Minimum Flow Rate Research Articles

CFD investigations of a shape-memory polymer foam-based endovascular embolization device for the treatment of intracranial aneurysms.

The hemodynamic and convective heat transfer effects of a patient-specific endovascular therapeutic agent based on shape memory polymer foam (SMPf) are evaluated using computational fluid dynamics studies for six patient-specific aneurysm geometries. The SMPf device is modeled as a continuous porous medium with full expansion for the flow studies and with various degrees of expansion for the heat transfer studies. The flow simulation parameters were qualitatively validated based on the existing literature. Further, a mesh independence study was conducted to verify an optimal cell size and reduce the computational costs. For convective heat transfer, a worst-case scenario is evaluated where the minimum volumetric flow rate is applied alongside the zero-flux boundary conditions. In the flow simulations, we found a reduction of the average intra-aneurysmal flow of > 85% and a reduction of the maximum intra-aneurysmal flow of > 45% for all presented geometries. These findings were compared with the literature on numerical simulations of hemodynamic and heat transfer of SMPf devices. The results obtained from this study can serve as a guide for optimizing the design and development of patient-specific SMPf devices aimed at personalized endovascular embolization of intracranial aneurysms.

Adaptive (re)operations facilitate environmental flow maintenance downstream of multi-purpose reservoirs

Multi-purpose reservoirs support socioeconomic development by providing irrigation, domestic water supply, hydropower, and other services. However, impoundment of water impacts instream aquatic ecosystems. Thus, the concept of minimum environmental flows (MEFs) was established to restore the benefits of naturally flowing rivers by specifying minimum flow rates to be maintained downstream of dams. But varying legislative contexts under which multi-purpose reservoirs operate may not always necessitate MEF releases. To what extent the release of MEF affects other sectoral benefits remains an open-ended and possibly a site-specific inquiry. A related issue is − how does the order in which releases are prioritized influences sectoral performances? We analyse these issues for the Nagarjuna Sagar reservoir, one of the largest multipurpose reservoirs in southern India. We formulate two versions of a multi-objective decision problem. PF_MEF formulation prioritizes MEF releases over releases for water demand satisfaction, followed by hydropower releases. PF_nMEF formulation follows the regional legislative rule releasing first for demand satisfaction, followed by hydropower and MEF releases. The objectives include: annual demand deficits (minimize), hydropower production (maximize), reliability of maintaining MEF (maximize), and reliability of non-exceedance of high flows downstream (maximize). A dynamic rule using radial basis functions (RBFs) specifies releases as a function of reservoir storage and the Borg multi-objective evolutionary algorithm is used to identify the Pareto approximate solutions. The reliability of MEF satisfaction, annual demand deficits, and hydropower production attained across the Pareto-optimal strategies obtained for PF_MEF (PF_nMEF) formulation is 86–99 % (63–80%), 47–1063 (17.6–340) Mm3, and 3452–3703 (3408–3650) GWh, respectively. Results thus indicate that prioritizing MEF releases improves can meet MEF requirements without significant compromises in other objectives. We hypothesize that similar investigations may reveal how simple modification of release order may improve ability of other reservoirs to meet environmental goals.

A novel solar-driven vacuum desalination unit: Simultaneously venturi-induced self-evaporation and self-condensation with fresh water cycle

Integrating solar energy in desalination processes offers a cost-effective and efficient solution. Moreover, reducing the saturated temperature of water vapor through pressure reduction can lower energy consumption and improve evaporation rates. This study investigates the performance of a novel venturi system integrated with an evacuated tube collector (ETC) that simultaneously conducts low-pressure evaporation and condensation. The research evaluates the system’s response to variations in flow rate and explores the potential for reducing freshwater pump activity to conserve energy. Increasing the flow rate led to a greater pressure differential across the venturi, causing a decrease in throat pressure. The system achieves its peak water production at a flow rate of 75 L per minute (LPM), yielding 9.02 kg/m2 with a system pressure of 0.297 bar. This production signifies a notable surge of 37.01 % compared to the recorded minimum flow rate. The cost analysis indicates that the cost of producing one kilogram of water per unit area is $0.045. The system achieved its maximum efficiency of 40.87 % by decreasing the water pump operation time to 1.5 h/day while following a cycling pattern of 5 min on-15 min off.

