Power Plant Condenser Research Articles

Effect of inclination on pressure drop and flow regimes in large flattened-tube steam condensers

This paper presents an experimental study of the inclination effect on pressure drop and flow regime during condensation of steam in a large flattened tube used in air-cooled condensers (ACC) for power plants. Steam with mass flux of about 7kgm−2s−1 was condensed inside a 10.7m long, flattened test tube with inclination angle varied from horizontal up to 70°. The original full-sized steel tube was cut in half along the centerline, and the removed part was replaced by a polycarbonate window to enable simultaneous flow visualization in situ with heat transfer and pressure drop measurements. A uniform velocity profile of 2.03±0.12ms−1 was imposed on the air side to extract heat from the steam in a cross flow direction. The experimental results showed that increasing the inclination angle led to reductions of pressure drop due to the improvement in the gravity-assisted drainage of condensate inside the test tube. At such low mass fluxes, tube inclination significantly influenced the flow pattern which was observed to be a well-separated stratified flow throughout the tube at all downward inclination angles. The separated flow pattern enabled the direct measurement of void fraction, and the traditional void fraction models using the newly-defined superficial quality successfully predicted the measurements within ±10%. The experimental data were converted to reflect pressure drop in a full tube based on the model that was developed to account for the differences in tube geometry between the full and test tube at the same operating condition. A prediction of pressure drop performance of the same steam condensing system under vacuum condition was also discussed. The negative dependence of total pressure drop on inclination angle also prevailed in both converted results in atmospheric condition and the predicted ones in vacuum condition.

A fully developed flow thermofluid model for topology optimization of 3D-printed air-cooled heat exchangers

In this work, density-based topology optimization is applied to the design of the air-side surface of dry-cooled power plant condensers. A topology optimization model assuming a steady-state, thermally and fluid dynamically fully developed internal flow is developed and used for this application. The conductance of the heat exchanger is maximized for a prescribed pressure drop and prescribed air-side temperature change across the heat exchanger. Polymer with infilled thermally conducting metal filaments is considered as the heat exchanger material which allows cost effective additive manufacturing techniques to be used to fabricate the obtained designs. Parametric studies are presented that analyze the effect of the material thermal conductivity and the heat exchanger unit cell height on the system’s performance. The designs obtained from topology optimization are benchmarked against a simple optimized slot channel model in order to demonstrate the superior performance of the topology optimized designs. Thus, this work demonstrates the usefulness of topology optimization to fully exploit the design freedom afforded by additive manufacturing technologies.

The numerical and experimental study of two passes power plant condenser

The steam condenser is one of the most important element in whole power plant installation. Their proper design and operation makes a significant contribution to the efficiency of electricity production. The purpose of this article is to propose a two-dimensional mathematical model that allows modeling condenser work. In the model, the tube bundle is treated as a porous bed. The analysis has been subjected to a two passes power condenser with a capacity of 50 MW. The mathematical analysis was compared with the results of experimental studies. The average error between the model and the experiment for difference of cooling water temperatures was 5.15% and 11.60% for the first and second pass respectively. This allows to conclude that the proposed model is good enough to optimize future work of the condenser.

Optimal turbine pressure drop for solar chimney-aided dry cooling system in coal-fired power plants

In solar chimney-aided dry cooling systems, the low-grade waste heat released by condensers in coal-fired power plants heats the inlet air of solar collectors, thus improves the power output and decreases the power consumption of fans. An analytical model of this hybrid system is proposed to study the characteristics of heat transfer and fluid flow in the water-air heat transfer, solar collector, heat storage layer, draft tower, and turbines. The fitting equation of the optimal turbine pressure drop for the hybrid system is derived, and the effects of the solar collector radius and solar radiation on power outputs are discussed. Results show that the optimal turbine pressure drop is positively correlated to the solar collector radius and solar radiation. However, a critical collector radius and a critical solar radiation for the turbine configuration exist. The performance of a hybrid system integrated with a 660MW supercritical coal-fired power unit reveals that the optimization scheme proposed in this study outperforms the two schemes provided in the references.

