This paper presents an experimental study to investigate the effect of using the magnetic water conditioner on the properties of water. The water flows through a closed loop, while the pH, TDS, and hardness represent ...This paper presents an experimental study to investigate the effect of using the magnetic water conditioner on the properties of water. The water flows through a closed loop, while the pH, TDS, and hardness represent its properties. For magnetic water conditioner with flux density of 170 mT, results showed that pH increased by 15.65% for 820 minutes of non-stop circulation. The increase in pH is divided to 93.5% for the first 360 minutes, and 6.5% for the last 460 minutes. TDS and Hardness of water are not affected by the magnetic water conditioner. Water remembers and keeps the impact of passing through the magnetic field for several hours, and pH decreased by 0.642 in24 hours. While the results lead to introduce and create the magnetized water saturation curve and water memory meter.展开更多
Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare ...Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.展开更多
Because of its ease of implementation,a linear PID controller is generally used to control robotic manipulators.Linear controllers cannot effectively cope with uncertainties and variations in the parameters;therefore,...Because of its ease of implementation,a linear PID controller is generally used to control robotic manipulators.Linear controllers cannot effectively cope with uncertainties and variations in the parameters;therefore,nonlinear controllers with robust performance which can cope with these are recommended.The sliding mode control(SMC)is a robust state feedback control method for nonlinear systems that,in addition having a simple design,efficiently overcomes uncertainties and disturbances in the system.It also has a very fast transient response that is desirable when controlling robotic manipulators.The most critical drawback to SMC is chattering in the control input signal.To solve this problem,in this study,SMC is used with a boundary layer(SMCBL)to eliminate the chattering and improve the performance of the system.The proposed SMCBL was compared with inverse dynamic control(IDC),a conventional nonlinear control method.The kinematic and dynamic equations of the IRB-120 robot manipulator were initially extracted completely and accurately,and then the control of the robot manipulator using SMC was evaluated.For validation,the proposed control method was implemented on a 6-DOF IRB-120 robot manipulator in the presence of uncertainties.The results were simulated,tested,and compared in the MATLAB/Simulink environment.To further validate our work,the results were tested and confirmed experimentally on an actual IRB-120 robot manipulator.展开更多
This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful...This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy.To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions.Thus,the shorter the start-up time,the better for the environment and economy.High-pressure(HP)part of the turbine originally located on the Queen Elizabeth II unit was analysed.Advanced numerical calculations by thermal fluid-solid-interaction(Thermal FSI)were carried out.A series of simulations were performed for the accelerated start-up with controlled steam injection.A description of the chosen calculation methodology and the results obtained by simulation are included in this paper.The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up.The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm(0.83 mm for ultra-fast start-up).Reducing the steam turbine start-up time by 75%results in a 36.7 tons reduction in fuel consumption for start-up,resulting in an annual savings of 5372 USD.In conclusion,the concept proposed by the authors is safe,less expensive and does not affect the life of the turbine.In addition,results and applications from Siemens prove that additional injection of cooling steam is possible.展开更多
In hot arid countries with severe weather, the summer air conditioning systems consume much electrical power at peak period. Shifting the loads peak to off-peak period with thermal storage is recommended. Model A of r...In hot arid countries with severe weather, the summer air conditioning systems consume much electrical power at peak period. Shifting the loads peak to off-peak period with thermal storage is recommended. Model A of residential buildings and Model B of schools and hospitals were used to estimate the daily cooling load profile in Makkah, Saudi Arabia at latitude of 21.42°N and longitude of 39.83°E. Model A was constructed from common materials, but Model B as Model A with 5 - 8 cm thermal insulation and double layers glass windows. The average data of Makkah weather through 2010, 2011 and 2012 were used to calculate the cooling load profile and performance of air conditioning systems. The maximum cooling load was calculated at 15:00 o’clock for a main floor building to a 40-floor of residential building and to 5 floors of schools. A district cooling plant of 180,000 Refrigeration Ton was suggested to serve the Gabal Al Sharashf area in the central zone of Makkah. A thermal storage system to store the excess cooling capacity was used. Air cooled condensers were used in the analysis of chiller refrigeration cycle. The operating cost was mainly a function of electrical energy consumption. Fixed electricity tariff was 0.04 $/kWh for electromechanical counter, and 0.027, 0.04, 0.069 $/kWh for shifting loads peak for the smart digital counter. The results showed that the daily savings in consumed power are 8.27% in spring, 6.86% in summer, 8.81% in autumn, and 14.55% in winter. Also, the daily savings in electricity bills are 12.26% in spring, 16.66% in summer, 12.84% in autumn, and 14.55% in winter. The obtained maximum saving in consumed power is 14.5% and the daily saving in electricity bills is 43% in summer when the loads peak is completely shifted to off-peak period.展开更多
