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Air-cooled condensers in thermal power plants have recently become increasingly popular. Besides all the advantages they have, like no demands for water supply on the plant site and no need for taking care of environmental regulations, they also have some serious disadvantages. One of the biggest disadvantages air-cooled condensers do have is precisely the nature of the Earth's atmosphere being their low temperature reservoir. Low density and low heat capacity of the air as the cooling medium combined with extremely stochastic behavior of the atmosphere itself put some serious challenges in front of the air-cooled condenser's proper and steady functioning. In this paper, the operating parameters of the air-cooled condenser in the chosen thermal power plant were investigated to gain a clearer insight into the influence of the atmospheric changes on its entropy generation and consequently on its efficiency. Also, the acquired results were further proposed as a starting point for potential optimization of the process inside the device. [ABSTRACT FROM AUTHOR]

Wet cooling towers (WCT) are widely used to reject the unutilized heat in coal thermal power plants (TPPs). But this comes at the cost of excessive water consumption. Adoption of air-cooled condensers (ACC), also known as dry cooling systems, in all proposed Indian TPPs would reduce their water consumption by 26% in 2030. However, power producers are reluctant to install ACC due to technical and economic disadvantages such as high capital investment and land footprint. This study evaluates the major challenges in implementing ACC by quantifying them in terms of cost of electricity generation. Critical parameters of WCT and ACC, such as water and auxiliary consumption, are also estimated at varying ambient air conditions. The study shows that cost of electricity generation in TPPs with ACC would increase by 0.26–0.30 INR/kWh (0.37–0.42 US cents/kWh) compared to those TPPs with WCT. Despite this, installation of ACC would still be economically viable for those TPPs that are susceptible to at least 1 month of shutdown annually due to water shortages. On an average, Indian plants that are located at high water-stressed regions operate 1.5 months lesser than those at low and medium water-stressed regions. Such TPPs would see an increase in cost of electricity generation by 0.17 INR/kWh (0.24 US cents/kWh) compared to TPPs with ACC. [ABSTRACT FROM AUTHOR]

Many economic and environmental restrictions have resulted in the growth of dry cooling technology. The air-cooled condenser (ACC), which can be used in power plants and other facilities, represents a way toward the minimisation of the water footprint. In the paper, a semi-empirical computational tool devised for the design and thermal assessment of the ACC is introduced. In comparison to commonly used CFD-based models, the presented tool is computationally effective and inexpensive. The model is based on a control-volume computational grid, which is coupled with three sub-models for the solution of steam-side, air-side, and fan-related phenomena. A number of empirical correlations collected in the literature review were incorporated in the model. Besides the underlying functionality, which includes the determination of the steam condensation capacity, the model allows for the consideration of advanced physical phenomena such as the condensate glut control and the influence of air in the steam to the condensation process. The comparison of the model with datasheets from manufacturers of ACCs as well as with experimentally gained data from a municipal solid waste incineration plant demonstrates that the semi-empirical model is a fast and accurate tool applicable for the design and thermal assessment of the ACC. [ABSTRACT FROM AUTHOR]

Ambient winds may deteriorate the thermo-flow performances of air-cooled condenser (ACC) in power plants, so it is of benefit to the energy efficient operation of ACC to propose measures against adverse wind effects. In this work, the air deflectors installed under the fan platform of ACCs are proposed on the basis of a 2 × 300 MW direct dry cooling power plant. The flow and temperature fields of cooling air are obtained and analyzed for the air deflectors with various geometric parameters. The air mass flow rate and turbine back pressure are computed and compared with the original ACCs. The results show that the thermo-flow performances of ACCs are significantly influenced by the width, pitch, inclination angle and number of air deflectors, and get improved due to the restrained reverse flows in windward condenser cells. In most cases, the wide and more air deflectors are preferred, but the moderate pitch is recommended to improve the ACC performances. Moreover, the 45° inclination of air deflectors is superior to others in restraining the adverse wind effects. [ABSTRACT FROM AUTHOR]