Improving near-stall performance of axial flow compressors using variable rotor tandem stage. A steady analysis

This paper investigates the idea of substituting the first stage of a conventional axial-flow compressor and its inlet guide vane (IGV) row with a variable rotor tandem (VRT) stage to reduce the size and weight of axial-flow compressors. It is expected that a tandem stage gains higher pressure ratio than a conventional stage, and simultaneously, its variable stagger rotor provides more flexibility in handling unsteady phenomena at low mass flow rates. A three-dimensional numerical model based on Reynolds-Averaged Navier–Stokes equations is developed to conduct this investigation. To validate the numerical model, experimental tests are conducted on a tandem single-stage axial-flow compressor test bench in the Dana laboratory of Amirkabir University of Technology, to compare the performance map with numerical results. The validated numerical model is then employed to simulate the performance of both front and aft variable rotor blades. The proposed tandem stage effectively performs the IGV duty, suppresses instabilities at low mass flow rates, and eventually extends the compressor's stable operational range. This proves that a VRT stage is an efficient active surge-control system tool. The detailed survey of the three-dimensional flow field reveals that the aft tandem rotor blade stagger angle is more effective in increasing the stall margin and decreasing the minimum operational mass flow rate than the front row of blades. It is observed that when the aft blades rotate in the direction of decreasing the tandem blades' gap area, the flow momentum increases and causes the compressor stability at lower mass flow rates.

Experimental and numerical studies on spray cooling of a downward-facing surface under partial coverage of multi-nozzle sprays

A new experimental study (aka SPAYCOR-S2) on multi-nozzle spray cooling of a downward-facing heater surface is conducted on the SPAYCOR facility at KTH, to provide data assessing the feasibility of spray cooling for in-vessel melt retention (IVR) in light water reactors. It is intended to investigate the potential for reducing the number of nozzles for spray cooling of an 80 mm × 120 mm surface, from the 2 × 3 nozzle array in the previous study (Bandaru, 2021) to a 2 × 2 nozzle array in the present study. Given the same heater surface, the pitch-to-diameter ratio is enlarged in a 2 × 2 nozzle array, resulting a partial coverage of the spray cones of four nozzles, in contrast with the 2 × 3 nozzle array where the heater surface was fully covered by six-nozzle spray. The tests focus on the cooling performance of such partial coverage of multi-nozzle spray and the effects of heater surface’s inclination angle. The experimental results reveal that the inclination angle of the heat surface has a negligible impact on cooling capacity, although it is slightly higher on the surface inclined at 90° than on the surfaces inclined at 45° or 60°. The maximum steady heat flux of the 2 × 2 nozzle array at its minimum spray flowrate is determined as 1.96 MW/m2. A numerical study on the spray cooling of the 2 × 2 nozzle array is also performed with models in OpenFOAM, which are extended from our previous development (Fang, 2023) by adding models for thin-film boiling and conjugate heat transfer in solid. For validation of the numerical study, the spray cooling of the heater surface inclined at various degrees is simulated, and the results are compared with those of experiment. The simulation generally shows good correspondence with experiments.

