High Temperature Field Research Articles

Operating condition optimization of liquid metal heat pipe using deep learning based genetic algorithm: Heat transfer performance

Liquid metal heat pipes play a critical role in various high-temperature applications, with their optimization being pivotal to achieving optimal thermal performance. In this study, a deep learning based genetic algorithm is suggested to optimize the operating conditions of liquid metal heat pipes. The optimization performance was investigated in both single and multi-variable optimization schemes, considering the operating conditions of heat load, inclination angle, and filling ratio. The single-variable optimization indicated reasonable performance for various conditions, reinforcing the potential applicability of the optimization method across a broad spectrum of high-temperature industries. The multi-variable optimization revealed an almost congruent performance level to single-variable optimization, suggesting that the robustness of optimization method is not compromised with additional variables. Furthermore, the generalization performance of the optimization method was investigated by conducting an experimental investigation, proving a similar performance. This study underlines the potential of optimizing the operating condition of heat pipes, with significant consequences in sectors such as high temperature field, thereby offering a pathway to more efficient, cost-effective thermal solutions.

Preparation of PLA/PBAT blends with high performance via the synergistic effect of high mold temperature and strong shear field

As a bio-based polymer with excellent mechanical properties, good biodegradability and biocompatibility, polylactic acid (PLA) displays considerable potential to replace traditional petrochemical-based polymers for application. However, poor toughness and heat resistance restrict its wide application. In this work, PLA based PLA/PBAT blends with excellent comprehensive performance were prepared through the synergistic effect of high mold temperature as well as strong shear field. SEM, DSC and WAXD were conducted to characterize the crystal and micro-morphology of the samples. The results show that highly oriented shish-kebab and hybrid shish-kebab structures are observed in VIM-H sample. The crystallinity increases dramatically, which can reach 48%. Besides, the toughness, strength and heat resistance of VIM-H all markedly improve. The Vicat softening temperature (VST) reaches up to 149.2 °C, while the tensile strength and impact strength increase to 89.07 MPa and 10.36 kJ/m2, respectively. This study proves the synergistic enhancement of the properties for PLA/PBAT blends by high mold temperature as well as strong shear field, which provides a new method to obtain high-performance PLA materials and is beneficial for the wider application of PLA products.

Nacre-Inspired Aramid Nanofibers/Basalt Fibers Composite Paper with Excellent Flame Retardance and Thermal Stability by Constructing an Organic-Inorganic Fiber Alternating Layered Structure.

The flame-retardant paper has gradually evolved into a necessary material in various industries as a result of the rising importance of fire safety, energy efficiency, and environmental preservation. Traditional cellulose paper requires the addition of a large amount of flame retardants to achieve flame retardancy, which poses a serious threat to mechanical quality and the environment. Therefore, there is an urgent need to develop inorganic fiber flame-retardant paper with good flexibility, high thermal stability, and inherent flame retardancy. Herein, inspired by the "brick-and-mortar" layered structure of nature nacre, we developed a layered composite paper with a unique alternating arrangement of organic-inorganic fibers by synergistically integrating environmentally sustainable basalt fiber (BF) and high-performance aramid nanofibers (ANFs) through a vacuum-assisted filtration process. The as-prepared ANFs/BF composite paper exhibited low thermal conductivity (0.024 W m-1 K-1), high tensile strength (54.22 MPa), and excellent flexibility. Thanks to its excellent thermal stability, the mechanical strength remains at a high level (92%) after heat treatment at 300 °C for 60 min. Furthermore, the peak heat release rate and smoke generation of ANFs/BF composite paper decreased by 44.6 and 95.3%, respectively. Therefore, the composite paper is promising for applications as a protective layer in flexible electronic devices, cables, and fire-retardant and high-temperature fields.

