Power Plant Condenser Research Articles

A correlation for heat transfer coefficient during stratified steam condensation in large flattened tubes with variable inclination and wall temperature

This paper experimentally investigates heat transfer coefficient during stratified-flow condensation in a large flattened-tube steam condenser with non-uniform heat flux and wall temperature, and varying inclination angle. The heat transfer test facility is designed and built to provide local measurements of wall temperature; combined with a CFD model, it also provides local heat flux and heat transfer coefficient.The condenser test tube is that commonly used in air-cooled condensers for power plants. The steel tube has inner dimensions of 216 mm height × 16 mm width. In addition, tube inclination is varied from 0° to 38° downwards. The test facility is designed to match the conditions of an operating condenser, with low steam mass flux, realistic development of flow regimes and a large temperature glide on the cooling side.The results show that heat transfer coefficient along the tube wall follows the Nusselt condensation model, while heat transfer through the stratified liquid layer at the tube bottom is predominantly driven by laminar forced convection. Commonly-used correlations for heat transfer coefficient are unable to accurately predict the experimental results, so a new correlation is proposed. The new correlation takes into account heat transfer through the stratified liquid layer at the tube bottom as well as through the condensing film along the tube wall. Recommendations are made for situations where: (1) the wall temperature is known and (2) the wall temperature is unknown. Finally, a recommendation is made for combining the correlation in the stratified condensate layer with a local model for determining condenser capacity.

Local heat transfer coefficient during stratified flow in large, flattened-tube steam condensers with non-uniform heat flux and wall temperature

Steam condensation heat transfer coefficient (HTC) in a large, flattened tube with non-uniform heat flux and wall temperature, and variable inclination angle is determined experimentally. The condenser tube is that typically used in an air-cooled condenser for power plants. The steel tube has an elongated-slot cross section with inner dimensions of 216 × 16 mm. Water vapor and liquid flow co-currently through a 5.7 m long air-cooled conditioning section, followed by a 0.12 m long water-cooled test section. The long conditioning section creates conditions in the test section that mimic the conditions in an operating condenser – allowing for the realistic development of flow regime and void fraction. HTC is then determined in the water-cooled section. The water-cooled section is designed as a crossflow heat exchanger to match the temperature and heat flux conditions of an air-cooled condenser. Visualization sections at the tube inlet and outlet allow determination of flow regime and void fraction. The flow is found to be stratified for all conditions. Tube inclination angle is varied from 0 to 38° downwards. Inlet quality in the water-cooled section ranges from 0 to 0.74. HTC is found to increase by more than 400% along the condenser height. In addition, inclination angle, wall-steam temperature difference, inlet water-steam temperature difference, water temperature glide and vapor quality are all found to affect the condensation HTC.

Structural-and-Parametric Optimization of Automatic Control System for Power Units of 300 MW in Wide Range of Load Variations

The structural-parametric optimization of the automatic control system for power units (ACSPU) of 300 MW of Lukoml’skaya GRES (Lukoml Local Condensing Power Plant) in the mode of both the permanent and the variable superheated steam pressure upstream of the turbine is under consideration. During 1974–1979, eight units of the Lukoml’skaya GRES implemented the ACSPU with a leading boiler power control. At the moment, these systems no longer meet all the frequency control quality requirements. In 2016, the daily schedule of electric loads of the Belarusian power system was as follows: the basic part of the schedule of electric loads was covered by combined heat and power plants (CHP) and by mini-CHP (which are the least maneuverable of the power plants), the semi-peak part of it–by local condensing power plants (Lukoml’skaya GRES and Berezovskaya GRES), the peak part–by import electric energy from neighboring power systems. However, this year the first unit of the Belorussian NPP will be put into operation, while the second one–in 2020. After the launch of the Belorussian NPP, it will cover basic part of load curve; CPPs will cover the semi-peak part, while the peak part of load curve will be covered by local condensing power plants. Correspondingly, due to the alteration of the structure of daily schedule of electric loads of the Belarusian power system, it is necessary to improve the efficiency of power units of Lukoml’skaya GRES as well as of the entire Lukoml’skaya GRES in general. This can be achieved with the help of the method of parametric optimization of the typical ACSPU proposed in the present paper. As a result, the quality of control of power and pressure upstream of the turbine will be improved; the flow of fuel will be reduced, as well as the turbine regulation valve displacement; environmental performance of entire power plant will be improved, too. The proposed technique has been confirmed by the results of computer simulation of transient processes in the automatic control system under external and internal disturbances.

