Mean Heat Flow Research Articles

Heat flow and thermal structure in the Koyna seismic zone, western India: Implications for recurrent reservoir triggered seismicity

Scientific core drilling to a depth of 1522 m in the Koyna seismic zone, western India, provides a rare opportunity to characterize the geothermal regime and study its implications on seismogenesis. The borehole KBH-1 penetrated the 932.5 m thick Deccan Trap and continued for 589.5 m in the granite-gneiss basement. The equilibrium temperature profile was obtained from measurements made 10 months after drilling. Thermal conductivity was measured on core samples of Deccan basalt and basement granitoids. Radiogenic heat production of the basement granitoids was estimated from U, Th and K analyses. Salient results are as follows. (i) The temperature gradients in Deccan basalt and granite-gneiss basement, 26.5 mKm−1 and 15.7 mKm−1, respectively, combined with thermal conductivity measurements for the two rock types, yield a mean heat flow of 43 mW m−2. (ii) The low heat flow in Koyna is similar to values characteristic of Archaean cratons. (iii) Mean Th concentration of 6.8 ppm, U 0.9 ppm, and K 1.8% yielded a mean radiogenic heat production of 0.9 μWm−3 for the basement granitoids. (iv) New geological and geothermal constraints lead to improved estimates of temperature in the crust. Although geothermal considerations support a ∼ 25 km deep seismic-aseismic transition, the seismic activity is limited to the uppermost 10 km. (v) The infrequent occurrence of earthquakes below ∼10 km could be attributed to the low permeability of the basement granitoids, which reduces the influence of pore fluids in triggering failures along faults at deeper levels.

Predicting Marine In Situ Heat Flow Using a Geospatial Machine Learning Conformal Prediction

AbstractHeat flow measurements over the past decades have drastically increased in number. However, even with vast increases in measurements, large geospatial gaps exist, most notably across Earth's oceans. As marine heat flow data acquisition can be tedious, time consuming, and ultimately expensive, new methods have arisen in an attempt to quantify heat flow across the seafloor using empirical proxies. The goal herein is to obtain a high quality, fully data‐driven, global estimate of marine in situ heat flow with calculated uncertainty. We present a heat flow analysis for Earth's marine environment using a geospatial machine learning algorithm (MLA) utilizing 33,746 heat flow measurements from the International Heat Flow Commission's most recent Global Heat Flow Database. The mean heat flow for the observational data set is 95.83 mWm−2 with a spatially averaged heat loss of 40.7 TW. We use a random forest regression MLA combined with a conformal prediction to predict in situ heat flow and its associated uncertainty for marine environments at a 100 km2 global resolution. Ten‐fold cross‐validation yields an R2 value of 0.4, indicating predictive skill. Geospatial prediction results in a global marine surface weighted in situ heat flow average of 69.67 ± 20.01 mWm−2 with a corresponding heat loss of 29.59 ± 5.78 TW. Additionally, parametric isolation is calculated to highlight areas where additional heat flow measurements would be beneficial to directly improve the overall prediction. The resultant in situ heat flow and parametric isolation maps serve as a tool to further heat flow studies within the community.

Heat Flow in the Asian Continent and Surrounding Areas

Heat flow is a key parameter to describe the interior heat of the Earth and provides constraints on understanding the thermal structure of lithosphere and assessment of the geothermal resource potential. Based on the latest heat flow database, here we present the heat flow pattern of the Asian continent and its surrounding areas and discuss the correlation between heat flow and tectonics. The mean heat flow of Asian continent and its surrounding areas is 71 ± 34 mW/m2, slightly higher than the global continental mean value, and the overall heat flow pattern in Asia exhibits remarkable heterogeneity, characterized by higher values in the eastern marginal seas, the Red Sea, the Gulf of Aden and the Qinghai-Tibet Plateau, while lower in large areas of North Asia and Central Asia. Cratons show a lower mean heat flow and smaller standard deviation, indicating the tectonic stability. The Cenozoic rifts, marginal seas and the Neo-Tethyan Tectonic Domain all exhibit higher heat flow. The geothermal pattern in Asia is controlled by the geodynamic processes of the subduction of Pacific Plate, the Indo-Asia continental collision and the break-up between Arabia and Africa.

