The Performances of Internal Helical-Rib Roughness Tubes Under Fouling Conditions: Practical Cooling Tower Water Fouling and Accelerated Particulate Fouling

2003 ◽  
Vol 125 (4) ◽  
pp. 746-748 ◽  
Author(s):  
Wei Li
Keyword(s):  
Cooling Tower ◽  
Particulate Fouling

This paper addresses fouling in a family of seven copper helically ribbed tubes. Series of semi-theoretical linear fouling correlations for long term combined precipitation and particulate fouling (PPF) in cooling tower systems and for accelerated particulate fouling were developed.

Semi-Theoretical Modeling Oscillatory Fouling in Enhanced Tubes in Cooling Tower Systems

2007 ◽  
Author(s):  
Wei Li
Keyword(s):  
Cooling Tower ◽  
Oscillatory Behavior ◽  
Linear Range ◽  
Specific Interest ◽  
Particulate Fouling ◽  
Internal Parameters ◽  
Enhanced Tubes ◽  
Adequate Accuracy ◽  
Oscillatory Model

The fluctuation of fouling data, a well-known fouling phenomenon, was recognized in applications three decades ago, but it had not yet been well understood. Of specific interest is long term, combined precipitation and particulate fouling in cooling tower systems. Fouling data collected in seven 15.54 mm I.D. copper, helically ribbed tubes at water velocity (1.07 m/s) at practical conditions shows an oscillatory behavior. In order to observe it, a water temperature difference of 3.0°C, or greater, was needed for adequate accuracy based on an uncertainty analysis. Oscillatory model was used to analyze the data. The frequencies of the fluctuation are the same for the seven tested tube geometries. A series of semi-theoretical correlations of fluctuation of the long-term cooling tower water fouling data were developed. It was found that there are two ranges of amplitudes of the fluctuation based on internal parameters: linear range and non-linear range.

Experimental Studies of Shell and Tube Condenser Fouling and Accelerated Particulate Fouling in Internal Helical-Rib Roughness Tubes

2003 ◽  
Author(s):  
Wei Li
Keyword(s):  
Cooling Tower ◽  
Experimental Studies ◽  
Cooling Water ◽  
Particulate Fouling ◽  
Enhanced Tubes ◽  
Shell And Tube ◽  
Condenser Fouling ◽  
Tube Condenser

This paper addresses fouling in a family of seven 15.54 mm I.D. copper, helically ribbed tubes, which have different ridge heights, helix angles, and number of ridge starts. A series of semi-theoretical linear fouling correlations as a function of the product of area indexes and efficiency indexes for long term combined precipitation and particulate fouling (PPF) in cooling tower systems and a series of semi-theoretical linear fouling correlations as a function of the efficiency indexes for particulate fouling were developed. The correlations can be directly used to assess the fouling potential of enhanced tubes in actual cooling water situations.

Oscillatory Fouling in Condensers in Cooling Tower Systems

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Wei Li
Keyword(s):  
Theoretical Analysis ◽  
Cooling Tower ◽  
Oscillatory Behavior ◽  
Water Velocity ◽  
Experimental Uncertainty ◽  
Physical Mechanisms ◽  
The Mean ◽  
Relationship Of ◽  
The Relationship

Abstract Oscillatory fouling in condensers using cooling tower water was recognized in 1980s, but it had not yet been theoretically analyzed. Without careful theoretical analysis, it is easy to think that oscillatory fouling phenomenon is generated from experimental uncertainty. The new analysis is to split the fouling rate into a mean variable and a fluctuating variable. The mean variable exhibits an asymptotic behavior, and the fluctuating variable exhibits an oscillatory behavior. A theoretical analysis based on the relationship of continuity is used to present fouling oscillatory behavior along the space and time dimensions simultaneously to provide the intuitive understanding in physical mechanisms driving the phenomenon. A series of long-term cooling tower water fouling tests were conducted: fouling data collected in two copper helically ribbed tubes with the same internal and external diameters and different inside geometric parameters at the same water velocity in condenser in practical cooling tower conditions present oscillatory behavior. The frequencies of the fluctuation are the same for the two tested tube geometries. The spatial and the temporal oscillatory fouling behaviors presented in the experimental results are predicted by the theoretical analysis.

scholarly journals Influence of Flue Gas Injection on the Long-Term Durability of a Natural Draft Concrete Cooling Tower

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2038
Author(s):  
Jianmin Du ◽  
Wenjuan Zhuang ◽  
Guo Li ◽  
Pei Zhang
Keyword(s):  
Flue Gas ◽  
Cooling Tower ◽  
Effective Diffusion ◽  
Gas Injection ◽  
Chemical Compositions ◽  
Natural Draft ◽  
Corrosion Risk ◽  
Finite Element Numerical Simulation

