Low Flux Research Articles

A 25-micrometer Single-Photon-Sensitive Kinetic Inductance Detector

We report measurements characterizing the performance of a kinetic inductance detector array designed for a wavelength of 25 microns and very low optical background level suitable for applications such as a far-infrared instrument on a cryogenically cooled space telescope. In a pulse-counting mode of operation at low optical flux, the detectors can resolve individual 25-micron photons. In an integrating mode, the detectors remain photon noise limited over more than 6 orders of magnitude in absorbed power from 70 zW to 200 fW, with a limiting noise equivalent power of 4.6×10−20 W Hz−1 at 1 Hz. In addition, the detectors are highly stable with flat power spectra under optical load down to 1 mHz. Operational parameters of the detector are determined including the efficiency of conversion of the incident optical power into quasiparticles in the aluminum absorbing element and the quasiparticle self-recombination constant. Published by the American Physical Society 2024

Experimental investigation of pressure drop oscillation and active mitigation in a pumped two-phase loop

A pumped two-phase loop (P2PL) integrated with a microchannel evaporator is the most favored design for advanced thermal management of modern electronic devices. However, these systems are susceptible to two-phase flow instabilities, in particular pressure drop oscillation (PDO), which can compromise their performance by premature initiation of critical heat flux (CHF), deterioration of the heat transfer capabilities, and inducing severe thermal and pressure fluctuations. This study experimentally investigates PDO in a P2PL with a microchannel evaporator, exploring the underlying mechanisms and mitigation strategies. The range of parameters are: heat flux from 0 to 56 W/cm2, mass flux from 47.9 to 95.9 kg/m2-s, a fixed inlet temperature of 10 °C, initial accumulator gas pressure from 620.5 to 827.3 kPa, and vapor quality from zero (subcooled liquid) to one (pure vapor close to dryout). A consistent trend of high-amplitude, low-frequency PDO at low heat fluxes transitioning to low-amplitude, high-frequency PDO at high heat fluxes was observed across all operating conditions. PDO originating in the evaporator propagated to other loop components with similar characteristics, underscoring the systemic nature of PDO. Further, PDO-driven thermal oscillations were observed to propagate through the evaporator, reaching the heater (heat source) temperature with maximum amplitude of 3.4 °C. These oscillations had a detrimental impact on the heat transfer coefficient by altering the flow boiling regimes within the microchannels. Notably, the subcooled liquid temperatures remained stable, indicating the absence of pressure-induced thermal effects in single-phase regions. Finally, an active control technique, based on controlling the pump flow rate using continuous feedback of flow rate was implemented to mitigate PDO, eliminating both pressure and temperature oscillations, achieving an average reduction of 69.8 % in PDO amplitude.

Comparison between Low Flux and High Flux Hemodialysis in Rebound of the Metabolic Profile and in Post-Dialysis Recovery Time in Prevalent Hemodialysis Patients

Abstract Background It is known that the high flux membranes now are widely used all over the world due to the higher permeability of the high flux membranes compared to low flux ones to middle molecules, remove more serum endotoxins and improve the patient general condition and quality of life. This study aims at exploring the effect of using High flux membrane in rebound metabolic profile in the prevalent hemodialysis patients and also its effect on post dialysis recovery time Methods This descriptive analytic study included the available data in hemodialysis patients in Port- Said Al Eman Hemodialysis Unit. Data was collected between March and September 2022. This clinical trial, 100 patients who met the inclusion criteria were randomly assigned to have their regular hemodialysis sessions with low flux dialysis membranes and examined for rebound metabolic laboratory investigations (4 hours post dialysis) and post dialysis recovery time questionnaire DRT, then compare the same previois parameters while using high flux dialysis membranes and consider which of both dialysers is better to use for the hemodialysis patients Results Of the 100 patients in the sample the Mean 4 hours post dialysis urea in low flux was 106.65 ± 3.1 and in high flux was 76.67 ± 3.1. Mean 4 hours post dialysis phosphorus in low flux was 6.17 ± 0.14 and in high flux was 4.45 ± 0.14. Mean 4 hours post dialysis CRP in low flux was 7.88 ± 0.72 and in high flux which was 3.84 ± 0.72. Mean 4 hours post dialysis Calcium in low flux was 9.17 ± 0.09 and in high flux which was 9.77 ± 0.09. Mean 4 hours post dialysis Potassium in low flux was 5.3 ± 0.08 and in high flux which was 4.7 ± 0.08. Mean 4 hours post dialysis Magnesium in low flux was 2.24 ± 0.03 and in high flux which was 2.33 ± 0.03. Mean 4 hours post dialysis Bicarbonate in low flux was 21.96 ± 0.27 and in high flux which was 24.23 ± 0.27. Significant strong correlation between The fewer CRP Rebound 4 hours post and the shorter the post dialysis recovery time in high flux membrane p = 0.003. Significant strong correlation between The fewer Ultrafiltration volume removal and the shorter the post dialysis recovery time in both dialysers p < 0.001. Significant strong correlation between The lower decrease in serum Bicarbonate level and post dialysis 4 hours and post dialysis recovery time in high flux membranes p < 0.001. Conclusion The fewer CRP rebound and higher Bicarbonate serum concentration 4 hours post dialysis and the shorter the post dialysis recovery time.