Advances in (Cu,C)Ba2Ca3Cu4O11+δ Superconductors with High Critical Transition Temperature and High Irreversibility Magnetic Field

Advances in (Cu,C)Ba2Ca3Cu4O11+δ Superconductors with High Critical Transition Temperature and High Irreversibility Magnetic Field

Constructing a gradient modulus interface layer on the surface of carbon fibers to enhance the mechanical properties of carbon fiber/epoxy composites at different temperatures

A gradient modulus interface layer was designed between the carbon fiber and the epoxy by grafting the rigid polymer PPENK and the flexible polymer PEI. The influence of the interfacial modulus on the mechanical performance of carbon fiber/epoxy composite at different temperatures was analyzed. At room temperature, compared with the desized CF composite, the mechanical properties (interfacial shear, interlaminar shear, flexural strength, flexural modulus, and impact strength) of CF-PPENK-PEI composites were increased by 32.2 %, 11.4 %, 34.8 %, 24.2 % and 20.3 %, respectively. This improvement was attributed to the interfacial phase PPENK-PEI, which improved the roughness and polarity of the CF surface, increased wettability with the matrix, and buffered and balanced the modulus discrepancy between the CF and the epoxy. Atomic force microscopy (AFM) was confirmed the existence of a gradient modulus interface layer in CF-PPENK-PEI/epoxy composites. Notably, at 180 °C, the interlaminar shear strength (ILSS), flexural strength and flexural modulus of the CF-PPENK composite increased by 86.7 %, 92.5 % and 113.0 %, respectively, compared with the commercial CF composite, indicating better thermomechanical stability due to PPENK rigid heteroaromatic structures, which can maintain a high modulus at elevated temperature. Additionally, the dynamic thermomechanical properties of the composites were demonstrated the outstanding thermomechanical stability of the CF-PPENK/epoxy composites interface. Overall, this work provides a theoretical basis for preparing CF composites for use in high-temperature fields.

Ultra‐Fast Pulsed Discharge Preparation of Coordinatively Unsaturated Asymmetric Copper Single‐Atom Catalysts for CO2 Reduction

AbstractSingle‐atom catalysts possess great potential for applications in electrochemical carbon dioxide reduction reactions. Recently, the fast and low‐cost preparation of highly efficient single‐atom catalysts remains a challenge. Herein, a high‐density current generated by pulsed discharge is employed for the formation of graphene aerogel anchored Cu single atom catalysts perfectly. The Cu atoms decomposed by Cu(NO3)2•xH2O are fixed on graphene under the local transient high temperature and intense electromagnetic field. The activity and selectivity of formic acid are correlated with the coordinatively unsaturated Cu─N1O1 moieties, reaching an optimal Faradaic efficiency (93.7%) at −0.9 V versus a reversible hydrogen electrode (RHE). In situ characterizations reveal that the asymmetric Cu─N/O structure in a pinched state displays better catalytic activity in CO2RR. Density functional theory results indicate that the Cu─N1O1 sites regulate the adsorption configuration of intermediates and lower the energy barrier for the hydrogenation of *OCHO species, thereby promoting CO2‐to‐HCOOH conversion.

High-temperature thermal disturbance elimination method based on multi-channel extraction and correction.

Digital image correlation (DIC) technology has been widely used in high-temperature measurement fields. However, due to the complexity of high-temperature environments, there are many interference factors that limit the development of high-temperature DIC technology, among which thermal disturbance is one of the most significant factors that severely affects the measurement accuracy of high-temperature DIC. In this paper, a multi-channel separation technique combined with a low-cost laser speckle device is proposed to eliminate thermal disturbance errors in high-temperature DIC measurements. First, a blue laser speckle generation system is independently designed to produce the most suitable speckle particles, and the best laser speckle is determined and projected onto the blue background white spot pattern. Then a green LED illuminates the sample to provide illumination for the sample's own grayscale characteristics. A color camera collects photos, and the obtained images are processed with channel separation to extract and calculate the displacement of different channels. Finally, the displacement fields of the green and blue channels are subtracted to separate the thermal disturbance error and correct the measurement values. In this paper, a laser speckle projection system is first assembled, followed by a comprehensive evaluation of the projected speckle and, finally, a DIC experimental system is constructed for verification experiments at both room temperature and high temperature, and the corrected values are compared with the true values. The results show that the corrected values are highly consistent with the true values, which verifies the reliability of the proposed method.