Achieving efficient hardfacing on stainless steel using single SiC powder in laser directed energy deposition

Generally, in a laser hardfacing process, a mixture of ceramic and metal powder is used to clad a hard surface, resulting in enhanced wear characteristics of metal parts. This study proposes an efficient hardfacing process that uses a single and minimal amount of ceramic powder (0.079 g/min in this work). This process, named as Laser Directed Energy Deposition of Minimal Ceramic Powder (LDED-MCP), features that the melt pool is generated inwardly because only the substrate participates in forming the melt pool. Furthermore, due to the minimal powder flow rate used and sparse particle-melt pool collision events, ripple formations leading to the convective melt pool flow and inhomogeneous microstructures would be suppressed. Consequently, the produced layer is nearly flat and free of incompletely melted metallic particles, thus minimizing post-machining. For a 316 L substrate and SiC powder material combination, a crack-free layer about 560 μm thick with an average hardness of about 417 HV was created through process parameter optimization. This layer showed a eutectic structure composed of γ-austenite and chromium carbides, partially melted SiC particles between dendrites, and in-situ synthesized SiC nanoparticles decorating the cell walls. Through this work, near-net-shape hardfacing of stainless steels is realized through LDED-MCP process minimizing powder pre-processing and post surface machining.

Improvement of inert-gas distribution for fuel tanks with the objective of minimum bleed flowrate

PurposeTo ensure the safety of aircraft fuel tanks, the FAA issued an airworthiness clause (25.981(b)) suggesting that the risk of combustion and explosion be reduced by installing a Flammability Reduction Means or an Ignition Mitigation Means. The airflow distribution method has a significant effect on the inerting performance. Therefore, this study aims to determine an optimum airflow distribution method of the inerting system.Design/methodology/approachThis paper establishes the calculation model of the oxygen concentration in the ullage of a multi-bay fuel tank, calculates the oxygen concentration in the ullage of an aircraft tank in single-flow and dual-flow modes under series and parallel ventilation methods and analyses the inerting performance of the tank under different airflow distribution methods.FindingsThe results show that: (1) the bleed flow rate required to achieve whole process inerting of multi-bay fuel tank in dual-flow mode is lower than that in single-flow mode; (2) under the parallel ventilation method, the decrease of oxygen concentration and the uniformity of each bay are better than that in the series ventilation method; (3) dual-flow mode staged ventilation method can be used to achieve the whole process inerting of the tanks under the minimum engine bleed consumption.Originality/valueThe novelty of this paper is to analyze and optimize the airflow distribution method of the inerting system under the whole flight envelope to minimize the engine bleed consumption.

Assessing the Performance of a Dual-Speed Tool When Friction Stir Welding Cast Mg AZ91 with Wrought Al 6082.

A novel dual-speed tool for which the shoulder and pin rotation speeds are separately established was utilized to friction stir weld cast magnesium AZ91 with wrought aluminum 6082-T6. To assess the performance and efficacy of the dual-speed tool, baseline dissimilar welds were also fabricated using a conventional FSW tool. Optical microscopy characterized the weld microstructures, and a numerical simulation enhanced the understanding of the temperature and material flow behaviors. For both tool types, regions of the welds contained significant amounts of the AZ91 primary eutectic phase, Al12Mg17, indicating that weld zone temperatures exceeded the solidus temperature of α-Mg (470 °C). Liquation, therefore, occurred during processing with subsequent eutectic formation upon cooling below the primary eutectic temperature (437 °C). The brittle character of the eutectic phase promoted cracking in the fusion zone, and the "process window" for quality welds was narrow. For the conventional tool, offsetting to the aluminum side (advancing side) mitigated eutectic formation and improved weld quality. For the dual-speed tool, experimental trials demonstrated that separate rotation speeds for the shoulder and pin could mitigate eutectic formation and produce quality welds without an offset at relatively higher weld speeds than the conventional tool. Exploration of various weld parameters coupled with the simulation identified the bounds of a process window based on the percentage of weld cross-section exceeding the eutectic temperature and on the material flow rate at the tool trailing edge. For the dual-speed tool, a minimum flow rate of 26.0 cm3/s and a maximum percentage of the weld cross-section above the eutectic temperature of 35% produced a defect-free weld.

