Local Heat Flow Research Articles

Variations in Moho and Curie depths and heat flow in Eastern and Southeastern Asia

The Eastern and Southeastern Asian regions witness the strongest land–ocean and lithosphere–asthenosphere interactions. The extreme diversity of geological features warrants a unified study for a better understanding of their geodynamic uniqueness and/or ubiquity from a regional perspective. In this paper we have explored a large coverage of potential field data and have detected high resolution Moho and Curie depths in the aforementioned regions. The oldest continental and oceanic domains, i.e. the North China craton and the Pacific and Indian Ocean have been found thermally perturbed by events probably linked to small-scale convection or serpentinization in the mantle and to numerous volcanic seamounts and ridges. The thermal perturbation has also been observed in proximity of the fossil ridge of the western Philippine Sea Basin, which shows anomalously small Curie depths. The western Pacific marginal seas have the lowest Moho temperature, with Curie depths generally larger than Moho depths. The contrary is true in most parts of easternmost Eurasian continent. Magmatic processes feeding the Permian Emeishan large igneous province could have also been genetically linked to deep mantle/crustal processes beneath the Sichuan Basin. The regionally elongated magnetic features and small Curie depths along the Triassic Yangtze-Indochina plate boundary suggest that the igneous province could be caused by tectonic processes along plate margins, rather than by a deep mantle plume. At the same time, we interpret the Caroline Ridge, the boundary between the Pacific and the Caroline Sea, as a structure having a continental origin, rather than as hotspot or arc volcanism. The surface heat flow is primarily modulated by a deep isotherm through thermal conduction. This concordance is emphasized along many subduction trenches, where zones of large Curie depths often correspond with low heat flow. Local or regional surface heat flow variations cannot be faithfully used in inferring deep thermal structures, which can be better constrained overall through Curie depths detected from surface magnetic anomalies.

An efficient and low resistant circumferential overlap trisection helical baffle heat exchanger with folded baffles

An efficient and low resistant circumferential overlap trisection helical baffle shell-and-tube heat exchanger with folded baffles (cothHXf) is presented. It is a modified trisection helical baffle heat exchanger with folded helical baffles for setting rods-and-spanning sleeves. It not only inherits all the merits of circumferential overlap helical baffle scheme, but also adds many additional advantages, such as supporting the inclined baffles with the least rods, simplifying the manufacturing process of spanning tubes and effectively inhibiting the reverse leakage at triangular areas between adjacent baffles. The improved flow characteristic and heat transfer enhancement mechanism of this heat exchanger were numerically investigated in comparison with conventional segmental baffles shell-and-tube heat exchanger (segHX). The flow fields within triangular area of adjacent baffles and nearby regions were depicted. The impacts of the folded baffles on shell-side helical flow, secondary vortex flow, and leakage pattern were analyzed. The distribution configurations of fields of velocity, pressure, temperature and local heat flow rate were revealed. The results show that the heat transfer performance and comprehensive performance evaluation indexes of the cothHXf are much better than those of the segHX while the pressure drop of the cothHXf is much lower than that of the segHX. The numerical simulation results of vivid distributions of flow and thermal fields of the cothHXf can provide theoretical basis for an engineering design and popularized industrial application of the new type heat exchangers.

Imminent Earthquake Forecasting on the Basis of Japan INTERMAGNET Stations, NEIC, NOAA and Tide Code Data Analysis

This research presents one possible way for imminent prediction of earthquakes’ magnitude, depth and epicenter coordinates by solving the inverse problem using a data acquisition network system for monitoring, archiving and complex analysis of geophysical variables-precursors. Among many possible precursors the most reliable are the geoelectromagnetic field, the boreholes water level, radon earth-surface concentration, the local heat flow, ionosphere variables, low frequency atmosphere and Earth core waves. The title demonstrates that only geomagnetic data are used in this study. Within the framework of geomagnetic quake approach it is possible to perform an imminent regional seismic activity forecasting on the basis of simple analysis of geomagnetic data which use a new variable SChtM with dimension surface density of energy. Such analysis of Japan Memambetsu, Kakioka, Kanoya INTERMAGNET stations and NEIC earthquakes data, the hypothesis that the “predicted” earthquake is this with biggest value of the variable SChtM permits to formulate an inverse problem (overdetermined algebraic system) for precursor’s signals like a function of earthquake’s magnitude, depth and distance from a monitoring point. Thus, in the case of data acquisition network system existence, which includes monitoring of more than one reliable precursor variables in at least four points distributed within the area with a radius of up to 700 km, there will be enough algebraic equations for calculation of impending earthquake’s magnitude, depth and distance, solving the overdetermined algebraic system.

