Power plants operating in cyclic mode, standby mode or as back up to solar and wind generating assets are required to come on line on short notice. Simple cycle power plants employing gas turbines are being designed to come on line within 10–15 minutes. Combined cycle plants with heat recovery steam generators and steam turbines take longer to come on line. The components of a combined cycle plant, such as the HRSG, steam turbine, steam surface condenser, cooling tower, circulating water pumps and condensate pumps, are being designed to operate in unison and come on line expeditiously. Major components, such as the HRSG, steam turbine and associated steam piping, dictate how fast the combined cycle plant can come on line. The temperature ramp rates are the prime drivers that govern the startup time. Steam surface condenser and associated auxiliaries impact the startup time to a lesser extent. This paper discusses the design features that could be included in the steam surface condenser and associated auxiliaries to permit quick startup and reliable operation. Additional design features that could be implemented to withstand the demanding needs of cyclic operation are highlighted.

Desalination is becoming a popular and necessary process for producing fresh water in deserts and areas across the word affected by drought. Small Modular Reactor (SMR) technology is attractive for this application because it cogenerates steam and electricity to run multiple desalination processes at once. Multi-Effect Distillation (MED) technology requires steam to evaporate fresh water, while Reverse Osmosis (RO) only requires electricity for desalination. While RO typically produces fresh water more efficiently than MED, condensate from the evaporators can be flashed and sent to an absorption chiller to produce chilled water for space cooling. This study uses a 6-effect backward feed evaporator model to analyze revenues and savings from total freshwater and chilled water produced and determine the steam pressure from the SMR and loading schedule to produce maximum revenue for the specified desalination facility. Three loading schedules were chosen for this study: base loading, day/night loading, and diurnal demand loading, and revenues were calculated by closely matching a demand of 50,000 people. Day/night loading resulted in significantly more revenue and chilled water production than the other two schedules. The coupling of RO and MED systems to a small modular reactor could result in increased revenue for a desalination plant while meeting the freshwater demands of a community.

The method of specific entropy generation (SEG) is employed to show how the thermal efficiency of a combined cycle power plant can be improved. SEG is defined as the total entropy generation rate associated with the operation of a power plant per unit flowrate of the fuel burnt in the combustor. In a recent article published in Journal of Energy Resources and Technology, it is shown that the thermal efficiency of a gas turbine cycle inversely correlates with SEG. In this work, we extend the analysis to show that the same relation between the thermal efficiency and SEG is also valid for a combined cycle. The topping cycle consists of a compressor, a combustor and a gas turbine, whereas the bottoming cycle includes a heat recovery steam generator, a steam turbine, a condenser, a deaerator, a condensate pump and a feed water pump. It is shown that the minimization of SEG is identical to the maximization of thermal efficiency. An illustrative example is presented using the SEG method to improve the efficiency of the combined cycle. The results reveal that 89% of the inefficiencies takes place in the gas turbine cycle. A modified design is then proposed to reduce the efficiency losses in the topping cycle. In the modified design, the thermal energy of the flue gases is first used in a heat exchanger to preheat the air before the combustor. The flue gases leaving the heat exchanger is then directed to the HRSG for producing steam. With this modification, the thermal efficiency and the power output of the combined cycle increase 2.7 percentage points and 20.9 kW per unit molar flowrate of the fuel. Recovering the thermal energy of the flue gases for both preheating the air and producing the steam appears to be more efficient than just producing the steam. Despite the net power production of the bottoming cycle decreases in the modified design, the overall efficiency of the combined cycle increases due to the improvement in the efficiency of the topping cycle.