Flow Distribution in Molten Salt Receiver Panels at High Flux Gradients

This paper presents a simulation study on critical mass flow distributions in receiver panels of commercial-scale molten salt towers (MST). Despite sophisticated aimpoint optimizations, the flux density distribution on an MST receiver in actual operation contains significant vertical and horizontal gradients. This study investigated how the latter affects the mass flow distribution among the parallel absorber tubes in each panel. A parametric study applied a discretized dynamic thermohydraulic model of a commercial scale receiver design, highlighting at which mass flow rates, flux density gradients and mean flux densities the flow distribution can become critical. Excessive temperature developments were observed, suggesting maintaining appropriate minimal mass flow rates to avoid damaging tube walls and the molten salt chemistry.

Calculation of the required methanol consumption during the flow of wet hydrocarbon gas in a horizontal pipeline

One of the main problems that have to be solved during the development of hydrocarbon deposits is the formation of gas hydrates in pipelines. In this regard, the article presents a preventive method to struggle against the formation of gas hydrate deposits on the pipes inner walls associated with the supply of a hydrate formation inhibitor to the gas stream. The research was conducted on the basis of a mathematical model of the wet hydrocarbon gas flow in a horizontal pipeline. The research object is to determine the minimum required consumption of methanol, in which there is no formation of gas hydrate deposits on the channel inner walls. The practical significance of this study is that it is aimed at reducing the risks associated with the formation of gas hydrates in pipelines. The numerical implementation of a mathematical model of natural gas flow in a horizontal channel is based on a sequential solution of a system of four differential equations by the Runge-Kutta method of 4 orders of accuracy, followed by a search for sequential approximations of the minimum inhibitor flow rate, in which the "gas + water ↔ gas hydrate phase" transition process does not occur on the inner surface of the channel. The article presents a calculation of the proportion of a hydrate formation inhibitor in the liquid phase by solving a cubic equation using the Cardano method. Based on the computational experiments results, graphs were constructed and interpreted of the dependencies of the minimum inhibitor consumption on the soil temperature, inlet gas pressure, total water concentration in the gas flow, initial gas temperature and total gas flow rate.

Improving heat transfer in indirect liquid-based battery thermal management systems through turbulator-equipped conical flow paths

To guarantee the safe operation of Li-Ion Cells (LICs) in various applications, such as electric vehicles, an efficient Battery Thermal Management System (BTMS) is necessary. The design of BTMSs, as documented in the literature, typically involves the use of cooling channels with uniform and smooth configurations. However, these configurations encounter the challenge of temperature non-uniformity in the battery module, which stems from elevated coolant temperatures along the flow direction. In this study, a 3D numerical analysis is conducted to develop a novel indirect liquid-based cooling system for the BTMS of a module with cylindrical LICs. The study explores the effects of conical cooling channels, both with and without twisted turbulators, across various coolant mass flows during a 2C discharge process of LICs. Within the studied ranges, diverging cooling channels improve the overall thermal and hydraulic performance of the BTMS by an average of 40%, increasing the heat transfer coefficient by a maximum of 32.6%, and decreasing pressure drop by up to 35.1%. The application of turbulators proves effective in reducing the maximum temperature difference within the LICs, demonstrating a decrease of approximately 34.2% at the minimum mass flow rate and 74.4% at the maximum mass flow rate. This emphasizes the more substantial impact of turbulator utilization at higher coolant mass flow rates. An increased coolant flow rate leads to a significant enhancement of the heat transfer coefficient, ranging from 70.5% to 79.0% for the BTMS incorporating turbulators. Moreover, the study highlights a more pronounced impact of increasing mass flow rates in the BTMS designed with converging cooling channels compared to those designed with diverging channels. Finally, the results of this analysis demonstrate that the proposed system is capable of efficiently regulating the temperature of the entire battery module, ensuring that it consistently maintains a normal and safe operational range suitable for vehicular applications (below 40 °C).