Review of geothermal conditions of Hungary

The heat flow map of Hungary was presented in the Atlas of Geothermal Resources in Europe in 2002 and was last updated in 2005. Since that time several geothermal projects, e.g. TransEnergy (2010-13), assessment of the geothermal potential of the Drava basin (2013) Paks-II, NPP (2016) and continuous drilling activity in the country have been in progress. Large amount of temperature data became available, which allowed the update of the Geothermal Database of Hungary and the compilation of an updated heat flow map and temperature maps.
 The heat flow is determined based on the Fourier law using the thermal conductivities of rocks and temperature gradient calculated from temperature observations in boreholes and wells. The thermal conductivity is known from laboratory measurements made on core samples. The thermal conductivities and the temperature data are stored in the Geothermal Database of Hungary.
 The heat flow is calculated in 2001 boreholes and wells using the Bullard-plot technique. The mean heat flow in Hungary is 90 mW/m2, varying between 30 mW/m2 and 120 mW/m2. The high values are found over buried basement highs in the eastern and southern part of the country, while the low values are located in the recharge areas of karstic flow systems. In the sedimentary basins, where the thickness of the Neogene and Quaternary sediments reaches 5-7 km, the heat flow is slightly below the mean value (80-90 mW/m2) due to the cooling effect of sedimentation. These basins contain the main thermal water aquifer in Hungary utilized for district heating and green house heating. The buried basement highs characterized by high heat flow (100-120 mW/m2) are potential sites to create artificial geothermal reservoirs by hydraulic fracturing (EGS).
 Temperature maps at 500 m, 1 km, 2 km and 3 km depths were also compiled. Similarly to the heat flow, the temperature anomalies strongly reflect the local and regional groundwater flow systems.

Flow-induced oscillation of membrane tapes and its effect on heat transfer of a transitional pipe flow

Flow-induced oscillation is an effective way for heat transfer enhancement, which embraces the advantages of requiring no extra energy consumption and better performance for preventing fouling or soot formation. In the present study, a thin membrane tape with length, width and thickness of 90 mm, 3.8 mm and 13.3 um respectively was mounted inside a horizontal pipe with an internal diameter of 13 mm. By visual measurement, the tape was demonstrated to be able to oscillate within airflow and the oscillation frequency was found to increase with the flow rate. Constant heat flux was applied at the pipe wall through electrical heating and the wall temperature was obtained by thermocouples. In low Reynolds number turbulent region (Re between 1800 and 4200), the mean heat transfer coefficient and flow resistance were found to be 1.3-1.7 times and 1.6-2.1 times than that of a smooth tube, respectively. However, the heat transfer enhancement effect is most pronounced at lower Re and as the Re increases, this effect becomes weak. Nevertheless, the spontaneous oscillating tapes can be a very promising heat transfer intensification element. This study is a primary investigation attempt and flow-induced oscillations of membrane tapes of different dimensions and the use of multiple membrane tapes are awaited to be studied deeply.

