Near-field Temperature Research Articles

Experimental study of leakage characteristics and risk prediction of N2-containing dense-phase CO2 pipelines in real transportation conditions

In the background of pipelines being widely used as a critical transportation chain for the carbon capture, utilization and storage (CCUS) process, studying the leak diffusion characteristics and risks of high-pressure impure CO2 pipelines in real transportation conditions is critical for process safety. Due to the limitations of the capture process and economic cost, the CO2 used for sequestration contains impurities in the range of 3% molar ratio, mainly N2. In this paper, the first leakage experiments involving dense-phase CO2 with a 3% molar ratio of N2 impurity were conducted on a large CO2 pipeline (258 m long and 233 mm inner diameter) using initial leakage orifices of 50 mm and 100 mm. Data concerning the thermodynamic properties of the impurity-containing leakage source were gathered for the analysis of phase transitions and flow alterations within the pipeline, as well as near-field temperature and the progression of the far-field concentration. The pressure-temperature curve in the pipe shifted along the dew line and then slowly shifted to the saturation line of pure CO2 with the influence of N2 impurities during the multiphase leakage phase. In the near-field region, cryogenic diffusion was governed by the boundary of the jet, with the control distance decreasing as the leakage orifice increased. In addition, an accurate prediction model of CO2 concentration on the leak axis was established based on the virtual source theory and the concentration decay law, and the predicted locations of CO2 concentrations at the 5% were 169 m and 210 m. As the leak orifice increases, the risk of low temperatures and high concentrations escalates, albeit with a sharp decrease in duration. These data provide accurate leakage characteristics and risk assessment for safely operating high-pressure CO2 processes under real conditions with impurities.

Photothermal catalytic conversion of water and inert nitriles to amide activated by in-situ formed transition-metal-complex nanodots

Photothermal catalytic N-acetylation of aniline has been a promising strategy to synthesize amides, which combined the advantages of thermal catalysis and photocatalysis. Herein, we demonstrate a high-performance strategy to synthesize amides catalyzed by the in-situ formed first-row transition-metal (Fe, Co, Ni, Mn et al.) complexes nanodots (TMC NDs) under solar light excitation without using noble metals or strong acids. The dual-functional nitriles substrates acted as the ligands to coordinate with transition-metal salts affording photosensitive TMC NDs with high solar-to-thermal energy conversion efficiency. Intramolecular charge transitions reduced the energy barrier of nitriles activation by weakening CN bond and triggered near-field temperature rise via the electron–phonon scattering non-radiative pathway. The reaction system exhibited good tolerance to different functional groups, affording a series of amide derivatives. Such a dynamic coordination reaction mode and the in-situ formed TMC NDs opens new avenues toward solar-heat conversion via photon–phonon coupling in the field of chemical synthesis.

Multi-channel charge transfer in self-supporting B-g-C3Nx/Bi2S3/CdS dual S-scheme heterojunction toward enhanced photothermal-photocatalytic performance

Improving the charge separation efficiency of catalysts is a significant challenge in photocatalysis. To solve this problem, we design a three-dimensional self-supported B-g-C3Nx/Bi2S3/CdS dual S-scheme heterojunction photocatalytic system mimicking natural photosynthesis to achieve multi-channel rapid charge transfer. The dual S-scheme heterojunction induces double interface electric fields on the surface of ultra-thin B-g-C3Nx nanosheets, which can drive charge carriers to migrate directionally along multiple channels and suppress carrier recombination through spatial separation of electrons and holes. Furthermore, the three-dimensional interconnected open framework of B-g-C3Nx/Bi2S3/CdS enhances light absorption, touching off intense photothermal effects and near-field temperature rise, thereby improving the chemical reaction kinetics. Benefiting from the efficient charge separation and near-field temperature rise, the B-g-C3Nx/Bi2S3/CdS exhibits a photocatalytic oxytetracycline degradation rate of 98.7% and H2 evolution rate of 4.78 mmol g−1 h−1. This work provides new insights into the construction of efficient S-scheme photocatalysts with multiple-channel charge transfer characteristics.