Multiphase flows frequently occur in many important engineering and scientific applications, but modeling of such flows is a rather challenging task due to complex interfacial dynamics between different phases, let alone if the flow is oscillating in the porous media. Using humid air as the working fluid in the thermoacoustic refrigerator is one of the research focus to improve the thermoacoustic performance, but the corresponding effect is the condensation of humid air in the thermal stack. Due to the small sized spacing of thermal stack and the need to explore the detailed condensation process in oscillating flow, a mesoscale numerical approach need to be developed. Over the decades, several types of Lattice Boltzmann (LB) models for multiphase flows have been developed under different physical pictures, for example the color-gradient model, the Shan-Chen model, the nonideal pressure tensor model and the HSD model. In the current study, a pseudopotential Multiple-Relaxation-Time (MRT) LBM simulation was utilized to simulate the incompressible oscillating flow and condensation in parallel plates. In the initial stage of condensation, the oscillating flow benefits to accumulate the saturated vapor at the exit regions, and the velocity vector of saturated vapor clearly showed the flow over the droplets. It was also concluded that if the condensate can be removed out from the parallel plates, the oscillating flow and condensation will continuously feed the cold surface to form more water droplets. The effect of wettability to the condensation was discussed, and it turned out that by increasing the wettability, the saturated water vapor was easier to condense on the cold walls, and the distance between each pair of droplets was also strongly affected by the wettability. It’s expected that this study can be used to optimize and redesign the structure of thermal stack in order to produce more condensed water, also this multiphase approach can be extended to more complicated 3D structures.

Increasing the share of intermittent renewable energy sources in a power system poses challenges in terms of increased net load variability and maintaining grid stability and security. Operational flexibility of coal-fired power plants in China has played an essential and promising role in accommodating these nonequilibrium in the power grid. In the study, focusing on condensate throttling coupled with thermal storage tank measures, dynamic simulations of an entire 660 MW supercritical coal-fired power plant were developed via the GSE software. Then, the dynamic characteristics of main thermodynamic parameters and output power were described and compared, and operational flexibility performances of these measures were discussed. It turns out that: when condensate water flowrate decreases, the largest power ramp rate, power capacity, and energy capacity are 12.68 MW min −1 , 12.76 MW, and 1084.70 MJ, respectively, and when condensate water flowrate increases, the largest power ramp rate, power capacity, and energy capacity are −5.49 MW min −1 , −5.65 MW, and −695.94 MJ, respectively, which means condensate throttling without thermal storage tank measure is more suitable for power-up regulation than power-down regulation, but the shortest duration time is 130 s, which will restrict the operational flexibility regulation. However, coupling with thermal storage tanks, the deaerator water level can maintain a longer time. Meanwhile, at feedwater bypass 60% coupled with thermal storage tank, the largest power ramp rate, power capacity, and energy capacity are −3.62 MW min −1 , −3.81 MW, and −897.31 MJ, respectively, and at condensate water bypass 60% coupled with thermal storage tank, the largest power ramp rate, power capacity, and energy capacity are 7.74 MW min −1 , 7.88 MW, and 1829.38 MJ, respectively, and these parameter values are greater than condensate water flowrate directly increases or decreases 60%, which means condensate throttling coupling with thermal storage tanks can improve operational flexibility performances. The work is expected to reveal the performance parameters and strategies to provide detailed guidance of using turbine energy storage to improve operational flexibility of the coal-fired power plants.

Recovering the waste heat of flue gas to reduce its temperature with avoiding low-temperature corrosion is an effective way to improve the economic efficiency of coal-fired power plant. A coupled high-low energy level flue gas heat recovery system was introduced in the paper. The inlet air temperature of air preheater and the temperature of turbine condensate can be increased by using this system. Thermal economy model of the system was built based on equivalent heat drop method. The system was successfully applied in 1000MW ultra-supercritical double reheat coal-fired unit in Laiwu Power Plant of China Huaneng Group, and the operation data showed the boiler flue gas temperature was not higher than 90° C, and the coal consumption was reduced by using the system. (CSPE)

The condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long lasting wetting inhibiting surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings appropriate for use on condenser tubes in steam cycle power generation systems may soon become a reality. This work presents a nano-scale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nano-particles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemi-cylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel condenser tube materials as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.