Geothermal Gradients and Heat Flow in Norte Basin of Uruguay

Progress obtained in a partial update of geothermal gradient and terrestrial heat flow values for the Norte Basin (Uruguay) are presented. It is based on results of temperature measurements carried out in deep water wells. Most of these wells have intersected the southern part of the Guarani Aquifer System, at depths varying from 200 to 1500m. In most of the Norte Basin it is a confined aquifer capped by the flood basalts of Cretaceous age. The results indicate that temperature gradients fall in the range of 15 to 45oC/km and the thermal conductivity of basalts have a mean value of 2.2W/m/K. Analysis of temperature distributions indicate that heat transfer takes place not only by conduction but also by upflow of groundwater with velocities in the range of 10-9 to 10-8 m/s. The representative mean heat flow values fall in the range of 30 to 85mW/m2. Maps of spatial distributions of geothermal gradients and heat flow values have been considered as indicative of the possible existence of an anomalous geothermal zone in the central-northwestern part of the Norte Basin. There are indications that this anomalous geothermal zone extends also to the eastern parts of adjacent regions in Argentina. Theoretical values derived on the basis of spherical harmonic expansion, employed in estimating geothermal gradients and heat flow points to a zone of relatively low heat flow in the other regions of the Norte Basin.

Capillary-assisted evaporation of water from finned tubes – Impacts of experimental setups and dynamics

Capillary-assisted thin-film evaporation is a promising approach to overcome the heat transfer challenges associated with sub-atmospheric evaporation of water in refrigeration applications. Consequently, thin-film evaporation is currently studied in several labs. However, so far it has been unclear whether results from different labs can be compared. In this work, we therefore investigate – for the first time – the impact of experimental setups and procedures on sub-atmospheric capillary-assisted thin-film evaporation of the refrigerant water and deduce methodological recommendations for improving reliability and comparability of measurement results. We present results of evaporation from finned copper tubes with decreasing filling levels from two different experimental setups:At higher driving force, the resulting dynamics of logarithmic mean temperature differences, heat flows and overall heat transfer coefficients determined in both setups are generally in good agreement but absolute values show deviations of up to 24%. For lower driving forces, the results are identical within uncertainty of measurement. We conclude that the impact of experimental setup is important when comparing absolute values from different setups, but obtaining comparable results is generally possible.Furthermore, we compare experiments with continuously decreasing versus constant filling levels and show that both procedures yield the same results within measurement uncertainty. With decreasing filling level, however, overall heat transfer coefficients are systematically 5–10% higher. Thus, experiments with continuously decreasing filling level are well-suited for a fast analysis of all filling levels in a single experiment.

Impact of magnetohydrodynamics (MHD) on energy transmission through ferrofluid saturating porous medium contained in a lid-driven trapezoidal container with triangular notched heater configuration

This article conveys numerical simulations for energy flow by mixed convection under the impact of magnetohydrodynamics (MHD) through ferrofluid saturating porous media contained in a trapezoidal enclosure having triangular notched heater at the bottom wall when the container’s top boundary is in motion with constant speed. The side and top walls of the container are assumed to be cold, the bottom wall is insulated, and the triangular notched heater supplies uniform heat to the fluid. Equations governing the flow are initially exposed to penalty scheme to eradicate pressure from momentum equations, and subsequently, the Galerkin weighted residual method is employed to compute the numerical solutions for velocity and temperature profiles. Computed solutions are expressed in form of graphs for streamline circulations, isotherms, and local and mean heat flow rates for suitable ranges of important physical parameters governing the flow, including the Darcy number (10−5 ≤ Da ≤ 10−3), Reynolds number (1 ≤ Re ≤ 10), Hartmann number (30 ≤ Ha ≤ 100), Prandtl number (0.062 ≤ Pr ≤ 10), concentration of solid ferroparticles (0.03 ≤ [Formula: see text] ≤ 0.15), and Grashof number (105 ≤ Gr ≤107). This investigation deduces that flow strength rises with escalation in the concentration of ferroparticles, as well as Darcy and Grashof numbers. The convection energy flow regime appears dominating for small Hartmann number and large Prandtl number. The mean energy flow rate is found to increase with increase in Darcy and Grashof numbers and it attenuates with escalation in the Hartmann number.

