Water Circuit Research Articles

Hospital-acquired Legionella pneumonia outbreak at an academic medical center: Lessons learned

BackgroundAn outbreak of Legionella pneumonia occurred at a university hospital using copper-silver ionization for potable water disinfection. We present the epidemiological and laboratory investigation of the outbreak, and associated case-control study. MethodsCases were defined by syndrome compatible with Legionella pneumonia with laboratory-confirmed Legionella infection. The water circuit and disinfection system were assessed, and water samples collected for Legionella culture. Whole genome multi-locus sequence typing (wgMLST) was used to compare the genetic similarity of patient and environmental isolates. A case-control study was conducted to identify risk factors for Legionella pneumonia. ResultsWe identified 13 cases of hospital-acquired Legionella. wgMLST revealed >99.9% shared allele content among strains isolated from clinical and water samples. Smoking (P= .008), steroid use (P= .007), and documented shower during hospitalization (P= .03) were risk factors for Legionella pneumonia on multivariable analysis. Environmental assessment identified modifications to the hospital water system had occurred in the month preceding the outbreak. Multiple mitigation efforts and application of point of use water filters stopped the outbreak. ConclusionsPotable water system Legionella colonization occurs despite existing copper-silver ionization systems, particularly after structural disruptions. Multidisciplinary collaboration and direct monitoring for Legionella are important for outbreak prevention. Showering is a modifiable risk factor for nosocomial Legionella pneumonia. Shower restriction and point-of-use filters merit consideration during an outbreak.

Thermal evaluation of a component heating system for a monastery cell with measurements and CFD simulations

This paper presents a comprehensive analysis of the thermal behaviour and the flow characteristics of a monastery cell with integrated component heating system (CHS). For the evaluation of the system the heating characteristics and the resulting thermal behaviour was investigated. The intention was to develop a model for similar thermal refurbishment projects using wall-integrated low-temperature component heating systems. In a first step a long-term measurement campaign was installed in the monastery cell to gather real life data. In a second step a stationary and transient three-dimensional Computational Fluid Dynamics (CFD) simulation was set up, followed by the validation of the CFD simulation model using the collected measurement data. The CFD model included the entire surrounding building structure, the CHS hot water circuit and the inner air space. The here presented study contains a detailed analysis of the heating up and cooling down phase of the CHS and the total cell. The influence of the most important heating parameters like the water supply temperature or the mass flow rate as well as the influence of the solar radiation or different heating pipe plaster materials on the thermal behaviour of the cell air space and building structure was investigated. Furthermore, a parameter analysis was made in which the CHS was compared with a conventional radiator system.

Identification and Metabolism of Naturally Prevailing Microorganisms in Zinc and Copper Mineral Processing

It has only recently been discovered that naturally prevailing microorganisms have a notable role in flotation in addition to chemical process parameters and overall water quality. This study’s aim was to assess the prevailing microbial communities in relation to process chemistry in a zinc and copper mineral flotation plant. Due to the limitations of cultivation-based microbial methods that detect only a fraction of the total microbial diversity, DNA-based methods were utilised. However, it was discovered that the DNA extraction methods need to be improved for these environments with high mineral particle content. Microbial communities and metabolism were studied with quantitative PCR and amplicon sequencing of bacterial, archaeal and fungal marker genes and shotgun sequencing. Bacteria dominated the microbial communities, but in addition, both archaea and fungi were present. The predominant bacterial metabolism included versatile sulfur compound oxidation. Putative Thiovirga sp. dominated in the zinc plant and the water circuit samples, whereas Thiobacillus spp. dominated the copper plant. Halothiobacillus spp. were also an apparent part of the community in all samples. Nitrogen metabolism was more related to assimilatory than dissimilatory nitrate and nitrite oxidation/reduction reactions. Abundance of heavy metal resistance genes emphasized the adaptation and competitive edge of the core microbiome in these extreme conditions compared to microorganisms freshly entering the process.

