Volume 2, No. 9 (2003)
Articles
THREE INPUTS MULTIPLEXER FOR MULTIPLYING LOGICAL SIGNALS DISPLAY CHANNELS ON THE OSCILLOSCOPE
ABABEI ŞTEFAN, CULEA GEORGE, ROTAR DAN
In this paper is presented a device that can realize the multiplexing of three logical signals with the purpose of simultaneous display on the oscilloscope screen. The device delays in time and amplitude the three signals as well as it synclironizes the oscilloscope time base with the tact signal. Being made with cheep and reliable elements, the device makes it possible for a single channel oscilloscope to be used for diverse application in the analysis of the way logical circuit work.
A VIRTUAL APPARATUS FOR FREQUENCY MEASUREMENT
ABABEI ŞTEFAN, CULEA GEORGE, HAZI ANETA
In this paper is presented a virtual measurement instrument, which could measure alternative periodic frequency signals (unnecessary' sinusoidal) with a better precision in 40-60Hz, which would use a cheep DAQ board of PCL-LPM-16 type made by National Instrument. This apparatus was realized with LABVIEW programming medium. The results obtained with this apparatus versus the results obtained with a numerical instrument are presented.
THE GAS DYNAMIC GENERATOR FOR INTENSIFICATION OF PROCESSES OF THERMAL STABILIZATION AND CLARIFICATION IN BREWING INDUSTRY
BĂLAN VALERIU, BĂLAN GEORGE
The results of an experimental research regarding the application of a gas dynamic ultrasonic generator for intensification of the processes of clarification and thermal stabilization in beer production are presented It has been shown that there is a lime range of sonic treatment for technological fluids. The sonic technology allows to lower considerably consumes of thermal and electric energy for brewing industry.
THE CHEMICAL EXERGY OF FUELS
BEGLET NATALIA
The calculation of the chemical exergy is a very important part of the exergetical analysis. Many scientists, such as Z. Rant, D. Buimovici, W. Fratzscher, H. Baehr and E. Schimidt, attempted to determine chemical exergy of fuel with different methods. In this paper is presented the calculation of chemical exergy of fuel based on the J. Szargut and T. Styryiska method which have developed the Z Rant method.Some numerical examples of calculation are presented at the end of the papers.
CONTRIBUTIONS TO THE ENERGETICAL OPTIMISATION OF THE FLUID TRANSPORT WITH HEAT FLOW BY CONDUITS
BENCHE VICTOR, UNGUREANU VIRGIL-BARBU
We present contributions to the definition and hydro-energetically optimization of the single-phase and constant density fluids transport in a non-adiabatic stationary flow regime by pressurized, long and smooth pipes (non-finned). On define relevant energetically indicators thus the energetically efficiency of the transport, the energetically slope, the heat transfer efficiency, possibilities of the economical design based on the minimization of the total power lost by transport. The design is generalized using the hydraulic radius, economical section area and particularized for cylindrical pipes. The study highlights the influence factors, optimization measures that can be adopted in the design and exploitation. Finally, the study is exemplified by numerical calculus for two categories.
ABOUT A STABLE RUNNING OF AN ASYNCHRONOUS GENERATOR IN A STRUCTURE OF THE WIND POWER INSTALLATION
BERZAN VLADIMIR, ERMURACHI IURIE
The application of asynchronous generators in a structure of the wind power installations limits by poor quality of electrical energy deliverable to an autonomous customer. It is conditioned by variable wind speed and restricted technical feasibilities of regulation of a magnetic flux in the machine. In paper the conditions of self-excitation of a three-phase asynchronous generator with capacitive excitation are reviewed is executed under the autoinductive scheme of actuation of a generating winding and excitation winding. The conditions of steady excitation and stable operations of the generator are formulated at variable wind speed and at change of load. It is reached by stabilization of a current in a capacitive branch by regulation of value of an accessory active resistance live sequentially with capacitors.
