Search

International audience; Concentrated Solar Power (CSP) technology captures solar radiation and converts it into heat for electricity production. It has received an increasing attention because integrated thermal energy storage (TES) systems can largely enhancing the reliability and the dispatchability. Over the last decade, low-cost single storage tank based on the thermocline technology becomes an alternative to commonly-used two-tank TES system. However, the improper inlet/outlet manifolds may cause the strong mixing of hot and cold fluids and disturb the temperature stratification, resulting in reduced thermal performances of the storage tank. This study aims at solving the flow maldistribution problem in the single-tank thermocline storage system by appropriately structuring the inlet/outlet manifolds. The technical solution is based on the insertion of optimized perforated baffles in the manifolds. 2D Computational fluid dynamics simulations were performed to calculate the transient flow and temperature profiles in the storage tank during the charging and discharging operations. The optimal size distribution of orifices on the upper baffle has been determined for homogenizing passage times of the thermal front, so as to enhance the temperature stratification. A novel intermediate evaluation indicator was introduced to characterize the real-time thermal behavior, which could reduce the computational cost of the optimization problem by a factor of 6 at least. Numerical results shown that the proposed optimization algorithm could significantly improve the thermal performances, indicated by the increased values of charging/discharging efficiency, the capacity ratio and the overall efficiency, ex., the fully charging efficiency be increased by 29% by comparing the unstructured manifold geometry and the one with optimized baffles. The parametric study on certain geometry and operating factors also demonstrated that the proposed method for flow distribution optimization was robust, effective and efficient.

Aquifer thermal energy storage (ATES) has been confirmed to be an effective thermal energy storage method and medium-to-high-temperature (MHT) ATES is receiving renewed interest. To illustrate the thermal performance of MHT ATES systems in the presence of natural regional groundwater flow and facilitate the future implementation of such systems, simulations including the effect of thermal dispersion are performed for a typical confined ATES system that consists of doublet wells and is operated in cyclic mode. The simulation model is validated using experimental data. The sensitivity of the system performance to hydrogeological and design/operation parameters is assessed using the thermal front, thermal breakthrough time, characteristic tilting time, and thermal recovery ratio. Based on the simulation results, the rules governing the influence of these parameters are presented and feasible storage site conditions and design/operation parameters for MHT ATES application are suggested.

Dissolvedorganic carbon (DOC) was determined at the Gerlache Strait, a coastal area off the Northern Antarctic Peninsula, in the austral summers of 2015 and 2016 during NAUTILUS I and II cruises, respectively. Hydrographic conditions in the area were very different between the study years. Despite that, the surface mixed layer displayed higher DOC concentrations compared to intermediate and deeper waters, as a result of the strong water column stratification, for both years. DOC accumulation on the surface is significantly related to the net community production (NCP), and stronger when the nitrate surface deficit (ΔNO3-) is higher (2016). The presence of a surface/subsurface thermal front at the central Gerlache Strait likely promotes the export of surface-produced organic carbon to deeper layers. A weak correlation between DOC and apparent oxygen utilization (AOU) suggests that the degradationof organic carbon in the deeper water column has a small role in oxygen consumption (less than 10%). This “recalcitrant” DOC characteristic below the surface layers observed in this study is similar to that found twenty years ago in the same area (FRUELA campaign, early Summer 1995). The Gerlache Strait allows, as an adequate regional scale study, assessments on the efficiency of the export and distribution of organic carbon in deep water masses in view of the observed trends of freshening, cooling, and lightening in the Antarctic Peninsula shelf waters.

This study aims to elucidate spatio-temporal variability of the thermal front in the eastern tropical Indian Ocean of the western Sumatera. The research was conducted during November 2017- February 2018. The Single Image Edge Detection (SIED) was applied to daily sea surface temperature (SST) data of 2016 of the level-3 Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) for the detection of thermal front. The number of the thermal front events during 2016 were 167 days. The distribution and frequency of thermal front mostly found in January, i.e. 23 days with SST mean of 30.3ºC. Whereas the lowest distribution appeared in November and the lowest frequency observed in September, i.e. 6 days with the SST mean of 29.1ºC. The highest temperature range of thermal front is between 31.4-32.0ºC and the lowest ranged between 26.4-29.3ºC. The occurrences of thermal front were commonly found in the open ocean. The highest frequency occurred in January and the lowest took place in September with the longest duration of 3 days.

