Circulation Pump Research Articles

Investigation of nuclear reactor core thermal-hydraulic characteristics after partial loss of flow accident

In normal operation conditions of nuclear power plants, the distribution of primary coolant between fuel channels would be considered almost uniform. When different number of Reactor Circulation Pumps (RCPs) are switched off, known as an abnormal condition, this uniform distribution is disturbed and different conditions occur for each channel depending on its position in the core. In this research, the normal and abnormal condition (with one or two tripped RCPs) for a VVER-1000/446 is investigated. For evaluation of the core neutronic calculations and thermal power distribution, USNRC’s PARCS system code is employed. Then a thermal-hydraulics module was developed for performing the T/H calculation of the core zone. The input velocity of each channel in abnormal condition was calculated based on developed CFD model in downcomer and lower plenum of Reactor Pressure Vessel (RPV) by ANSYS-CFX. The results show that, in normal operation, the hot channel is related to the central fuel assembly of the reactor core with the highest relative power equal to 1.29 and total power of 23.74 MW. In this case, the minimum inlet velocity, the maximum coolant outlet velocity, and the maximum fuel temperature are 5.6 (m/s), 330.96 (°C), and 1345.8 (°C), respectively. In the cases of operation with one and two tripped RCPs, the hot channel is related to the fuel assemblies with the lowest inlet velocities. The lowest velocities are 0.32 m/s, 0.24 m/s, and 0.22 m/s respectively for the condition with one tripped pump, two tripped pumps placed oppositely, and two tripped pumps placed contiguously. The hot channel numbers in these cases are 158, 102, and 90, respectively. In these channel, the condition of outlet flow would be superheated, but the fuel temperature (1006.3, 1050.9, and 987.9) do not reach the maximum allowable margin. The study confirms the necessity of the coolant distribution consideration in OLCs as well as events that may disturb the symmetry of the coolant flow. It also showed that the lateral fuel assemblies are more at risk in this situation because of a significant reduction in coolant flow. Likewise, the investigations proved the safe continuation of the operation in PLOFA conditions with the preventive algorithm of the emergency protection system and without any need for immediate mitigation actions or operator intervention.

Experimental investigation on characteristics of Multiple-Loops coupled natural circulation system

The passive safety design is advantageous because it simplifies the system and brings higher safety features. Passive residual heat removal system (PRHRS) is one of the most important passive safety systems, which is designed to cool down the reactor during accidental conditions. For floating nuclear power platforms, seawater could be utilized as the final heat sink of PRHRS through multiple-loops coupled natural circulation.To study the operating characteristics and thermal hydraulic behavior of multiple-loops coupled natural circulation system, the Natural Circulation Mechanism Experimental System (NCMES) has been constructed. The station blackout accident (SBO) scenario is simulated in NCMES, which leads to the stopping of circulation pump and operation of PRHRS. Based on the experimental data, an analysis was carried out using the thermal hydraulic system code RELAP5, aiming to validate applicability and accuracy, as well as predict the operating characteristics of the experiment facility. The comprehensive analysis of experimental and calculated results shows that when it comes to the SBO scenario, the releasing residual heat and sensible heat of fluid can be removed to seawater through triple-loops coupled natural circulation; the calculated results fit the experimental data quite well and the RELAP5 code is applicable to predict operating characteristics of multiple-loops coupled natural circulation and PRHRS. As a result of self-adaptive characteristic of natural circulation, with the heating power decreasing, the response rate of natural circulation flow rate and fluid temperature is slow.

Peningkatan Produktivitas Tanaman Hidroponik Menggunakan Tenaga Surya

Electricity is highly essential in hydroponic agriculture. To enhance the productivity of hydroponic plants, LED grow lights are used to provide illumination during the nighttime. This electrical energy is utilized for the circulation pump of the plant's nutrients and to power the LED grow lights. To address this, the approach taken is to harness solar energy and convert it into electrical energy. This conversion of solar energy into electrical energy is known as photovoltaic, which involves the use of solar cells as the device. The hydroponic system employed in this research is the Deep Flow Technique (DFT) hydroponic system. The circulation pump operates every hour for 10 minutes, while the LED grow lights are turned on from 20:00 to 24:00. On average, the plants grow approximately 0.8 to 1.5 cm per day, and the leaves grow around 1 to 2 strands per day. The total daily electricity requirement for the circulation pump amounts to 36.4 watt-hours.

