Cooling Water System Research Articles

Potential risk from and prevention of phytoplankton outbreaks in blocking the cooling water system in a nuclear power plant on the Southeast China coast

The invasion or aggregation of marine biota in coastal waters has become a common problem, threatening the safety of cooling water systems in the context of environmental and climate changes. However, studies on issues of coastal nuclear power plants from the view of marine ecology have mostly focused on the thermal effluent, entrainment effect on organisms, residual chlorine, radioactivity, etc. There is a lack of information on the safety of cooling water systems in nuclear power plants blocked by marine biota. Based on field and historical datasets, this study screened phytoplankton species that may potentially block the cooling water system of the Fuqing nuclear power plant on the Southeast China coast, identified the phytoplankton risk and a risk calendar, and established a catalog of risk phytoplankton species for the cooling water system. The screening criteria were simultaneously required as follows: (1) particle size of cells or group >2000 μm; (2) phytoplankton bloom or aggregation events occurred in surrounding areas; (3) and species abundance maintained at >0.5×105 cells/L in the surrounding area. Nine high-risk species were screened out that can easily form colonies, clusters, and groups, including Thalassiosira diporocyclus, Thalassiosira subtilis, Noctiluca scintillans, Phaeocystis globosa, Pseudo-nitzschia pungens, Pseudo-nitzschia delicatissima, Skeletonema costatum, Skeletonema dohrnii, Paralia sulcata. Due to small cells or the formation of short chains, some dominant phytoplankton species, even those with advantages in abundance and occurrence, had difficulty threatening the reliability of cooling water systems in nuclear power plants. The outbreak of different phytoplankton species varied daily, and the risk of blockage was highest from April to July. The biological characteristics, ecological mechanisms underlying outbreaks of high-risk phytoplankton species are reviewed and discussed, suggesting a high degree of temporal and spatial variability of blockage risk. Finally, main prevention and control measures used against high-risk phytoplankton species are provided to imply new ideas and methods for nuclear power plants. These strategies have very important practical and scientific significance.

Design of the Cooling Water System for the EAST Lower Divertor

The new lower tungsten divertor is a crucial component to achieve the targets of long pulse and high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> H-mode operation of Experimental Advanced Superconducting Tokamak (EAST) device. The cooling water system (CWS) of lower divertor should have sufficient heat removal capability and be able to cope with pressure transients caused by the potential water hammer events, which makes the design challenging. In this study, the system process and details of main component are determined based on the design requirements. The thermal-hydraulic analysis model has been developed by Flowmaster (FLOWMASTER) to conduct the heat transfer analysis. Furthermore, the system water hammer transients under one pump trip condition have been analyzed. The results show that the flow distribution of each client is uniform, and the pressure and temperature of key points meet the design requirements. The maximum pressure fluctuation, 0.16 MPa, caused by the sudden closing of the check valve is within the acceptable range. The experiment data are in good agreement with the simulation values, which proves the correctness of the model and the feasibility of the design.

Dynamic Event Tree Analysis as a Tool for Risk Assessment in Nuclear Fusion Plants Using RAVEN and MELCOR

In the broad framework of the nuclear power plants (NPPs) industry, the dynamic probabilistic risk assessment could answer the time dependence deficiency of the event tree and fault tree analysis. The basic event tree approach relies on experts’ pre-constructed accident sequences without exploring the time-dependent nature of an accident scenario, which could strongly affect the accident sequence. Conversely, the effects of events timing can be studied by adopting a dynamic event tree (DET) approach. Developing a DET methodology requires integrating a system code capable of replicating an accident scenario and a logic-driver code able to generate the event tree sequence, trigger plant safety systems, and manage other relevant events throughout the simulation. For this purpose, Methods for Estimation of Leakages and Consequences of Release (MELCOR) and reactor analysis and virtual control environment (RAVEN) have been coupled through a Python script developed by the Sapienza University of Rome, Rome, Italy, to perform DET studies during accident transients in fusion and fission reactors. RAVEN is a software tool developed at the Idaho National Laboratory (INL), Idaho Falls, ID, USA, to act as a control logic driver and post-processing tool for different applications. MELCOR for fusion is a fully integrated design basis and severe accident code that simulates thermal-hydraulic behavior and self-consistently accounting for aerosol transport in nuclear facilities and reactor cooling systems for the evaluation of the source term in fusion reactors. The coupling between these codes will provide a wide range of NPP risk assessment analyses, establishing new best practices. In this work, a preliminary DET study has been performed, selecting as initiating event an ex-vessel loss of coolant accident (LOCA) in the water-cooled lithium lead test blanket system (WCLL TBS) to be tested in International Thermonuclear Experimental Reactor (ITER). Time-dependent parameters such as the intervention of the plasma shutdown system and the closure of the main system isolation valves have been sampled to study evolving system scenarios.