The article undertakes the very important topic of the long-term durability of concrete in a natural draft concrete cooling tower with flue gas injection. The corrosive conditions, including temperature, relative humidity, and CO2 and SO2 gas concentrations, near the inner wall of a cooling tower with flue gas injection were monitored in real time to obtain the long-term durability performance of concrete. The pH and chemical compositions of the condensed liquid that adhered to the tower’s inner face and the macromorphology, compressive strength, and neutralization depth of in situ specimens were tested periodically. In addition, a finite element numerical simulation was conducted to simulate and verify the concentration distributions of CO2 and SO2 in the flue gas in the cooling tower. The results showed that the cleaned flue gas was enveloped, diluted, and uplifted by hot vapor in the cooling tower, and its concentration decreased. Meanwhile, the effective diffusion radius increased gradually as the flue gas rose. With the same elevation in the cooling tower, the concentration of flue gas decreased rapidly from the central point to the surrounding area. The air near the inner surface of the cooling tower was merely dampened air with a low concentration of acidic gas due to the gigantic diameter of the cooling tower. As a result, the injection of cleaned flue gas will not evidently increase the corrosion risk in a natural draft concrete cooling tower.

scholarly journals Experimental Study of a Humidification-Dehumidification Seawater Desalination System Combined with the Chimney

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Fei Cao ◽  
Qingjun Liu ◽  
Hong Xiao
Keyword(s):  
Experimental Study ◽  
Wind Speed ◽  
Thermal Efficiency ◽  
Cooling Tower ◽  
Heating Power ◽  
Heat Power ◽  
Seawater Desalination ◽  
Remote Areas ◽  
Evaporation And Condensation

The solar humidification-dehumidification system is of high significance to the freshwater supply in remote areas. In the present study, a humidification-dehumidification seawater desalination system combined with the chimney is designed and experimentally evaluated. Main parameters influencing its freshwater productivity are analyzed. It is found from this study that the cooling tower is required to obtain long-term steady freshwater generation. Raising the temperature difference between the evaporation and condensation chambers would lead to the rise of the freshwater productivity. There is a turning wind speed, beyond which increasing the wind speed would lead to the decline of both the freshwater productivity and the thermal efficiency. The turning wind speed is relevant to the ambient humanity and the heating power. Decreasing the heat power would increase the turning wind speed. When the heating power is 4.9 kW, the highest freshwater productivity and the highest efficiency are 48 g/min and 32.14%, respectively.

Mitigation of Particulate Fouling by Ozonation

2003 ◽  
Vol 125 (1) ◽  
pp. 147-150 ◽  
Author(s):  
Bang-Yenn Wu ◽  
S. H. Chan
Keyword(s):  
Heat Transfer ◽  
Calcium Carbonate ◽  
Cooling Tower ◽  
Cooling Water ◽  
Reynolds Numbers ◽  
Fouling Resistance ◽  
Low Reynolds Numbers ◽  
Particulate Fouling ◽  
High Reynolds ◽  
Deposit Layer

Heat transfer surface fouling introduces a major uncertainty into the design and operation of cooling water systems. Fouling caused by calcium carbonate CaCO3 typically occurs on heat transfer surfaces. Ozone has been successfully used for more than 90 years as a disinfectant in drinking water. Recently, it has been proposed to use ozone for cooling tower water treatment. In this research, the effectiveness of mitigation of calcium carbonate particulate fouling by ozone was studied systematically. The experimental results show that, at low Reynolds numbers, though the ozonation retards the initial calcium carbonate particulate fouling rate, the retardation led to a non-porous deposit layer and a higher asymptotic fouling resistance. However, at high Reynolds numbers, ozonation was found to reduce the asymptotic fouling resistance.

Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders?

2019 ◽  
Vol 42 ◽  
Author(s):  
John P. A. Ioannidis
Keyword(s):  
Mental Health ◽  
Mental Disease ◽  
Brain Disorders ◽  
Social Stressors ◽  
Labor Education ◽  
Mental Diseases ◽  
Long Term Follow Up ◽  
Political Decisions

AbstractNeurobiology-based interventions for mental diseases and searches for useful biomarkers of treatment response have largely failed. Clinical trials should assess interventions related to environmental and social stressors, with long-term follow-up; social rather than biological endpoints; personalized outcomes; and suitable cluster, adaptive, and n-of-1 designs. Labor, education, financial, and other social/political decisions should be evaluated for their impacts on mental disease.

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