scholarly journals PERFORMANCE ANALYSIS OF ALTERNATIVE COVERINGS FOR COOLING TOWERS IN BRAZILIAN CAPITALS THROUGH NUMERICAL MODELING

2017 ◽  
Vol 16 (2) ◽  
pp. 67
Author(s):  
A. C. C. Tomás ◽  
P. H. Souza ◽  
A. R. M. Primo
Keyword(s):  
Relative Humidity ◽  
Cooling Tower ◽  
Waste Heat ◽  
Heat Removal ◽  
Poor Performance ◽  
Climatic Conditions ◽  
Capital City ◽  
Inlet Temperature ◽  
Cooling Towers ◽  
Climate Conditions

A cooling tower is a heat removal device used to transfer waste heat to the atmosphere process. Today, commercial cooling towers use plastic coverings, specially developed for this application. It is known that alternative coverings have been an increasingly viable solution thanks to its performance and cost. The purpose of this study was to evaluate, through numerical simulation, the performance of different alternative coverings under different climatic conditions. Therefore, we used, as reference, the climate of the state capitals and their respective geographic regions. The performance of these coverings was evaluated through observation of three parameters: effectiveness, approach and cooling. The main input data used by the software EES (Engineering Equation Solver) for the calculation of evaluation parameters were: experimental NUT of each covering, average local temperature, local air pressure and relative humidity. The flow of water and air were set at 0.33 L / s and 170 L / s, respectively. We concluded that the air inlet temperature and relative humidity at each location greatly influence the performance of the coverings. The alternative covering that showed the best results was the "cross-fiber and neck", with an efficiency about 35% lower than the industrial covering. The Brazilian capital city with the best performances for alternative coverings was Palmas (TO). This is due to the very low relative humidity found in the city in the summer. Air humidity is also responsible for the poor performance of coverings in the capitals of the North. In general, the region with the best performance was the South, due to the characteristics of the sub-tropical climate. Regions that had the worst results were North / Northeast because of the weather that combines high temperatures with high / moderate humidity, respectively. Thus, the study of climate conditions is indispensable for the operation prevision of a cooling tower. Alternative coverings will be viable depending on the location.

Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle

2012 ◽  
Author(s):  
Thomas Conboy ◽  
Steven Wright ◽  
James Pasch ◽  
Darryn Fleming ◽  
Gary Rochau ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Waste Heat ◽  
Electrical Power ◽  
Heat Removal ◽  
Test Facility ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Compact Size ◽  
Test Loop

Supercritical CO2 (S-CO2) power cycles offer the potential for better overall plant economics due to their high power conversion efficiency over a moderate range of heat source temperatures, compact size, and potential use of standard materials in construction [1,2,3,4]. Sandia National Labs (Albuquerque, NM, US) and the US Department of Energy (DOE-NE) are in the process of constructing and operating a megawatt-scale supercritical CO2 split-flow recompression Brayton cycle with contractor Barber-Nichols Inc. [5] (Arvada, CO, US). This facility can be counted among the first and only S-CO2 power producing Brayton cycles anywhere in the world. The Sandia-DOE test-loop has recently concluded a phase of construction that has substantially upgraded the facility by installing additional heaters, a second recuperating printed circuit heat exchanger (PCHE), more waste heat removal capability, higher capacity load banks, higher temperature piping, and more capable scavenging pumps to reduce windage within the turbomachinery. With these additions, the loop has greatly increased its potential for electrical power generation — according to models, as much as 80 kWe per generator depending on loop configuration — and its ability to reach higher temperatures. To date, the loop has been primarily operated as a simple recuperated Brayton cycle, meaning a single turbine, single compressor, and undivided flow paths. In this configuration, the test facility has begun to realize its upgraded capacity by achieving new records in turbine inlet temperature (650°F/615K), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20kWe). Operation at higher speeds, flow rates, pressures and temperatures has allowed a more revealing look at the performance of essential power cycle components in a supercritical CO2 working fluid, including recuperation and waste heat rejection heat exchangers (PCHEs), turbines and compressors, bearings and seals, as well as auxiliary equipment. In this report, performance of these components to date will be detailed, including a discussion of expected operational limits as higher speeds and temperatures are approached.

scholarly journals A Study on the Carbonation Rate of Concrete Exposed in Different Climatic Conditions