Numerical investigation on complete condensation and freezing of finned tube air-cooled condensers

The freezing of finned tubes degrades the safety and efficiency of air-cooled condensers in power plants, so it is beneficial to investigate the freezing mechanism and anti-freezing measures for condensers. A conjugate model-based approach is presented, which characterizes the thermodynamic development between the vapor and cooling air of finned tube condensers, indicating that freezing is essentially caused by an immediate decline of the cooling-wall temperature at the complete condensation. The influences of the atmospheric temperature, cooling-air flow velocity, and vapor inlet mass flux on the film formation and wall temperature are examined for complete condensation, finding that the film formation depends on the vapor mass flux, while the cooling-air flow velocity dominates, whether or not the wall temperature achieves the freezing point. The internal flow of Λ frames in condensers reveals the mechanism whereby a serious freezing attacks the middle and lower sections of finned tube bundles but frees the upper. An air flow guiding device is recommended for the anti-freezing of condensers. This study contributes to the design of anti-freezing condenser frames and the secure operation of field condensers.

Повышение экономичности процессов генерации теплоты в коммунальной теплоэнергетике и теплотехнологиях на основе комбинированных когенерационно-теплонасосных технологий

Наиболее эффективной технологией генерации электрической и тепловой энергии для нужд коммунальной теплоэнергетики и теплотехнологий является комбинированная выработка энергии с использованием современных когенерационных установок на основе газопоршневых двигателей и газотурбинных установок, работающих на природном газе или биогазе. Комбинированная выработка энергии на такой базе существенно снижает затраты топлива в сравнении с традиционной раздельной выработкой электроэнергии на тепловых конденсационных электростанциях или на теплоэлектроцентралях и тепловой на котельных установках. Дальнейшее заметное повышение энергоэффективности процессов генерации теплоты для рассматриваемых нужд может быть достигнуто путем включения в процесс теплонасосных установок, т.е. создание комбинированных когенерационно-теплонасосных установок. Они будут иметь наивысшую топливную экономичность в сравнении со всеми существующими в традиционной теплоэнергетике. Это обусловлено целым рядом факторов. Современные когенерационные установки (КГУ) на базе газопоршневых двигателей (ГПД) и газотурбинных установок (ГТУ) имеют электрический к.п.д. выше, чем тепловая электростанция (ТЭС) или теплоэлектроцентраль (ТЭЦ) – 30…45 % и 28…35 %, соответственно. В котлах-утилизаторах более эффективно используется высокотемпературная сбросная теплота двигателей, в результате чего суммарный к.п.д. установок достигает 85…88 %. Такие установки обеспечивают децентрализацию производства электрической и тепловой энергии, поэтому на автономных КГУ существенно ниже, а иногда практически отсутствуют потери в электрических и тепловых сетях, достигающие в централизованных системах 8…12 % и 15…30%, соответственно. Немаловажным является и то, что они повышают надежность работы всего объекта, делая его независимым от внешних сетей. Включение в процесс генерации теплоты теплонасосной установки (ТНУ) вызывает заметное повышение энергоэффективности, увеличивая топливную экономичность, благодаря использованию практически даровой низкопотенциальной теплоты природного, промышленного или бытового происхождения, а также высокой эффективности преобразования в ТНУ этой теплоты в теплоту более высокого потенциала с использованием электрической энергии КГУ.
 Целью работы является оценка перспектив применения комбинированных когенерационно-теплонасосных установок на базе ГПД и ГТУ для повышения энергоэффективности и энергосбережения при генерации теплоты в коммунальной теплоэнергетике и теплотехнологиях, в частности, в процессах сушки.