Modeling and calibration of micro/nano FBG temperature probe for scanning probe microscopy.

To accurately measure the local temperatures of the micro-nano area, we propose an optical method using a tapered fiber Bragg grating (FBG) probe with a nano tip for scanning probe microscopy (SPM). When the tapered FBG probe senses local temperature through near-field heat transfer, the intensity of the reflected spectrum decreases, along with a broadening bandwidth and a shift in the central peak position. Modeling the heat transfer between the probe and the sample shows that the tapered FBG probe is in a non-uniform temperature field when approaching the sample surface. Simulation of the probe's reflection spectrum reveals that the central peak position shifts nonlinearly with increasing local temperature. In addition, the near-field temperature calibration experiments show that the temperature sensitivity of the FBG probe increases nonlinearly from 6.2 pm/°C to 9.4 pm/°C as the sample surface temperature increases from 25.3°C to 160.4°C. The agreement of the experimental results with the theory and the reproducibility demonstrate that this method offers a promising approach for exploring micro-nano temperature.

Temperature Field Measurement of Photovoltaic Module Based on Fiber Bragg Grating Sensor Array.

Studying the temperature field of photovoltaic modules is important for improving their power generation efficiency. To solve the problem of traditional sensors being unsuitable for measuring the spatial temperature field, we designed a real-time detection scheme of the photovoltaic module temperature field based on a fiber Bragg grating (FBG) sensor array. In this scheme, wavelength division multiplexing and space division multiplexing technologies were applied. The multi-channel FBG sensor strings were arranged on the surface and in the near field of the photovoltaic module. Different FBG strings were selected through optical switches, and the wavelength of the FBG string was addressed and demodulated using the tunable laser method and a peak-seeking algorithm. A measurement experiment of the photovoltaic module temperature field was carried out in an outdoor environment. The experimental results showed that the fluctuation law of the photovoltaic module surface and near-field temperature is basically consistent with that of solar radiation power. The temperature of the photovoltaic module decayed from the surface to space. Within 6 mm of the photovoltaic module surface, the temperature sharply dropped, and then the downward trend became flat. The lower the solar radiation power and the higher the wind speed, the faster the temperature decay. This method provides technical support for measuring the temperature field of a photovoltaic module and other heat source equipment.

MoS2@In2S3/Bi2S3 Core-shell dual Z-scheme tandem heterojunctions with Broad-spectrum response and enhanced Photothermal-photocatalytic performance

MoS 2 @In 2 S 3 /Bi 2 S 3 core - shell dual Z-scheme tandem heterojunction photocatalyst is fabricated by two-step hydrothermal methods and exhibits excellent photocatalytic performance. It can be attributed to unique core-shell dual Z-scheme tandem heterojunction structure favors efficient interface contact and facilitates the transfer and spatial separation of photogenerated electron-hole pairs and prolongs the carrier lifetime. • MoS 2 @In 2 S 3 /Bi 2 S 3 core-shell dual Z-Scheme tandem heterojunction is fabricated. • It shows broad-spectrum response and excellent photothermal effect. • It exhibits excellent photocatalytic hydrogen evolution and degradation performance. • Dual Z-scheme tandem heterostructures promotes effective spatial charge separation. Oxygen-doped MoS 2 @In 2 S 3 /Bi 2 S 3 core-shell dual Z-scheme tandem heterojunctions are fabricated via two-step hydrothermal methods. In 2 S 3 and Bi 2 S 3 nanosheets grow on the outer surface of oxygen-doped MoS 2 spheres, and the tight interface between the spheres could ensure stable electron transfer. MoS 2 with oxygen defects could inhibit the recombination of photo-induced electron-hole pairs. The unique core-shell structure increases the interface area and provides adequate surface reactive sites for the reactants. The resultant MoS 2 @In 2 S 3 /Bi 2 S 3 shows broad-spectrum response and excellent photothermal effect, which is beneficial to trigger the near-field temperature rise and promote the photocatalytic process. The MoS 2 @In 2 S 3 /Bi 2 S 3 exhibits excellent photocatalytic H 2 evolution rate of 973.42 μmol h −1 g −1 , and the degradation efficiency of tetracycline within 90 min is 99.6%, which is ∼ 10 times higher than that of pristine MoS 2 . It can be ascribed to the unique core-shell dual Z-scheme tandem heterojunction structure facilitates the transfer and spatial separation of photogenerated electron-hole pairs, and greatly prolongs the carrier lifetime. In addition, the long-term stability indicates the potential applications due to the core-shell dual Z-scheme tandem structure inhibiting the photocorrosion of sulfides.

