Significant Heat Flow Research Articles

Heat flow of northern Norway, new data and geodynamic implications

The present contribution introduces new heat flow data from northern Norway, a region of the Baltic Shied and Scandinavian Caledonides that has been poorly covered until now. We computed heat flow values based on data gathered in ten boreholes reaching total depths ranging between ∼390 m and 960 m below ground level. Abundant core material for five of the studied boreholes allowed for precise determination of thermal conductivity profiles. The new determinations represent significant improvement with respect to the few pre-existing heat flow values that were based on shallow drillholes and lake measurements. The obtained heat flow values range between ∼40 and 70 mW/m2, after corrections, and suggest significant heat flow decrease (i.e. ∼10–20 mW/m2) from chiefly Proterozoic terrains to the Archean nucleus in NE Norway. The results suggest also sharp decrease in heat flow from the NE Atlantic to the Lofoten-Vesterålen margin but rather smooth gradients from the Barents Shelf to the continent. The former may be associated with abrupt deepening of the base of the lithosphere below the Lofoten-Vesterålen margin, as already suggested by previous seismic tomography studies and consistent with drastic strain focusing and the formation of a narrow margin. In contrast, gradual deepening of the base lithosphere towards the continent appears to be in agreement with the observed diffuse deformation that took place in the comparatively wide Western Barents Shelf.

Pool Boiling of Novec-649 on Inclined Microchannel

Significant amounts of heat flow can be removed with small temperature differences by boiling. This process is used in a variety of industries, e.g., cooling electronics, digital circuits, power sources, etc. Heat dissipation from equipment that generates significant heat flows involves the movement of thermal energy through a wall into a cooling fluid. In the present study, this mechanism was analysed during the boiling of Novec-649 fluid at atmospheric pressure. The heat transfer surfaces were samples made of copper with milled, parallel grooves with a depth of 0.3 mm and a width ranging from 0.2 to 0.5 mm in 0.1 mm increments for straight channels and channels inclined with respect to the vertical by 30° and 60°, respectively. The study was carried out from the onset of nucleate boiling, approximately q = 7 kWm−2 with a heat flux increase until the critical heat flux was reached. The maximum heat flux was 262 kWm−2 and the heat transfer coefficient was 19.4 kWm−2K−1, achieved for surfaces with straight microchannels. A maximum heat flux increased by 80% and a heat transfer coefficient twice as high compared to a smooth surface was obtained. The performance of the experiment can be deemed adequate, considering that it compares well with the correlation results of different authors.

Methodology for determining the parameters of high-temperature superconducting power transformers with current limiting function

<span lang="EN-US">This paper substantiates a new adaptive method for determining parameters of high-temperature superconducting power transformers with current limiting function. The main focus is the design of current-limiting superconducting windings in the light of new restrictions on current density, magnetic induction, critical current and critical temperature. The presented method considers the nature of alternating current (AC) losses in a superconductor under nominal operating conditions, features of the dielectric medium (liquid nitrogen), as well as the reduced values of the short-circuit voltage (0.5 to 1.5%). The main design features of high-temperature superconducting (HTS) transformers are specified, and a prototype of a three-phase HTS transformer of 63 kVA with a short-circuit current limiting function is developed. It is shown that HTS units have some advantages over conventional transformers: a 90 to 95% active losses reduction, short-circuit current limitation function, explosion and fire safety, a 60% reduction in weight and size, and increased efficiency (up to 99.8%). Experimental studies confirm that the short-circuit current limitation function is safe and efficient. It is demonstrated that during the short-circuit current limitation, significant heat flows occur on the windings, which should not exceed the critical value above which the superconductor could not return to the superconducting state by itself.</span>

Numerical studies of heat transfer parameters during injection feeding of powders into the rail steel melt in ladle-furnace