Effect exponentially distributed trapped charge jump transport on energy storage performance in polyetherimide nanocomposite dielectric

With the development of science and technology, polymer dielectric capacitors are widely used in energy, electronics, transportation, aerospace, and many other areas. For polymer dielectric energy storage capacitors to remain effective in practical applications, excellent charge and discharge performance is essential. However, the performance of the common polymer dielectric capacitors will deteriorate rapidly at high temperature, which makes them fail to work efficiently under worse working conditions. Dielectric trap energy levels and trap densities increase when nanoparticles are incorporated into the dielectric. The change in trap parameters will affect carrier transport. Therefore, the high temperature energy storage performance of polymer nanocomposite dielectric can be improved by changing the trap parameters to regulate the carrier transport process. However, the quantitative relationship between trap energy level and trap density and the energy storage properties of nanocomposite dielectric need further studying. In this paper, the energy storage and release model for exponentially distributed trapped charge jump transport in linear polymer nanocomposite dielectrics is constructed and simulated. The volume resistivity and electric displacement-electric field loops of pure polyetherimide are simulated at 150 ℃, and the simulation results match the experimental results, which demonstrates the validity of the model. Following that, under different temperatures and electric fields, the current density, electric displacement-electric field loops, discharge energy density and charge-discharge efficiency of polyetherimide nanocomposite dielectric are simulated by using different trap parameters. The results show that increasing the maximum trap energy level and the total trap density can effectively reduce the carrier mobility, current density and conductivity loss, and enhance the discharge energy density and the charge-discharge efficiency of the nanocomposite dielectric. On condition that temperature is 150 ℃ and applied electric field is 550 kV/mm, the polyetherimide nanocomposite dielectric with a maximum trap energy level of 1.0 eV and a total trap density of 1×10<sup>27</sup> m<sup>–3</sup>, has 4.26 Jcm<sup>–3</sup> of discharge energy density and 98.93% of energy efficiency. These parameters in the polyetherimide nanocomposite dielectric are 91.09% and 227.58% higher than those in the pure polyetherimide, respectively. The energy storage performance under high temperature and high electric field is obviously improved. It provides theoretical and model support for the research and development of capacitors with high temperature resistance and energy storage performance.

Effect exponentially distributed trapped charge jump transport on energy storage performance in polyetherimide nanocomposite dielectric

With the development of science and technology, polymer dielectric capacitors are widely used in energy, electronics, transportation, aerospace, and many other areas. For polymer dielectric energy storage capacitors to remain effective in practical applications, excellent charge and discharge performance is essential. However, the performance of the common polymer dielectric capacitors will deteriorate rapidly at high temperature, which makes them fail to work efficiently under worse working conditions. Dielectric trap energy levels and trap densities increase when nanoparticles are incorporated into the dielectric. The change in trap parameters will affect carrier transport. Therefore, the high temperature energy storage performance of polymer nanocomposite dielectric can be improved by changing the trap parameters to regulate the carrier transport process. However, the quantitative relationship between trap energy level and trap density and the energy storage properties of nanocomposite dielectric need further studying. In this paper, the energy storage and release model for exponentially distributed trapped charge jump transport in linear polymer nanocomposite dielectrics is constructed and simulated. The volume resistivity and electric displacement-electric field loops of pure polyetherimide are simulated at 150 ℃, and the simulation results match the experimental results, which demonstrates the validity of the model. Following that, under different temperatures and electric fields, the current density, electric displacement-electric field loops, discharge energy density and charge-discharge efficiency of polyetherimide nanocomposite dielectric are simulated by using different trap parameters. The results show that increasing the maximum trap energy level and the total trap density can effectively reduce the carrier mobility, current density and conductivity loss, and enhance the discharge energy density and the charge-discharge efficiency of the nanocomposite dielectric. On condition that temperature is 150 ℃ and applied electric field is 550 kV/mm, the polyetherimide nanocomposite dielectric with a maximum trap energy level of 1.0 eV and a total trap density of 1×10<sup>27</sup> m<sup>–3</sup>, has 4.26 J·cm<sup>–3</sup> of discharge energy density and 98.93% of energy efficiency. Compared with pure polyetherimide, the rate of improvement is 91.09% and 227.58%, respectively. The energy storage performance under high temperature and high electric field is obviously improved. It provides theoretical and model support for the research and development of capacitors with high temperature resistance and energy storage performance.