SOME ASPECTS CONCERNING THE CHOICE CRITERIA OF METALLIC MATERIALS FOR 420 t/h STEAM BOILER OF CENTRAL HEATING-AND-POWER PLANT FROM BACAU
CIUCESCU EDUARD
In general, at the choice of metallic materials it is taken into consideration both the reliability and the price. The steam boilers are under pressure at high temperature industrial equipments. Being given the operation risks presented by steam boilers, at the used metallic materials choice has priority the aspects bound to reliability as follows: mechanical resistance, corrosion resistance. The metallic materials used in construction of main elements of steam boilers show a multitude of types, which have to correspond to some very severe requirements. In general, the greatest part of metallic materials of main elements of steam boilers made in Romania are described by Romanian standards (STAS), but the rest of materials by soviet (GOST), German (DIN) or American (ASTM) standards as well by foreign norms, as for example, Mannesmann, Sandvik, Marrel Freres, Hoesch, Creusol- Loire, Uddeholm. At Central Heating-and-Power Plant from Bacau, the metallic materials of main elements of 420 t/h steam boiler are described by Romanian and soviet standards as well by Marrel Freres norms, inspired from American norms. From economic reasons, all these metallic materials were made at Iron and Steel Works from Galati. This paper presents some aspects concerning choice criteria of metallic materials used at manufacturing of 420 t/h steam boiler main elements from Central Heating-and-Power Plant from Bacau, taking into consideration chemical composition, the influence of some alloying elements, some mechanical characteristics and the design stipulated standards.
A CALCULATION METHOD TO DETERMINE THE NUMBER OF ROTATION OF THE HEAT WHEEL AT ROTARY LJUNGSTROM TYPE PREHEATER
CIUCESCU EDUARD
A major problem for all Central Heating-and-Power Plants is to achieve as much as possible fuel savings. The improvement the efficiency of such plants includes, also, the maintaining the temperature of combustion air at maximum level. In the case of dirty gaseous fuels, such as the coal, the most used air-preheater system is rotary Ljungstrom type preheater. Due to the many sources of boiler inefficiency, the temperature of flue gas changes and the number of rotation of heat wheel must change also. This paper presents a calculation method to determine the number of rotation of the heat wheel on the basis the maintaining time necessary for the metallic matrix of the heat wheel to absorb maximum energy from the flue-gas.
A SIMPLIFIED RELATION TO DETERMINE THE MAINTAINING TIME IN FLUE GAS OF METALLIC MATRIX OF THE HEAT WHEEL OF ROTARY LJUNGSTROM TYPE PREHEATER
CIUCESCU EDUARD
To save fuel as much as possible is one of the main problem for all Central Heating-and-Power Plants. In this goal, one way is to keep the temperature of combustion air at maximum level, in the case of dirty gaseous fuels, such as the coal, the most used air- preheater system is rotary Ljungstrom type preheater, like at the Central Heating-and-Power Plant of Bacau. Due to the many factors, the temperature of flue gas changes and, consequently, the number of rotation of the heat wheel must change. For this reason, is necessary to determine the maintaining time necessary for the hot side of the heat wheel to absorb maximum energy from the flue gas. This paper tries to establish a relation to determine the maintaining time in flue gas of metallic matrix of the heat wheel from rotary Ljungstrom type preheater in order to absorb maximum energy from the flue gas.
COMPLEMENTARY METHOD CONTROL FOR UNCERTAIN NONLINEAR DISCRETE-TIME SYSTEMS
COSTACHE GABRIEL
In this paper, different cases that describe the benefit of using a complementary control method together with classics controllers, applied to nonlinear discrete-time systems are presented. A high-order iterative learning controller, assisted by a feedback controller, is proposed, with the consideration of a control saturater. Tracking error bounds are functions of the bounds of uncertainty, disturbance, and re-initialization error and. in the case of absence of this elements, tracking error bounds tend to 0.