Analysis of the influence of the multi-fracture water flow and heat transfer direction on the near-field temperature of high-level radioactive waste repository

Analysis of the influence of the multi-fracture water flow and heat transfer direction on the near-field temperature of high-level radioactive waste repository

Numerical analysis of the influence of the number of waste canister in borehole on the temperature, stress, and displacement in the near field of the high-level waste repository

Safe disposal of high-level waste is a challenging problem facing the scientific, technological, and engineering communities. The actual high-level waste disposal is closely related to the number of waste canisters in a single borehole. The influence of the number of waste canisters in a single borehole on the near-field temperature, stress, and displacement of the repository is directly related to the safety and cost of waste disposal. In this paper, based on the conceptual model of the high-level waste repository, the influence of the number of waste canisters in a single vertical borehole on the near-field temperature, stress, and displacement of the high-level waste repository was calculated and analyzed by using the 3DEC program. The results show that as the number of waste canisters in a single borehole increases, its heat release capacity is enhanced, and the temperature in the same area near the repository increases gradually; the temperature gradient increases gradually. The more waste canisters in a single borehole, the higher the temperature of the observation point near the same location of the repository (about 30°C), the temperature difference is getting larger and larger, and the average increase of temperature difference at observation point is about 8.1°C. The change of normal stress at the observation point is obvious when the waste canister releases heat for about 0–1 year; after that, the compressive stress decreased slightly, and then the stress and time curve was basically horizontal; the stress difference is getting larger and larger; the average increase of stress difference is about 0.0545MPa.The general trend of observation point displacement is that when the waste canister releases heat for about 0–1 year, displacement increases greatly, and then displacement increases less and presents a linear distribution trend; the displacement difference is getting larger and larger; the average increase of displacement difference is about 0.00034m. The thermal superposition effect of waste canisters added in a single borehole in engineering design cannot be ignored, and it showed that attention should be paid to the number of waste canisters in the disposal pit.

A double-layered model for near-field temperature in a nuclear waste repository

The temperature distribution is an important issue for the design and safety assessment of the repository for disposing high-level radioactive nuclear waste (HLRW). In order to analyze the heat conduction property near the canister containing HLRW, in this paper two kinds of double-layered model are established respectively for the unit cell scale and repository scale, and the corresponding analytical solutions are obtained in terms of the heat conduction equations for the buffer layer and surrounding rock by the separate variable method. Then, the proposed analytical solutions are verified by checking against the existing ones for a special case in the literature. Finally, a parametric study is performed to investigate the temperature behavior in the buffer layer and surrounding rock with different parameters.

Hollow MoSe2@Bi2S3/CdS Core-Shell Nanostructure as Dual Z-Scheme Heterojunctions with Enhanced Full Spectrum Photocatalytic-Photothermal Performance

Inadequate separation of carriers is still major obstacles to the practical application of photocatalysis. The reasonable design of semiconductor photocatalysts is expected to break through this bottleneck. Herein, MoSe2@Bi2S3/CdS is designed by solvothermal-hydrothermal strategy. Thanks to the dual Z-Scheme heterojunction conforms to the characteristics of multi-channel charge transfer which favor the spatial separation of carriers. MoSe2@Bi2S3/CdS hollow structure increases the utilization rate of light source, the core-shell structure increases the interface area and the active sites. Moreover, full spectrum absorption endues MoSe2@Bi2S3/CdS with unpredictable photothermal effect, which can touch off near-field temperature rise to facilitate photocatalytic process. Profiting from the synergistic facilitation effect, MoSe2@Bi2S3/CdS exhibits excellent photocatalytic activity in the hydrogen evolution and pollutants removal of Cr (VI) and 2,4,6-trichlorophenol (TCP), which are up to 11.84 mmol/g/h, 98.7% and 99.2%, respectively. This dual functional MoSe2@Bi2S3/CdS photocatalyst may paves new opportunities for solving the energy crisis and environmental pollution.

