Horizontal Flow Direction Research Articles

A robust and simple correlation for internal flow condensation

Accurate prediction of the heat transfer coefficient for internal flow condensation is essential for designing and optimizing condensers. Due to advances in manufacturing techniques and new environmental and safety regulations in recent years, applications arose with extensive use of microchannel condensers and low GWP refrigerants. Consequently, a new range of condensation flow conditions is emerging, which requires the evaluation of the accuracy of available correlations and the proposition of more accurate ones. In this work, the most extensive and updated experimental database for heat transfer coefficient (HTC) on internal flow condensation was gathered from the literature, which includes 69 working fluids, 12,017 data points, channel diameters ranging from 0.067 to 20.8 mm, and horizontal and vertical flow directions for smooth tubes. Correlations proposed from 1958 to 2023 were evaluated and compared to this database to verify their prediction error. A new simple HTC correlation was developed, showing that further improvement of available correlations is still possible. The new correlation predicted the database with a mean absolute error of 23.3 %, a 5.3 % relative improvement compared to the second-best-ranked and more complex correlation. This analysis showed that a few well-known dimensionless groups can accurately model the heat transfer process during condensation in a broad range of operational conditions.

Treatment Wetlands in Mexico for Control of Wastewater Contaminants: A Review of Experiences during the Last Twenty-Two Years

Constructed or treatment wetlands (CWs) are a sustainable option to clean wastewater in the face of water pollution problems. Consequently, this study was aimed at reviewing and analyzing the use of CWs in Mexico. This involved types, sizes, and functionality in the removal of pollutants, as well as the main plant species that are used. Furthermore, 67 studies regarding CWs were found, which were classified according to the treatment area as microcosms, mesocosms, pilot scale, and full-scale at 18, 30, 25, and 27%, respectively. The most used types of CWs are those of subsurface flow (87%) versus free-water surface (13%), of which horizontal flow direction (58%) are the most common. Considering Full-Scale CWs, the pollutant removal reported for COD, BOD5, TN, and TP oscillated between 50–90%, 60–90%, 30–90%, and 30–70%, respectively. Among the vegetation that is more used for Mexican CWs, 78 different species were detected; Typha and Cyperus hydrophytes species and ornamental flowering plants as Zantedeschia aethiopica., Canna genus., Heliconia genus, Hedychium coronarium, and Anturium andreanum species (plants with commercial value) were the most used plants. It was concluded that although there is an important advance in the use of ecotechnology as it is an attractive answer for decentralized wastewater treatment in Mexico, results revealed the need to migrate towards the use of CWs in full-scale size, in order to address real pollution problems. Thus, the further implementation of CWs in rural and urban regions with similar tropical and subtropical characteristics as in Mexico is suggested by the authors.

Effect of an applied magnetic field on Kelvin–Helmholtz instability driven by a laser under multi-mode disturbance

Kelvin–Helmholtz instability (KHI), as a fundamental physical process of fluids and plasmas, widely exists in astrophysics and physical phenomena of high energy density. In this paper, through radiation magnetohydrodynamic code, KHI is generated by the interaction between laser pulses and modulation targets in two-dimensional numerical simulations. Here, the evolution process of KHI vortices under different initial disturbance modes and with or without a horizontal external flow-direction magnetic field is investigated and compared from the perspectives of vorticity, magnetic pressure, magnetic tension, and longitudinal maximum kinetic energy. The simulation demonstrates that the external magnetic field in the horizontal flow direction inhibits the evolution of single-mode KHI vortices and the merging of multi-mode KHI vortices. The research results can provide theoretical guidance for KHI experiments using a high-energy-density laser device under a robust magnetic environment. They are also of significance to frontier research related to inertial confinement fusion.