RECOVERY AND REEVALUATION OF LANDFILL GAS
CRACIUN LIZICA SIMONA, ION V. ION, SPIRU PARASCHIV
This paper presents the advantage of utilization the gas extracted from landfill sites. By extracting landfill gas, methane emissions are prevented and fossil fuels are saved if landfill gas is subsequently used as a source of energy. The goal of a landfill gas-to-energy project is to convert landfill gas into useful energy such as electricity, steam, boiler fuel, vehicle fuel or pipeline -quality gas.
DIELECTRIC PERMITTIVITY OF DIELECTRIC MIXTURES
CRET RODICA, CRET LAURA, MATEESCU DANUT
Due to the increasing importance and wide utilization of composite materials, the paper presents some considerations on the calculation of dielectric permittivity of mixtures. First, some analytical solutions of the problem are presented, and then the results are compared with the numeric solutions obtained with a FEM based software produced by the ANSOFT Corporation. The analytic and numeric results seem to be in good agreement, which means that the software is reliable and can be Used for the simulation of complex structures, for which no analytical solutions are available.
DIELECTRIC PROPERTIES OF SOME CERAMIC/POLYMER MIXTURES
CRET RODICA, MATEESCU DANUT
This paper presents a study of dielectric properties of some ceramic/polymer composites. It is also emphasizes the polarization of relaxation phenomena, based on the frequency variation of complex permittivity of the compounds. Based on the comparison between experimental and theoretical results, it has been established that the best theoretic formula for the approximation of the static permittivity as a function of the compounds properties, for a binary mixture with very different dielectric permittivities, is Lichtenecker-Rother formula.
THERMAL UTILIZATION OF SOLAR ENERGY IN ABSORPTION SYSTEMS
CUJBA LUMINITA
Refrigeration driven by solar thermal energy is attractive because fossil fuels can be substituted by renewable energy whose availability usually is in phase with required cooling loads. This report presents one possible solution using as refrigerant NH3 in a solar absorption refrigeration cycle. The heat is taken from solar collectors and used to increase the temperature of the NH3 solution. There are several types of solar collectors, but in this report the evacuated-tube collectors is chosen due to the extremely high temperatures they canachieve (77°-175°C). This study is based on the variation of the COP as a function of the generator and the evaporator temperature and the variation of the FAb as a function of the generator and the evaporating temperature and conversion factor.
ACTIVE INTERNET
DOBROVICI ANDREI-LIVIU
Remote control and monitoring over the Internet has become popular over the last few years. Internet accessibility enhances the functionality of devices by allowing the control of actuators and the receiving of data from sensors. This paper presents an embedded Internet system capable of monitoring and controlling a process. Topics such as timing and network connection issues, data rates and limitations are also discussed.
ASPECTS REFERING TO THE ECONOMIC ANALYSIS OF THE POWER PLANTS
DRAGAN MARCEL, PANAIT TANASE
This work presents the method on the basis of which we should calculate the costs of the products generated by the power plants as well as the main aspects that follows the application of this method. In concrete way, we'll calculate the costs of the products generated by a power plant that delivers combined electrical and thermal energy, we'll emphasize the accuracy of the exergoeconomic method.
HUMAN BEHAVIORS SIMULATOR FOR AUTONOMOUS ROBOT
DUMITRAŞCU ALEXANDRU
In this paper, the applications that describe a simple mechanism of control, which generates behaviors is presented. All these human cognitive states are implemented into a Khepera robot. The software applications of Braitenberg vehicles are very simple, but the robot's behavior is extremely unexpected and complex. The applications are developed in Lab VIEW. The implemented behaviors on the Khepera robot, conformity of Braitenberg theories are: aggressive, shy, curious, repellent.
