Condensate Pump Research Articles

Modal Analysis and Optimization of Fluid-Structure Coupling for Rotor and Inner Cylinder of Vertical Condensate Pump

Background: Low-frequency resonance is one of the common issues encountered during the variable-frequency operation of condensate water pumps. There have been numerous patents and papers proposing solutions to address the low-frequency resonance problem in condensate water pumps. However, the solutions for resonance problems often need to be tailored to specific circumstances. Methods: Based on the acoustic method, the dynamic model of the rotor and inner cylinder of Jiangsu Guohua Chenjiagang Power Plant 2B condensate pump is established to compare the difference between dry modal and fluid-structure coupling modal, the influence of perpendicularity, concentricity and bearing wear on the natural frequency of rotor is studied. Results: The rotor is rigid under normal conditions. When the bearing is worn, the frequency of the rotor will be greatly reduced and may fall into the frequency conversion operation range to excite resonance. The deviation of perpendicularity and concentricity will not directly lead to the decrease of rotor modal but will lead to the increase of bearing stress, aggravate bearing wear, and then affect the rotor modal. As the inner cylinder only relies on the fixed support at the top, the structure stiffness is low, which may lead to low-frequency resonance. By adding two support structures at the guide vane, the first-order modal frequency of the inner cylinder can be increased from 3.29 Hz to 28.88 Hz, effectively avoiding the operating frequency range of the system. Conclusion: This study can guide the optimization of similar pump structures.

A Reduced-Order Model of a Nuclear Power Plant with Thermal Power Dispatch

This paper presents reduced-order modeling of thermal power dispatch (TPD) from a pressurized water reactor (PWR) for providing heat to nearby heat consuming industrial processes that seek to take advantage of nuclear heat to reduce carbon emissions. The reactor model includes the neutronics of the reactor core, thermal–hydraulics of the primary coolant cycle, and a three-lump model of the steam generator (SG). The secondary coolant cycle is represented with quasi-steady state mass and energy balance equations. The secondary cycle consists of a steam extraction system, high-pressure and low-pressure turbines, moisture separator and reheater, high-pressure and low-pressure feedwater heaters, deaerator, feedwater and condensate pumps, and a condenser. The steam produced by the SG is distributed between the turbines and the extraction steam line (XSL) that delivers steam to nearby industrial processes, such as production of clean hydrogen. The reduced-order simulator is verified by comparing predictions with results from separate validated steady-state and transient full-scope PWR simulators for TPD levels between 0% and 70% of the rated reactor power. All simulators indicate that the flow rate of steam in the main steam line and turbine systems decrease with increasing TPD, which causes a reduction in PWR electric power generation. The results are analyzed to assess the impact of TPD on system efficiency and feedwater flow control. Due to the simplicity of the proposed reduced-order model, it can be scaled to represent a PWR of any size with a few parametric changes. In the future, the proposed reduced-order model will be integrated into a power system model in a digital real-time simulator (DRTS) and physical hardware-in-the-loop simulations.

МОДЕЛИРОВАНИЕ ПРОЦЕССОВ ВЛАГОПОГЛОЩЕНИЯ ДРЕВЕСИНЫ ПРИ ИЗМЕНЕНИИ ДАВЛЕНИИ СРЕДЫ

On the basis of differential equations of material balance in a hermetic chamber and heat and mass transfer in the object under study under given boundary conditions, a mathematical model describing technological processes occurring with changes in medium pressure has been developed. The methodology of experimental studies of the process of material saturation in a unit operating in a periodic mode at varying medium pressure is presented. Birch veneer is taken as a model material for experimental studies, the heat and mass transfer characteristics of which are widely known. The preparation of the experiment consisted in the production of samples of the saturated material, in the form of rectangular plates with dimensions of 30 * 90 mm and a thickness of 4 mm. The results of physical and mathematical modeling are reflected in the form of profiles of changes in moisture content and temperature along the cross section of the material during saturation. It is established that the active process of saturation of the veneer with moisture under changing medium pressure is observed during the first 15 minutes, and by this time the temperature in the center of the material exceeds 120 ° C. The results of mathematical modeling were obtained using the Visual Basic for Applications software environment. The discrepancy between the calculated and experimental data does not exceed 15%. The developed mathematical model of the process makes it possible, when the capacities of sources (steam generator) and drains (condenser and vacuum pump) vary, to recommend the modes of conducting the technological process or to select the capacities of the steam generator and pump in accordance with the required law of pressure change in the technological process. For physical modeling of the investigated process in the processing of wood raw materials, an experimental setup was created, on which experimental data confirming the adequacy of the developed model were obtained.

