Laboratory Heating Research Articles

Influence of prior microstructure on the mechanical and microstructural properties of C–Mn–B steel after spheroidizing annealing

ABSTRACT During spheroidizing annealing of steels, the carbide shape is modified from lamellar to spheroidal for increasing cold deformability. The aim of this work is to study the kinetics and the mechanical properties of a C–Mn–B steel grade after spheroidizing annealing, varying the prior microstructure produced by industrial conventional and thermo-mechanical hot rolling with different Stelmor cooling rates. Moreover, different prior microstructures were also produced by laboratory heat treatments. Microstructural analysis, hardness tests, and tensile tests were carried out at different soaking times. The results show that a better distribution of the carbon in the metal matrix obtained in bainitic and martensitic microstructures results in a more uniform dispersion of the carbides with higher mechanical resistance and deformability. The ferritic and pearlitic microstructures obtained by thermo-mechanical hot rolling are able to produce more homogeneous carbides when compared with the traditional hot rolling.

Fracture toughness of coarse-grain heat affected zone of quenched and tempered CrMo steels with internal hydrogen: Fracture micromechanisms

The determination of fracture behaviour of welds in presence of internal hydrogen is essential for the integrity assessment of CrMo vessels and pipes working under high hydrogen pressures. Homogeneous coarse-grain tempered bainitic/martensitic microstructures were obtained in 42CrMo4 and 2.25Cr1Mo steels by means of laboratory heat treatments in order to reproduce the coarse grain heat affected zone (CGHAZs) of real welds. Afterwards, the fracture toughness behaviour of the simulated CGHAZs was assessed under low displacement rate J-fracture tests, using pre-charged (in hydrogen gas) CT specimens. The hydrogen embrittlement (HE) experienced by the CGHAZs of both steels was considerably greater than in the base steels. The greater hardness, i.e. higher dislocation density, characteristic of the CGHAZ microstructures, explains the more strongly trapped hydrogen, and hence the sharper drop in the fracture toughness, also associated to an increase of intergranular fracture micromechanisms. Scanning electron microscopy examination of the fracture surfaces revealed the action of hydrogen-enhanced localized plasticity (HELP) mediated hydrogen-enhanced decohesion (HEDE) micromechanism, in which HELP took place first, providing enough hydrogen in the process zone to modify the local resistance, and eventually weakening the cohesion of the internal interfaces, HEDE.

Energy and Exergy Analysis of Low-Global Warming Potential Refrigerants as Replacement for R410A in Two-Speed Heat Pumps for Cold Climates

Heat pumps (HPs) are being developed with a new emphasis on cold climates. To lower the environmental impact of greenhouse gas (GHG) emissions, alternate low global warming potential (GWP) refrigerants must also replace the exclusive use of the refrigerant R410A, preferably without re-engineering the mechanical hardware. In this paper, we analyze the performance of four low-GWP alternative refrigerants (R32, R452B, R454B, and R466A) relative to the conventional R410A and draw conclusions on the relative performances for providing heating in cold climates based on the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 210/240 standard for two-speed heat pumps. The simulations are carried using the Department of Energy, Oak Ridge National Laboratory (DOE/ORNL) Heat Pump Design Model (HPDM), a well-known heating, ventilation, and air conditioning (HVAC) modeling and design tool in the public domain and the HVAC research and development community. The results of the simulation are further scrutinized using exergy analysis to identify sources of systemic inefficiency, the root cause of lost work. This rigorous approach provides an exhaustive analysis of alternate low-GWP refrigerants to replace R410A using available compressors and system components, without compromising performance.

The Effect of He-Ne laser Radiation and Temperature of Blood in Vitro on the Erythrocytes Sedimentation Rate Values in Healthy People