Thermal Power Plant Condenser Fault Diagnosis Using Coordinated Condition Monitoring Approach

Thermal Power Plant Condenser Fault Diagnosis Using Coordinated Condition Monitoring Approach

Enhancement of steam condensation on titanium corrugated tubes under vacuum condition

Steam condensation tests were conducted on titanium corrugated tubes at the pressure of 5 kPa and 10 kPa, which are the operating pressures of a power plant condenser. Seven 22.2 mm O.D titanium corrugated tubes had 6.4 mm ≤ p ≤ 22.1 mm and 0.2 mm ≤ e ≤ 0.6 mm. The condensation heat transfer coefficient increased as the corrugation pitch or the corrugation depth decreased. The tube having p = 6.4 mm and e = 0.2 mm yielded the highest heat transfer coefficient with the enhancement from 57 % to 75 %. Comparison with Mehta and Raja Rao [17] correlation revealed that the data are predicted within ±15 %.

Research of parameter distributing simulation and modeling for the condenser in nuclear power plant

Condenser is an important component in the secondary loop of nuclear power plant. The modeling method is developed based on the physical model and reasonable assumptions. The parameter expression could calculate and simulate along with flow direction at any designated position through mathematical derivation. The influence of non-condensable gas in the condenser and liquid film heat conduction around the tube is applied to the simulation model which would impact heat transfer process. There are empirical correlations for these process and situation which could make the simulation model more detailed and accurate. There is simulation and calculation for the thermal hydraulic characteristics of the condenser both in steady state and during dynamic process. Main and key parameters are chosen to compared with the design data in the steady state. The results represent that the simulation model could have enough accuracy in the steady state. For the dynamic process there are two working conditions compared with JTopmeret and another extended working condition simulated for analysis. The dynamic responding could work well compared with JTopmeret in different working conditions which could prove the credibility of simulation model. With different requirements there may be different parameters obtaining in the calculation and simulation process. The simulation model could easily acquire parameters distribution along with flow direction. This method could use for the other similar condensers with the same physical process or structure. The present work can provide references for the design, operation and simulation of condensers in nuclear power plant.

Effect of Cooling Water Flow Path on the Flow and Heat Transfer in a 660 MW Power Plant Condenser

The effect of the cooling water flow path on the flow and heat transfer in a double tube-pass condenser for a 660 MW power plant unit was numerically investigated based on a porous medium model. The results were used to analyze the streamline, velocity, air mass fraction and heat transfer coefficient distributions. The simulations indicate that the cooling water flow path is important in large condensers. For the original tube arrangement, the heat transfer with the lower-upper cooling water flow path is better than that with the upper-lower cooling water flow path. The reason is that the steam cannot flow into the internal of upper tube bundle and the air fractions are higher in the upper tube bundle with the upper-lower cooling water flow path. An improvement tube arrangement was developed for the upper-lower cooling water flow path which reduced the back pressure by 0.47 kPa compared to the original scheme. Thus, the results show that the tube arrangements should differ for different cooling water flow paths and the condenser heat transfer can be improved for the upper-lower cooling water flow path by modifying the tube arrangement.