SOME THEORETIC ASSESSMENTS OF FINANCIAL FEASIBILITY OF COGENERATION SYSTEM, CONSIDERING THE SAFETY LEVEL OF SYSTEM
GRIGORE ROXANA, CULEA GEORGE, HAZI ANETA
The paper presents some theoretic assessments about feasibility analysis with consider safety level of cogeneration system. The basic condition for the fulfillment of the cogeneration system objective function is guarantee of energy supply continuity. The paper shows system reliability indicators and key parameters for a technical-economic analysis.
THE STUDY OF THE CONDENSING BOILERS EFFICIENCY
GUTU AUREL, GHIES BOGDAN
In this paper is presented the analyzer`s results of the work of the boilers with the burning gases steam condensation. At the gases cooling till 30...40 ° C, the condensate mass is 1.1 - 1.3 kg/m3 natural gas which increases the boiler`s efficiency with 12 - 14%. At the installation of the boilers inside of the heated buildings the efficiency with reference to the fuel inferior heating value constitutes 106 - 108%, with the superior heating value - about 12% less.
ALORITHM AND COMPUTER PROGRAM FOR OPTIMIZATION OF WORKING REGIMES OF POWER COGENERATION PLANT
HAZI ANETA*, HAZI GHEORGHE**, SAJIN TUDOR*
In this paper it is presented an algorithm and computer program for optimization of operating regimes of power regeneration plant that supplies technological consumers. It is described the optimization algorithm standing out steps that are examined for solving of optimization problem. The minimization of fuel consumption for producing of thermal and electrical energy is considered the success state. Based on this algorithm, it is established a computer program that contains a main program and under-programs that are called by it. The general structure of main program and under-programs established arc presented in this paper.
CORRELATION BETWEEN PRODUCTION AND SPECIFIC ENERGETICALLY CONSUMPTIONS
HAZI ANETA*, HAZI GHEORGHE**, GRIGORE ROXANA*
In this paper it is analyzed evolution of production and of specific energetically consumption and consequence decreasing of production above specific energetically consumption in a company. Finally, there are proposed some solutions for decreasing specific thermal energy consumption.
EXERGY OPTIMIZATION IN A PAPER MACHINE
HAZI ANETA*, HAZI GHEORGHE**, CULEA GEORGE*
This paper examines an exergy optimization method of the working regimes of the paper machines that include dryer cylinders. The optimization objective is the minimization of the exergy specific consumption regarding the quality constrains of the paper. The optimization model and the numerical results obtained for a typing paper machine are presented.
OPTIMIZATION OF THE PRODUCTION WITHIN THE SERVICE COMPANIES IN THE POWER FIELD
HAZI GHEORGHE*, HAZI ANETA**, ABABEI ŞTEFAN**
The paper analyses the possibilities to optimize the manufacturing size for the companies created after the reorganization of the Romanian Electricity Authority - RENEL. In particular the paper focuses on the companies within the electricity networks field. For a given number of orders, of various types, the optimum programmed is established so as to comply with the obligations stipulated by contracts, to ensure the proper tasks for the employees, and, in addition, to generate the maximum benefit for the company. In its latter part the paper presents the steps towards solving the problem and the results of a practical example.
MODERN NUMERICAL TECHNICS USED IN OPTIMIZING THE WORKING STATES IN LARGE-SCALE SYSTEMS
HAZI GHEORGHE*, HAZI ANETA**, CULEA GEORGE**
The paper presents the advantages of using the product form of inverses of sparse matrices (PFI) in the optimization processes of the working states in power systems. It also presents ways, tested by the author, of determining the PFI. Two ways of pivoting are compared, both from the point of view of conserving the sparsity of the represented matrix - usually the Jacobi matrix of the equality type restrictions - and from the point of view of the calculus duration. In its latter part the paper presents a few methods of performing the calculations with the product form matrices.
