Performance Of Air-cooled Condenser Research Articles

Performance optimization of the air-cooling system in a coal-fired power unit based on intelligent algorithms

Air-cooled condensing technology is considered a preferred technology for thermal power generation due to the advantages of water savings. The performance of air-cooled condenser (ACC) is mainly influenced by external weather conditions and unit operation. In this paper, an artificial intelligence algorithm model is developed to predict and optimize the performance of the air-cooled condenser in advance based on long-term operational data of coal-fired power plants. A back propagation neural network algorithm is used to establish a net power output-back pressure model, and the optimal back pressure search is completed based on the established model. Finally, the average power savings of a single sample over a 30-second period was used as an indicator to evaluate the energy saving effect of optimized back pressure. The artificial intelligence analysis method not only enables the use of a large amount of operational data, but also allows effective prediction, analysis, and optimization of the performance of the air-cooled condenser, ultimately improving the overall performance of this equipment. The results indicate that: (1) when the back pressure of the unit reaches 9.25 kPa, the net power output of the unit is the highest, thus achieving the optimal back pressure; (2) by calculating the average energy savings, it can be concluded that, for a single sample over a 30-second period, the average power savings of the unit are above 7.0 kWh during the medium load period, and 5.0 kWh during the low and high load periods. Therefore, the proposed optimization method is beneficial for energy saving of the air-cooled condenser.

Evaporative pre-cooling of a condenser airflow: investigation of nozzle cone angle, spray inclination angle and nozzle location

ABSTRACT In hot and dry areas, evaporative cooling can enhance the performance of air-cooled condensers. Pre-cooling of a condenser airflow in a channel by a spray nozzle has been studied numerically. The Eulerian-Lagrangian 3D equations for two-phase flow have been discretized using the finite volume method. An experimental setup has been prepared to validate the numerical model. The effects of nozzle cone angle, spray inclination angle, and nozzle location in the channel have been investigated on the outlet air temperature, droplet evaporation rate, and spray cooling efficiency. The results represent that, between four analyzed geometrical parameters, nozzle longitudinal location is the most important parameter and the spray inclination angle has the lowest degree of importance. Spray inclination angle analysis displays that the counter-flow condition of the nozzle is more efficient than co-flow and cross-flow conditions. The case with the nozzle height of 45 cm in the duct, spray inclination angle of 180 ∘ , and nozzle cone angle of 60 ∘ is the best case. The maximum and minimum spray cooling efficiencies among the cases are about 30.5% and 21%, respectively. Hence, the nozzle geometrical parameters can affect the evaporative cooling capacity up to 45%.

Experimental Investigation of Coolant Side Characteristic on the Performance of Air-Cooled Condenser Structured by Horizontal Flattened Tube

The steam condensation process has been experimentally investigated in an air-cooled condenser (ACC). The ACC has been designed and built using a flattened cross-section horizontal tube. The flattened tube has an internal dimension of 102 mm x 12 mm with 4030 mm length. A range of vacuum operating conditions are applied to operate the ACC. In the experiments, parameters such as vacuum pressure, saturated temperature, wall tube temperature, rate of heat transfer, and local average steam heat transfer coefficient have been considered along the flow direction with the variation of cooling water temperature. The experimental results revealed that the steam saturated temperature and the related pressure decrease with the reduction of the cooling water temperature, and the temperatures of the upper and lower parts of the horizontal flattened tube. The results also showed that the local steam condensation heat transfer coefficient decreases along with the direction of the flow, but it there is incrementing with the decreasing of saturated steam temperature at a certain range of cooling water temperature.