Cascading uses of geothermal energy for a sustainable energy supply for Meshkinshahr City, Northwest, Iran

While renewable energy has been considered as an unlimited energy resourcein recent years, increasing dependency on natural gas has created various economic and environmental problems in Iran. Among renewables, geothermal energy is a powerful source for producing electricity and heat, simultaneously. The Sabalan geothermal field in northwestern Iran has a great geothermal potential and 11 geothermal wells have been drilled there during the last decade. The present design of the Sabalan geothermal power plant does not utilize the potential of the waste hot water and this useful energy flow would be wasted by injecting it into the underground reservoir. In this study, four geothermal energy utilization scenarios are modelled, analyzed and compared. The first and second scenarios are focused on electricity production in single and double flash geothermal system, while the third and fourth ones consider direct uses besides electricity production. Direct applications considered in this paper are district heating, greenhouses, tourist centres, fish farming and heat supply for factories. Exergy analysis is conducted to find a reliable system design. Also, the efficiency analysis indicates that the double-flash condensing power plant designed can generate 27.5 MW electricity and 76.1 MW heat from existing wells with direct geothermal uses. Lastly in this paper, the environmental effect of producing electricity and heat in the proposed system shows 696,200 tons of CO2 emission reduced compared to the using fossil fuel power plants and heating system.

Analysis of flow resistance in bundles of power plant condensers

Shell-side pressure drop is a very important variable in the successful design of the condensers. The prediction of this pressure drop through the horizontal tube banks, with condensation, has long been a problem facing design engineers. Low pressure drop is a requirement in designing condensers for power plants. The paper presents a comparison of the various correlation to determine the pressure drop in the tube bundle. It is an important element for the verification of numerical simulations. Analysis of flow resistance for power plant condenser were made.

Techno-economic and environmental performances of heating systems for single-family code-compliant and passive houses

In this study the implications of different energy efficiency requirements and heating solutions for versions of a single-family house in southern Sweden is explored. Final energy use, primary energy use, climate impacts and lifecycle cost of heat supply are analyzed for the building versions designed to meet the current Swedish BBR 2015 building code and heated with district heating or exhaust air heat pump. A case where the building is designed to the Swedish passive house criteria and heated with exhaust air heat pump is also analyzed. The district heating is assumed to be supplied from combined heat and power plants using bio-based fuels. For the heat pump solutions, cases are analyzed where the electricity supply is from coal-fired condensing power plant or fossil gas combined cycle power plant as baseline scenario, and from a combination of improved fossil power plants and non-fossil power plants as long-term scenario. The analysis considers the entire energy chain from natural resources to the final energy services. The results show that the BBR heat pump heated building use the most primary energy compared to the other two alternatives. Lifecycle cost is reduced by about 7-12% when district heating is used instead of heat pump for a BBR code-compliant building. This study shows the importance of lifecycle and system-wide perspectives in analyzing the resource efficiency and climate impacts as well as economic viabilities of heating solutions for houses.

Comparison of separate and combined generation of energy carriers at a condensing power plant

Generation of additional produced energy carriers at the station, such as heat, cold, compressed air, hydrogen, air separation products, etc., due to the use of electric power unclaimed by consumers during off-peak electric load periods lets keeping the lower specific fuel consumption for the generation of electricity. The article is devoted to comparison of efficiency of two ways of power supply of the consumer with the electric power and one other produced energy carrier: separate and combined generation.

Effect of inclination on heat transfer and flow regimes in large flattened-tube steam condensers

An experimental study of convective steam condensation inside a large, inclined, flattened tube used in air-cooled condensers for power plants is presented. This is the fourth of a four-part group of papers. The first three parts (Kang et al., 2017; Davies et al., 2017, 2018) published in the same journal present the facility, pressure drop, void fraction, flow regime and heat transfer results, while this study presents the effects of inclination on heat transfer and flow regimes.The condenser is a flattened steel tube with brazed aluminum fins. The full tube has dimensions 10.72 m × 214 mm × 18 mm. The condenser tube is cut in half lengthwise and covered with a polycarbonate window to perform visualization simultaneously with the heat transfer measurements. The steam is condensed at atmospheric pressure, and cooled by air at a uniform velocity profile. The angle of inclination is varied from horizontal (0°) to 75° downward. Condenser performance is also predicted with a model.The majority of the condenser is found to be in the stratified flow regime for all inclinations tested, with only a short annular section at the inlet of the condenser. The tubes inclined greater than 60° are also found to have stratified-wavy flow near the condenser outlet. Overall condenser U is found to increase with increasing downward inclination angle of the condenser, with a maximum increase of approximately 4% at 75° inclination. This improvement is found to be the result of improved drainage and increased void fraction near the condenser outlet. Mean steam-side heat transfer coefficient1HTC – Heat transfer coefficient1 (HTC) is found to remain constant along the tube, and for the entire condenser, with changes in tube inclination angle. Commonly-used inclined condensation HTC correlations are found to underpredict the magnitude of the experimentally-determined steam-side HTC.