Phase-change materials for storing heat extracted from heat pump condensers

This study aims to investigate the storage of heat from a heat pump's condenser in a well-insulated cylindrical tank filled with spherical capsules containing a phase-change material (PCM). Using a detailed physical model and the enthalpic method, the system's operation and phase change phenomena are simulated. The impact of various operational parameters, such as condenser power, water flow rate, storage volume, and PCM type, is examined. The results reveal that increasing condenser power significantly reduces the PCM loading time, achieving a 66 % reduction within the 5 kW to 15 kW power range. Additionally, decreasing the water flow rate enhances storage efficiency by 15 % when the flow rate drops from 2.3 m3/h to 1 m3/h. The use of a PCM with a melting temperature of 44 °C is deemed more suitable for the system compared to other options.

Application of deep learning modelling of the optimal operation conditions of auxiliary equipment of combined cycle gas turbine power station

Reasonable condition adjustment of the auxiliary machinery can optimize the operation performance of the Combined Cycle Gas Turbine (CCGT) power station. In this paper an optimization method for the operation control of the auxiliary equipment based on deep learning is proposed and applied to an F-class gas turbine generation unit. A database of the optimal operating conditions is established to achieve the best economic benefit based on the analysis of two years of historical operation data. The control optimization models are built using the machine learning algorithms including the Multi-Layer Perceptron (MLP), Supporting Vector Machine (SVM), Gaussian process regression and linear regression methods and their accuracy has been compared. The input parameters of these models consist of the load rate, the heating output and the ambient temperature, with the output parameters including the electrical currents for the mechanical draft cooling tower, the high pressure feed pump, the medium pressure feed pump and the condensate pump. The MLP model is designed with different network hidden layer structures and provides the highest calculation accuracy with the least average error of 1.82 %. Different training data sizes are compared and the optimal control trajectory is analyzed. The result can provide useful references for the optimization of auxiliary equipment operations.

Construction of the Dynamic Model and Control System for the Canadian Supercritical Water–Cooled Reactor Power Plant

Canada has proposed the supercritical water–cooled reactor (SCWR) concept as one of the Generation IV nuclear reactors. In the SCWR power plant, the supercritical water is heated in the reactor and then flows to the turbine directly. Therefore, knowledge of the dynamic behaviors of the system is necessary for the stable operation of the power plant. There is still a lack of study on the control system for the proposed SCWR power plant. In this study, a dynamic model for the entire SCWR power plant is constructed that includes the reactor, turbine, condenser, and feedwater pump. Based on the model, the open-loop characteristics of the system when subjected to perturbations in the inputs are analyzed. Subsequently, a feedback control strategy is adopted to regulate the outputs of the system when there are disturbances. The evaluation of the performance of the control system shows that the proposed control system can return the plant back to the operating conditions effectively.