The Effect of Windscreens and Walkways on Air-Cooled Condenser Performance and Fan Blade Dynamic Loading

Abstract This paper presents a relative comparison of the impact of cruciform screens, perimeter screens, and walkways on 3 × 6 cells forced draft air-cooled condenser's (ACC) thermal performance and dynamic fan blade loading under windy conditions. Numerical simulations were carried out for the three mitigation measures at two fan platform heights, four wind speeds, and three wind directions. The results indicate that walkways are a robust solution to ACC wind effects and offer benefits in terms of thermal performance and dynamic blade loading under all wind conditions considered. Cruciform screens offered the most effective mitigation of wind-related thermal performance deterioration under certain wind conditions, but the impact of these screens is sensitive to the wind direction. The dynamic blade loading impact of cruciform screens is variable, and these screens are not recommended for dynamic blade loading mitigation. Perimeter screens offered the most effective mitigation of dynamic blade loading and were particularly effective at high wind speeds but often exacted a penalty in terms of thermal performance at moderate to low wind speeds. The results of this study indicate that a correctly configured wind mitigation system, potentially consisting of more than one individual mechanism, could help improve thermal performance and simultaneously reduce dynamic blade loading under windy conditions resulting in a robust, wind-resistant condenser.

Data-driven forecasting with model uncertainty of utility-scale air-cooled condenser performance using ensemble encoder-decoder mixture-density recurrent neural networks

In the current work, an encoder-decoder mixture-density network (MDN) is developed using recurrent neural networks (RNN) for the prediction of utility-scale air-cooled condenser backpressure. Backpressure has a direct impact on thermal power plant generated load. The current study compares deterministic models (standard RNNs) to probabilistic models (MDN-RNNs). This is done using three datasets with increasing complexity to understand how significant the effects of plant operating parameters and ambient conditions are on the ACC back pressure. A hyperparameter search was performed to find the best encoder-decoder RNN architecture. An MDN layer was then attached to the selected architectures, to develop models capable of predicting the uncertainty. A two-layer encoder-decoder MDN-RNN model was selected and then trained with and without early stopping regularization active. The resultant models were combined using an ensemble approach. It was found that the ensemble model was able to achieve a better prediction of outliers without overfitting the data. The basic model, a standard RNN with the smallest input dimensionality achieved an average RMSE of 5.66 kPa whereas the end-to-end ensemble model (meta-MDN model trained using the highest dimensionality input) achieved an RMSE of 3.14 kPa which translate into a model accuracy increase from 68% to 82%.

Enhanced power plant air-cooled condensers using auto-fluttering reeds

Air-cooled condensers offer a pathway to decreasing the water consumption associated with electricity production, but dry-cooled plants suffer from lower efficiencies than those of conventional systems. One approach to increasing the performance of air-cooled condensers is to employ heat transfer enhancement techniques. Many enhancement devices have been proposed, but they have not been evaluated in air-cooled condensers at relevant scales. One promising low-cost air-side enhancement approach is the use of auto-fluttering reeds, which increase the vorticity of the flow and result in higher heat transfer coefficients. This work investigates the use of auto-fluttering reeds in a dry-cooled Rankine cycle power plant experimentally and numerically. The experimental results quantify the pressure drop and heat transfer characteristics of the enhanced condensers, which are then incorporated into a detailed model to assess performance at the system level. The air-cooled condenser geometry is also optimized to determine the maximum efficiency with and without the reeds. The results show that auto-fluttering reeds could improve the system performance in retrofit applications and may have some economic benefits in new dry-cooled power plants.

Influences of Lateral Double-Layered Deflectors on Cooling Performance of Air-Cooled Condenser

The cooling performance of air-cooled condenser (ACC) is susceptible to adverse impacts of ambient winds. In this work, three kinds of lateral double-layered deflectors installed under the ACC platform are proposed to weaken the unfavorable effects of cross winds. Through CFD simulation methods, the main parameters of thermo-flow performances of a 2×660 MW direct dry cooling system are obtained, by which it can be concluded that the deflectors can effectively reduce the inlet air temperatures while enhance the mass flow rates of upwind fans due to the guiding effect, especially at high wind speeds, while the improvement of cooling capacity of ACCs in the 0° wind direction is weak. The inclined-vertical deflectors are superior to others in performance improvement of ACCs for all cases, which can reduce the turbine back pressure by 12.15% when the wind speed is 12 m/s, so they can be applied to the performance enhancement of ACCs under windy conditions in practical engineering.