In response to the technical challenges faced by aging plant systems and components at nuclear power plants (NPP), the Electric Power Research Institute (EPRI) has a product entitled Integrated Life Cycle Management (ILCM). The ILCM software is a quantitative tool that supports capital asset and component replacement decision-making at NPPs. ILCM is comprised of models that predict the probability of failure (PoF) over time for various high-value components such as steam generators, turbines, generators, etc. The PoF models allow the user to schedule replacements at the optimum time, thereby reducing unplanned equipment shutdowns and costs. This paper describes a mathematical model that was developed for critical heat exchangers in a power plant. The heat exchanger model calculates the probability of the tubes, shell, or internals failing individually, and then accumulates the failures across the heat exchanger sub-components. The dominant degradation mechanisms addressed by the model include stress corrosion cracking, wear, microbiologically influenced corrosion, flow accelerated corrosion, and particle-induced erosion. The heat exchanger model combines physics-based algorithms and operating experience distributions to predict the cumulative PoF over time. The model is applicable to shell and tube heat exchangers and air-to-water heat exchangers. Many different types of fluids including open cycle fresh water, closed cycle fresh water, sea water, brackish water, air, closed cooling water, steam, oil, primary water, and condensate are included. Examples of PoF over time plots are also provided for different fluid types and operating conditions.

The Ultra-high Voltage (UHV) transmission has become an important developing direction of the Internet of Energy. Aiming at the influence of the Ultra-high Voltage transmission on the steam turbine, the primary frequency control (PFC) and low-load operation of units are analyzed emphatically. A coordination principle is proposed to guide operating personnel to modify PFC parameters. First, the PFC parameters are calculated qualitatively based on the proposed principle according to the units of Zhejiang province-China. Second, as the important embodiment of the PFC ability, the PFC capacity of a unit is illustrated from the angle of control valve opening, condensate throttling and feed water bypass and the removing high-pressure heater. Third, several measures are put forward to help increase the economical efficiency and safety when units are working in low-load due to the access of UHV. Finally, the future developing directions and the problems which need to be solved are discussed. The research of the effect of the UHV transmission on the steam turbine has great significance for the application of UHV and the Internet of energy (CSPE).

The cation conductivity in water-steam cycle has been significantly increased as external heating units presented on trends in large capacity and high parameters. Real test has been carried out to demonstrate the TOC concentration in feedwater has been increased as the external heating increases. The presence of organic acid would significantly reduce the pH of the condensate and result in general corrosion, pitting and environment assisted cracking. For the cogeneration thermal power stations in which make-up water were produced with traditional ion exchange system and Integrated Membrane Technology separately, the main factors affecting cation conductivity of steam are residues of the organics in raw water and dynamic variation about bacterial reproduction in reducing environment, respectively. If gel type anion resin had been replaced with macroporous strong base anion resin, the remaining TOC in traditional ion exchange system could be significantly reduced. And if non-oxidative bactericide had been dosed before or after Ultrahigh Purity Filter, bacteria could be effectively killed. For heat-supply units, the actual rates of makeup water, denote with “N%”, are always more than the design value. So it is very important in this scenario to revise the ceiling values of TOC for makeup water, which should be divided by N, to allow that ceiling value to match the actual rate of makeup water. For drum boilers and once-through boilers which superheated steam pressure are greater than 18.3 MPa, in order to guarantee the cation conductivity (25 °C) values of feed water less than the standard of 0.10 μ S/cm, TOC values in feed water should be under 50μ g/L.

Low levels of dissolved oxygen for the condensate produced within steam surface condensers is highly desirable and an increasingly important performance metric related to the efficient operation of today’s power plants. The presence of high levels of dissolved oxygen within condensate can quickly contribute to; accelerated corrosion, the need for additional treatment requirements, increased maintenance, operational challenges and even early equipment failure. Under certain operating conditions, steam surface condensers can be expected to produce condensate with defined and/or guaranteed levels of dissolved oxygen. However, these levels can only be achieved provided certain guidelines are maintained and operational limitations are not exceeded. This is not always the case. This paper includes the latest design guidelines, operational limitations, general considerations and practical techniques for controlling and minimizing condensate dissolved oxygen levels produced within steam surface condensers.