2021 ◽  
pp. 128-136
Keyword(s):  
Fly Ash ◽  
Relative Humidity ◽  
Environmental Conditions ◽  
Climatic Conditions ◽  
Climate Conditions ◽  
Industrial Areas ◽  
Carbonation Process ◽  
Carbonation Resistance ◽  
Proper Design ◽  
One Year

Recently, the degradation of concrete has become a serious problem worldwide and one of the principle factors of degradation is the carbonation process. It is well established that environmental conditions affect the carbonation progress of concrete among the most important factors that can greatly affect the carbonation resistance of concrete are relative humidity (RH) and temperature. Carbonation has become a threat to concrete structures, especially in urban and industrial areas. Thus, it is necessary to have a proper design to maintain the structure's stability against degradation caused by carbonation. Therefore, this study was conducted to evaluate the effects of different environmental and climatic conditions on the carbonation rate of concrete. The specimens were prepared using OPC and fly ash (FA). After 28 days of air curing, specimens were exposed to different climate conditions under sheltered and un-sheltered conditions. The carbonation tests were conducted at the ages of 6 and 12 months. It was found that the carbonation rates were significantly influenced by the climate and environmental conditions; the specimens exposed to a relatively dry environment and low annual precipitations have shown higher carbonation during one-year exposure. Moreover, in unsheltered conditions, the annual precipitation significantly affects the carbonation rate of concrete. Furthermore, it was observed that a 20% replacement of FA does not enhance the carbonation resistance of concrete.

An analysis of operating parameters in the cooling tower-based thermally activated building system

2017 ◽  
Vol 27 (9) ◽  
pp. 1175-1186 ◽  
Author(s):  
D. G. Leo Samuel ◽  
S. M. Shiva Nagendra ◽  
M. P. Maiya
Keyword(s):  
Thermal Comfort ◽  
Cooling Tower ◽  
Climatic Conditions ◽  
Operating Parameters ◽  
Inlet Temperature ◽  
Operative Temperature ◽  
Inlet Velocity ◽  
Comfort Index ◽  
Thermally Activated ◽  
Building System

Thermally activated building system is not only energy efficient but also provides better thermal comfort compared to the conventional cooling systems. In this paper, COMSOL Multiphysics, a computational fluid dynamics tool, is used to simulate the performance of a cooling tower coupled with thermally activated building system for the hot and dry summer climatic conditions of New Delhi. The effects of three operating parameters, namely, temperature and inlet velocity of water and the number of cooling surfaces (area), on the performance of the system have been investigated. The results indicate that increasing the water inlet temperature from wet bulb temperature (WBT) to WBT + 6℃ would increase the operative temperature of the indoor space, a thermal comfort index, by 2℃. The increase in water inlet velocity from 0.2 to 1 m/s would decrease the diurnal average of operative temperature by 1.4℃. If only the roof was cooled, the diurnal average of operative temperature was 36.7℃. The diurnal average of operative temperature was reduced by 5.7℃ if all the building fabrics were cooled. In this case, with pipes connected in series from the floor first to walls and then to roof resulted in 2.9℃ lower operative temperature compared to that in the reverse sequence. Hence, the sequence in which the fabrics are cooled would have an appreciable influence on the performance of thermally activated building system.

Performance Characteristics of an Operating Supercritical CO2 Brayton Cycle

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Thomas Conboy ◽  
Steven Wright ◽  
James Pasch ◽  
Darryn Fleming ◽  
Gary Rochau ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Waste Heat ◽  
Electrical Power ◽  
Heat Removal ◽  
Test Facility ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Compact Size ◽  
Test Loop