Evolution of solidification texture during additive manufacturing.

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.

More efficient and cost-effective ways of evaluating and high grading unconventional plays

With unconventional exploration expanding into basins with little seismic data and few wellbores, some lower cost technologies should be exploited up front to select areas of greater economic potential. Typically, 3D seismic is used for high grading, but it is expensive, ground access can be limited resulting in partial coverage, and, as with many technologies, interpretations can be ambiguous. However, there are less expensive alternatives, such as remote sensing, gravity and magnetics, geochemistry, and petrography, that can be used to initially identify areas with higher potential. After the initial screening evaluation, the high-graded areas can subsequently be appraised using more expensive techniques. Using less expensive screening alternatives up front can improve results and project economics. Two examples, one from the Bakken in the Williston Basin and another from the Eagle Ford at First Shot Field in Texas, are given showing how such less expensive screening data can be used to locate areas that have either better production and/or oil that is more easily produced from tight rocks. Our Bakken and Eagle Ford examples determined that our integrated approach could add value in different tectonic settings that involve rocks of very different geologic ages and depositional settings. Detecting and investigating igneous events in a sedimentary basin were important steps in our integrated approach. Igneous activity was more common in the upper crust and sedimentary basins than was generally assumed. In both of these examples, production “sweet spots” were related to igneous drivers that create areas of localized convective high heat flow that in turn were associated with recurrent movement of basement faults. Convective heat flow via hydrothermal fluids along faults and fracture zones was much more efficient than the transfer of heat by conductive heat flow. The screening data at the mega- and microscale supported the hypothesis that recurrent movement on faults and lineaments provided conduits for hydrothermal fluids and igneous volatiles. The hydrothermal fluids were interpreted to have had an important impact on in situ hydrocarbon generation, and petrography further suggested that precipitation of minerals from these hydrothermal fluids could affect porosity, permeability, rock fracturability, and overpressuring. The work and our examples proved how less expensive screening techniques, such as remote sensing, gravity, magnetics, geochemistry, and petrography, could be used to high grade unconventional shale oil plays, so the sweet spots could be drilled first.

Local vs global heat transfer and flow analysis of hydrocarbon complete condensation in plate heat exchanger based on infrared thermography

Plate heat exchangers (PHE), compact and energy-efficient, are used as condensers in various industrial applications to recover and recycle heat energy. The condenser optimization still represents a challenge. Due to complex thermo-hydraulic couplings inside three-dimensional PHE geometry, most of the literature studies are correlatives based on hypothesis as uniform heat flux or heat transfer coefficient along the condenser. In this article, some new information on the analysis of condensation heat transfer along the PHE is highlighted. The experimental study focuses on complete condensation of saturated pentane inside a PHE of 4.4mm hydraulic diameter placed vertically with a descending flow of the refrigerant. The global and local thermo-hydraulic characteristics, as the vapor quality, the heat flux density and the heat transfer coefficient, were identified along the PHE based on the infrared thermography, and the effect of mass flux, between 9 and 30kgm−2s−1, on these characteristics is analysed. The results show a significant variation, of the heat transfer coefficient and the heat flux density, between the inlet and the outlet of the condensation region for most of the mass fluxes. In our operating range, the heat flux rate decreases till 400% between the PHE inlet and outlet, while the condensation heat transfer coefficient decreases by 5–10 times. The PHE mean heat transfer coefficients, calculated from the local values are then 10–20% higher than the ones calculated from the literature assumption of uniform heat fluxes or the assumption of constant heat transfer coefficient. Moreover, the variation of the mean heat transfer coefficient with pentane mass flux allowed the identification of two condensation regimes, from gravity mode to a mix gravity/convection mode, with a transition limit around 15kgm−2s−1. Condensation flow analysis was conducted based on pressure drop measurements and calculations. Hence the global pressure drop measured experimentally and the local profile deduced from infrared images, are compared to the results obtained by models from the literature. The comparison shows that the homogeneous model and the Lockhart–Martinelli (1949)’s model predict with good agreement the experimental results.