Experimental and numerical study of a condensation-driven dilution refrigerator

Dilution refrigerators are widely used in the fields of condensed-matter physics and quantum technology. For small cooling power applications, condensation-driven dilution refrigerator utilizes a condensation pump to achieve 3He cryogenic circulation and has advantages of compact structure, small 3He usage, and convenient operation. Related published research mainly focused on the overall system performances, and in-depth thermodynamics and fluid dynamics analyses are lacking. In this paper, a condensation-driven dilution refrigerator was experimentally studied and corresponding numerical simulations were performed. The results of experiments and simulations were compared and analyzed. In the experiments, lowest no-load temperature was 84.4 mK. The experimental cooling power was 1.91 μW @100 mK with a still heating power of 280 μW and the corresponding COP and second-law efficiency of the dilution cold cycle at 100 mK reached 0.0068 and 2.4% with the high temperature of 452 mK, respectively. The experiments also revealed that the charged mixture amount had a certain influence on the performance. With the help of simulations, the heat leak to the mixing chamber was estimated and certain intrinsic features of the cycle were enlightened. The heat leak and Kapitza resistance in the mixing chamber are possibly the main reasons for the differences between experimental and simulation results. Extended study based on the simulation also showed how flowrate variation changed the liquid column height difference and how the requirement of gas circulation and liquefaction set the limit on the minimum still temperature.

Novel configuration of dual-temperature condensation and dual-temperature evaporation high-temperature heat pump system: Carbon footprint, energy consumption, and financial assessment

To achieve the goal of carbon neutrality for the application of industrial heating by recovery waste heat, the concept of dual-temperature condensation and dual-temperature evaporation is proposed for the high-temperature heat pump (HTHP) by introducing the techniques of ejector and two-stage compression. The energy, exergy, emission, and economic models are developed and optimized for the two new proposed systems. Then, the energy consumption, CO2 emissions and cost (LCC) during the whole life cycle are compared with five existing heat pumps and four traditional boilers. The highest coefficient of performance (COP) of heat pump (HP) can be got when intermediate water temperature on the heat sink side is optimum. The new proposed systems have better performances than the other five HTHPs. During the rated working condition, discharge temperature decreases by the use of dual-temperature condensation and dual-temperature evaporation HP with an ejector (Ej-DCDE). The optimal COP of Ej-DCDE-2 is 4.25, which is 11.55% and 1.43% higher than dual-temperature condensation and single-temperature evaporation HP and Ej-DCDE-1, respectively. The exergy destruction of Ej-DCDE-2 is reduced by 27.88% compared with basic heat pump (Base). Moreover, Ej-DCDE-2 has the lowest primary energy consumption of 14.62 ktoe, 22.19% and 25.09% lower than Base and oil-fired boiler during the total working period, respectively. In general, HTHPs have lower carbon dioxide, gaseous and particular pollutant emissions compared with boilers, especially Ej-DCDE-2. Finally, Ej-DCDE-2 has the minimum LCC, which is 14.67% and 11.75% less than Base and coal-fired boiler. Ej-DCDE-2 shows the most potential advantages of all the heating solutions and is recommended to replace traditional boilers for industrial heating.

Investigation on stall characteristics of marine centrifugal pump considering transition effect

Marine centrifugal pumps are used as boiler feed pumps and condensate pumps in ocean engineering. Centrifugal pump stall is a transient flow structure, which may disrupt the uniformity of the flow field and have destructive effects on the pump. Centrifugal pump simulations are usually limited to the application of turbulence, ignoring the transition characteristics of the blade boundary layer. Aiming at the transient characteristics of centrifugal pump stall vortex, the calculation strategy considering the transition effect is established. This strategy determines the near-wall mesh based on the transition flow parameters and is applied to calculate the centrifugal pump stall for the first time. It is found that at deep stall conditions, the number of stall cells calculated by the transition model increases, while the stall frequency decreases. The microscopic flow structure calculated by the transition model and its relationship with the hump of the centrifugal pump head is obtained. The laminar separation bubbles near the blade leading edge will increase as the flow rate decreases, causing an increase in the friction loss on the blade surface, which lead to a hump in the pump head characteristics. The dynamic mode decomposition (DMD) method is used to extract the characteristic frequencies and corresponding modes of the 0.2Qd condition. In the high-order mode of the stall flow field with transition, a low-pressure zone formed at the head of the blade has a tendency to fall off from the wall, which shows the high-order motion characteristics of the stall vortex. The results could guide centrifugal pump design and operation.