Sensitivity Analysis of Factors Affecting the Calibration of Heat-Flow-Meter Apparatus

Abstract The analysis and results of a sensitivity study of four procedural variables on the calibration response of two commercial heat-flow-meter apparatuses in conformance with ASTM Test Method C518, Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, are presented. The apparatuses ranged in plate size from 305 mm by 305 mm to 610 mm by 610 mm and were calibrated using Standard Reference Materials 1450c, Fibrous Glass Board, and 1453, Expanded Polystyrene Board, issued by the National Institute of Standards and Technology. A major objective of the study is to rank the relative importance of the factors and interactions affecting the calibration of the apparatus. Seventy-six runs were conducted under input conditions that varied the mean temperatures from 17°C to 30°C, temperature differences from 17 K to 30 K, heat flow up or down across the specimen thickness, and different circulation bath temperatures. For each apparatus and SRM, the experiment followed a full factorial design for the four factors and included three interspatial replicates to assess for temporal drift. The study revealed that mean temperature and heat flow direction were the two most important test method factors affecting the calibration of both apparatuses. Although the temperature effect was the same for both apparatuses, the heat flow direction effect was found to be instrument dependent. The study also found that the calibration factor for each apparatus was affected by the reference material utilized for calibration. Empirically derived predictive models for each apparatus SRM combination are presented covering the experimental region defined by the input test conditions.

Dynamical effects of multiple impacts: Large impacts on a Mars-like planet

The earliest stage of the evolution of a fully assembled planet is profoundly affected by a number of basin-forming impacts large enough to change the dynamics of its deeper interior. These impacts are in some cases quite closely spaced and follow one another in short time intervals, so that their effects interact and result in behavior that may differ from a simple sum of the effects of two individual and isolated impacts. We use two-dimensional models of mantle convection in a Mars-like planet and a simple parameterized representation of the principal effects of impacts to study some of the dynamical effects and interactions of multiple large impacts. In models of only two impacts, we confirm that the dynamical effects of the impacts reinforce each other the closer they are in space and time but that the effects do not always correspond to straightforward superpositions of those of single, isolated impacts. In models with multiple (4–8) impacts with variable sizes, distances, and frequencies, the global response of the mantle is as variable as the impact sequences in the short term, but in the long term the different evolutionary paths converge for several indicator variables such as the mean flow velocity, temperature, or heat flow. Nonetheless, beyond a certain impact frequency and energy, lithospheric instabilities triggered by large impacts occur on a global scale, reinvigorate mantle dynamics for long time spans, and entail a late stage of melt production in addition to the initial melting stage that is not observed in one- or two-impact models. After one or several very large impacts, some lithospheric material may founder and sink to the core–mantle boundary, and if enough of it accumulates there, it enhances the heat flux out of the core for several hundred millions of years, with possible effects on dynamo activity.

Geodynamo models with a stable layer and heterogeneous heat flow at the top of the core

The mean heat flow at the core–mantle boundary (CMB) could be less than the heat that can be transported by conduction along a core adiabat. If the difference is significant, it may render the top few hundred kilometres of the core to be stably stratified. The geodynamo then operates in deeper parts of the core, driven from the inner-core boundary by thermochemical convection. The CMB heat flow is probably strongly heterogeneous. Locally the thermal gradient below the CMB could be unstable while on average it is stable. The way in which lateral heat flux differences are accommodated and the consequences for the dynamics of a stable layer are not clear a priori. This is studied in numerical dynamo simulations with a strongly stabilizing average density gradient near the outer boundary and large lateral differences in the heat flux. The results suggest that a circulation in a thin layer immediately below the CMB balances the differences in heat flow by lateral advection. Deeper parts of the stable layer and the convecting region remain unaffected by the thermal heterogeneity at the CMB. A simple scaling theory for the shallow circulation layer is developed and is found to be in rough agreement with the numerical results. Applied to the Earth’s core, it predicts that the thickness of the layer is a few hundred metres, the horizontal velocity reaches values around 1 mm s−1, and lateral temperature differences at the CMB are slightly less than 1 K. The morphology of the magnetic field is found to be only marginally compatible with characteristic properties of the geomagnetic field when the stable layer thickness is around 400 km and is incompatible for a thicker layer. Therefore, the total CMB heat flow should exceed 10 TW unless unaccounted compositional buoyancy effects close to the CMB play a major role. If a sufficiently stable layer exists at the top of the core, thermal heterogeneity at the CMB would not influence the flow pattern in deeper parts of the core or affect heterogeneous growth of the inner core. Likewise, proposed mechanisms for the dipole offset from the centre of Mercury based on heterogenous CMB heat flow are unlikely to work if the upper part of Mercury’s core is thermally stable.