Membrane fouling in integrated forward osmosis and membrane distillation systems – A review

With the increase in water consumption, especially by the industrial and agricultural sectors, more strategies capable of increasing the recovery and reuse of water resources have been sought. An example of technology that assists in this challenge is membrane separation processes. However, systems that use this type of separation may be limited by the phenomenon of fouling. Integrated systems such as forward osmosis (FO) with membrane distillation (MD) have several advantages, such as obtaining a high-quality permeate from raw wastewater, the constant regeneration of the draw solution, which assists in continuous operation, and the possibility of association with biological tanks that enable nutrients recovery. However, these systems face limitations related to low flux values caused by membrane fouling. Therefore, the present review seeks to study fouling in integrated FO-MD systems to understand the main challenges of applying this technology and achieving higher permeate flux values. From the most recent studies, many strategies are being evaluated, such as different membrane materials, deposition of antifouling materials on membrane surface, feed temperature, draw solution substances, concentration and temperature, use of spacers and new modules configurations. That way, the low flux from those systems may be bypassed, enabling FO-MD systems scale up.

A Nondestructive and Rapid Method for the Determination of Triamterene Content by Transmission Raman Spectroscopy Combined with Chemometrics

Background: Triamterene is a potassium-conserving diuretic mainly used in the treatment of edematous diseases. Although there are some methods to measure the content of triamterene, the existing methods have the characteristics of sample destructiveness and low flux, making it difficult to meet the needs of online monitoring. In recent years, transmission Raman spectroscopy (TRS), as a new technology for the determination of drug content, has emerged as being nondestructive and rapid and provides a new method for the determination of triamterene content. Objective: In this study, we used transmission Raman spectroscopy combined with partial least squares (PLS) approaches to establish a six concentration levels model for measuring the content of triamterene. The model was applied to determine whether tablets are commercially available. Method: Firstly, TRS was used to collect the spectra of the principal components and mixed excipients of triamterene, and the feasibility test was carried out. Secondly, six concentration levels were determined by the design of experimental (DOE), and hand-made tablets were prepared to obtain corresponding spectra. The content prediction model was established by the PLS method, and the content of triamterene was determined by high-performance liquid chromatography (HPLC) to correct the model. Finally, the model was applied to the determination of triamterene in commercially available tablets. Results: The results showed that the established model was successfully applied to the determination of triamterene. The values of RMSEC (0.0089783) and RMSECV (0.0097241) of the final model were very low and close to each other. The relative error of 12 hand-made tablets predicted by this model was less than 5% compared with the results determined by HPLC. In addition, in the process of applying the model to the determination of the content of commercially available tablets, the accuracy of the model can be significantly improved by adding the spectrum of commercially available tablets. The corrected model was used to determine the content of triamterene in two commercially available tablets. The results showed that the relative error was less than 5%. Conclusion: We described a new strategy to analyze the content of active pharmaceutical ingredients (API) in triamterene tablets by TRS with PLS. The established model has the advantage of non-destructive and rapid quantitation, which can provide a new method for real-time monitoring of production lines and promote the development of process analytical technology (PAT).