The effect of turbulence on the minimum thickness of a liquid film flowing down a vertical tube

When a liquid flows down a vertical tube at a low flowrate, it may not be able to completely cover the surface as a film, and the flow will comprise a number of rivulets separated by unwetted areas. Predictions of the minimum film thickness and corresponding minimum flowrate below which films cannot be sustained are needed in many industrial heat and mass transfer operations. In this paper a model is developed using the minimum energy method to calculate the minimum film thicknesses that can be maintained for flows down a vertical tube. It is concluded that inclusion of the effect of turbulence in the model can significantly increase the values of the calculated minimum film thicknesses. In these calculations (for 100⁰C water flowing down a 6 mm inside diameter tube) the effect of turbulence increased as the tube to liquid contact angle increased. For a flow at the highest contact angle of 90⁰, the minimum film thickness increased by 22% above the laminar value and the corresponding minimum flowrate increased by 75%. The model presented in this paper can be used to calculate the thermal performance of falling film evaporators over the whole range of flowrate.

Optimization of the first wall cooling circuits to achieve an efficient coolant flow distribution in the DCLL breeding blanket

In the current design proposal of the Dual Coolant Lithium Lead (DCLL) breeding blanket for the EU DEMO reactor, the first wall is cooled down by a succession of He channels arranged along the poloidal length. In this scheme, since He extracts around 30% of the blanket thermal power, a conservative oversizing of the coolant mass flow rate compelled by highly heterogeneous heat loads, can severely jeopardize the blanket thermal efficiency and the consumption of the auxiliary systems. A meticulous design of the hydraulic network can enhance the cooling system efficiency by ensuring that each channel is fed with a mass flow rate according to its specific needs.In this study, a novel approach employing genetic algorithms has been developed to optimize the geometry of the first wall, encompassing the feeding/collecting manifolds and channels. This optimization aims to replicate the mass flow rate distribution obtained from TOMFLOW (Tool for Optimization of Helium Mass Flow Rate Distribution), a code dedicated to determine the minimum mass flow rate required in each channel to maintain the EUROFER steel structure below 550 °C.

Numerical study on the effect of smoke emitted from the vents on the roof of a diesel train on the intake of downstream air-conditioning units

Constrained by economic development and geographical features, numerous railway lines remain unelectrified, underscoring the expansive potential of diesel trains. Diesel engine emissions discharged from the roof of trains pose a challenge as some of the smoke infiltrates the cabin through the intake of roof-mounted air-conditioning units (ACUs). This intrusion diminishes the indoor air quality, posing health risks to passengers and potentially jeopardizing their safety. This study employs the shear stress transport k-omega turbulence model to formulate a multiphase flow model for simulating smoke diffusion in diesel trains. Additionally, we conducted an optimization design to minimize smoke entry into the ACUs. This study defined six cases based on variations in the shape and height of the cover and the spacing of the smoke vents. The results show that the effect of the diffusion characteristics decreased with the cover height. With the progression of airflow diffusion, the effect of the smoke vent structure on the concentration diminished farther from the vents. The minimum smoke mass flow rate into the intake occurred with the vent spacing of 2.14 m and without a cover, resulting in a 57.0% decrease compared with the maximum. Thus, a smoke vent spacing of 2.14 m without a cover was deemed to be the optimal configuration. The research results provide certain engineering guidance significance for the design and operation of train-smoke vent structures.

Characterizing rheological behavior and fluidization of highly refined furnishes for process optimization

In this work, highly refined softwood bleached kraft pulp (SWBKP) furnishes, referred to here as XFC, were studied from the perspective of fiber suspension handling in processing. The rheology of the furnishes was studied with a rotational rheometer using a non-standard flow geometry to understand the viscosity development at different consistencies and the impact of temperature. For fluidization analysis during pipe flow, two optical methods were implemented; namely, optical coherence tomography (OCT) and high-speed video (HSV) imaging. The OCT was used to determine the small-scale floc structures near the pipe wall where the shear stress is highest, and the HSV imaging was applied for observing flow instabilities and XFC suspension uniformity at the pipe scale. All these issues can be significant in deciding the minimum flow rate required for a process pipe to get sufficient fluidization of XFC suspensions.

