Plant Condenser Research Articles

A Preliminary Comparative Performance Evaluation of Highly Efficient Waste-to-Energy Plants

When looking for sustainable energy systems, Waste-to-Energy plants play a relevant role. Therefore performance evaluation of these plants in order to increase their efficiency is of great relevance to the field of engineering. In the present paper, highly efficient Waste-to-Energy plants are modeled and analyzed from the thermodynamic and technological points of view. Four existing plants constructed in Amsterdam/the Netherlands, Reo Nord/Denmark, Brescia/Italy and Germany were considered. The different methods aiming at increasing the efficiency adopted in these plants have been discussed and compared by using available data in the literature. The performance evaluation was carried out using a proprietary code developed at Politecnico di Milano. A sensitivity analysis was performed to investigate the effects of the plant size, condenser pressure, oxygen content and flue gas temperature at boiler exit on the efficiency of the plants. The results show that adopting a new configuration for steam cycle increases the efficiency of the plant, thus also reducing the corrosion of boiler tubes. It is also demonstrated that the proposed configuration leads to a net lower heating value efficiency of 33%.

Corrosion of 304L Stainless Steel Tube in Power Plant Condenser

Before being put to use, a new condenser of 600 MW unit was found corrosion leakage of a large number of 304L stainless steel tubes during the water leakage test. Through field investigation, sampling, chemical composition and mechanical properties test, metallographic analysis, corrosion area surface morphology and micro area component analysis, corrosion reasons were analyzed. The main reason for corrosion is improper installation. Stainless steel tubes were polluted by rain, soil, welding slag during the installation process. Carbon steel members cut the tubes when wore tubes, and was placed in such condition for a too long time. Moreover, the electric current occurred in repair welding with water may accelerate pitting holes.

Thermal power plant efficiency enhancement with Ocean Thermal Energy Conversion

In addition to greenhouse gas emissions, coastal thermal power plants would gain further opposition due to their heat rejection distressing the local ecosystem. Therefore, these plants need to enhance their thermal efficiency while reducing their environmental offense. In this study, a hybrid plant based on the principle of Ocean Thermal Energy Conversion was coupled to a 740 MW coal-fired power plant project located at latitude 28°S where the surface to deepwater temperature difference would not suffice for regular OTEC plants. This paper presents the thermodynamical model to assess the overall efficiency gained by adopting an ammonia Rankine cycle plus a desalinating unit, heated by the power plant condenser discharge and refrigerated by cold deep seawater. The simulation allowed us to optimize a system that would finally enhance the plant power output by 25–37 MW, depending on the season, without added emissions while reducing dramatically the water temperature at discharge and also desalinating up to 5.8 million tons per year. The supplemental equipment was sized and the specific emissions reduction was estimated. We believe that this approach would improve the acceptability of thermal and nuclear power plant projects regardless of the plant location.

Comparison of power plant steam condenser heat transfer models for on-line condition monitoring

In this paper heat transfer models for large power plant condenser were examined. The goal was to develop a model capable of predicting not only the condenser pressure but the overall heat transfer coefficient. Such a model can be used for condenser condition monitoring. The results of a two-dimensional (2-D) condenser heat transfer model and single-point, zero-dimensional (0-D) model are presented together with the results from Heat Exchanger Institute (HEI) standards curves. Both 0-D and 2-D models can account for the effects of steam-side pressure drop and in a simplified manner also some effects of tube bundle geometry. For all models an experimental correction as a function of cooling water temperature was implemented to improve their accuracy. The results are presented in comparison with the measured plant data for three different tube bundle geometries, with and without the experimental correction factor. The 2-D model proved to be the most consistently accurate of the models both without the correction, and at varying steam and coolant flow with the correction applied. The results indicate significant local variation of pressure drop related effects, which the 0-D model failed to accurately predict particularly in cases of close temperature approach. In predicting the heat transfer coefficient the HEI model was the least accurate, significantly overestimating the impact of coolant flow rate change, and failing to match the measurements even with a correction applied.