Installation Design and Integration of Poloidal Field Converter Units for ITER

The poloidal field (PF) converter units (CUs) with the four-quadrant operation and circulating current capability is to supply power to International Thermonuclear Experimental Reactor (ITER) superconducting magnets. To ensure PF converter system safety and reliability for the operation, the safety distance of transformer installation calculated and studied. The electromagnetic field of the installed equipment is analyzed and discussed to determine the installation layout design of the equipment. When the converter power supply system operates at the steady-state rated current of 55 kA, the heat dissipation of the equipment is analyzed to determine the design of the cooling water system. The grounding of the system is calculated according to the application scenario. According to the equipment performance parameters and operation requirements of the PF converter system, the electrical, mechanical, and water system test and acceptance criteria test presented to ensure the state of system installation and integration and the safety and reliability of operation.

Post-warranty maintenance strategy selection using shape packages process

It is fair to assume that selection of a post-warranty maintenance strategy is one of the main challenges the capital-good owners face; however, there is relatively little research done in this area. This paper aims to assist asset owners in selecting the equipment maintenance package at the warranty termination time; it proposes the shape package process (SPP), which represents a comprehensive process that facilitates the choice between multiple packages, considering the cost and risk associated with each package.The main novelty of this paper is introducing two new parameters to compare maintenance packages: the risk reduction factor (RRF) to assess the maintenance task effectiveness in reducing non-financial risk and the value-added indicator (VAI) to evaluate the task efficiency in reducing the financial risk. Additionally, the suggested process includes mapping the risk profile associated with each package, enabling a cost-cutting process where the tasks with less value and risk mitigation can be easily identified and eliminated.A case study then demonstrates the process flexibility in comparing different maintenance packages using the analytical hierarchy process (AHP); while presenting RRF and VAI at the task and package levels when implemented in a cooling water system to select the post-warranty maintenance package from an asset owner's perspective.

Deep Forest-Based DQN for Cooling Water System Energy Saving Control in HVAC

Currently, reinforcement learning (RL) has shown great potential in energy saving in HVAC systems. However, in most cases, RL takes a relatively long period to explore the environment before obtaining an excellent control policy, which may lead to an increase in cost. To reduce the unnecessary waste caused by RL methods in exploration, we extended the deep forest-based deep Q-network (DF-DQN) from the prediction problem to the control problem, optimizing the running frequency of the cooling water pump and cooling tower in the cooling water system. In DF-DQN, it uses the historical data or expert experience as a priori knowledge to train a deep forest (DF) classifier, and then combines the output of DQN to attain the control frequency, where DF can map the original action space of DQN to a smaller one, so DF-DQN converges faster and has a better energy-saving effect than DQN in the early stage. In order to verify the performance of DF-DQN, we constructed a cooling water system model based on historical data. The experimental results show that DF-DQN can realize energy savings from the first year, while DQN realized savings from the third year. DF-DQN’s energy-saving effect is much better than DQN in the early stage, and it also has a good performance in the latter stage. In 20 years, DF-DQN can improve the energy-saving effect by 11.035% on average every year, DQN can improve by 7.972%, and the model-based control method can improve by 13.755%. Compared with traditional RL methods, DF-DQN can avoid unnecessary waste caused by exploration in the early stage and has a good performance in general, which indicates that DF-DQN is more suitable for engineering practice.

