Bulk Temperature Research Articles

VEXLPE friction studied with a multidirectional hip joint simulator using contact temperature control

Frictional torque of VEXLPE and UHMWPE acetabular liners against CoCr and ZTA femoral heads was measured with a multidirectional hip joint simulator for a wide range of diameters. Measured frictional torque varied from 1 Nm to 7 Nm. The contact temperature was estimated with a subsurface thermocouple within the liner, located near the contact surface. When the estimated contact temperature was 37 °C, the lubricant bulk temperature was 30.1 ± 1.1 °C. When the lubricant bulk temperature was 37 °C, the estimated contact temperature was 43.4 ± 1.1 °C. The custom to use 37 °C as the lubricant bulk temperature in wear testing may lead to overheating of the contact and unrealistically low wear rates, as indicated by recent studies.

Significance of adiabatic heating on phase transformation in titanium-based alloys during severe plastic deformation

Experiments were conducted on Ti-based alloys including a commercially pure titanium (α phase), Ti-6Al-4 V (α + β phase) and TiNi (B19’-martensitic phase) alloys in order to investigate the phase transformation during high-pressure torsion (HPT) at room temperature. An allotropic α to ω phase transformation in the commercially pure titanium occurred during HPT processing but increasing the rotation speed led to a decrease in the volume fraction of the ω-phase. This procedure facilitates the loss of the β phase in the Ti-6Al-4 V alloy and promotes a B19’ to B2 (austenite) phase transformation in the TiNi alloy. The results show that the bulk temperature increment in the processed specimens was not sufficiently high to affect phase transformations. However, the calculations by assuming adiabatic conditions revealed that the local temperature increment is responsible to encourage or suppress the phase transformation in the Ti-based alloys. This fundamental understanding of phase transformations during severe plastic deformation is useful for conducting microstructure engineering of Ti-based alloys by tailoring the microstructures containing different phases and thereby producing different mechanical and functional behaviors.

The Temperature and Composition of the Mantle Sources of Martian Basalts

AbstractThe composition of basaltic melts in equilibrium with the mantle can be determined for several Martian meteorites and in‐situ rover analyses. We use the melting model MAGMARS to reproduce these primary melts and estimate the bulk composition and temperature of the mantle regions from which they originated. We find that most mantle sources are depleted in CaO and Al2O3 relative to models of the bulk silicate Mars and likely represent melting residues or magma ocean cumulates. The concentrations of Na2O, K2O, P2O5, and TiO2 are variable and often less depleted, pointing to the re‐fertilization of the sources by fluids and low‐degree melts, or the incorporation of residual trapped melts during the crystallization of the magma ocean. The mantle potential temperatures of the sources are 1400–1500°C, regardless of the time at which they melted and within the range of the most recent predictions from thermochemical evolution models.

Hydrate Growth over a Sessile Drop of Water in Cyclopentane

Liquid cyclopentane is frequently used in hydrate formation studies as an analogue of natural gas because cyclopentane hydrates are stable above the ice melting point at ambient pressure. In this study, hydrate growth was established on a sessile water drop of 11 mm in diameter and 4.5 mm in height (volume of 0.25 mL) immersed in liquid cyclopentane. The hydrate formation mechanism and growth processes were observed optically over an extended range of subcooling temperatures from 5.1 to 15.2 °C, with the cyclopentane bulk temperature maintained in different experimental runs between 2.6 and −7.5 °C. Qualitative and quantitative comparisons were performed to confirm the absence of ice freezing during hydrate formation, and thus, the lack of contamination of the latter from the former in the experiments. Different transformations in the hydrate film morphology were registered from macroscopic observation over the considered range of subcooling temperatures, with the hydrate crystals composing the film taking the form of polyhedral, dendritic, or spherulitic structures. It was also found that the hydrate growth rate varied depending on the subcooling temperature, with the variation of the growth rate as a function of this temperature changing from a power to an (approximately) linear law with an increase in the degree of subcooling. We postulate that hydrate film growth can be governed by different mechanisms, whose roles change over the range of explored subcooling temperatures.

