Continuous Temperature Change Research Articles

Impact of different numerical approaches on the magnetocaloric effect modeling

As an ecological alternative to the conventional refrigeration technology, magnetocaloric refrigeration is still facing scientific and technological challenges hindering their application. Magnetocaloric devices rely on the magnetocaloric effect, where temperature variations result from magnetic field changes. The correct implementation of the magnetocaloric effect in numerical models is crucial before prototyping the related solutions. Here, we present a comparison between the three most used numerical methods to simulate the magnetocaloric effect: continuous temperature change, discrete temperature change step and heat source obtained from adiabatic temperature. By varying the time and space steps, it was observed that the continuous temperature change method is the most appropriate for small time steps, but has the largest computational cost. The discrete method can only be applied to small time steps, but is the fastest method. Finally, the adiabatic temperature change power source method can be applied in the entire range and is the one that presents the best results for larger time steps.

Electrolyte Chemistry toward Ultrawide-Temperature (-25 to 75 °C) Sodium-Ion Batteries Achieved by Phosphorus/Silicon-Synergistic Interphase Manipulation.

All-weather operation is considered an ultimate pursuit of the practical development of sodium-ion batteries (SIBs), however, blocked by a lack of suitable electrolytes at present. Herein, by introducing synergistic manipulation mechanisms driven by phosphorus/silicon involvement, the compact electrode/electrolyte interphases are endowed with improved interfacial Na-ion transport kinetics and desirable structural/thermal stability. Therefore, the modified carbonate-based electrolyte successfully enables all-weather adaptability for long-term operation over a wide temperature range. As a verification, the half-cells using the designed electrolyte operate stably over a temperature range of -25 to 75 °C, accompanied by a capacity retention rate exceeding 70% even after 1700 cycles at 60 °C. More importantly, the full cells assembled with Na3V2(PO4)2O2F cathode and hard carbon anode also have excellent cycling stability, exceeding 500 and 1000 cycles at -25 to 50 °C and superb temperature adaptability during all-weather dynamic testing with continuous temperature change. In short, this work proposes an advanced interfacial regulation strategy targeted at the all-climate SIB operation, which is of good practicability and reference significance.

Influence of temperature and humidity coupling on rutting deformation of asphalt pavement

Abstract In this article, ABAQUS finite-element software is used to establish an asphalt pavement structure model under high-temperature environment in summer. The changes in the temperature field and moisture concentration field of asphalt pavement are studied under the condition of 1-day continuous temperature change. The creep model is used to analyse the influence of ambient temperature and humidity on the rutting deformation of asphalt pavement. The results show that the maximum temperature of asphalt pavement can reach 60°C in the high-temperature environment in summer. The temperature accumulation effect causes the temperature of the middle and lower layers to increase by approximately 10°C, which easily induces rutting. Ambient humidity has a great influence on the change in moisture concentration in the upper layer. Considering the influence of ambient humidity in the high-temperature environment, the rut depth increases by 67%.

On the mechanical behavior of carbon fiber/epoxy laminates exposed in thermal cycling environments

Carbon fiber reinforced polymer (CFRP) composites are commonly used for reflectors of artificial satellites operating in low earth orbit (LEO). The decay of the modulus of the CFRP composite varies under different thermal cycling environments, which can lead to a reduction in the accuracy of the reflector panels, affecting the transmission of signals. This paper investigates the impact of different thermal cycling conditions on the mechanical behavior of carbon fiber/epoxy laminated composites experimentally. Three kinds of thermal cycling conditions involving continuous temperature changes are employed to explore the influence of temperature range on the residual tensile and in-plane shear moduli of the laminates. Test results indicate that the upper temperature limit and the temperature span of the thermal cycling conditions jointly affect the mechanical properties of CFRP composite laminates, but the responses of the residual tensile and in-plane shear moduli are different under the variation of each temperature parameter alone. The residual tensile and in-plane shear moduli of the laminates under thermal cycling decrease with an expansion of the temperature span having the same upper limit. If the temperature span remains constant, an increase in the upper temperature limit leads to an increase in the residual tensile modulus, but a decrease in the residual in-plane shear modulus. The main damages causing the decay of residual tensile and in-plane shear moduli of unidirectional laminates were investigated by scanning electron microscopy (SEM) technology. Observations of the microscopic fracture of the material show that the post-curing reaction factor predominantly influences the residual tensile modulus of unidirectional laminates, while the fiber/matrix interface damage factor dominates the residual in-plane shear modulus of the unidirectional laminates. Furthermore, an increase in the fiber tensile modulus decreases both residual tensile and residual in-plane shear moduli. Notably, the residual in-plane shear modulus exhibits greater sensitivity to thermal cycling compared to the residual tensile modulus. The findings reported in this paper would provide valuable insights and guidance for the design and application of carbon fiber/epoxy composites subjected to thermal cycling conditions.

