numerical model, utilizing the enthalpy‐porosity approach and conservation equations, is developed to analyze the melting and heat transfer processes within the TES tank. The model is validated against previous experimental and numerical data. Performance evaluation of the cascade‐PCMs tank is conducted during a 9‐h charging period (from 8:00 am to 5:00 pm) under Marrakesh weather conditions in Morocco. An optimization study is carried out to determine the optimal height of each cascade‐PCM. The results suggest that an optimal design with heights of 23, 16, and 11 cm for RT44HC, RT54HC, and RT62HC respectively, offers improved melting and storage quality. The thermal characteristics of the TES tank incorporating cascade‐PCMs are compared to those of a TES tank filled with a single phase change material (single‐PCM) during the charging period. The findings indicate that the cascade‐PCMs achieve complete melting, while the single‐PCM only reaches a melting fraction of 0.903 at the end of the charging process. Furthermore, the optimal configuration of the cascade‐PCMs storage tank exhibits slightly higher sensible and latent thermal energy storage capacity compared to the single‐PCM tank. The combination of the solar collector with the cascade‐PCMs storage tank results in a 3.47% higher average collection efficiency when compared to the single‐PCM tank.

A bimodal source for the generation of tonalitic to granitic magmas in a non-subduction-related magmatic belt: An example from the Sierra Chica of Córdoba, Argentina

A notable consensus prevails about the hybrid nature of intermediate calc-alkaline magmatism. Accordingly, petrogenetic models envisage the addition of young mantle material and cortical recycling in those geological settings where intermediate magmas are dominant. Most exhaustively studied examples are: 1) magmatic arcs associated with subduction zone settings where oceanic crust and sediments are introduced into the mantle wedge, and 2) deep crustal sections are pervaded by hot, H2O-rich mantle-derived liquids. Nevertheless, back-arc or foreland terranes of several hundred kilometers in width, frequently characterized by high heat flux, crustal melting, recycling and melt fractionation, are crucial areas to evaluate the generation of intermediate magmatism. The Sierra Chica of Córdoba (Argentina) provides an excellent example to study these processes. The high-grade crustal segment shows metamorphosed pelitic and basaltic protoliths that were part of an old sedimentary succession. We evaluate the evolution of this bimodal source during two consecutive early Paleozoic orogenic periods when it was established as the source area of intermediate to silicic magmatism far from the contemporary magmatic arcs. Field relations and new geochemical and geochronological data revealed the occurrence of two magmatic events during Cambrian and early Ordovician periods. Cambrian migmatization and partial melting (∼528 to 505 Ma) is represented by irregular-shaped monzogranites and tonalites, while early Ordovician magmatism (∼480 Ma) is characterized by dyke-shaped pegmatites and tonalite-trondhjemites. The preservation of two contrasting igneous lineages suggests a genetic linkage between metapelitic and amphibolitic migmatites and between granitic and tonalitic-trondhjemitic partial melts. Coeval with this magmatism, Famatinian tonalitic-trondhjemitic to monzogranitic magmas intruded upper crustal levels in Sierra Chica and other parts of Sierras of Córdoba. Geochemical signatures point to a bimodal (mafic/felsic) source for this intermediate to silica-rich magmatism. The evolution of partial melts studied in the Sierra Chica is depicted on the basis of geochemical projections with fractionation and hybridization models, in order to establish the primary liquids of this Famatinian magmatic belt. Trends defined by Famatinian tonalites, trondhjemites and granodiorites suggest that primary Ca-rich melts (tonalites and trondhjemites of this study) evolved through fractionation of plagioclase (30–50 vol%) compatible with the preservation of inferred co-magmatic Pl-cumulates within these plutonic bodies. Peraluminous granites and monzogranites can be explained by a simple restite unmixing process involving alkali-rich liquids generated in the metapelitic part of the source. The addition (hybridization) of up to 30 vol% of granitic melts to the tonalite-trondhjemite end-member may account for the composition of other Famatinian granodioritic to monzogranitic intrusive rocks from the plutonic belt. The crustal segments of the Sierra Chica have undergone metamorphism and partial melting in out-of-arc settings: the Cambrian fore-arc and the early Ordovician back-arc. The voluminous magmatic belt rooted in the paired metapelitic-amphibolic source area is involved in the origin of intermediate to silicic Famatinian magmatism without significant mass transfer from the mantle and crustal growth, instead it is dominated by crustal melting, recycling and fractionation.

Syn‐Rift Magmatism and Sequential Melting of Fertile Lithologies in the Lithosphere and Asthenosphere

AbstractThe timing and rate of decompression melting of a compositionally heterogeneous mantle during continental rifting are assessed with a new one‐dimensional geodynamic code, MELT1D. MELT1D computes pressure and temperature in the extending lithosphere and rising asthenosphere and calculates the resulting melt fraction and eruption rates for different lithologies. A series of models simulate syn‐rift melt production from (a) dry and wet depleted lherzolite similar to the mantle that underlies most mid‐ocean ridges, (b) dry and wet relatively fertile ultramafic compositions representing plume or primitive mantle material, (c) pyroxenite representing recycled ultramafic oceanic crust or magmatic metasomes, and (d) basalt representing recycled mafic crust or metasomes. The models predict sequential melting of the different compositions that is broadly consistent with basalt eruption histories in many Phanerozoic rifts. Results show a progressive transition in magma sources as the lithosphere thins, beginning with melting of wet mantle and compositionally fertile mafic components near the lithosphere‐asthenosphere boundary during the earliest stages of extension. This transitions to magmatism dominated by melting of relatively fertile ultramafic components (pyrolitic and pyroxenitic compositions) as extension progresses, and finally to melting of ambient lherzolite asthenosphere as lithosphere thinning approaches breakup. Mantle composition, pre‐rift lithosphere thickness, and mantle temperature exert the greatest controls on the timing and volumes of magmas produced from each lithology. In general, a cool or thick lithosphere has a greater capacity to sequester fertile lithologies than thin or warm lithosphere, and thus has a greater capacity to produce early syn‐rift magmas without requiring a hot mantle plume.