Background : The aim of this study is to research the in vitro effect of  the He-Ne laser radiation and study the effect of environmental temperature on Erythrocyte Sedimentation Rate (ESR) in blood samples from healthy . Objective : To show the effect of He-Ne laser and effect of environmental temperature on Erythrocyte Sedimentation Rate (ESR) Subject & Methods : He-Ne laser wave length of 632.8ηm was used for irradiation with 0.5mm diameter beam spot on blood samples, with power density  1mw/cm2 , The irradiation times were (1hr ) , The samples of blood were obtained  30 contributors and each sample was separated into three samples for irradiation and control . Results : The results showed that there were significant differences in the values of sedimentation rates for both class (25 -45 ) 0c degree heat compared with the values of sedimentation 25 0c degree heat temperature for irradiation and control . It shows the effect of temperature factor on the red blood cells sedimentation rate in blood samples from healthy people and see the effect of the degree of laboratory heat due to lack of efficient heating and cooling devices in the summer and winter on the sedimentation rates of values to be taken into consideration with the results . Conclusion :The change of temperature (high and low) has a great effect on the deposition and precipitation of red blood cells in health people and thus must be taken into consideration and this effect is also observed with the use of He - Ne laser at a temperature of 25 ° C.

Single Phase Oxidation of Ferrimagnetic Grains as a Cause of L-Shaped Arai–Nagata Diagrams

Abstract—The experiments on the determination of paleointensity Banc of the Earth’s magnetic field by Thellier method on basalts of the Berd (Jurassic) and Paravakar (Cretaceous) collections sampled in the northeastern Armenia in 2006 revealed an anomalous behavior of the Arai–Nagata diagrams. The anomaly manifests itself by a sharp drop in the intensity of natural remanent magnetization (NRM) under heating of samples to about 400°C, which is accompanied by a very weak acquisition of partial thermoremanent magnetizations (pTRMs) in this temperature interval. The further increase in temperature leads to the opposite phenomenon—an unexpectedly sharp rise in pTRMs intensity with almost no decrease in NRM, which creates the L-shape of the Arai–Nagata diagram. A similar phenomenon of a steep decline during thermal demagnetization was also established for remanent saturation magnetization Mrs(T). We carried out a number of magnetomineralogical experiments from which we conclude that, consistent with the hypothesis suggested by (Kosterov and Prevot, 1998), the sharp drop in Mrs(T) and NRM(T) curves is caused by the transitions of the domain state from a metastable configuration to a more stable one. These transitions are initiated by the processes of single- and heterophase oxidations of primary titanomagnetites under the laboratory heating of samples to moderate temperatures.

Signatures of the post-hydration heating of highly aqueously altered CM carbonaceous chondrites and implications for interpreting asteroid sample returns

The CM carbonaceous chondrites have all been aqueously altered, and some of them were subsequently heated in a parent body environment. Here we have sought to understand the impact of short duration heating on a highly aqueously altered CM through laboratory experiments on Allan Hills (ALH) 83100. Unheated ALH 83100 contains 83 volume per cent serpentine within the fine-grained matrix and altered chondrules. The matrix also hosts grains of calcite and dolomite, which are often intergrown with tochilinite, Fe(Ni) sulphides (pyrrhotite, pentlandite), magnetite and organic matter. Some of the magnetite formed by replacement of Fe(Ni) sulphides that were accreted from the nebula. Laboratory heating to 400 °C has caused partial dehydroxylation of serpentine and loss of isotopically light oxygen leading to an increase in bulk δ18O and fall in Δ17O. Tochilinite has decomposed to magnetite, whereas carbonates have remained unaltered. With regards to infrared spectroscopy (4000–400 cm−1; 2.5–25 µm), heating to 400 °C has resulted in decreased emissivity (increased reflectance), a sharper and more symmetric OH band at 3684 cm−1 (2.71 µm), a broadening of the SiO stretching band together with movement of its minimum to longer wavenumbers, and a decreasing depth of the MgOH band (625 cm−1; 16 µm). The SiO bending band is unmodified by mild heating. With heating to 800 °C the serpentine has fully dehydroxylated and recrystallized to ∼Fo60/70 olivine. Bulk δ18O has further increased and Δ17O decreased. Troilite and pyrrhotite have formed, and recrystallization of pentlandite has produced Fe,Ni metal. Calcite and dolomite were calcined at ∼700 °C and in their place is an un-named Ca-Fe oxysulphide. Heating changes the structural order of organic matter so that Raman spectroscopy of carbon in the 800 °C sample shows an increased (D1 + D4) proportional area parameter. The infrared spectrum of the 800 °C sample confirms the abundance of Fe-bearing olivine and is very similar to the spectrum of naturally heated stage IV CM Pecora Escarpment 02010. The temperature-related mineralogical, chemical, isotopic and spectroscopic signatures defined in ALH 83100 will help to track the post-hydration thermal histories of carbonaceous chondrite meteorites, and samples returned from the primitive asteroids Ryugu and Bennu.