The shift towards the renewable energy market for carbon-neutral power generation has encouraged different governments to come up with a plan of action.But with the endorsement of renewable energy for harsh environmen...The shift towards the renewable energy market for carbon-neutral power generation has encouraged different governments to come up with a plan of action.But with the endorsement of renewable energy for harsh environmental conditions like sand dust and snow,monitoring and maintenance are a few of the prime concerns.These problems were addressed widely in the literature,but most of the research has drawbacks due to long detection time,and high misclassification error.Hence to overcome these drawbacks,and to develop an accurate monitoring approach,this paper is motivated toward the understanding of primary failure concerning a grid-connected photovoltaic(PV)system and highlighted along with a brief overview on existing fault detection methodology.Based on the drawback a data-driven machine learning approach has been used for the identification of fault and indicating the maintenance unit regarding the operation and maintenance requirement.Further,the system was tested with a 4 kWp grid-connected PV system,and a decision tree-based algorithm was developed for the identification of a fault.The results identified 94.7%training accuracy and 14000 observations/sec prediction speed for the trained classifier and improved the reliability of fault detection nature of the grid-connected PV operation.展开更多
The paper discusses the advancements and applications of neural networks, specifically ChatGPT, in various fields, including chemistry education and research. It examines the benefits of AI and ChatGPT, such as their ...The paper discusses the advancements and applications of neural networks, specifically ChatGPT, in various fields, including chemistry education and research. It examines the benefits of AI and ChatGPT, such as their ability to process and analyze large amounts of data, create personalized training systems, and offer problem-solving recommendations. The paper delves into practical applications, showcasing how ChatGPT can be utilised to augment chemistry learning. It provides examples of using ChatGPT for creating tests, generating multiple-choice questions, and studying chemistry in general. Concerns are voiced about the ethical and societal impact of AI development. In conclusion, it explores the exciting potential of AI to tackle challenges that may exceed human capabilities alone, paving the way for further exploration and collaboration between humans and intelligent machines.展开更多
A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in...A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in this paper. Indirect evaporative cooler is used for sensible cooling of air which then is used for air conditioning purposes. Mathematical model was developed allowing determining heat transfer surface, outlet air temperature and specific humidity of the air being cooled. To make the model simpler some simplifications have been incorporated. The model has high level of correctness and can be used to calculate and design different types of evaporative heat exchangers. Analysis of results of calculations by the help of the developed model prove that the surface of heat exchanger depends on the thickness of water film layer by the regularity of direct proportionality. Moreover, increasing of the water film thickness brings to the decreasing of the efficiency of evaporative type heat exchanger. The model can be used for correct calculation and design of an evaporative cooling air conditioning systems.展开更多
Cavitation in pumps causes destructive consequences;it must be detected and prevented. The aim of the present work is investigating the validity of sound spectrum as a prediction tool for pump cavitation. Results show...Cavitation in pumps causes destructive consequences;it must be detected and prevented. The aim of the present work is investigating the validity of sound spectrum as a prediction tool for pump cavitation. Results showed that;for the discrete frequencies of RF = 47.5 Hz, and BPF = 285 Hz and its second, third, and fourth harmonics of 570 Hz, 855 Hz, and 1140 Hz respectively;there are no great variations in the noise signal for the cavitation and non-cavitation conditions. For the discrete frequency of 147 Hz, there is also no great variation in the noise signal at this frequency. The only apparent result is that;the occurrence of cavitation results high energy noise signals at high frequencies from 1000 Hz to 10000 Hz. The absence of any discrete frequency to be monitored makes the sound spectrum not valid as a prediction tool for cavitation in the pumps.展开更多
Recently, microreactors have become available to be fabricated and used safely. The performance of these microreactors depends on the behavior of the multiphase flow hydrodynamics. Gas-liquid flow through T-junction m...Recently, microreactors have become available to be fabricated and used safely. The performance of these microreactors depends on the behavior of the multiphase flow hydrodynamics. Gas-liquid flow through T-junction microchannel reactor is simulated numerically using VOF （volume of fluid） method. 2-D （Two-dimensional） and 3-D （three-dimensional） models of the T-junction microchannel reactor were introduced to the simulations. Both 2-D and 3-D simulations for nitrogen-water flow were performed in the FLUENT （Fluent. Inc.） computational fluid dynamics package. The third direction effect has been studied by comparing the results of the 2-D and 3-D simulations with the published experimental data. Also, the bubble slug length was calculated for the 2-D and 3-D simulations. Furthermore, the hydrodynamics of the flow was studied for the 2-D and 3-D simulations, and compared with other experimental data. The pressure drop, mean bubble velocity, the velocity distribution and the void fraction were calculated and found to be in good agreement with published data.展开更多