High-temperature mechanical properties and dynamic recrystallization of Mo-14Re alloy

The Mo-14Re alloy is currently utilized as a candidate structural material in space nuclear reactors and exhibits significant potential in other high-temperature fields. However, due to the high cost of rhenium, limited research has been conducted on the high-temperature properties of Mo-14Re. This study aims to investigate the high-temperature tensile properties of the stress-relieved Mo-14Re within the temperature range of 1200 K to 1773 K, specifically focusing on the microstructure of dynamically recrystallized grains and their influence on high-temperature deformation. The results demonstrate that the ultimate tensile strength of Mo-14Re reaches 399 MPa, 358 MPa, 311 MPa, and 33 MPa at 1200 K, 1350 K, 1500 K, and 1773 K, respectively. Above 1350 K, the softening caused by dynamic recovery and dynamic recrystallization becomes more pronounced, surpassing the influence of work hardening on high-temperature deformation. Continuous dynamic recrystallization is identified as the primary mechanism driving the dynamic recrystallization. Moreover, a new texture emerges when Mo-14Re undergoes dynamic recrystallization above 1500 K. Notably, no precipitated phases or element segregation are observed in Mo-14Re following high-temperature deformation.

Growth mechanism under the supply-limited regime in mist chemical vapor deposition: presumption of mist droplet state in high-temperature field

In mist CVD, investigation of the dependence of the growth rate on the solution concentration and precursor supply amount in the growth of ZnO films using a methanol-based solution of Zn(acac)2 revealed that the reaction is a rate-determination process of the supply-limited regime. Based on this result, the diffusion coefficient of gasified Zn(acac)2 at standard ambient temperature and pressure (SATP) was calculated to be approximately 10−6m2/s, where the diffusion rate was derived from the relation between the precursor supply amount and the film formation amount, assuming that all precursors were gasified in the reactor. The derived values were approximately one order of magnitude lower than the typical diffusion coefficient of 10−5m2/s in the gas phase at SATP. Several factors considered were unable to explain the much lower diffusion coefficient. Therefore, this result contradicts the assumption that all precursors are gasified in the reactor, and it is presumed that droplets might remain in the liquid–gas phase.

Dielectric performance improvement of polypropylene film modified by γ-ray irradiation for HVDC capacitors

Polypropylene (PP) films exhibit low dielectric strength and high losses under elevated temperatures and strong electric field environments. This paper proposes a method to improve the dielectric properties based on γ-ray irradiation crosslinking, investigates the effect of the type of sensitizer on the crosslinking reaction, and explores the effect of crosslinking structure on the dielectric properties of PP films such as breakdown strength. The results showed that the type of group in the sensitizer influenced its activity in the crosslinking reaction, and the modified films added with pentaerythritol triacrylate (PETA) exhibited the highest crosslinking degree of 25.68%. In addition, it was found that the crosslinked structure improved the stability of the molecular chains at high temperatures and reduced the probability of thermal breakdown. At 115 °C, the modified films with PETA showed a 72.5% reduction in conductivity and a 33.6% increase in breakdown strength. This method demonstrates the importance of irradiation crosslinking modification for improving the reliability of PP films in high-temperature and strong electric field applications.

Rapidly screening out refractory metallic alloys with high glass-forming ability by laser surface remelting

Compared with conventional metallic glasses, refractory metallic glasses (RMGs) with a mass of refractory element(s), high glass-transition temperature (Tg) and outstanding mechanical properties (like ultrahigh strength, high hardness and good wear resistance) exhibit fascinating potential applications in high temperature field. However, the development of RMGs is painfully slow, and one of the key problems is the lack of rapid and convenient way to screen out high glass-forming refractory alloys. In this study, a method for rapid evaluation of glass forming ability (GFA) based on laser surface remelting was provided. The high-efficiency screening-out method was validated in a classical glass-forming model system of Ni–Nb binary refractory alloys. The effects of different laser parameters on the glass formation and phase evolution were investigated by experimental analysis and finite element simulation. By correlating thermal history of the laser treatment with glass formation, the alloys with high GFA in Ni–Nb system was screened out rapidly. The screening-out efficiency of the novel method can be improved one order of magnitude, compared with that of the conventional techniques, and the materials cost can be reduced, especially for RMGs. The revealed formation mechanism of glassy and crystalline phases in time and spatial distributions influenced by thermal history under multi-scanning laser treatment can provide a significant insight in the construction of the bulk-metallic-glass materials and the related composite ones by laser additive manufactory.