Surface exchange of HONO over paddy fields in the Pearl River Delta, China

Soil can release HONO, affecting atmospheric oxidation and tropospheric chemistry processes through the production of hydroxyl radicals (OH) and nitric oxide (NO) via photolysis. However, there is limited field observation of HONO flux, hindering a comprehensive understanding of its emission mechanisms. In this study, a dual open-top chambers system combined with a long path absorption photometer (LOPAP) was employed to measure HONO flux from paddy fields in the Pearl River Delta area (PRD), showing good reproducibility and effectivity to mitigate greenhouse effects. The average HONO flux was 0.77 ± 0.72 ng N m−2 s−1, displaying a diurnal pattern of higher fluxes during the day and lower fluxes at night, similar to previous flux observations. A strong linear correlation between the HONO flux with the product of NO2 and solar radiation (R2 = 0.90) suggests that surface reactions involving NO2 and sunlight may dominate HONO production from the paddy fields, surpassing microbial activity within the soil. Given the diversity of field environments, more field observations are needed for assessing emission rates of HONO and understanding underlying mechanisms.

Experimental investigation of the swirling steam jet condensation at low mass flux

Swirling steam jet condensation holds significant applications in industrial processes such as nuclear safety and gas–liquid mixing in the oxygen transmission pipeline of the liquid rocket engine. However, due to its involvement with complex flow and phase-change heat transfer, the application and optimization of related condensation technologies still face challenges. Therefore, this paper aims to investigate the condensation characteristics of the swirling steam jet by numerous experiments. The steam mass flux is 15–45 kg/(m2·s), and the water temperature ranges from 40 to 85 °C. A novel X-type swirl pressure nozzle is selected to achieve the swirling flow of the steam jet. A comparative analysis is conducted on the interface behavior and evolution of condensation parameters of the non-swirling and swirling steam jets during condensation processes. Results show that the swirling jet condensation includes three flow patterns, namely, chugging regime, smooth grown bubble regime, and rough grown bubble regime. Compared with the non-swirling steam jet condensation, swirling steam jets exhibit a 10.36% increase in the smooth grown bubble regime region and a 14.63% decrease in the rough grown bubble regime. Swirling bubble morphology evolves steadily, and the surface is smoother and more rounded. Simultaneously, irregular deformation behaviors can also occur in the swirling bubble condensation process, such as spiral growth of jet bulge, neck torsion, and the corolla pattern. This deformation helps to increase the contact area and prolongs the bubble lifetime, allowing for more adequate heat transfer at the steam–water interface. The swirling motion of the steam jet will reduce the bubble collapse frequency. As the water temperature rises from 60 to 80 °C, the bubble condensation rate and collapse frequency decrease. The bubble radius increases and the condensation time is extended. With the increasing steam mass flux, the collapse frequency gradually increases. The condensation rate and the bubble radius vary nonlinearly. At the higher steam mass flux, the swirling motion can effectively release the heat that accumulates inside the bubble after reaching the condensation equilibrium state.

Measurements of Low Optical Power with Cryostat-Based Predictable Quantum Efficient Detector at Liquid Nitrogen Temperature

Abstract We have validated optical power measurements with a Predictable Quantum Efficient Detector (PQED) at liquid nitrogen temperature (77 K) at low optical power from 130 fW to 3.3 pW. Two laser wavelengths at 514 nm and 785 nm were used. The lowest measured optical power corresponds to a photon flux of 0.5·106 photons per second (785 nm). The PQED’s responsivity is linear within the relative measurement uncertainties of 8% at 0.5·106 ph/s and 1.4% at 10·106 ph/s (95% confidence level), which enables the calibration of other low photon flux detectors directly against a primary standard of optical power.

Proton Predominance At UHE Cosmic Rays Through Analysis Of Different Mass Composition Models

Recently, detection of giant (1017 to 1020eV ) and super giant ( Ep >1020 eV ) air showers is gaining importance as the investigation of EAS in these energy ranges is expected to give necessary information on characteristics of high energy nuclear interactions in one hand and for solving the astrophysical problem of Cosmic Ray origin , beyond the Greisen-Zatsepin-Kuzmin cut-off energy near 1020 eV. Due to the very low Cosmic Ray flux in the UHE range ( > 1017 eV ) direct measurement by balloons or satellites are not possible. The experimental approach realized conventionally uses extended ground-based installations catching data of the induced air showers . An alternative approach is to use a low cost particle detector array called mini-array for detecting UHE cosmic rays by Linsley’s method of arrival time measurement. The miniarray consist of eight plastic scintillation counters covering an area of 2m2 operating for detecting EAS particles of primary energy 1017 -1018 eV based on Linsley’s method of arrival time measurement. An optical detector (5 inch diameter PMT) has been installed at the centre of the miniarray to record the associated optical Cerenkov pulse produced by the ultra-relativistic shower particles in the atmosphere with an aim to derive primary mass composition above 1017 eV. Optical pulses are recorded in one channel of the DSO and the stored data in the wave form memory are transferred to the computer via GPIB interface. The particle detector pulses are triggered with the help of trigger circuit and recorded through other channel of the DSO and transferred to the same DSO. However, the data are subjected to large fluctuation both in particle detection and optical photon detection. Primary energy is estimated through the parameter shower size which is also indirectly measured from a small sample of shower front using miniarray data. Mass composition estimated indirectly relies on simulation model. On the basis of pulse height distribution measurement, the inferred mass composition is predominantly protons, with a tendency of mass composition becoming lighter at the highest energies.