A maintenance-focused approach to complex system design

AbstractMaintenance plays a critical role in reducing operating cost and maximizing reliability of a complex engineering system. This paper proposes a novel maintenance-focused, system-level design framework that attempts to capture the interactions between maintenance strategies and system-level design parameters overlooked in current modeling approaches. The goal of this maintenance-focused approach is to help designers better understand the interconnectedness of system architecture, choice of maintenance strategy, and uncertainties in a design. Application of the proposed design framework is demonstrated through a case example of a power plant condenser system. Results show that using an integrated approach can reveal the many nonobvious interactions between subsystems, and produce system designs that have lower life-cycle cost compared to traditional sequential design approaches.

Integrated Combined Heat and Power System Dispatch Considering Electrical and Thermal Energy Storage

Wind power has achieved great development in Northern China, but abundant wind power is dissipated, rather than utilized, due to inflexible electricity production of combined heat and power (CHP) units. In this paper, an integrated CHP system consisting of CHP units, wind power plants, and condensing power plants is investigated to decouple the power and heat production on both the power supply side and heat supply side, by incorporating electrical energy storage (EES) and thermal energy storage (TES). Then the integrated CHP system dispatch (ICHPSD) model is formulated to reach the target of reducing wind power curtailment and primary energy consumption. Finally, the feasibility and effectiveness of the proposed ICHPSD model are verified by the six-bus system, and the simulation results show that EES has a better effect on wind power integration than TES. The annual net benefits by incorporating EES and TES increase with increasing wind penetration, but they gradually approach saturation. Introducing both EES and TES can largely increase the amount of wind power integration and improve the operation efficiency of the system.

Relations for steam power plant condenser performance in off-design conditions in the function of inlet parameters and those relevant in reference conditions

In the classical approach, the effectiveness of a steam power plant condenser, being a surface-type steam–water heat exchanger, can be given as a function of an overall heat transfer coefficient, heat transfer surface area, cooling water mass flow rate, and the specific heat of water. The calculation of the overall heat transfer coefficient requires additional equations to determine the overall heat transfer coefficient from steam and water as well as Nusselt, Reynolds, and Prandtl similarity numbers. Basic geometric data of the condenser, such as tube diameter, tube wall thickness, heat exchanger length, and pitch of the tubes, also have to be taken into account. Complete geometric data of a heat exchanger are not always available, which raises further difficulties in developing a model. Hence, it is justified to provide a single equation for the steam power plant condenser effectiveness in off-design conditions (without any additional heat transfer equations) as a function of three independent parameters, such as cooling water temperature at the inlet, cooling water mass flow rate, and steam temperature, along with corresponding reference parameters (relevant under nominal operating conditions). The paper formulates two simplified equations for the steam power plant condenser effectiveness and the cooling water outlet temperature as functions of the parameters and reference conditions mentioned above. The proposed relations were verified against data obtained using a steam condenser simulator (written in Fortran), actual measurement data from a power plant, and measurement data available in the literature. One of the proposed relations is explicit but its use is limited to the range of NTU (number of transfer units) between 0.5 and 1.5. The other one is not limited to any range of NTU, but is an implicit function and has to be solved in an iterative process. The data obtained using the steam condenser simulator, actual measurement data, and data available in the literature allow the conclusion that the proposed equations provide good accuracy.

Numerical study of laminar flow and heat transfer characteristics in the fin side of the intermittent wavy finned flat tube heat exchanger

The wavy finned flat tube heat exchangers are widely used in air-cooled condensers of power plants. The flow and heat transfer characteristics in the fin side of the wavy finned flat tube heat exchanger are numerically studied and compared with experimental results. The influence of the fin spacing, the wave spacing, the wave amplitude and Reynolds number on the flow and heat transfer performances is investigated. The correlations of the Nusselt number and friction factor are obtained by fitting the numerical results. The results show that the intermittent wavy fin can significantly increase the heat transfer than straight fin. The wavy channel of the intermittent wavy finned flat tube heat exchanger can produce the longitudinal vortices and the transversal vortices. The longitudinal vortices can enhance heat transfer, but the transversal vortices appear negative effect on heat transfer. Both of the intensities of longitudinal vortices and transversal vortices do not uniquely determine Nusselt number for all configurations. The suggestions for improving the heat transfer performance in the fin-side of intermittent wavy finned flat tube are obtained. That is, the fin spacing is 3.0mm, the wave spacing is 9.5mm and the wave amplitude is 2.3mm.