An updraft tower cooling system is assessed for elimination of water use associated with power plant heat rejection. Heat rejected from the power plant condenser is used to warm the air at the base of an updraft tower; buoyancy-driven air flows through a recuperative turbine inside the tower. The secondary loop, which couples the power plant condenser to a heat exchanger at the tower base, can be configured either as a constant-pressure pump cycle or a vapor compression cycle. The novel use of a compressor can elevate the air temperature in the tower base to increases the turbine power recovery and decrease the power plant condensing temperature. The system feasibility is evaluated by comparing the net power needed to operate the system versus alternative dry cooling schemes. A thermodynamic model coupling all system components is developed for parametric studies and system performance evaluation. The model predicts that constant-pressure pump cycle consumes less power than using a compressor; the extra compression power required for temperature lift is much larger than the gain in turbine power output. The updraft tower system with a pumped secondary loop can allow dry cooling with less power plant efficiency penalty compared to air-cooled condensers. [ABSTRACT FROM AUTHOR]

The Kalina cycle is believed to be one of the most promising technologies for power generation from low temperature heat sources such as geothermal energy. So far, most Kalina cycle power plants are designed with a working fluid mixture having a fixed composition, and thus normally operate at a fixed condensing temperature. However, the ambient temperature (i.e., heat sink) varies over a large range as the season changes over a year, particularly in continental climates. Recently, a new concept, i.e., composition-adjustable Kalina cycle, was proposed to develop power plants that can match their condensing temperature with the changing ambient conditions, aiming at improving the cycle’s overall thermal efficiency. However, no detailed analysis of its implementation and the potential benefits under various climate conditions has been reported. For this reason, this paper carried out a comprehensive numerical research on its implementation and performance analysis under several different climate conditions. A mathematical model is firstly established to simulate the working principle of a composition-adjustable Kalina cycle, based on which a numerical program is then developed to analyse the cycle’s performance under various climate conditions. The developed numerical model is verified with some published data. The dynamic composition adjustment in response to the changing ambient temperature is simulated to evaluate its effect on the plant’s performance over a year. The results show that a composition-adjustable Kalina cycle could achieve higher annual-average thermal efficiency than a conventional one with a fixed mixture composition. However, such an improvement of thermal efficiency strongly depends on the heat source temperature, climate conditions, etc. The composition-adjusting system introduces extra capital and operation costs. The economic viability of a composition-adjustable Kalina cycle power plant depends on the balance between these extra costs and the increase of thermal efficiency. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine the influence of face-air velocity distribution of finned tube bundles on the thermal-performance of power plant Air-Cooled Condensers (ACCs) by experimental method and to explore Favorable Face-Air Velocity Distributions (FFAVDs) of the ambient cooling air inside the air-cooled cells by Computational Fluid Dynamics (CFD) method. FFAVD is a face-air velocity distribution favorable for thermo-performance of power plant ACCs. Based on experiments on a specially-constructed wind tunnel test-bed located on-site of a 1000-MW ultra-supercritical direct air-cooled power plant, it was found that face-air velocity distribution of ambient cooling air of finned tube bundles used in ACCs notably affects their thermo-performance, and FFAVD s can be determined. One type of FFAVD tended to increase in the retrograde direction of tube-side turbine-exhaust-condensate flow. The face-air velocity distributions of ambient cooling air that increase in the direction of tube-side turbine-exhaust-condensate flow have an adverse effect on the thermo-performance of power plant ACCs. The existence of FFAVDs can be scientifically explained by the principle of field synergy. Experiments on an A-frame cell on the ACC employed in the 1000 MW ultra-supercritical direct air-cooled power plant showed that the face-air velocity distribution in an A-frame ACC cell has the opposite trend of an FFAVD. Therefore, one type of distributing net with the characteristics of an FFAVD is introduced. The favorable characteristics of the wind distributing net have been verified based on modelling and numerical calculation. [ABSTRACT FROM AUTHOR]

Abstract: In order to rapidly and accurately predict the velocity and temperature distributions in air cooled condenser (ACC) of direct air cooling power plant influenced by the ambient wind, reduced order models (ROMs) for two-dimensional flow and temperature fields were studied with proper orthogonal decomposition (POD) method. The velocity vector, u, turbulent kinetic energy, k, and turbulent dissipation rate, ε, were approximated through POD procedure. The improved complementary POD approach (PODc) was adopted to construct robust velocity POD models of ACC under various ambient wind velocities, then flux matching procedure (FMP) was introduced to estimate the POD mode coefficients. And that of k, ε were obtained through cubic spline interpolation. It was found that as the case differed from the system reference point was great, the advantage of PODc became obvious. Otherwise, the mean relative errors of POD solutions were smaller than that of PODc method for the cases near system reference point. By interpolating the above three variables obtained by POD/PODc method into CFD software for energy equation, the temperature distributions could be acquired with the mean relative error of 10−3–10−4. At the meanwhile, the computing time spending on the energy equation iterating could be decreased significantly compared with that of direct CFD simulations. [Copyright &y& Elsevier]