Failure Analysis on Leakage of Brass Condenser Tube in Thermal Power Plant

The corrosion failure analysis of the brass tube in a power plant condenser was conducted by the methods of chemical composition analysis, macro morphology inspection of the leakage point, metallurgical examination, scanning electron microscope and energy spectrum analysis etc. The results indicated that the failure of the brass tube was due to the erosion of the internal surface. The zinc content in the etching pits decreased obviously and dezincification corrosion could be classified. Some suggestions for anti-corrosion measures of the brass tubes were put forward.

The Application of Improved Fuzzy Analytic Hierarchy Process (FAHP) in the Condenser Fault Diagnosis in Power Plant

Since the influential factors of vacuum reduction of condenser are fuzzy and uncertain, the improved FAHP is used. By comparing every two of the influential factors, the fuzzy matrix is constructed. The weight index of influential factors of vacuum reduction of condenser in a certain power plant is calculated out quantitatively. The most important influential factor is found out. And there is a verification which exactly identified the fault of the condenser by using a real instance.

CHP Plants in Russia: the Necessity for Technological Renovation

The role of combined heat and power (CHP) plants in the electric power industry of Russia is shown. The operational efficiency analysis of public service CHP plants and the fuel, power, and age structure of the existing CHP plants are carried out. Their main problems, such as underuse of generating equipment, excessive production in the condensing mode, high degree of equipment wear, and technological heterogeneity, are identified. The necessity of technological renovation of the CHP plants is shown. The energy efficiency of the combined production of electric and thermal energy by the existing CHP plants is compared to modern technologies for their separate gas and coal production. It is shown that the thermal capacity of the CHP plants in Russia exceeds the required capacity by almost two times. Estimates of the CHP plant thermal capacity necessary to cover the current heat loads are obtained for Russian regions. Main directions of the CHP plants' renewal based on the use of competitive domestic equipment and operation according to the heat load schedule are determined. Systemic impacts achieved by technological renewal are determined for gas-fired CHP plants with allowance for the climatic and load features of the Russian regions. It is shown that the technological renewal of gas-fired CHP plants will allow saving up to 16% of today’s fuel consumption, reducing the total CHP thermal capacity by 47.5% with the same volume and heat supply mode. The operation of a CHP plant according to the heat load schedule leads to a reduction in the electric capacity of the CHP plant by 20% with an increase in electricity generation by 11%. As a result, the consumption of the installed electric and thermal capacity of the CHP plant increases dramatically as does the fuel efficiency and the annual loading balance of external gas-fired condensing power plants. The needs for GTPs and CCGTs required for the technological renovation of the CHP plants is assessed. The necessity for developing competitive domestic medium and high power GTPs is considered.