Effect of Air Gap on thermohydraulic performance of finned tube bundles

The air gap between the consecutive tube bundle row fins is one of the most important parameters that have not been evaluated in terms of their impact on the performance of air-cooled condensers. In this paper, the effect of this air gap on the thermo-hydraulic performance of the tube bundle air-side flow is investigated. The importance of this parameter lies in the fact that it can change the heat transfer coefficient and pressure drop in the tube bundle air-side flow. Moreover, changing the air gap will vary the overall length of the condenser and the dimensions of the main cooling system and consequently imposes a change in the costs of construction and operation. In this study, the effect of inlet air velocity on fin and ambient functioning temperature conditions is investigated at various air gaps on the thermo-hydraulic performance of the tube bundle air-side flow. The results indicate that the air gap for the proper thermo-hydraulic performance of the tube bundle air-side flow is independent of the air inlet velocity of the tube bundle and the ambient temperature conditions of the power plant. Moreover, it was found that the tube bundle air-side flow at a 1-mm air gap will have better thermo-hydraulic performance. The behavior of tube bundle air-side flow of the condenser of a 484 MW power plant was also studied. The results indicated that the tube bundle air-side flow at this state will also have better performance at a 1-mm air gap such that the overall length of the condenser in this state will increase by 1.7% compared to the state where the air gap is zero

Numerical Characterization of an Ultrasonic Mist Generator as an Evaporative Cooler

Pre-cooling of inlet air using evaporative cooling is an effective approach to enhance the performance of air-cooled condensers in air conditioning applications. Ultrasonic mist generators have emerged as a promising alternative to conventional evaporative cooling systems based on cooling pads or spray cooling. This paper presents the developed numerical model of an ultrasonic mist generator for the evaporative pre-cooling of the inlet air of the condenser in air conditioning applications. The model was validated against the experimental data obtained in a wind tunnel experimental facility. A parametric analysis including some physical variables involved in the cooling process was carried out, including the main axial air velocity, the injection air velocity and the water mass flow rate of atomized water. The dimensionless groups water-to-air mass flow and air-to-air mass flow ratios were found to most affect the average evaporative cooling efficiency. A maximum value of 0.654 was found for the studied conditions. The optimization analysis carried out shows that the operational ranges leading to the best overall performance are 5 × 10 − 4 ≤ m ˙ w / m ˙ a T ≤ 0.002 and 0.035 ≤ m ˙ a i / m ˙ a T ≤ 0.05 . Under these conditions, there is a better distribution of the water mist throughout the control section and a more homogeneous and effective evaporative cooling process.

Improving air-side heat transfer performance in air-cooled power plant condensers

One method to reduce water consumption in cooling towers for steam condensation is to use dry-cooled technologies with air as the heat rejection medium. These air-cooled systems are beneficial where water is unavailable or uneconomical, but typically result in lower power plant efficiencies. The present study investigates the application of an A-frame air-cooled condenser (ACC) with various air-side enhancements to increase dry-cooled plant performance to levels approaching wet-cooled plants. A computational model was developed to predict the air-cooled condenser performance during the summer (inlet air at 30 °C and 25% relative humidity), when air-cooled systems typically perform the worst. Parametric studies were conducted to identify optimal condenser geometries with smooth, wavy, and louvered fins. The segmented condenser model was integrated into Rankine cycle and combined cycle power plant models to determine the impact of various condenser fin geometries on overall cycle performance. While ACC designs with wavy or louvered fins improved the overall cycle efficiencies over the baseline case, it was found that a reduction in fin spacing of the conventional, smooth fins resulted in the largest improvement in cycle efficiency (1.14% increase for the Rankine cycle, and a 0.84% increase for the Combined cycle).