INTELLIGENT TECHNIQUES FOR THE ENERGY SAVING OF BUILDING MANAGEMENT AND IN THE OFFICES
HOJBOTA MARIA RODICA
Modern buildings have to increasingly cope with the expectation that their energy demand decreases steadily. The automation of building energy management is capable of enabling remarkable reductions in energy consumption. With combined light and louver management systems energy savings up to 70%.
INTELLIGENT TECHNIQUES FOR SMALL BOILER CONTROL
HOJBOTA MARIA RODICA
The boiler Metering and Monitoring Project has resulted in signifiant savings at Ontario Northlands where the system was installed. The systems benefits impacts in three areas: - operational savings including maintenance, labour and capital cost; - utilities savings including natural gas, water and steam through efficiency gains; - environmental reductions in NOx, C02, and combustibles such as methane. The system achieves monitoring and automatic control through the use of a programmable logic controller PLC, coupled with a desktop computer PC for monitoring of boiler plant operation. The monitoring software includes trend analysis, allowing faster and more accurate diagnosis of alarms, upset conditions and preventative maintenance scheduling to cure minor problems before they become major ones.The PLC uses a fuzzy logic controller which anticipates steam load due to changes in the weather to maintain adequate capacity reserve on the boilers. This has operated successfully and allowed for a more constant steam pressure than obtainable by manual operation.
SIMULATION OF THE BOILER FURNACE'S DYNAMIC OPERATION
ION V. ION, CRACIUN LIZICA SIMONA
The paper presents the analysis of the boiler furnace behavior working at dynamic regime. A mathematical model describing the thermodynamic processes, which take place inside the furnaces, is presented. The application of the numerical simulation on a coal fired boiler furnace and a gas fired boiler furnace are also described. The results of the simulation provide conclusions for the automatizated balanced working of the both air blowers and exhauster of the steam boiler.
FROM ENERGY ANALYSIS TO COMPARED COST-TO-QUALITY ANALYSIS OF THE THERMAL SYSTEMS
IONITA ION
The paper presents briefly the first law-based energy analysis, the both first and second law-based exergy analysis, the constructal design optimization, the exergo- economic analysis and finally the compared cost-to-quality analysis. Each of the above mentioned procedures solves additionally and successively more analytical requirements and represents steps of knowledge advance.
CONSIDERATIONS REGARDING THE UTILISATION OF THE FUZZY LOGIC CONTROLLERS FOR ELECTRICAL DRIVE SYSTEMS WITH D.C. MOTORS
LIVINŢI PETRU, ROTAR DAN
This paper presents a speed control system for a D.C. motor supplied from a variable D.C. voltage regulator in which it is used a fuzzy logic controller. It is determined the mathematical model of the D.C. motor. It is analyzed the dynamic behavior of the speed control loop of the D.C. motor through numerical simulation in the MATLAB-SIMULINK programation environment.
STRUCTURES OF AUTOMATIC CONTROLLERS DESIGNED THROUGH FREQUENCY METHODS
LIVINŢI PETRU
Because of the calculus technique development, the frequency methods utilization for the synthesis of the automatic controllers has know a spectacular return. This paper presents the structure of a current controller designed through the frequency logarithm characteristic method. This structure is composed of two controllers: a PIT1 controller and a PDT1 controller.
MATHEMATICAL MODEL FOR EXPERIMENTAL CALCULUS OF INDUCE VOLTAGE IN A PIPELINE
MICU DAN, MICU DAN
A mathematical model employing the finite-difference method is used for the experimental calculus of the induced voltages across points on an underground pipeline running parallel to a faulted line and remote earth. The fault is considered outside the parallel exposure so that the conductive coupling is negligible so only the inductive couplings are taken into account.