Numerical Study of Heat Transport in Static Liquid Metal Exposed to Plasma with Magnetic Field

Suitable management of excessive heat in liquid metal is one of key roles to accomplish the proper liquid metal usage as future alternative fusion plasma facing components. In this work, theoretical heat transfer in liquid metal in contact with magnetized plasma was carried out, and a numerical solver for investigating temperature and induced velocity by j×B force has been developed. The study suggests the trends: 1. lower bulk temperature in liquid metal at which magnetic field is presented, compared to no magnetic field, by additional convection from j × B, stronger than natural convection; and 2. asymmetric temperature distribution in liquid metal along j × B.

Fast Damage-Healing of Rigid Photocuring 3D Printing Materials Capable of Directly Recycling in 3D Printing.

Rigid 3D printing materials often get defects such as cavities, voids, holes, or gaps when suffering from impact forces. Fast self-healing of these damages without bulk temperature increase is always desired. Besides, the recycling of dynamically cross-linked polymers was usually focused on solvent- or heat-assisted strategies such as compression molding and dissolution-casting, which restricts the geometrical diversity of recycled materials and may cause environmental issues. Here we report a rigid photocuring 3D printing material that can heal its cave-like damage quickly under UV light based on the dynamic urea bond. Besides, after grounding the printed objects into powders and directly refilling them into new printing resin, the re-3D printed objects show similar mechanical properties to the original materials without any post-treatment.

Canopy Phenology and Meteorology Shape the Seasonal Dynamics in Hydrological Fluxes of Dissolved Organic Carbon in an Evergreen Broadleaved Subtropical Forest in Central Japan

Seasonal variabilities in hydrological fluxes of dissolved organic carbon (DOC) and their driving factors in the evergreen broad-leaved forest are inadequately understood. To aid this understanding, we conducted a three-year study to examine seasonal changes in DOC concentration and flux in throughfall, stemflow, and litter leachate in an evergreen broad-leaved subtropical forest in central Japan. We specifically addressed (1) how DOC in different hydrological fluxes vary on a monthly to seasonal basis, and (2) how canopy phenology and meteorology shape the DOC concentration and flux of throughfall, stemflow, and litter leachate trends in this evergreen forest. Clear seasonal changes were found in throughfall and stemflow DOC concentration but not in litter leachate DOC concentration; the highest throughfall DOC concentrations were observed in spring (10.03 mg L−1 in 2017 and 9.59 mg L−1 in 2018, respectively) and the highest stemflow DOC concentrations were observed in summer (13.95 mg L−1 in 2017 and 16.50 mg L−1 in 2018, respectively). Correlation analysis revealed the monthly throughfall DOC concentration to be positively related to the dry weight of fallen leaves (r = 0.72, p < 0.05) and flowers (r = 0.91, p < 0.05). In addition, Random Forest models predicted that the dry weight of flowers was a primary driver of throughfall DOC concentration and that the DOC concentrations of stemflow and litter leachate were constrained by the throughfall DOC concentration. DOC fluxes in different hydrological flux were significantly positive related to bulk precipitation amounts and temperature. Moreover, the throughfall DOC concentration had a considerable effect on throughfall and litter leachate DOC fluxes. Over 75% of annual net tree-DOC (throughfall + stemflow) fluxes and more than 70% of the annual litter leachate DOC fluxes were produced in the flowering season. Thus, we speculated that the seasonal phenological canopy changes (leaf emergence, fallen leaves, flowering, and pollen) and the sufficient rainfall had great impacts on the amount and quality of DOC concentrations in the evergreen forest; and, furthermore, that the DOC from different forest hydrological fluxes was a significant fraction of the carbon that accumulates in soils.

CFD analysis of porous flow blockage in a gas-lift enhanced LBE-cooled fuel assembly

Porous blockage is likely to occur in wire-wrapped fuel assemblies and cause severe consequences such as overheating and mass flow decrease. In this study, flow behavior upstream, inside and downstream of the blockage is obtained for different porosities to analyse the overheating and pressure change. Additionally, the effect of reactivity feedback considering the void fraction and radial and axial power distributions on LBE-cooled porous blockage are given. It is concluded that flow separation upstream and recirculation downstream is the main reason for the overheat phenomenon due to poor convective heat transfer. Static pressure has a local rise both upstream with small porosities and in the flow recovery region downstream, while the gradient of pressure drops inside the blockage is large and begins forwards for small porosities because of flow resistance. The study of reactivity insertion reveals that although the effect of the void fraction on the reactivity and heat power is straightforward, the volume-averaged coolant and rod temperatures are virtually unaffected within 0.02 s. The wall and bulk temperature of central blockage C1 is generally higher than that of edge blockage E1.