Semianalytical Solution to Near-Field Temperature in Nuclear Waste Repository

The temperature field in a nuclear waste repository is an important issue with regard to the design and safety assessment of the repository. In this paper, a double-layer model for simulating the heat conduction near a single waste canister is established, and then, by applying the Laplace transform to the governing equations of the heat conduction in the buffer layer and the surrounding rock, the solutions of the temperature field are obtained in the Laplace domain. The temperature distribution near the nuclear waste canister is presented by numerical inversion of the solutions using Crump’s method in the time-space domain. Finally, the effects of parameters on the temperature on the canister surface are analyzed. The results show that the double-layer model of the heat conduction increases the maximum temperature on the canister surface by about 11.87°C compared to the single-layer model. The double-layer model is verified to be reliable by comparing with a line heat source model that has been verified by numerical calculations. The temperature on the canister surface is significantly affected by the burnup value and cooling time of the nuclear waste, the thickness of the buffer layer, the thermal conductivities of the buffer material and the surrounding rock, and the external boundary condition.

Direct molecular-level near-field plasmon and temperature assessment in a single plasmonic hotspot

Tip-enhanced Raman spectroscopy (TERS) is currently widely recognized as an essential but still emergent technique for exploring the nanoscale. However, our lack of comprehension of crucial parameters still limits its potential as a user-friendly analytical tool. The tip’s surface plasmon resonance, heating due to near-field temperature rise, and spatial resolution are undoubtedly three challenging experimental parameters to unravel. However, they are also the most fundamentally relevant parameters to explore, because they ultimately influence the state of the investigated molecule and consequently the probed signal. Here we propose a straightforward and purely experimental method to access quantitative information of the plasmon resonance and near-field temperature experienced exclusively by the molecules directly contributing to the TERS signal. The detailed near-field optical response, both at the molecular level and as a function of time, is evaluated using standard TERS experimental equipment by simultaneously probing the Stokes and anti-Stokes spectral intensities. Self-assembled 16-mercaptohexadodecanoic acid monolayers covalently bond to an ultra-flat gold surface were used as a demonstrator. Observation of blinking lines in the spectra also provides crucial information on the lateral resolution and indication of atomic-scale thermally induced morphological changes of the tip during the experiment. This study provides access to unprecedented molecular-level information on physical parameters that crucially affect experiments under TERS conditions. The study thereby improves the usability of TERS in day-to-day operation. The obtained information is of central importance for any experimental plasmonic investigation and for the application of TERS in the field of nanoscale thermometry.

Disorder Engineering in Monolayer Nanosheets Enabling Photothermic Catalysis for Full Solar Spectrum (250–2500 nm) Harvesting

AbstractA persistent challenge in classical photocatalyst systems with extended light absorption is the unavoidable trade‐off between maximizing light harvesting and sustaining high photoredox capability. Alternatively, cooperative energy conversion through photothermic activation and photocatalytic redox is a promising yet unmet scientific proposition that critically demands a spectrum‐tailored catalyst system. Here, we construct a solar thermal‐promoted photocatalyst, an ultrathin “biphasic” ordered–disordered D‐HNb3O8 junction, which performs two disparate spectral selective functions of photoexcitation by ordered structure and thermal activated conversion via disordered lattice for combinatorial photothermal mediated catalysis. This in situ synthetically immobilized lattice distortion, constrained to a single‐entity monolayer structure not only circumvents interfacial incompatibility but also triggers near‐field temperature rise at the catalyst–reactant complexes’ proximity to promote photoreaction. Ultimately, a generic full solar conversion improvement for H2 fuel production, organic transformation and water purification is realized.