Interior structures and tidal heating in the TRAPPIST-1 planets

Context. With seven planets, the TRAPPIST-1 system has among the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Aims. We aim to determine interior structures for each planet and estimate the temperatures of their rock mantles due to a balance between tidal heating and convective heat transport to assess their habitability. We also aim to determine the precision in mass and radius necessary to determine the planets’ compositions. Methods. Assuming the planets are composed of uniform-density noncompressible materials (iron, rock, H2O), we determine possible compositional models and interior structures for each planet. We also construct a tidal heat generation model using a single uniform viscosity and rigidity based on each planet’s composition. Results. The compositions for planets b, c, d, and e remain uncertain given the error bars on mass and radius. With the exception of TRAPPIST-1c, all have densities low enough to indicate the presence of significant H2O. Planets b and c experience enough heating from planetary tides to maintain magma oceans in their rock mantles; planet c may have surface eruptions of silicate magma, potentially detectable with next-generation instrumentation. Tidal heat fluxes on planets d, e, and f are twenty times higher than Earth’s mean heat flow. Conclusions. Planets d and e are the most likely to be habitable. Planet d avoids the runaway greenhouse state if its albedo is ≳0.3. Determining the planet’s masses within ~0.1–0.5 Earth masses would confirm or rule out the presence of H2O and/or iron. Understanding the geodynamics of ice-rich planets f, g, and h requires more sophisticated modeling that can self-consistently balance heat production and transport in both rock and ice layers.

Terrestrial Heat Flow in Non-Thermal Ground Water Circulation Settings of Brazil

Data on Silica content of ground waters have been employed in obtaining estimates of heat flow for more than 500 localities, distributed over six tectonic provinces in Brazil. The procedure adopted is based on the use of an improved geo-thermometry relation for solubility of silica in ground waters. It is coupled with a revised interpretation of the empirical relation between silica content and heat flow, that allows for independent determination of the depth of circulation of ground waters. According to the results obtained mean heat flow values obtained for sedimentary areas of the late Proterozoic Sao Francisco basin and the Paleozoic Amazon basins are in the range of 45 to 47mW/m2. Similar range of heat flow values were found for the Precambrian Borborema province in the northeastern region of Brazil. Higher heat flow values of greater than 50mW/m2 were encountered for the eastern coastal area of Sergipe – Alagoas. On the other hand, Parana basin in southeast Brazil is found to have heat flow values higher than 55mW/m2. Such ranges of mean heat flow values are found to be in reasonably good agreement with those reported in earlier studies, using conventional methods. This trend is considered as indication that silica content of ground waters may be used for obtaining reliable estimates of conductive heat flow in areas where practical limitations impede use of conventional methods.

Thermohydraulics of rib-roughened helium gas running cooling channels for first wall applications