The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effe...The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effects on the transmission heat through outer walls, ceiling and glazing windows. Good thermal isolation for buildings is important to reduce the transmitted heat and consumed power. The buildings models are constructed from common materials with 0 - 16 cm of thermal insulation thickness in the outer walls and ceilings, and double-layers glazing windows. The building heat loads were calculated for two types of walls and ceiling with and without thermal insulation. The cooling load temperature difference method, <em>CLTD</em>, was used to estimate the building heat load during a 24-hour each day throughout spring, summer, autumn and winter seasons. The annual cooling degree-day, <em>CDD</em> was used to estimate the optimal thermal insulation thickness and payback period with including the solar radiation effect on the outer walls surfaces. The average saved energy percentage in summer, spring, autumn and winter are 35.5%, 32.8%, 33.2% and 30.7% respectively, and average yearly saved energy is about of 33.5%. The optimal thermal insulation thickness was obtained between 7 - 12 cm and payback period of 20 - 30 month for some Egyptian Cities according to the Latitude and annual degree-days.展开更多
This paper presents the development of remotely operated Quadcopter system. The Quadcopter is controlled through a graphical user interface (GUI) where the communication between GUI and Quadcopter is constructed by us...This paper presents the development of remotely operated Quadcopter system. The Quadcopter is controlled through a graphical user interface (GUI) where the communication between GUI and Quadcopter is constructed by using wireless communication system. The Quadcopter balancing condition is sensed by FY90 controller and IMU 5DOF sensor. For smooth landing, Quadcopter is equipped with ultrasonic sensor. All signals from sensors are processed by Arduino Uno microcontroller board and output from the Arduino Uno microcontroller board is implemented to control Quadcopter propellers. The GUI is designed using Visual Basic 2008 Express as interfacing communication between the Proportional, Integral and Derivative (PID) controller and the Quadcopter system. The experiment shows that the Quadcopter system can hover while maintain it balancing and the stability is guaranteed. Moreover, the developed system is able to cope with load disturbance up to 250 gduring the hover position. Maximum operated time of Quadcopter is six minutes using 2200 mAh Lipo battery and operate time can be increased by using largest battery capacity.展开更多
Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient con...Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient condition was designed thermostatic chamber where was monitoring temperature course on main parts of cooling device （energy converter, air cooler and heat pipes） at various position of cooling device. It was found, if the cooling device is in tilt position the cooling performance is better. But if the tilt angel of gravity assisted heat pipe is higher the heat transfer is lower. From reason improve heat transfer cooling device at tilt angle are manufactured heat pipes with the sintered, mesh screen and grooved capillary structures and tested their thermal performance at vertical and tilt angel 45~ position by calorimetric method. Article describes manufacturing process and thermal performance measuring method of wick heat pipes. This experiment testify that the wick heat pipe is able operate at tilt angle position than gravity assisted heat pipe and application of wick heat pipes into cooling device will improve his cooling performance.展开更多
This paper presents theoretical issues about CIM （common information model） and CGMES （common grid model exchange standard）, which will allow the exchange of data bases for power flow, short circuit and dynamics a...This paper presents theoretical issues about CIM （common information model） and CGMES （common grid model exchange standard）, which will allow the exchange of data bases for power flow, short circuit and dynamics at ENTSO-E （European network for transport system operators for electricity） level. Grid model exchange is a complex process covering a variety of use cases, which include the exchange of equipment information, topology information, information on power system state variables, steady state hypothesis information. CGMES is an ENTSO-E standard that follows the CIM guidelines of IEC （International Electrotechnical Commission） TC57/WG13 in order to comply with the requirements of the European network codes. There are mentioned in the paper the challenges of implementing CIM and CGMES in Transelectrica for the planning cases.展开更多
The developed auxiliary software serves to simplify, standardize and facilitate the software loading of the structural organization of a complex technological system, as well as its further manipulation within the pro...The developed auxiliary software serves to simplify, standardize and facilitate the software loading of the structural organization of a complex technological system, as well as its further manipulation within the process of solving the considered technological system. Its help can be especially useful in the case of a complex structural organization of a technological system with a large number of different functional elements grouped into several technological subsystems. This paper presents the results of its application for a special complex technological system related to the reference steam block for the combined production of heat and electricity.展开更多