Modelling the piping-assisted erosion of clay barriers

Recent laboratory and field experiments have provided evidence of the erosion and piping of clay-based barriers. Predicting these phenomena is essential for the performance assessment of bentonite barriers and containments. This paper presents a non-local multi-physics model for bentonite erosion induced by piping flow that includes swelling, detachment of particles and co-transport of detached particles with piping flow. The erosion is controlled by the balance between the cohesive strength, which depends on the swelling, and the shear force, which depends on the water velocity and chemistry. The accuracy of the model is tested by comparison of simulation results with experimental data from pinhole tests and material erosion in boreholes. It is demonstrated that the model predicts accurately the total mass eroded by the piping flow. For example, the results show that the mass loss induced by piping-assisted erosion during the installation of a bentonite plug can reach 10·3% of the original mass, which may significantly reduce the sealing capacity of bentonite plugs in boreholes. The results of simulations show that the eroded mass depends on the borehole diameter and flow rate. The minimum flow rates required to erode 10% of the original mass are 0·8 l/s and 0·045 l/s for borehole diameter, db = 56 mm and 160 mm, respectively. These results demonstrate how the proposed formulations can be used to quantify the piping-assisted erosion of clay barriers, such as buffers, backfills and plugs considered for geological disposal of higher activity waste, and the sealing of investigation boreholes and abandoned geo-energy wells.

Analysis of hydraulic losses in the series from 1990 to 2022 at the Retiro small hydroelectric power plant

Hydraulic losses are a crucial variable in hydroelectric ventures as they can cause significant reductions in power generation. This article analyses the impact of hydraulic losses on the Retiro Small Hydroelectric Power Plant (SHPP), investigating their effect on monthly average power and, consequently, the efficiency of electricity generation. This study examines the historical series of load losses at the Retiro SHPP from 1990 to 2022. The calculations are based on flow data available in HidroWeb. The study considered the maximum and minimum flow rates in the historical flow series as constraints for hydropower generation. We used a multivariable function to calculate the efficiency of the hydraulic turbine, relating the turbine flow rate and the net water head. We developed mathematical relationships for head losses that occur in the grid, at the water intake, and due to friction from the intake to the turbine of the Retiro SHPP. The article presents a comparison between the actual monthly average power of the Small Hydroelectric Power Plant (SHPP) and the simulated monthly average power. We normalized the data for turbine flow and load loss to conduct statistical analysis. Kernel probability density was applied to understand the distribution shape of the data. Findings show that average monthly capacity is lowest in September, at approximately 0.81 MW. In March, the highest power occurs, approximately 14.19 MW. During the high flow period, the simulated average power, which accounts for load losses, closely matched the actual average power generated at the Retiro SHPP. In the months from July to October, despite being the period with the lowest head losses, it is the time when there is a greater opportunity to maximize energy generation at the power plant. An inefficient power generation system experiences significant load losses during specific periods of the year. To minimize this effect, it is crucial to understand the behavior of hydraulic losses and consider implementing mitigating measures.