Monitoring the effect of water temperature on the heart rate of olive flounder (Paralichthys olivaceus) using a bio-logger

Olive flounder (Paralichthys olivaceus) is a major aquaculture fish species in South Korea and is primarily cultivated in running water culture systems. However, these systems undergo continuous water temperature changes due to environmental variations, and abrupt changes in water temperature can lead to physiological stress. This study was conducted to monitor the health conditions of farmed olive flounder according to water temperature. A bio-logger (DST milli-HRT, Star-Oddi) was inserted near the heart of olive flounder to observe heart rate changes in response to water temperature under two scenarios. In Experiment 1, the water temperature was increased (1 °C/day) from 15 °C to 25 °C. In Experiment 2, the water temperature was constant (28 °C). Control fish were cultivated at 24 °C. All logged heart rate measurements were graded with a data verification quality index (QI) to calibrate the electrocardiogram data. All experiments were conducted in duplicate. In Experiment 1, the average heart rates at 15 °C and 25 °C were 35 ± 8.70 beats min−1 and 59 ± 20.99 beats min−1, respectively, demonstrating a significant (p < 0.05) increase of 69%. No significant changes in heart rates relative to those at 15 °C (baseline) were observed from 15 °C to 22 °C (p > 0.05); however, a significant difference was observed at 23 °C (p < 0.05). In Experiment 2, heart rates fluctuated between 66 and 69 beats min−1 at 28 °C. In the control experiment, heart rates remained relatively constant with an average of 46 ± 1.66 beats min−1. Notably, heart rates were higher in Experiment 2 than in Experiment 1, suggesting that cardiac output may increase with the increased oxygen requirement of olive flounder under certain conditions, especially during growth at high water temperatures. Moreover, the variations in the heart rate of olive flounders according to the diurnal cycle were found to increase from day to night when the fish were kept within an optimal water temperature range (control experiment). Additionally, the heart rate of olive flounders was found to increase during feeding.

Experimental Study of the Concrete Cracking Behavior of an Immersed Tunnel under Fire

This study investigates the impact of fire on the cracking behavior of immersed tunnels. A reduced-scale (1:5) model of an immersed tunnel was constructed to conduct fire tests in both traffic tubes using the HCinc curve as the applied fire. Temperature field changes were carefully monitored during the test by thermocouples and infrared thermography on the outer surface of the tunnel’s ceiling. The continuous temperature field and temperature changes in the concrete cracks were recorded by infrared thermography. By integrating the temperature field distribution in concrete and the behavior of concrete cracking, an analysis of the depth of concrete cracking in the immersed tunnel under fire was conducted. The concrete cracks exceeded 150 mm at 95 min of the fire test. The results indicate that the inner concrete exposed to fire undergoes thermal expansion, leading to tensile cracking of the outer concrete. Additionally, the fire-exposed surface of the tunnel is vulnerable to cracking due to a temperature decrease. Thus, the design of fire resistance of immersed tunnels should take into consideration the potential for concrete cracking caused by thermal strain.