Improved cooling channel designs of helium cooled first wall (FW) applications focus on efficient heat transfer enhancement and reduced material temperatures, even for high incident heat flux densities of more than 0.5MW/m2. To this end, thermohydraulics of turbulent flow in a one-sided heated, one-sided rib-roughened channel with squared, round-edged cross section were predicted by Detached Eddy Simulations (DES) at Reynolds numbers ranging from ReDh=1.0E4 to ReDh=1.5E5 and at heat up rates ranging from q+=1.1E−3 to q+=7.48E−4, encompassing the envisaged operation envelope of helium cooled FW cooling channels. The rib-roughened channel wall consists of centrally positioned, transversally oriented rib elements with a rib-pitch-to-rib-height-ratio of p/e=10, a rib-height-to-hydraulic-diameter-ratio of e/Dh=0.0638 and a rib-width-to-channel-width-ratio of l/W=0.6. Mean flow and heat transfer quantities, turbulent fluxes and flow structures were analyzed. Anisotropic, large-scale eddies originated in separated shear layers are shed vertically and laterally to the flow. Maximum heat transfer correlates with regions of maximum span- and crosswise turbulent fluctuations and is located at the rib leading edge. Minimum heat transfer occurs within the region of the counter-rotating vortex behind the rib.

Geothermal studies in oilfield districts of Eastern Margin of the Gulf of Suez, Egypt

Results of geothermal studies carried out at 149 onshore oil wells have been used in evaluation of temperature gradient and heat flow values of the eastern shore of the Gulf of Suez. The investigations included temperature logs in boreholes, calculation of amplitude temperature, geothermal gradients and heat flow. The results obtained indicate that geothermal gradient values are in the ranges of 0.02–0.044°C/m and regionally averaged mean heat flow values are found to fall in the interval of 45–120mW/m2. Temperature gradients and heat flow values change from low values eastward to high values toward the axial of Gulf of Suez rift. The result of this research work has been highly successful in identifying new geothermal resources eastward of the Gulf of Suez. Additionally, this study shows that the areas with relatively higher temperature gradients have lower oil window, mature earlier, than those with low gradient values. Thus, high temperature gradients cause to expedite the formation of oil at relatively shallow depths and narrow oil windows. On the other hand, low temperature gradient makes the oil window to be quite broad when locate at high depths.

Validation and modification of modeling thermally activated building systems (TABS) using EnergyPlus

EnergyPlus (EP) integrates a low temperature radiant system module to evaluate thermal performance of radiant systems such as thermally activated building systems (TABS), but the assumptions in this module neglect thermal resistance of the pipe and thermal resistance between the pipe exterior surface and the pipe level, which may result in the inaccurate evaluation of TABS in terms of surface temperature and surface heat flow. In this paper, in order to validate this module used in EP, steady and transient heat transfer processes of TABS in buildings were studied by analytical solution, two-dimensional numerical simulation and EP simulation. The comparison shows that the assumptions indeed result in a largely overestimated cooling and heating capacity of TABS. In order to improve this radiant module, a simple solution of introducing a no mass material layer with the neglected thermal resistances to both sides of the pipe level was proposed. With this method, the results of mean surface temperature and mean heat flow show good agreement with that from analytical solution as well as numerical simulation. Furthermore, the results of the simulation coupling the modified module with room systems show very small deviation from the results found in the literature. In addition, the application of the modified module in a hollow core concrete deck structure with TABS was investigated.

High heat flow and ocean acidification at a nascent rift in the northern Gulf of California

The prevailing tectonic setting in the Gulf California suggests the presence of an undetermined number of short spreading centres with associated hydrothermal systems. However, to date, active seafloor spreading phenomena have been documented in only three of the eight tectonically active basins. Here we report heat flow values as high as 15,436 mW m−2 in two of the northernmost basins of the Gulf of California, providing evidence of intense hydrothermal activity associated with the transition from continental rifting to seafloor spreading. The mean heat flow for the Wagner and Consag basins area is 1,875 mW m−2, more than 15 times higher than the mean value for oceanic crust (105.4 mW m−2). Additional evidence for vigorous hydrothermal circulation and a shallow heat source includes intense gas discharge (CO2 and CH4), widespread low pH (average 7.7), locally high 222Rn concentrations in the bottom water and a high extent of organic matter maturation in the sediments.