High sensitivity temperature and gas pressure sensor based on PDMS sealed tapered hollow-core fiber

We use hollow core fiber (HCF) and single mode fiber (SMF) fusion splicing to form a sensor with a “SMF-HCF-SMF” structure. To improve the sensitivity of the sensor, the HCF is tapered and stretched to a waist diameter of 10 μm. Then, in order to further improve the sensitivity of the sensor to temperature and pressure, as well as the mechanical strength of the sensor, we coated a layer of polydimethylsiloxane (PDMS) thin film on the surface of the tapered HCF. When light propagates in the sensor, an anti-resonant reflection optical waveguide (ARROW) mechanism is formed. Due to the excellent thermal sensitivity and elasticity of PDMS, the transmission spectrum of the sensor will significantly drift due to changes in environmental temperature and gas pressure, achieving temperature and pressure measurement. The experimental results show that the maximum temperature and gas pressure sensitivity of the sensor reach −3.2321 nm/℃ and −22.80 nm/MPa, respectively. In addition, the sensor also has good repeatability and stability, as well as short response time. It has certain application prospects in the field of high sensitivity temperature and gas pressure sensing measurement.

Study the Al2O3 nano-fillers performances of metallic hollow microlattice material as a heat insulation on the high-temperature

Hollow microlattice material is a kind of excellent heat insulation material due to its special microstructural characteristics and ultra-low relative density. However, the possibility of oxidation at the temperature higher than 500℃ limits its application in the high-temperature insulation fields, such as rockets and aircraft engines. In order to overcome this obstacle, this study successfully prepared nano-Al2O3 reinforced metallic hollow microlattice materials with an equivalent density of 26.5 mg/cm3. Heat insulation tests and thermogravimetric (TG) experiments were also carried out to investigate the thermal performances of the Al2O3 reinforced metallic hollow microlattice materials, while the effect of the concentration of the Al2O3 was also investigated in accordance with the comparative tests. The results indicate that the Al2O3 plays a significant role in hindering the high-temperature oxidation of hollow microlattice material, especially with Al2O3 concentration in the range of 2 g/L to 4 g/L, and the heat insulation performance can be improved by 13.9%.

Multidimensional high-temperature field measurement method for flame based on near infrared radiation spectrum of water vapor

The temperature distribution is an important parameter in the design and optimization of :various engine types, and this paper begins by analyzing the temperature sensitivities of different waveband combinations. Based on an evaluation of the effects of self-absorption phenomena on the temperature measurement accuracy, a multidimensional temperature measurement method based on the integrated ratio of the intensity of the water vapor broadband radiation spectra is proposed. To address the multidimensional temperature inversion problem, the practicality of a nonlinear reconstruction approach is evaluated, and a multiple linear iteration algorithm is proposed. In addition, validation experiments are performed in the form of methane/oxygen laminar flame temperature measurements in combination with parallel rotating beam spectroscopy, and the results show that the method exhibits temperature measurement resolution of 10 K. The method proposed and developed in this work provides a new experimental concept for high-temperature measurements and is expected to provide reliable multidimensional temperature data for combustion chambers and plumes in engine ground experiments.

Higher orders for cosmological phase transitions: a global study in a Yukawa model

We perform a state-of-the-art global study of the cosmological thermal histories of a simple Yukawa model, and find higher perturbative orders to be important for determining both the presence and strength of strong first-order phase transitions. Using high-temperature effective field theory, we calculate the free energy density of the model up to O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(y5T4), where y is the Yukawa coupling and T is the temperature. The locations of phase transitions are found using the results of lattice Monte-Carlo simulations, and the strength of first-order transitions are evaluated within perturbation theory, to 3-loop order. This is the first global study of any model at this order. Compared to a vanilla 1-loop analysis, accurate to O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(y2T4), reaching such accuracy enables on average a five-fold reduction in the relative uncertainty in the predicted critical temperature Tc, and an additional ∼ 50% strong first-order transitions with latent heat L/Tc4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ L/{T}_c^4 $$\\end{document}> 0.1 to be identified in our scan.