Technological features of powdered reagents injection into the melt using a submersible tuyere were investigated for the research and development of the main provisions of rail steel out–of-furnace treatment in a ladle-furnace. Authors analyzed the characteristics of influence of a directed heat flow through the tuyere conditional separation wall from metal to two-phase gas-powder flow under purging conditions. Using numerical methods, were determined the parameters of influence of the submersible tuyere surface temperature on characteristics of the transporting gas, concentration of the powder and its density, and on characteristics of the gas-powder flow, including the aerodynamic drag coefficient, pressure of the transporting gas, difference in phase velocities, equivalent diameter, and particle shape coefficient. The obtained experimental results show that at the same flow rate of the transporting gas, more significant heat flows, ensuring stable operation of the blowing device, are created by using a lighter gas (nitrogen), while the diameter of powdered particles does not affect the amount of heat transferred from the tuyere wall to the transporting gas. It was established that when using submersible tuyeres and heating the gas–powder flow to a temperature of 500 – 600 °C, the strength of the interfacial interaction changes by 2 to 10 times depending on the particle shape coefficient, concentration of the injected powder, pressure of the transporting gas, difference in phase velocities and density of the powder.

Numerical Studies of Heat Transfer Parameters during Injection Feeding of Powders into the Rail Steel Melt in Ladle-Furnace

Technological features of powdered reagents injection into the melt using a submersible tuyere were investigated for the research and development of the main provisions of rail steel out–of-furnace treatment in a ladle-furnace. Authors analyzed the characteristics of influence of a directed heat flow through the tuyere conditional separation wall from metal to two-phase gas-powder flow under purging conditions. Using numerical methods, we determined the parameters of influence of the submersible tuyere surface temperature on characteristics of the transporting gas, concentration of the powder and its density, and on characteristics of the gas-powder flow, including the aerodynamic drag coefficient, pressure of the transporting gas, difference in phase velocities, equivalent diameter, and particle shape coefficient. The obtained experimental results show that, at fixed flow rate of the transporting gas, more significant heat flows are created by using a lighter gas (nitrogen) ensuring stable operation of the blowing device, while the diameter of powdered particles does not affect the amount of heat transferred from the tuyere wall to the transporting gas. It was established that, when using submersible tuyeres and heating the gas–powder flow to a temperature of 500–600°C, the strength of the interfacial interaction changes by 2 to 10 times depending on the particle shape coefficient, concentration of the injected powder, pressure of the transporting gas, difference in phase velocities, and the powder density.

ТЕПЛООБМІН В ТЕПЛОВІЙ ТРУБІ ЗІ ЗМІННИМИ КУТАМИ НАХИЛУ ТА ВПЛИВУ ВІБРАЦІЙ

The article presents the results of experimental studies of the influence of modeling of external factors, such as vibrations and changes in the gravity vector, on the heat and mass transfer processes inside the heat pipe. Heat pipes are widely used as devices that allow the transfer of significant heat flows to solve various problems in power plants. Equipment using heat pipes can be found in the thermal power complex, metallurgy, aviation and rocket and space technology. Complex heat-mass exchange processes of boiling, evaporation, condensation, movement of the liquid phase in porous or capillary structure stake place inside the heat pipe. Existing methods of calculation and design are often of a recommendatory nature. The complexity of heat pipe work processes prompts scientists in the field of heat and mass transfer to further scientific research. In this work, a series of experimental studies is conducted on the modeling of work processes in the middle of heat pipes, namely the influence of vibrations and the angle of inclination on the intensity of heat exchange. This work is a generalization of experimental data on the study of the influence of vibrations and the angle of inclination on the characteristics of heat pipes.