Small-angle neutron scattering (SANS) characterization of 13.5 Cr oxide dispersion strengthened ferritic steel for fusion applications

Abstract Small-angle neutron scattering (SANS) has been utilized for micro-structural investigation on laboratory heats of oxide dispersion strengthened (ODS) 13.5 Cr wt % ferritic steel, with 0.3 wt% Y2O3 and with variable Ti and W contents. The results show that increasing the Ti content from 0.2 to 0.4 wt% a distribution of nano-clusters develops, tentatively identified as Y2Ti2O7, with average radii as small as 6.5 A and volume fractions increasing from 0.021 to 0.032. The measured SANS cross-sections show also the growth of much larger defects, possibly Cr oxides. Furthermore, the ratio of magnetic to nuclear SANS components shows that the defect composition varies both with their size and with the Ti and the W content. These results are in qualitative agreement with transmission electron microscopy (TEM) observations, showing a striking influence of Ti addition on particle size refinement. However, while TEM is limited in statistics and minimum observable size of the Ti-rich nano-clusters, the defect distributions obtained by these SANS measurements provide complementary information useful for morphological characterization of the micro-structure in the investigated material.

Metal-hydride hydrogen compressors for laboratory use

The development of commercial applications of hydrogen at high pressure (300–700 + bar), for example in fuel cell vehicles and associated filling stations, necessitates the study of hydrogen capacity, and the safety of materials at pressures well above that of standard pressurised cylinders employed in research laboratories. This, in turn, requires laboratory instruments to have some mechanism for hydrogen compression as part of their operation. In this study, the use of metal-hydride compressors for laboratory applications is explored and evaluated. The reduced operating requirements of laboratory instruments, relative to industrial compressors, and the ready availability of laboratory heating and cooling methods, allows the use of relatively simple, single-stage metal-hydride compressors. A simple theoretical derivation enables the determination of the size and amount of hydrogen storage alloy required for a desired pressure, given the experimental volume to be pressurised. Practical requirements, both in terms of the hydrogen storage alloy, and of the pressure vessel, are discussed. Examples of working compressors for both manual operation to 1000 bar, and automated operation to 100 bar, under computer control, are also given.

Pathways for 39Ar loss during step-heating of alkali feldspar megacrysts from the Shap granite (UK): Combined evidence from diffusion experiments and characterisation of heating-induced texture modifications

This study aims to identify the dominant fast pathways for 39Ar loss during step-heating 40Ar/39Ar analysis of alkali feldspar from the Shap granite (UK). In our analysis we combined step-heating 40Ar/39Ar data acquired from variably sized feldspar fragments (0.4 to 2.2 mm in the shortest dimension) and optical and electron microscopy observations of microtextural modifications caused by heating in a muffle furnace in air. Our optical and electron microscopy results suggest that laboratory heating of the Shap feldspar causes it to fracture. The resulting cracks form an interconnected network, which may link with some of previously documented nanoscale defects such as nanotunnels, slots, pull aparts and bubbles. Our step-heating 40Ar/39Ar analyses yielded non-linear Arrhenius trajectories of 39Ar release. The non-linearity is best explained by heating-induced reduction of the effective diffusion length due to fracturing, likely with some contribution from nanotunnels, pull-aparts, slots and bubbles. Incoherent grain boundaries apparently played a minor role in providing fast pathways for 39Ar loss, if any. Importantly, unambiguous evidence for a reduction of the diffusion length during step-heating was only observed in experiments with large fragments (≥1 mm in the shortest dimension). The Arrhenius trajectory obtained from the smaller fragments (≤0.5 mm in the shortest dimension) appears to be consistent with the presence of variably-sized non-interacting intra-grain diffusion domains that existed prior to mineral separation. Heating-induced fracturing must be taken into account when interpreting 40Ar/39Ar dates of alkali feldspar, with particular focus on the following two points. First, this process is clearly inconsistent with the underlying assumptions of commonly utilised multi-diffusion domain (MDD) theory, although it can result in 39Ar release patterns that appear consistent with them. Therefore, it is important to identify on a case by case basis the dominant fast pathways for 39Ar loss from alkali feldspar during step-heating before applying MDD theory. Second, if heating-induced fracturing is ubiquitous in alkali feldspar and affects even gem-quality samples, then presently available diffusion parameters of Ar in alkali feldspar structure may be inaccurate to some degree, since all of them were obtained without considering the presence of cracks.

