Recirculation Loop Research Articles

K+ontrol rapidly and efficiently reduces potassium in donor blood during ex vivo circulation.

Patients with kidney failure are at risk for lethal complications from hyperkalemia. Resuscitation, medications, and hemodialysis are used to mitigate increased potassium (K+) levels in circulating blood; however, these approaches may not always be readily available or effective, especially in a resource limited environment. We tested a sorbent cartridge (KC, K+ontrol CytoSorbents Medical Inc., Monmouth Junction, New Jersey) which contains a resin adsorber for K+. The objective of this study was to test the utility of KC in an ex vivo circulation system. We hypothesized that KC reduces K+ levels in extracorporeal circulation of donor swine whole blood infused with KCl. A six-hour circulation study was carried out using KC, a NxStage (NxStage Medical, Inc., Lawrence, MA) membrane, blood bag containing heparinized whole blood with KCl infusion, 3/16-inch ID tubing, a peristaltic pump, and flow sensors. The NxStage permeate line was connected back to the main circuit in the Control group (n = 6), creating a recirculation loop. For KC group (n = 6), KC was added to the recirculation loop, and a continuous infusion of KCl at 10mEq/hour was administered for two hours. Blood samples were acquired at baseline and every hour for 6h. In the control group, K+ levels remained at ∼9mmol/L; 9.1 ± 0.4mmol/L at 6h. In the KC group, significant decreases in K+ at hour 1 (4.3 ± 0.3mmol/L) and were sustained for the experiment duration equilibrating at 4.6 ± 0.4mmol/L after 6h (p = 0.042). Main loop blood flow was maintained under 400mL/min; recirculation loop flow varied between 60 and 70mL/min in the control group and 45-55mL/min in the KC group. Decreases in recirculation loop flow in KC group required 7% increase of pump RPM. During ex-vivo extracorporeal circulation using donor swine blood, KC removed approximately 50% of K+, normalizing circulating levels.

Optimizing E. coli cell growth performance with in-line, real-time OD600 (abs/mm) monitoring during the fermentation process

The increasing demand for cell and gene therapies (CGT) has created a need to optimize manufacturing process steps using Process Analytical Technologies (PAT) to lower costs and increase yields. Plasmid DNA (pDNA) is a precursor to the development of CGTs and is met with many challenges throughout the production process due its size, viscosity, and similarities to other impurities. The generation of these plasmids in high density E. coli cultures can be difficult to monitor using traditional off-line OD600 methods due to the careful sample preparation, fast growth rate, and dilutions required to be in the linear range of a standard spectrophotometer. This study proposes utilizing an in-line, variable pathlength spectrophotometer in a recirculation loop during fermentation to monitor and optimize the growth of E. coli cells in real-time. This provides distinct advantages over traditional methods due to the constant modification of path lengths to create a slope-based solution that is always within the linear range of the equipment, with no buffer correction required. The growth curve is tracked in real-time using the slope (Abs/mm) at 600 nm to measure cell density and to optimize growth performance of cells. This will serve as a proof-of-concept for the optimal cultivation of E. coli and production of pDNA. The Biofactory Competence Center (BCC) is a not-for-profit organization based in Switzerland with the aim of providing training courses to the biopharmaceutical industry and related sectors, in order to supply a highly trained workforce. The BCC also provides technical services, including process design, development, and optimization.

A novel approach to predict the inclusion removal in a billet caster mold with the use of electromagnetic stirrer

Use of in-mold electromagnetic stirrer (M-EMS) in continuous casting (CC) mold has been an effective means to get clean steel. However, at times their application results in slag entrainment and inclusion particles from the meniscus due to improper positioning of the stirrer along the length of the mold. More importantly, the inclusion particles coming through the tundish outlet pose a great challenge as they are likely to get trapped in the swirl flow developed due to the stirrer and finally move towards the mold outlet. In this study, a multiphase model involving solidification, slag-metal interface and inclusion transport is developed in the billet continuous casting process. The multiphase study involves the study of slag metal interface as well as the inclusion transport in the billet caster mold. For inclusion removal at the interface, a new realistic approach based on volume fraction criterion is adopted and incorporated using user defined function. The numerical results reveal that both intensity and size of the recirculation loop decrease on shifting the EMS away from meniscus. Tangential velocity increases significantly in the presence of EMS. Stirring generated due to EMS decreases the temperature and increases the uniformity in liquid fraction in the region above the stir. This region becomes wider as EMS moves downwards. Stirring pulls down most of the interface originated 2 μm and a few 100 μm in the mold, which is otherwise trapped back in slag layer when EMS is off. Moreover, this effect diminishes with shifting the EMS down.