Assessment of Neutrophil Activation in Children with Chronic Kidney Disease Stage 5 on Hemodialysis: Effect of a Single Procedure

Abstract Background Hemodialysis (HD) process can trigger inflammation and induce cytokines activation. Neutrophils extrude neutrophil extracellular traps (NETs) which are extracellular chromatin containing a variety of granular proteins that have been implicated in infection, as well as vascular inflammation and occlusion. Objective To assess the effect of a single HD session on the level of circulating NETs in children with chronic kidney disease stage 5 (CKD-5) on regular HD treatment. Methods This is a cross sectional study done at Pediatric Dialysis Unit (PDU), Children’s Hospital, Ain Shams University during the period from April 2023 to July 2023. It included 26 CKD-5 cases receiving 3 hours HD session 3 times per week using low flux polysulfone dialyzer and 26 age and sex matched children as controls. Patients with the following medical conditions were excluded: failed renal graft, active infection, autoimmune disease, active thrombosis, diabetes mellitus, malignancy, cardiovascular disease like (infective endocarditis, vegetation and intracardiac mass) and patients on immunosuppressants. Complete blood cell (CBC), C-reactive protein (CRP) and serum NETs measured by enzyme-linked immunosorbent assay were done for all cases pre- and post-dialysis as well as the control group. Results The mean±SD age of the patient was 12.2±2.8 years. They were 16 males (61.5%) and 10 females (38.5%). The mean age of the controls was 10.9±2.7 years. They were 13 males (50%) and 13 females (50%). There was significantly elevated pre-HD (Median= 535.95ng/L, IQR= 519.6ng/L) and post-HD (Median=1310.5ng/L, IQR=916.4ng/L) serum NETs compared to its level (Median=149.1ng/L, IQR=69.7ng/L) in controls (p < 0.001 for both). There was also significantly higher post-HD level of serum NETs than its pre-HD one (p < 0.001). Gender did not have significant effect on serum NETs levels (p = 0.089). The age of patients, dialyzer surface area, pump blood flow rate, and duration of HD didnot correlate significantly with serum NETS levels (p = 0.95, 0.68, 0.23 and 0.83, respectively). In addition, there was no significant correlation between serum NETs and total leukocyte count, absolute neutrophil count and lymphocyte count (p = 0.29, 0.17 and 0.6, respectively). Conclusion Children with CKD-5 on regular HD had higher basal levels of circulating NETs than normal controls. These levels were further increased after HD session using low flux polysulfone membrane implying the associated subclinical inflammation.

Design of Flow Fields for High-Temperature PEM Fuel Cells Using Computational Fluid Dynamics

This study proposes novel and modified conventional flow fields for a high-temperature PEM fuel cell, and predicts the fluid dynamic behavior with a 3D, computational fluid dynamics model. Five base flow field patterns (FFPs) are selected: a 4-channel serpentine, a hybrid design, a 2-channel spiral, a dual-triangle sandwich, and a parallel pin-type flow field. For each base FFP, sub-patterns are developed through modification of the channels and ribs. The 4-channel serpentine is taken as the state-of-the-art reference flow field. Simulations are carried out at two different mass flow rates. The result shows that the incorporation of a dead end in flow channels or the merging of channels into a single channel before connecting to the outlet enhances the average and maximum GDL mass flux, but it also increases the pressure drop. The parallel pin-type design-3 and dual-triangle sandwich design-1 exhibit a more even distribution but yield a lower average GDL mass flux than the 4-channel serpentine, which could be beneficial for reducing MEA degradation and thus used at low load conditions where a high mass flux is not needed. In contrast, the uniform hybrid design and 2-channel spiral design-2 provide a higher average and maximum mass flux with a more non-uniform distribution and greater pressure drop. The high average GDL mass flux would be beneficial during high load conditions to ensure enough reactants reach the catalyst.