Электротепловые переходные процессы в сети с высокотемпературным сверхпроводящим трансформатором с функцией токоограничения

The results of a study of thermal and electromagnetic transients in an electric power system containing a high-temperature superconducting (HTS) transformer with a current limiting function are presented. For carrying out the research work, an experimental HTS transformer sample with windings made of Y1Bа2Cu3O7 superconductor and with liquid nitrogen at an operating temperature of 77 K serving as dielectric medium was developed. It has been demonstrated, taking the experimental sample as an example, that transformers with HTS windings can be used to limit short-circuit currents in electrical systems. By using the developed mathematical model of a three-phase single-machine network containing an HTS transformer, it became possible to perform an in-depth analysis of electromagnetic transients in the current limiting mode and to study the thermal and electrodynamic effects produced by the short-circuit current in varying the short-circuit fault kind (single-phase, two-phase and three-phase short-circuit faults) and the type of connected load (active, active-inductive, and active-capacitive) on the current limiting degree. It has been determined that significant heat flows arise at the current limitation moment, which also should be limited. A positive effect of HTS transformers on the electric power system operating modes is shown. The obtained results of theoretical and experimental studies of HTS transformers prove a high efficiency of their current limiting function.

Temperature profile of nanospintronic device analyzed by spin-dependent Seebeck effect

The heat transport in a laterally configured nano-spintronic device, including a magnetic multi-layered nanowire has been investigated by detecting the second harmonic voltages. We show that the magnetic-field dependence of the second harmonic voltage in the multi-layered wire shows a clear spin-valve-like effect with the magnitude larger than the electrical spin valve effect. The second harmonic signal with its probe configuration dependence is found to be quantitatively explained by the spin-dependent Seebeck effect with a significant heat flow from the substrate. This demonstration paves the way for the precise analysis of the heat flow in nano-structured electronic devices.

Increasing the efficiency of the partial oil removal column

The operation of the primary oil refining unit is considered. An analysis of the operation of the operating column K-1 showed that there are noticeable fluctuations in the operating mode of the apparatus in the summer and cold season, as a result, a change in the temperature of the column top and a deterioration in the clarity of fraction rectification were observed. To study the methods of adjusting the parameters of the K-1 topping column, a computational experiment was carried out using the UniSim Design modeling system, in which the models of the apparatus and the installation model as a whole were formed. The Peng-Robinson method was used as a mathematical package for calculating the thermodynamic properties of the mixture components. Comparison of the calculated performance of the two options for the equipment of the column K-1. According to the first version, the operation of the K-1 column was simulated, in which the raw material enters the 19 tray, the hot stream is fed to the bottom of the column to the 24 tray, oil reflux to the 5 tray, acute irrigation and a partial condenser are used. Unstable technological regimes of the column top were observed in this variant in industrial conditions. To assess the fundamental possibility of changing the hardware design of the K-1 column, another option was chosen, in which there is no acute irrigation and oil irrigation, at the same time, upper circulating irrigation was introduced from the 5th to the 1st tray with cooling the flow and the technological scheme of forming and feeding the hot jet was preserved. Comparison of the fractional compositions of the topped oil showed that for the considered options, there are practically similar calculated estimates, while the use of upper circulating irrigation allows not only to unload the upper part of the distillation column from the heat load, but also to use a significant heat flow of the cooler of the upper circulating irrigation for preheating oil , which will also reduce the consumption of liquid fuel for furnaces.

Evolution of defect concentration in Zr<sub>50–</sub><i><sub>x</sub></i>Cu<sub>34</sub>Ag<sub>8</sub>Al<sub>8</sub>Pd<i><sub>x</sub></i> (<i>x</i> = 0, 2) amorphous alloys derived using shear modulus and calorimetric data