Reuse of Acid Bioleachate in Bacterial Oxidation of a Refractory Gold Sulfide Concentrate

Bacterial pre-oxidation of refractory gold concentrates generates large volumes of leachate and requires a significant supply of nutrients to support bacterial growth. Therefore, bioleachate reuse reduces both water consumption and the nutrients required for the process. However, the efficiency of this method and its benefit need to be further explored. In the present study, two tests on the reuse of bioleachate in new cycles of bacterial oxidation were carried out to evaluate the efficiency and the benefit of bioleachate reuse. Our results showed that the reuse of bioleachates could reduce nitrogen and phosphorus requirements by 40% and 36%, respectively, after a 14-day biooxidation stage in a stirred tank bioreactor. We also showed that the reuse of bioleachate had a positive effect on the recovery of gold in a subsequent 48 h treatment by cyanidation. The gold recovery rate (initial concentration of 44 mg/kg) remained unchanged at 90% after the two bioleachate recirculation loops. The reuse of bioleachate also made it possible to increase the solubilization rates of other metals from the sulfide concentrate. Thus, the solubilization yields of copper (initial concentration of 3587 mg/kg) and zinc (initial concentration of 27,315 mg/kg) increased, respectively, from 14.8% and 40.2% to 37.5% and 99.6% after the two bioleachate recirculation loops.

High-potential control for durability improvement of the vehicle fuel cell system based on oxygen partial pressure regulation under low-load conditions

In the state-of-the-art high-power self-humidifying proton exchange membrane fuel cell (PEMFC) systems for vehicles, the high potential and low water production at idle or low load conditions strongly cause corrosion and decay of key materials and thus reduce durability. Therefore, the control technology of system-level durability requires an innovative design. Cathode recirculation is beneficial in alleviating the above unfavorable factors from the perspective of regulating oxygen and vapor partial pressure. This paper presents a pioneering study on the dynamics and control of cathode recirculation in vehicle high-power self-humidifying PEMFC system under low load conditions. First, a control-oriented dynamic model of the vehicle PEMFC system with a cathode recirculation loop is developed and the steady-state and dynamic performance is verified with experimental data from a 120 kW system. Active control of the intake component is achieved by re-feeding the reacted cathode gas to the air compressor outlet through a recirculation pump. On this basis, a high-potential controller based on oxygen partial pressure regulation is designed in combination with the dynamics of cathode recirculation. Results show that the designed dynamic fuzzy logic segmented proportional integral derivative controller with feedforward compensation achieves the optimal high-potential control effect by managing the oxygen partial pressure under variable low load conditions. It not only has excellent anti-disturbance ability but also effectively reduces the dynamic response time, transient overshoot, and steady-state error to satisfy the rapid and stable voltage output. Finally, the concomitant effect of humidification brought by the implementation of the optimal high-potential controller is analyzed, and the results show that the proton membrane is completely humidified.

Taylor bubble formation and flowing in a straight millimetric channel with a cross-junction inlet geometry Part II: Gas-liquid mass transfer

