scholarly journals CFD Modeling Analysis of Mechanical Draft Cooling Tower

2008 ◽  
Author(s):  
Si Y. Lee ◽  
James S. Bollinger ◽  
Alfred J. Garrett ◽  
Larry D. Koffman
Keyword(s):  
Water Droplet ◽  
Cooling Tower ◽  
Waste Heat ◽  
National Laboratory ◽  
Ambient Air ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Test Results ◽  
Savannah River ◽  
The Impact

Industrial processes use mechanical draft cooling towers (MDCT’s) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has a MDCT consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to conduct a parametric study for cooling tower performance under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model to achieve the objective. The model uses three-dimensional momentum, energy, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of the modeling calculations was performed to investigate the impact of ambient and operating conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was benchmarked against the literature data and the SRS test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed modeling and test results will be presented here.

scholarly journals Performance Analysis for Mechanical Draft Cooling Tower

2009 ◽  
Author(s):  
Si Y. Lee ◽  
James S. Bollinger ◽  
Alfred J. Garrett ◽  
Larry D. Koffman
Keyword(s):  
Water Droplet ◽  
Cooling Tower ◽  
Waste Heat ◽  
National Laboratory ◽  
Ambient Air ◽  
Savannah River ◽  
Ambient Conditions ◽  
Integral Test ◽  
Counter Current ◽  
The Impact

Industrial processes use mechanical draft cooling towers (MDCT’s) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has cross-flow and counter-current MDCT’s consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to simulate the cooling tower performance for the counter-current cooling tower and to conduct a parametric study under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model and performed the benchmarking analysis against the integral measurement results to accomplish the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of parametric calculations was performed to investigate the impact of wind speeds and ambient conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was also benchmarked against the literature data and the SRS integral test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be published here.

scholarly journals Comparative Study of the Heat and Mass Transfer Characteristics between Counter-Flow and Cross-Flow Heat Source Towers

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2674 ◽  
Author(s):  
Yifei Lv ◽  
Jun Lu ◽  
Yongcai Li ◽  
Ling Xie ◽  
Lulu Yang ◽  
...  
Keyword(s):  
Heat Source ◽  
Cross Flow ◽  
Ambient Air ◽  
Packing Material ◽  
Operating Conditions ◽  
Solution Temperature ◽  
Low Grade ◽  
Counter Flow ◽  
Heat Pump Unit ◽  
The Impact

The heat source tower (HST), as a cleaner energy production, which can absorb the low-grade energy from ambient air to drive the heat pump unit without emissions has attracted more and more interest. In addition, HST has excellent economic applicability by using cooling tower equipment, which was idle in winter. However, there are few studies on comparative analysis of thermal behavior between counter-flow and cross-flow HST. A mathematical model suitable for both HST types was developed to identify the performance discrepancies between them. Then a parametric study was carried out in order to investigate the impact of solution and air as well as packing material properties on energy transfer of HSTs. Finally, the characteristics of solution dilution and dehumidification were investigated. As the inlet solution temperature increases, increases first, then decreases gradually, but a transition point occurs in the solution at −5 °C. Moreover, the transition section of moisture transfer direction for counter-flow HST was located in the 0.78 m and 0.26–1.56 m of packing material height, under the condition that the air relative humidity was 50%. In summary, this work intuitively indicates the thermal performance difference between counter-flow and cross-flow HST, also could assist the selection of proper operating conditions in HSTs.