Ex vivo evaluation of the sensitivity of modified average speed of sound estimation method

The speed of sound (SoS), which is the propagation speed of longitudinal waves, is expected to be effective for the early detection and monitoring of diseases. Several methods that use handheld probes have been proposed to estimate the SoS. In this study, a modified average SoS estimation method, referred to as the improved focusing method, is proposed to increase the accuracy of average SoS estimation. In the proposed method, a plane wave was transmitted, and the center-element position-dependent variations in the SoS estimation were reduced. Ex vivo experiments were conducted using chicken liver to evaluate the applicability and sensitivity of the proposed method to actual tissues. The livers were subjected to continuous temperature changes to induce changes in the SoS. The results suggest that the improved focusing method measures the average SoS accurately as well as small SoS changes of approximately 1.5 m·s−1·°C−1.

Effect of Magnetite Concrete on Splitting Tensile Strength and Gamma Ray Shielding Performance Exposed to Repeated Heating at High Temperature

Radiation shielding concrete is one of the most used materials in the construction of nuclear power plants and will be subjected to high temperatures for a long time during its service life. This study aims to investigate deterioration of radiation shielding concrete with multiple heating at different temperatures. A microwave oven was used as a heating apparatus to simulate irradiation, and 200, 300, and 400 °C were selected as experimental cycle temperatures. The apparent characteristics, mass loss, splitting tensile strength, and gamma ray shielding properties of the commonly used magnetite shielding concrete were investigated. The results showed that the splitting tensile strength and gamma shielding performance of concrete were dramatically reduced at first heating. Then, as the heating times increased, the splitting tensile strength and gamma shielding properties of the concrete continued to deteriorate, and the higher the increase in heating temperature, the more severe the deterioration of the concrete. During the service period of radiation shielded concrete, the magnitude of temperature under the service conditions will affect the deterioration degree of concrete, and the continuous change of temperature will continuously lead to the deterioration of concrete.

In process monitoring of the thermal profile during solidification in laser directed energy deposition of aluminium

• In situ infrared imaging of directed energy deposition in high spatial resolution. • Image processing to determine changes of weld pool geometry during deposition. • Experimental determination of local solidification rates during deposition. • Experimental determination of local temperature gradients during deposition. The manufacturing of parts in a layer-by-layer fashion in laser based directed energy deposition (L-DED) of wire enables a unique flexibility and freedom of part design, but some technological challenges remain unsolved. The cumulative heat input, which results from the subsequent addition of individual layers, leads to a continuous temperature change with proceeding build progress. In order to access a comprehensive investigation of this effect, the process was analysed by infrared imaging in spatial and temporal resolution. The present work describes an image based processing method, to monitor the process zone of the L -DED process. The algorithm detects the point in time, when the process zone is present in the field of view of the infrared camera, and determines the current location of the melt pool and the solidification zone. The captured isotherms determine the change of the temperature field in case of L -DED-manufacturing with different process parameters. Finally, the local solidification rates and temperature gradients were deduced from the geometry and position of the captured isotherms. The comparison of spatial distribution of these solidification conditions highlights the significant influence of the process parameters on solidification in L -DED.

1064 nm InGaAs metamorphic laser power converts with over 44% efficiency.

InGaAs metamorphic laser power converters (LPCs) have the potential to deliver electrical energy over distances of several kilometers. In this study, metalorganic chemical vapor deposition (MOCVD) was used to grow InGaAs-based LPCs with an absorption wavelength of 1064 nm. At step thicknesses of 2800 nm, overshoot thicknesses of 6000 nm, reverse component and thicknesses of 2.4% and 700 nm, respectively, a surface roughness of 6.0 nm and InGaAs (24%) lattice relaxation of 93.7% of the InGaAs metamorphic buffer were obtained. The I-V characteristics of LPCs with 10 × 10 mm2 apertures were investigated as a function of laser power and temperature. The maximum conversion efficiency of 44.1% and 550 hours of continuous stable operation at 4 W were demonstrated. Under 1064 nm laser illumination of 4 W, the temperature coefficients for the conversion efficiency and open-circuit voltage were -0.1%abs/°C and -1.6 mV/°C, respectively, and the LPC output power fluctuation was less than 0.5% during 216 hours of continuous temperature change from 20 to 100°C.