Improving the energy efficiency of NPP

The objective of the present study is the analysis and assessment of potential ways for enhancing the energy efficiency of nuclear power generation.Currently used and promising advanced thermodynamic cycles of nuclear power plants in power generation are examined. Ways for enhancing parameters of working agents in the NPP steam-turbine plants are suggested. Thermodynamic assessment was made of enhancement of thermal efficiency of NPP equipped with fast reactors due to the increase of coolant temperature at the reactor core outlet and, correspondingly, the increase of temperature and pressure of steam generated by steam generator. Analysis of efficiency of utilization of waste low-potential heat at the NPP using heat pumps was performed.Contemporary level of development of machine building industry for power generation, development of high-efficiency high-temperature gas turbines and steam compressors allow addressing the possibility to achieve high conjugated parameters of steam at NPPs equipped with conventional light-water reactors without exceeding the permissible conditions for operation of reactor cores with fuel cladding made of zirconium alloys.Application of heat pumps within the cooling circuit of the main condenser of steam-turbine power plant for the purpose of enhancement of financial indicators is not justifiable. As it was demonstrated by estimation calculations, the use of heat pumps within the main condenser loop is promising only for reducing heat discharged by NPPs in the environment. Utilization using heat pumps of low-potential heat removed by equipment cooling systems is the efficient way to improve NPP efficiency. Non-productive extraction of steam from the thermal cycle of the power unit is reduced in this case which results in the additional power generation as well as reduces heat disposal in the environment.

A novel layout of air-cooled condensers to improve thermo-flow performances

Ambient winds are generally unfavorable to the thermo-flow performances of air-cooled condensers in power plants. More emphases are placed to weaken the negative effects of ambient winds, but no layout alternative of air-cooled condensers is considered. In this work, a novel vertical arrangement of air-cooled condensers is proposed on the basis of a 2×600MW direct dry cooling power plant, which can weaken the adverse wind effects and utilize the wind power to improve the cooling capacity of air-cooled condensers. By means of the CFD simulation and experimental validation, the flow and temperature fields of cooling air for the vertically arranged air-cooled condensers at ambient winds are obtained. The mass flow rate, inlet air temperature and turbine back pressure are computed and compared with the traditional air-cooled condensers. The results show that the flow rate of the novel air-cooled condensers increases conspicuously compared with the current ones both in the absence and presence of winds. In the wind directions of 60° and 90°, the off-axis flow distortions of axial flow fans are greatly weakened and the average inlet air temperature of the novel air-cooled condensers is reduced and almost equals the ambient temperature. The thermo-flow performances of the air-cooled condensers are improved, thus the turbine back pressure is reduced by the novel layout of air-cooled condensers.

P031 地熱発電所用復水器における水噴霧特性に関する研究(メカボケーション学生研究発表セッション)

P031 地熱発電所用復水器における水噴霧特性に関する研究(メカボケーション学生研究発表セッション)

스펀지 볼을 이용한 원전용 복수기 튜브 세정 시스템 개발

This study presents a development of the cleaning system in a nuclear power plant condenser. The tube cleaning system is very important equipment in a power plant condenser. Specially, removal of the fouling is a key process in the condenser tube. The objective of this study is development of a ball collector system for cleaning a condenser by using a sponge ball. This study uses CFD in order to optimize design of the ball strainer screen. Through the CFD, the implication of the ball strainer screen for static pressure distribution is examined. Results of research, this study have developed a 1/5 scale model for application to the power plant and developed a performance test equipment.

A high-temperature gas-and-steam turbine plant operating on combined fuel

A high-temperature gas–steam turbine plant (GSTP) for ultrasupercritical steam conditions is proposed based on an analysis of prospects for the development of power engineering around the world and in Russia up to 2040. The performance indicators of a GSTP using steam from a coal-fired boiler with a temperature of 560–620°C with its superheating to 1000–1500°C by firing natural gas with oxygen in a mixingtype steam superheater are analyzed. The thermal process circuit and design of a GSTP for a capacity of 25 MW with the high- and intermediate-pressure high-temperature parts with the total efficiency equal to 51.7% and the natural gas utilization efficiency equal to 64–68% are developed. The principles of designing and the design arrangement of a 300 MW GSTP are developed. The effect of economic parameters (the level and ratio of prices for solid fuel and gas, and capital investments) on the net cost of electric energy is determined. The net cost of electric energy produced by the GSTP is lower than that produced by modern combined-cycle power plants in a wide variation range of these parameters. The components of a high-temperature GSTP the development of which determines the main features of such installations are pointed out: a chamber for combusting natural gas and oxygen in a mixture with steam, a vacuum device for condensing steam with a high content of nondensables, and a control system. The possibility of using domestically available gas turbine technologies for developing the GSTP’s intermediate-pressure high-temperature part is pointed out. In regard of its environmental characteristics, the GSTP is more advantageous as compared with modern condensing power plants: it allows a flow of concentrated carbon dioxide to be obtained at its outlet, which can be reclaimed; in addition, this plant requires half as much consumption of fresh water.