This paper deals about testing thermal properties of the cooling device with heat pipes at inclination position, in consequence of using the natural convection to improve heat transfer properties. Head point testing o...This paper deals about testing thermal properties of the cooling device with heat pipes at inclination position, in consequence of using the natural convection to improve heat transfer properties. Head point testing of cooling device is monitoring temperature on the aluminium block of energy converter, heat pipes and ribs under temperature condition 30 ℃ in thermostatic chamber. Testing of the device was performed at tilt angles positions 0, 10 and 20° from the vertical level. The heat flux loaded to energy converter was 450 W. The next goal of the paper is to research on influence working position of the wick heat pipe on their thermal performance. In this research heat pipes were made with capillary structure sintered from copper powder granularity 100, 63 and 50 μm filled with water and ethanol. Next heat pipe thermal performance was performed by measuring heat source and working positions. Knowledge of these two research goals can bring potential improvements in purpose of cooling device for effective heat sink from high power electronic components.展开更多
Emerging sub-synchronous interactions(SSI)in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and ...Emerging sub-synchronous interactions(SSI)in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and power electronics devices.SSI phenomenon occurs when two power system elements exchange energy below the synchro-nous frequency.SSI phenomenon related to wind power plants is one of the most significant challenges to main-taining stability,while SSI phenomenon in practical wind farms,which has been observed recently,has not yet been described on the source of conventional SSI literature.This paper first explains the traditional development of SSI and its classification as given by the IEEE,and then it proposes a classification of SSI according to the current research status,reviews several mitigation techniques and challenges,and discusses analysis techniques for SSI.The paper also describes the effect of the active damping controllers,control scheme parameters,degree of series compensation,and various techniques used in wind power plants(WPPs).In particular,a supplementary damping controller with converter controllers in Doubly Fed Induction Generator based WPPs is briefly pronounced.This paper provides a real-istic viewpoint and a potential outlook for the readers to properly deal with SSI and its mitigation techniques,which can help power engineers for the planning,economical operation,and future expansion of sustainable development.展开更多
The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical con...The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.展开更多
The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(F...The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.展开更多
Faults’recognition in the distribution feeders(DFs)is extremely important for improving the reliability of the distribution system.Therefore,this paper proposes a technique to identify the faults on the DF using the ...Faults’recognition in the distribution feeders(DFs)is extremely important for improving the reliability of the distribution system.Therefore,this paper proposes a technique to identify the faults on the DF using the Stockwell Transform(ST)dependent variance feature and Hilbert transform(HT)by utilizing current signals.By element to element multiplication of the H-index,we compute using HT aided decompositions of current waveforms and VS-index,and calculate through ST aided decomposition of current waveforms.By utilizing the decision rules,various faults are classified.Different faults studied in this work are line to ground,double line,double line to ground and 3-Φto ground.For high fault impedance,this technique is effectively utilized.Furthermore,variations in the fault incidence angles are also utilized to test the performance of the proposed technique.To perform the proposed algorithm,a IEEE-13 bus system is developed in MATLAB/Simulink software.The algorithm effectively classified the faults with accuracy greater than 98%.The algorithm is also successfully validated on the IEEE-34 bus test system.Furthermore,the algorithm was successfully validated on the practical power system network.It is recognized that the developed method performed better than the discrete Wavelet transform(DWT)and ruled decision tree based protection scheme reported in various literature.展开更多
文摘This paper presents an experimental study to investigate the effect of using the magnetic water conditioner on the properties of water. The water flows through a closed loop, while the pH, TDS, and hardness represent its properties. For magnetic water conditioner with flux density of 170 mT, results showed that pH increased by 15.65% for 820 minutes of non-stop circulation. The increase in pH is divided to 93.5% for the first 360 minutes, and 6.5% for the last 460 minutes. TDS and Hardness of water are not affected by the magnetic water conditioner. Water remembers and keeps the impact of passing through the magnetic field for several hours, and pH decreased by 0.642 in24 hours. While the results lead to introduce and create the magnetized water saturation curve and water memory meter.