COMBINED HEAT PUMP AND POWER PLANT. PART I: THERMODYNAMIC ANALYSIS

The paper presents the thermodynamic analysis of an advanced heat pump and power plant which applies a modern heat engine of the gas turbine combined cycle for both heat and power production. This new technology ensures low cost of heat and a possibility to subsidise the sale of electricity. High efficiency of heat pump is conditioned by effective heat engine and high evaporating temperature of the heat pump working fluid in power plant condenser. The developed plant scheme provides for a possibility to regulate heat capacity during winter and summer regimes. The formula developed for the calculation of the powerfulness of the heat engine presents calculations for various heat capacities in any big city with a district heating and natural gas piping. The cold wave problem is proposed to be solved by adding a supplementary boiler instead of entering into the trans-critical cycle regime of the heat pump.DOI: http://dx.doi.org/10.5755/j01.mech.19.1.3630

Thermal plume behaviour in the Kadra reservoir at Kaiga atomic power station – Part 2: studies for the case of four and six units in operation

AbstractA computational model was developed earlier for 2 units of Nuclear Power Plants (NPPs) operational at Kaiga Atomic Power Station (KAPS) to understand the thermal plume behaviour in the Kadra reservoir wherein the hot water from the plant condensers is discharged. The model was successfully validated against the site data. The same model has now been extended for analyzing the thermal plume bahaviour in case of 4 NPP units as well as 6 NPP units operational at the same site. The present paper briefly describes details of the studies along with the results of earlier study to understand the overall behavior of thermal plume in Kadra reservoir.

Numerical study of a power plant condenser tube arrangement

Abstract The flow and heat transfer performance of a power plant condenser for a 300 MW unit was numerically analyzed using a porous medium model. Three typical tube arrangements were considered. The analysis indicates that none of these three tube arrangements satisfies the Heat Exchange Institute Standards (HEI Standards) with lower overall average heat transfer coefficients in the condenser and higher back pressures. A new tube arrangement was developed based on the modeling results for the velocity, heat transfer coefficient and air mass fraction distributions in the condenser. This tube arrangement gives better condenser performance than the HEI Standards.

Study on the Time Decreasing Trend Model of Condenser Cleanness Coefficient

The fouling on the condenser water-side wall is an important factor that impacts the cleanness coefficient of condenser in the optimization of designing, operation and improvement of opening cooling water circulation system. Based on the mechanism of foul-forming, a comprehensive prediction model of fouling growth on condenser water-side wall is constructed in this paper. Through analyzing the simplified theoretical model of fouling growth, the characteristic of fouling deposit, effects of working time and cooling water velocity are discussed. Taking a 600MW supercritical steam power plant's condenser as an example, the accurate estimation and prediction of cleanness coefficient can be obtained with this model. The effects of the temperature difference and condenser pressure are analyzed at the same time, and the work conditions of water circulating with different cleanness coefficient are obtained. With the evidence of some condenser fouling growth, it can be concluded that the present model is validity and would be contributed to water circulating optimization of condenser.

A greedy algorithm for dimensionality reduction in polynomial regression to forecast the performance of a power plant condenser

Engineers and physicists agree in stating that the heat transfer rate and the cleanliness factor are good indicators of the thermal performance of a power plant condenser. Both, the heat transfer rate and the cleanliness factor depend on other physical variables such as mass flow rates, pressures and temperatures measured by several sensors in the power plant. There is no knowledge about the relationship beyond the intuition of the expert that it is polynomial, taking into account the flux and heat balances derived from the mass and energy conservation principles. Performing a common full polynomial regression of a certain degree-considering all possible monomials formed by the set of measured variables-leads to a NP-hard and NP-complete problem. Besides, it would be necessary to decide the degree of the polynomial beforehand. This paper overcomes this drawback by proposing a greedy algorithm based on polynomial stepwise regression. It previously selects relevant monomials from the set of possible ones and then performs a common polynomial regression with the relevant monomials. The method is tested on some artificial data sets and some UCI repository data sets before being applied to the power plant condenser. The results show that our method successfully outperforms other state-of-the-art learning methods, taking into account both effectiveness and efficiency.