In a horizontal feedwater heater with a partial length subcooling zone the end plate located at the entrance to the subcooling zone is the only non-welded barrier that prevents the condensing zone steam from entering the subcooling zone. The end plate is usually two or three inches thick and the tube holes in the end plate are drilled to tolerances similar to that of the tubesheet. As the steam from condensing zone tries to enter the subcooling zone it condenses in the tight spaces between the active tube and the tube hole in the end plate forming a liquid barrier that prevents further ingress of steam into the subcooling zone. With usage and wear the gap between the active tube and the tube hole in the end plate increases thereby weakening the liquid barrier. The liquid barrier is completely lost when the tubes are plugged. Steam from condensing zone enters the subcooling zone and disrupts the performance of the subcooling zone, the performance of the feedwater heater and the efficiency of the power plant. This problem is faced by all horizontal feedwater heaters with subcooling zones that are in operation in power plants worldwide. This loss of performance can be eliminated by employing the patent pending Maarky concept of “dual end plate subcooling zone with a water seal”. The “dual end plate subcooling zone with water seal” concept comprises of two end plates separated by a short distance. The gap between the two end plates is filled with condensate thereby forming a triple barrier to ingress of condensing zone steam into the subcooling zone. The performance of the subcooling zone and the longevity of the heater are preserved. This paper discusses the design of subcooling zone in present day feedwater heaters, degradation of performance of subcooling zone and the improvements brought about by the patent pending Maarky concept of “dual end plate subcooling zone with water seal”.

Low grade waste heat and water recovery using ceramic membrane, is an emerging technology which helps to increase the efficiency of boilers and gas or coal combustors in various industrial processes and conventional power plants. The tube wall of a Transport Membrane Condenser (TMC) based heat exchanger is made of a nano-porous material with high membrane selectivity which is able to extract condensate water from the flue gas in the presence of other non-condensable gases (i.e. CO2, O2 and N2). In this work, a numerical study has been carried out to investigate the effects of transversal pitches of the TMC bundle tubes on the performance of a TMC based cross flow heat exchanger. A simplified multi-species transport model is used to investigate the heat and mass transfer characteristics of a condensing combustion flue gas in a crossflow transport membrane tube bundle. Various transversal (0.4”–0.6”) and longitudinal (0.4”–0.8”) pitches were used. The numerical results revealed that the effect of transversal pitches on the outlet parameters are more pronounced.

A novel flue gas treatment system was proposed in this paper. The system integrates the low pressure economizer (LPE) with the desulphurized flue gas heater (DFGH) for both waste heat recovery of the exhaust gas and the desulphurized flue gas heating. A model for the system was established based on the equivalent enthalpy drop theory. The thermal economic comparisons among 5 feasible connection schemes for the flue gas treatment system of a 300 MW unit were executed. The parametric analyses were also performed to evaluate the effects of the outlet flue gas temperature and the condensate temperature of the DFGH. Results indicate that the optimized flue gas treatment system can improve the thermal economy and heat the desulphurized flue gas. Better thermal economy is achieved when the LPE is connected with the high energy level feed water heater, and the low pressure extraction steam is extracted for heating desulphurized flue gas. The thermal economy decreases with the increase of the outlet flue gas temperature of the DFGH while it increases slightly with the decrease of the condensate temperature of the DFGH.