Impact of selected parameters on the development of boiling and flow resistance in the minichannel

The paper presents results of flow boiling in a rectangular minichannel 1 mm deep, 40 mm wide and 360 mm long. The heating element for FC-72 flowing in the minichannel was the thin alloy foil designated as Haynes-230. There was a microstructure on the side of the foil which comes into contact with fluid in the channel. Two types of microstructured heating surfaces: one with micro-recesses distributed evenly and another with mini-recesses distributed unevenly were used. The paper compares the impact of the microstructured heating surface and minichannel positions on the development of boiling and two phase flow pressure drop. The local heat transfer coefficients and flow resistance obtained in experiment using three positions of the minichannel, e.g.: 0°, 90° and 180° were analyzed. The study of the selected thermal and flow parameters (mass flux density and inlet pressure), geometric parameters and type of cooling liquid on the boiling heat transfer was also conducted. The most important factor turned out to be channel orientation. Application of the enhanced heating surface caused the increase of the heat transfer coefficient from several to several tens per cent, in relation to the plain surface.

304 水平加熱平板上の自然対流における局所の熱伝達特性と流れ場の対応(OS3-(1),OS3 オーガナイズドセッション≪熱・流体・エネルギー変換工学の進展≫)

304 水平加熱平板上の自然対流における局所の熱伝達特性と流れ場の対応(OS3-(1),OS3 オーガナイズドセッション≪熱・流体・エネルギー変換工学の進展≫)

Heat flow anomaly on the seaward side of the Japan Trench associated with deformation of the incoming Pacific plate

Extensive heat flow measurements were conducted on the seaward side of the Japan Trench for investigation of the extent and the origin of high heat flow previously found on the incoming Pacific plate. The obtained data combined with the existing data showed that high and variable heat flow values are pervasively distributed seawards of the northern half of the trench and within about 150 km of the trench axis. In this anomalous zone, the average heat flow is 60 to 70mW/m2, appreciably higher than the value typical for the seafloor age of about 135 m.y. The occurrence of the anomalous heat flow along the trench indicates that it results from processes closely related to deformation of the incoming plate. Heating by intra-plate “petit-spot” volcanism and/or fluid flow along normal faults developed on the trench slope may yield local heat flow peaks but cannot raise regional average heat flow. The most probable cause of the observed widespread anomalous heat flow is efficient vertical heat transport by hydrothermal circulation in a permeable layer in the oceanic crust, which is gradually developed by fracturing due to plate bending. Similar heat flow and temperature structure anomalies on the seaward side of the trench may exist in other subduction zones.

Assessment of the Influence of Welding Parameters on Distortion

The welding involves the transfer of high localized heat flow, which results in residual stresses in the welded body. The impossibility of relieving these stresses generates welding distortions that become a problem in dimensional setting of welded structures. This study aims to evaluate the influence of some parameters in the welding process in a T-type joint. Due to the complexity of the welded joint and the deposition rate, a three-dimensional finite element model was developed for the solution of the temperature field and distortions. The transient thermal analysis used the Goldak equation for definition of the heat flux transferred to the part. The nonlinear characteristics of the phenomenon as well as the dependence of physical and mechanical properties with the temperature were considered in this work. The parameters studied were the welding speed, welding sequence and cooling time between weld beads. The results suggest that the higher welding speed, the welding sequence forward and back and with cooling interval between beads present themselves as the best parameters for welding with lower distortions.

Five Orders of Magnitude Reduction in Energy Coupling across Corrugated Graphene/Substrate Interfaces

A normal full-contact graphene/substrate interface has been reported to have a thermal conductance in the order of 10(8) Wm(-2)K(-1). The reported work used a sandwiched structure to probe the interface energy coupling, and the phonon behavior in graphene was significantly altered in an undesirable way. Here, we report an intriguing study of energy coupling across unconstrained graphene/substrate interfaces. Using novel Raman-based dual thermal probing, we directly measured the temperature drop across the few nm gap interface that is subjected to a local heat flow induced by a second laser beam heating. The thermal conductance (Gt) for graphene/Si and graphene/SiO2 interfaces is determined as 183 ± 10 and 266 ± 10 Wm(-2)K(-1). At the graphene/Si interface, Gt is 5 orders of magnitude smaller than that of full interface contact. It reveals the remarkable effect of graphene corrugation on interface energy coupling. The measurement result is elucidated by atomistic modeling of local corrugation and energy exchange. By decoupling of graphene's thermal and mechanical behavior, we obtained the stress-induced Raman shift of graphene at around 0.1 cm(-1) or less, suggesting extremely loose interface mechanical coupling. The interface gap variation is evaluated quantitatively on the basis of corrugation-induced Raman enhancement. The interface gap could change as much as 1.8 nm when the local thermal equilibrium is destroyed.