• Mass transfer was studied during bubble formation at a cross-junction. • Accuracy of resazurin-based technique was improved by advanced image systems. • Different mechanisms were observed for the developing O 2 concentration fields. • Oxygen concentration fields were measured during and after bubble pinch-off. • A scaling law relating k L a and f c was proposed to gather literature data. Using the resazurin-based colorimetric technique and advanced image acquisition, the equivalent oxygen concentration fields inside the liquid slugs were measured during and after the bubble formation stage at a cross-junction in a straight millimetric channel. Firstly, two different mechanisms were identified for the development of oxygen concentration fields depending on the two-phase Reynolds numbers (Re TP ). Under low Re TP , a jet-like central oxygen concentration ‘finger’ occurred between the newly formed bubble and the gas finger at the bubble pinch-off point. Right after the bubble pinch-off, the dissolved oxygen was transported first by the entering liquid from two side inlets, and later by the developing recirculation loop inside the liquid slug. Under higher Re TP , two highly concentrated oxygen concentration spots were formed near the bubble rear and the channel wall region, and a much more complex flow structure in the liquid slug appeared. Then, whatever the operating conditions, it was observed that the averaged oxygen concentrations inside the liquid slug followed a nearly linear relation as a function of the axial position in the channel, and that the related mass flux density decreased as far as the bubbles flowed along the channel’s length. The bubble formation process could be decomposed into three stages when considering the temporal evolution of the cumulated oxygen mass and depending on the development of the liquid slug. At last, the overall volumetric liquid side mass transfer coefficients ( k L a ) were deduced from the concentration fields, and found to linearly increase with the recirculation frequencies, leading to a scaling law.

Field Measurement of Central CO2 Heat Pump Water Heater for Multifamily Retrofit

Domestic hot water heating of multifamily buildings accounts for a substantial portion of the energy load of existing buildings. This load is made up of both the energy required to produce hot water and the energy needed to maintain the temperature of the heated water within a building’s distribution piping so that heat can be promptly delivered to building occupants as needed. Properly designed heat pump water heater (HPWH) systems have the ability to improve efficiency in both water heating and temperature control operations. Further, CO2 heat pump technology reflects a shift away from traditional refrigerants and toward refrigerants with low global warming potential (GWP). In this paper’s case study, a design consisting of multiple CO2 heat pump water heaters (commonly used in single-family homes) with a novel “swing tank” was proposed to meet the demand for domestic hot water heating and recirculation loop temperature maintenance. The proposed design was applied to the retrofit of a 60-unit, low-rise, multi-family building located in the Pacific Northwest of the United States. The purpose of this paper is to verify the performance of the system including the proposed “swing tank” in a centralized SHW system using CO2 HPWH. It also provides practical information and lessons learned from the retrofit project. Long-term monitoring data showed that the system had a coefficient of performance (COP) of three or greater and provided an average of 20 gallons of hot water per day per apartment. The results of this work indicate that residential-scale CO2 HPWH equipment and a “swing tank” design can efficiently provide domestic hot water heating and temperature maintenance for mid-sized multifamily buildings.

A Novel Mock Circuit to Test Full-Flow Extracorporeal Membrane Oxygenation.

Extracorporeal membrane oxygenation (ECMO) has become an important therapeutic approach in the COVID-19 pandemic. The development and research in this field strongly relies on animal models; however, efforts are being made to find alternatives. In this work, we present a new mock circuit for ECMO that allows measurements of the oxygen transfer rate of a membrane lung at full ECMO blood flow. The mock utilizes a large reservoir of heparinized porcine blood to measure the oxygen transfer rate of the membrane lung in a single passage. The oxygen transfer rate is calculated from blood flow, hemoglobin value, venous saturation, and post-membrane arterial oxygen pressure. Before the next measuring sequence, the blood is regenerated to a venous condition with a sweep gas of nitrogen and carbon dioxide. The presented mock was applied to investigate the effect of a recirculation loop on the oxygen transfer rate of an ECMO setup. The recirculation loop caused a significant increase in post-membrane arterial oxygen pressure (paO2). The effect was strongest for the highest recirculation flow. This was attributed to a smaller boundary layer on gas fibers due to the increased blood velocity. However, the increase in paO2 did not translate to significant increases in the oxygen transfer rate because of the minor significance of physically dissolved oxygen for gas transfer. In conclusion, our results regarding a new ECMO mock setup demonstrate that recirculation loops can improve ECMO performance, but not enough to be clinically relevant.