Amorphous alloys exhibit unique physical and mechanical properties, which are closely connected with their microstructural heterogeneity. The correlation between structural heterogeneity and mechanical properties is one of the important issues of amorphous alloys. Micro-alloying is an effective way to tune the mechanical and physical properties of amorphous alloys. In the present study, Zr<sub>50–</sub><i><sub>x</sub></i>Cu<sub>34</sub>Ag<sub>8</sub>Al<sub>8</sub>Pd<i><sub>x</sub></i> (<i>x</i> = 0 and 2) amorphous alloys with ability to form excellent glass are chosen as model alloys. The evolutions of heat flow and shear modulus in different states (as-cast, relaxed and crystalline) with temperature of Zr<sub>50–</sub><i><sub>x</sub></i>Cu<sub>34</sub>Ag<sub>8</sub>Al<sub>8</sub>Pd<i><sub>x</sub></i> (<i>x</i> = 0 and 2) glass system are studied by differential scanning calorimetry (DSC) and electromagnetic-acoustic transformation (EMAT) technique, respectively. The experiment demonstrates that a decrease of the shear modulus is accompanied by the endothermic heat flow and vice versa. The correlation between the heat flow and shear modulus is investigated according to the interstitialcy theory. The calculations of the interstitialcy defect concentration and activation energy spectra suggest that the microstructure remains stable at relatively low temperatures. When temperature increases, the interstitialcy defect structure is activated. Compared with that in the as-cast state, the interstitialcy defect concentration in the relaxed state is reduced by structural relaxation, indicating that temperature-dependent shear modulus softening is inhibited. At temperatures above glass transition temperature, a rapid growth of interstitialcy defect concentration results in the accelerated shear softening, which is accompanied by significant endothermic heat flow. It is noted that the minor addition of palladium reduces the interstitialcy defect concentration in the Zr<sub>50–</sub><i><sub>x</sub></i>Cu<sub>34</sub>Ag<sub>8</sub>Al<sub>8</sub>Pd<i><sub>x</sub></i> (<i>x</i> = 0 and 2) metallic glass systems. It is suggested that the introduction of Pd reduces the atomic mobility and increases the characteristic relaxation time. In parallel, the change of shear modulus as a function of the aging time (below the glass transition temperature) is studied by using EMAT equipment. The results indicate that the interstitialcy defect concentration decreases in the physical aging process, which is accompanied by an increase of shear modulus. The interstitialcy defect concentration and shear modulus change towards the quasi-equilibrium state with aging time increasing. A reduction of the interstitialcy defect concentration leads to a decrease of the shear modulus change upon microalloying by Pd into Zr<sub>50–</sub><i><sub>x</sub></i> Cu<sub>34</sub>Ag<sub>8</sub>Al<sub>8</sub>Pd<i><sub>x</sub></i> (<i>x</i> = 0 and 2) metallic glass system.

Computational Fluid Dynamics Analysis of Combined Cycle Power Plant Heat Exchanger with OpenFOAM® Software

The heat exchangers application in combined cycle power plants is a key aspect in the thermal and fluid mechanics sciences due to their elevated functionality in industrial processes related to the quality and the efficiency in the power generation. Heat exchangers are employed in thermal processes in order to remove a significant heat flow and to maintain temperature values under different working conditions. Taking into account the above, numerical methodologies have been developed with the aim to study and analyze the heat exchanger performance based on the thermal states of its physical values in space and time. Experimental methods may be applied to create models and describe the flow behavior in function of mass flow rate, pressure, and flow temperature in different measure points of the finite volume. However, it is necessary to apply numerical methods linked to computational tools in order to generate a high flow description into the heat exchanger under real working conditions. Therefore, this paper proposes a numerical analysis of the flow transported into a heat exchanger with computational tools to predict its performance under real Combined Cycle Power Plant conditions through a virtual environment. Random number generator KEpsilon turbulence model and Eulerian – Eulerian multiphase model is coupled in a Computational Fluid Dynamics code to solve the system of the partial differential equations which describes the flow behavior and heat transfer into the heat exchanger, and numerical results have been compared against the experimental model in order to verify the flow prediction of the simulation methodology employed in this particular case. The good agreement reached between the models defines an inexpensive way to evaluate and optimize the heat exchanger performance by means of OpenFOAM software.

