Numerical Investigation and Performance Optimization of an Air-Cooled Steam Condenser Cell Under Ambient Conditions

2011 ◽  
Author(s):  
Weifeng He ◽  
Yiping Dai ◽  
Qingzhong Ma
Keyword(s):  
Flow Field ◽  
Performance Optimization ◽  
Ambient Air ◽  
Absolute Pressure ◽  
High Wind ◽  
Ambient Conditions ◽  
Wind Speeds ◽  
Hot Air ◽  
Porous Media Model ◽  
And Performance

Air-cooled steam condensers (ACSCs) are so sensitive to the unpredictable ambient conditions that it is quite necessary to find the mechanism how the ambient conditions get into reaction and reasonable measurements can be employed to improve the performance. The numerical model of an ACSC cell is established in the paper. The influence of the ambient conditions on the performance of the ACSC cell is investigated, and the final stable back pressure (absolute pressure) the ACSC cell operates at is forecasted. Finally, wind wall is equipped to change the flow field around the ACSC cell and the performance is optimized. Aerodynamic characteristic of the ACSC cell is simulated by employing the FAN boundary and porous media model in FLUENT. User Define Function (UDF) based on the actual steam property is loaded to simulate the condensation of the steam in the exchangers. The flow field around the ACSC cell varies with the different wind speeds and directions. As a result, the fan volumetric effectiveness and the exchanger performance both decrease under high wind speed and adverse wind direction. Wind temperature gets into reaction mainly because it changes the cold side temperature of the exchangers. Under high wind temperature, the reduced temperature difference decreases the heat transfer rate between the exhaust steam and the ambient air. The equipped wind wall successfully reduces the hot air recirculation (HAR) although the fan performance is also affected due to the gathering effect between the wind wall and heat exchangers, and the performance of the ACSC cell is significantly improved under the dual effects.

Numerical Investigation of Hot Air Recirculation in an Air-Cooled Steam Condenser Under Ambient Conditions

2011 ◽  
Author(s):  
Weifeng He ◽  
Yiping Dai ◽  
Qingzhong Ma ◽  
Danmei Xie
Keyword(s):  
Wind Speed ◽  
Power Plant ◽  
Ambient Air ◽  
Finned Tube ◽  
Ambient Conditions ◽  
Navier Stokes Equation ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Hot Air ◽  
Air Flows

Air-cooled steam condensers (ACSCs) have been extensively utilized to reject heat in modern power plant. Hot air recirculation, which implies that the heated air from the exchangers is again drawn back into the axial fans influence the performance of the ACSC. Hot air recirculation under different wind speeds and directions is numerically simulated in an ACSC of a 2×600MW air-cooled power plant with the commercial Computational Fluid Dynamics (CFD) code, FLUENT, and the performance of the ACSC is investigated. Fan boundary is applied to simulate the fan characteristics when the ambient air flows through the rotor and the source term is added to the Navier-Stokes equation to simulate the pressure loss when the air flows through the exchangers. Phase transition is involved in the simulation because the turbine exhaust condensates in the finned tube exchangers while the ambient air flows outside. As a result, user define function based on the actual steam property is applied to simulate the heat transfer course between the exhaust and the ambient air. Two different mechanisms of hot air are simulated: one is based on wind speed and the other is based on wind direction. The simulation result shows that when the wind blows in the front of the ACSC, the hot air from the heat exchanger flow out free at low wind speed while it flows into the fan in the A-frame, and reverse irrigation occurs. Recirculation rate reaches its peak value at α = 135° under the obstacle effect of the turbine and boiler houses. The hot air recirculation under ambient conditions is systematically studied in the paper, and the research results provide the reference for the design and operation of the power plant.

scholarly journals An optimized roots power machine based on negative displacement theory

2020 ◽  
pp. 256-256
Author(s):  
Yanjun Xiao ◽  
Jing Gao ◽  
Jiamin Ren ◽  
Wei Zhou ◽  
Feng Wan ◽  
...  
Keyword(s):  
Flow Field ◽  
Performance Optimization ◽  
Waste Heat ◽  
Internal Flow ◽  
Medium Temperature ◽  
Structural Improvement ◽  
Power Machine ◽  
Before And After ◽  
And Performance ◽  
Field Disturbance

Roots power machine has obvious advantages in low and medium temperature waste heat recovery. The existing roots power machine has the problem of internal flow field disturbance, which seriously affects the power generation efficiency of the power machine. In order to solve the problem of disturbance of the internal flow field of roots power machine, the traditional involute rotor roots power machine is improved, and the roots power machine based on negative displacement involute rotor is proposed. The structure model and turbulence model of roots power machine are constructed, and the internal flow field simulation of roots power machine is realized by computational fluid dynamics. The pressure contour and torque change of roots power machine before and after improvement are compared, and the experimental research on the improved structure is carried out. The results show that the intensity of flow field disturbance in the modified involute rotor roots power machine decreases, and the working performance of the roots power machine improves, which provides a reference for the structural improvement and performance optimization of roots power machine.