Numerical Simulation of the Welding Process during the Main Circulation Pump Impeller Repair

Paper presents a numerical simulation of the main circulation pump impeller damaged parts repair/replacement welding process, for the prediction of welding-induced residual stresses. 3D numerical model creation of the impeller flange and central hub welded joints. Thermal and stress-strain analysis of assessed parts using the finite element method. Calculation of equivalent residual stresses in the area of examined welded joints. Applicability of results in further impeller integrity analyzes. The results confirmed the suitability of the chosen welding procedure and technology.

Modernization of electrical equipment as a way of reducing the risks of emergency situations at nuclear power plants

An analysis of major accidents in the electric power and coal industry was carried out. It is shown that for many types of technological equipment, the cause of failure was the unsatisfactory performance of the seals. It is shown that in two known nuclear accidents, the cause is the failure of coolant supply systems. Moreover, it had catastrophic consequences at the Fukushima nuclear power plant. The direct cause of the cessation of cooling of the reactors was the ingress of water into the electric motors of the circulation pumps. Most electric drives of nuclear power plants are synchronous electric motors. Turbogenerators are also synchronous four-pole electric machines of great value, which determines the expediency of increasing their reliability and service life. The solution to this problem is possible with the help of magnetic fluid sealing complexes (MFCs). To compare the level of man-made safety when using MFCs and traditional sealing systems, an improved method of risk assessment is proposed, developed at the expense of a systematic analysis of sealing complexes of equipment of hazardous industries for synchronous electric motors of the SDN type under different modes of operation, power and revolutions of the rotating shaft. The man-made risk assessment shows that the level of man-made danger is reduced by 1.5 to 4 times when sealants are introduced.

Modeling, control and analysis of a novel energy-saving oriented fuel cell anode system

Fuel cell hydrogen supply sub-system needs to provide sufficient mass flow and pressure of hydrogen to meet the working demand of the stack. The hydrogen circulation pump is often used, but causes additional parasitic power of fuel cell system. In this study, a new structure of hydrogen circulation pump is proposed to reduce the parasitic power by using the pressure potential energy of hydrogen flow. The hydrogen feeding system model is established based on the solution of differential equation of state of ideal gas, mass and energy balance. Then, considering the hydrogen intake pressure and the hydrogen excess ratio of the system, a reasonable control strategy is proposed for accurate control. Simulation results show that under the fuel cell work condition and the fuel cell vehicle operation condition, pressure difference between anode and cathode and the hydrogen excess ratio can be regulated to the conditions required by the stack, and the excess ratio error and pressure difference error between anode and cathode is 3.82e-3 and 4.52e-4 Bar, respectively. The parasitic power consumption of the circulating pump is effectively reduced about two-thirds under the fuel cell vehicle operation condition. Then, the effects of anode hydrogen pressure drop, hydrogen inlet pressure and entrainment ratio of ejector on the system are studied. Reducing the anode pressure drop, increasing the ejector entrainment ratio while reducing the hydrogen inlet pressure at low power and increasing it at high power are conducive to energy-saving of the system.

Enhancing the Energy Efficiency—COP of the Heat Pump Heating System by Energy Optimization and a Case Study

This article deals with the degrees of freedom and possible optimums, specifically with the energy optimums of the heat pump heating system. The authors developed an multi objective optimization procedure that allows for the determination of the optimal motor power for the circulation and well pumps in order to achieve the maximum COP. Upon selecting the type and size of the water-to-water heat pump, based on the heating demand of the buildings, the proper power of the circulation and well pumps must be determined. There are several procedures used for determining the pump’s power. However, none of those methods ensures the optimum power, i.e., the maximum coefficient of performance, COP of the heating system. In this study, a multi objective analytical-numerical dimensioning procedure was developed for the determination of the optimal mass flow rate of warm and well water. Based on the flow rate values, the optimum power of the circulation and well pumps can be calculated. Due to the wide scope of the topic, the application of the optimization procedure is presented in a case study, but only for determining the optimum power of the circulation pump. The validity of the procedure was confirmed by measurements. The results obtained with the optimization showed that through the energy optimization of the circulation pump power, the COP of the system increased by 5.34%.