Numerical analysis of the influence of the non-uniform inflow induced by streamwise vortices on the cavitating flow around hydrofoil

Cavitation under non-uniform inflows is a commonly encountered situation in engineering applications. In the present study, the effects of the streamwise vortices on cavitating flows are investigated separately, which are extracted from the non-uniform inflow of some non-straight inlet casings of condensate pumps. The unsteady cavitating flow around NACA66 hydrofoils with Vortex Generators (VGs) installed upstream (VGs-Up and VGs-Down), as well as a single NACA66 without VGs (benchmark case), is numerically analyzed. The Large Eddy Simulation (LES) coupled with a homogeneous cavitation model is employed to capture complex cavitating flow structures. The influences of the streamwise vortices induced by the vortex generators (SV_VGs) on partial cavitation are analyzed by comparing the three cases. The results show that the SV_VGs tend to intensify the cavitation degree around the foil for both VGs-Up and VGs-Down, and they will generate a noticeable concave trace on the cavities. However, the different positions of the SV_VGs appear to have little influence on pressure distribution, as well as lift and drag forces change in cavitating flow. During the whole cavity shedding cycle, three types of interaction mechanisms between SV_VGs and cavitating flow field are analyzed: 1) SV_VGs-Sheet Cavity interaction; 2) SV_VGs-Vortex interaction; 3) SV_VGs-Cloud Cavity interaction. As for the vorticity field, influenced by the SV_VGs, the vorticity transport process assumes 3D characteristics. Further analysis of the mean cavitating flow field reveals that the streamwise vortices in the free stream mainly contribute to the first half of the sheet cavities, whereas having little impact on the second half of the cloud cavities due to the rapid attenuation of their vorticity strength. In addition, the upstream streamwise vortices in the free stream have little influence on the boundary layers in non-cavitating flow, even for the VGs-Down with vertical distance δ = 0.

Pemakaian Metode ASME PTC 4.1 Pada Evaluasi Performa (Efisiensi) Boiler Pulverized Firing di Pembangkit Listrik Tenaga Uap (PLTU)

The rankine cycle is widely used for thermal generators that use steam as a turbine driver in power generation plant. There are 4 main equipments in power plant with rankine cycle system that is: Boiler, Turbine, Condenser and Feed pump. Boiler is a tool to heat water up to steam with high temperature and pressure. Then steam goes into the turbine to drive the generator. The steam coming out of the turbine is cooled inside the condenser to be changed into liquid again. Condenser coolers are widely used in steam power plants is sea water, but some are using river water. Water becomes a working fluid in the rankine cycle and undergoes closed cycle (close loop cycle) meaning continuously water at the end of the cycle process re-entry to the early process cycle. There are several methods to calculate boiler efficiency by direct method (input method) and heat loss method (energy balanced method). The calculation by the direct method by dividing the resulting steam energy divided by the fuel energy coming into the boiler. While the calculation of boiler efficiency with heat loss method is the fuel energy that enter the boiler reduced by losses that occur in the boiler. ASME PTC 4.1 method can be used to calculate boiler efficiency at large boiler capacity, so PTC 4.1 method is often used to evaluate boiler in power plant. The ASME PTC 4.1 method is recommended for the calculation of heat-loss methods in the boiler and is often performed to review the efficiency according to the design as a benchmark.

Numerical investigation of a condensation-driven dilution refrigerator

The dilution refrigerator is the most popular subkelvin refrigerator and important for research fields such as condensed matter physics, astronomical observation, and quantum computing. For applications requiring small cooling powers as well as small footprints, the cold-cycle dilution refrigerators without ambient mechanical pumps and complex connecting gas circuits have become a new research frontier. In this paper, a condensation-driven dilution refrigerator, as a kind of cold-cycle dilution refrigerator, is studied numerically. A comprehensive model covering the thermodynamics, heat transfer and fluid dynamics is established and systematical simulations are carried out to analyze the system performance and the influence of key operating parameters. Through simulations, the T-S and P-T figures of the cold cycle at typical operating conditions are given, and the thermodynamic processes and irreversibility are analyzed. Typically, a COP of 0.025 with the corresponding thermodynamic second-law efficiency of 7.5% can be obtained at 100 mK with the still temperature being 450 mK and the condensation pump temperature being 400 mK. The results reveal the mechanism of the condensation-driven dilution refrigerators and provide useful guidance to the design and operation of experimental setup.