Stratigraphic and structural control over permeability distribution in poorly consolidated siliciclastic rocks

Permeability models are very relevant for the characterization of oil systems. However, limitations related to the resolution of seismic data make it difficult to identify subseismic, sedimentary, and tectonic structures, which can significantly impact the flow pattern. This study analyzed the spatial variability of permeability according to stratigraphic and structural geology control to propose a useful model for poorly consolidated, fractured, and faulted siliciclastic reservoirs. In an outcrop analogue to this type of reservoir, air permeability was measured in 3 orthogonal directions at 24 points, spaced 2 m apart.The models were obtained by sequential Gaussian simulation (SGS) after statistical data treatment. The models were validated to ensure the consistency of the generated scenarios. Permeability values showed a positive asymmetric distribution and reduced medians toward tectonic structures. The fitted semivariogram model was exponential, with higher spatial continuity in the horizontal flow direction and lower in the vertical one. The permeability models emphasized the importance of considering subseismic structures in the flow analysis of reservoirs since they have proven to play a significant role in the permeability distribution in the outcrop assessed.

Laboratory testing of real-time flux measurements in fractured media

The In-Well Point Velocity Probe (IWPVP) was originally developed for use in screened porous media wells. The tool can characterize small-scale aquifer heterogeneity from wells that have been carefully developed to ensure an open screen and good hydraulic connection with the surrounding aquifer. This capability led to the hypothesis that the IWPVP could be adapted to characterize flow in fractured media, which features small-scale openings (i.e. fractures) that resemble screen slots. To test this hypothesis, a lab-scale fracture flow apparatus (FFA) was fabricated. The FFA consisted of two parallel acrylic plates that could be separated by a fixed distance, simulating a fracture with a known aperture. Two lengths of PVC well casing served as a cylindrical access port and were centrally placed in the plates. This mock-well left the interface with the fracture open – analogous to a fracture intersecting an uncased borehole. The probe was calibrated experimentally by relating known fluxes through the FFA with those measured inside the IWPVP. The ratio of these fluxes was found to be predictable for two aperture sizes (500 μm and 1290 μm), based on a flux balance and the Cubic Law. Additionally, the ability of the probe to discern flow direction in a fracture was tested and found to be accurate within ±20° under the conditions of the laboratory testing. The results suggest that an IWPVP could be reliably used in fractured media to directly measure horizontal flux and flow direction in a single fracture without reference to Darcy’s Law.

Investigation on CO2 permeation in water-saturated porous media with disordered pore sizes

CO2 sequestration in saline aquifers is considered to be a promising method for climate mitigation. Studies of the subsurface flow mechanisms of CO2–brine are important for evaluation of sequestration potential and security. However, this process is complicated by the intrinsic heterogeneity of reservoir rocks. The main objective of this study was to identify CO2 distribution and saturation related to changing injection conditions, and to comprehensively compare the characteristics of different drainage processes, under small scale heterogeneous condition. An X-ray computed tomography machine and a micromodel were introduced to investigate the CO2/brine drainage process from pore to core scale in a wide range of injection rates at static and transient states, respectively. Four types of drainage experiments were conducted. Horizontal and vertical (upward) flow directions in a micromodel setup at ambient conditions and vertical (upward and downward) flow directions in a core-flood setup at in-situ conditions. Based on experimental results, it is found that, a higher injection rate gives rise to a higher displacement efficiency but a lower sweep efficiency. The stability of CO2 displacing front become weak with drainage development. The difference in pore structure leads to different CO2 saturation variation with CO2 injection rates change. Even the sand pack is almost homogenous at core scale, the impact of heterogeneous porosity is enhanced with increasing flow rates in upward drainage, while it weakens in downward drainage.

Analysis of a horizontal flow closed loop thermal energy storage system in pilot scale for high temperature applications – Part II: Numerical investigation