A sample holder for simultaneous neutron and dielectric spectroscopy – dielectric tests with glycerol, glycerol-water, water and phosphoric acid

We report on dielectric test measurements of a rectangular flat sample holder which serves as capacitor and which is aimed for simultaneous neutron and dielectric (n-DE) spectroscopy of acidic liquid samples. We describe technical details of the sample holder assembly and the dielectric and neutron equipment as well as the sample preparation procedure of the air sensitive acidic samples. The sample holder was characterised off-line from the neutron spectrometer by dielectric spectroscopy, but using the standard IN16B cryofurnace with a dielectric sample stick with 4-wire connection and a Novocontrol equipment, previously setup by a collaborative effort between ILL and Roskilde University. Temperature-dependent dielectric scans on standard samples (glycerol, glycerol-water, and Milli-Q water) were measured in the frequency range between 0.27 Hz and 1 MHz. Step-like temperature changes allowed to probe the temperature equilibrium conditions and continuous temperature changes were made to mimic typical IN16B backscattering neutron fixed window scans. Both type of scans were carried out in cooling and in heating. The standard samples show that our dielectric setup with flat sample holder is well suited for simultaneous n-DE-experiments. On the other hand, the dielectric scan on phosphoric acid reveals the limitations of our setup in case of high sample conductivities, but also shows that the DC-conductivity can still be accessed in a sufficiently wide low temperature range where the onset of conductivity can be simultaneously probed with the change in proton dynamics as seen by neutron spectroscopy.

Experimental investigation of the extreme seeking control on a transcritical CO2 heat pump water heater

• Model-free real-time maximization of transcritical system COP. • ESC design for optimizing the CO 2 discharge pressure. • Experimental investigation of ESC control under various conditions. • The system COP was maximumly improved by 8.81% under the ESC control. In recent years, CO 2 has been widely considered as one of the most promising substitutes for the HFCs due to the consideration of both the environmental protection and high efficiency. However, the system performance of a transcritical CO 2 cycle is greatly influenced by the discharge pressure, the determination of which has been the most important and hottest issue. Apart from the traditional correlation development through theoretical analysis and experimental data, model-free extreme seeking control method has also been proved to be effective through the simulation investigation in literatures. However, the related experimental investigation is still rare. In this article, we provide the experimental investigation of the ESC method on a transcritical CO 2 heat pump water heater. The ESC controller was designed based on the system dynamics and then implemented on the test rig. Experimental investigation was then carried out under the fixed design condition (inlet water temperature at 40°C and air temperature at 0°C) and the fixed off-design condition (inlet water temperature at 45°C and air temperature at 0°C), the system COP operated by the ESC controller was improved by 7.62% after 4167s, and by 8.81% after 4287s respectively. The experimental results under the continuous step change of the inlet water temperature (40-45-40°C) demonstrated the repeatability and the effectiveness of the ESC control under changing working conditions. The static performance of the heat pump water heater was finally explored under the inlet water temperatures of 40°C and 45°C to furtherly demonstrate that the found discharge pressures of the ESC controller were indeed the optimal discharge pressures of the transcritical CO 2 heat pump.

Continuous Heating Dissolution and Continuous Cooling Precipitation Diagrams of a Nickel-Titanium Shape Memory Alloy

Binary NiTi alloys are the most common shape memory alloys in medical applications, combining good mechanical properties and high biocompatibility. In NiTi alloys, the shape memory effect is caused by the transformation of an austenite phase to a martensite phase and the reverse process. Transformation temperatures are strongly influenced by the exact chemical composition of the NiTi phase and the presence of precipitates in the microstructure induced by thermo-mechanical treatment, especially solution annealing and ageing. Isothermal time–temperature precipitation diagrams can be found in the literature. Cooling is frequently not considered, as water quenching is typically assumed to be sufficient. To the best of our knowledge, continuous heating dissolution (CHD) and continuous cooling precipitation (CCP) diagrams do not exist. Differential scanning calorimetry (DSC) is a common method to analyse the austenite/martensite transformation in shape memory alloys, but it has not yet been used to analyse precipitation processes during continuous temperature changes. We have enabled DSC to analyse dissolution and precipitation processes in situ during heating as well as during cooling from the solution annealing temperature. Results are presented as CHD and CCP diagrams, including information from microstructure analysis and the associated changes in the austenite/martensite transformation temperatures.