A dual-mode system for water purification and cooling using a thermal desalination technique coupled to a heat pump unit

Humidification-dehumidification is one of the most suitable small-scale desalination methods based on air humidification and condensation. The major energy-consuming components for a humidification-dehumidification process are a heat source for the humidifier and a cooling source for the dehumidifier. To improve the performance of these processes, the fluids were preheated using different energy sources or waste heat. In recent years, preheating air or saline water using heat from a heat pump's condenser has been explored to improve the system's performance and to produce cooling and desalination simultaneously. However, separate heat exchangers and additional solar collectors/heaters were used to preheat the second fluid. In this work, the air-cooled condenser of a heat pump has been replaced by an evaporative condenser and used as a humidifier. This configuration has been scarcely explored in the literature and requires a single heat exchanger to preheat the fluids. On the other hand, the heat pump's evaporator was used to produce low-temperature coolant, circulated through a cooling coil where the humid air from the evaporative condenser is cooled and dehumidified to produce fresh water and cooling simultaneously. This modification ensures reduced space requirement and better system performance than other heat pumps coupled to humidification-dehumidification systems for simultaneous cooling and desalination. Also, the present system operates flexibly to switch between desalination and cooling mode (mode-1) to cooling mode (mode-2). Towards this, a mathematical model of the system has been developed and analyzed under various operating conditions. The system's performance, which includes desalination yield, cooling output, gained output ratio, and coefficient of performance under each mode of operation, is studied for different ambient conditions and evaporator temperatures. The maximum desalination yield, cooling output, gained output ratio, and coefficient of performance of mode-1 are 4.55 LPH, 0.82 kWth, 3.79, and 0.75, respectively. The maximum cooling output and COP of mode-2 are 3.79 kWth and 3.82, respectively. The exergy efficiencies for mode-1 and mode-2 are 32.7 % and 29.7 %, respectively.

Experimental analysis of condensation-pump dilution refrigerators

<sec>Subkelvin refrigeration is necessary for many frontier research fields such as condensed-matter physics, astronomical observation, and quantum computing. Dilution refrigeration utilizes the entropy increase of <sup>3</sup>He atoms when they flow from the concentrated phase to dilute phase to provide cooling, and has the advantages of continuous operation, large cooling power and no electromagnetic interference. It is the most widely used method among subkelvin refrigeration at present. For research scenarios requiring small cooling powers, the condensation-pump dilution refrigerator utilizes a condensation pump to achieve cold cycle of <sup>3</sup>He, with no need of complex ambient pump systems or gas circuits, and has become a new research topic because of its compact structure, convenient operation and low cost.</sec><sec>A condensation-pump dilution refrigerator is built and investigated in this work. The refrigerator consists of a mixing chamber, a continuous tube-in-tube heat exchanger, a still, and a condensation pump, and it is precooled by a GM-type pulse tube cryocooler below 4 K and an adsorption refrigerator below 400 mK. The <sup>3</sup>He evaporates from the still, condenses in the condensation pump and provides cooling in the mixing chamber after being precooled in the heat exchanger.</sec><sec>By means of the multi-temperature measuring system, the cold cycle of the dilution refrigerator can be summarized as three stages: precooling by the adsorption refrigerator, cycle start-up, and continuous dilution cooling. The operating characteristics of the system are analyzed. The experiments showed that the lowest no-load temperature reached 108 mK when the condenser temperature was 378 mK. Meanwhile, the temperature oscillation appeared, and the possible reasons are analyzed. In the future, the system performance will be improved by 1) adjusting the spiral mode and position of the continuous tube-in-tube heat exchanger and 2) increasing the heat transfer area between the cold plate and the fluid in the mixing chamber to reduce the fluid-solid temperature difference.</sec><sec>The refrigerator introduced in this work can easily expand many existing cryogenic platforms working at higher temperatures, and effectively support developments of high-end equipment.</sec>