Optimisation of laser welding parameters to maximise the joint strength of laser weld stainless steel joints using a GA for geothermal plants

ABSTRACTLaser beam welding is vital in high-temperature fields such as the aerospace, automobile, and gas turbine manufacturing industries. In this article, parametric studies are carried out on Nd:YAG laser weldments that influence stainless steel 430 L weldment quality. A series of trial runs are organised to investigate input parameters such as peak power, frequency, speed, and time that impact output responses such as yield strength, ultimate tensile strength, shear strength, and elongation simultaneously. Trail runs on martensitic stainless steel AISI 430 L are conducted based on Taguchi experiments, and a regression equation is established. To yield optimum results, the process parameters are optimised by using the genetic algorithm optimisation technique. By conducting experimentation with optimum parameters, the output responses are compared with the optimum results 95% confidence level was obtained. The optimum levels for process variables are identified for quality weld peak power 160 kW, frequency 9 Hz, speed 3.33 mm/ms, and time 2.53 ms. Optical microscopy reveals that refined grains are formed in the weld zone with a grain size of 2.909 µm, and a scanning electron microscopy test is performed to study the morphology of AISI 430 L weldment specimen failure takes place at the interface of the weld metal.

Preparation and characterization of phase change microcapsules for improving the applicable temperature and stability of high temperature resistant drilling fluids

High temperature environment has many negative effects on the drilling fluid system. In order to avoid or delay these negative effects, phase change materials (PLMs) microcapsule technology was introduced into the high temperature drilling fluid system in this study to further improve the applicability of the high temperature resistant drilling fluid under extremely high temperature formation environment. The microcapsules circulate with drilling fluid, and PLMs melt endothermically at high temperature in deep formation and solidify exothermically at shallow formation. A PLMs microcapsule with solar salt (NaNO3: KNO3 = 3:2) as core material and nano silica as shell material was prepared by sol-gel interfacial polymerization. The structure and properties of the microcapsules were characterized, the temperature-control performance of the microcapsule and its stability and compatibility with drilling fluid were evaluated. The results showed that the microcapsules were well encapsulated, and the single microcapsule particles were spherical, but there was a certain agglomeration phenomenon. The particle size distribution of microcapsules was concentrated in 4–16 µm, with a median particle size of 7.79 µm. The highest encapsulation rate was 60.6%, and the melting enthalpy was 68.48 J/g. The microcapsules had no obvious mass loss below 400 ℃ and had excellent thermal stability. It was proved that the microcapsules had good sealability, shear stability and cycling stability, with the enthalpy/mass retention rate all above 90%. The addition of microcapsules will not affect the basic properties of drilling fluid, and can reduce the peak temperature of high temperature drilling fluid. Different from existing researches, this paper uses a method that absorbs heat to slow down the heating rate of drilling fluid in the formation. This is a new idea, which is expected to be widely studied in the field of high temperature drilling fluids.

Transdimensional ambient-noise surface wave tomography of the Reykjanes Peninsula, SW Iceland

SUMMARY Ambient noise seismic tomography has proven to be an effective tool for subsurface imaging, particularly in volcanic regions such as the Reykjanes Peninsula (RP), SW Iceland, where ambient seismic noise is ideal with isotropic illumination. The primary purpose of this study is to obtain a reliable shear wave velocity model of the RP, to get a better understanding of the subsurface structure of the RP and how it relates to other geoscientific results. This is the first tomographic model of the RP which is based on both on- and off-shore seismic stations. We use the ambient seismic noise data and apply a novel algorithm called one-step 3-D transdimensional tomography. The main geological structures in the study area (i.e. covered by seismic stations) are the four NE–SW trending volcanic systems, orientated highly oblique to the plate spreading on the RP. These are from west to east; Reykjanes, Eldvörp-Svartsengi, Fagradalsfjall and Krýsuvík, of which all except Fagradalsfjall host a known high-temperature geothermal field. Using surface waves retrieved from ambient noise recordings, we recovered a 3-D model of shear wave velocity. We observe low-velocity anomalies below these known high-temperature fields. The observed low-velocity anomalies below Reykjanes and Eldvörp-Svartsengi are significant but relatively small. The low-velocity anomaly observed below Krýsuvík is both larger and stronger, oriented near-perpendicular to the volcanic system, and coinciding well with a previously found low-resistivity anomaly. A low-velocity anomaly in the depth range of 5–8 km extends horizontally along the whole RP, but below the high-temperature fields, the onset of the velocity decrease is shallower, at around 3 km depth. This is in good agreement with the brittle–ductile transition zone on the RP. In considerably greater detail, our results confirm previous tomographic models obtained in the area. This study demonstrates the potential of the entirely data-driven, one-step 3-D transdimensional ambient noise tomography as a routine tomography tool and a complementary seismological tool for geothermal exploration, providing an enhanced understanding of the upper crustal structure of the RP.