Hydrogen embrittlement of the coarse grain heat affected zone of a quenched and tempered 42CrMo4 steel

The coarse grain heat affected zone (CG-HAZ) of welds produced in a quenched and tempered 42CrMo4 steel was simulated by means of a laboratory heat treatment consisting in austenitizing at 1200 °C for 20 min, oil quenching and finally applying a post weld heat treatment at 700 °C for 2 h (similar to the tempering treatment previously applied to the base steel). A tempered martensite microstructure with a prior austenite grain size of 150 μm and a hardness of 230 HV, similar to the aforementioned CG-HAZ weld region, was produced. The effect of the prior austenite grain size on the hydrogen embrittlement (HE) behaviour of the steel was studied comparing this coarse-grained microstructure with that of the fine-grained base steel, with a prior austenite grain size of 20 μm.The specimens used in this study were charged with hydrogen gas in a reactor at 19.5 MPa and 450 °C for 21 h. Cylindrical specimens were used to determine hydrogen uptake and hydrogen desorption behaviour. Smooth and notched tensile specimens tested under different displacement rates were also used to evaluate HE.Embrittlement indexes, EI, were generally quite low in the case of hydrogen pre-charged tensile tests performed on smooth tensile specimens. However, very significant embrittlement indexes were obtained with notched tensile specimens. It was observed that these indexes always increase as the applied displacement rate decreases. Moreover, hydrogen embrittlement indexes also increase with increasing prior austenite grain size. In fact, the embrittlement index related to the reduction in area, EI(RA), reached values of over 20% and 50% for the fine and coarse grain size steels, respectively, when tested under the lowest displacement rates (0.002 mm/min).A comprehensive fractographic analysis was performed and the main operative failure micromechanisms due to the presence of internal hydrogen were determined at different test displacement rates. While microvoids coalescence (MVC) was found to be the typical ductile failure micromechanism in the absence of hydrogen in the two steels, brittle decohesion mechanisms (carbide-matrix interface decohesion, CMD, and martensitic lath interface decohesion, MLD) were observed under internal hydrogen. Intergranular fracture (IG) was also found to be operative in the case of the coarse-grained steel tested under the lowest displacement rate, in which hydrogen accumulation in the process zone ahead of the notch tip is maximal.

Continuous Casting Secondary Cooling: Laboratory Heat Transfer Measurements and Accuracy Considerations by Comparison with the Real Situation

In secondary cooling of continuous casting, it is very important to know the cooling heat flux for the actual spray cooling situation with respect to various parameters like the local position, the nozzle types, distances, and the water and air flow rates, to be able to control the cooling conditions precisely. As heat flux measurements on a casting machine are too challenging, experimental laboratory test rigs are designed and used for measurements by different research groups. Therefore, metal probes of different dimensions and materials are heated up to the desired temperature and then exposed to spray nozzles. The heat flux is usually measured by temperature sensors immersed in the probe body, and then determined from the measured temperature using inverse modelling methods. Herein, the differences between the real and laboratory conditions are focused on using a mathematical heat transfer simulation model. The influence of strand surface temperature, nozzle spray water flow conditions, and Leidenfrost effect are pointed out. A procedure to use heatflux data measured on a test rig for cooling control on a real caster despite the different conditions is proposed.

The magnetization of the ocean floor: stress and fracturing of titanomagnetite particles by low-temperature oxidation