Gas hydrate identified in sand-rich inferred sedimentary section using downhole logging and seismic data in Shenhu area, South China Sea

Downhole wireline log (DWL) data was acquired from eight drill sites during China's first gas hydrate drilling expedition (GMGS-1) in 2007. Initial analyses of the acquired well log data suggested that there were no significant gas hydrate occurrences at Site SH4. However, the re-examination of the DWL data from Site SH4 indicated that there are two intervals of high resistivity, which could be indicative of gas hydrate. One interval of high resistivity at depth of 171–175 m below seafloor (mbsf) is associated with a high compressional- wave (P-wave) velocities and low gamma ray log values, which suggests the presence of gas hydrate in a potentially sand-rich (low clay content) sedimentary section. The second high resistivity interval at depth of 175–180 mbsf is associated with low P-wave velocities and low gamma values, which suggests the presence of free gas in a potentially sand-rich (low clay content) sedimentary section. Because the occurrence of free gas is much shallower than the expected from the regional depth of the bottom simulating reflector (BSR), the free gas could be from the dissociation of gas hydrate during drilling or there may be a local anomaly in the depth to the base of the gas hydrate stability zone. In order to determine whether the low P-wave velocity with high resistivity is caused by in-situ free gas or dissociated free gas from the gas hydrate, the surface seismic data were also used in this analysis. The log analysis incorporating the surface seismic data through the construction of synthetic seismograms using various models indicated the presence of free gas directly in contact with an overlying gas hydrate-bearing section. The occurrence of the anomalous base of gas hydrate stability at Site SH4 could be caused by a local heat flow conditions. This paper documents the first observation of gas hydrate in what is believed to be a sand-rich sediment in Shenhu area of the South China Sea.

Heat flow survey in the vicinity of the branches of the megasplay fault in the Nankai accretionary prism

Heat flow measurements were conducted at four sites in the Nankai accretionary prism southeast of the Kii Peninsula, around the area where the megasplay fault reaches the surface, in conjunction with long-term monitoring of bottom water temperature at nearby stations. Analysis of the obtained data showed that variations in bottom water temperature seriously affect surface heat flow measurements in the areas with water depths of less than about 2,800 m. This effect can reach up to 20% to 30% and may have significantly contributed to a large scatter in the heat flow values previously measured in the study area. The temperature records were also used to determine heat flows from sediment temperature profiles disturbed by bottom water temperature variations. Results of measurements at sites deeper than 2,800 m indicate that the regional heat flow, corrected for surface disturbances including the influence of bathymetric relief, is about 65 mW/m2, which is consistent with the value calculated using subduction thermal models. Local high heat flow values were obtained in the vicinity of the tips of the branches of the splay fault, suggesting advective heat transport by upward pore fluid flow along the faults.

Geothermal Characteristics and Hydrocarbon Accumulation of the Northern Marginal Basins, South China Sea

AbstractA total of 65 new heat flow data were obtained based on newly determined thermal conductivity and collected temperature logging data. Using these data together with those from previous studies, we constructed a geothermal gradient map as well as a heat flow map for the northern marginal basins of the South China Sea. Furthermore, geothermal characteristics of these basins and their relationship with oil and gas field distribution were analyzed. The results show that the four sub‐basins located in the northern South China Sea, namely the Pearl River Mouth Basin, Qiongdongnan Basin, Beibuwan Basin and Yinggehai Basin, are typical “hot basins” with average heat flow of 68.7±11 mW/m2, 71.1±13 mW/m2, 65.7±8.9 mW/m2, and 74.7±10 mW/m2, respectively. The overall heat flow distribution pattern in the study area, which gradually increases from the shelf to the slope corresponding with crust thinning trend, are generally controlled by regional tectonic setting. Meanwhile some high local heat flow anomalies are likely to be attributed to the fault and magmatic activities. The geothermal field may control and restrict oil and gas accumulation in the study area. In light of exploration results of these basins, we find that the gas fields are mostly located in the high heat flow basins (depressions) while the oil fields more likely lie in relatively lower heat flow basins (depressions).