Eco-Efficient Vehicle Cooling Modules with Integrated Diffusers—Thermal, Energy, and Environmental Analyses

The automotive domain is a very good candidate for energy management, particularly due to the huge amounts of energy lost by heat through exhaust and water-cooling systems. This makes the optimization of vehicle cooling modules directly related to energy consumption and carbon dioxide emission. In this context, contemporary designs that employ diffusers between the forward-facing of an automobile and its heat exchanger subjected to airflow are presented in this work. The ultimate aim is to reduce the fuel consumption and carbon dioxide emissions of vehicles. Based on the aforementioned design, the intensity of the air velocity would be decreased but distributed over a larger exchanger surface. Consequently, the velocity non-uniformity of the airflow upstream would decrease and therefore, the thermal performance would increase. The above-mentioned conclusion is a result of parametric numerical analysis and its associated numerical results that disclosed the enhancement of water-air heat exchanger thermal performance. To perform a parametric numerical analysis of the heat exchanger thermal performance for the new suggested configurations, a computational code was developed and validated to estimate the thermal performance for a known set of parameters. It was shown that for an automobile, with engine power ranging from 100–200 kW that is utilized for three hours a day and equipped with a diffuser, reduction of up to 2.91 kg (3.89 L) of gasoline consumption and 9.51 kg of CO2 emission can be achieved per day. The originality of the present work resides in the use of diffusers in cooling modules of vehicles, the thermal modeling of heat exchanger’s thermal performance along with its associated code, and the parametric analysis performed to prove the potential enhancement related to the use of diffusers in the cooling modules.

Effects of Different Influencing Factors on Temperature Distributions and Cooling Performance of Turbocharger Bearing Casing

In order to study temperature distributions under different influencing factors and evaluate the cooling performance of the turbocharger bearing casing, water-cooling system experiments regarding the turbocharger bearing casing are carried out, and an improved fuzzy analytic hierarchy process (FAHP) evaluation method for evaluating its design performance is proposed firstly. Then, the effects of various factors such as cooling-water inlet flow velocity, cooling-water inlet temperature, cooling-water pressure and exhaust temperature on the cooling performance of the bearing casing are investigated according to the experimental results. Finally, the design performance of the water-cooling system in the turbocharger bearing casing is evaluated based on the FAHP evaluation method. The results show that the turbocharger bearing casing temperature and the temperature drop rate show a decreasing trend with the increase of inlet cooling-water velocity, but that the temperature and temperature rise rate increase with the increase of the inlet temperature of cooling-water and exhaust temperature; the temperatures under the inlet velocities of 4 m/s, 5 m/s and 6 m/s are reduced by 4.1%, 5.9% and 6.7% compared with that under 3 m/s, respectively. In addition, the bearing casing temperatures firstly reduce then increase with the increase of cooling-water pressure, where the boiling heat transfer plays an important role; points 1, 2 and 3 have relatively higher temperatures than other points under all working conditions; the bearing casing temperature of six measuring points also increases under a cooling-water pressure between 0.1 MPa and 0.25 MPa. Moreover, the performance evaluation value based on the FAHP method for the turbocharger bearing casing is 87.7620, and the performance evaluation level is good, which indicates that the water-cooling system in the turbocharger bearing casing has desirable design performance. This work provides reference for the turbocharger’s design and its cooling performance enhancement.

Conceptual Design of a Compact Divertor Heat Load Simulation Device: HIT-PSI

Linear plasma devices have been increasingly applied in investigating plasma–surface interaction (PSI) processes and divertor/scraped-off-layer (D/SOL) physics because of their economy, flexibility, and expandability. However, only a few existing linear plasma devices are able to obtain high heat and particle fluxes. In this work, we report a compact superconducting linear device, with its scientific goals and specific design methods, at Harbin Institute of Technology (HIT), HIT-PSI, capable of implementing an extreme plasma environment with beams of a long discharge pulse, as well as high heat and particle fluxes in the future fusion reactor regime of ITER/CFETR-like parameters. A five-coil integrated superconducting magnet is designed to generate a &gt;2.0 Tesla steady-state magnetic field for confining a long pulse plasma beam with a density of &gt;1020 m−3 produced by a cascaded arc plasma source. With a pump set of 2500 L/s and a water-cooled target system with bias voltage, it is expected to obtain high-density and low-temperature plasma beams with a heat flux of over 10 MW/m2. Subsystems of the platform, including the plasma source, superconducting magnets, vacuum system, and target holder system, are described in detail. In addition, the function and performance of the platform are numerically simulated and represented by SOLPS-ITER code to predict the laboratory simulation results.