文摘Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.
文摘Because of its ease of implementation,a linear PID controller is generally used to control robotic manipulators.Linear controllers cannot effectively cope with uncertainties and variations in the parameters;therefore,nonlinear controllers with robust performance which can cope with these are recommended.The sliding mode control(SMC)is a robust state feedback control method for nonlinear systems that,in addition having a simple design,efficiently overcomes uncertainties and disturbances in the system.It also has a very fast transient response that is desirable when controlling robotic manipulators.The most critical drawback to SMC is chattering in the control input signal.To solve this problem,in this study,SMC is used with a boundary layer(SMCBL)to eliminate the chattering and improve the performance of the system.The proposed SMCBL was compared with inverse dynamic control(IDC),a conventional nonlinear control method.The kinematic and dynamic equations of the IRB-120 robot manipulator were initially extracted completely and accurately,and then the control of the robot manipulator using SMC was evaluated.For validation,the proposed control method was implemented on a 6-DOF IRB-120 robot manipulator in the presence of uncertainties.The results were simulated,tested,and compared in the MATLAB/Simulink environment.To further validate our work,the results were tested and confirmed experimentally on an actual IRB-120 robot manipulator.
文摘This paper analyses the issue of accelerated start-up of a marine steam turbine,which is an important problem because the start-up of a steam machine involves the combustion of fuel that is not transformed into useful energy.To find novel technologies that offer improvements in this aspect is essential due to restrictions on reducing ship emissions.Thus,the shorter the start-up time,the better for the environment and economy.High-pressure(HP)part of the turbine originally located on the Queen Elizabeth II unit was analysed.Advanced numerical calculations by thermal fluid-solid-interaction(Thermal FSI)were carried out.A series of simulations were performed for the accelerated start-up with controlled steam injection.A description of the chosen calculation methodology and the results obtained by simulation are included in this paper.The stress occurring during the accelerated start-up are approximately 40 MPa higher than those during the reference start-up.The relative elongations between the rotor and the hull during accelerated start-up reach a maximum value of 0.89 mm(0.83 mm for ultra-fast start-up).Reducing the steam turbine start-up time by 75%results in a 36.7 tons reduction in fuel consumption for start-up,resulting in an annual savings of 5372 USD.In conclusion,the concept proposed by the authors is safe,less expensive and does not affect the life of the turbine.In addition,results and applications from Siemens prove that additional injection of cooling steam is possible.