Review on modern and future tribological directions of frictional-thermal sliding wear modeling

Mechanical wear is a tribological phenomenon that causes parts deterioration over time when they are in service. The wear causes enormous performance and economic burden on the mechanical applications, and the main aspects of mechanical designs should consider first. Mechanical wear is accelerated in the presence of high temperature that is caused by the frictional forces between the sliding surfaces. The generated temperature is classified into instantaneous (flash) and bulk. Both flash and bulk temperatures are modeled mathematically and verified experimentally. The models utilize different techniques and simplifications in order to obtain valid results. Future directions of the modeling techniques involve enhancing the collection of the experimental data as well as the incorporation of the chemical interactions.

Investigation of phase transition in the binary mixture of thermotropic liquid crystalline systems 4-(Heptylox) benzoic acid and 4-(Undecyloxy) benzoic acid using Raman and DFT studies

A binary mixture Uba@Hba of liquid crystalline systems; 4-(Undecyloxy) benzoic acid and 4-(Heptylox) benzoic acid was prepared, and their liquid crystalline properties were investigated through differential scanning calorimetry and polarized optical microscopy at the bulk level and temperature dependent Raman spectroscopic technique as well as density functional calculations at molecular level. The polarized optical microscopic studies revealed crystal, smectic A, nematic and isotropic phases in the Uba@Hba. The phase transition temperatures of the binary mixture Uba@Hba was identified by the temperature dependent Raman study which was found almost close to phase transitions observed in differential scanning calorimetry and polarized optical microscopy. The detailed Raman & DFT studies provide information occurring in phase transitions at molecular level. The changes in inter/intra-molecular interactions at crystal → smectic A and smectic A → nematic transitions have been discussed in detail.

Ni nanoparticles supported on Al2O3 + La2O3 yolk-shell catalyst for photo-assisted thermal decomposition of methane

Catalytic methane decomposition (CMD) has emerged as an appealing technology for large-scale production of H2 and carbon nanostructures from natural gas. As the CMD process is mildly endothermic, the application of concentrated renewable energy sources such as solar energy under a low-temperature regime could potentially represent a promising approach towards CMD process operation. Herein, Ni/Al2O3-La2O3 yolk-shell catalysts are fabricated using a straightforward single-step hydrothermal approach and tested for their performance in photothermal CMD. We show that the morphology of the resulting materials, dispersion and reducibility of Ni nanoparticles, and nature of metal-support interactions can be tuned by addition of varying amounts of La. Notably, the addition of an optimal amount of La (Ni/Al-20La) improved the H2 yield and catalyst stability relative to the base Ni/Al2O3 material, while also favoring base growth of carbon nanofibers. Additionally, we show for the first time a photothermal effect in CMD, whereby the introduction of 3 suns light irradiation at a constant bulk temperature of 500 °C reversibly increased the H2 yield of catalyst by about 1.2 times relative to the rate in the dark, accompanied by a decrease in apparent activation energy from 41.6 kJ mol−1 to 32.5 kJ mol−1. The light irradiation further suppressed undesirable CO co-production at low temperatures. Our work reveals photothermal catalysis as a promising route for CMD while providing an insightful understanding of the roles of modifier in enriching methane activation sites on Al2O3-based catalysts.