CFD simulation of thermal discharge behaviour in the Kadra reservoir at the Kaiga atomic power station

Abstract The thermal pollution arising out of discharge of hot water from the power plant condensers into the natural water bodies such as rivers, lakes, reservoirs, oceans etc. has been a serious concern to environmentalists ever since the plants started operating world over. In the past forty to fifty years, the methods of calculations for predicting the velocity and temperature fields in the affected regions of the stagnant/flowing water bodies have undergone a significant improvement. Currently, use of Computational Fluid Dynamics (CFD) codes for performing these calculations is gaining popularity. However, several factors such as the assumed computational domain and its discretisation, the boundary conditions used, representation of hydrodynamic characteristics (laminar/turbulent, buoyant/non-buoyant), etc. have a strong influence on the accuracy of predictions by such a model. A CFD code STAR-CD has been used for analyzing the thermal plume behaviour in the Kadra reservoir at Kaiga Atomic Power Station (KAPS). The predictions from these calculations of two units in operation have been found to be in good agreement with the site data made available from earlier studies. The present paper briefly describes the model developed using STAR-CD and results obtained for the Kadra reservoir at KAPS.

THE APPLICATION OF A STEP BY STEP TECHNIQUE FOR THE PERFORMANCE PREDICTION OF THERMAL POWER PLANT SURFACE CONDENSERS

In the present work, the step by step technique is used to predict the performance of the power plant condenser. The procedure includes the calculation of pressure distribution, condensation temperature, water inlet and outlet temperature, condensation load distribution and single phase heat transfer sub-cooling. A quasi two dimensions model is applied, one in the tube water direction and the other in the vapor direction. It is applied with different operating conditions of the condenser such as operating pressure, air percentage mixed with steam, cooling water temperature and fouling factor on tube side for summer and winter seasons.The present model revealed that the fouling resistance has a great effect and plays the major part of the decline in the condenser performance. This is because it decreases the overall heat transfer coefficient and condensation rate. The performance of the condenser when the cooling water enters at the lower pass is better than the upper pass, due to the balance in the distribution of the heat transfer and the condensation rate between tube passes. The model is verified with field operating conditions of Southern Baghdad thermal power station. It has revealed that there is a good agreement between the field data and the present technique. The accuracy fell within (98) % and (89) % for the cooling water temperature prediction for summer and winter respectively, while it showed accuracy of (98) % and (99) % for the condensate exit temperature prediction for summer and winter respectively.

Titanium and super stainless steel welded tubing solutions for sea water cooled heat exchangers

Owing to its outstanding resistance to general and localised corrosion, titanium has become established as the preferred material for sea water cooled heat exchanger tubing, be it for power plant surface condensers or heat exchangers in thermal desalination plant or in the chemical and petrochemical processing industry. Periodic increases in the price of titanium have generated interest in cost effective alternatives using so called 'super alloys': highly alloyed stainless steels showing improved corrosion resistance over conventional compositions. Taking sea water cooled power plant condenser tubes as an example, the mechanical and corrosion/erosion properties of titanium are reviewed together with those of three frequently considered alternatives, UNS S31254 super austenitic alloy, and UNS S44735 and S44660 super ferritic alloys. The results of ASTM G48 pitting and crevice corrosion tests and of electrochemical studies in model sea waters are reported. The effect of heat treatment on the corrosion resistance of S44735 has also been examined. It is concluded that while titanium has a superior balance of corrosion and other properties, super alloys can provide excellent performance in service provided certain precautions are observed.

Exergy analysis of turbulent flow for tubes of power plant feed water heaters and condensers

The thermal performance of heat exchangers that are essential units in power plants can be substantially improved by a number of augmentation techniques. The entropy generation and exergy destruction rate due to the flow friction and heat transfer across temperature differences were proposed numerically to evaluate the benefits of utilisation of these techniques. Enhanced tubes with either dimples or spiral corrugations that are isothermally heated were investigated. The combination of spirally corrugated tubes with twisted tape inserts was also presented. In general, dimpled and spirally corrugated tubes and the combination of spirally corrugated tubes with a twisted tape substantially increase the percentage of temperature raise ratio and decrease the percentage of exergy destruction rate relative to smooth tubes. Increasing both the additional heat transfer area due to dimpling, and ridge height of corrugation increases the percentage of temperature raise ratio and decreases the exergy destruction rate. Also, the combination of corrugated tubes with twisted tapes is attractive as an augmentation technique based on exergy analysis, especially at low twisted tape length to inner tube diameter ratio, and high ridge height of corrugation for high Reynolds number.