Simulation, Set-Up, and Thermal Characterization of a Water-Cooled Li-Ion Battery System

A constant and homogenous temperature control of Li-ion batteries is essential for a good performance, a safe operation, and a low aging rate. Especially when operating a battery with high loads in dense battery systems, a cooling system is required to keep the cell in a controlled temperature range. Therefore, an existing battery module is set up with a water-based liquid cooling system with aluminum cooling plates. A finite-element simulation is used to optimize the design and arrangement of the cooling plates regarding power consumption, cooling efficiency, and temperature homogeneity. The heat generation of an operating Li-ion battery is described by the lumped battery model, which is integrated into COMSOL Multiphysics. As the results show, a small set of non-destructively determined parameters of the lumped battery model is sufficient to estimate heat generation. The simulated temperature distribution within the battery pack confirmed adequate cooling and good temperature homogeneity as measured by an integrated temperature sensor array. Furthermore, the simulation reveals sufficient cooling of the batteries by using only one cooling plate per two pouch cells while continuously discharging at up to 3 C.

Combined effect of elevated temperature and high strain rates on S690QL high strength steel

The effects of elevated temperature and high strain rate on S690QL high strength steel material properties are described. These data are meaningful for the design and structural safety assessment of critical artefacts (bridges, cranes, offshore structures) under combined extreme loadings (impact and explosion) and temperature conditions (fire). Tests were carried out in 20–900 °C temperature range and under three different high strain rates (250, 450 and 950s−1) by means of a Split Hopkinson Tensile Bar equipped with a water-cooled induction heating system. An insight into the influence of the material sampling position on the mechanical properties, i.e. core or peripheral samples is shown. The evolution of the main mechanical properties as a function of both temperature and strain-rate, spanning from quasi-static to dynamic conditions, is assessed. Prediction formulas, valid for 40 mm thick sections, for the yield strength of the core and peripheral materials are proposed. The constitutive parameters of Johnson–Cook’s strength model have been calibrated based on test results.

Optimal design of industrial cooling water systems considering economic performance and water savings

As large water-using systems in chemical industries, cooling water systems (CWSs) consume a large amount of water and power. Up to now, most research on the cooling water system mainly focuses on energy-saving aspects by using the series-parallel structure of the cooler network. In this work, to consider the water-saving aspects of the cooling water system, air coolers and closed cooling towers are applied. Considering the best implementation of air coolers and closed cooling towers, the trade-offs between energy consumption, water consumption, and capital cost should be considered. In this work, a multiperiod optimization of the cooling water system in a chemical plant is carried out. To achieve the above-mentioned trade-off, heat duty distribution between air cooling and water cooling is optimized. Meanwhile, a comparison of cooling performance between the open cooling system and closed cooling system is involved. The problem is formulated as a mixed-integer nonlinear programming (MINLP) model and solved by GAMS (The General Algebraic Modelling System) software to obtain the best cooling water system configuration. In a case study, the new method is used to guide the energy saving and water saving of the cooling water system in a refinery, which can reduce the total cost by at least 4%.