조선용 B Gr. 강의 용접부 미세조직과 기계적 성질에 미치는 용접기법의 영향

The microstructurale and mechanical properties of B Gr. steel were evaluated for shipbuilding according to a welding process. The following conclusions were drawn. In tandem submerged arc welding(TSAW), compared to single submerged arc welding(SAW), the grain boundary ferrite was coarsened, and the fraction was higher owing to the high heat input and low flux basicity ; conversely, the volume fraction of acicular ferrite was lower. Fine intragranular acicular ferrite and polygonal ferrite were observed in the weld metal of the electrogas welding (EGW), which had the highest heat input. In the microstructure near the fusion line, as the amount of heat input increased, the prior austenite grain boundary became coarse. Further, both the intergranular grainboundaryferrite and intragranular bainite became coarse, and the heat-affected zone became wider. The hardness of weld metal was independent of the amount of heat input and was demonstrated to be high in the order of EGW, single SAW, and TSAW owing to the microstructure difference caused by the chemical composition of the filler material and the dilution rate of the base metal. Furthermore, the tensile strength of all three welding processes resulted in stable satisfaction with the class society rules.

Experimental investigation on the heat transfer characteristics of loop thermosyphon with a micro-channel evaporator under low heat flux

Loop thermosyphon is an efficient heat transfer device increasingly used in solar energy applications. The heat flux offered by solar radition is relatively restricted, but the mechanism of heat and mass transfer in loop thermosyphon at low heat flux remains ambiguous. Hence, a low heat flux loop thermosyphon experimental test platform was proposed and constructed in this paper to investigate the influences of filling ratio, heat load and cooling water temperature on the start-up and operation characteristics of the system. The outcomes reveal that instances of local dry-out, temperature overshoot, and geyser boiling are witnessed throughout the experimental process. With an increase in the filling ratio, the occurrences of local dry-out and geyser boiling gradually decrease and disappear, while the temperature overshoot becomes more prominent. The system’s optimal filling ratio is found to be approximately 80 %, and the lowest thermal resistance is 0.0053 K/W. No heat leakage is observed from the bottom of the evaporator to the liquid line. Except for the 40 % filling ratio, the system’s heat transfer efficiency exceeds 94 % for all other filling ratios, and the heat transfer performance is outstanding. The research results will contribute to the enhanced application of loop thermosyphon in solar energy utilization, possessing practical engineering significance. Additionally, they can also enhance the heat and mass transfer mechanisms of loop thermosyphon, having certain academic significance.

Mechanism analysis of turbulent convective heat transfer of supercritical carbon dioxide in serpentine tubes

This study examines turbulent convective heat transfer in serpentine tubes, a critical topic given their widespread use in supercritical carbon dioxide (SCO2) cycle heat exchangers. Despite their importance, this area remains underexplored. The novelty of this work lies in analyzing various serpentine tube orientations to optimize heat exchanger design under different mass and heat fluxes. Using a validated numerical method, the study explores the impact of SCO2 thermophysical variations on gravitational and centrifugal forces. Furthermore, heat transfer effects are evaluated by analyzing Morton and Dean vortices as well as Richardson numbers under various conditions. The results show that changes in mass and heat fluxes have a greater impact on the gravitational Richardson number than on the centrifugal Richardson number. When both effects are considered together, the Richardson ratio increases with higher mass and heat fluxes, emphasizing the dominance of centrifugal force over gravitational force. The study also found that changes in SCO2 flow direction most significantly affect the thermal and hydraulic characteristics of serpentine tube in a vertical orientation. The improvement index reaches values of 1.13, 2.38, and 3.26 at heat fluxes of 20, 40, and 60 kW/m2, respectively. However, under conditions of low mass fluxes and high heat fluxes, the serpentine tube with a lateral orientation and downward SCO2 flow demonstrates optimal overall performance. In this configuration, the performance index for thisconfiguration increases by up to 15 % at a heat flux of 60 kW/m2.