THERMAL BEHAVIOR OF FLUIDS IN ELECTROMAGNETIC INDUCTION

In this study, the thermal behavior of different fluids in electromagnetic induction heating was investigated. Induction coil, heat exchanger and control circuit designs were made for the research. An experimental setup was created by using a temperature gauge, tachometer, DC motor and circulation pump. The thermal behavior of 650 ml of boron oil, pure water, olive oil, sunflower oil, motor oil and boron – pure water composite fluids after their circulation at 700 rpm and 92 minutes from the experimental setup was investigated. The heat exchanger surface temperature, circulation pipe temperature, beaker temperature and ambient temperature were recorded. The heat exchanger surface temperature, circulation pipe temperature, beaker temperature and ambient temperature were recorded. The specific heat capacity values of the same fluids were also calculated. At the end of the research, it was observed that the temperature of 92 minutes under the same electromagnetic induction and ambient conditions showed values between 79 °C and 95 °C. It has been determined that the most efficient fluid is the engine oil, which has a heating value of 37 °C at the 2nd minute, 85 °C at the 42nd minute and 95 °C at the 92nd minute. It was observed that boron oil, olive oil, sunflower oil, boron – pure water composite mixture and pure water followed, respectively. It has been observed that the specific heat capacity values are inversely proportional to the temperature increase of the fluids.

Influence of Surface Machining on Development of Stress Corrosion Cracking of Distribution Wheels of Main Circulation Pump in Nuclear Power Plants

The present work deals with the causes of the damage to the distribution wheel of the main circulation pump of the nuclear power plant. During the solution of the problem, a significant influence of the final machining on the formation of cracks was found. Coarse surface machining can cause strain-induced martensite on the distribution wheel surface. Small pitting, which was observed on the surface of the distribution wheel, can be caused by the presence of martensite with less corrosion resistance. Thermal stress and residual stress after coarse final surface machining caused the growth of the cracks which initiated from the pitting.

Effect of different roll-forming flower patterns on coiled tubing ovality and pressure performance

The pressure applied by the drilling fluid circulation pumps into Coiled Tubing (CT) compensates for the effects of fluid friction and force applied to the downhole motors. The higher the pressure, the greater the power of the well operation. The critical point of the cross-section of CT is on the earth's surface, where the highest internal and lowest external pressure are applied to it. In this paper, the compressive tolerance value of CT is investigated in relation to its ovality. This ovality can be inherent and created during the construction of the tube. 4 different flower patterns can be used for making CT. This paper aims to roll forming CT without a sizing step so that it preserves its mechanical performance against incoming forces. The geometry-based form definition method calculations have been used to determine the forming path of the strip, and this is the basis for the design of the forming rollers in each stage, finally, according to the similarities in the forming stages, 45 rollers have been designed for simulation. Therefore, assuming that the sizing step is not used in tube roll forming, the effect of roll forming flower patterns on the ovality of the final product of 1 ½ inch CT-70 and its effect on the internal and external pressure tolerance of the tube is investigated and Results of dimensional analysis, a tensile test of a new QT-70, 1 ½ inch tube as a sample and the geometry-based form definition method results are considered as input for the simulation of all four methods and the finite element method was used to simulate tube construction with different flower pattern methods, and its results were used in the geometry of the final product, in CT pressure tolerance analysis. The results show that the behavior of the tube made by the reverse bending flower pattern method shows better tolerance against internal and external pressure so this behavior is related to the ratio of internal to external pressure tolerance in the tube. With the flower pattern method, the reverse bending is approximately 1.08–1.85 times compared to the double-radii pattern and 1.13 to 2.27 times, and 1.18 to 3.21 times compared to the edge flower pattern and circular flower patterns, respectively.