文摘In hot arid countries with severe weather, the summer air conditioning systems consume much electrical power at peak period. Shifting the loads peak to off-peak period with thermal storage is recommended. Model A of residential buildings and Model B of schools and hospitals were used to estimate the daily cooling load profile in Makkah, Saudi Arabia at latitude of 21.42°N and longitude of 39.83°E. Model A was constructed from common materials, but Model B as Model A with 5 - 8 cm thermal insulation and double layers glass windows. The average data of Makkah weather through 2010, 2011 and 2012 were used to calculate the cooling load profile and performance of air conditioning systems. The maximum cooling load was calculated at 15:00 o’clock for a main floor building to a 40-floor of residential building and to 5 floors of schools. A district cooling plant of 180,000 Refrigeration Ton was suggested to serve the Gabal Al Sharashf area in the central zone of Makkah. A thermal storage system to store the excess cooling capacity was used. Air cooled condensers were used in the analysis of chiller refrigeration cycle. The operating cost was mainly a function of electrical energy consumption. Fixed electricity tariff was 0.04 $/kWh for electromechanical counter, and 0.027, 0.04, 0.069 $/kWh for shifting loads peak for the smart digital counter. The results showed that the daily savings in consumed power are 8.27% in spring, 6.86% in summer, 8.81% in autumn, and 14.55% in winter. Also, the daily savings in electricity bills are 12.26% in spring, 16.66% in summer, 12.84% in autumn, and 14.55% in winter. The obtained maximum saving in consumed power is 14.5% and the daily saving in electricity bills is 43% in summer when the loads peak is completely shifted to off-peak period.
基金The authors extend their appreciation to the Deputyship for Research&Innovation,Ministry of Education in Saudi Arabia for funding this research work through the project number“IFPHI-022-135-2020”and King Abdulaziz University,DSR,Jeddah,Saudi Arabia.
文摘The shift towards the renewable energy market for carbon-neutral power generation has encouraged different governments to come up with a plan of action.But with the endorsement of renewable energy for harsh environmental conditions like sand dust and snow,monitoring and maintenance are a few of the prime concerns.These problems were addressed widely in the literature,but most of the research has drawbacks due to long detection time,and high misclassification error.Hence to overcome these drawbacks,and to develop an accurate monitoring approach,this paper is motivated toward the understanding of primary failure concerning a grid-connected photovoltaic(PV)system and highlighted along with a brief overview on existing fault detection methodology.Based on the drawback a data-driven machine learning approach has been used for the identification of fault and indicating the maintenance unit regarding the operation and maintenance requirement.Further,the system was tested with a 4 kWp grid-connected PV system,and a decision tree-based algorithm was developed for the identification of a fault.The results identified 94.7%training accuracy and 14000 observations/sec prediction speed for the trained classifier and improved the reliability of fault detection nature of the grid-connected PV operation.
文摘The paper discusses the advancements and applications of neural networks, specifically ChatGPT, in various fields, including chemistry education and research. It examines the benefits of AI and ChatGPT, such as their ability to process and analyze large amounts of data, create personalized training systems, and offer problem-solving recommendations. The paper delves into practical applications, showcasing how ChatGPT can be utilised to augment chemistry learning. It provides examples of using ChatGPT for creating tests, generating multiple-choice questions, and studying chemistry in general. Concerns are voiced about the ethical and societal impact of AI development. In conclusion, it explores the exciting potential of AI to tackle challenges that may exceed human capabilities alone, paving the way for further exploration and collaboration between humans and intelligent machines.
文摘A simplified model for analysis of heat and mass transfer between air stream and flowing down water film in counter-flow plate heat exchanger which serves as an indirect evaporative cooler is theoretically analyzed in this paper. Indirect evaporative cooler is used for sensible cooling of air which then is used for air conditioning purposes. Mathematical model was developed allowing determining heat transfer surface, outlet air temperature and specific humidity of the air being cooled. To make the model simpler some simplifications have been incorporated. The model has high level of correctness and can be used to calculate and design different types of evaporative heat exchangers. Analysis of results of calculations by the help of the developed model prove that the surface of heat exchanger depends on the thickness of water film layer by the regularity of direct proportionality. Moreover, increasing of the water film thickness brings to the decreasing of the efficiency of evaporative type heat exchanger. The model can be used for correct calculation and design of an evaporative cooling air conditioning systems.
文摘Cavitation in pumps causes destructive consequences;it must be detected and prevented. The aim of the present work is investigating the validity of sound spectrum as a prediction tool for pump cavitation. Results showed that;for the discrete frequencies of RF = 47.5 Hz, and BPF = 285 Hz and its second, third, and fourth harmonics of 570 Hz, 855 Hz, and 1140 Hz respectively;there are no great variations in the noise signal for the cavitation and non-cavitation conditions. For the discrete frequency of 147 Hz, there is also no great variation in the noise signal at this frequency. The only apparent result is that;the occurrence of cavitation results high energy noise signals at high frequencies from 1000 Hz to 10000 Hz. The absence of any discrete frequency to be monitored makes the sound spectrum not valid as a prediction tool for cavitation in the pumps.