Результаты экспериментально-расчетных исследований воздушного потока в цирктрассах воздушных конденсаторов паротурбинных установок

Результаты экспериментально-расчетных исследований воздушного потока в цирктрассах воздушных конденсаторов паротурбинных установок

The impact of the CO2 separation system integration with a 900 MWe power unit on its thermodynamic and economic indices

This paper presents an analysis of the thermal cycle of a supercritical 900 MWe condensing power plant which meets the “capture ready” requirements. The CO2 separation method selected for the analysis is chemical absorption using MEA (monoethanolamine) or ammonia as sorbent. The indispensable scope of the turbine system upgrade necessitated by the incorporation of the carbon dioxide separation installation is proposed. The change in indices of the power unit operation after integration with the capture installation is presented for different variants of the retrofit. If MEA is used for carbon dioxide separation, the smallest drop in electric power can be observed in the case of hard coal for added stages at the intermediate pressure part outlet. In the case of lignite, the most favourable upgrade solution in terms of the smallest drop in electric power is elimination of one low pressure part and a backpressure turbine is added at the same time. If ammonia is used as sorbent, the best upgrade solution in terms of the smallest drop in electric power is the variant with more stages added at the IP part outlet, regardless of the type of fuel. An economic analysis is conducted for the proposed variants.

대기 조건에 따른 공랭식 응축기 성능 저하 개선 연구

Air cooled condenser for power plant is used at inland area of desert or mountainous area because condenser coolant like sea water is not necessary. However, the performance of air cooled condenser is influenced by ambient condition such as wind speed and air temperature. Therefore, various devices have been designed to improve the performance of air cooled condenser. In this study, the CFD analysis for air cooled condenser was carried out according to wind speed and wind screen configuration. As wind speed increased from 3m/s to 7m/s, the fan flow rate was reduced about 15.76% and the rise of inlet air temperature was 5.55 degree of Celsius. When the suitable wind screen is equipped, the fan flow rate went up about 5.18% and inlet air temperature dropped by 2.08 degree of Celsius in comparison with original case without wind screen at 7m/s wind speed.

Research on the Surface of Nano H68 Alloy Surface Corro Sion Mechanism

Based on nanometer related theory, this paper has used H68 alloy for power plant condensers alloy surface nano mechanical polishing method, combining the related theory of materials research, the use of metallographic microscopic analysis, XRD analysis, hardness test and electrochemical corrosion test method, the correlation properties of nano surface treatment of H68 test, around the related properties of nano surface treatment H68 experiment, theoretical analysis and normative analysis, combining qualitative analysis with quantitative analysis, it has concluded that the surface nano can improve the corrosion resistance of H68 alloy in ammonia solution.

Entransy analysis of tube arrangement effect on condenser performances and its application