To investigate the early life history of Seriola dumerili, we first validated otolith daily increments using reared fish (11?51 days after hatching). Four larval and early-juvenile S. dumerili were collected in May and July 2015 around the Penghu Islands, Taiwan (23.45?23.70 °N, 119.40?119.70 °E), by surface larval net towing, but not from drifting seaweeds. Seriola dumerili were caught at the thermal front, and the total lengths and ages ranged 7.4?42.5 mm and 18?56 days, respectively. Our results indicate that the hatching dates of S. dumerili were April to June and larvae may have been accumulated in the frontal zone before the juvenile phase., Ichthyological Research, 64(1), pp.145-150; 2017

Indonesia is a region that is directly adjacent to the Pacific Ocean and the Indian Ocean which allows a thermal front phenomenon. The purpose of this study was to identify the presence of thermal fronts based on seasonal variations and inter-annual variations in Indonesia waters. The data used in this study were Sea Surface Temperature (SST), Ocean Nino Index (ONI), and Dipole Mode Index (DMI) from January 2007 - December 2017 (11 years). The SST data was a level 3 Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image data with a resolution of 4 km. SST data was analysed using remote sensing techniques and Geographic Information System (GIS). The results of this study indicated that the distribution of SST and thermal fronts were influenced by seasonal variations and inter-annual variations. The highest average thermal front event in Indonesian waters occurred in a combination of El-Nino and Positive Indian Ocean Dipole (IOD) conditions. The highest average thermal front incidence in Indonesian waters also occurred during the East Season, while the smallest average occurred during the Transition Season II. During West Season, Transition Season II, and East Season, the largest number of thermal fronts was found in Western Indonesian Waters. Meanwhile, in the Transition Season I, the largest number of thermal fronts was found in Central Indonesian Waters. Thermal fronts were often found when the SST of Indonesian waters were cooler than normal conditions. The cooler condition made the SST more heterogeneous and formulated the thermal front phenomenon.

The need for information on potential fishing zones based on remote sensing satellite data (ZPPI) in coastal waters is increasing. This study aims to create an information model of such zones in coastal waters (coastal ZPPI). The image data used include GHRSST, SNPP-VIIRS and MODIS-Aqua images acquired from September 1st-30th, 2018 and September 1st-30th, 2019, together with other supporting data. The coastal ZPPI information is based on the results of thermal front SST detection and overlaying this with chlorophyll-a. The method of determining the thermal front sea surface temperature (SST) used Single Image Edge Detection (SIED). The chlorophyll-a range used was in the mesotropic area (0.2-0.5 mg/m3). Coastal ZPPI coordinates were determined using the polygon centre of mass, while the coastal ZPPI information generated was only for coastal areas with a radius of between 4-12 nautical miles and was divided into two criteria, namely High Potential (HP) and Low Potential (LP). The results show that the coastal ZPPI models were suitable to determine fishing locations around Nias Island. The percentage of coastal ZPPI information generated was around 90% information monthly. In September 2018, 27 days of information were produced, consisting of 11 HP sets of coastal ZPPI information and 16 sets of LP information, while in September 2019 it was possible to produce 29 days of such information, comprising 11 sets of HP coastal ZPPI information and 18 LP sets. The use of SST parameters of GHRSST images and the addition of chlorophyll-a parameters to MODIS-Aqua images are very effective and efficient ways of supporting the provision of coastal ZPPI information in the waters of Nias Island and its surroundings.

San Jorge Bay (23° S) is characterised by a permanent coastal upwelling front and a thermal front that influence water circulation into the bay. This bay constantly receives effluents from different mining activities. Several studies have demonstrated different levels of heavy metals in waters and sediments within the bay. The clam Protothaca thaca is a bivalve with sedentary habits, which is distributed along the Peruvian and Chilean coasts and is exploited commercially. During 2010, clams were collected inside the bay: north (La Chimba), centre (Paraiso) and south (Llacolen), as well as from a site outside the bay (Bolsico). Haematological parameters, condition factor index, lesions, parasites and pathogens and heavy metal concentrations in clam tissues were determined. The health indicators of clams inhabiting the bay varied between sites. Clams inside the bay showed higher prevalence and intensity of parasites and lesions than those clams inhabiting the site outside the bay, which could be indicating the presence of some environmental stressor (e.g. heavy metals). This study is the first to evaluate the health status of organisms from San Jorge Bay, and our results support the hypothesis that clams P. thaca can be used to evaluate environmental quality.