Seismic Analysis of Steel Solid Web Girder-RC Tubular Column Hybrid Structure

This paper aims to investigate the seismic performance of a novel type of steel–concrete hybrid supporting structure consisting of reinforced concrete (RC) tubular columns, steel solid web girder platform, and A-shaped steel frames. It is typically used to house air-cooled condensers (ACC) in thermal power plants (TPPs). First, the finite-element (FE) model was implemented in ABAQUS and the simulation approaches were validated by pseudo-dynamic test results of a scaled steel-concrete hybrid supporting structure. Then, the elasto-plastic time-history analysis of the steel solid web girder-RC tubular column hybrid structure was conducted. The El Centro (NS) record was scaled to peak ground acceleration (PGA) of 0.07, 0.20, 0.40 and 0.62 g to reflect the frequent, basic, rare, and very rare earthquakes. The dynamic characteristics, base shear force, lateral deformation performance, stiffness deterioration, and damage evolution characteristics were analyzed. The numerical results showed that the first vibration mode of this hybrid structure is torsion, due to its small torsional stiffness and the nonuniform distribution characteristics of stiffness and mass in the vertical direction; the lateral deformation shape is shear mode; and the damage mainly occurred on the RC tubular columns, while the steel components did not yield under severe earthquakes. In general, the overall seismic performance of the steel solid web girder-RC tubular column hybrid structural system could meet the seismic design requirements with respect to the high-intensity earthquakes.

Parametric Optimization for Automatic Control System of 300 MW Power Units at a Constant Steam Pressure Upstream of the Turbine

The problem of parametric optimization of automatic control systems of power units (ACSPU) of 300 MW at the Lukoml’skaya GRES (Lukoml Condensing Power Plant) at a constant superheated steam pressure upstream of the turbine is under consideration. During 1974–1979, eight units of the Lukoml’skaya GRES implemented ACSPU with a leading boiler power control, which will be forced to work in a wide range of loads due to the planned commissioning of two power units of the Belarusian NPP: the first one – in 2019, and the second one – in 2020. The total capacity of the Belarusian Nuclear Power Plant will amount to 2400 MW. In addition, modern requirements for the regulation of the frequency and flows of active electric power in the power system have been tightened: the time to reach the half value of the required power alteration should be 10 seconds within the normal and emergency reserves; the time to reach the full value of the required power alteration should be 30 seconds within the range of the normal reserve and 2 minutes – within the range of the emergency reserve. With this regard, increasing the efficiency of the units operating in the variable part of the electric load schеdule by the use of modern methods of calculation of parameters of the dynamic adjustment of the regulating devices of ACSPU becomes an urgent problem. The methodology of parametric optimization of the typical ACSPU that make it possible to improve the quality of power regulation and the pressure of the superheated steam upstream of the turbine is presented. The described technique is illustrated by the results of computer simulation of transient processes in the system when the task and internal disturbances are worked out, which confirm the correctness of the proposed technique in comparison with the known methods of optimization of the typical ACSPU.

Study on the performance of indirect air-cooled system influenced by environmental temperature

In order to explore the mechanism of the performance of Air-cooled system influenced by environmental temperature, indirect air-cooled towers with surface condensers in power plant were studied in this paper. Through a proper simplification, the geometric models of indirect air-cooled towers and other major buildings around which may affect the fluid flow were established. When it comes to the air-cooled towers, which were located in the central region of flow and heat transfer, the structure type of the towers and the radiators should be clearly presented. Flow resistance and heat transfer characteristics of radiators were correctly and objectively taken into account, the reliability of which was verified by field test. Numerical simulation study on the thermal performance of the indirect air-cooled system with surface condensers was conducted by creating corresponding mathematical and physical models on the condition of designed wind director and velocity. At the same time, the thermal performance of indirect air-cooled towers under different environmental temperature was studied. The results showed that, the volume flow rate of air into the indirect cooling tower under different environmental temperature is basically unchanged. With temperature rising up, the density of air reduces, which leaded to a decrease on the mass flow rate of air into tower. Besides, the trends and changing laws of performance parameters from the level of segments and the tower are achieved. What’s more, the flow traces of air and flue gas in towers were basically similar which were clearly divided by a temperature line, but the two flows always melt into a whole one at the export of towers. The conclusions would be of guide significance to the optimal operation and design of indirect air-cooled system.