Effects of Operating Conditions on the Heat Management of a Microscale Fuel Cell

2019 ◽  
Author(s):  
Liyong Sun ◽  
Adam S. Hollinger ◽  
Jun Zhou
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Waste Heat ◽  
Heat Removal ◽  
Current Collector ◽  
Ambient Air ◽  
Operating Conditions ◽  
Heat Management ◽  
Fuel Flow ◽  
Fuel Stream

Abstract Higher energy densities and the potential for nearly instantaneous recharging make microscale fuel cells very attractive as power sources for portable technology in comparison with standard battery technology. Heat management is very important to the microscale fuel cells because of the generation of waste heat. Waste heat generated in polymer electrolyte membrane fuel cells includes oxygen reduction reaction in the cathode catalyst, hydrogen oxidation reaction in the anode catalyst, and Ohmic heating in the membrane. A novel microscale fuel cell design is presented here that utilizes a half-membrane electrode assembly. An ANSYS Fluent model is presented to investigate the effects of operating conditions on the heat management of this microscale fuel cell. Five inlet fuel temperatures are 22°C, 40°C, 50°C, 60°C, and 70°C. Two fuel flow rate are 0.3 mL/min and 2 mL/min. The fuel cell is simulated under natural convection and forced convection. The simulations predict thermal profiles throughout this microscale fuel cell design. The exit temperature of fuel stream, oxygen stream and nitrogen stream are obtained to determine the rate of heat removal. Simulation results show that the fuel stream dominates heat removal at room temperature. As inlet fuel temperature increases, the majority of heat removal occurs via convection with the ambient air by the exposed current collector surfaces. The top and bottom current collector removes almost the same amount of heat. The model also shows that the heat transfer through the oxygen channel and nitrogen channel is minimal over the range of inlet fuel temperatures. Increasing fuel flow rate and ambient air flow both increase the heat removal by the exposed current collector surfaces. Ultimately, these simulations can be used to determine design points for best performance and durability in a single-channel microscale fuel cell.

CFD Modelling of an Electrically Trace Heated Blanket

2019 ◽  
Author(s):  
Vincent Le Toux ◽  
Stéphanie Harchambois ◽  
Geoffrey Guindeuil ◽  
Romain Vivet ◽  
François-Xavier Pasquet ◽  
...  
Keyword(s):  
Natural Convection ◽  
Full Scale ◽  
Operating Conditions ◽  
Burial Depth ◽  
Test Results ◽  
Cfd Modelling ◽  
Joule Effect ◽  
Hydrate Dissociation ◽  
Cfd Models ◽  
The Impact

Abstract The Electrically Trace Heated Blanket (ETH-Blanket) is a new offshore intervention/remediation system currently in development by TechnipFMC for the efficient remediation of plugs due to hydrates or wax in subsea production and injection flowlines. The ETH-Blanket consists of a network of heating cables placed underneath an insulation layer which is laid onto the seabed above the plugged flowline. By applying electrical power to the cables, heat is generated by Joule effect which warms up the flowline content until hydrate dissociation or wax plug remediation through softening or complete melting. As part of a Joint Industry Project (JIP) between TechnipFMC, Shell and Total, full-scale thermal testing of an ETH-Blanket prototype was carried out in Artelia facilities (Grenoble, France). This testing was performed to verify the capability of the ETH-Blanket system to increase the temperature of the fluid inside a pipe sample above a target temperature (hydrate dissociation temperature or wax disappearance temperature) for various conditions. The impact of lateral misalignment of the ETH-blanket on the pipe and of the pipe burial depth were studied. Moreover, the tests were carried out on two pipe samples, with different designs and insulation properties. CFD models of the test set-up have been built to replicate the thermal behaviour of the ETH-Blanket prototype. Once validated against the test results, the final aim of CFD modelling is to be able to calculate the performances of the system in real subsea conditions. The modelling of the prototype includes a 3D geometry of the system including the soil, natural convection of water between the ETH-blanket and the pipe sample and natural convection of fluid in the pipe sample. The present paper focuses on the CFD work performed to match the full-scale thermal test results and to predict the ETH-Blanket performances for real subsea operating conditions. It will describe the various CFD models used, the sensitivities and findings in terms of local and global heat transfer and flow effects and the comparison to the experimental data.