POWER NETWORKS RELIABILITY INDICES INCLUDING THE HUMAN ERRORS AND ADVERSE WEATHER INFLUENCE
MUNTEANU FLORIN
The new emerging energy market structures allow for a high competition between utilities. The reliability is of a major interest for specialists with a view to improve the quality of supply and to optimize the corresponding economical indices. Unfortunately, in the new restructured electrical power systems many reliability aspects are neglected and the consequences are and could be severe. In some countries there are national or regional bodies, like NERC in USA, involved in global quality and reliability analysis. The paper is dedicated to the review of most important customer and load oriented reliability indices focusing on the importance of a more detailed and refined approach in considering the primary reliability parameters in Romania compared to the actual standards and prescriptions. A study case based on a real network is finally presented revealing the different reliability indices and some influence due to network components reliability, network structure, human errors and adverse weather.
EFFICIENT ENERGY MANAGEMENT IN CONTROL SYSTEM ARCHITECTURES
NIŢU COSTICĂ
In the paper a new control strategy for efficient energy management in computer control systems is proposed. The proposed strategy consists in a global, a system method which includes a control systems energy saving, with process computers, communication systems and process optimization. For control systems architectures the method with isolated single parts energy saving is proposed to be replaced with control systems energy saving.
THE KEYS TO RAPID AND COST EFFECTIVE THERMOECONOMIC ANALYSIS OF THE HEAT POWER STATION
PALASH SERGHEY
The differentiated principle of formation of the tariff for thermal energy, produced in a combined mode, is offered by the exergocconomic method [8]. The fuel component in the tariff of any heat flow is determined proportionally with the exergetic rates, and values of specific constant costs arc distributed proportionally of energy rates for each flow [1].
NEW TECHNIQUES FOR ELECTROMAGNETIC FIELD MODELING
POPA SORIN, ROTAR DAN
In this paper it is presented the activities of the process modeling and digital simulation of the electromagnetic behavior of an electrical device. The latest new digital techniques for modeling and simulation of the electromagnetic behavior of the electrical systems are the Finite Element Method (FEM) and the Boundary Element Method (BEM). Both tins techniques are analyzed and used in this paper for the modeling and simulation of an electrical vacuum switch.
FUZZY LOGIC CONTROL FOR REAL-TIME POWER SYSTEM STABILIZATION ACTUATING OF THE DRILLING RIG/SERVICING UNIT
PRUTEANU EUSEBIU
For a proper operation, this integrated system requires a stable operating condition by means of an adequate control. The power system is a dynamic one. It is constantly being subjected to disturbances cause. For a system with interconnected elements to be able to supply the power load demand, when the transients cause the disturbance, a new acceptable operating steady state condition must be reached. That is why, the power system must be a stable one. It is important that these disturbances do not drive the system to an operating unstable condition.
ELECTROMAGNETIC COMPATIBILITY STUDY BY NUMERICAL ANALYSIS
ROTAR DAN, POPA SORIN
In this paper it is presented the activities of the digital simulation of the electromagnetic behavior of an electrical device. The studies of the electromagnetic compatibility in die energetic domain of the electrical energy transportation have many applications concerning the design and the exploitation of the energetic system. For the electromagnetic compatibility study it is necessary the modeling and simulation the electromagnetic field behavior.
DIGITAL FILTERING WITH DIGITAL SIGNAL PROCESSING CONTROLLER
ROTAR DAN, LIVINŢI PETRU, ABABEI ŞTEFAN
The paper reports a digital filter implementation with the TMS 320F240 Digital Signal Processing controller. The design and simulation of the filter is achieved wit the Matlab toolboxes. The main purpose of the signal digital filtering is the electrical asynchronous engine command.
ELECTRICAL PROCESSING OF EXHAUST GASES FROM THE BURNING INSTALLATIONS
SAJIN TUDOR*, CRĂCIUN ALEXANDRU**, HAZI ANETA*, BOTEZ CLEOPATRA***
This paper presents a new technology of nitrogen and sulphur oxides removal in the installations for burning of organic fuels, which is based on the oxidation of the last ones up to the corresponding acids used pulsed corona discharge and alternating electric field, neutralization of the formed acids by introduction of ammonia in gas and receiving of nitrate and sulphate of ammonia used as fertilizers.