Abstract: Ambient winds may deteriorate the thermo-flow performances of air-cooled condensers, so it is of use to take measures against the adverse impacts of winds upon the air-cooled condensers in a power plant. On the basis of a 2×600MW direct dry cooling power plant, a new trapezoidal array of air-cooled condensers is proposed. The computational models of the air-side fluid and heat flows of the air-cooled condensers in a trapezoidal array at various wind speeds and in various wind directions are developed, and the velocity and temperature fields are presented by using CFD simulations. The volumetric flow rate, inlet air temperature and heat rejection for different condenser cells are obtained and compared with those of the current air-cooled condensers in the rectangular array. The results show that the reversed flows arose in the upwind condenser cells at high wind speeds disappear due to the trapezoidal array of air-cooled condensers, resulting in a lowered inlet air temperature and an increased heat rejection of the upwind condenser cells. The hot plume recirculation in the wind direction of 0° becomes very weak and only appears at one side near the main buildings. The thermo-flow performances are improved to a certain extent thanks to the trapezoidal array of air-cooled condensers. It is recommended that air-cooled condensers in a power plant take the form of trapezoidal array to restrain the adverse impacts of ambient winds. [Copyright &y& Elsevier]

Abstract: Wind-break wall is considered to be an effective way to weaken the inlet flow distortions and hot plume recirculation of air-cooled condensers in a power plant. It is of use to investigate the effects of wind-break wall configurations on the thermo-flow performances of air-cooled condensers. The physical and mathematical models of the air-side fluid and heat flows for the air-cooled condensers in a representative 2 × 600 MW direct dry cooling power plant are established with three different configurations of the wind-break wall. The volumetric flow rate and heat rejection of the air-cooled condensers are calculated and compared on the basis of the simulation results of air velocity and temperature fields at various ambient wind speeds and directions. The results show that the thermo-flow performances of the air-cooled condensers are improved by the extensions of the inner and outer walkways and elevation of the wind-break wall, especially at the wind directions ranging between 0° and 90°. The improvement thanks to the width increase of the inner or outer walkway is superior to that resulting from the elevated wind-break wall. [Copyright &y& Elsevier]

Abstract: Ambient winds may lead to poor fan performance, exhaust air recirculation and mal-distribution of the air across the tube bundles of the air-cooled condensers in a power plant. Investigations of the impacts of the ambient winds on the air-cooled condensers are key area of focus. Based on a representative 2×600MW direct dry cooling power plant, the physical and mathematical models of the air-side fluid and heat flow in the air-cooled condensers at various ambient wind speeds and directions are set up by introducing the radiator model to the fin-tube bundles. The volumetric flow rate, inlet air temperature and heat rejection for different air-cooled condensers as a whole, condenser cells and fin-tube bundles are obtained by using CFD simulation. The results show that the thermo-flow performances for the air-cooled condenser as a whole, condenser cells and heat exchanger bundles vary widely in space. The thermal performances of the air-cooled condensers, condenser cells and fin-tube bundles at the downstream are generally superior to those at the upwind. It is of use for the upwind fan regulations and the A-frame condenser cell geometric optimization to investigate the space characteristics of the thermal performance for the air-cooled condensers in a power plant. [Copyright &y& Elsevier]

Abstract: The recirculation of hot exhaust air and its dependence on wind direction was investigated as a cause of reduced efficiency in an air-cooled condenser (ACC). A method of simulating exhaust air recirculation at an ACC platform using a wind tunnel is presented, and applied to a proposed ACC addition at an existing power plant. It was found that wind speed and the height of an ACC platform have a significant impact on recirculation. Wind direction was also found to be significant, due to the interference of the buildings adjacent to the ACC platform. The mechanisms that cause recirculation are presented and analyzed, and the characteristics of the recirculating flow are described. It was found that when considering additions to existing power plants, the distance of the new ACC and power plant from the original buildings and structures has only a minor effect on the recirculation of the added ACC platform. Wind tunnel simulation is recommended in the initial design stage of new or renovated power plants with ACC systems to minimize exhaust recirculation. [Copyright &y& Elsevier]