Electrical transport studies in Na2O and Fe2O3 containing borate glasses

A new series of (X) Na2O.(0·5−x)Fe2O3.(0·5)B2O3 of sodium and iron oxides doped borate glasses were synthesised by melt quenching. The bulk density, structural and temperature dependent electrical properties of these glasses have been investigated. The density decreased with increase in Na2O content up to Na2O=0·2 and increased thereafter. The FTIR studies indicated the presence of BO3 and BO4 groups in the network and also has shown presence of minimum NBOs at x=0·2. These results are attributed to the significant structural modifications taking place in the glass network at Na2O=0·20. The dc electrical conductivity decreased with increase in Na2O content up to Na2O=0·20 and increased for further addition of Na2O. The activation energy has increased up to 0·2 mol% of Na2O and decreased thereafter. Based on these results, it is established that at x=0·20, a changeover of dc conduction mechanism predominantly from polaronic to ionic is taking place. Mott’s SPH, Mott’s VRH and Greave’s VRH models have been used to explain the high and low temperature conductivities.

Heat transfer of hydrogen with variable properties in a heated tube

Hydrogen as a fuel or a coolant plays an essential role in carbon emission reduction and energy system transformation. There has been a long need for a better method of explaining the heat transfer mechanism for gases with variable physical properties in the past few decades. In this study, an experimental investigation was conducted to explore the heat transfer and flow friction of hydrogen in a horizontally heated tube for the following ranges: local Reynolds number from 4300 to 48600, local wall temperature up to 1200 K, local wall-to-bulk temperature ratio up to 2.37, and heat flux up to 0.57 MW/m2. The average friction coefficient equations with heat addition are developed for 6000 < Re < 105 and 1.20 < Tw/Tb < 1.85. It is found that the modified average heat transfer correlation by the acceleration parameter Kv is proposed for 4900 < Re < 44500 and 5 × 10−8 < Kv < 1 × 10−6 that can cover the laminar-turbulent transition and turbulence regime with an accuracy of ±10%. A new correlation evaluated at the bulk temperatures is proposed with the temperature and length correction to predict the local heat transfer of hydrogen, which is in good agreement with the experimental data in the range of 8000 < Re < 48000, 6.2 < x/D < 111, and 1.17 < Tw/Tb < 2.37. This investigation can facilitate improvements in thermal hydraulics analysis codes and the heat transport system with variable fluid properties.

Application of response surface methodology for the reactivity analysis of marble waste slurry collected from a marble processing unit in Western Rajasthan

The dissolution ability (reactivity) in dilute HCl solution of a marble waste (MARWAS) from Western Rajasthan (India) was studied using the RSM with CCD. The factors considered to affect the conversion of MARWAS were pH (3–7), bulk temperature (30–90 °C), agitator-speed (200–100 rpm), and particle-size of MARWAS (-25 + 10 µm). The experimental and model-predicted conversion values at the optimal conditions of pH (4.5), agitator-speed (800 rpm), temperature (60 °C), and particle-size (-25 + 10 µm) were 94.10% and 95.28%, respectively. The developed quadratic model (R2 = 0.93) can thus be employed for MARWAS reactivity prediction (<2% error) in the process designing of dissolution tanks and scrubbers.

Impacts of controlled microwave field irradiation on o-cresol and p-cresol adsorption capability of activated carbon

ABSTRACT To access the feasibility of microwave in promoting adsorbability of carbonaceous adsorbents, microwave irradiation on activated carbon (AC) was conducted at powers of 400–800 W and duration of 10 min. Accordingly, the temperature rising of AC under microwave field were studied. Moreover, the alterations in physicochemical properties of AC and impacts on cresol isomer adsorption were investigated. Results indicated that the heating curve of AC displays the initial fast temperature rising stage and the final slow stage. Additionally, the bulk temperature at irradiation terminal increases with microwave power. The temperature rising further increases the pores with a diameter range of 1.00–6.00 nm of AC; it also increases the oxygenic functional groups of AC after irradiation at 400 W and 800 W, but decreases that of AC after irradiation at 640 W. The saturation adsorption capacity of o-cresol and p-cresol on the irradiated AC rises with elevated temperature. Additionally, the cresol isomer adsorption kinetics on the irradiated AC follows the Elovich model. The above-mentioned equilibrium and kinetics suggest that the cresol isomer adsorption on the irradiated AC is dominant by chemisorption. Finally, the optimum irradiation power for o-cresol and p-cresol adsorption is 800 W and 400 W, respectively, thereby fabricating AC with developed pores and abundant oxygenic functional groups. Accordingly, the saturation adsorption capacity of o-cresol and p-cresol reaches up to 111.11 mg·g−1 and 95.97 mg·g−1, respectively. Overall, microwave irradiation is a viable option to promote cresol isomer adsorption on AC.