Data-Driven Air-Cooled Condenser Performance Assessment: Model and Input Variable Selection Comparison

This paper presents a data–driven model for the estimation of the performance of an aircooled steam condenser (ACC) with the aim to develop an efficient online monitoring, summarized by the condenser pressure (or vacuum) as Key Performance Indicator. The estimation of the ACC performance model was based on different dataset from three different combined cycle power plants with a gross power of above 380 MWe each, focusing on stationary condition of the steam turbine. The datasets include both boundary (e.g. Ambient Temperature, Wind Speed) and operative parameters (e.g. steam mass flow rate, Steam turbine power, electrical load of the ACC fans) acquired from the power plants and some derived variable as the incondensable fraction, which calculation is here proposed as additional parameter. After a preliminary sensitivity analysis on data correlation, the paper focuses on the evaluation of different ACC Condenser models: Semi-Empirical model is described trough curves typically based on steam mass flow rate (or condenser load) and the ambient temperature as main parameters. Since monitoring based on ACC design curves Semi-Empirical models, provides biased poor results, with an error of about 15%, the curves parameters were estimated basing on training data set. Other two data driven models were presented, basing on a neural network modelling and multi linear regression technique and compared on the base of the reduced number of input at first and then including aldo the other process variables in the prediction of the condenser back pressure. Estimate the parameters of the Semi-Empirical model, results in a better prediction if just steam mass flow rate and ambient temperature are available, with an error of the 7%, thanks to the knowledge contained within the “curves shapes”, with respect to linear regression (8.3%) and Neural Network models (7.6%). Higher accuracy can be then obtained by considering a larger number of operative parameters and exploiting more complex data-driven model. With a higher number of features, the neural network model has proved a higher accuracy than the linear regression model. In fact, the mean percentage error of the NN model (2.6%), in all plant operating conditions, is slightly lower than the error of the linear regression model, but presents and much lower than the mean error of the Semi-Empirical model thanks to the additional data-based knowledge.

Numerical Investigation on the Influence of Mechanical Draft Wet-Cooling Towers on the Cooling Performance of Air-Cooled Condenser with Complex Building Environment

In air-cooled power units, an air-cooled condenser (ACC) is usually accompanied by mechanical draft wet-cooling towers (MCTs) so as to meet the severe cooling requirements of air-cooling auxiliary apparatuses, such as water ring vacuum pumps. When running, both the ACC and MCTs affected each other through their aerodynamic fields. To make the effect of MCTs on the cooling performance of the ACC more prominent, a three-dimensional (3D) numerical model was established for one 2 × 660 MW air-cooling power plant, with full consideration the ACC, MCTs and adjacent main workshops, which was validated by design data and published test results. By numerical simulation, we obtained the effect of hot air recirculation (HAR) on the cooling performance of the ACC under different working conditions and the effect of MCTs on the cooling performance of the ACC. The results showed that as the ambient wind speed increases, the hot recirculation rate (HRR) of the ACC increased and changed significantly with the change of wind directions. An increase in ambient temperature can cause a significant rise in back pressure of the ACC. The exhaust of the MCTs partially entered the ACC under the influence of ambient wind, and the HRR in the affected cooling units was higher than that of the nearby unaffected cooling units. When the MCTs were turned off, the overall HRR of the ACC decreased. The presence of MCTs had a local influence on the cooling performance of only two cooling units, and then slightly impacted the overall cooling performance of the ACC, which provides a good insight into the arrangement optimization of the ACC and the MCTs.