The storage system investigated in this work, namely the CellFlux system, consists of a regenerator type thermal energy storage volume which is coupled to a heat exchanger by a circulating intermediate working fluid. The numerical simulations in this work are based on experiments conducted with a large scale pilot plant having a bed length of more than 10 m. The storage volume is of a novel design with horizontal flow direction and is filled with hollow bricks as sensible heat storage material. So far, most publications focus on packed bed storage systems, often with molten salt or oil, only few consider regularly shaped channels with gaseous flow. For the investigation in this part of the publication, a one-dimensional dispersion concentric model for channel flow is implemented in MATLAB/Simulink.The analysis in part I of this publication has revealed a radial flow maldistribution, which can be predicted by a correction function correlated beforehand. The commonly used assumption of plug flow, however, will be afflicted with an error. Thus, the aim of this work is to determine the accuracy of the model both under the plug flow assumption and the application of aforementioned correction function. Three single blow experiments, where the storage is charged or discharged from a uniform initial temperature, are compared to the numerical model. The average temperature deviation between experiment and simulation reaches up to 10% without the correction function, but improves significantly through its application and then ranges between 0.4% and 4.8%.Moreover, studies based on larger experiments have either not observed or generally not addressed the effect of a flow maldistribution. This appears to be an issue for small scale experiments where typically more sophisticated models are applied. If it was possible to model the entire storage volume with the present 1D model, the flow maldistribution effects could average out. Also, computing effort would be low and allow simulations on system level. This approach was taken only by few authors so far, particularly for packed bed systems and was also not experimentally verified. In order to correctly depict the experimental set up, the model considers the different composition of the interior, such as flow distributors and inlet/outlet cones as well as the thermal heat capacity of the walls and losses to the environment. As a result the model shows good agreement with the experiments: the mean temperature difference of the exit temperature between experiment and simulation during cyclic operation remained below 5%.

Effects of abnormal gravity on heat transfer of supercritical CO2 in heated helically coiled tube

Based on the RNG k-ε turbulence model, numerical analyses are carried out for the simulation of heating process of supercritical CO2 in the helically coiled tube in the aerospace fields. This study focuses on the influence of gravity on the supercritical CO2 heat transfer in two flow orientations: vertical and horizontal flow directions. The coupling effect of buoyancy and centrifugal force is analyzed to study the mechanism of heat transfer in helically coiled tube. Results reveal that the heat transfer coefficient is enhanced by bigger gravity force in the liquid-like region. The heat transfer coefficient exhibits a noticeable peak near the pseudo-critical temperature, but it remains almost the same in the gas-like region. Regardless of flow orientations, it has a weakening effect on the heat transfer with the low-gravity before the pseudo-critical point, whereas, it has a strengthen effect with the high-gravity. Finally, a new heat transfer correlation is proposed for the supercritical CO2 heating process covering a wide range from 0g to 6g.

The feasibility study of bridge construction plan in Digoel River Province of Papua

The planning of the bridge construction in Digoel river that connects the western part with the eastern part of Boven Digoel in Papua Province is part of the development program as stipulated in PP No 78 Tahun 2014 about” Acceleration of development in underdeveloped regions”. The land, river, and air transport systems that connect between regions in Boven Digoel are very difficult to be reached, also to extreme weather and climate conditions make the transportation cost expensive. One of the efforts to overcome these problems is to build road and bridge infrastructure. To support the implementation of infrastructure development in the district of Boven Digoel, a feasibility study of road and bridge planning is required. It refers to the guidelines Pd T-19-2005-B (Studi Kelayakan Proyek Jalan dan Jembatan). A feasibility study was undertaken to analyze in more detail some of the proposed road trace alternatives. Based on the feasibility study results, two alternatives of road trails connecting the western and eastern part of Boven Digoel of Papua Province are chosen. The bridge plans were made across the Digoel river. Bridge construction on alternative road trails connecting Kampung Ampera with Tanah Merah is considered to be more effective and efficient because it is safer from river scouring hazard. The bridge length is made longer than the width of the Digoel river, considering the rapid changes of the channel size. From the results of field measurement analysis, the average speed of the movement of the horizontal river flow direction is (80-180) x10(-4) meters/day so that in the 50-year period, the movement speed of the horizontal river flow path becomes (160 - 3200) meters. Based on Kun Qarshov method, the movement of the river flow for 50 years at the location of the bridge connecting Tanah Merah through Ampera Village is 311.64 meters so that the optimum bridge length at the location is designed 600 meters.