Getting steam out of the ground is the first crucial step in the conversion of geothermal steam into electricity. Getting it to the turbine and making the steam flow measurement is likewise important. It is at the turbine or, more precisely, just before the turbine, that many measurements are made. Performance Acceptance Tests (PAT’s) are conducted here to ensure that the equipment provided by the turbine manufacturer is performing as specified. The need for accurate steam flow measurement is critical on the main steam line (MSL). Historically, orifice plates, venturies and averaging pitot tubes have been used with greater or lesser success and with associated challenges. Orifice plates typically have high permanent pressure losses and averaging pitot tubes have small holes on their leading edge which can plug. A different solution is needed — one that provides an accurate and repeatable measurement with low maintenance requirements. In recent testing spanning over a year of operation, it was found that an Annubar™ flowmeter, installed in the top mounted position, provided the low permanent pressure loss, and met the accuracy, repeatability and maintenance requirements of the end user. Typically, in steam applications with Annubar primary elements, conventional wisdom dictates that the Annubar primary element and transmitter be positioned below the pipe. The previously recommended orientation has a number of issues particularly with geothermal steam and its constituents (silica scale, non-condensable gases,) plus the likelihood that pockets of condensate will form and lead to metallurgical issues including stress corrosion cracking, thus shortening the life of the primary element. The installation can be further enhanced with an automated nitrogen purge system that blows nitrogen through the Annubar primary element to ensure the ports remain clear. The MSL flow measurement is critical for regulatory compliance and performance monitoring. Knowing with precision and repeatability the volumetric steam flow rate is critical. The top-mounted Annubar flowmeter with nitrogen purge system, which has been in service for more than a year, has proven to be reliable and has provided precise, repeatable measurement of steam flow.

In new Russian NPP with VVER reactor in the event of LOCA, provision is made for the use of passive heat removal system for necessary core cooling. In the case of leakage in the primary circuit this system assures the transition of steam generators to operation in the mode of condensation of the primary circuit steam coming to steam generator piping from the reactor. As a result, the condensate from the steam generators arrives to the core providing its additional cooling. The steam generator off-design condensation mode has the following features: undeveloped nucleate boiling on the horizontal tubes heated by condensing steam; natural circulation processes in the both steam generator circuits; low heat fluxes and temperature differences. The experimental study of undeveloped nucleate boiling on the single horizontal tube heated by condensing steam has been carried out in the Institute for Physics and Power Engineering. The experiments have been carried out on the GROT test facility. The heart of the test facility is the single VVER steam generator tube (length l = 10.2 m, outer diameter D = 16 mm, wall thickness d = 1.5 mm). The tube is fabricated of the original stainless steel 08Cr18Ni10Ti. The length and geometry of the test tube corresponded to that of real steam generator. The test facility was equipped with thermocouples enabling the temperatures of primary and secondary facility circuits to be controlled. The experiments were carried out at three heating steam pressures P s 1 : 0.21, 0.35, 0.55 MPa. The main task of the research was to study the pressure effect on the process of undeveloped nucleate boiling on the single horizontal tube. On the base of the results of these experiments the empirical correlations for prediction of heat transfer coefficient and heat flux were obtained. The generalizing empirical correlations obtained can be used for the substantiation of work heat-exchanging equipment of NPP with VVER reactor in the condensation mode, and also can be applied to the verification of computer codes.

In this study, a long-term corrosion tendency and metal salt effect in heating nitric acid solution on corrosion behavior of titanium-5% tantalum alloy (Ti-5Ta) in hot nitric acid condensate condition were mainly researched to discuss the aging behavior of reprocessing equipments such as evaporators made of titanium or its alloy. The hot pure nitric acid solution with continuous renewing such as the nitric acid condensate condition is severe corrosion environment for their materials because of the corrosion inhibition effect from titanium ions as corrosion products or oxidizing ions in nitric acid solution and is certainly formed in evaporator for spent nuclear fuel reprocessing. From the results of the long-term corrosion test for total 11,000 hrs, the corrosion of Ti-5Ta in the nitric acid condensate was accelerated with increase of the nitric acid concentration in the condensate (∼5.6 M). The corrosion rate was nearly constant during the immersion time and the test coupons suffered a uniform corrosion. Thus, from the viewpoints of nitric acid corrosion, the life-time of the reprocessing equipments made of titanium or its alloy will be roughly estimated based on the results of average corrosion rate in operation. It was also found that the kind and concentration of metal salt in the heating nitric acid solution gave a remarkable effect on the concentration of nitric acid vapor and the corrosion of Ti-5Ta in the hot nitric acid condensate. Most of the evaporators for reprocessing plants include metal ions in the heating nitric acid solution, so the metal salt effect is one of the corrosion factors to control the corrosion behavior of titanium alloy in condensate. The nitric acid concentration in the condensate increases by adding the metal salts in the heating nitric acid solution, in addition, the larger valence of metal ions was contributed to the increase of nitric acid concentration in the condensate. Consequently, the metal salts effect in the heating nitric acid solution accelerates the corrosion of Ti-5Ta in the nitric acid condensate. The corrosion of titanium or its alloy in nitric acid condensate condition should be carefully considered as one of severe corrosion environment in evaporators for reprocessing plant. This corrosion study would give useful information to estimate the lifetime of evaporators made of titanium alloy from the viewpoint of nitric acid corrosion.