ENHANCEMENT AND CONTROL OF BURNING PROCESSES IN AN ELECTRIC FIELDS
SAJIN TUDOR*, CRĂCIUN ALEXANDRU**, GABA AUREL***, PĂUNESCU LUCIAN***, SURUGIU GEORGE***, BOTEZ CLEOPATRA****, MOTORIN OLEG****
An apparatus, consisting of a Seitan 20 gas burner with a fuel flow rate 20 m3N/h, supplied with a system of Kanthal electrodes and an adjustable source of a high voltage, was investigated on the experimental bench of Bucharest Metallurgic Research Institute, ROMANIA. It was found that an increase of voltage up to 12 kV, and current up to 32 µA, respectively, results in the evident improvement of the burning process: increasing of flame temperature from 1100 up to 1190 °C, decreasing of CO percentage from 1.2 up to 0.012 %, reducing of the fuel consumption about 5%. Annual savings resulted from the using of such apparatus is around 292 USD.
ENERGY SAVING GREENHOUSE AIR TEMPERATURE CONTROL
SIT MIHAIL, JURAVLEOV ANATOLII, POPONOVA OLGA, SIT BORIS
As energy costs are one of the main production costs many efforts were made to reduce the energy consumption of greenhouses. One possibility is the development of new control strategies. The cascade control system of the greenhouse is investigated. The external loop is organized on the base of air temperature controller. For the compensation of „fast" disturbances (solar radiation, wind speed) the control of water flowrate through the hot-water system in the dependence of the signal proportional to disturabances is realized Also predictive control law is used.
ENERGY SAVING CONTROL SYSTEM OF A HEAT EXCHANGER
SIT MIHAIL, JURAVLEOV ANATOLII, SIT BORIS
The improved model of the shell-and-tube steam-water heat exchanger is presented. A nonlinear PID control law is proposed for such exchanger for mitigation of output temperature variations because of fluid flow oscillations. Simulation results are given to estimate the effectiveness of the proposed approach. The disturbance limiting control law is also presented. The control law ensures the increase of precision of stabilization of the temperature in the outlet of the heat exchanger on the assumption of the minimum of the heat flow rate (performance criterion) under the action of disturbances of the heating agent flow rate.
THE ANALYSIS OF THERMAL CIRCUITS DEFICIENSIES OF SUGAR-REFINERIES AND OPPORTUNITIES OF ITS IMPROVEMENT
TCACI LARISA
In this paper is given the analysis of thermal and technological circuits of sugar- refineries wich causes increasing of expenditure of fuel and primary steam. There are suggest some explications about maked negativ effects. There are indicated opportunities of improvement of thermal circuits for reducing the dependence of consumption of primary steam from quality of sugar beet. Increasing of efficiency of thermal circuits and installation of steam-jet compressors permits increasing of coefiicient of thermodynamic efficiency for evaporation station and improvement of technological processes.
THE CONCEPT OF MONITORING OF TECHNICAL STATE OF INSULATION OF ELECTRICITY GENERATORS
TIRSU MIHAI, TIRSU VALENTINA
The preliminary monitoring of technical state insulation of the generator includes detection of appearance of defects, overseeing their development in time, estimation of a degree of danger of these defects for the equipment, localization of defects and taking a step for an avoidance of their transition in unchecked process of fast development. The efficiency of monitoring systems and preliminary diagnostic is largely determined by principles and methods of measurement of informative parameters and processing techniques of this information.
COMPARISON OF SINGLE AND DOUBLE BURIED LINE SOURCE TX MODELS
TONT GABRIELA, TONT DAN GEORGE
Because of the complexity of the result for the case of two buried line sources it would be desirable to be able to use the TX model resulting from the single line source solution to treat the case of two buried pipes. Since the heat loss and TX factor are directly proportional for each of the models we can determine what errors are induced by treating two source systems with the one source model simple by computing and comparing the TX factors for each model when the same total heat flow is used.