Isothermal microcalorimetry provides new insights into biofilm variability and dynamics

The purpose of this study was to investigate a three-species in vitro biofilm with peri-implantitis-related bacteria for its variability and metabolic activity. Streptococcus sanguinis, Fusobacterium nucleatum, and Porphyromonas gingivalis were suspended in simulated body fluid containing 0.2% glucose to form biofilms on polished, protein-coated implant-grade titanium disks over 72h using a flow chamber system. Thereafter, biofilm-coated disks were characterized by scanning electron microscopy and fluorescence in situ hybridization/confocal laser scanning microscopy. To assess metabolic activity within the biofilms, their heat flow was recorded for 480h at 37°C by IMC. The microscopic methods revealed that the total number of bacteria in the biofilms varied slightly among specimens (2.59×10(4) ±0.67×10(4) cellsmm(-2) ), whereas all three species were found constantly with unchanged proportions (S.sanguinis 41.3±4.8%, F.nucleatum 17.7±2.1%, and P.gingivalis 41.0±4.9%). IMC revealed minor differences in time-to-peak heat flow (20.6±4.5h), a trend consistent with the small variation in bacterial species proportions as shown by microscopy. Peak heat flow (35.8±42.6μW), mean heat flow (13.1± 22.0μW), and total heat over 480h (23.5±37.2J) showed very high variation. These IMC results may be attributed to differences in the initial cell counts and relative proportions of the three species, their distribution and embedment in exopolysaccharide matrix on the test specimens. The present results provide new insights into variability and dynamics of biofilms on titanium disks, aspects that should be explored in future studies of dental surfaces.

Shallow geothermal regime in the Perth Metropolitan Area

Exploration of Perth's geothermal potential has been performed by the Western Australian Geothermal Centre of Excellence (WAGCoE). Detailed vertical temperature and gamma ray logging of 17 Western Australia Department of Water's (DoW) Artesian Monitoring (AM) wells was completed throughout the Perth Metropolitan Area (PMA). In addition, temperature logs from 53 DoW AM wells measured in the 1980s were digitised into LAS format. The logged data are available in the WAGCoE Data Catalogue. Analysis of the gamma ray logs yielded the first estimates of radiogenic heat production in Perth Basin formations. Values by formation ranged between 0.24 and 1.065 μW m−3. The temperature logs provide a picture of true formation temperatures within shallow sediments in the Perth Basin. A three-dimensional model of the temperature distribution was used to produce maps of temperature at depth and on the top of the Yarragadee aquifer. The temperature data were interpreted with a one-dimensional conductive heat model. Significant differences between the model and the observations was indicative of heat moving via non-conductive mechanisms, such as advection or convection. Evidence of non-conductive or advective heat flow is demonstrated in most formations in the region, with significant effects in the aquifers. Average conductive geothermal gradients range from 13°C km−1 to 39°C km−1, with sandstone formations exhibiting average gradients of approximately 25°C km−1, while insulating silt/shale formations show higher average gradients of over 30°C km−1. To produce preliminary heat flow estimates, temperature gradients were combined with thermal conductivities measured elsewhere. The geometric mean heat flow estimates range between 64 mW m−2 to 91 mW m−2, with the standard deviation of the arithmetic mean heat flow ranging between 15 and 23 mW m−2. The study characterises the shallow temperature regime in the Perth Metropolitan Area, which is of direct relevance towards developing commercial geothermal projects.

Analysis of the effects of heat sink temperature on single-phase natural circulation loops behaviour

During the past years, several authors performed numerical and experimental studies on single-phase natural circulation loops (thermosiphons-NCL). However the problem of the loop stability, which is of interest in many industrial applications, cannot be considered solved.This paper is focused on the evaluation of the instantaneous mass and heat flow rates in the main loop sections.The available experimental apparatus is provided with a heat sink which can be feed with cooling fluid at controlled temperature. In this way the NCL mean temperature and heat flow rate can be varied independently.A set of CFD simulations with various heat sink temperatures, at fixed heat flow rate, has been carried out in order to improve the comprehension of the data collected during the experimental campaigns.