文摘Recently, microreactors have become available to be fabricated and used safely. The performance of these microreactors depends on the behavior of the multiphase flow hydrodynamics. Gas-liquid flow through T-junction microchannel reactor is simulated numerically using VOF （volume of fluid） method. 2-D （Two-dimensional） and 3-D （three-dimensional） models of the T-junction microchannel reactor were introduced to the simulations. Both 2-D and 3-D simulations for nitrogen-water flow were performed in the FLUENT （Fluent. Inc.） computational fluid dynamics package. The third direction effect has been studied by comparing the results of the 2-D and 3-D simulations with the published experimental data. Also, the bubble slug length was calculated for the 2-D and 3-D simulations. Furthermore, the hydrodynamics of the flow was studied for the 2-D and 3-D simulations, and compared with other experimental data. The pressure drop, mean bubble velocity, the velocity distribution and the void fraction were calculated and found to be in good agreement with published data.
文摘The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effects on the transmission heat through outer walls, ceiling and glazing windows. Good thermal isolation for buildings is important to reduce the transmitted heat and consumed power. The buildings models are constructed from common materials with 0 - 16 cm of thermal insulation thickness in the outer walls and ceilings, and double-layers glazing windows. The building heat loads were calculated for two types of walls and ceiling with and without thermal insulation. The cooling load temperature difference method, <em>CLTD</em>, was used to estimate the building heat load during a 24-hour each day throughout spring, summer, autumn and winter seasons. The annual cooling degree-day, <em>CDD</em> was used to estimate the optimal thermal insulation thickness and payback period with including the solar radiation effect on the outer walls surfaces. The average saved energy percentage in summer, spring, autumn and winter are 35.5%, 32.8%, 33.2% and 30.7% respectively, and average yearly saved energy is about of 33.5%. The optimal thermal insulation thickness was obtained between 7 - 12 cm and payback period of 20 - 30 month for some Egyptian Cities according to the Latitude and annual degree-days.
文摘This paper presents the development of remotely operated Quadcopter system. The Quadcopter is controlled through a graphical user interface (GUI) where the communication between GUI and Quadcopter is constructed by using wireless communication system. The Quadcopter balancing condition is sensed by FY90 controller and IMU 5DOF sensor. For smooth landing, Quadcopter is equipped with ultrasonic sensor. All signals from sensors are processed by Arduino Uno microcontroller board and output from the Arduino Uno microcontroller board is implemented to control Quadcopter propellers. The GUI is designed using Visual Basic 2008 Express as interfacing communication between the Proportional, Integral and Derivative (PID) controller and the Quadcopter system. The experiment shows that the Quadcopter system can hover while maintain it balancing and the stability is guaranteed. Moreover, the developed system is able to cope with load disturbance up to 250 gduring the hover position. Maximum operated time of Quadcopter is six minutes using 2200 mAh Lipo battery and operate time can be increased by using largest battery capacity.
文摘Paper deals about testing of device with gravity assisted heat pipes and about researching of wick heat pipes used to effective heat transfers from power switches of energy converter. At first, to simulate ambient condition was designed thermostatic chamber where was monitoring temperature course on main parts of cooling device （energy converter, air cooler and heat pipes） at various position of cooling device. It was found, if the cooling device is in tilt position the cooling performance is better. But if the tilt angel of gravity assisted heat pipe is higher the heat transfer is lower. From reason improve heat transfer cooling device at tilt angle are manufactured heat pipes with the sintered, mesh screen and grooved capillary structures and tested their thermal performance at vertical and tilt angel 45~ position by calorimetric method. Article describes manufacturing process and thermal performance measuring method of wick heat pipes. This experiment testify that the wick heat pipe is able operate at tilt angle position than gravity assisted heat pipe and application of wick heat pipes into cooling device will improve his cooling performance.