ATHENA Main Heat Exchanger Conceptual Design and Thermal-Hydraulic Assessment With RELAP5 Code

Abstract Among the envisaged experimental infrastructures supporting ALFRED reactor development, Fostering Alfred Construction consortium identified ATHENA as one of the facilities to address the pool thermal-hydraulic challenges and demonstrate the feasibility of the revised ALFRED configuration, along with the thermal-hydraulic performances of its main components. ATHENA is a large pool-type lead-cooled multipurpose experimental facility featuring a large size vessel (3.2 m diameter, 10 m in height), conceived to host almost 800 tons of lead to test ALFRED relevant scaled components. The test section to be installed in the main vessel includes an electrically heated core simulator (CS), made of 7 FAs, which delivers to the primary coolant a nominal thermal power of 2210 kW, a main coolant pump for lead circulation, and a countercurrent shell and tubes main heat exchanger, which tube bundle is fed by pressurized water by a dedicated secondary circuit. A preliminary analytical calculation has been performed to identify the most suitable configuration for the ATHENA heat exchanger, as well as to achieve a preliminary sizing of the component. The final layout foresees a bundle of 91 bayonet tubes, arranged in a cylindrical geometry, having an active length of 3000 mm and adopting an external double wall tube with a pressurized helium gap. A numerical model of the heat exchanger has been developed using the thermal-hydraulic system code RELAP5/Mod3.3, and a numerical sensitivity analysis on the geometrical and operating parameters has been carried out to verify the performances of the component.

Thermal-Hydraulic Characterization and Numerical Modeling with RELAP5 Code of ATHENA Secondary Loop

Among the envisaged experimental infrastructures supporting Advanced Lead Fast Reactor European Demonstrator (ALFRED) reactor development, the FALCON [Fostering ALfred CONstruction] consortium identified the Advanced Thermo-Hydraulics Experiment for Nuclear Application (ATHENA) as one of the facilities to address the pool of thermal-hydraulic challenges and demonstrate the feasibility of the revised ALFRED configuration, along with the thermal-hydraulic performances of its main components. ATHENA is a large pool-type lead-cooled multipurpose experimental facility featuring a large-sized vessel (3.2-m diameter and 10-m height), conceived to host almost 800 tons of lead to test ALFRED-relevant scaled components. The test section to be installed in the main vessel includes an electrically heated core simulator, made of seven fuel assemblies, which delivers to the primary coolant a nominal thermal power of 2210 kW; a main coolant pump for lead circulation; and a countercurrent shell-and-tube main heat exchanger, of which the tube bundle is fed by pressurized water by a dedicated secondary circuit. This work presents the numerical model of ATHENA along with thermal-hydraulic characterization of the facility using the system code RELAP5/Mod3.3, properly modified to include the thermophysical properties of heavy liquid metals. After the characterization of the steady state representative of the Stage 3 foreseen for the ALFRED staged approach, results of a numerical sensitivity analysis aimed at defining the most suitable procedure for the shutdown transient of the facility are presented.

Modelling and performance evaluation of a direct steam generation solar power system coupled with steam accumulator to meet electricity demands for a hospital under typical climate conditions in Libya

This study aims to build a dynamic model of a direct steam generation (DSG) solar power system coupled with a steam accumulator to meet electricity demands for a hospital under transient environmental conditions in Libya. The main components of the system are DSG parabolic trough collectors, a steam accumulator, a turbine, a condenser and a circulation pump. The system is modelled via using Simulink\\Simscape software blocks with integrated MATLAB functions to run a dynamic simulation. As the simulation tool reflects the transient operation of the components, advanced control strategies were applied to the model. Using the proportional integral controller (PI controller), safe operation of the system is secured by pump flow rate control, safe turbine operation is provided by pressure control and power output is matched with the demand by using a throttle valve control. 1584 m2 solar collector area and 160 m3 total volume of pressurized steam tank are used in the simulation considering the electricity demand of the hospital and solar radiation in the location. The produced work output was controlled to match the demand profile of the hospital, which needs 200 kW in the peak period and 50 kW at the night. The designed system shows a maximum thermal efficiency of 23.5% for the operation condition.