scholarly journals Cooling Performance Optimization of Direct Dry Cooling System Based on Partition Adjustment of Axial Flow Fans

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3179
Author(s):  
Wenhui Huang ◽  
Lei Chen ◽  
Weijia Wang ◽  
Lijun Yang ◽  
Xiaoze Du
Keyword(s):  
Wind Direction ◽  
Performance Optimization ◽  
Cooling System ◽  
Axial Flow ◽  
High Wind ◽  
Power Generating Unit ◽  
Wind Speeds ◽  
Mass Flow Rates ◽  
Computational Fluid Dynamics Cfd ◽  
Dry Cooling

Axial flow fans play key roles in the thermo-flow performance of direct dry cooling system under windy conditions, so the energy efficiency of a power generating unit can be improved by optimizing the operation strategies of the axial flow fans. In this work, various measures based on the partition adjustment of axial flow fans with constant power consumption of a 2 × 660 MW power plant are studied by computational fluid dynamics (CFD) methods. The results show that increasing the rotational speed of the windward fans is beneficial to reduce the inlet air temperature and increase the mass flow rates of the fans, which enhance the heat rejections of the air-cooled condensers, especially at high wind speeds. Moreover, the turbine back pressures for the optimal and original cases are achieved by iterative methods, with the largest drop of 2.77 kPa at the wind speed of 12 m/s for 110-case 3 in the wind direction of −90°. It is recommended to adopt 110-case 1 and 110-case 3 at low and high wind speeds, respectively, in the wind directions of 90° and −90°, while 110-case 2 is always the best choice in the 0° wind direction.

Performance Evaluation of New Designs of Wind Towers

2002 ◽  
Author(s):  
Mehdi N. Bahadori ◽  
Amir R. Pakzad
Keyword(s):  
Performance Evaluation ◽  
Natural Ventilation ◽  
Evaporative Cooling ◽  
Ambient Air ◽  
Passive Cooling ◽  
High Wind ◽  
Flow Rates ◽  
Wind Speeds ◽  
Low Wind Speeds

Wind towers are architectural designs employed for natural ventilation and passive cooling of buildings. In this study, it is shown that the performance of these towers can be improved appreciably by incorporating evaporative cooling in them. Two designs, called wetted columns and wetted surfaces, were employed, and their performances were evaluated and compared with those of the conventional towers. It is found that both designs can deliver air to the building they serve at higher flow rates and at temperatures very near the ambient air wet-bulb temperatures. In general, the wind tower with wetted columns performs better in areas with relatively high wind speeds, whereas the designs with wetted surfaces performs better in areas with no winds, or with very low wind speeds.

scholarly journals COUNTERACTING HIGH WINDS WITH LOW PRESSURE: DEVELOPMENT AND TESTING OF A NEW ROOF VENT SYSTEM

2011 ◽  
Vol 6 (4) ◽  
pp. 65-76
Author(s):  
Elizabeth Grant ◽  
James Jones
Keyword(s):  
High Speed ◽  
Performance Test ◽  
Ambient Pressure ◽  
Low Pressure ◽  
High Wind ◽  
System Failures ◽  
Wind Speeds ◽  
Pressure Development ◽  
Wind Events ◽  
And Performance

Roof system failures are common during high wind events. In locations subject to high wind conditions, membrane roofing systems must typically be either physically attached or fully adhered to the substrate or ballast may be added to weigh down the membrane. An alternative to these installation approaches could be to use aerodynamics principles such as the Bernoulli and Venturi effects to create a low-pressure region beneath the membrane roof that is lower than the ambient pressure and thus counteracts the uplifting force. A new omnidirectional vent has been designed and tested that takes advantage of these aerodynamics principles to induce low pressure under the membrane layer. This new vent operates with no moving parts and was tested in the high-speed stability wind tunnel at Virginia Tech to wind speeds up to 233 km/h. The results demonstrate that this new vent generates pressures lower than the ambient when subjected to high wind conditions. This paper presents the design principles and performance test results for this new roof vent system and other applications for roof vent technologies.

scholarly journals Evaluation of the Hot Air Recirculation Effect and Relevant Empirical Formulae Applicability for Mechanical Draft Wet Cooling Towers

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3347
Author(s):  
Haotian Dong ◽  
Dawei Wan ◽  
Minghua Liu ◽  
Tiefeng Chen ◽  
Shasha Gao ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Ambient Air ◽  
Calculation Error ◽  
Cooling Towers ◽  
Design Data ◽  
Cooling Performance ◽  
Wind Speeds ◽  
Hot Air ◽  
The Usa