Effects of Airflow Profile and Condensation Pressure on Performance of Air-Cooled Condensers

The effect of airflow profile and condensation pressure on the performance of air-cooled condensers is investigated experimentally. Two large, flattened-tube air-cooled steam condensers are studied. The tube lengths are 10.7 and 5.7 m, with inner dimensions of 216 × 16 mm and aluminum fins on each side of the elongated-slot cross sections. Capacity and pressure drop are measured and discussed here. All tests are performed with a horizontal tube and co-current vapor and condensate flow. Four different profiles of cross-flowing air are tested: uniform air flowing upwards, uniform air flowing downwards, and two profiles of non-uniform air flowing upwards. For the 10.7 m tube, reversing airflow direction from upwards to downwards is found to significantly increase condenser capacity. Also for the 10.7 m tube, a favorable non-uniform air-velocity profile is shown to increase capacity in comparison to a uniform air-velocity profile. Both of these performance increases are shown to be the result of matching regions of maximum heat transfer coefficient on the air and steam sides. For the 5.7 m tube, a non-uniform airflow profile is shown to have no effect on capacity. Reducing condensation pressure is shown to decrease condenser capacity for both condenser tubes.

Cooling Performance Enhancement of Air-Cooled Condensers by Guiding Air Flow

Adverse wind effects on the thermo-flow performances of air-cooled condensers (ACCs) can be effectively restrained by wind-proof devices, such as air deflectors. Based on a 2 × 300 MW coal-fired power generation unit, two types (plane and arc) of air deflectors were installed beneath the peripheral fans to improve the ACC’s cooling performance. With and without air deflectors, the air velocity, temperature, and pressure fields near the ACCs were simulated and analyzed in various windy conditions. The total air mass flow rate and unit back pressure were calculated and compared. The results show that, with the guidance of deflectors, reverse flows are obviously suppressed in the upwind condenser cells under windy conditions, which is conducive to an increased mass flow rate and heat dissipation and, subsequently, introduces a favorable thermo-flow performance of the cooling system. When the wind speed increases, the leading flow effect of the air deflectors improves, and improvements in the ACC’s performance in the wind directions of 45° and –45° are more satisfactory. However, hot plume recirculation may impede performance when the wind direction is 0°. For all cases, air deflectors in an arc shape are recommended to restrain the disadvantageous wind effects.

Improving Efficiency of Cooling Coil Chiller Units

Air Cooled condensers were first introduced in US power industry in early 1970’s, but only during last 10-15 years number of installations greatly increased largely due to growing attention being paid to environmental safety. Also, growing demand for water for both domestic and industrial use has brought an increased interest in use of Air Cooled condensers. This is a review paper which studies the performance of Air-cooled condenser under various operating conditions it is found that there is degradation in performance of air cooled condenser under high ambient temperatures and windy conditions. The heat rejection rate of ACC also depends on surface condition of fins and thus its performance is reduced due to external fouling of finned tubes due to weather conditions and by internal fouling from condensate (Ammonia corrosion). A Hybrid (dry/wet) dephlegmator achieves major enhancement in performance when ambient temperatures are high. Also shading of condensers is done for air-conditioning units to mitigate the adverse effect of high ambient temperatures due to solar radiation. Now a day’s wind walls are used to reduce the effect of high wind velocity .second option is to increase the fan speed Fin cleaning plays an important role in heat rejection. External cleaning improves air side heat transfer coefficient. In order to improve the performance of an ACC Flat tubes inclined at some angle to horizontal can also be used in place of conventional circular horizontal tubes so that an improvement in heat transfer rate occurs.

Fouling and Its Effects on Air-cooled Condensers in Split System Air Conditioners (RP-1705)

This paper describes research into the effects of air side fouling on the performance of air-cooled condensers used in unitary air-conditioning equipment. It takes a novel approach by using field-f...