Disorder Engineering in Monolayer Nanosheets Enabling Photothermic Catalysis for Full Solar Spectrum (250-2500 nm) Harvesting.

A persistent challenge in classical photocatalyst systems with extended light absorption is the unavoidable trade-off between maximizing light harvesting and sustaining high photoredox capability. Alternatively, cooperative energy conversion through photothermic activation and photocatalytic redox is a promising yet unmet scientific proposition that critically demands a spectrum-tailored catalyst system. Here, we construct a solar thermal-promoted photocatalyst, an ultrathin "biphasic" ordered-disordered D-HNb3 O8 junction, which performs two disparate spectral selective functions of photoexcitation by ordered structure and thermal activated conversion via disordered lattice for combinatorial photothermal mediated catalysis. This in situ synthetically immobilized lattice distortion, constrained to a single-entity monolayer structure not only circumvents interfacial incompatibility but also triggers near-field temperature rise at the catalyst-reactant complexes' proximity to promote photoreaction. Ultimately, a generic full solar conversion improvement for H2 fuel production, organic transformation and water purification is realized.

Inverse estimation of near-field temperature and surface heat flux via single point temperature measurement

A concept was developed to inversely estimate the near-field temperature as well as the surface heat flux for the transient heat conduction problem with boundary condition of the unknown heat flux. The mathematical formula was derived for the inverse estimation of the near-field temperature and surface heat flux via a single point temperature measurement. The experiments were carried out in a vacuum chamber and the theoretically predicted temperatures were justified in specific positions. The inverse estimation principle was validated and the estimation deviation was evaluated for the present configuration.

High intensity focused ultrasound induced in vivo large volume hyperthermia under 3D MRI temperature control.

Mild hyperthermia can be used as an adjuvant therapy to enhance radiation therapy or chemotherapy of cancer. However, administering mild hyperthermia is technically challenging due to the high accuracy required of the temperature control. MR guided high-intensity focused ultrasound (MR-HIFU) is a technology that can address this challenge. In this work, accurate and spatially uniform mild hyperthermia is demonstrated for deep-seated clinically relevant heating volumes using a HIFU system under MR guidance. Mild hyperthermia heating was evaluated for temperature accuracy and spatial uniformity in 11 in vivo porcine leg experiments. Hyperthermia was induced with a commercial Philips Sonalleve MR-HIFU system embedded in a 1.5T Ingenia MR scanner. The operating software was modified to allow extended duration mild hyperthermia. Heating time varied from 10 min up to 60 min and the assigned target temperature was 42.5 °C. Electronic focal point steering, mechanical transducer movement, and dynamic transducer element switch-off were exploited to enlarge the heated volume and obtain uniform heating throughout the acoustic beam path. Multiple temperature mapping images were used to control and monitor the heating. The magnetic field drift and transducer susceptibility artifacts were compensated to enable accurate volumetric MR thermometry. The obtained mean temperature for the target area (the cross sectional area of the heated volume at focal depth primarily used to control the heating) was on average 42.0 ± 0.6 °C. Temperature uniformity in the target area was evaluated using T10 and T90, which were 43.1 ± 0.6 and 40.9 ± 0.6 °C, respectively. For the near field, the corresponding temperatures were 39.3 ± 0.8 °C (average), 40.6 ± 1.0 °C (T10), and 38.0 ± 0.9 °C (T90). The sonications resulted in a concise heating volume, typically in the shape of a truncated cone. The average depth reached from the skin was 86.9 mm. The results show that the heating algorithm was able to induce deep heating while keeping the near-field temperature uniform and at a safe level. The capability of MR-HIFU to induce accurate, spatially uniform, and robust mild hyperthermia in large deep-seated volumes was successfully demonstrated through a series of in vivo animal experiments.