Hybrid FEM and FDM Approach for Monolithic Catalytic Converters with Pore Diffusion

A transient, three-dimensional model is developed for monolith catalytic converters with washcoat pore diffusion. Due to the unique configuration of monolith converters, the flow within the channel can be considered fully developed laminar flow, and one-dimensional transport equations can be formulated for the flow and species. On the other hand, a three-dimensional equation is necessary for the monolith solid temperature to capture the effects of significant external heat loss or flow maldistribution. The proposed model employs a three-dimensional finite-element method (FEM) for the solid temperature equation and a one-dimensional finite-difference method (FDM) for the flow and species equations. A recently developed asymptotic approach (Bissett, Emiss. Control Sci. Technol. 1(1), 3–16, 2015, Bissett, Emiss. Control Sci. Technol. 5(1), 45–54, 2019) is utilized to solve the washcoat pore diffusion and surface coverages equations. The three-dimensional FEM meshes are chosen so the nodes also serve for the one-dimensional transport equations. All equations are solved fully coupled, without lagging or reliance upon external tools. The developed solver can efficiently simulate general cross-section geometries (circle, oval, rectangle, etc.) for a catalytic monolith under nonuniform inlet distribution and detailed washcoat pore diffusion. The solver is verified by comparing the simulation results to the one-dimensional simulation results for a simple geometry under uniform inlet conditions. The model can be applied to flow through general monolith catalytic reactors with single or dual washcoat layers and a wide range of kinetics.

Quantifying the late-to post-Variscan pervasive heat flow, central Netherlands, Southern Permian Basin

The Southern Permian Basin is marked by significant Latest Carboniferous-Early Permian magmatism attributed to mantle plume emplacement. This intense magmatic activity is commonly assumed to have impacted the heat flow in this area. In the central Netherlands a large number of wells show evidence of magmatic activity dated as Permo-Carboniferous. In addition, high maturity values have been measured for the Carboniferous and below. Theoretical models for tectonic heat flow and maturity evolution presented in this paper show that mantle upwelling, underplating, and intrusions have a significant effect on maturity-depth trends. Tectonic modelling of five selected wells shows that tectonic subsidence and exhumation can be correlated with a significant heat flow pulse at Latest Carboniferous-Early Permian time. This could well explain the widespread elevated maturity/depth gradient in Carboniferous rocks. Quantitative assessment of heat flow, based on a model of mantle plume emplacement, shows that mantle upwelling and underplating at the base of the crust, proposed by previous studies, provides insufficient heat flow to explain strongly elevated maturity-depth trends. In contrast, widespread Permo-Carboniferous calc-alkaline magmatism at shallow crustal levels provides a mechanism for elevated heat flow with a regional impact, consistent with observed high maturity-depth trends. The model and maturity data demonstrate that elevated maturity at shallow burial-depth levels of 500–1000 m is probably sited in the gas window during a heat pulse, occurring at Late Carboniferous times. • Late-to post-Variscan thermal perturbation related to magmatic event. • High maturity in central Netherlands by deep lithospheric processes. • Distinct, short lived thermal peak in carboniferous sediments. • Result fit with regional geodynamic models and magmatic occurrences across the Southern Permian Basin.

The Asymmetric Distribution of Heat Flow along Mid-Oceanic Ridges

Observations of heat flow along nine geotraverses across mid-oceanic ridges in the Atlantic, Pacific, and Indian oceans are analyzed statistically. It is found that there is significant heat flow distribution asymmetry: opposite sides of the axis of the ridges differ in the average heat flow. Geotraverses in the Southern Hemisphere of the Earth exhibit higher average heat flow on the western flanks of the mid-oceanic ridges, while geotraverses in the Northern Hemisphere are characterized by higher average heat flow along the eastern flanks. Various tectonic factors are taken into account when explaining this phenomenon; however, it is suggested that the Coriolis force must be considered the main factor responsible for this asymmetry, causing redistribution of magmatic material in the asthenospheric reservoir.