The design and control on intelligent underwater cleaning robot for power plant condenser

A novel method for online steam condenser fouling cleaning is proposed in this paper. In the approach, high pressure cleaning is chosen as the main method, chemical cleaning is applied to complement and this cleaning method is achieved by a new autonomous cleaning robot. In this paper, firstly, the robot system structure is designed which consists of mechanical and electrical structure. Secondly, the distributed control system is used to improve cleaning efficiency. Based on these, the cleaning control strategy based on fuzzy-gaussian neural network is presented and the BP algorithm is adopted to train the network weights. Then, the simulation results show that the proposed control strategy has better robustness and dynamic performance than traditional fuzzy control, which can not only reduce the phenomenon of chattering in effect, but also has good robustness and dynamic performance. Hence, the control strategy is very fit for underwater robotic arm control.

Performance of low noise fans in power plant air cooled steam condensers

Axial fans are often installed in locations where the orientation and surrounding infrastructure can have a detrimental effect on the fan performance indicated by the manufacturer. This paper addresses various aspects of phenomena related to the installation of axial fans, one of these being the use of low-noise fans, and how these can be considered in the CFD performance evaluation of modern air-cooled power plant condensers.

Myth and reality of the hybrid desalination process

The paper discusses some misconceptions that have contributed to the continued use of thermal desalination processes and promotion of the hybrid desalination process for new plants being built or considered at Middle East locations. The misconceptions are examined both on the basis of fundamental thermodynamic principles and in terms of practical engineering parameters. The analysis shows that there is no economic or performance advantage in the installation of greenfield hybrid power/thermal desalination/ seawater reverse osmosis (SWRO) plants in preference to power/SWRO plants, because the latter would produce water more cheaply under all conditions and at all fuel costs, and would provide more operational flexibility than the former. The paper identifies situations where the hybrid desalination process can be fully justified: in existing power/desalination plants, where aging boilers and multistage flash (MSF) units need to be repaired or replaced, through retrofitting and repowering. In such situations, abandonment of the MSF process would result in a reduction in the power output of the plant. The paper refers to previous work which showed that the repowering of a typical existing power/desalination station with refurbishment/replacement of the MSF units, together with the addition of SWRO units, would result in a several-fold increase in the water and power output and a dramatic improvement in the fuel efficiency, without any additions to the existing seawater intake system. The paper emphasizes the importance of test stations/demonstration plants at existing power/desalination stations in the Middle East in order to obtain data and make improvements in the technology of higher temperature SWRO, with the feed obtained from the cooling water returning from the power plant condenser and the thermal desalination plant. The paper shows that the potential benefits would easily justify the investment in research and development required to validate this concept.

Deviations in Predicted Condenser Performance for Power Plants Using HEI Correction Factors: A Case Study

The Heat Exchange Institute (HEI) Standards for Steam Surface Condensers are used to design and predict the performance of condensers for power plant applications. Since their inception, the Standards have undergone numerous changes to incorporate technological advances and revisions to various factors based on testing and operating experiences. Admiralty and copper-nickel (CuNi) tubes were very popular until the 1970s. Subsequently, increasing concerns with the use of copper-based alloys in nuclear power plants as well as other factors led to specification and use of stainless steel (SS) and titanium. The first condenser designed with titanium tubes was put into service in 1977. In 1978, the HEI published the seventh edition of the HEI Standards for Steam Surface Condensers. The eighth edition was issued in 1984 followed by Addendum 1 in 1989. The ninth edition was issued in 1995 and Addendum 1 to the ninth edition was published in 2002. Notable differences between the ninth and seventh editions include higher circulating water inlet temperature correction factors below 70.0°F; for Admiralty, higher tube material and gauge correction factors for tube wall gauge below 16 Birmingham wire gauge (BWG) and lower values above 20 BWG; for 90∕10 CuNi and 304 SS, higher tube material and gauge correction factors for tube wall gauge between 12 BWG and 24 BWG; and for titanium, higher tube material and gauge correction factors for tube wall gauge above 18 BWG. Depending upon the tube diameter, material, wall gauge, and the correction factors used for a specific condenser application and its operating range, there could be substantial deviations in predicted condenser performance and associated impact on output. Using a case study, this paper examines the use of the correction factors from the seventh and ninth editions in power plant condenser performance predictions. It provides recommendations for developing proper benchmarks and for ensuring optimum condenser performance.

