Forced-Convection Condensation of Ethylene Glycol on Integral-Fin Tubes

2004 ◽  
Author(s):  
Satesh Namasivayam ◽  
Adrian Briggs
Keyword(s):  
Ethylene Glycol ◽  
Forced Convection ◽  
Experimental Studies ◽  
Heat Fluxes ◽  
Slight Reduction ◽  
Enhancement Ratio ◽  
Vapor Velocity ◽  
Wide Range ◽  
Plain Tube ◽  
Fin Tubes

This paper reports new experimental data for forced-convection condensation of ethylene glycol on a set of five single, copper, integral-fin tubes. The five tubes had fin root diameter of 12.7 mm, fin height and thickness of 1.6 mm and 0.25 mm respectively. Fin spacings were 0.25, 0.5, 1.0, 1.5 and 2.0 mm. A plain tube of outside diameter 12.7 mm was also tested. The tests, which were performed at near constant pressure of approximately 15 kPa, covered vapor velocities between 10 and 22 m/s and a wide range of heat fluxes. The best performing tube was that with a fin spacing of 0.5 mm, which had an enhancement ratio (compared to the plain tube at the same vapor-side temperature difference and vapor velocity) of 2.5 at the lowest vapor velocity tested, increasing to 2.7 at the highest. The increase in enhancement ratio with increasing vapor velocity, which is the opposite trend to that found in most earlier experimental studies, was thought to be due to a slight reduction in condensate flooding between the fins due to increased vapor shear.

Condensation of Ethylene Glycol on Integral-Fin Tubes: Effect of Fin Geometry and Vapor Velocity

2005 ◽  
Vol 127 (11) ◽  
pp. 1197-1206 ◽  
Author(s):  
Satesh Namasivayam ◽  
Adrian Briggs
Keyword(s):  
Ethylene Glycol ◽  
Experimental Studies ◽  
Heat Fluxes ◽  
Slight Reduction ◽  
Enhancement Ratio ◽  
Vapor Velocity ◽  
Wide Range ◽  
Plain Tube ◽  
Fin Tubes ◽  
Fin Spacing

New experimental data are reported for forced-convection condensation of ethylene glycol on a set of nine single, copper, integral-fin tubes. The first set of five tubes had fin height and thickness of 1.6 and 0.25mm, respectively, with fin spacings of 0.25, 0.5, 1.0, 1.5, and 2.0mm. The second set of four tubes had fin spacing and thickness of 1.0 and 0.5mm, respectively, and fin heights of 0.5, 0.9, 1.3, and 1.6mm. The fins were rectangular in cross section. All tubes had a fin root diameter of 12.7mm. A plain tube of outside diameter 12.7mm was also tested. The tests, which were performed at a near constant pressure of ∼15kPa, covered vapor velocities between 10 and 22m∕s and a wide range of heat fluxes. The best performing tube was that with fin spacing, height, and thickness of 0.5, 1.6, and 0.25mm, respectively, which had an enhancement ratio (compared to the plain tube at the same vapor-side temperature difference and vapor velocity) of 2.5 at the lowest vapor velocity tested, increasing to 2.7 at the highest. For all but two of the tubes, the effect of vapor velocity on the heat-transfer coefficient of the finned tubes was less than on the plain tube, leading to a decrease in enhancement ratio with increasing vapor velocity. For two of the tubes, however, the enhancement ratio increased with increasing vapor velocity, which is the opposite trend to that found in most earlier experimental studies. This effect was thought to be due to the slight reduction in condensate flooding between the fins of these two tubes because of vapor shear.

Condensation of Steam on Integral-Fin Tubes in a Bank

2003 ◽  
Author(s):  
Adrian Briggs ◽  
Sritharan Sabaratnam
Keyword(s):  
Atmospheric Pressure ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Vapor Velocity ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Plain Tube ◽  
Reported Data ◽  
Fin Tubes

Accurate repeatable data are presented for condensation of atmospheric pressure steam on three rows of integral-fin tubes situated in a bank of plain tubes. The data cover a wide range of vapor velocities and heat fluxes. Unlike previously reported data for plain tubes using the same test bank and apparatus, the heat-transfer coefficients for the finned tubes were unaffected by vapor velocity. When compared to a plain tube of fin-tip diameter and at the same vapor side temperature difference, enhancement ratios between 3.7 and 4.9 were found for the finned tubes compared to a plain tube in quiescent vapor conditions, while values between 1.9 and 3.9 were found when compared to a plain tube at the same vapor velocity.