Thermal conductivity in nanoscale polysilicon structures with applications in sensors

Thermal conductivity of polysilicon nanowires and thin films has been experimentally studied. Thermal conductivity has been measured with a microstructure fabricated alongside the polysilicon nanowires and thin films and a robust fabrication process has been developed. Results suggest that the in-plane and out-of-plane thermal conductivity are limited by phonon grain boundary and film boundary scattering respectively. The nanowires are fabricated by patterning a thin layer of low-pressure chemical vapor deposited polysilicon using e-beam lithography, consequently circumventing the prevalent process of pick-and-place process, in which metallic contacts are deposited to insure significant heat flow to the nanowire. By avoiding the need for metallic contacts a significant source of error in the calculation of the thermal conductivity is eliminated. Thermal conductivity of nanowires with a cross section of ˜60 nm × 100 nm and thin film with a cross-section of 3μm × 108 nm were measured to be both ˜3.5 W/m.K, suggeting that the thermal conductiviy is dominated by the out-of-plane phonon scattering in both cases. This is an almost 8× reduction from the thermal conductivity of bulk polysilicon at ˜30 W/m.K. The effect of grain size and doping concentration on the thermal conductivity of ˜100 nm polysilicon films is also experimentally studied.

P Wave Anisotropic Tomography of the SE Tibetan Plateau: Evidence for the Crustal and Upper‐Mantle Deformations

AbstractThe upper crust in the SE Tibetan Plateau is rotating around the eastern Himalayan syntax clockwise, and the western margin of the Yangtze Craton has been involved in the active tectonics. However, it is still unclear whether and how the deep crust and upper mantle respond to the plateau expansion. In this study we present a high‐resolution three‐dimensional model of P wave velocity tomography and azimuthal anisotropy in the crust and uppermost mantle beneath the SE Tibetan Plateau determined using traveltime data recorded by a dense seismic network. Widespread low‐velocity zones are revealed around a high‐velocity body in the deep crust and uppermost mantle beneath the southwest Yangtze Craton, where fast‐velocity directions of the azimuthal anisotropy are mostly parallel to the contour lines of the surface topography and the Moho depth along the plateau margin. These results indicate that gravitational potential plays an important role in the crustal and uppermost‐mantle deformations in the SE Tibetan Plateau. Meanwhile, the shallow crust may drop down to the deep crust and drive the ductile deep‐crustal material to intrude into the adjacent regions. The extruded crust is trapped in a deep‐crustal corner and obstructed by the surrounding strong blocks. The trapped crustal material may rise up, causing significant uplift and high heat flow at the surface.

The influence of surface roughness on volatile transport on the Moon

The Moon and other virtually airless bodies provide distinctive environments for the transport and sequestration of water and other volatiles delivered to their surfaces by various sources. In this work, we conduct Monte Carlo simulations of water vapor transport on the Moon to investigate the role of small-scale roughness (unresolved by orbital measurements) in the migration and cold-trapping of volatiles. Observations indicate that surface roughness, combined with the insulating nature of lunar regolith and the absence of significant exospheric heat flow, can cause large variations in temperature over very small scales. Surface temperature has a strong influence on the residence time of migrating water molecules on the lunar surface, which in turn affects the rate and magnitude of volatile transport to permanently shadowed craters (cold traps) near the lunar poles, as well as exospheric structure and the susceptibility of migrating molecules to photodestruction. Here, we develop a stochastic rough surface temperature model suitable for simulations of volatile transport on a global scale, and compare the results of Monte Carlo simulations of volatile transport with and without the surface roughness model. We find that including small-scale temperature variations and shadowing leads to a slight increase in cold-trapping at the lunar poles, accompanied by a slight decrease in photodestruction. Exospheric structure is altered only slightly, primarily at the dawn terminator. We also examine the sensitivity of our results to the temperature of small-scale shadows, and the energetics of water molecule desorption from the lunar regolith – two factors that remain to be definitively constrained by other methods – and find that both these factors affect the rate at which cold trap capture and photodissociation occur, as well as exospheric density and longevity.