Троспия хлорид у детей: динамика симптома остаточной мочи при коррекции расстройств мочеиспускания

Background. A significant place among pediatric urination disorders is occupied by overactive bladder (OAB). Treatment involving the use of M-anticholinergics is aimed to suppress detrusor overactivity. The side effects of treatment include urination problems, incomplete bladder emptying (residual urine), and acute urinary retention. Methods. We monitored 20 children aged 5–15 years, among them 12 boys and 8 girls. The average age (М±δ) was 8.47 ± 3.46 years. The 2-day uroflow monitoring revealed residual urine (RU) in 9 patients (1–15 times per monitoring period). The urination volume and rate, as well as RU, were assessed by uroflow monitoring conducted at home using the SIGMA F uroflowmeter (RZN registration certificate No. 2020/11522 of 5.08.2020). One of the components of combination therapy was trospium chloride (Spasmex) in a dose of 10–15 mg per day, depending on the age and disorder. Statistical data processing was performed using the STATISTICA 10 (StatSoft, Inc., USA) and Excel (Microsoft Office 2016) software packages. The differences were considered significant at p<0.05. The descriptive statistics were presented as М±δ (where М was median, δ was standard deviation). Results. The average effective volume (AEV) of urination in the group was reduced by 10–86.5% relative to the age norm. Furthermore, incomplete bladder emptying was reported in 9 patients. After treatment, the minimum urine output volume and the maximum urine flow rate increased significantly, while the urination rate decreased. There were no significant changes in the urine output volume (average and maximum), however, an upward trend of the urine output volume was observed. No increase in the number of RU cases following prescription of trospium chloride was reported. In fact, the decrease in their number was recorded. Conclusion. Pediatric micturition cycle abnormalities also include the RU symptom. The M-anticholinergic drug, trospium chloride (Spasmex), in a daily dose of 10-15 mg represents a safe and effective medication option. Therapy lasting up to 2 months results in the significant increase in minimum bladder volume and maximum urine flow rate, the decrease in pollakiuria severity, but never changes the rate and amount of residual urine.

Energy, exergy and environmental analysis of concentrated parabolic trough collector using alumina-water nanofluid and twisted tape insert

Concentrating parabolic trough collector (CPTC) is used to convert energy of solar radiation into useful heat energy utilized in different thermal applications. The present article discusses the use of nanofluids and inserts in CPTC to improve its performance parameters such as collector efficiency, exergy efficiency, Nusselt number, friction factor, and performance augmentation factor (PAF). Al2O3-water nanofluid with different volume concentrations of 0.25%, 0.5%, 0.75%, and 1% was used as working fluid. The effect of simple twisted-tape insert (STI) and overlapped twisted-tape insert (OTI) were studied with the nanofluid to evaluate performance of CPTC. Nanofluid, with highest volume fraction (φ = 1%), demonstrated maximum enhancement as 5.3%, 17.4%, 70%, 230%, and 140% in collector efficiency, exergy efficiency, Nusselt number, friction factor, and PAF as compared to water as working fluid flowing through plain absorber tube. Employing STI and OTI with nanofluid (φ = 1%) represented maximum enhancement of 14.5% and 15.9% in collector efficiency, 19.9% and 20.8% in exergy efficiency, 282% and 367% in Nusselt number, 1800% and 1900% in friction factor, and 231% and 475% in PAF as compared to water flowing through bare absorber tube at a minimum flow rate. OTI with nanofluid (φ = 1%) demonstrated maximum CO2 reduction of 1.61 tons/year and maximum enviro-economical gain of 23.41 $/year.

Radioprotection issues in uraniferous minerals collections with reference to an actual case.

Our work investigated the radioprotection implications associated with the possession of a collection of uraniferous minerals. Considering different scenarios, we developed (and applied to an actual collection) specific formulas for radiation doses evaluation. We discussed the shielding necessary to reduce the gamma irradiation down to the required values. A mathematical model was developed to estimate the minimum air flow rate to reduce the radon air concentration below the reference values. The radiation risks associated to the handling of single specimens was also addressed, including hand skin irradiation and shielding capabilities of surgical lead gloves. Finally, we discussed the radiation risks associated to the exhibition of a single specimen. The results, compared to the safety standards of the EU Directive 13/59, show that the exhibition of uraniferous samples with activity of a few MBq do not need specific radioprotection requirements nor for the involved personnel nor for visitors.