Evaluación hidrodinámica de un reactor airlift de recirculación interna con fluidos newtonianos y adelgazantes: Experimentación vs Simulación CFD

The hydrodynamics of an internal-loop airlift reactor was numerically and experimentally characterized. The gas holdup, liquid velocity, shear rate, flow pattern and volumetric oxygen transfer coefficient (kLa) were evaluated as a function of the air velocity and medium rheology. Tap water and CMC solutions were used as Newtonian and non-Newtonian fluids, respectively. The standard  model was employed for modeling turbulence, and unsteady three-dimensional simulations with the Euler–Euler model were performed. Gas holdup, liquid velocity and kLa measurements were performed for validating simulations. An increase in bubble coalescence and a decrease in kLa was observed with CMC solutions. The presence of recirculation loops inside the riser for CMC solutions is reported, which was not observed with tap water. The higher the CMC concentration, the larger the recirculation region seems to be. Results show that recirculation loops play a substantial role in the reactor’s hydrodynamic performance, and it turns out that the gas holdup in the riser increases with increasing the CMC concentration.

Practitioners’ Perspective on the Prevalent Water Quality Management Practices for Legionella Control in Large Buildings in the United States

Managing building water systems is complicated by the need to maintain hot water temperatures high enough to control the growth of Legionella spp. while minimizing the risk of scalding. This study assessed water quality management practices in large buildings in the United States. Surveys conducted with building water quality managers found that more than 85% of buildings have hot water temperatures that are consistent with scald risk mitigation guidelines (i.e., <122 °F/50 °C). However, nearly two thirds and three quarters of buildings do not comply with the common temperature guidance for opportunistic pathogen control, i.e., water heater setpoint > 140 °F (60 °C) and recirculation loop > 122 °F (50 °C), respectively; median values for both setpoint and recirculation loop temperatures are 10 °F (6 °C) or more below temperatures recommended for opportunistic pathogen control. These observations suggest that many buildings are prone to Legionella spp. risk. The study also found that 27% of buildings do not comply with guidelines for time to equilibrium hot water temperature, over 33% fail to monitor temperature in the recirculation loop, more than 70% fail to replace or disinfect showerheads, more than 40% lack a written management plan, and only a minority conduct any monitoring of residual disinfectant levels or microbiological quality. Given the rise in Legionellosis infections in recent years, coupled with highlighted water quality concerns because of prolonged water stagnation in plumbing, such as in buildings closed due to COVID-19, current management practices, which appear to be focused on scald risk, may need to be broadened to include greater attention to control of opportunistic pathogens. To accomplish this, there is a need for formal training and resources for facility managers.

Experimental demonstration of the performance of the novel thermosyphon heat transport device and comparison with CFD predictions

Thermosyphon heat transport device (THTD) is a novel system operating on the principle of single-phase natural circulation driven by density difference and is significantly different from a heat pipe wherein the flow is pressure driven. The present experimental and numerical analyses deliberate the heat transportation capability of THTD and its flow phenomena, which are linked to the operating conditions viz. Power, heating length, and flow rate of coolant. Experiments confirmed the instability for the entire range of parameters tested as a chaotic oscillation of temperature rise across the heater and temperature drop across the cooler is seen. Additionally, the temperature rise across the heater was found to be significantly larger than the temperature drop across the cooler, indicating the flow is not purely unidirectional natural circulation flow, which was further confirmed by CFD simulations. It also revealed that the unstable flow pattern is a unidirectional flow with a recirculation loop in the cooler, which has both downward and upward flows. The extent of downward flow is found to depend on the operating conditions. Further, the unidirectional flow is observed in the entire cold leg, heated section, and near to the inner adiabatic wall along the hot leg and the cooler. The essence of the study is that despite the unstable nature of flow for the entire range of parameters tested, the heat transport capability of THTD is uninterrupted.

Intensive Data and Knowledge‐based Approach for Sustainable and Circular Industrial Systems

ABSTRACTThe circular economy and its various recirculation loops have become a major study subject over recent years, particularly the transformation of the actual processes into sustainable processes. However, these environmental analyses require a huge quantity of data: foreground data and background data. The collection of these data can be long and tedious. Nevertheless, an increasing number of scientific articles describe the processes, which is a great source of data. This source of information is heterogeneous but big data tools can be used to compile, process and analyze them.Following this perspective, this paper focus on the creation of methodological framework centered on intensive data and knowledge for an economically viable and ecologically responsible design of industrial processes or systems. Composed of five steps, this approach is oriented towards offering decision support for the researcher or R&D engineer during systems requirements and high‐level design steps of V‐model. It is implemented within the domain of pre‐treatment processes for corn stover.