Supercritical CO2 (S-CO2) power cycles offer the potential for better overall plant economics due to their high power conversion efficiency over a moderate range of heat source temperatures, compact size, and potential use of standard materials in construction. Sandia National Labs (Albuquerque, NM) and the U.S. Department of Energy (DOE-NE) are in the process of constructing and operating a megawatt-scale supercritical CO2 split-flow recompression Brayton cycle with contractor Barber-Nichols Inc. (Arvada, CO). This facility can be counted among the first and only S-CO2 power producing Brayton cycles anywhere in the world. The Sandia-DOE test-loop has recently concluded a phase of construction that has substantially upgraded the facility by installing additional heaters, a second recuperating printed circuit heat exchanger (PCHE), more waste heat removal capability, higher capacity load banks, higher temperature piping, and more capable scavenging pumps to reduce windage within the turbomachinery. With these additions, the loop has greatly increased its potential for electrical power generation, and its ability to reach higher temperatures. To date, the loop has been primarily operated as a simple recuperated Brayton cycle, meaning a single turbine, single compressor, and undivided flow paths. In this configuration, the test facility has begun to realize its upgraded capacity by achieving new records in turbine inlet temperature (650 °F/615 K), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20 kWe). Operation at higher speeds, flow rates, pressures, and temperatures has allowed a more revealing look at the performance of essential power cycle components in a supercritical CO2 working fluid, including recuperation and waste heat rejection heat exchangers (PCHEs), turbines and compressors, bearings and seals, as well as auxiliary equipment. In this report, performance of these components to date will be detailed, including a discussion of expected operational limits as higher speeds and temperatures are approached.

Heat Sink Issue: A Specific Problematic Issue for NPP Implementation in Warm Countries With Extreme Climatic Conditions

2012 ◽  
Author(s):  
Andrei Rodionov ◽  
Jean-Marie Mattei
Keyword(s):  
Heat Sink ◽  
Cold Water ◽  
Waste Heat ◽  
Heat Removal ◽  
Water Source ◽  
Climatic Conditions ◽  
Normal Operation ◽  
Advantages And Disadvantages ◽  
Problematic Issue ◽  
And Performance

With the nuclear renaissance, many new countries start to consider nuclear energy as a reliable, sustainable energy source and initiated their own programs for a peaceful application. One of the major issues during the site selection and design of a NPP is the heat sink issue, i.e. availability of reliable and efficient recipient of heat (air or water) in relation with: • The waste heat removal from the condenser of turbine generator during normal operation of the NPP. • The assurance of the nuclear fuel residual heat removal and safety important equipment cooling in abnormal and accidental situations. There are several newcomer countries that have extreme climatic conditions in combination with a shallow sea and absence of an important reliable cold water source inside the country (groundwater, rivers, lakes, etc.). This requires particular consideration of the heat sink issue for the siting survey and design requirements. The article discusses advantages and disadvantages of possible heat sink solutions, proposes site survey criteria and provides a list of safety and performance issues to be addressed throughout siting and design stages.

Waste Heat Disposal to Air with Mechanical and Natural Draft—Some Analytical Design Considerations

1980 ◽  
Vol 102 (3) ◽  
pp. 719-727
Author(s):  
Ali Montakhab
Keyword(s):  
Cooling Tower ◽  
Waste Heat ◽  
Cooling Towers ◽  
Large Power ◽  
Natural Draft ◽  
Power Stations ◽  
Influence Coefficients ◽  
Design Variables ◽  
Dry Cooling Tower ◽  
Dry Cooling

There is a growing acceptance of the future necessity of dry and wet/dry cooling tower systems for large power stations in spite of their economic penalty compared with once-through cooling, cooling ponds, and evaporative cooling towers. If technological improvements succeed in reducing the current costs of dry cooling towers, their future applications will be accelerated. The main objective of this work is to quantify the factors that reduce the overall size and cost of the tower and the associated heat transfer system and to provide a basis for establishing the conditions that result in dry cooling tower cost reductions. As a first-step, the design equations for forced-and natural-draft dry cooling towers are derived in close form to give explicit relations for salient design variables. Subsequently, these equations are used to establish a set of influence coefficients for quantifying the effects of various key design variables on the design of forced- and natural-draft cooling towers.

Potential Weather Modification Caused by Waste Heat Release from Large Dry Cooling Towers

1979 ◽  
Vol 101 (1) ◽  
pp. 164-168
Author(s):  
Jiin-lang Lee
Keyword(s):  
Cooling Tower ◽  
Waste Heat ◽  
Atmospheric Effects ◽  
Cooling Towers ◽  
Weather Modification ◽  
Thermal Plumes ◽  
Power Generating Unit ◽  
Generating Capacity ◽  
Order Of Magnitude ◽  
Dry Cooling

A numerical model of a cooling tower plume is employed to study the possible atmospheric effects of thermal plumes from natural draft dry cooling towers. Calculations are performed for both single and multiple towers, each of which can dissipate the waste heat from a nominal 1000 MWe power generating unit, and the results are compared with those for wet cooling towers associated with plants of the same generating capacity. Dry cooling tower plumes are found to have a higher potential for inducing convective clouds than wet cooling tower plumes, under most summertime meteorological conditions. This is due to the fact that both the sensible heat and momentum fluxes from a dry tower in summer are approximately one order of magnitude larger than those from a wet cooling tower.

