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.

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

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4560 ◽  
Author(s):  
Fan ◽  
Dong ◽  
Xu ◽  
Teng ◽  
Yan ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Significant Rise ◽  
Cooling Power ◽  
Air Cooling ◽  
Cooling Towers ◽  
Design Data ◽  
Cooling Performance ◽  
Ambient Wind ◽  
Hot Air ◽  
Complex Building

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.

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.

Optimization Analysis of Height and Distance for Shelter Wind Wall of High Speed Railway

2012 ◽  
Vol 588-589 ◽  
pp. 1794-1800 ◽  
Author(s):  
Kun Ye ◽  
Ren Xian Li
Keyword(s):  
Numerical Analysis ◽  
High Speed ◽  
Three Dimensional ◽  
Aerodynamic Forces ◽  
Optimization Analysis ◽  
High Speed Railway ◽  
Rolling Moment ◽  
Side Force ◽  
Wind Speeds ◽  
Simulation Results

Shelter wind wall is one of the most effective devices to reduce crosswind loads acting on trains. The height of the wall and distance between the wall and the center of railway are important factors for design and construction of wind wall. Since the wall design is related to many factors, such as train speeds, transverse wind speeds, types of the wall and so on, up to now, there are still different judgment methods in the optimal height and distance of the wall to get minimum aerodynamic forces on the train. Based on numerical analysis methods of three-dimensional viscous compressible aerodynamics equations, aerodynamic side forces and rolling moments acting on the train are analyzed. With 275 calculation models, include the straight and different radius curve railway with different heights and distances of shelter wind wall, the aerodynamic side forces and rolling moments are calculated. Simulation results show that the optimal height and distance of the wall are not the same during in straight and curve railway. And the direction of aerodynamic side force and rolling moment acting on the head and rear train may be different. The change trends of transverse forces (moments) with the height and distance of the wall are also different.

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.

High-speed brightfield 3-D imaging and 3-D image analysis of thick and overlapped cell clusters in cytological preparations

1994 ◽  
Vol 52 ◽  
pp. 218-219
Author(s):  
Robert W. Mackin
Keyword(s):  
Image Analysis ◽  
High Speed ◽  
Three Dimensional ◽  
Image Data ◽  
Ccd Camera ◽  
Objective Lens ◽  
Array Processor ◽  
Vaginal Smears ◽  
Low Contrast ◽  
Computer Controlled

This paper presents two advances towards the automated three-dimensional (3-D) analysis of thick and heavily-overlapped regions in cytological preparations such as cervical/vaginal smears. First, a high speed 3-D brightfield microscope has been developed, allowing the acquisition of image data at speeds approaching 30 optical slices per second. Second, algorithms have been developed to detect and segment nuclei in spite of the extremely high image variability and low contrast typical of such regions. The analysis of such regions is inherently a 3-D problem that cannot be solved reliably with conventional 2-D imaging and image analysis methods.High-Speed 3-D imaging of the specimen is accomplished by moving the specimen axially relative to the objective lens of a standard microscope (Zeiss) at a speed of 30 steps per second, where the stepsize is adjustable from 0.2 - 5μm. The specimen is mounted on a computer-controlled, piezoelectric microstage (Burleigh PZS-100, 68/μm displacement). At each step, an optical slice is acquired using a CCD camera (SONY XC-11/71 IP, Dalsa CA-D1-0256, and CA-D2-0512 have been used) connected to a 4-node array processor system based on the Intel i860 chip.

Effects of Three-Dimensional Pressure Gradients on High-Speed Turbulent Boundary Layers

2021 ◽  
Author(s):  
Scott J. Peltier ◽  
Brian E. Rice ◽  
Ethan Johnson ◽  
Venkateswaran Narayanaswamy ◽  
Marvin E. Sellers
Keyword(s):  
Boundary Layers ◽  
High Speed ◽  
Three Dimensional ◽  
Turbulent Boundary Layers ◽  
Pressure Gradients

Legionnaire’s disease and COVID-19: Could Legionella be acting in conjunction with the Corona virus to aggravate the COVID-19 disease?

2020 ◽  
Author(s):  
Andrew John PENDERY
Keyword(s):  
Drinking Water ◽  
Air Conditioning ◽  
Water Systems ◽  
Contaminated Water ◽  
Cooling Towers ◽  
Age Group ◽  
Corona Virus ◽  
The Usa ◽  
Legionnaire's Disease ◽  
Legionnaire’S Disease

There are some striking similarities between Legionnaire’s disease and COVID-19. Thesymptoms, age group and sex at risk are identical. The geographical distribution of both diseases is similar in Europe overall, and within the USA, France and Italy. The environmental distributions are also similar. However Legionnaire’s disease is caused by Legionella bacteria while COVID-19 is caused by the Corona virus. Whereas COVID-19 is contagious, Legionnaire’s disease is environmental. Legionella bacteria are commonly found in drinking water systems and near air conditioning cooling towers. Legionnaire’sdisease is caught by inhaling contaminated water droplets. The Legionella bacteria does not spread person to person and only causes disease if it enters the lungs.Could the Corona virus be making it easier for Legionella bacteria to enter the lungs?

Three-Dimensional Imaging through Shock-Waves at Ultra-High Speed.

2018 ◽  
Author(s):  
Yi Chen Mazumdar ◽  
Michael E. Smyser ◽  
Jeffery Dean Heyborne ◽  
Daniel Robert Guildenbecher
Keyword(s):  
Shock Waves ◽  
High Speed ◽  
Three Dimensional ◽  
Three Dimensional Imaging ◽  
Ultra High Speed
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