An evaluation of the effects of geometry and water supply pressure on the void transport has been performed using RELAP5/MOD3.3 (patch03). Two different piping configurations were considered for a hypothetical nuclear power plant. The cases that were analyzed considered switchover between two different water supplies, i.e. condensate storage tank (CST) and essential service water system (SX) for a safety system that acted as the ultimate heat sink. In addition, two different pressures were considered for the pressure of SX to investigate the effect of supply water pressure on void transport. Results were interpreted based on the differences in the geometries of the piping configurations and supply water pressures.

Power plants, including nuclear power plants regularly employ tanks whose contents need to be kept isolated from atmospheric conditions. One way to satisfy these requirements is to provide a liner for the tank which completely fits the interior shape of the tank but floats on top of the tank contents when the tank contains fluid. As the volume in the tank changes, the liner or diaphragm accommodates the changes in volume by sliding along the tank walls. To allow free movement of the diaphragm, management of the gas volume above the fluid and behind the diaphragm is of prime importance. The work described in this paper elaborates on the conditions required to prevent the tank diaphragm from becoming damaged. To develop potential failure modes, the kinematics of the diaphragm and the interaction with the gas volume between the diaphragm and the tank fluid are considered in detail. The developed model is applied to the case of a condensate storage tank at Comanche Peak Nuclear Power Plant (CPNPP). Two physical scale models of the tank were constructed and tested to validate the model and allow the safe operation principles to be quantified for use in the operation of the condensate storage tank at CPNPP. The work allowed CPNPP to design appropriate periodic checks and maintenance activities to ensure the diaphragm will not be damaged due to tank volume changes while still ensuring the required water chemistry criteria for the tank contents can be met.

While 1700MW class Pressurized Water Reactor (PWR) projects like US-APWR are conducted by Mitsubishi Heavy Industry (MHI) now, the size of condenser tube bundle becomes the largest ever constructed by MHI to be accordance with the increased heat rejection rate from the turbine system. Where, it becomes difficult to ignore the condensate sub-cooling and heat transfer deterioration by condensate inundation. Therefore, we have been working on research about the practical application of large-sized condenser since 2008, and tube arrangement optimization is one of the important subjects. As suitable tube arrangement for a large-sized condenser, the proven streamlined shape tube bundle was proposed, which had been adopted in the fossil fuel power units. In the streamlined shape tube bundle, most steam condenses on tubes under horizontal or downward steam flow conditions. In large tube bundle, the heat transfer deterioration due to inundation apparently occurs. On the other hand, condensate is blown away by the horizontal steam flow, and the effect of inundation would be reduced. For the tube arrangement optimization, the accurate knowledge on heat transfer including the behavior of such condensate under the horizontal steam flow condition is essential. However, most research on steam condensation on tube bundle has been conducted for the downward steam flow but the research for horizontal steam flow condensation is very limited so far (1–5). In the present research, condensation experiments were conducted by using a horizontal tube bank containing 36 cooling tubes with 12 condensate supply tubes. Steam was horizontally supplied to the tube bank at velocities 15–27m/s at pressures of 8.8kPa. Cooling tubes were made of copper and have an outer diameter of 19.1mm and condensing length of 150mm. In order to clarify the effect of condensate inundation on condensation heat transfer in detail, local heat transfer coefficients and the condensate flow in the tube bank were measured. In this paper, we describe findings on the condensate behavior and heat transfer in horizontal flow obtained by the experiment.