ПРИВЕДЕННЯ ДАНИХ ВИМІРЮВАНЬ ШВИДКОСТІ ВІТРУ ДО УМОВ ВІДКРИТОЇ МІСЦЕВОСТІ

Wind speed spatial distribution over the territory of Ukraine built based on weather stations measurements has been analyzed. Interpolated field of wind speed averaged over 1981-2010 indicated fairly heterogeneous structure with a number of artificial spots of larger/smaller values compared to surrounding areas. The main reason of such heterogeneity might be associated with representativeness of observation site regarding the landscape zone. It is well known that surrounding obstacles have a great impact on wind flow in horizontal direction. In order to solve this problem we have corrected sub-daily wind speed data measured at 207 meteorological stations of Ukraine for the period of 1981-2010 according to the open terrain conditions and the standard height (10 m). Generally, aerodynamic characteristics (e.g. surface roughness length) of measurement sites are needed in order to perform such adjustment. However, the only usable parameter available at a climatological reference book is horizon closure degree. The research revealed significant relationship between this characteristic and wind speed records (Pearson correlation coefficient equals -0.58). Given that horizon closure degree could not be used in correction procedure directly, surface roughness length has been calculated for 10 stations and statistical relationship has been determined between these two parameters. Based on the obtained relation and additional information we have found roughness length for all 207 stations at eight directions. Supplementary materials for analysis included observation sites description and Google Earth snapshots as well. In the final step, there has been applied a correction formula derived from the neutral logarithmic profile of wind speed in the atmospheric surface layer. The output of the research is new database of corrected wind speed measurements for the multiyear period. These results have been compared with observations. Mean 30-yr corrected speeds are featured by more homogeneous distribution over Ukraine and mostly higher values (with positive mean spatial bias ~0.35 m/s). The applied method allowed us to remove uncertainties related to differences in vertical level of measurements and considerably eliminate influence of the micro-scale terrain inhomogeneity. Obtained datasets may facilitate to perform spatial interpolation and further development of Ukrainian Wind Atlas.

Improving Performance of Treatment Wetlands: Evaluation of Supplemental Aeration, Varying Flow Direction, and Phosphorus Removing Filters

Pollutant removal was compared among subsurface flow constructed wetland (CW) mesocosms used for dairy farm wastewater treatment. Supplemental aeration, flow direction, and the use of phosphorus-reducing filters (PRFs) were varied among the CWs. The following were compared: (1) vertical flow CWs with and without supplemental aeration, (2) aerated CWs with horizontal and vertical flow directions, (3) single-cell and two-cell treatment systems, and (4) wetland-wetland systems (two CWs in series) and wetland-PRF systems (a CW followed by a PRF). The results from this investigation showed that, first, nearly all treatment strategies, either singly or in pairs, substantially reduced almost all the contaminants we tested. Second, supplemental aeration resulted in higher ammonium-nitrogen (NH4-N) removal efficiencies in aerated vertical flow CWs, compared to unaerated CWs. However, it caused no further improvement in dissolved reactive phosphorus (DRP), total suspended solids (TSS), E. coli, or BOD5 removal. Third, there was no difference between aerated horizontal and aerated vertical flow CWs in removal of any of the tested contaminants. Fourth, adding a second stage of treatment significantly improved DRP, TSS, E. coli, and NH4-N removal, but not BOD5. Finally, treatment systems with PRFs showed superior performance in DRP and E. coli removal.

An In-Well Point Velocity Probe for the rapid determination of groundwater velocity at the centimeter-scale

The In-Well Point Velocity Probe (IWPVP) is a novel device designed for obtaining rapid, initial measurements of groundwater velocity at the centimeter-scale using a standard monitoring well to access the subsurface. IWPVP measurements of groundwater speed are quantified on the basis of a mini-tracer test that is conducted within the body of the probe. Information regarding horizontal flow directions is obtained from differential responses at detectors placed in the four quadrants of the probe. The viability of the IWPVP design was confirmed by (1) numerical modeling that accounted for laminar flow in the porous medium outside the well and turbulent flow inside the well (and probe), and (2) a series of laboratory tank experiments in which the probe was calibrated to quantify seepage rates in a medium-grain sand. Laboratory tests were completed in less than 20 min in all cases, when seepage velocity was between 50 and 400 cm/day. The magnitude of the groundwater velocity was determined with a precision of ±7% on average, and accuracy of ±11% for seepage velocities up to 400 cm/day. The flow direction was determined within ±15°. The IWPVP appears to be a viable tool for rapid assessment of groundwater velocity.