Modelling of A Solar Thermal Energy System For Energy Efficiency Improvement In A Ceramic Plant

The thermal energy use in the manufacturing plants is the most representative parcel of the total energy consumption within the European industry. Such is mainly attributed to the operation of high energy intensive thermal processes such as furnaces and boilers. The implementation of heat recovery technologies is a solution with a great potential to improve the operation of these processes and improve the overall energy efficiency in a plant. On the other hand, the use of renewable energy resources such as solar energy is highly relevant measure to decrease the use of fossil fuels, such as natural gas. This paper presents the modelling of a solar thermal energy system (STES) established by a water circuit and solar thermal collector for the heat supply to two boilers installed in a ceramic plant. Such system has been conceptualised in the scope of industrial practices, proposing solar heat for industrial processes (SHIP). The practical work in this paper aims to the development of a customised simulation tool for the modelling of heat recovery networks and thermal processes in manufacturing industry plants using the Modelica language. The system model has been developed using existing and newly developed equipment models. The simulation results were validated with measured data in the industrial plant, being consistent with the real values (e.g. highest deviation of about 0.01%). In addition to the boilers, the performed simulation allowed to achieve the sizing of the components of the water circuit, in particular for the pumping system (with a required supply of 0.747 kW of electric energy). A techno-economic assessment has been performed to evaluate the viability of the cproposed solution, showing a payback time of approximately 3 years, a total annual economic savings of about 25209 € and associated reduction of equivalent carbon dioxide emissions of about 170 ton/year.

EVALUATION OF ENERGY EFFICIENCY OF CONDENSING ECONOMIZERS FOR STEAM AND HOT WATER BOILERS

An assessment of the feasibility of the development and implementation of a condensing economizer (CE) for the TGM-96A steam generator has been carried out. The CE cools fuel gases from 123 °C to 47 °C, and also has a very high heating capacity, ranging from 21 to 23.5 Gcal/h. The heat recovered due to the CE installation will heat three water circuits: one for untreated river water and two with water from district heating networks (DH). The expected value of the steam generator efficiency will increase by 10.55%. Complete thermal calculations of the condensing economizer have been carried out, and heat transfer fluids have been determined by flow rate and temperature, respectively. On the basis of calculations of heat and mass transfer processes, the heat capacity of the economizer was estimated under conditions of partial condensation of water vapor from flue gases. The analysis carried out allows us to give an objective assessment of the investment of the proposed project, and other financial indicators and environmental benefits that give the investor the opportunity to implement the project. Key words: condensing economizer (CE), exhaust gases, energy efficiency.

Prediction of boiler gas side effective heat transfer coefficients using mixture density networks and historic plant data

Machine learning has received increased recognition for applications in engineering such as the thermal engineering discipline due to its abilities to circumvent thermodynamic simulation approaches and capture complex inter-dependencies. There have been recent headways to couple deep learning models to process simulations, given the deeper insight they can provide. The present study entails the development of a mixture density network (MDN) capable of predicting effective heat transfer coefficients for the various heat exchanger components of a utility scale boiler. Large boilers are susceptible to dead zones and other anomalous phenomena that influence performance and manifest as multimodalities in the measured data, which system-level 1D process models struggle to capture. The overall water-side heat load calculation, as well as mass and energy balances around the components were done to determine the heat transfer coefficients at each stage of the boiler using historic sensor data. The measured data was then used to train a deep learning model capable of outputting predicted heat transfer coefficients and local model uncertainty. The predictive model can be coupled to a water circuit process model which can be used to study aspects such as metal temperatures and operating philosophies at the different operating loads of the plant.

Understanding ATLAS infrastructure behaviour with an Expert System

The ATLAS detector requires a huge infrastructure consisting of numerous interconnected systems forming a complex mesh which undergoes constant maintenance and upgrades. The ATLAS Technical Coordination Expert System provides, by the means of a user interface, a quick and deep understanding of the infrastructure, which helps to plan interventions by foreseeing unexpected consequences, and to understand complex events when time is crucial in the ATLAS control room. It is an object-oriented expert system based on the knowledge composed of inference rules and information from diverse domains such as detector control and safety systems, gas, water, cooling, ventilation, cryogenics, and electricity distribution. This paper discusses the latest developments in the inference engine and the implementation of the most probable cause algorithm based on them. One example from the annual maintenance of the 15°C water circuit chillers is discussed.

Optical fibre long period grating based chemical sensor for the analysis of silica in boiler water

Silica deposits in turbine blades, boiler tubes and cooling water circuits lead to serious loss in efficiency of power plants. Hence silica deposition is one parameter that is seriously monitored i...