CFD Modeling of Solid Fluidization in a Column

2005 ◽  
Author(s):  
Si Y. Lee
Keyword(s):  
National Laboratory ◽  
Primary Objective ◽  
Cfd Modeling ◽  
Savannah River ◽  
Hydraulic Behavior ◽  
Savannah River National Laboratory ◽  
Computational Fluid Dynamics Cfd ◽  
Pass Through ◽  
River Site ◽  
Sedimentation Processes

Primary objective of the work is to model resin particles within the column during the particle fluidization and sedimentation processes and to understand hydraulic behavior for particles within column during the resin fluidization and sedimentation processes. The modeling results will assist in interpreting experimental results, providing guidance on specific details of testing design, and establishing a basic understanding of resin particle’s hydraulic behavior within the column. The model was benchmarked against the literature data and the test data conducted by Savannah River National Laboratory at Savannah River Site (SRS). A scoping analysis effort has been undertaken to address the feasibility of simulating the basic fluidization and sedimentation aspects pertinent to the resin addition/removal process considered here. The existing computational fluid dynamics (CFD) code Fluent was chosen for this effort. Both fluidization and sedimentation of granular particles (i.e., of varying sizes) were based on an Eulerian model for granular flow. A two-dimensional axial symmetrical cylindrical geometry was chosen to perform the solid-fluid simulations. The column consisted of a fluid region of 48” in diameter by 94” in height where at both the top and bottom boundaries liquid fluid could pass through, but resin particle could not (i.e., assuming screens at both ends).

Improving the energy efficiency of a 110 MW thermal power plant by low-cost modification of the cooling system

2018 ◽  
Vol 29 (2) ◽  
pp. 245-259 ◽  
Author(s):  
Milica Jović ◽  
Mirjana Laković ◽  
Miloš Banjac
Keyword(s):  
Energy Efficiency ◽  
Power Plant ◽  
Cooling Tower ◽  
Cooling System ◽  
Thermal Power ◽  
Ambient Air ◽  
Electric Power System ◽  
Operating Conditions ◽  
Cooling Towers ◽  
Tower System

The electric power system of the Republic of Serbia relies mostly on lignite-fired thermal power plants, with 70% of the total electricity generation. Most of these plants are over 30 years old, and investment in their modernization is necessary. The energy efficiency of the 110 MW coal-fired power plant in which the condenser is cooled by the mechanical draught wet cooling towers system is analyzed in this paper. Attention is primarily devoted to operating conditions of the cold end of the plant, i.e. to the interrelationship of the condenser and cooling towers. Most important parameters that affect the operation of the cooling towers system are ambient air temperature and relative humidity, specific mass flow rate, and temperature of cooled water. With the existing cooling system, the overall energy efficiency of the plant is low, especially in the summer months, even less than 30%, due to adverse weather conditions. By upgrading existing cooling tower system by adaptation of two additional cooling tower cells, overall energy efficiency can be increased by 1.5%. The cooling tower system rehabilitation investments payback period is estimated to be less than one year. Static method for economic and financial assessment is used.

Multiphase CFD Model Development for a Rotating Centrifugal Separator

2012 ◽  
Author(s):  
Daniel DeMore ◽  
William Maier
Keyword(s):  
Separation Efficiency ◽  
Fluid Dynamic ◽  
Model Development ◽  
Modeling Method ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Separation Performance ◽  
Centrifugal Separator ◽  
Wide Range ◽  
The Impact

The present paper describes the development of a Computational Fluid Dynamic (CFD) modeling approach suitable for the analysis, design, and optimization of rotating centrifugal separator stage geometries. The Homogeneous Multiple Size Group (MUSIG) model implemented in the commercial code CFX V13.0 was utilized as a basis for the CFD modeling method. The model was developed through a series of studies to understand the impact of droplet size distribution, particle coalescence, rotor/stator interface treatment, and mesh resolution on the prediction of separation efficiency for a given rotating separator geometry. This model was then validated against the OEM’s extensive in-house experimental separation testing database. The resulting CFD modeling method is shown to adequately reproduce observed trends in separation performance over a wide range of operating conditions.