A semi-analytical method and its application for calculating the thermal stress and displacement of sparsely fractured rocks with water flow and heat transfer

Using Goodier’s thermo-elastic displacement potential and Laplace transform, a semi-analytical method is developed for calculating the displacement and stress induced by heat transfer in sparsely fractured granitic rocks with saturated water flow and distributed heat sources. An integral equation of the thermo-elastic displacement potential is formulated in the Laplace-transformed domain. The fractures are discretized into rectangular elements, and the elemental integrals that involve singularities are calculated analytically. The numerical solutions of the potential are calculated using numerical Laplace inversion, and the temperature-gradient-induced displacements and stresses are calculated using central differences. The method is employed to examine the characteristics of the temperature-gradient-induced displacement and stress for a hypothetical problem that is intended to mimic the near-field environment of deep geological repositories of high-level radioactive wastes. Among other things, the results reveal the following: (1) In early time of operation of the repository, the region of rock under thermal expansion and compressive is limited; (2) As the intensity of the heat source gets smaller with time, only a small portion of the rock expands whereas the remaining portion contracts; (3) Downstream peak temperatures may be higher due to the supply of thermal energy by the water-flow-facilitated heat transfer, and patterns of influences of the water velocities on the thermal stress and displacement are similar; (4) Sufficiently close heat sources would cause superposition of the heating effects and make the near-field temperature increase significantly.

Quantification of near‐field heating during volumetric MR‐HIFU ablation

High-intensity focused ultrasound guided by magnetic resonance imaging has been extensively evaluated during the past decade as a clinical alternative for thermal ablation of tumor tissue. However, the maximal ablation volume is limited by the extensive treatment duration resulting from the small size of the focal point as compared to the average tumor size. Volumetric sonication has been shown to efficiently enlarge the ablated volume per sonication, but remains limited by the temperature increase induced in the skin and fat layers. In this study, multiplane MR thermometry is proposed for monitoring the near-field temperature rise in order to prevent related unintended thermal damage. The method was evaluated by performing sonications in the thigh muscle of 11 pigs maintained under general anesthesia. Volumetric ablations were performed by steering the focal point along trajectories consisting of multiple outward-moving concentric circles. Near-field heating was characterized with MR temperature maps and thermal dose maps. The results from the MR measurements were compared to simulations. In this study, the measured maximum temperature rise was found to correlate linearly with the surface energy density within the near field of the beam path with a slope of 4.2 K mm2/J. This simple linear model appears to be almost independent of the trajectory pattern and the sonication depth. The safety limit to avoid lethal damage of the subcutaneous tissues of the porcine thigh was identified to be an absolute temperature of 50 degrees C, corresponding to a surface energy density of 2.5 J/mm2 at 1.2 MHz. A linear relationship can be established to estimate the temperature increase based on the chosen power prior to ablation, thereby providing an a priori safety check for possible excessive near-field heating using a known surface energy density threshold. This method would also give the clinician the possibility to abort the sonication should excessive near-field temperature rise be seen before fat layer damage or skin burns are inflicted.

2D model in near-field microwave temperature tomography with a scanning diffraction grating

Equations have been derived to solve the inverse problem of reconstructing the Fourier expansion coefficients for the temperature of a medium as a function of coordinate along elementary layers. These coefficients are reconstructed from the known similar expansion coefficients for the thermal energy flux at the diffraction grating output as a function of the grating displacement along the medium surface. The grating is in the inhomogeneous wave zone.

Thermal constraints on disposal of heat-emitting waste in argillaceous rocks

Although the post-closure thermal phase of a repository containing heat-emitting radioactive wastes is likely to be of comparatively short duration when judged against performance assessment time-scales, the effects of temperature increase and associated thermal gradients within an argillaceous host-rock are likely to be wide-ranging and include: (a) geomechanical effects on the rock-mass and engineered structures (linings, emplacement boreholes, etc.), (b) perturbation of groundwater pressures and flow by ‘aquathermal mechanisms’, (c) possible near-field effects on mass transport properties and mechanisms (e.g. coupled flow phenomena), and (d) effects on the chemical evolution of the near-field environment. Maximum allowable temperature in a repository is likely to be constrained by host-rock and/or clay buffer/backfill thermal behaviour. Given the diverse range of the thermal responses, the identification of a primary constraint on near-field temperature and the specification of a maximum allowable temperature remains problematic.