Analysis of the operating parameters in a Stirling cryocooler

In this work, the results obtained in different tests performed on a Stirling cryocooler are shows, as well as a comparative analysis of these results with different load pressures. The prototype is a single-acting Stirling engine with a piston and displacer, which is used to liquefy air with helium as the working fluid; this is an integral Stirling (β-type). A three-phase asynchronous electric motor drives the Stirling engine and cooling, in the hot focus, is performed with a pressurized water circuit. In the cold focus are reached very low temperatures, around 75 K (-198 °C). The study has been developed at different load pressures of the working fluid and it shows a comparative analysis about the most important work parameters evolution. The parameters studied are the following: cooling water inlet and outlet temperatures, cold and hot focus temperatures, voltage and intensity consumed by the electric motor that drives the Stirling engine and quantity of liquid air obtained. The results show that it is very likely to use this configuration in industrial processes when they need cold and heat simultaneously.

H2 generation at metal oxide particle surfaces under γ-radiation in water

ABSTRACT The formation of hydrogen gas in the water circuits of nuclear power plants has implications for the safe and efficient operation of the plant and so requires thorough investigation. Therefore, typical metal oxides found on water circuit structural material surfaces have been subjected to γ-radiation in water, and the production of H2 by radiolysis has been analysed as a function of oxide composition and water content. The observed radiolytic hydrogen yields, G(H2), were analysed as a function of structural material oxide showing that the presence of the metal oxides increased the rate of hydrogen production relative to neat water radiolysis due to energy absorption by the oxides. The increase in the rate of H2 production was dependent on the oxide composition. The G(H2) value increased at low water weight fractions indicating surface effects are important in the H2 production mechanism.

Removal of volatile organic compounds from Waste air stream of a furniture factory

In this paper, an alternative to the thermal oxidation of VOC in a gaseous effluent was studied, to lessen power consumption and mitigate the environmental impact of a furniture factory located in the north of Portugal.A gas–liquid absorption of n-butyl acetate in a packed-bed column of LECA was studied to achieve a VOC outlet in agreement with the Portuguese law for effluent discharge in the atmosphere. Studies of VOC physical absorption with water were evaluated.Experiments with a continuous flow of tap water demonstrated to be very effective in removing n-butyl acetate of the air stream. Efficiencies over 90% were achieved by this method and in three experiments outlet VOC concentration remained under the imposed limit of 50 mgC/Nm3. Other experiments were registered to be above the imposed limit, even so, they were also highly effective, suggesting that if the outlet water can be reused and employed for other purposes, this solution might have an industrial interest. In the other studied approach, with a closed water circuit, the system proved to be less effective, with the removal efficiency of the VOC dropping very fast, which revealed the need for continuous treatment of the recirculated water.When introducing the microorganisms to the system, the efficiency was lower than for open circuit, averaging, 40.2%, 27.0%, 25.5%, respectively in the three experiments realized, suggesting that the system might be an interesting and a sustainable alternative to the ROT system employed at the factory, with a significant reduction in the energy consumption.

Agua y arquitectura en la Alpujarra de Granada (España): Una aproximación a los conjuntos hidráulicos de las fuentes y los lavaderos de la comarca

La arquitectura y el urbanismo de la Alpujarra presentan un fuerte carácter comarcal que fue definido en época andalusí y que todavía conserva parte de los elementos que lo conforman. Entre ellos, las fuentes y lavaderos constituyen uno de los conjuntos arquitectónicos más característicos de los núcleos de población de una región cuyo paisaje está fuertemente determinado por el aprovechamiento del agua de la vertiente sur de Sierra Nevada. Una compleja red de acequias permite regar los bancales de cultivo, que estructuran y cualifican este territorio, mientras que las fuentes, abrevaderos, lavaderos y albercas ofrecen servicios públicos y articulan el trazado urbano. En esta investigación se realiza una aproximación a los conjuntos hidráulicos de la comarca de la Alpujarra granadina, para lo que se estudian su localización urbana, su circuito de agua y la morfología de sus elementos. Así mismo, se pone el foco en su valores patrimoniales y en su relevancia para los sentimientos identitarios de la población local.