Development of an integrated hydropower system with hydrogen and methanol production

In the present study, a methanol synthesis plant integrated with a hydropower station with river hydro storage option is developed and analyzed thermodynamically to study the ability of increased benefit and sustainability via the generation of multiple useful commodities. The present system is, in this regard, designed to produce methanol steadily throughout the day at baseload and generate power at an increased rate during the on-peak period. This system also cogenerates heat and fresh water through reverse osmosis and oxygen via water electrolysis. The methanol synthesis unit is simulated in the AspenPlus in a recirculation loop based on a plug flow pressurized reactor. The reaction extent for synthesis reaches a maximum at an optimum temperature for any specified pressure. The water electrolysis is conducted at 80 °C and 2 kA/m2 since the parametric study confirms that at higher current density, the duty of the water preheating heat exchanger becomes high, which increases unnecessarily the capital investment. One key focus of the paper is to devise the operating strategy of hydro-storage, which is done for an illustrative case study in which the hourly Ontario electricity price (HOEP) for the year 2020. The system is controlled in such a way that the power generation during the on-peak periods is maximized for increased revenue. A river with a 425 m3/s annual average flow rate is assumed for the case study. The gross head for hydro-storage must reach a maximum at about 30 m at 7 a.m., and 6 p.m. and the storage pool is discharged to 23 m after morning peak and to 20 m after evening peak. The overall energy efficiency of the system is found to be 61.6%. The overall exergy efficiency of the system is obtained to be 58.2% with a generation mix of grid-delivered power, methanol, heating, oxygen and fresh water.

The thermal analysis of pre-defueled operation for decommissioning of a BWR4 reactor

After the operating license of the Nuclear Power Plant (NPP) has expired, a lack of storage capacity of the spent fuel pool (SFP) may occur when the dry storage facilities are not ready. As a result, the fuel of the last cycle will remain in the reactor vessel. When the NPP is under pre-defueled operation mode, it means the vessel head is removed, interconnecting with the upper cavity and SFP via movable gate. Hence, the reactor vessel, upper cavity, and SFP can be treated as an integrated system.This study has developed a MELCOR2.1/SNAP model to analyze the thermal response under the recirculation loop occurring break. There are two decay power conditions in this study: limited condition (7 days after shutdown) and realistic condition (942 days after shutdown). Based on the results of the recirculation line break accident under the limited condition with low-pressure coolant injection (LPCI), the core integrity may be challenged. And the realistic condition is less harsh than the limited condition; the core can be adequately cooled following a loss of coolant at the recirculation line break.

RIN induced penalties in G.654.E and G.652.D based distributed Raman amplifiers for coherent transmission systems.

Relative intensity noise (RIN) induced penalties were experimentally measured in distributed Raman amplifiers (DRAs) for G.654.E and G.652.D fibres with forward, backward and bidirectional pumping configurations. The measured signal RIN using the G.654.E fibre was ∼3.5 dB and ∼2 dB lower than the G.652.D fibre with forward (FW) pump configuration for PM-QPSK and PM-8QAM signals, with single span transmission showing a Q-factor improvement of ∼3 dB and ∼2.5 dB for G.654.E over G.652.D fibres. The performance penalty in a long haul coherent system was evaluated for 28 GBaud PM-QPSK signals using a recirculation loop for backward and bidirectional distributed Raman amplifiers. Our experimental results demonstrate an additional transmission distance of more than 1000 km for G.654.E over its counterpart G.652.D assuming a HD-FEC limit of 8.5 dB.

Analysis of flocculation in a jet clarifier. Part 2 - Analysis of aggregate size distribution versus Camp number

Among the various existing technologies for water treatment, the jet clarifier is considered as an effective and compact system as it couples flocculation and clarification in a single unit. In this work, a quasi-two-dimensional apparatus was designed to visualise the interaction between floc size distribution and hydrodynamics in the flocculation zone of a jet clarifier. Measurements of the number of flocs and their size distributions are performed by means of shadowgraphy method and image analysis. Thanks to a coupling between population size distributions and results on local hydrodynamics, the evolution of the number of aggregates along the jet is directly correlated to the recirculation loop present in the flocculation zone. The relative independence of the floc size distributions on the flow rate is discussed in light of the Camp number Gt which remains constant for different flow rates investigated and can thus explain the efficiency of the jet clarifier in terms of flocculation.