A Study on Energy Saving of Condensate Pump Speed Regulation improvement for CPR1000 Nuclear Power Unit

To reduce the energy consumption of nuclear power plants, this paper studies the control mode of changing the condensate pump frequency to variable speed regulation, using permanent magnet flexible transmission technology to change the speed of the condensate pump, and the control strategy of deaerator water level and the outlet pressure of condensate pump is redesigned to achieve the purpose of energy saving. Through the study of control strategy, process design analysis, theoretical calculation, and process simulation of the full-range simulator, the feasibility of the proposed method is confirmed, which provides an important reference for the improvement of energy saving and speed regulation of auxiliary machines in nuclear power plants.

Two-Dimensional Nonlinear Thouless Pumping of Matter Waves.

We consider theoretically the nonlinear quantized Thouless pumping of a Bose-Einstein condensate loaded in two-dimensional dynamical optical lattices. We encountered three different scenarios of the pumping: a quasilinear one occurring for gradually dispersing wave packets, transport carried by a single two-dimensional soliton, and a multisoliton regime when the initial wave packet splits into several solitons. The scenario to be realized depends on the number of atoms in the initial wave packet and on the strength of the two-body interactions. The magnitude and direction of the displacement of a wave packet are determined by Chern numbers of the populated energy bands and by the interband transitions induced by two-body interactions. As a case example we explore a separable potential created by optical lattices whose constitutive sublattices undergo relative motion in the orthogonal directions. For such potentials, obeying parity-time symmetry, fractional Chern numbers, computed over half period of the evolution, acquire relevance. We focus mainly on solitonic scenarios, showing that one-soliton pumping occurs at relatively small as well as at sufficiently large amplitudes of the initial wave packet, while at intermediate amplitudes the transport is multisolitonic. We also describe peculiarities of the pumping characterized by two different commensurate periods of the modulations of the lattices in the orthogonal directions.

Evaluation of a modernization project of the main condensate scheme at CHP-10 power unit No. 5 using its customized simulation model

We investigate the effect of modernizing the main condensate scheme applied at the power unit No.5, CHP-10 of Baikal Energy Company LLC, on its energy and economic efficiency using a customized simulation model. Simulation modelling was carried out in the Machine Program Building System software environment. The constructed model was verified using the results of measuring control parameters in several operating modes according to a three-stage procedure of verifying the mathematical models of complex thermal power units. We propose an original approach to modernizing the main condensate thermal scheme at the power unit under study in order to reduce the specific fuel consumption for balance-of-plant needs. The idea was to expand the main condensate scheme by including an additional sealing pump to the feedwater electric pumps of the 1Кs-20-110 unit in order to avoid the incorrect selection of condensate pumps. The study showed that the redistribution of the main condensate flow between the existing condensate pumps and the proposed 1Ks-20-110 sealing pump leads to a reduction in the specific fuel consumption for the electric energy generation to 0.32 g of fuel per kWh across the range of electrical loads from 137 to 150 mW. As a result, the net efficiency of the power unit can be raised by 0.03%. It should be noted that the proposed modernization project may reduce the consumption of electricity for balance-of-plant needs when the feedwater electric pump is switched to the standby mode during an emergency shutdown of the power unit. Based on the performed energy and economic calculations, energy savings for the period of 2019 comprise 82,653 kWh, while the total annual savings are estimated at 78,030 rubles. Thus, the conducted research demonstrates the high efficiency of applying simulation modelling in the study and optimization of existing thermal power plants.