Charge transfer across the Cr2O3, Fe2O3, and ZrO2 oxide/water interface: A pulse radiolysis study

The transfer of electrons across the oxide/water interface has been investigated for oxide particles which are typically found incorporated into structural material surfaces within water circuits of nuclear systems. A pulse radiolysis study was conducted in order to observe the generation and decay kinetics of hydrated electrons in water in the presence of metal oxides. The presence of the oxides was found to have an effect on hydrated electron decay behaviour, with Fe2O3 retarding the decay rate and ZrO2 increasing the decay rate. The presence of Cr2O3 appeared to have negligible effect on the decay rate. The electron yield after the irradiation pulse was found to increase for all oxide/water mixtures relative to neat water, indicating electron transfer from the oxide to the water. The responses were attributed to electronic properties such as the band gap of the materials with respect to redox reactions at the material surface, as well as the effect of hydroxyl radicals on electron behaviour in the presence of the oxides.

Thermal Design and Experimental Verification of Double Helium Gap Conduction Test Facility

In order to obtain the heat transfer characteristics of the helium gap in conditions of different material thicknesses and linear power in high-temperature ranges, on the basis of previous research, an existent test device was improved. Through the theoretical design of double helium, the test device can perform experiments under high-temperature conditions. Compared with the experimental data, the theoretical design values are in good agreement with the experimental results. According to the design results of the test device, the helium gap test can be successfully carried out out in a high-temperature range, and the test results can provide reference for the design of the material irradiation assembly. The objective of this paper is to set up a multilayer helium gap according to the structural design of the irradiation device to achieve a helium gap test under high-temperature conditions under water circuit conditions.

Design of Nursing Bed Control System Based on STM32

In order to solve the problems of low intelligence, lack of function in the domestic nursing beds, a multifunctional intelligent nursing bed for daily care in homes and nursing homes was designed. The control system adopts STM32 series chips as the control core, uses PWM modulation to simultaneously control the working state of multiple linear drivers and solenoid valves to achieve posture adjustment. The closed-loop control of the working status of the air circuit and water circuit hardware through the pressure sensor and PID adjustment algorithm realizes the function of sewage treatment. Improve the intelligence of nursing bed through the design of voice recognition and remote communication module. The application of the control system improves the convenience of operation, control intelligence and safety and reliability of nursing bed equipment.

Evolution of the Safety of Fast Neutron Reactors

In its history, fast neutron reactors (BR) have gone through a long evolutionary period. However in general, BRs have gone the way of the evolutionary development. The function of retention radioactivity in case of an accident was performed by BRs safety vessels. For protection against external influences, new BR projects must be constructed containments. In the function of the reactor core cooling, changes have occurred related to the transition of the emergency cooling from the water circuit to the intermediate sodium circuit. Developments in emergency cooling systems are associated with the placement of an emergency heat exchanger inside the reactor, and the use of natural circulation in sodium and air. In the function on reactivity controlling due to the increase in core sizes, difficulties arise with the suppression of positive reactivity caused by sodium void reactivity effect. Therefore, in BR projects, the use of sodium plenum over the fuel part of the core and / or use of heterogeneous cores are needed. With an increase in the core sizes, the risk of jamming the long shifts of emergency rods increases. Therefore, it is advisable to transfer the safety rods to the hydraulic suspension in a sodium stream.

A case study on the treatment and recycling of the effluent generated from a thermo-mechanical pulp mill in Brazil after the installation of a new bleaching process

A Brazilian thermo-mechanical pulp mill (TMP) was evaluating the installation of a proposed bleaching process, with changes in the qualitative and quantitative characteristics of the wastewaters and the Effluent Treatment Plant (ETP). The objectives of this research were to evaluate the treatment plant configuration for the future industrial effluent, consisting of a flotation unit followed by an upflow anaerobic sludge blanket reactor (UASB), an activated sludge process and nanofiltration (NF) using polymeric membranes, and to study the technical feasibility of recycling the treated effluents in the industrial process. The possible options for recycling the treated effluent were determined through a water balance of the mill. The pulp quality was evaluated in laboratory bleaching assays, based on brightness and brightness reversion tests after the recycling of 50%, 75% and 100% of the treated effluent. The buildup of the non-process elements (NPE) in the industrial water cycle after each effluent recycling proportion was evaluated through computer simulation, using the Aspen Plus® simulator software. The future mill effluent, considering the implementation of a proposed bleaching stage with hydrogen peroxide, was generated in the laboratory and treated in a bench-scale effluent plant, simulating the future configuration. The treatment plant removed 99.8%, 99.2% and 61.6% of soluble COD, BOD5 and color, respectively. The water consumption was highest in the bleaching plant and, therefore, the recycling of 50%, 75% and 100% of the treated effluent for washing the pulp was simulated. The brightness and brightness reversion of the pulp, with 100% of the treated effluent used in the bleaching process, were similar to those provided by fresh water. The recycling of 100% of the treated effluent in the proposed treatment plant was possible in the TMP pulp mill without decreasing the pulp quality.