Experimental Investigation of Bubble Oscillation and Leaping Driven by Thermocapillary Effects with Non-condensable Gas

Boiling phase-change plays a crucial role in heat transfer as it can dissipate higher heat fluxes than single phase. Bubble nucleation, growth, motion (oscillation or leaping), coalescence and departure, govern the boiling and the heat transfer performance on wires. Many factors affect the bubble mechanisms and interactions taking place, which include the nature of the fluid, experimental conditions, thermocapillary effects, etc. This work investigates the bubble oscillation and leaping phenomena caused by thermocapillary effects in the presence of oxygen and air as non-condensable gases during boiling on a platinum micro-wire. More in particular, the bubble oscillation performance is compared under various bulk temperatures and heat fluxes for two different non-condensable gases. It is observed that for a similar fluid bulk temperature, the lower the heat flux the longer the bubble displacement. Moreover, bubble oscillation phenomenon is influenced by the concentration of non-condensable gas dissolved in the liquid showing larger harmonic periods and shorter waiting times with decrease in the contact line pinning force by approximately 7–44% in the presence of air when compared to nitrogen. Last during oscillations, bubble leaping phenomenon was observed as a consequence of the interaction between the jet flows above the oscillating bubble.

Numerical and Experimental Analysis of the ZFC Heat Release from a YBCO Bulk and Validation of YBCO Thermal Parameters

This article presents results from a simple experimental methodology used to determine the amount of heat transferred from an yttrium barium copper oxide (YBCO) bulk to liquid nitrogen (LN2) and LN2 consumption during the process of zero-field cooling (ZFC). The thermal power can be determined from the YBCO bulk temperature variation, which is difficult to measure with accuracy. In this procedure, the thermal power from the YBCO bulk to LN2 is determined from the measured rate of LN2 evaporation, considering the LN2 latent heat. To reduce the influence of room temperature heating and make the LN2 mass variation depend as much as possible on the heat released from the YBCO bulk, a step transient from room temperature into the LN2 is performed. The precision of results is determined from the rate of LN2 evaporation due to room temperature heating with the bulk already cooled by ZFC. The temperature evolution at the bulk lateral surface where the heat transfer is higher is also measured. The results from experimental measurements are compared with 3D finite element analysis (FEA) numerical results. The obtained evolutions of the temperature and thermal power from the YBCO bulk are used to validate YBCO thermal parameters, such as thermal conductivity and specific heat capacity at constant pressure. The YBCO bulk equivalent heat capacity and thermal resistance are determined by analyzing the equivalent first-order thermal lumped parameter circuit based on the obtained evolutions in time of the YBCO temperature and heat transferred to the LN2. The characteristics of dependence of the YBCO thermal resistance and heat capacity with temperature are obtained by correlating their time evolutions with the bulk average temperature evolution in time. The YBCO-specific heat capacity at constant pressure is then calculated by dividing the obtained bulk heat capacity by the bulk mass. The YBCO thermal conductivity is calculated from the obtained thermal resistance considering an equivalent bulk section and length toward the main direction of heat flux.

A simplified core catcher model for the containment code AC2/COCOSYS

In Generation 3+ NPPs such as EPR or WWER-1200 the ex-vessel core catcher presents a key component of the severe accident mitigation concept. A simplified core catcher model in the containment code COCOSYS (part of AC2 code package) is developed to consider core melt retention and cooling phenomena in core catchers for containment simulations. The model enables the characterization of the corium in the core catcher including processes in the corium conditioning phase (melting of sacrificial material in the core catcher, oxidation of metallic components, possible layer flip) and the long-term cooling phase (evolution of long-term corium pool bulk temperature and changes in physical state). The core catcher model is based on the existing molten corium / concrete interaction (MCCI) model in COCOSYS with additions for melt retention within water-cooled structures and input data can be adapted to simulate various core catcher design features of e. g. NPPs with EPR or WWER.The current state of the model, including basic assumptions, calculation methods, simplifications, and two application examples are outlined. The recalculation of the water-cooled basemat test OECD WCB-1 shows that the experimental data regarding e. g. the ablation of the sacrificial concrete on top of the water-cooled basemat, corium pool temperature and heat fluxes at water-cooled interfaces can be adequately reproduced by the COCOSYS simulation, when using empirical data for the heat transfer, including the MCCI phase. These empirical heat transfer data agree well with findings obtained from recent analytical work on MCCI tests. However, the model does not predict high local bottom plate temperatures as observed in the WCB-1 test due to a restriction of the model to quasi-steady state processes. The second calculation example demonstrates the current modelling features when applied to an axisymmetric geometry of a reactor-scale core catcher. With view to reactor-scale, the model is ready for a further verification, like e.g. comparison with other analytical core catcher approaches.