Recent mantle degassing recorded by carbonic spring deposits along sinistral strike-slip faults, south-central Australia

The interior of the Australian continent shows evidence for late Quaternary to Recent fault-controlled mantle 3He and CO2 degassing. A series of interconnected NW-striking sinistral faults, the Norwest fault zone (NFZ), in south-central Australia are associated with travertine mounds, the latter show a regular spacing of 50–70 km. U-series ages on 26 samples range from 354±7 to 1.19±0.02ka (2σ errors) and suggest a clustering every ∼3–4 ka since ∼26 ka. Geochemical data demonstrate a remarkable mantle-to-groundwater connection. Isotopic data indicate that the groundwater is circulating to depths >3 km and interacting with Neoproterozoic/Cambrian basement and mantle volatiles. 3He/4He isotope ratios show that the He comes in part from the mantle. This demonstrates that the NFZ cuts through the entire crust and provides pathways for mantle degassing. Scaling relationships suggest that the series of sinistral faults that make up the NFZ are interconnected at depths and have a significant strike length of 60–70 km or more. The NFZ occurs where a major compositional boundary and a significant heat flow anomaly occurs, and a major step in lithospheric thickness has been mapped. We discuss a tectonic model in which recent stress field, heat flow and lithospheric structure in central Australia reactivated a set of steeply dipping Neoproterozoic faults, which may now be growing into a crustal/lithospheric-scale structure.

Non-extensive statistical physics applied to heat flow and the earthquake frequency–magnitude distribution in Greece

This study investigates seismicity in Greece and its relation to heat flow, based on the science of complex systems. Greece is characterised by a complex tectonic setting, which is represented mainly by active subduction, lithospheric extension and volcanism. The non-extensive statistical physics formalism is a generalisation of Boltzmann–Gibbs statistical physics and has been successfully used for the analysis of a variety of complex systems, where fractality and long-range interactions are important. Consequently, in this study, the frequency–magnitude distribution analysis was performed in a non-extensive statistical physics context, and the non-extensive parameter, qM, which is related to the frequency–magnitude distribution, was used as an index of the physical state of the studied area. Examination of the spatial distribution of qM revealed its relation to the spatial distribution of seismicity during the period 1976–2009. For focal depths ≤40 km, we observe that strong earthquakes coincide with high qM values. In addition, heat flow anomalies in Greece are known to be strongly related to crustal thickness; a thin crust and significant heat flow anomalies characterise the central Aegean region. Moreover, the data studied indicate that high heat flow is consistent with the absence of strong events and consequently with low qM values (high b-values) in the central Aegean region and around the volcanic arc. However, the eastern part of the volcanic arc exhibits strong earthquakes and high qM values whereas low qM values are found along the North Aegean Trough and southwest of Crete, despite the fact that strong events are present during the period 1976–2009 in both areas.

Thermal conductivity of plasma modified polyethylene terephthalate and polyamide-6 layers

Tribological performance of the materials greatly depends on the temperature of the contacting zones and sur- faces and hence on the heat conducting behaviour of the materials. Heat conduction of polymers is, however, greatly affected even by a very narrow (few tens of nm) modified layer formed on the surface after subjecting the polymer to plasma treatment. In this article the heat flow inhibiting properties of plasma modified surface layers were investigated on polyethylene terephthalate (PET) and polyamide-6 (PA6) engineering polymers. Nitrogen Plasma Immersion Ion Implanta- tion gave rise to compositional and structural changes of the polymers in a depth of 110 nm. It was found that even this thin layer exhibited significant heat flow inhibiting effect. The modified layer considerably decreased the thermal conductivity coefficient of the treated polymer and resulted in a reduced heat transmission for PET and PA6 by 33 and 28%, respectively. This new information supports and is in accordance with the former tribological results about extra friction heat generation experienced under NPIII surface layer of PA6 and PET during dry sliding.