Experimental investigation on the strength characteristics of cement paste backfill in a similar stope model and its mechanism

The strength comparison of cement paste backfill (CPB) in situ and laboratory exhibit contrary results both in some publications and case-based data. Based on this issue, this paper investigates the strength characteristics of CPB in a stope. A group of experiments in a large similar stope model (SSM) was designed for simulating the consolidation of CPB in a stope, then the unconfined compressive strength (UCS) test on specimens cored in the different position of CPB sample in SSM was conducted. Moreover, macrostructure (high-definition photography and borehole imaging) and microstructure (scanning electron microscopy, SEM) were carried out to help to explain the mechanism. The results indicate that: (i) the strength presents a wave-type change along the horizontal flow direction of paste; (ii) in the gravity direction, the strength decreases gradually from the bottom to the top of the SSM, and there exists sharp changes at some top sections of the SSM; (iii) SEM analyses indicated that the specimens of higher strength showed more compact structure and denser hydration products of Aft, C-S-H and Ca (OH). The strength characteristics of CPB in SSM can be explained by sediment dynamics combined with the macrostructure, microstructure, and 4 strength zones can be concluded accordingly. The studies may guide both backfill study and design.

Deformation in the lowermost mantle beneath Australia from observations and models of seismic anisotropy

AbstractObservations of seismic anisotropy near the core‐mantle boundary may yield constraints on patterns of lowermost mantle flow. We examine seismic anisotropy in the lowermost mantle beneath Australia, bounded by the African and Pacific Large Low Shear Velocity Provinces. We combined measurements of differential splitting of SKS‐SKKS and S‐ScS phases sampling our study region over a range of azimuths, using data from 10 long‐running seismic stations. Observations reveal complex and laterally heterogeneous anisotropy in the lowermost mantle. We identified two subregions for which we have robust measurements of D″‐associated splitting for a range of ray propagation directions and applied a forward modeling strategy to understand which anisotropic scenarios are consistent with the observations. We tested a variety of elastic tensors and orientations, including single‐crystal elasticity of lowermost mantle minerals (bridgmanite, postperovskite, and ferropericlase), tensors based on texture modeling in postperovskite aggregates, elasticity predicted from deformation experiments on polycrystalline MgO aggregates, and tensors that approximate the shape preferred orientation of partial melt. We find that postperovskite scenarios are more consistently able to reproduce the observations. Beneath New Zealand, the observations suggest a nearly horizontal [100] axis orientation with an azimuth that agrees well with the horizontal flow direction predicted by previous mantle flow models. Our modeling results further suggest that dominant slip on the (010) plane in postperovskite aggregates provides a good fit to the data but the solution is nonunique. Our results have implications for the mechanisms of deformation and anisotropy in the lowermost mantle and for the patterns of mantle flow.

An experimental study of gas sequestration efficiency using water alternating gas and surfactant alternating gas methods