Increasing the Energy Efficiency of an Internal Combustion Engine for Ship Propulsion with Bottom ORCs

The study examines the option of adding a bottom Organic Rankine Cycle (ORC) for energy recovery from an internal combustion engine (ICE) for ship propulsion. In fact, energy recovery from the exhaust gas normally rejected to the atmosphere and eventually from the cooling water circuit (usually rejected to the sea) can significantly reduce the fuel consumption of a naval ICE during its operation. In the paper, different possible bottom ORC configurations are considered and simulated using the Aspen® code. Different working fluids are taken into account, jointly with regenerative and two-temperature levels designs. The energy recovery allowed by each solution is evaluated for different engine load, allowing the identification of the most suitable ORC configuration. For the selected case, the preliminary design of the main heat exchangers is carried out and the off-design performance of the whole combined propulsion plant (ICE + ORC) is evaluated, leading to a preliminary analysis of cost saving during normal ship operation. The results of this analysis show an increase in power output of about 10% and an expected Payback Time of less than 6 years.

О ВЛИЯНИИ СОДЕРЖАНИЯ КИСЛОРОДА НА ТЕПЛООБМЕН ПРИ ПОПЕРЕЧНОМ ОБТЕКАНИИ ПАРОГЕНЕРИРУЮЩИХ ТРУБ В РЕЖИМАХ НОРМАЛЬНОГО ТЕПЛООБМЕНА И С ЗАМОРАЖИВАНИЕМ СВИНЦА

The BREST-OD-300 steam generator project being developed at NIKIET is pioneering both in terms of the heat carrier used (lead) and in design implementation (coils of helical heat transfer tubes). The advantages of the designs of steam generators made in the form of helical coiled tubes, in comparison with straight tube designs are obvious. Helical coiled tubes are used in heat exchange equipment not only to increase the heat transfer surface, to solve the problem of thermal expansion, but also to increase the coefficient of heat transfer to the fluid flowing inside the tubes. In 2011-2017 years the thermohydraulic tests of various models of lead-heated steam generator were carried out at the IPPE SPRUT facility (IPPE). The test program was aimed to study the heat transfer and the thermal-hydraulic stability of the steam generating tubes. Throughout the entire range of changes in operating parameters, no pulsating modes were detected with overturn of circulation in the water circuit. The design temperatures of superheated steam were obtained in nominal operation. The results provide extensive information on water heat transfer in different zones of the steam generating channel under various operating conditions (nominal and partial modes, starting modes). However, to verify the computer codes, experimental data on the heat transfer of lead coolant around the bundles of heat transfer tubes are necessary. Due to the small twist angle of the tubes in a full-scale steam generator, it can be said that heat transfer is close to heat transfer during transverse flow. A model with a transverse flow of lead coolant around steam-generating tubes was developed at the SSC RF - IPPE. The main goal of the research was to obtain data on the effect of oxygen concentration in lead on heat transfer in normal heat transfer modes and with lead freezing. Throughout the entire range of changes in the initial temperature values of lead and water, blocking of the annular space by frozen lead was not recorded.

The role of molybdate‐containing inhibitors in cases of stress corrosion cracking in closed water circuits

AbstractIn this study, three cases of damage to heating circuits are presented, in which damage was caused by intergranular stress corrosion cracking in an unalloyed steel. The results are compared with literature data. From this, it can be concluded that stress corrosion cracking has been triggered in all three cases by the addition of an inhibitor containing molybdate. The development of this form of corrosion is only possible under critical conditions.