Evaluation of the performance of water-cooled VRF system for heat exchanger geometry under part-load operation

In this study, static numerical simulation was used to evaluate the performance of a water-cooled variable refrigerant flow (VRF) system for geometry of plate-type outdoor heat exchanger. In general, heat exchanger is designed based on full-load operating condition. Since most of operation for VRF system is part-load operation, part-load operating characteristics should be considered to optimize entire system. The geometry characteristics are divided into chevron angle and vertical length. Numerical models of cooling and heating modes were developed for the VRF system, system performance was represented by integrated energy efficiency ratio (IEER) for the cooling system and coefficient of performance (COP) for the heating system by AHRI standard 1230. Regardless of operating mode, 20° of chevron angle among 20°, 35° and 45° is the optimal angle of outdoor heat exchanger. The energy efficiency was proportional to the vertical length of the plate heat exchanger and inversely proportional to the chevron angle. In the cooling mode, the energy efficiency ratio (EER) calculation converged at a shorter vertical length of the heat exchanger with a decrease in operating loads. The optimal vertical length is 1.7 m with only considering full-load, and 1.2 m with considering part-load operation. In the heating mode, the tendency of energy efficiency was similar to that of the cooling mode. The optimal vertical length is 1 m which is 0.2 m shorter than the optimal length in cooling mode.

Analysis and optimization of operation mode of outlet communication valves for circulating pump in cold season

The circulating cooling water system of a coastal power plant adopts a unit seawater supply system. Each unit is arranged with three circulating water pumps. The operating mode of the circulating water pump in the cold season is two for operation and one on standby. If a running circulating water pump trips due to a fault, the standby pump will be activated by interlocking; meanwhile, an opening or closing command will be issued to the two outlet communication valves. According to the state of the outlet communication valve, the risks such as overpressure, condenser vacuum, water hammer, and pump reversal are analyzed. In order to reduce the possible risks in the cold season, an optimization scheme is proposed for keeping the outlet communication valves fully open. The feasibility of the optimization scheme in terms of flow distribution and pipe and equipment stability is also analyzed. The outlet communication valve optimization scheme will reduce operational risk and ensure the safe and stable operation of the circulating water system. The optimization scheme provides reference and experience feedback for the follow-up circulating water system design and operation.

Water-cooling diamond anvil cells: An approach to temperature-pressure relation in heated experiments.

Temperature induced pressure drift in the diamond anvil cell (DAC) is a major issue in high-pressure high-temperature experiments. It is commonly acknowledged that these drifts originate from multiple factors, but no systematic descriptions have been made so far. By introducing an internal water-cooling system in the DAC, we have performed a systematic investigation into temperature induced pressure drifts to reveal the mechanism behind them and to find a proper experimental procedure to achieve minimal pressure variation in DAC's heating experiment. It is revealed in this experiment that pressure variation during heating processes originates from multiple temperature related factors of the DAC. The variation itself can be considered as a rebalancing process of the compression forces on the sample chamber initiated by the disturbance caused by temperature elevation. It is possible to suppress pressure variation by maintaining the temperature of the DAC body at room temperature to ensure the consistency of compression on the sample chamber. At the same time, the best procedure for the heating experiments is to properly pre-heat the sample chamber equipped with the internal water-cooling system before performing the in situ measurements on the temperature-related properties at the pressurized and heated conditions. Our discovery provides a reliable procedure for the sample heating process in the DAC and helps resolve the complex mystery of the influence of the combination of pressure and temperature in high-pressure high-temperature experiments.

Research on pipeline connection structure of microwave load water-cooling system for spacecraft thermal test

The microwave load water-cooling system was operated in a vacuum cold black environment, and the pressure difference between the inside and outside of the water pipe could reach 0.3 to 0.4 MPa. To ensure the tightness of the water pipe, a conical seal structure was selected, the macro-static model and micro-boundary element contact model were established for the two forms with and without the Viton seal. The macro model simulation was performed by the finite element method to obtain the stress distribution inside the conical structure under different preload stress, the relationship between the contact pressure of the conical sealing interface and the contact area of the O-ring sealing interface as a function of preload stress; the method was used to calculate the micro-contact model, and the critical contact pressure and contact area to achieve the sealing requirements were obtained respectively without Viton seal and with Viton seal. As a result, a conical seal structure with a Viton seal was finally chosen for application. After verification, the structure meets the requirements for the use of microwave load water-cooling systems during the vacuum thermal test.