Simulation of the Troitsk District Power Plant 660-MW Power Unit Boiler Startup Modes without Using the Startup Circulation Pump or Estimation of the Boiler Lower and Upper Radiant Parts’ Temperature Operating Conditions

Simulation of the Troitsk District Power Plant 660-MW Power Unit Boiler Startup Modes without Using the Startup Circulation Pump or Estimation of the Boiler Lower and Upper Radiant Parts’ Temperature Operating Conditions

Thermal-Hydraulic Investigation of Steady-State Single-Phase Natural Circulation of an Integral PWR-Type SMR Test Rig (iPSTR)

The main aim of the natural circulation of the primary coolant in a nuclear reactor is to reject heat from the reactor core to the steam generator without using a circulation pump. In this work, a vertical heater–vertical cooler, high-temperature, high-pressure, nonuniform-diameter, single-phase natural circulation loop is proposed. The rig contains a spacer grid assembly of electrical heaters in a core with a conical section in its upper plenum and a double helical coil steam generator. The proposed loop is analyzed using RELAP5 and various analytical models. First, these models are benchmarked with experimental data from the Facility to Investigate Natural Circulation in SMART or FINCLS. The model results are found to be in good agreement with the experimental data. The same models are then employed to investigate the proposed natural circulation facility, named the Integral PWR-type SMR Test Rig (iPSTR), to investigate the mass flow rate as a function of geometric and process parameters. Core power input was varied from 5 to 82.5 kW at a maximum system pressure of 10 bar and a maximum elevation difference of thermal centers of 3400 mm. Elevation differences of the thermal centers and diameter of core are found to be important parameters that affect thermal-hydraulic performance significantly. However, cone angle, spacer grid, and system pressure are found to have no significant effect on the performance of the iPSTR. Moreover, the proposed iPSTR is found to possess higher Reynolds number compared with the existing facilities.

Health State Identification Method of Nuclear Power Main Circulating Pump Based on EEMD and OQGA-SVM

Main circulation pump is the only high-speed rotating equipment in primary loop of nuclear power plant. Its function is to ensure the normal operation of primary loop system by controlling the circulating flow of reactor coolant. In order to ensure long-term healthy operation of nuclear power main circulating pump, a method for identifying the health states of nuclear power main circulating pump based on ensemble empirical mode decomposition (EEMD) and support vector machine optimized by optimized quantum genetic algorithm (OQGA-SVM) is proposed. Vibration signal of main circulating pump is decomposed by EEMD. Vibration signal characteristics of nuclear power main circulating pump in healthy state and different fault states are analyzed and target characteristic indexes are put forward. Then, health state identification model of main circulation pump of OQGA-SVM is established, and target characteristic indexes are used as input parameter of the model. Finally, combined with experimental data, the model analysis and validation show that the health state identification method of nuclear power main circulating pump based on EEMD-OQGA-SVM can accurately and effectively identify the states of main circulation pump, has a higher identification accuracy than EEMD-SVM method and is more efficient and accurate than EEMD-QGA-SVM method.

Multicomponent numerical model for heat pump control with low-temperature heat storage: A benchmark in the conditions of Central Europe