A novel integrated PDB-FDB model for the prediction of flow boiling heat transfer under high sub-cooling and very high heat flux conditions

Although numerous studies on subcooled flow boiling heat transfer have been conducted, those evaluating very high heat fluxes of several MW/m2 under one-side heating conditions are limited. In this study, the heat transfer characteristics of a circular smooth channel are evaluated under one-sided heating conditions with a high heat flux of up to 11.82 MW/m2. An experiment to measure the heat transfer (including boiling performance) from single-phase to critical heat flux (CHF) under an inlet pressure of 0.1–1 MPa, mass flux of 2000–6000 kg/m2s, and inlet bulk temperature conditions of 30–140 °C is conducted. The boiling regime is analyzed by dividing it into a partially developed nucleate boiling (PDB) regime and fully developed nucleate boiling (FDB) regime, using the onset of the nucleate boiling (ONB) point and onset of the fully developed nucleate boiling (OFDB) point. A total of 15 existing subcooled flow boiling heat transfer correlations for the PDB and FDB regimes are evaluated with the experimental results. In the PDB regime, the Liu and Winterton correlation reveal good predictability within 11%. However, all the evaluated existing correlations of the FDB regime exhibit high error rates. In this study, a new FDB correlation is developed by considering the agitation heat flux (an expected heat transfer characteristic in the FDB regime) in the Liu and Winterton correlation with Python code and the AI regression method. An evaluation of the developed correlation with the data of other previous studies, such as those of Araki et al. and Jianguo Yan et al. reveals that the newly proposed correlation can predict the FDB heat transfer under conditions of higher pressure (approximately 5 MPa) and higher flow rate (approximately 10,000 kg/m2s) with a low error rate of 17%.

Heat Transfer Analysis of Nanofluid Based Coolant Used in the Sub-Channel of Fuel Assembly of a Pressurized Water Reactor

Nano fluids are found as one of the important suspension nanoparticles in the solution that show a very significant improvement on (boiling) critical heat flux (CHF) at moderate concentrations of nanoparticles. CHF is considerate to be the maximum limit of nucleate boiling. Moreover, CHF is the most essential factor for improving the heat transfer mode, and thus the reactor performance. The goal of this study is to investigate the use of nanofluid as a component of the primary coolant in the pressurized water reactor (PWR) to improve heat transfer. This enhances the heat transfer characteristics of the reactor core and also prevents the core from melting in an emergency situation. In current and future PWRs, the nano fluid application could allow substantial power upgrades, thereby enhancing their economic efficiency. In addition, the use of nanofluids could allow as much as 20 percent increase in power density in latest generation plants without any change in the design of the fuel assembly. In this analysis, it has been found that almost 1–4% increase of Nano particle with base fluid caused a substantial escalation in heat transfer, which can reduce the overall bulk temperature and the temperature of the fuel rods as well. In addition to this, turbulent kinetic energy and velocity have been developed and investigated for different percentages of Nano fluid along the sub channel of a PWR fuel assembly, which is crucial in case of design. Overall, there has not been done much CFD based work regarding the Nano fluid application in the coolant of the sub channel, thus impact of nano fluid inclusion in the base water for heat transfer escalation inside a sub channel of a PWR is a crucial topic for investigation, in addition to this, necessary Computational Fluid Dynamics (CFD) relevant data base has been generated for further investigation. Hence, the present CFD analysis represents the novelty and uniqueness of the work for the inclusion of nanofluid with water.