Investigation on Water Immersing and Spraying for Cooling PV Panel

The use of photovoltaic cells has increased dramatically in recent years. However, the photovoltaic cells convert most of the solar radiation into heat, and this heat negatively affects the PV productivity. Therefore, a cooling system can get rid most of this heat. An experimental and theoretical examination is conducted for the augmentation of PV power and efficiency by using two different water cooling systems. The PV cooling has been equipped with two types of water-cooling systems, i.e. immersion, and spraying. For the immersion cooling, the temperature decrease is achieved but the power output has been low. On the other hand, the water spraying cooling has been studied at three different chilled water flow rates. The solar simulator having an average radiation of 1300 W/m2 is generated through 50 W halogen lights for testing. It has been found out that a 60% temperature reduction has been achieved, with a remarkable increase in power output by 59% and efficiency by 8%. However, no remarkable difference has been achieved by varying water flow rates. Therefore, cooling by spraying system has given better results than immersion. Finally, the experimental results have been found to be consistent with the numerical results.

Питание тиляпии мозамбикской (Oreochromis mossambicus) бактериально-водорослевыми матами в водоёме-охладителе Нововоронежской АЭС

The formation of stable periphyton communities is undesirable for all types of hydrotechnical systems, especially functioning watercooling systems. To combat the development of biological fouling in the cooling ponds of nuclear power plants bioreclamation species are widely used, which include Mozambican tilapia. It was unintentionally brought into the cooling reservoir of the Novovoronezh nuclear power plant; however, it formed a stable and numerous population there. The food base for the fish population in the cooling pond is depleted due to difficult (sometimes extreme) environmental conditions, which can lead to competition for food items. Under these conditions, tilapia switches to feeding on bacterial-algal mats, which develop abundantly in the warm-water part of the reservoir. In areas eaten by tilapia, the biomass of fouling is reduced by one and a half times and the content of mineral substances decreases. The study of the contents of the intestines of tilapia made it possible to confirm these observations, since representatives of the phytoperiphyton were found in the food bolus: cyanoprokaryotes, diatoms and green algae, for which even a taxonomic affiliation was established. The results of the research made it possible to clarify the mechanism o f integration of this southern species into the ichthyocenosis of the reservoir and its positive role in reducing biofouling.

Synergistic experimental investigation of the nano-ceramic cover sheet on the PV module performance

Due to the accumulation of the heat on surface of the photovoltaic collector as well as the module’s components, the efficiency of photovoltaic (PV) module is influenced by the increase of temperature in particular at high load (high voltage). Therefore, the efficiency and the current output decrease dramatically, and the full performance of the module tends to be zero in these conditions. In the present work, an experimental comparison between a controlled active water-cooling system and nano-ceramic cover sheet system is performed to get the best performance in high load. Water-cooling system is designed to minimize this effect of the high temperature and dust on the photovoltaic module. In addition, the nano-ceramic cover sheet is installed on the module to reduce the infrared permeability. Furthermore, Experiments were performed on the plain module without active cooling or nano-ceramic cover. After the experimental comparison, the results indicated that the controlled active water-cooling system is extremely improve the performance on the contrary the nano-ceramic cover sheet system which reduces the performance.

Design modification of the existing cooling water system of Marsyangdi hydropower station using pipe flow modeling software

Marsyangdi Hydropower Station has adopted the Open Loop Cooling System (also called Once through Cooling System) in which the cooling water extracted from Penstock or the draft tube is circulated throughout the cooling system and discharged back to the draft tube. The water of the Marsyangdi River is muddy and sediment-rich in the rainy season, which causes the choking of tubes of the primary heat exchangers reducing the cooling efficiency and even leading to leakages in the tubes due to erosion. Cleaning and maintenance of the tubes are impossible without dismantling the primary heat exchangers from the Unit assembly. Hence, hours of machine shutdown is required to replace them with new or cleaned one. A Close Loop Cooling System has been modeled in the Software, "AFT Fathom," to overcome the issue in the Existing Cooling System. The modified model was run to observe the performance of the modified system at different river water temperatures and increased heat duty in all the heat exchangers. Further, the System Curve was considering the effect of the increase in surface roughness of pipelines due to aging. The performance capacity of the modified system was justified considering the obtained results from the simulations.