This paper presents a computational parametric study on increasing the Seasonal Coefficient of Performance for residential heat pumps, utilizing an enhanced computational model and comparing it to previous research. The model computes a system that consists of a heat pump, low-temperature heat storage, heat exchanger and circulation pump, and a control unit which allows the heat pump to choose either low-temperature heat storage or ambient air as the favorable heat source. A parametric study is conducted to obtain results from a numerical model describing in detail the heat storage, surrounding soil, and the behavior of a water tank with and without temperature stratification and with two different geometries. These are combined into three different systems. Each system uses an algorithm for heat pump control that combines equithermal regulation and deferred heat storage discharging based on long-term temperature trends. Python is used to transform the numerical model into a computational model, and the assessment of heat pump operation is made based on meteorological data from the years 2012–2021 recorded in the city of Brno, Czech Republic, Central Europe. Previous studies have suggested that this combination for heat pump control and a more detailed numerical model of the system should result in a SCOP increase. In this study, heat losses of an actual occupied building with floor area of 140 m2 without considering heat radiation are used. The results show that stratification cannot be omitted for numerical modelling, and that the geometry of the storage influences how the storage should be designed. For a wide and shallow storage, it is better to insulate the system and increase the SCOP from 3.8 to 4.65, but non-insulated deep and narrow storage can increase the from 3.8 to 4.95. Flow rate is also an important parameter with a local maximum between 0.01 and 0.02 kg/s for every cubic meter of the storage. When a system consisting of parts readily available on the market is used at optimal conditions, the resulting increase can be from 11.8% up to as high as 25.7% with low-temperature heat storage ranging from 9 to 25 cubic meters.

Flow Structure and Short-Term Riverbed Evolution in Curved Flumes

River bending is the major effect responsible for bed topography and bank changes. In this study, fluid velocity (measured by a three-dimensional Doppler advanced point current meter) and bed topographical data have been collected in 40 sections of an experimental model. The whole flume was composed of an organic glass bend, upstream and downstream water tanks, two transition straight sections, a circulation pump, and a connection pipeline. Each section has been found to be characterized by a primary circulation and a small reverse circulation, with some sections even presenting three more or more circulation structures. The minimum circulation intensity has been detected in proximity to the top of the curved channel, while a region with small longitudinal velocity has been observed near the concave bank of each bend, corresponding to the flat bed formed after a short period of scouring. The maximum sediment deposition and scour depth in the presence of a uniform distribution of living flexible vegetation within 10 cm of the flume wall have been found to be smaller than those observed in the tests conducted without vegetation.

Energetske performanse infiltriranih i elevacionih zemunica na području grada Kragujevca - numeričko istraživanje

This paper investigates the energy potential of different modern earth-sheltered building types, during a seven-month period (October 1 to April 30), in order to achieve sustainable development. The subject of the research is a one-story residential building (total net area 102.5 m2), intended for a family of four, located in the territory of the city of Kragujevac (central Serbia). The heating system consists of a ground source heat pump, geothermal vertical probes, floor panel heaters, and two circulation pumps. Four types of infiltrated earth-sheltered buildings, as well as one elevation earth-sheltered building, were investigated by numerical analysis (using the EnergyPlus software). The energy performances of all of the mentioned earth-sheltered buildings were compared with the energy performance of classic above-ground buildings. All of the buildings have the same geometric, construction, and thermo-technical performance. The research results show that, in infiltrated earth-sheltered buildings, the annual consumption of final (electrical) energy can be reduced by 2.53-21.64% (depending on the number of external building elements in direct contact with the soil). Modern architecture should still be focused on the development of elevation earth-sheltered buildings because in them the annual consumption of final (electrical) energy for heating can be reduced by more than 40%.

Transportation of fertilized northern pike eggs in a small mobile egg transportation system: Effect of time and comparison to a traditional method

Fish eggs must commonly be transported from their place of origin to another location, such as hatcheries or experimental laboratories. In the present study, two transportation methods (plastic bags and an incubation mini-system) and three transportation scenarios (5, 9, and 12 h after fertilization) were tested for northern pike eggs that were fertilized one hour before transportation. The size of the presented incubation mini-system, combining incubation jars, water circulation pumps, and space for dry ice for cooling, enabled egg transportation, even in the trunk of a car. When the number of dead eggs, which were monitored during the incubation process, and the larval hatching rate (mean = 64%) were compared, no statistically significant differences were found between the two transportation methods or among the three transportation durations. In conclusion, although the presented incubation mini-system was found to be appropriate for transporting eggs over a long distance for up to 11 h (12 h after fertilization), the simpler method of transportation in bags is recommended for such transportation time. It is, however, recommended that the incubation mini-system be tested over a longer distance and time in the future, including longer no-movement periods.