Due to the hot air recirculation, the inlet air enthalpy h1 of mechanical draft wet cooling towers (MCTs) was usually greater than the ambient air enthalpy ha. To realize the cooling performance and accurate design of MCTs, this paper clarified the feasibility of the inlet air enthalpy empirical formula presented by the Cooling Technology Institute (CTI) of the USA. A three-dimensional (3D) numerical model was established for a representative power plant, with full consideration of MCTs and adjacent main workshops, which were validated by design data and published test results. By numerical simulation, the influence of different wind directions and wind speeds on hot air recirculation (HAR) and the influence of HAR on the cooling performance of the MCTs were qualitatively studied based on the concept of hot air recirculation rate (HRR), and the correction value of HRR was compared with the calculated value of the CTI standard. The evaluation coefficient ηh, representing the ratio of the corrected value to the calculated value was introduced to evaluate the applicability of the CTI formula. It was found that HAR was more sensitive to ambient crosswind, and an increase in HRR would deteriorate the tower cooling performance. When the crosswind speed increased from 0 to 15 m/s, ηh, changed from 2.42 to 80.18, and the calculation error increased accordingly. It can be concluded that the CTI empirical HRR formula should be corrected when there are large buildings around the MCTs, especially under high-speed ambient crosswind conditions.

Combustion Dynamics Monitoring Considerations for Systems With Autotuning

2018 ◽  
Author(s):  
Benjamin Emerson ◽  
Chris Perullo ◽  
Tim Lieuwen ◽  
Scott Sheppard ◽  
Jared Kee ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Best Practices ◽  
Gas Turbine ◽  
Performance Optimization ◽  
Third Party ◽  
Ambient Conditions ◽  
Combustion Dynamics ◽  
Monitoring Strategies ◽  
Plant Data ◽  
And Performance

Gas turbine autotuning systems are surfacing as a popular OEM and third party solution to minimize manual tuning for emissions compliance, combustion dynamics, and performance optimization. While these systems provide many valuable benefits, they also introduce new challenges. This paper presents a review of autotuning systems, including the general approaches, benefits, challenges, and best practices for combustion dynamics monitoring. The primary benefit of autotuning is that it provides a mostly automated solution to address operability/emissions challenges which arise due to changes in ambient conditions, fuel composition, and machine aging. The operability and emissions challenges include compliant NOx and CO, acceptable combustion dynamics levels, acceptable operability (i.e., turndown and lean blowout avoidance), and in some cases optimized performance. The overarching potential benefit of autotuning systems is their ability to address all of these issues simultaneously and continuously. The paper first presents a brief outline of the general tuning considerations for autotuning systems, with some examples from real plant data to illustrate the tuning sensitivities. It next reviews the major challenges that autotuning can introduce to combustion dynamics monitoring, such as combustor fault pattern recognition and greater consequences of instrumentation faults. Finally, the paper recommends best practices for monitoring combustion dynamics in systems with autotuning. These recommendations include what to do (and what not to do) to continue health monitoring with advanced pattern recognition software, and how to recognize the signatures of combustion dynamics instrumentation faults. This paper is directed at gas turbine operators. It presents familiar plant data to help this audience understand the core working principles of an autotuning system. This understanding is an important basis for determining when a combustion dynamics event is attributable to the operations of the autotuning system, an instrumentation fault, or combustion system hardware degradation. With this understanding established, this paper also presents a list of capabilities and best practices that should be incorporated into combustion dynamics monitoring strategies for units that use autotuning.

scholarly journals The influence of chemical parameters on the in-situ metal carbonyl complex formation studied with the fast on-line reaction apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 243-260 ◽  
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Metal Carbonyl ◽  
Ambient Air ◽  
Single Atom ◽  
Carbonyl Complex ◽  
Carbonyl Complexes ◽  
On Line ◽  
Carrier Gases ◽  
And Performance ◽  
Atom Chemistry

Abstract A new setup named Fast On-line Reaction Apparatus (FORA) is presented which allows for the efficient investigation and optimization of metal carbonyl complex (MCC) formation reactions under various reaction conditions. The setup contains a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes at a rate of a few atoms per second by its 3% spontaneous fission decay branch. Those atoms are transformed within FORA in-situ into volatile metal carbonyl complexes (MCCs) by using CO-containing carrier gases. Here, the design, operation and performance of FORA is discussed, revealing it as a suitable setup for performing single-atom chemistry studies. The influence of various gas-additives, such as CO2, CH4, H2, Ar, O2, H2O and ambient air, on the formation and transport of MCCs was investigated. O2, H2O and air were found to harm the formation and transport of MCCs in FORA, with H2O being the most severe. An exception is Tc, for which about 130 ppmv of H2O caused an increased production and transport of volatile compounds. The other gas-additives were not influencing the formation and transport efficiency of MCCs. Using an older setup called Miss Piggy based on a similar working principle as FORA, it was additionally investigated if gas-additives are mostly affecting the formation or only the transport stability of MCCs. It was found that mostly formation is impacted, as MCCs appear to be much less sensitive to reacting with gas-additives in comparison to the bare Mo, Tc, Ru and Rh atoms.

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