文摘This paper presents theoretical issues about CIM （common information model） and CGMES （common grid model exchange standard）, which will allow the exchange of data bases for power flow, short circuit and dynamics at ENTSO-E （European network for transport system operators for electricity） level. Grid model exchange is a complex process covering a variety of use cases, which include the exchange of equipment information, topology information, information on power system state variables, steady state hypothesis information. CGMES is an ENTSO-E standard that follows the CIM guidelines of IEC （International Electrotechnical Commission） TC57/WG13 in order to comply with the requirements of the European network codes. There are mentioned in the paper the challenges of implementing CIM and CGMES in Transelectrica for the planning cases.
文摘The developed auxiliary software serves to simplify, standardize and facilitate the software loading of the structural organization of a complex technological system, as well as its further manipulation within the process of solving the considered technological system. Its help can be especially useful in the case of a complex structural organization of a technological system with a large number of different functional elements grouped into several technological subsystems. This paper presents the results of its application for a special complex technological system related to the reference steam block for the combined production of heat and electricity.
文摘This paper deals about testing thermal properties of the cooling device with heat pipes at inclination position, in consequence of using the natural convection to improve heat transfer properties. Head point testing of cooling device is monitoring temperature on the aluminium block of energy converter, heat pipes and ribs under temperature condition 30 ℃ in thermostatic chamber. Testing of the device was performed at tilt angles positions 0, 10 and 20° from the vertical level. The heat flux loaded to energy converter was 450 W. The next goal of the paper is to research on influence working position of the wick heat pipe on their thermal performance. In this research heat pipes were made with capillary structure sintered from copper powder granularity 100, 63 and 50 μm filled with water and ethanol. Next heat pipe thermal performance was performed by measuring heat source and working positions. Knowledge of these two research goals can bring potential improvements in purpose of cooling device for effective heat sink from high power electronic components.
基金supported financially by the Ministerio de Ciencia e Innovación(Spain)and the European Regional Development Fund,under Research Grant WindSound project(Ref.:PID2021-125278OB-I00).
文摘Emerging sub-synchronous interactions(SSI)in wind-integrated power systems have added intense attention after numerous incidents in the US and China due to the involvement of series compensated transmission lines and power electronics devices.SSI phenomenon occurs when two power system elements exchange energy below the synchro-nous frequency.SSI phenomenon related to wind power plants is one of the most significant challenges to main-taining stability,while SSI phenomenon in practical wind farms,which has been observed recently,has not yet been described on the source of conventional SSI literature.This paper first explains the traditional development of SSI and its classification as given by the IEEE,and then it proposes a classification of SSI according to the current research status,reviews several mitigation techniques and challenges,and discusses analysis techniques for SSI.The paper also describes the effect of the active damping controllers,control scheme parameters,degree of series compensation,and various techniques used in wind power plants(WPPs).In particular,a supplementary damping controller with converter controllers in Doubly Fed Induction Generator based WPPs is briefly pronounced.This paper provides a real-istic viewpoint and a potential outlook for the readers to properly deal with SSI and its mitigation techniques,which can help power engineers for the planning,economical operation,and future expansion of sustainable development.
文摘The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.
文摘The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.
文摘Faults’recognition in the distribution feeders(DFs)is extremely important for improving the reliability of the distribution system.Therefore,this paper proposes a technique to identify the faults on the DF using the Stockwell Transform(ST)dependent variance feature and Hilbert transform(HT)by utilizing current signals.By element to element multiplication of the H-index,we compute using HT aided decompositions of current waveforms and VS-index,and calculate through ST aided decomposition of current waveforms.By utilizing the decision rules,various faults are classified.Different faults studied in this work are line to ground,double line,double line to ground and 3-Φto ground.For high fault impedance,this technique is effectively utilized.Furthermore,variations in the fault incidence angles are also utilized to test the performance of the proposed technique.To perform the proposed algorithm,a IEEE-13 bus system is developed in MATLAB/Simulink software.The algorithm effectively classified the faults with accuracy greater than 98%.The algorithm is also successfully validated on the IEEE-34 bus test system.Furthermore,the algorithm was successfully validated on the practical power system network.It is recognized that the developed method performed better than the discrete Wavelet transform(DWT)and ruled decision tree based protection scheme reported in various literature.