Effect of the form of granular sludge and temperature on anammox immobilized fillers: From performance to microbial community analysis

The immobilized carrier was prepared with complete anaerobic ammonia oxidation granular sludge (AnGS) and crushed AnGS, respectively. We evaluated the effects of granular form and continuous temperature changes on nitrogen removal by immobilized anaerobic ammonium oxidation (anammox) filler. The results showed that the rate of nitrogen removal of crushed and encapsulated AnGS was 20% higher than that of direct encapsulated AnGS. However, the latter had higher thresholds of tolerance to Fe2+ and Cu2+. In addition, the immobilization reduced the activation energy of anammox. Above 12.5 °C, the immobilized filler was efficient at removing nitrogen removal through the dual adjustment of temperature-hydraulic retention time. From 12.5 °C to 23 °C, the temperature had a greater influence on the nitrogen removal effect than the HRT. In contrast, HRT had a dominant influence from 23 °C to 32 °C. Anammox activity was severely inhibited below 12.5 °C. High-throughput sequencing analysis showed that the community structure migrated with the changes in temperature. The anammox functional bacteria Candidatus Kuenenia (18.31–39.73%) were the dominant genus at medium and high temperatures, and it was replaced by Chryseobacterium (24.19%) at 8.5 °C. In addition, an RDA analysis showed that Candidatus Brocadia was more adaptable to low temperatures than Candidatus Kuenenia. In addition, Bellilinea was more sensitive to temperature than Candidatus Kuenenia. Thus, the temperature could be appropriately lowered to avoid overbreeding. The results of this study optimized the operation of an anammox immobilized system and promote its further application.

Research on temperature error compensation method of vehicle-mounted laser gyro SINS

In order to solve the problem that the measurement accuracy of vehicle-mounted laser gyro strapdown inertial navigation system (SINS) is affected by the temperature change, a temperature error compensation method which can adapt to the full temperature environment is proposed. Based on the phenomenon that the temperature of the inertial sensor is still rising when the temperature of the temperature control box is kept, a continuous temperature change experiment is designed. Then, Pearson correlation analysis of the output of laser gyro and quartz flexible accelerometer with temperature, temperature rate and temperature gradient has been carried out. Based on that, the temperature error models of gyro and accelerometer are constructed, and the temperature compensation method based on polynomial model is proposed. The results show that this method could compensate the temperature error of the laser gyro and the quartz flexible accelerometer effectively, and the zero-bias stability of them are both improved, especially the zero-bias stability of the accelerometer is improved by at least one order of magnitude, the accuracy of inertial measurement in full temperature environment is improved effectively.

Integrating antioxidant responses and oxidative stress of ornamental discus (Symphysodon spp.) to decreased temperatures: Evidence for species-specific thermal resistance

Discus (Symphysodon spp.) is among the most popular ornamental fish for warm-water and species that tolerates low temperature should be preferred by discus farmers due to costs in heating aquaria. Here, we compared the antioxidant responses and oxidative stress to decreased temperatures in gills of two discus species (S. haraldi and S. aequifasciatus), by employing a continuous temperature change program, i.e., cooling (28 °C to 14 °C; −1 °C/h), cold maintenance (14 °C for 12 h) and recovery (14 °C to 28 °C; +1 °C/h). Heatmap showed distinct activities or levels of oxidative stress biomarkers in response to thermal stress between two discus species. Except for reduced glutathione content, indicators regarding antioxidant enzymatic activities (e.g., superoxide dismutase, glutathione reductase and glutathione peroxidase) and lipid peroxidation level were generally higher in S. aequifasciatus than in S. haraldi. Subordinate function analysis integrating oxidative stress biomarkers suggested that the thermal resistance of S. haraldi was in the order of cooling > cold maintenance ≈ recovery, but that of S. aequifasciatus was in the order of cold maintenance > cooling > recovery. Specifically, the lowest thermal resistance was observed in S. aequifasciatus during cold recovery, potentially indicating a more severe oxidative damage in terms of lipid peroxidation in S. aequifasciatus than in S. haraldi. These results suggest that S. haraldi had a stronger thermal resistance than S. aequifasciatus, exhibiting a significant interspecific variability under acute thermal stress.