A Computational Method for Compressible Flows with Condensation in Power Plant Condensers

The computational method for compressible flows with condensation was developed. Condensation was formulated by two thermodynamic equations of state for pressure and energy. These equations of state were simultaneously solved with the Euler equation and heat transfer equations. A finite volume method based on an approximate Riemann solver was adopted to solve the Euler equation. The computational method was applied to compressible flows in the condenser and the turbine exhaust hood. The flow regime changed widely from subsonic flow to transonic one during a small decrease of cooling water temperature. Subcooling temperature from the annulus of the turbine blades to the condensate in the hot well was investigated. Results showed the subcooling temperature could be reduced by using an advanced steam guide which was designed to improve diffuser performance under widely changed conditions. Further improvement of the steam turbine system will be pursued by the presented method.

Finite Element Solution of Navier-Stokes Equations for Steam Flow and Heat Transfer

Computational simulation of steam flow and heat transfer in power plant condensers on the basis of the three- dimensional mathematical model for the flow through porous media is presented. In order to solve the mathematical model of steam flow and heat transfer in power plant condensers, the Streamline Upwind Petrov-Galerkin finite element method is applied. By comparison of the results of simulation with experimental results about an experimental condenser, it is confirmed that SUPG finite element method can be successfully applied for solving the three-dimensional mathematical model of steam flow and heat transfer in power plant condensers. HERE are numerous papers and reports concerning numerical simulation of steam flow and heat transfer in power plant condensers. In most of the papers the simulations are mainly based on the mathematical model which defines steam flow in the tube bundle as flow through porous media. The common characteristic of the most of the current works on this subject is solving the mathematical model on the basis of finite volume method with use a rectangular grid for discretization of the condenser area. Although this methods so far have shown good results in solving the mathematical model of steam flow and heat transfer in power plant condensers, the difficulties still remain in applying the rectangular grid for discretization of the condensers flow area, especially in modern condensers with complex irregular geometry. In this paper in order to solve the mathematical model of steam flow and heat transfer in power plant condensers, the finite element method is applied.

Analysis of the Leibstadt power plant condensate and feedwater systems during selected operational transients

This paper presents a selection of plant analyses that were carried out by PSI in support of the Leibstadt Nuclear Power Plant (Swiss boiling water reactor). The analyses were performed as part of a collaboration between Leibstadt and PSI, to help resolve some operational problems that were experienced during the power uprate beginning in 1998. The issues under investigation were related to the behavior of the condensate and feedwater systems during transients initiated by a turbine trip, load rejection and a single feedwater pump trip, all of which increased the risk of an inadvertent reactor shutdown by reaching reactor pressure vessel water level limits. The possibility of a reactor shutdown was related to perturbations in the feedwater flow caused by transitory pump cavitation of the feedwater pumps, due to a rapid depressurization in the feedwater tank. In addition to a direct analysis of plant measurement provided by Leibstadt, steady-state and transient simulations of the events were performed at PSI using the system codes TRAC-BF1 and TRACE. Through a combination of the analysis of the plant measurements, the code simulations and an analysis of the whole plant behavior using the Leibstadt plant-simulator appropriate modifications of the plant hardware, control system and operational set points were proposed. The implementation and success of these changes were verified by a number of plant tests. Finally, the original designed plant capability not to shutdown during the aforementioned transients was demonstrated.