Investigation of Wet Milling and Indirect Ultrasound as Means for Controlling Nucleation in the Continuous Crystallization of an Active Pharmaceutical Ingredient

This study compares the use of wet milling and indirect ultrasound for promoting nucleation and controlling the particle size during the continuous crystallization of a hard-to-nucleate active pharmaceutical ingredient (API). Both an immersion and an external wet mill installed on a recirculation loop were investigated. It was found that all methodologies significantly improved the nucleation kinetics, and the effects of key process parameters (e.g., mill speed, temperature, and ultrasound intensity) on particle size were experimentally investigated. A minimum d50 of 27 and 36.8 μm was achieved when using the wet mill and ultrasound, respectively. The effectiveness of wet milling was demonstrated in a three-stage mixed suspension mixed product removal continuous crystallization of the API that was operated continuously for 12 h (eight residence times), achieving a steady state with minimal fouling. Strategies for improving the overall robustness of the setup in routine manufacturing are discussed.

EXPLORING LOCAL RECIRCULATION OF PAPER WASTE THROUGH UPCYCLING AND ARTISTIC RECYCLING

AbstractLocal recirculation of materials is a key aspect for a green transition, as it enables materials to be reused in new life cycles locally. In this article, we use the material “paper” as a case study to explore how this material recirculates at the local scales. This article aims at observing and evaluating upcycling scenarios as part of an expansion of local end-of-life possibilities compared to the current situation where paper end-of-life is reduced to a few recycling plants in France and abroad. This work relies on interviews and questionnaires that aim at understanding how paper is used and explored by artists to be recirculated in products. Indicators were tested to provide a methodology to compare different material circulation scenarios in terms of material use, environmental impact and value perception. Collaboration among multiple actors, artists, community centres, schools and industrial players is crucial for scaling up such recirculation loops.

Regulation and control methods for the unattached fraction of 220Rn progeny in a 220Rn progeny chamber

The unattached fraction of 220Rn progeny is one of the key parameters in lung dose evaluation models. To study the behavior of unattached 220Rn progeny and to prepare for calibration of the unattached 220Rn progeny monitors, a 220Rn progeny chamber that could stably regulate different unattached fractions of 220Rn progeny was established. A recirculation loop to eliminate the effects of the sampling and a loop connected to the dilution chamber to supplement the carrier aerosol were set up. Also, a theoretical model regarding the regulation of the unattached fraction of 220Rn progeny was established. Continuous measurements of the unattached fraction were conducted using the combination of a single-layer wire screen and a filter membrane. The experimental results showed that, under different aerosol levels, the relative standard deviation (RSD) of 212Pb concentration during the continuous samplings was within 10.7% and the RSD of the unattached fraction of 212Pb was within 9.9%. The relative deviation between the theoretical and the experimental values of 212Pb concentration was within 16.7% and the model calculation values of the unattached fraction of 212Pb were consistent with measured results.

Influence of mixing valve dynamics and recirculation loop connection to solar tank on large hot water system performances

A centralized solar domestic hot water system for a multi-family building is analyzed numerically. The solar preheated water in the solar tank is flowing into an auxiliary tank, connected to a gas boiler. At its output, a mixing device is used to ensure hot water at steady temperature before going through the recirculation loop. This reference system is sized as a typical installation under mild climate in France. The load profile is generated statistically with a one-minute time step. Small time scale phenomena have consequences on the global system behavior: recirculation flow rate variations due to pressure drop change is modeled and validated experimentally. This work’s goal is to analyze these effects on two sub-parts of the plant: mixing valve and recirculation loop connection to solar storage. In each case, yearly simulations with 6 s time step provide quantitative performance indicators for different sizing and control options. Results show that mixing valve slow response, due to ageing or bad design, leads to a loss of 3.5% energy savings compared to using a fast component. Furthermore, health risks increase as the minimal temperature in the recirculation loop is often under 50 °C, which promotes legionella development due to cold water plug flows generated in the loop by the mixing valve dynamic response. The recirculation loop, linked to a solar tank, leads to performance improvement with 6–15% increase in energy savings following solar oversizing and reduced overheating risks.