ASSESSMENT OF HEAT LOSS USING INFRARED THERMOGRAPHY
TONT GABRIELA, TONT DAN GEORGE
The TX method allows quantification of heat losses from the temperature profile of the ground's surface above the buried heat distribution pipeline. Basically, the method uses the integral of the surface temperature distribution at the ground's surface along with climatological and district heating system data to get at an empirical estimate of the heat loss.
THE TX FACTOR FOR SINGLE AND DOUBLE BURIED LINE SOURCE OF HEAT
TONT GABRIELA, TONT DAN GEORGE
For measuring the TX factor in practice it is difficult to establish what the undisturbed ground temperature will be at some point far from the pipes influence. Thus, rather than define the TX factor relative to the undistributed ground temperature, we defined the TX factor as being in relation to the lowest temperature within distance, xm from the centerline of the pipes, in the two cases discussed in the paper.
POWER TRANSFORMER PROTECTION PAST, PRESENT AND FUTURE
VASILIEVICI ALEXANDRU*, BALASIU FLORIN**, MORARU GHEORGHE***
The paper analysis the power transformer protective systems evolution beginning with electro-magnetic relays until numerical protection terminals. A comparison between advantages and disadvantages of electro-mechanical relays and numerical protection terminals focused on the differential protection is shown. The paper also includes a block diagram of a numerical protection terminal for the 110 kV / medium voltage power transformers.
REMOTE PROCESS CONTROL MONITORING USING MOBILES
VIRTEJANU IULIAN
The paper proposes a new method of remotely monitoring and updating of parameters of a controlled project / regulator using mobile phones (and other small portable devices) and the GPRS wireless protocol. The application for the cell phone is written using J2ME runtime environment, making it portable to any device that supports this standard.
ASPECTS CONCERNING THE GLOBAL DEFINITION OF THE SPECIFIC EXERGY POWER IN CLASSIC, THERMOSTATIC AND MODERN, THERMODYNAMIC SENSE
VONICA IOAN
The paper tries to define in a classic, thermostatic and modern sense the notion of specific exergy power as global notion, in the context of thermodynamic in finite time. The analysis is set up on an exo and endoreversible thermodynamic process, respectively cycle, and also on an endoreversible but exoirreversible thermodynamic process, respectively cycle.
STUDIES CONCERNING THE OPTIMUM OF RANKINE THERMOENERGETIC CYCLE USIKG ENERGETIC RESOURCES OF MODERATE THERMAL POTENTIAL
VONICA IOAN
The paper presents an optimum analysis of a thermo energetic cycle based on thermodynamics in finite time. The economic and ecological conditions are determined, based on energetic and entropy surveys of a steam turbine installation functioning in real conditions and using thermal sources of moderate potential for steam production. The paper offers theoretical bases for setting up a using program in conditions of an economic functioning of such an installation.
THE AUTOMATIC LEADING OF FMS WITH THE HELP OF PROGRAMMABLE CONTROLLERS
CULEA GEORGE, ABABEI ŞTEFAN, HAZI ANETA, GRIGORE ROXANA
Starting from the model of a flexible processing system, this paper proposes an automatization solution based on programmable controllers. The implementation was done using programmable controllers PS4, EM4, connected to the network. The leading system created displays a high degree of flexibility, integrating all the leading functions of FMS.
THE MODELLING OF LEADING FUNCTIONS FOR A FLEXIBLE MANUFACTURING SYSTEM
CULEA GEORGE, ABABEI ŞTEFAN, HAZI ANETA
This paper intends to present the configuration and modelling of a flexible manufacturing system. The modelling of the flexible manufacturing system is realized with the purpose of automatizing leading functions. The use of Grafcet method for modelling will allow an easier implementation of the automatic leading system.