CFD Modeling of Laser Guided Deposition for Direct Write Fabrication

2000 ◽  
Vol 624 ◽  
Author(s):  
J. C. Sheu ◽  
M. G. Giridharan ◽  
S. Lowry
Keyword(s):  
Particle Deposition ◽  
Laser Intensity ◽  
Ambient Pressure ◽  
Ambient Air ◽  
Deposition Process ◽  
Traverse Speed ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Direct Write ◽  
Fully Coupled

ABSTRACTA computational model for simulating laser-guided particle deposition process is described. This model solves for the transport of gas and particle phases in a fully coupled manner. The optical forces on the particles are evaluated from Mie theory based on local laser intensity. Simulations were performed for different operating conditions of laser power, ambient pressure, and substrate traverse speed. Simulations revealed potential problems such as particle deflected away from substrate due to ambient air current disturbances, substrate overheating, and optical fiber clogging. Possible solutions for these problems are discussed

Economical Optimization of Integrated Cooling Tower by Solar Energy

2009 ◽  
Author(s):  
Mohammad Hassan Panjeshahi ◽  
Lena Ahmadi ◽  
Mona Gharaie
Keyword(s):  
Solar System ◽  
Solar Energy ◽  
Cooling Tower ◽  
Waste Heat ◽  
Weather Conditions ◽  
Ambient Air ◽  
Operational Conditions ◽  
Practical Applications ◽  
Economical Analysis ◽  
Economical Optimization

Nowadays, the visible impact of releases to the ambient has become a matter of greater concern due to the awareness of environmental degradation and protection among the society. Therefore, the contribution of renewable energies as the free and clean sources can provide environment-friendly solutions. However, little attention has been paid to the practical applications of the renewables. Cooling towers are widely used in industries and commercial buildings to dissipate waste heat to the ambient environment. During unfavorable weather conditions, the exhaust of the wet cooling tower remixes with the cooler ambient air and as it cools down the excess moisture condenses in small fog droplets, creating visible plume. The generated plume sometime can extend up to few hundred meters and causes invisibility and darkness problem. In this study, solar energy is integrated into wet cooling tower to reduce the visible plume formation. In this method, optimum solar system is achieved taking into consideration the economical analysis. Also, the operational conditions of cooling tower at various environmental states have been incorporated in targeting the optimum solar system through different scenarios. Related coding in MATLAB version 7.1 is developed for computations.

Modeling and Analysis of Tier 4 Locomotives Operating in a High-Altitude Tunnel

2017 ◽  
Author(s):  
Kevin S. McElhaney ◽  
Robert Mischler
Keyword(s):  
High Altitude ◽  
Diesel Engines ◽  
Ambient Air ◽  
Operating Conditions ◽  
Tier 2 ◽  
Electric Locomotive ◽  
Design Changes ◽  
Engine Design ◽  
The Impact ◽  
Cooling And Lubrication

Tunnels represent one of the most severe operating conditions for diesel engines in diesel-electric locomotive applications, specifically for non-ventilated tunnels located at high elevation. High ambient air temperatures are observed in these tunnels due to heat rejected from the locomotive engines through the exhaust and engine cooling and lubrication systems. Engine protection algorithms cause the maximum allowable engine horsepower to be reduced due to these conditions leading to a reduction in train speed and occasionally train stall. A first law based model was developed to simulate the performance of a train pulled by GE diesel-electric locomotives equipped with medium speed diesel engines in a high altitude and non-ventilated tunnel. The model was compared against and calibrated to actual tunnel operation data of EPA Tier 2 compliant locomotives. The model was then used to study the impact of engine design changes required for EPA Tier 4 compliant locomotives, specifically the introduction of exhaust gas recirculation (EGR), on engine, locomotive, and train performance in the tunnel. Simulations were completed to evaluate engine control strategies targeting same or better train performance than the EPA Tier 2 compliant locomotive baseline case. Simulation results show that the introduction of EGR reduces train performance in the tunnel by increasing the required reduction in engine horsepower, but is slightly offset by improved performance from other engine design changes. The targeted engine and train performance could be obtained by disabling EGR during tunnel operation.

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