SUMMARY The natural remanent magnetization (NRM) of the ocean floor is carried by titanomagnetite grains that undergo low-temperature oxidation after initial cooling. Progressing oxidation is known to generate shrinkage cracks in grains larger than approximately 5 μm, and is suspected to control the long wavelength variation of NRM-intensity across the ocean floor. Here we develop a quantitative theory of single-phase oxidation and crack formation by solving the vacancy-diffusion equation that describes the oxidation process for spherical titanomagnetite particles, where the diffusion coefficient strongly decreases with vacancy concentration. The latter dependence has been experimentally demonstrated and is essential to explain the peculiarities of the observed variations of oxidation-degree with ocean-floor age. The calculated diffusion profiles provide the exact stress distributions inside oxidized titanomagnetite spheres, and predict a size limit for shrinkage-crack formation that agrees with microscopic observations of crack appearance in ocean-floor basalt samples. The new diffusion model provides a unified explanation of long-known experimental facts that (1) temperatures for the onset of low-temperature oxidation during laboratory heating are theoretically estimated as 200–400 ○C, depending on grain size and (2) that heating to 400–500 ○C is required to obtain a sufficiently high degree of oxidation z ≈ 0.8 for the development of high-temperature exsolution lamellae. Calculations for ocean-floor conditions quantitatively suggest that a rapid decrease of NRM intensity during the first 40 ka results from a deflection of magnetization by strong stresses that emerge in titanomagnetite grains of subcritical sizes, and randomization of domain-state by crack formation in larger grains.

Real-world application of machine-learning-based fault detection trained with experimental data

Buildings are responsible for a large portion of the overall energy consumption. With the rising penetration of renewable energies, the heating and cooling demand of buildings will be increasingly satisfied by heat pumps. However, faults in the heat pump systems reduce energy efficiency or cause system failure, leading to an increased demand for primary energy. Hence, fault detection algorithms (FDA) are used to identify faults before system failure or efficiency deterioration occurs.With the rise of artificial intelligence and big data as well as more detailed monitoring systems, data-driven FDA have become a focus of research in recent years, showing promising results with acceptable effort. However, studies often use specific training data sets, thus generating FDAs adapted to a specific experimental system.In this paper, we investigate whether FDAs trained on a fault data set gathered with a laboratory heat pump system can be deployed on a real-world application system without the need for expensive modifications. We also investigate a big data approach, in which we use data collected over an extended period of time to train the FDAs.To this end, we use a data set kindly provided by the National Institute of Standards and Technology (NIST) containing data for typical heat pump failures measured on a specially outfitted air-water heat pump. From this data, we extract a series of features as input for the FDAs and evaluate the importance of those features for the FDAs. We train the algorithms to detect faults on the NIST data set, and transfer the fitted FDAs to our own measurement data.The results show that the trained FDAs perform very well on the NIST data set, but poorly on the real-world data set. We identify several reasons for the FDAs’ poor performance and derive mitigating actions. We believe that big data approaches for FDAs are facing several issues beyond the simple gathering of large data quantities, especially the labelling of occurred faults and completeness of the data set.

Hydrophobicity of peat soils: Characterization of organic compound changes associated with heat-induced water repellency

Boreal peatlands provide critical global and regional ecosystem functions including climate regulation and nutrient and water retention. Wildfire represents the largest disturbance to these ecosystems. Peatland resilience depends greatly on the extent of post-fire peat soil hydrophobicity. Climate change is altering wildfire intensity and severity and consequently impacting post-fire peat soil chemistry and structure. However, research on fire-impacted peatlands has rarely considered the influence of peat soil chemistry and structure on peatland resilience. Here we characterized the geochemical and physical properties of natural peat soils under laboratory heating conditions. The general trend observed is that hydrophilic peat soils become hydrophobic under moderate heating and then become hydrophilic again after heating for longer, or at higher, temperatures. The loss of peat soil hydrophilicity initially occurs due to evaporative water loss (250 °C and 300 °C for <5 min). Gently but thoroughly dried peat soils (105 °C for 24 h) also show mass losses after heating, indicating the loss of organic compounds through thermal degradation. Gas chromatography-mass spectrometry (GC–MS) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the chemistry of unburned and 300 °C burned peat soils, and various fatty acids, polycyclic compounds, saccharides, aromatic acids, short-chain molecules, lignin and carbohydrates were identified. We determined that the heat-induced degradation of polycyclic compounds and aliphatic hydrocarbons, especially fatty acids, caused dried, hydrophobic peat soils to become hydrophilic after only 20 min of heating at 300 °C. Furthermore, peat soils became hydrophilic more quickly (20 min vs 6 h) with an increase in heat from 250 °C to 300 °C. Minimal structural changes occurred, as characterized by BET and SEM analyses, confirming that surface chemistry, in particular fatty acid content, rather than structure govern changes in peat soil hydrophobicity.