Ecological specificities of the interaction between animal breeding and climate changes, caused by greenhouse gas emissions

2017 ◽  
Vol 4 (3) ◽  
pp. 62-72
Author(s):  
O. Zhukorsky ◽  
O. Nykyforuk ◽  
N. Boltyk
Keyword(s):  
Greenhouse Gases ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Climatic Conditions ◽  
Animal Breeding ◽  
Gas Emissions ◽  
Climate Conditions ◽  
Emissions Inventory ◽  
Theoretical Substantiation ◽  
Global Problems

Aim. Proper development of animal breeding in the conditions of current global problems and the decrease of anthropogenic burden on environment due to greenhouse gas emissions, caused by animal breeding activity, require the study of interaction processes between animal breeding and external climatic conditions. Methods. The theoretical substantiation of the problem was performed based on scientifi c literature, statistical informa- tion of the UN Food and Agriculture Organization and the data of the National greenhouse gas emissions inventory in Ukraine. Theoretically possible emissions of greenhouse gases into atmosphere due to animal breeding in Ukraine and specifi c farms are calculated by the international methods using the statistical infor- mation about animal breeding in Ukraine and the economic-technological information of the activity of the investigated farms. Results. The interaction between the animal breeding production and weather-and-climate conditions of environment was analyzed. Possible vectors of activity for the industry, which promote global warming and negative processes, related to it, were determined. The main factors, affecting the formation of greenhouse gases from the activity of enterprises, aimed at animal breeding production, were characterized. Literature data, statistical data and calculations were used to analyze the role of animal breeding in the green- house gas emissions in global and national framework as well as at the level of specifi c farms with the consid- eration of individual specifi cities of these farms. Conclusions. Current global problems require clear balance between constant development of sustainable animal breeding and the decrease of the carbon footprint due to the activity of animal breeding.

Case study: Theoretical calculation model and variable condition analysis research on the water-splashing noise for natural draft wet cooling towers

2020 ◽  
Vol 68 (2) ◽  
pp. 137-145
Author(s):  
Yang Zhouo ◽  
Ming Gao ◽  
Suoying He ◽  
Yuetao Shi ◽  
Fengzhong Sun
Keyword(s):  
Theoretical Model ◽  
Sound Pressure Level ◽  
Water Droplet ◽  
Water Distribution ◽  
Sound Pressure ◽  
Cooling Tower ◽  
Distribution Patterns ◽  
Calculation Model ◽  
Pressure Level ◽  
Cooling Towers

Based on the basic theory of water droplets impact noise, the generation mechanism and calculation model of the water-splashing noise for natural draft wet cooling towers were established in this study, and then by means of the custom software, the water-splashing noise was studied under different water droplet diameters and water-spraying densities as well as partition water distribution patterns conditions. Comparedwith the water-splashing noise of the field test, the average difference of the theoretical and the measured value is 0.82 dB, which validates the accuracy of the established theoretical model. The results based on theoretical model showed that, when the water droplet diameters are smaller in cooling tower, the attenuation of total sound pressure level of the water-splashing noise is greater. From 0 m to 8 m away from the cooling tower, the sound pressure level of the watersplashing noise of 3 mm and 6 mm water droplets decreases by 8.20 dB and 4.36 dB, respectively. Additionally, when the water-spraying density becomes twice of the designed value, the sound pressure level of water-splashing noise all increases by 3.01 dB for the cooling towers of 300 MW, 600 MW and 1000 MW units. Finally, under the partition water distribution patterns, the change of the sound pressure level is small. For the R s/2 and Rs/3 partition radius (Rs is the radius of water-spraying area), when the water-spraying density ratio between the outer and inner zone increases from 1 to 3, the sound pressure level of water-splashing noise increases by 0.7 dB and 0.3 dB, respectively.

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