Методика оценки влияния эксплуатационных параметров на работу турбопитательного насоса

Background. Turbine feed pumps (TFP) are one of the main consumers of thermal energy for in-house needs of thermal power plants and nuclear power plants. Currently, much attention is paid to improve the efficiency of operation of turbine feed pumps. Thus, it is necessary to assess the impact of operational parameters. The problem is that it is necessary to process a large array of data. The solution to the problem is the development of a methodology that allows quantitative and qualitative assessment of operational parameters. Materials and methods. As initial data, the authors have used the data of 20 thermodynamic and hydraulic parameters recorded during the industrial operation of the TFP equipment and the equations of thermal balances to find the key performance indicators of the TFP. A complex of multidimensional statistical methods is used for data processing, i.e cluster and factor analysis in the Statistica software package. Results. A methodology to assess the impact of parameters on the operation efficiency of the TFP has been developed. The cluster analysis method is used to diagnose and classify the parameters under study. By the method of factor analysis, several parameters have been identified: feed water flow in the pipeline behind the TFP, differential pressure of water of the TFP, condensate flow in the pipeline behind the TFP condensate pumps, pressure drop of circulating water before and after the TFP condenser, condensate temperature of the drive turbine. The analysis of the results has showed that the identified parameters are the main components of the useful power of the turbine feed pump and the criteria for the efficiency of the TFP. Conclusions. The proposed methodology makes it possible to carry out a quantitative and qualitative assessment of operational parameters, solve the problem of processing large amounts of information, reduce the time and complexity of calculations. The results obtained are based on the developed methodology and can be used to design a statistical model using neural network technologies. This methodology can be chosen to evaluate the operation of technological systems and subsystems at thermal power plants and nuclear power plants.

Prognostics and Health Management for Maintenance-Dependent Processes

Industrial components and systems undergo degradation in process operations. Prognostics and health management (PHM) is a process to assess and predict health conditions of components and can be applied to condition-based monitoring and maintenance. PHM is commonly utilized to analyze the health condition of a single lifecycle until failure. When maintenance occurs, degradation can be removed, and the PHM model can be restarted with new parameters related to the expected postmaintenance conditions. Maintenance actions, mostly imperfect repairs, may not entirely reset the condition to as good as new, and further degradation may occur at a higher rate. Maintenance repairs should be considered in prognostic models to predict component health more accurately. Furthermore, processes typically have more than one component that degrade and influence process measurements. The dependence of process measurements to multiple fault modes and related degradation can make individual component health monitoring complex. Commonly, faults and their related effects on process parameters must be isolated. In these cases, the diagnostics and prognostics framework should handle unsynchronized failure and maintenance reinitialization of different components for multiple fault processes. This research paper presents the Maintenance-Dependent Monitoring and Prognostics Model (MDMPM) to detect anomalies, decouple faults for different components, and predict future health conditions to calculate remaining useful life (RUL). The model is demonstrated with semisimulated nuclear power plant (NPP) data, with simultaneous condenser pump degradation and condenser tube fouling. The MDMPM shows a reliable prediction of RULs of NPP maintenance-dependent processes with interacting component degradation modes.

Cavitation Characteristics during Startup Process of a Condensate Pump with Splitter Blades

The present study aims to describe characteristics of cavitation during the startup process of a condensate pump. The pump is featured by an impeller equipped with five splitter blades. A computational fluid dynamics (CFD) work was conducted to plumb the evolution of cavitation in the pump. Effect of the volumetric flow rate on instantaneous cavitation patterns as the rotational speed of the pump increased was analyzed. The results show that high resistance to cavitation of the pump depends greatly on large area of the impeller eye, which is related to the deployment of the splitter blades. The splitter blades are insignificantly affected by cavitation. During the startup process, both the pump head and the pump efficiency vary drastically, which is insensitive to the flow rate. At a net positive suction head (NPSH) of 2.0 m, high flow rates are responsible for intensified cavitation. High volume fraction of cavitation arises near the inlet of long blades. As the rotational speed increases, the evolution of cavitation is featured by intermittency and diversified cavity patterns. Furthermore, the sum of the volume fraction of cavitation fluctuates with continuously increasing rotational speed.