Thermo-flow performance analysis of split air conditioner under high-speed winds around buildings

ABSTRACT Air-cooled condensers are predominantly used in condensing units of split air conditioning systems. These units are mostly installed on terraces or on outer walls of buildings. In case of tall buildings, the performance of air-cooled condenser is greatly affected by high-speed winds. Present work deals with a numerical study predicting the influence of high-speed winds on the performance of split air conditioning systems whose condensing units are installed on outer walls of buildings using mounting brackets. Simulation tools viz. ANSYS Fluent and VapCyc are employed in this work in order to obtain air flow and thermal characteristics of the condensing unit. Simulation results show that the thermo-flow performance of the split air conditioning system deteriorates significantly with high-speed winds due to an increase in the temperature of air entering the condensing unit and inferior air flow rates in the condensing unit. It is observed that the cooling capacity and coefficient of performance of the air conditioning system are reduced by 11% and 35%, respectively, when wind speed is 12.3 m/s in comparison with the baseline case.

Square array of air-cooled condensers to improve thermo-flow performances under windy conditions

The thermo-flow performances of air-cooled condensers (ACCs) get deteriorated severely under windy conditions for the inherent defects of rectangular array of condenser cells. In this work, a square array of ACCs is proposed to restrain the unfavorable effects of ambient winds. By means of CFD methods and experimental validation, the air variable fields, mass flow rates and total heat rejections of the ACCs with two types of arrays at different wind speeds and directions are obtained and analyzed. The results show that the reverse flow in the upwind condenser cells and hot plume recirculation of the peripheral condenser cells are both weakened for the proposed square array under windy conditions. Accordingly, the mass flow rate and total heat rejection increase a lot especially in the wind direction of −90° with a heat rejection improvement of 25.21% at the wind speed of 16 m/s, showing that the thermo-flow performances of ACCs get improved thanks to the square array of ACCs. In the absence of ambient winds, the total heat rejection of ACCs in the square array is almost the same as the conventional array.

Novel air-cooled condenser with V-frame cells and induced axial flow fans

The thermo-flow performances of air-cooled condensers (ACCs) are basically deteriorated under wind conditions, so it is of great concerns to propose the measures against the adverse wind effects on air-cooled condensers. In this work, a novel reconstruction of ACCs combined the V-frame condenser cells with the induced axial flow fans, and a modified layout of the novel ACCs for a specific wind direction are proposed based on the direct dry cooling system in a 2× 600 MW power plant. The CFD approach with a validation is applied to the performance investigation of the novel ACCs. The variable fields, mass flow rate, inlet air temperature and turbine back pressure for both the conventional and novel layouts of ACCs under different wind conditions are obtained and compared. The results show that the mass flow rates of the novel ACCs increase conspicuously compared with the conventional ACCs both in the absence and presence of winds. The flow distortions through the induced axial flow fans are greatly restrained and the inlet air temperature of the novel ACCs decreases, which lead to the improved thermo-flow performances of ACCs and reduced turbine back pressure of power generating unit.

Enhancing Turbine Output at Dry-Cooled Power Plants Using a Hybrid (Dry/Wet) Dephlegmator

ABSTRACTThis paper examines the benefits to steam turbine output of retrofitting an air-cooled steam condenser with a hybrid (dry/wet) dephlegmator (HDWD) in a coal-fired, reheat, regeneration cycle. A hybrid dephlegmator concept has been proposed and shown to provide enhanced air-cooled condenser cooling performance while consuming only a small amount of water. The hybrid dephlegmator retrofit is shown to be able to increase turbine power output by up to 10.8% in certain cases. A corresponding increase in annual energy output of 2.56% can be achieved for continuous wet operation of the hybrid dephlegmator. A likely operating scenario, where hybrid dephlegmator units are sequentially operated in wet mode in order to maintain rated turbine power output over a wide range of ambient temperatures, results in an annual energy output increase of 1.33%. Based on these results, the payback period for an HDWD retrofit is between 3 and 6 years. The hybrid dephlegmator concept offers a simple, cost-effective, and sustainable solution to the issue of reduced air-cooled condenser performance at high ambient temperatures and is capable of providing clean dispatchable power.