The currents of the northern shelf of the Yellow Sea are investigated using observations of current and hydrography and numerical current model results. The Regional Ocean Model System (ROMS) with a horizontal resolution about 1km is implemented for the Yellow Sea and the Bohai Sea, and the results are produced for the year 2014 and 2015. Observations from bottom moored ADCP profilers and CTD on the northern shelf of the Yellow Sea are used for validation of the model. The comparison of current time series and bottom temperature evolution show good agreement between model and observation. Barotropic tides are the dominant current component throughout the year on the shelf and consistently mixing the water column in the shallower parts. A thermal front and associated jet exists during the summer creating a robust current structure on the western part of the shelf. The winds in the region are changing constantly creating episodic currents in the upper part of the sea lasting from hours to a couple of days. publishedVersion

Summer hydrographic data from 1971 to 2000 demonstrate the presence of bottom cold water (BCW) and a bottom thermal front around the BCW in a semienclosed sea in the Seto Inland Sea of Japan. The horizontal gradient of water temperature across the bottom front was larger in neap tide than in spring tide, which is the opposite the pattern observed in the fortnightly variations in other areas (e.g., the Irish Sea). A numerical model for the Inland Sea reproduced the presence of BCW and a bottom front as well as the same fortnightly variation in the horizontal gradient of water temperature across the bottom front as in observational data. Being the same BCW as those in other areas, the presence of BCW in the Inland Sea is also caused by spatial variation in tidal mixing. The intensification of the bottom front in neap tide in the Inland Sea results from a combination of tidal mixing and horizontal advection of warm water to the BCW. The presence of a bottom residual current in the direction across the bottom front results in the horizontal advection of warm water to the BCW, and its fortnightly variation is responsible for the fortnightly variation of the bottom front in the Inland Sea. The presence of the BCW induces a surface cyclonic circulation in the direction approximately along the bottom front; the intensification and weakening of the bottom front with the spring–neap tidal cycle, combined with the fortnightly variation in the bottom boundary layer thickness, produce a slightly stronger surface cyclonic circulation in neap tide than in spring tide.

Commercial exploitation of geothermal resources requires the disposal of large volumes of cooled brine in an environmentally acceptable way. Reinjection of cooled (i.e. spent) geothermal water has become a standard reservoir management strategy. Since injected fluids are typically much colder than the reservoir rock, this strategy results in the cooling of the region around the injection wells. Injected cool water may not have sufficient residence time in the reservoir to receive enough heat from surrounding hotter rock, resulting in temperature decrease at producing wells. Usually, the energy transport in geothermal reservoirs is calculated by use of sophisticated numerical simulators. In this paper we present analytical solution of simplified model of mass and heat transfer in fractured porous medium in one dimension, assuming constant rock temperature and neglecting small-scale effect connected with dispersion and heat conduction. The solution presented in this paper is applicable if thermal capacity of rock is high but the specific area is not sufficient for instant thermal equilibrium. This approach allows for better understanding the relation between fluid movement along the fractures and heat transfer between the rock matrix and fluid. Simple numerical experiments reported in the paper have shown the importance of specific surface area of naturally fractured rock, which influences the rate of exchange of heat between the fractures and the rock matrix.

This work presents the development of improved tracer techniques for monitoring internal temperatures and cooled fractions in water saturated porous media. The analysis is based on reactive chemical compounds whose hydrolysis reactions allow for accurate temperature measurements. The tracers are designed to improve geothermal reservoir management procedures. Thermo-sensitive tracers will provide valuable information about the thermal state of the examined permeable media. This is demonstrated by means of laboratory experiments with sand-packed columns. The special heating/cooling setup provides a defined internal temperature distribution. In 70 independent experiments, tracer sensitivity was examined. Practical limitations in three different experimental schemes, flow-through, moving thermal front and push–pull, were investigated. The results show that thermo-sensitive tracers can be used to measure temperatures and cooled fractions with high precision and accuracy.