Numerical Study of Established Thermo-Mechanical State of Rods of Limited Length, with the Presence of Local Heat Flows, Temperatures, Heat Insulation and Heat Transfer

Numerical Study of Established Thermo-Mechanical State of Rods of Limited Length, with the Presence of Local Heat Flows, Temperatures, Heat Insulation and Heat Transfer

Heat Transfer Investigation of Air Flow in Microtubes—Part I: Effects of Heat Loss, Viscous Heating, and Axial Conduction

Experiments were conducted to investigate local heat transfer coefficients and flow characteristics of air flow in a 962 μm inner diameter stainless steel microtube (minichannel). The effects of heat loss, axial heat conduction and viscous heating were systematically analyzed. Heat losses during the experiments with gas flow in small diameter tubes vary considerably along the flow length, causing the uncertainties to be very large in the downstream region. Axial heat conduction was found to have a significant effect on heat transfer at low Re. Viscous heating was negligible at low Re, but the effect was found to be significant at higher Re. After accounting for varying heat losses, viscous heating and axial conduction, Nu was found to agree very well with the predictions from conventional heat transfer correlations both in laminar and turbulent flow regions. No early transition to turbulent flow was found in the present study.

Local Heat Transfer and flow Patterns During Condensation in a Single Silicon Microchannel

Condensation of steam in a single silicon microchannel was investigated using a simultaneous condensate flow visualization and heat transfer measurement along the flow direction. A silicon microchannel of a rectangular cross section covered with a transparent Pyrex glass was used. Different condensate flow patterns were identified, such as mist flow, churn flow, upstream elongated bubble flow followed by a bubble sequence, and slug flow. Both surface temperature measurements and video images obtained for different flows showed that the condensate flows were periodic or stable during time. The local surface temperature, local heat flux, and local heat transfer coefficient related to different condensate flow patterns were of particular interest. The local heat transfer coefficient was deduced from the local heat flux and the local surface temperature was measured through micro-instrumentation in a microchannel. The local thermal performance of condensation flow in a microchannel was better for mist flow and upstream elongated bubble flow relative to slug and bubbly flows.

Heat flow in the Western Po Basin and the surrounding orogenic belts

On the basis of lithostratigraphic data from petroleum wells, geophysical logs and laboratory measurements, we revised surface heat-flow values from previous studies and obtained new data for the western sector of the Po Basin (Italy). The available bottom-hole temperatures were corrected for mud circulation. The in situ thermal conductivity was estimated by taking into account the combined effects of mineral composition, anisotropy, temperature and porosity. The radiogenic heat of the basin rocks was evaluated from natural γ-ray logs and with laboratory γ-ray spectrometry. After correction for sedimentation and palaeoclimate influences, the inferred surface heat flow of the basin is 73 ± 4 mW m−2 in the undeformed Po foredeep and decreases to 64 ± 6 mW m−2 in the Alps and Apennines buried units, affected by active thrust. Numerical and analytical calculations indicate that such a decrease is likely caused by thrusting. Local heat flow minima (<60 mW m−2) may be related to groundwater movement. These data together with those available for the surrounding orogenic belts allow redrawing the heat-flow pattern of northwestern Italy.

Decaying swirl flow in round tubes with short-length twisted tapes

This paper presents experimental and numerical results of the local heat transfer coefficient and flow characteristics of decaying turbulent swirl flow generated by short-length twisted tapes (STs). The STs with three different twist ratios (y/W=3, 4 and 5) were applied at the entrance of the test section. The experiments were conducted under uniform heat flux conditions for water flow rates in the range of 5200≤Re≤15,300. The results of the tube without swirl generator as well as the ones with full-length twisted tape (TTs) are also reported as the reference cases. The experimental results reveal that the tube with STs consistently yields higher local Nusselt number than that the one without swirl generator. The local Nusselt numbers decrease with increasing axial distance (x/D) due to the decaying effect. Although, STs consistently provide poorer heat transfer than TTs over the range studied, the STs with y/W=4 and 5 yield superior thermal performance factors to the TTs at the same twist ratios, for Reynolds numbers beyond 10,000 due to the prominent effect of heat transfer improvement over that of the increase of friction factor. For better understanding, the visualization of flow structure (pathline and vector plot) in the tubes with STs is also presented.

Probing for inclusions in heat conductive bodies

This work deals with an inverse boundary value problem arising from the equation of heat conduction. Mathematical theory and algorithm is described in dimensions 1--3 for probing the discontinuous part of the conductivity from local temperature and heat flow measurements at the boundary. The approach is based on the use of complex spherical waves, and no knowledge is needed about the initial temperature distribution. In dimension two we show how conformal transformations can be used for probing deeper than is possible with discs. Results from numerical experiments in the one-dimensional case are reported, suggesting that the method is capable of recovering locations of discontinuities approximately from noisy data.