Effect of Silicon and Retained Austenite on the Liquid Metal Embrittlement Cracking Behavior of GEN3 and High-Strength Automotive Steels

GEN3 steels are a new family of automotive sheet steels developed and commercialized in the last three years, specifically for body-in-white applications. The high ductility in GEN3 steels is typically achieved through the transformation-induced plasticity (TRIP) effect by the addition of silicon or aluminum. When these steels are formed into parts, the TRIP effect of austenite to martensite transformation provides enhanced ductility. Typically, 10 to 12 micrometers of zinc coating (known as galvanized coating) is applied to automotive steel sheets for corrosion protection. Liquid metal embrittlement (LME) cracking can occur during resistance spot welding (RSW) of galvanized steels. LME cracking occurs when molten zinc penetrates prior austenite grain boundaries of the steel substrate. The precise role of silicon in the LME cracking behavior in TRIP and GEN3 steels is unknown. Therefore, a study was undertaken to examine the role of silicon in LME cracking behavior of GEN3 steels. The purpose was also to examine if the presence of retained austenite is required for LME cracking to occur. In this study, laboratory heats were prepared using three silicon levels. Samples cut from galvanized panels were welded using a resistance spot welding machine, and weld areas were examined metallographically for the presence of LME cracks. Gleeble® simulations were done to study the LME behavior of the three steels prepared. Base materials were examined with a scanning electron microscope using the electron back-scattered diffraction (EBSD) method to examine the nature of grain boundaries found. The effect of retained austenite in LME cracking was studied using the Gleeble®. Both RSW and Gleeble® results showed silicon promotes LME cracking in steels, predominantly in the weld heat-affected zones(HAZs). More low-energy, low-coincidence site lattice (CSL) boundaries were found as the silicon content of the steel was decreased. These boundaries do not host cracks. Higher silicon appeared to shrink the safe temperature range over which LME cracks could be avoided, thus indicating heat in-put control to limit cracks has limited windows as the silicon in steel goes up. It was shown that the presence of retained austenite in steel is not a prerequisite for LME cracking to occur.

Improvement in the wear resistance of a hypereutectoid rail via heat treatment

The rail, as the most important component in railways, needs to be routinely checked to maintain proper service conditions to prevent catastrophic accidents by any premature failure of the rail. The severe plastic deformation of rails due to cyclic wheel/rail contact forces forms a superficial deformed layer, referred to as the white etching layer, because of cementite decomposition and the formation of the carbon-supersaturated nanostructured ferrite phase. This supersaturated superficial layer is highly prone to the initiation and propagation of rolling contact fatigue cracks. However, it has been observed that transition carbides and cementite can precipitate when the first and third stages of tempering starts at approximately 150 and 400 °C, respectively, due to carbon ejection from the body-centered tetragonal structure. A controlled laboratory heat treatment was conducted on a used hypereutectoid rail at 200 and 500 °C. Then, the wear resistances of the heat-treated samples were compared with the as-received rail sample using pin-on-disc testing. A significant increase in the wear resistance of the sample treated at 200 °C confirmed the improvement in the wear resistance of used pearlitic rails, which is a great interest for railway industries.

Experimental Evaluation of Remanence Carriers Using the Microcoercivity‐Unblocking Temperature Diagram

AbstractKnowledge of remanence carriers in recording media is crucial for obtaining reliable paleomagnetic data. In this paper, we report a newly developed technique to determine remanence carriers in natural rock samples that uses anhysteretic remanent magnetization (ARM) spectra in the microcoercivity (hc) and unblocking temperature (TUB) planes. The distribution of ARM carriers was determined via systematic stepwise demagnetization experiments of ARM combining thermal demagnetization and alternating field demagnetization treatments and calculating the change in ARM intensity on the hc‐TUB plane (hc‐TUB diagram). Samples from three basaltic lavas and two welded tuffs were analyzed. Combining the hc‐TUB diagram with the change in ARM coercivity spectra, both decreases and increases in magnetic minerals due to the thermal alteration during laboratory heating could be identified. From experimental samples, ARM carrier components were identified as being original rather than produced as a result of thermal alteration. In the case of the Izu‐Oshima 1986 A lava flow (1986La) sample, it was confirmed from the hc‐TUB diagram that high‐hc components can be separated using stepwise alternating field demagnetization treatment but not stepwise thermal demagnetization treatment. Paleointensity experiments were also conducted on Izu‐Oshima 1986 A lava flow samples. Two of the three paleointensity estimates were greater than the expected field intensity, suggesting a certain rock‐magnetic property that affects the paleointensity estimation. The hc‐TUB diagrams of the Izu‐Oshima 1986 A lava flow samples suggest that the differences in the paleointensity estimates were likely caused by different degrees of the high‐temperature oxidation state.