Interannual variability of thermal front west of Luzon Island during the winter of 1993–2013 is examined with the method of singular value decomposition (SVD) and a suite of satellite measurements in this paper. It is found that both the area and intensity of the thermal front west of Luzon Island show apparent interannual variability. Further study based on SVD shows that the interannual variability of the thermal front is highly associated with El Nino and Southern Oscillation (ENSO), and the correlation coefficient between Nino3.4 index and the first Principal Component (PC1) of thermal front can reach–0.65. The mechanism can be described as follows. In El Nino (La Nina) years, the East Asian winter monsoon (EAWM) is weakened (enhanced), inducing weaker (stronger) local wind stress curl (WSC) west of Luzon Island, and resulting in weakened (enhanced) Luzon cold eddy, which finally leads to the weakening (enhancement) of the thermal front.

We carried out an integrated reservoir characterization to model a heavy oil reservoir called Balol located in the heavy oil belt of Mehsana in the western state of Gujarat in India. The Oil and Natural Gas Corporation of India was the field operator. The operator adopted in situ combustion process in northern part of Balol because of high-mobility contrast between oil and water. However, the performance review carried out by the operator found that oil recovery from this field was not as per prediction. Hence, serious attempts were made to interpret 3D seismic data to map the reservoir efficiently. We integrated the information derived from 3D time-lapse seismic data with the well logs provided by the operator to explain the movement of thermal front tracked using time-lapse seismic data. To model the reservoir, flow unit and electrofacies characterization was also carried out, and four to five FUs with conduits and baffles to flow were identified. Electrofacies analysis identified three major reservoir facies. These analyses also revealed that Balol reservoir was layered and heterogeneous with depth. Further, in addition to 3D seismic data, well logs and empirical equations were used to generate porosity, water saturation, and permeability models for the entire reservoir. Thus, a reservoir model with heterogeneous distribution of petrophysical properties was generated. We observed a high permeability trend in the northwest direction at injection wells, which could be governing the movement of thermal fronts in the reservoir.

The results of numerical modeling of hydrodynamic processes that occur during the period of existence of an autumnal thermal bar in Kamloops Lake, Canada are presented. These results were obtained using a nonhydrostatic 2.5D model in the Boussinesq approximation with allowance for the diurnal variability of radiative and turbulent heat fluxes at the surface of the lake. A series of numerical experiments with various values of water mineralization in the Thompson River have been performed. The calculations show that the mineralization of inflow river waters has a significant effect on the dynamics of horizontal movements of the thermal front and on the pattern of circulation flows induced by the thermal bar during the period of lake cooling.

Modern sea surface temperatures (SSTs) were estimated from UK′37 values of ten core-top sediment samples collected under the Cabo Frio upwelling system and validated by comparison with satellite-derived SSTs. UK′37-SSTs were found to reflect annual SST means in the offshore area and seasonal means (winter/spring) in the inshore and central areas. The latter areas are mainly influenced by upwelling processes whereas the offshore area is under the influence of the thermal front of the Brazil Current (BC). SST variability during the last century was then reconstructed from three short sediment cores. The record showed a general cooling trend in the inshore and central areas, suggesting intensification of the upwelling process. The trends at the offshore area reflected oscillations of the BC thermal front, with piling up of warmer BC waters closer to the coast since ca. 1950.

Two major temperature fronts, the Subpolar (Gosung, Gang-won-do; $38^{\circ}-41^{\circ}N$ ) and Thermal (Jukbyun, Gyeong-sang-buk-do; $36^{\circ}-37^{\circ}N$ ) fronts, are found in the East Sea along the east coast of Korea. These are located roughly where the Tsushima Warm Current and North Ko...