Condenser is a huge, complex shell-and-tube heat exchanger. It is the key auxiliary equipment in power plants whose designs have a very important influence on thermal efficiency of electric power generation. At present, power plant condensers are traditionally designed based on recommendations from previous designs and experimental results, often based on the standards developed by the Heat Exchange Institute. However, it does not take a number of factors into account, including the tube arrangement. Hence, to study the tube arrangement effect on condenser performance and to optimize/improve the condenser design are very important for energy saving. The condenser performances, such as the back pressure and venting rate, are strongly affected by the tube arrangement, and there are three irreversible processes for the fluid flow, heat transfer and mass diffusion in condenser. Borrowing from the entransy analysis method of heat transfer process, the momentum entransy analysis and mass entransy analysis were performed on the steam flow and air mass diffusion process in condenser. Adopting the porous media model the momentum entransy balance equation and the air mass entransy balance equation of the steam flow were deduced, then, the relation of momentum entransy loss of the steam flow and the distributed flow and heat transfer parameters in the condenser and the relation of air mass entransy increase of the steam flow and the distributed parameters of flow, heat transfer and air mass fraction were deduced. With the two relations the effects of tube arrangement on the back pressure and the venting rate are numerically investigated. The numerical analyses on four typical condensers indicate that larger momentum entransy loss relates to larger back pressure, and larger air mass entransy increase relates to less venting rate. Based on the numerical results of the four kinds of tube arrangements 330 MW condensers, the principles for tube layout in condenser are summarized. For examples, the reasonable design of the periphery of the tube bundle, i.e., the tube bundle profile, can lead the steam more uniformly entering the tube bundle, then the back pressure can be decreased; the tube arrangement should be well designed to properly guide the steam flow so as to avoid vortex flows, and a air cooling region should be well designed to reduce the venting rate. Finally, the bionic double-tree-shaped tube bundle condenser is introduced and the performances of a 330 MW condenser with bionic double-tree-shaped tube bundle are numerically analyzed. The results indicate that the steam uniformly enters the tube bundle, the thermal parameters are mainly centripetally distributed from the tube bundle periphery to the venting channel; the well-designed auxiliary steam entering channels result in a reduction of average steam velocity, hence, a reduction of flow resistance; The non-condensed steam is deeply condensed in the gradually contracted air cooling region, which strongly reduces the venting rate. Compared with the existing four kinds of condensers, its flow and thermal performances are much better. The back pressure of the rebuilt #2 condenser of Laicheng Power Plant by using the bionic double-tree-shaped tube bundle is decreased 1.5 kPa.

A novel desalination system for utilizing waste heat contained in cooling salt water of a steam plant condenser

A novel system for utilizing low temperature heat contained in cooling sea water of a steam power plant condenser for desalination is proposed in this work. This system enables warm saline water, leaving the condenser of a steam power plant to flow through a barometer tube to a tight evaporator under vacuum where some water vapor is flashed. The produced water vapor flows to the tip of an inverted U-pipe through an entraining tube connected to the U-pipe due to the pressure difference. The required vacuum is produced by allowing fresh water to flow through the U-tube by immersing each of its two branch terminals in a holding tank full of fresh water. The water levels in the two tanks are at different heights. The brine remained in the evaporator is drained through a drainage barometric tube connecting the evaporator to a brine holding tank. The results of an analytical fluid flow and thermodynamics for predicting the proposed system performance led to infer that relatively high value of producing fresh water rate can be achieved by selecting the appropriate dimensions of the proposed system. For obtaining reasonably high produced fresh water rate (1.5–10.0kg/h) at reasonably low specific energy consumption (1.0–8.0kWh/kg) the inner diameters of the U-pipe and entraining tube are selected equal in the range 0.08–0.15m, and the diameters of the suction and drainage tubes are selected in the range 0.04–0.08m. Higher values of the produced fresh water rates can be achieved with selected diameters of suction and drainage tubes in the range 0.1–0.16m, so that any disturbances of water flow through the greater inner diameters of both the U-pipe and entraining tube are obviated, but at greater specific energy expenditure. The height difference of the two fresh water holding tanks is selected in the range of 0.1–0.16m, so that any disturbances of water flow through the U-pipe are avoided and the specific energy consumption is kept reasonably low. Right choice of the suction and drainage tube heights enables suction and draining the required rate of seawater. They lie roughly 10.1m depending on their inner diameters.

Achieving near-water-cooled power plant performance with air-cooled condensers

Power plants using air-cooled condensers suffer a 5–10% plant-level efficiency penalty compared to plants with once-through cooling systems or wet cooling towers. In this study, a model of a representative air-cooled condenser (ACC) system is developed to explore the potential to mitigate this penalty through techniques that reduce the air-side thermal resistance, and by raising the air mass flow rate. The ACC unit model is coupled to a representative baseload steam-cycle power plant model. It is found that water-cooled power-plant efficiency levels can be approached by using enhanced ACCs with a combination of significantly increased air flow rates (+68%), reduced air-side thermal resistances (−66%), and air-side pressure losses near conventional levels (+24%). Emerging heat-transfer enhancement technologies are evaluated for the potential to meet these performance objectives. The impact of ambient conditions on ACC operation is also examined, and two hybrid wet/dry cooling system technologies are explored to improve performance at high ambient temperatures. Results from this investigation provide guidance for the adoption and enhancement of air-cooled condensers in power plants.