Capillary trapping plays an important role in the geological storage of Carbon dioxide (CO2) because of its ability to immobilize a significant fraction of the injected gas. Numerous papers have investigated various factors that affect capillary trapping. Recently, gas-mobility control methods are being investigated through simulation studies, for improving capillary trapping of CO2 in saline aquifers. The results published so far are inconclusive and sometimes conflicting. In this study, a series of laboratory experiments was conducted to investigate and compare the effects of two mobility control methods namely, water alternating gas (WAG) and surfactant alternating gas (SAG), on gas sequestration efficiency. Efficiency was measured by injectivity and residual trapping capacity. The two methods were tested in both vertical and horizontal flow directions using rock samples of varying lithology and permeability. The different gas injection schemes were compared with the continuous gas injection method. WAG method consistently reduced residual gas saturations in all the experiments while SAG method significantly increased residual gas saturation for both horizontal and vertical flows. Comparison of performance of SAG method in horizontal flow with its performance in vertical flow revealed a significant increase in residual gas saturation when applied in vertical flow direction. However, SAG method resulted in decreasing injectivity as the SAG cycles increase while WAG injectivity remained unaffected throughout its cycles except in tight samples. Furthermore, higher residual gas saturations were observed in high permeability rocks compared to tight rocks when subjected to vertical-SAG sequestration method. The possible reasons for such efficiency in the vertical-SAG method are discussed in detail.

Mangroves buffer marine protected area from impacts of Bovoni Landfill, St. Thomas, United States Virgin Islands

One of the many ecosystem services that mangrove systems provide is their ability to act as buffers between the land and sea, protecting human development from storm surges while also trapping terrestrial pollutants. In St. Thomas, United States Virgin Islands, an ecologically-important mangrove system sits between Bovoni Landfill and a marine protected area, the St. Thomas East End Reserves. To characterize the physical processes driving this mangrove system, groundwater hydraulic head, sediment cores, sediment surface temperatures, and water and sediment chemistry were analyzed. Hydraulic head data from January to November 2014 were used to determine vertical and horizontal groundwater flow directions. Water and sediment samples were tested for heavy metals potentially originating from Bovoni Landfill. Stratigraphic context was provided by the sediment cores and used to infer past environmental conditions. Subsamples were taken from these cores and analyzed for dry bulk density, organic matter content (through loss on ignition), and heavy metals using electron microscopy. Vertical groundwater velocity and sediment porosity were determined by calibrating a one-dimensional finite difference heat transport model to near surface temperature data from depths of 0, 7, 14, and 21 cm. Groundwater was found to flow from the terrestrial upland, through the mangroves, and toward the ocean for the majority of the study. Flow reversal was seen after long periods of little precipitation. In the surface and shallow groundwater samples, trace metal concentrations were measured from 23 to 105 μg/L for Cr, Ni, Sn, and Zn. Sediment samples collected near the landfill contained Bi, Cr, Sn, Ti, and Zn. Very slow flushing of sediment pore water was indicated by the vertical groundwater velocities produced from the heat transport model, which ranged from ±10–7 to ±10–9 m/s. This study revealed that the mangrove system is an important buffer system protecting the outer lagoon of the marine protected area from terrestrial contaminants via sediment trapping and slowing of water fluxes from the upland area into the lagoon. The results presented here can be used as a baseline for future studies and are relevant to local managers and to landfill closure plans.

Effect of Flow Direction on Relative Permeability Curves in Water/Gas Reservoir System: Implications in Geological CO2 Sequestration

The effect of gravity on vertical flow and fluids saturation, especially when flow is against gravity, is not often a subject of interest to researchers. This is because of the notion that flow in subsurface formations is usually in horizontal direction and that vertical flow is impossible or marginal because of the impermeable shales or silts overlying them. The density difference between two fluids (usually oil and water) flowing in the porous media is also normally negligible; hence gravity influence is neglected. Capillarity is also often avoided in relative permeability measurements in order to satisfy some flow equations. These notions have guided most laboratory core flooding experiments to be conducted in horizontal flow orientation, and the data obtained are as good as what the experiments tend to mimic. However, gravity effect plays a major role in gas liquid systems such as CO2 sequestration and some types of enhanced oil recovery techniques, particularly those involving gases, where large density difference exists between the fluid pair. In such cases, laboratory experiments conducted to derive relative permeability curves should take into consideration gravity effects and capillarity. Previous studies attribute directional dependence of relative permeability and residual saturations to rock anisotropy. It is shown in this study that rock permeability, residual saturation, and relative permeability depend on the interplay between gravity, capillarity, and viscous forces and also the direction of fluid flow even when the rock is isotropic. Rock samples representing different lithology and wide range of permeabilities were investigated through unsteady-state experiments covering drainage and imbibition in both vertical and horizontal flow directions. The experiments were performed at very low flow rates to capture capillarity. The results obtained showed that, for each homogeneous rock and for the same flow path along the core length, the relative permeability and residual saturation are dependent on flow direction. The results were reproducible in all experiments conducted on the samples. This directional dependence, when accounted for in numerical simulation, can significantly improve simulation accuracy in the flow processes described.