Mio-pliocene evolution of deep-water channels on the northeastern Bengal fan: Records of signals of Himalaya uplift and South Asian Monsoon from source areas

Submarine channels, acting as major conduits for delivering terrestrial sediments into the deep sea, are sensitive to source-region uplift and climate variations. Using new 3D seismic data, previously published paleoenvironmental data, and IODP/ODP data, we characterize stratigraphic time changes in deep-water channels on the northeastern Bengal Fan and suggest that their long-term evolution relates to contemporaneous changes of Himalaya uplift and South Asian Monsoon. Our results show that around the boundary between the Miocene and Pliocene Epochs, the sedimentary characteristics of deep-water channels were changing at about the same time as decreased rates of Himalaya uplift and changes in the monsoonal climate. It is strongly suggested that environmental signals could successfully propagate from the Himalaya to the deep sea and play a dominant control on the long-term evolution of deep-water channels. During the late Miocene, orogen-wide and substantial Himalaya uplift and humid monsoonal climates (dominance of summer monsoon) generated a sediment supply with high fluxes, which allowed coarser-grained sediments to reach further into the basin and thus caused the formation of larger-scale, non-leveed erosional channels that have avulsion and confluence phenomena. After the Miocene, local and limited Himalaya uplift and arid monsoonal climates (dominance of winter monsoon) led to a sediment supply with low fluxes, during which only finer-grained sediments reached deep water and gave rise to smaller-scale, leveed aggradational channels that mainly have splay deposits. Between the late-Miocene and post-Miocene periods, detrital zircon U-Pb ages of Bengal Fan samples from IODP cores reflect a sediment provenance change from the mixing of Brahmaputra and Ganges Rivers to the end-member of Brahmaputra River, broadly coeval with the variations of Himalaya uplift and South Asian Monsoon. Moreover, Bengal Fan cores record a Mio-Pliocene decrease in sedimentation rates and maximum grain sizes and an increase in mudstone contents, consistent with the variations of sediment yield in the source catchments. Observations and interpretations from the current study, therefore, contribute to a better understanding of how the long-term evolution of submarine channels respond to tectonic and climatic perturbations in source areas and may help recognizing similar process-response relationships in other areas.

A Study on Enhancing Axial Flux Motor Efficiency Using Cladding Core Technology

With the rise of eco-friendly policies, advanced motor technologies are being developed to replace fossil fuel-based engines in the mobility industry. Axial flux motors, known for their ability to reduce size and increase output torque compared to radial flux motors, require different materials and manufacturing techniques. Specifically, the production of complex stator cores and segmented magnets presents significant challenges, often leading to higher costs. To address this issue, soft magnetic composite (SMC) materials, which offer greater design flexibility, are being explored for use in stator cores. However, soft magnetic composite materials exhibit lower permeability and saturation flux density compared to laminated silicon steel, resulting in reduced output torque and efficiency. This paper investigates the effects of stator geometry on axial flux motor performance and explores cladding core technology, which combines soft magnetic composite materials with silicon steel. By conducting finite element method (FEM) analysis to evaluate the output torque and efficiency based on the shape of the silicon steel within the cladding core, this study proposes an optimized cladding core design to enhance the efficiency and output torque of axial flux motors.

The production and separation of 161Tb with high specific activity at the University of Utah

Targeted radiotherapy (TRT) is an increasingly prominent area of research in nuclear medicine, particularly in the context of treating cancerous tumors. One radionuclide of considerable interest for TRT is terbium-161 (t1/2 = 6.95 days), which undergoes beta emission and shares similar decay properties as 177Lu (FDA-approved as LUTATHERA® and PLUVICTO®). Besides beta emission, 161Tb also emits a significant number of conversion and Auger electrons further enhancing its therapeutic potential. Terbium-161 can be produced using nuclear reactors through an indirect neutron capture reaction, G64160dn,γG64161d→3.66min,β−T65161b, from 160Gd targets. However, a key challenge in utilizing 161Tb for TRT lies in effectively separating target and product materials to attain high specific activity for radiolabeling. Here, we detail the production of no-carrier added 161Tb using low flux research reactors (mean thermal (<0.625 eV) neutron flux: 1.356×1012n∙cm−2∙s−1) like the University of Utah TRIGA Reactor, using enriched 160Gd2O3 targets (1.5 ± 0.3 μCi of 161Tb per mg of 160Gd target per hour of irradiation). We also developed a separation technique based on cation exchange and extraction chromatography, suitable for mCi level irradiations with targets exceeding 200 mg. In a simulated full-scale irradiation, 161Tb was successfully isolated from large mass targets using cation exchange (AG 50W-X8, with 2-hydroxyisobutyric acid at 70 mM, pH 4.75) and extraction chromatography (LN Resin, 0.5–0.75 M HNO3) methods. This resulted in high apparent molar activities of [161Tb]Tb-DOTA (113 ± 3 MBq/nmol), demonstrating high purity 161Tb relevant for potential future preclinical applications.