The primary mode of deactivation of automotive emission control catalysts is thermal aging, and it is well-known that high-temperature lean aging conditions are particularly detrimental. Since evaluating the long-term durability of automotive catalysts is costly and time-consuming, rapid catalyst aging cycles have been developed to mimic (in a reduced time) the catalyst deactivation under real-world driving conditions. One of the commonly used rapid catalyst aging tests is an exothermal aging cycle, which involves a combination of fuel-rich engine operation and supplemental air injection to generate high-temperature lean conditions within the catalyst bed. In this work, we use the previously developed transient three-way catalyst model to investigate the time evolution of the axial temperature profiles and exhaust air–fuel ratio (A/F) along the catalyst bed during the course of the exothermal rapid aging cycles. We find that the thermal front propagates downstream through the catalyst bed relatively slowly (compared to the concentration front) and this can limit the location within the catalyst bed and duration for high-temperature lean exposure. We also investigate how variations of some of the key system design and operating parameters can affect the extent and duration of high-temperature lean exposure. Finally, a simple analytical expression is developed which allows one to estimate the time it takes for the thermal front to travel through the catalyst bed. This time can be compared with the period of the lean A/F operation during the aging cycle to determine the location and duration of high-temperature lean exposure.

Reactive tracers have long been investigated as a means to measure geothermal temperature profiles and predict thermal breakthrough, but this method has only been used in practice to estimate an effective (or average) reservoir temperature. This means that spatial information about the temperature profile is lost, and a sequence of reactive tracer tests would need to be carried out at different times to track the thermal front. Advances in nanotechnology have made the use of nanoparticles as geothermal tracers feasible. Nanomaterials can be designed with a high degree of control over their response to temperature, which could enable them to provide more information than reactive solute tracers. Nanoreactors that prevent reaction of encapsulated reactants from occurring until a threshold temperature is reached are a promising candidate for use as geothermal temperature sensors. It is demonstrated through modeling that this could enable engineers to determine the location of temperature measurements to map the inter-well temperature profile at a given time. This could facilitate more accurate reservoir fracture geometry characterization and thermal breakthrough prediction.

A control strategy of flow reversal with hot gas withdrawal for heat recovery was developed and verified for the mitigation and utilization of ventilation air methane (VAM) in a reverse flow reactor. The flow reversal strategy was based on the thermal front propagation velocity and a logic-based controller was built to avoid catalyst deactivation and reaction extinction caused by prolonged rich or lean feed conditions; the utilization of heat released from VAM combustion was considered through heat extraction by withdrawing part of hot gas from the middle of the reactor. By means of simulation using a one-dimensional heterogeneous model, the results revealed that the flow direction should be reversed before the temperature peak passing through the middle of the reactor to reduce the discharge of unreacted methane as well as to enhance the heat recovery efficiency; a fixed (relatively short) switching time is reasonable for the reactor operation in the case of hot gas withdrawal. The stability and autothermicity of reverse flow reactor are jointly influenced by the feed concentration and hot gas withdrawal fraction; the reactor can only be run stably in a narrow operating window (stability area). Heat recovery and bed temperature regulation are achieved mainly by hot gas withdrawal, while air dilution and extra methane injection are the auxiliary manipulated variables to sustain the reaction in some extreme circumstances. An extra catalyst bed along the way to the boiler is effective to enhance the overall methane conversion by oxidizing the unreacted methane. A case study under modified real ventilation conditions shows that the control strategy developed in this work is feasible to mitigate and utilize VAM if the methane content is higher than 0.2 vol.%.

We use a continuum model of reservoir evolution to explore the interaction of coupled thermal, hydraulic and chemical processes that influence the evolution of seismicity within a fractured reservoir from stimulation to production. Events occur from energy release on seeded fractures enabling moment magnitude, frequency and spatial distribution to be determined with time. Event magnitudes vary in the range −2 to +2 with the largest event size (~2) corresponding to the largest fracture size (~500 m) and a prescribed stress drop of 9 MPa. Modelled b-values (~0.6–0.7) also correspond to observations (~0.7–0.8) for response in the Cooper Basin (Australia). We track the hydrodynamic and thermal fronts to define causality in the triggering of seismicity. The hydrodynamic front moves twice as fast as the thermal front and envelops the triggered seismicity at early time (days to month) – with higher flow rates correlating with larger magnitude events. For later time (month to years), thermal drawdown and potentially chemical influences principally trigger the seismicity, but result in a reduction in both the number of events and their magnitudes.