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer.

Small-scale point velocity probe (PVP)-derived velocities were compared to conventional large-scale velocity estimates from Darcy calculations and tracer tests, and the possibility of upscaling PVP data to match the other velocity estimates was evaluated. Hydraulic conductivity was estimated from grain-size data derived from cores, and single-well response testing or slug tests of onsite wells. Horizontal hydraulic gradients were calculated using 3-point estimators from all of the wells within an extensive monitoring network, as well as by representing the water table as a single best fit plane through the entire network. Velocities determined from PVP testing were generally consistent in magnitude with those from depth specific data collected from multilevel monitoring locations in the tracer test, and similar in horizontal flow direction to the average hydraulic gradient. However, scaling up velocity estimates based on PVP measurements for comparison with site-wide Darcy-based velocities revealed issues that challenge the use of Darcy calculations as a generally applicable standard for comparison. The Darcy calculations were shown to underestimate the groundwater velocities determined both by the PVPs and large-scale tracer testing, in a depth-specific sense and as a site-wide average. Some of this discrepancy is attributable to the selective placement of the PVPs in the aquifer. Nevertheless, this result has important implications for the design of in situ treatment systems. It is concluded that Darcy estimations of velocity should be supplemented with independent assessments for these kinds of applications.

The CellFlux Storage Concept for Increased Flexibility in Sensible Heat Storage

Abstract Packed beds using air at atmospheric pressure as heat transferringmedium are the most cost effective systems for sensible heat storage. The basic idea of the CellFlux concept is to apply this concept also for liquid and/or pressurized primary HTFs by the introduction of an intermediate working fluid cycle. A heat exchanger is used for transferring energy between the primary HTF and the intermediate air cycle which eventually transfers the energy to a packed bed. The CellFlux concept can be implemented by using standard components. Essential is the minimization of efficiency losses resulting from the circulation of the air as well as the heat transfer processes within the heat exchanger and the storage volume. Some example cost estimations for the heat exchanger are given. The feasibility of the CellFlux concept has been proven by a pilot scale test facility operated at a maximum temperature of 380 °C and 100 kW. A novel approach promising further cost reductions has been applied by realizing a horizontal flow direction. Results from the theoretical and experimental analysis of the CellFlux concept will be presented. Distinctive for the CellFlux concept is the flexibility regarding working fluid (thermal oil, molten salt, pressurized water, CO 2 ), temperature range (0-800 °C), power (kW-multi MW) and storage medium (rocks, clinker bricks, concrete). This allows a wide range of applications. An example for application in combined heat and power will be given.

3-D numerical groundwater flow simulation for geological discontinuities in the Unkheltseg Basin, Mongolia

Groundwater models which realistically represent the hydrogeology of a complex system, like the Unkheltseg Basin, are critically important to Mongolia. They have flow on benefits to research, governments, management strategies and commercial development within the country. Limited case studies of calibrated 3-D numerical transient simulations in fault-controlled connection between basins, similar to the Unkheltseg Basin, are available in the public domain and the model presented here aims to address this problem. This basin is uniquely geologically controlled and a key water supply resource for future economic development in the Taikh Valley. Commercial exploration projects have produced the high-quality geological and hydrogeological data gathered, necessary for successful model simulation at a basin-wide scale. Using the “DRAIN Package” and “Fracture-Well Package FW4” in MODFLOW-SURFACT, the spatial discretization necessary to fully represent horizontal and vertical flow direction was achieved to effectively constrain recharge and discharge across the fault barrier. This model is an important tool for establishing a long-term monitoring programme in a fault-controlled basin, which predicts regional impacts, both short and long term.