Flow boiling in a rectangular micro/mini channel with self-rewetting and non-rewetting fluids

In this experimental investigation the influence of self-rewetting during flow boiling was studied in a horizontal microchannel during one-sided uniform heating. The channel had a width and height of 6 mm and 0.3 mm respectively. Local wall temperature and direct in-time flow visualisation was performed. The working fluids under consideration included water as base reference, pure 1-butanol, pure ethanol, dilute butanol-water self-rewetting mixtures, and a dilute ethanol-water binary mixture. Tests were conducted at mass fluxes of 10, 15 and 25 kg/m2s, over a range of heat fluxes to produce both single phase and two-phase quasi steady state flow data. Within the wall temperature ranges of interest, the butanol-water mixtures (5 % and 7 % by volume butanol) had surface tension characteristics that would draw liquid toward local wall hotspots. Local and average wall temperatures and heat transfer coefficients were obtained and considered against the governing flow pattern visualisations. In contrast to the other fluids, the self-rewetting butanol-water mixtures exhibited significantly more stable flow and more predictable saturation flow boiling heat transfer coefficient trends across all heat fluxes under consideration. At the lowest mass flux, it was found that an increase in the heat flux resulted in an improvement in the self-rewetting fluids heat transfer performance, while at higher mass fluxes this dependence was diminished. Across all mass fluxes and heat fluxes the 5 % butanol-water outperformed its 7 % butanol-water counterpart. The tendency of self-rewetting to reduce local dry-out, even at low mass fluxes are demonstrated.

Coupled Wall Boiling and Population Balance Model for High Void Fraction Flows Under Sub-Cooled Nucleate Boiling Regime: Model Development and Validation

Abstract The subcooled flow boiling of water in a vertical annulus channel is studied numerically at low-pressure conditions. The two-fluid model is developed with flow-regime dependent interfacial transfers for mass, momentum, and energy using the algebraic interfacial area density (AIAD) framework. A discrete population balance model is used to mechanistically determine the vapor bubble diameter in the flow channel by considering the bubble aggregation and breakup effects. Energy balance at the heated wall for the subcooled nucleate boiling is handled using a suitable wall boiling model. A coupling is achieved between the discrete population balance and the wall boiling model for the nucleation and the growth rate of the vapor bubbles along the heated wall. The developed model simulates the reference experimental cases of flow boiling in a vertical channel for various flow and thermal conditions. At low wall heat flux, the wall boiling generates vapor bubbles near the heated wall and within the bubbly flow regime. With an increase in the wall heat flux, the aggregation and evaporation cause the formation of larger bubbles, which progress toward the flow channel core region, a phase that is representative of the transitional flow regime. The model's capability to predict such flow regime transition is validated with the experimental results. The bubble aggregation is found to be dominant compared to the breakup, and thus, proper choice of the aggregation factor is important for the accurate prediction of vapor parameters for the subcooled flow boiling at low-pressure conditions.

Mechanistic impact of Stern bilayer-based electrolysis on the enhancement of pool boiling heat transfer

Pool boiling is a heat transfer method that utilizes phase change for efficient heat transfer, and enhancing its heat transfer intensity and understanding the mechanism is of great practical significance for refrigeration and microelectronics thermal management. This study employs experimental methods to innovatively use ionic surfactant modification on heating surfaces, building on the basis of strengthening heat transfer by generating hydrogen bubbles through water electrolysis to increase nucleation sites on the heating surface. The Stern double layer formed on the heating surface is utilized to control the growth rate and quantity of hydrogen bubbles, thus achieving controllable nucleation density on the heating surface. The study examines its impact on heat transfer efficiency and the onset of nucleate boiling (ONB). Results indicate that electrolysis can increase nucleation sites at low heat fluxes, thereby enhancing heat transfer. Using a CTAB solution at a concentration of 3200 ppm with an electrolytic current of 0.08A, under the Stern potential at saturated adsorption, the heat transfer coefficient increased by up to 3.16 times. Additionally, the superheat at ONB decreased from 12.6 K to 4.4 K under boiling heat flux. Therefore, utilizing electrolysis with the addition of surfactants to enhance rapid cooling of high-temperature surfaces provides a novel engineering application approach.