Thermal bending and vibration of FGM plates with various cutouts and complex shapes using isogeometric method

The bending and vibration of FGM plates with various cutouts and complex shapes considering thermal effects is studied using isogeometric analysis (IGA). Three thermal conditions which vary only along the direction of thickness are included in this paper. The IGA based on high-order splines can easily and exactly describe the geometry of plates with various cutouts and complex shapes. And the consistency of basis functions used in calculation and shape functions described geometry can ensure the continuous change of temperature along the thickness direction. The displacement fields are described by the first order shear deformation theory (FSDT). Several examples including isotropic plates with various cutouts and complex shapes without thermal conditions are presented to justify the correctness and convergence of IGA-FSDT approach. Furthermore, the influence of different thermal conditions, geometric and cutout parameters and temperature changes on the thermal bending and vibrational behaviors of the considered plates are presented.

Integrity tests of cement sheath for shale gas wells under strong alternating thermal loads

During large-scale hydraulic fracturing in shale gas horizontal wells, a cement sheath easily loses its integrity due to the fluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading, which will threaten wellbore integrity. In order to figure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells, this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing, cement sheath and intermediate casing under strong alternating thermal loads. And the integrity experimental results of two kinds of full-scale cement sheaths (conventional and high-strength cement sheaths) under three kinds of strong alternating thermal loads (cycle number for the occurrence of discontinuous CO2 bubble: 4 and 14; cycle number for the occurrence of continuous CO2 bubble: 5 and 15; alternating thermal load: 30–120 °C and 30–150 °C) were obtained. And the following research results were obtained. First, alternating thermal load has a significant negative impact on the integrity of cement sheath, and with the increase of alternating temperature and temperature difference, the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply. Second, the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature. Third, the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials, and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree. In conclusion, the research results can provide a reference for the design of large-scale fracturing in deep shale gas horizontal wells.

High-frequency flashing of light source for synchronous measurement of temperature and deformation at elevated temperature

Synchronous measurement of full-field temperature and deformation at elevated temperature using non-contact optical methods attracts increasing attention in evaluating the high temperature properties of materials. The current optical methods all face one major challenge, which is the strong light reflection on the surface of the specimen. Such strong light reflection could greatly impair the measurement accuracy of the temperature field measured based on the radiation light information. Here, we develop an effective and simple testing system to overcome this difficulty. The measurement system consists of an image and temperature acquisition device, and a light source with the feature of high-frequency flashing and periodic flicking. High-frequency flashing of the light source is driven by a motor and controlled by a field programmable gate array controller. Our system can realize the synchronous control of light flashing, image capturing, and temperature acquisition. Images with light on are used to calculate the deformation field based on the digital image correlation method, and those with light off (without reflection) are used for the calculation of temperature. Based on the continuous change of temperature over time, the temperature field at the moment when light is on can be obtained by interpolating the temperature fields before and after the moment through the fitted curve. Experimental validation on the thermal heating of C/C fiber composites shows a satisfactory result for temperature and deformation measurement.

Separation of Phases and Charge States in Relaxor Ferroelectric PbCo1/3Nb2/3O3

The permittivity, conductivity, electric polarization, and features of high-resolution X-ray diffraction scattering of a relaxor ferroelectric PbCo1/3Nb2/3O3 have been investigated in the temperature range 5–350 K. Continuous correlated temperature changes in dielectric properties and electric polarization have been revealed, which were not typical of relaxor ferroelectrics. These changes can be attributed to local polar domains, which were induced in the original crystal matrix. In such domains, the charges (valences) of Co and Nb ions were continuously changed.