The Stability of Titanomagnetite Basalt of the Red Sea during Heating in Air and Argon

To optimize heating conditions during the Thellier procedure and to improve the reliability of paleofield determination, thermal stability experiments with titanomagnetite and titanomaghemite obtained by laboratory heating were conducted. The experiments were performed on P72/2 and P72/4 basalts of the rift zone of the Red Sea that contain titanomagnetite with a concentration of the magnetite component equal to (44.7 ± 3.9)% and (46 ± 5)%, respectively. It has been shown that the single-phase oxidation process prevails in annealing of titanomagnetite for 10 hours in a temperature range of 290–410°C in air. An increase in the annealing temperature up to 460–535°C means that single-phase oxidation is replaced by oxi-exsolution. The temperature range of thermal stability of the single-phase oxidized titanomagnetite expands with the degree of oxidation. In particular, at an oxidation state close to 0.9, titanomaghemite is stable up to temperatures of 410–460°C. The use of the Thellier technique for studying the properties of the chemical remanent magnetization of single-phase oxidized titanomagnetite with an oxidation state above z ≥ 0.6 is limited to approximately 20% of its value. It is possible to stabilize the single-phase oxidized state of titanomagnetite at temperatures above 460°C and thereby to improve the quality of CRM research using the Thellier method by adjusting the value of the oxygen partial pressure.

Transient heat transfer analysis in packed beds: Entropy generation model and multi-objective optimization

Due to the important role of the unsteady heat transfer process of packed beds in industrial production, the construction of the transient heat transfer model is of great significance for the operation and optimization. The present study performs a transient thermal analysis of packed bed, in which the convective heat transfer and conductive thermal resistance within the particles are considered simultaneously. A mathematical model is established of the total entropy generations (0−t) contributed by viscous dissipation and heat transfer; the influence of particle diameter, air flow rate, and pressure drop, is then investigated. Because of the time cost, these results present some different trends from the steady-state process. Furthermore, for a laboratory heat transfer system, with the aid of the genetic algorithm we adopt a multi-objective genetic algorithm model and modified expressions of the entropy generations are set as objective functions. Finally, optimal operational and structural parameters are obtained for different fan power settings. When the fan power is 300 W, the optimal particle diameter and inlet wind speed are 14 mm and 2.4 m/s, respectively. The results also suggest that the time cost is reduced with increasing fan power consumption.

Non-uniform temperature distribution's impact on downhole weight on bit (DWOB) measurement and the novel compensatory method

Non-uniform temperature distribution of DWOB measuring devices has a great effect on the accuracies of weight on bit (WOB) readings. To study the influence, two types of non-uniform temperature distributions of the WOB measuring device were created. The relationship between the two temperature distributions was studied with the further transform of heat conduction formulas. Then the strain of the measuring device was acquired under the two temperature distributions. And the relations of the strain in the two conditions was obtained with the further transform of compatibility equations and constitutive equations. To quantify the influence of non-uniform temperature distribution, a contrast simulation without non-uniform temperature distribution was carried out. The simulated results showed that the WOB errors were 9.33 kN and 46.25 kN. This paper proposed a novel compensating method based on the deduced relationships above, with which the WOB error was eliminated to 0.4 kN. To further validate the new method, the laboratory heating and cooling experiments were carried out. The experiment showed that the biggest WOB error was eliminated to 1.7 kN while the original error was up to 60 kN. Then a field experiment was conducted. Eight connection processes are chosen to further elaborate the temperature difference's impact and the related compensatory method. The economic loss caused by the WOB measuring inaccuracy was calculated, which was up to 1.17% of the drilling cost per meter. The work presented herein can serve as guidance for the DWOB measurement.