Effect of Vapour Velocity on Condensation of Ethylene Glycol on Horizontal Integral Fin Tubes: Heat Transfer and Retention Angle Measurements

2010 ◽  
Author(s):  
Claire L. Fitzgerald ◽  
Adrian Briggs ◽  
Huasheng Wang ◽  
John W. Rose
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Root Diameter ◽  
Transfer Coefficients ◽  
Vapor Velocity ◽  
Finned Tubes ◽  
Tube Wall Temperature ◽  
Transfer And Retention ◽  
Plain Tube ◽  
Fin Tubes

Heat-transfer data are reported for forced-convection filmwise condensation of ethylene glycol flowing vertically downward over two single, horizontal instrumented integral-fin tubes and one plain tube. Vapor-side, heat-transfer coefficients were obtained by direct measurement of the tube wall temperature using two specially manufactured, instrumented tubes with thermocouples embedded in the tube walls. Both tubes have fin height of 1.6 mm and fin root diameter and 12.7 mm, with fin thickness and spacings of 0.3 mm and 0.6 mm, respectively for one of the tubes and 0.5 mm and 1 mm, respectively for the other. Tests were performed at low pressures; 5.59kPa, 8.15kPa and 11.23kPa, at nominal vapour velocities from 13m/s to 82 m/s. All the data show that both of the finned tubes provided an increase in heat flux at the same vapour-side temperature difference with increasing vapour velocity. Visual observations were made and photographs obtained of the fluid retention angle φf at each combination of vapor velocity and pressure tested. It was observed that the curvature of the meniscus was distorted by the increase in vapor velocity and in many cases, the extent of condensate flooding decreased compared to its value in the quiescent vapor case.

Condensation From Pure Steam and Steam–Air Mixtures on Integral-Fin Tubes in a Bank

2004 ◽  
Vol 127 (6) ◽  
pp. 571-580 ◽  
Author(s):  
Adrian Briggs ◽  
Sritharan Sabaratnam
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficients ◽  
Vapor Velocity ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Plain Tube ◽  
Reported Data ◽  
Pure Steam ◽  
Fin Tubes

Data are reported for condensation of steam with and without the presence of air on three rows of integral-fin tubes situated in a bank of plain tubes. The data cover a wide range of vapor velocities and air concentrations. Unlike previously reported data for plain tubes using the same test bank and apparatus, the heat-transfer coefficients for the finned tubes were largely unaffected by vapor velocity. When compared to a plain tube of fin-tip diameter and at the same vapor side temperature difference, heat-transfer enhancement ratios between 3.7 and 4.9 were found for the finned tubes compared to a plain tube in quiescent vapor conditions, while values between 1.9 and 3.9 were found when compared to a plain tube at the same vapor velocity. When compared to the plain tubes, the heat transfer to the finned tubes was much more susceptible to the presence of noncondensing gas (air) in the vapor, with enhancement ratios falling as low as 1.5 compared to the plain tubes when even small concentrations of air were present.

Heat Transfer to Water at Supercritical Parameters in Vertical Tubes, Annular Channels, 3- and 7-Rod Bundles

2013 ◽  
Author(s):  
V. G. Razumovskiy ◽  
E. M. Mayevskiy ◽  
A. E. Koloskov ◽  
E. N. Pis’mennyi ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Experimental Studies ◽  
Heat Fluxes ◽  
Bulk Temperature ◽  
Experimental Setup ◽  
Gaseous State ◽  
Annular Channels ◽  
Wide Range ◽  
Vertical Tubes

The data on deteriorated transfer to supercritical water in vertical tubes and channels simulating coolant flow in fuel assemblies obtained at the same experimental setup during more than dozen of years are considered and compared with some known results of the experimental studies performed by other authors. They involve the data for vast ranges of geometry, mass velocity, heat flux rate, and pressure, in some cases for up- and downward flow, for flow with and without thermoacoustic oscillations. For the first time the data illustrating deterioration of heat transfer in the bundles of fuel elements are presented. An attempt to explain the phenomena of “inlet” peak of wall temperature is made. It is shown that temperature regimes of the tubes cooled with supercritical water in a gaseous state (i.e., at bulk temperature above the pseudocritical temperature) are close to linear, stable and easily reproducible within a wide range of mass and heat fluxes. Some requirements to the experimental setup, coolant quality, test sections etc. that should be followed in studying thermal and hydraulic parameters of supercritical coolant are analyzed.

A New Model for Forced-Convection Condensation on Integral-Fin Tubes

1996 ◽  
Vol 118 (3) ◽  
pp. 689-693 ◽  
Author(s):  
A. Cavallini ◽  
L. Doretti ◽  
G. A. Longo ◽  
L. Rossetto
Keyword(s):  
Forced Convection ◽  
Reynolds Numbers ◽  
Visual Observation ◽  
Vapor Condensation ◽  
Good Ability ◽  
Wide Range ◽  
Extended Surface ◽  
Data Points ◽  
Fin Tubes ◽  
Semi Empirical

This work investigates the effects of vapor shear during pure vapor external condensation on horizontal integral-fin tubes. More than 220 experimental data points in a wide range of operative conditions and enhanced surface geometries are reported together with the visual observation of the condensate flow patterns. The effects of vapor shear are relevant only for vapor Reynolds numbers greater than 70,000–100,000, while heat transfer enhancement is linked to the geometry of the extended surface. A simple semi-empirical equation was developed to account for the shear stress contribution in forced-convection condensation: this equation, applied in conjunction with the model by Briggs and Rose (1994) for stationary vapor condensation, displays a good ability in reproducing all the available data with relevant vapor velocities.

Influencia de las condiciones de secado solar en la coloración de plantas medicinales

2019 ◽  
pp. 28-34
Author(s):  
Margarita Castillo-Téllez ◽  
Beatriz Castillo-Téllez ◽  
Juan Carlos Ovando-Sierra ◽  
Luz María Hernández-Cruz
Keyword(s):  
Medicinal Plants ◽  
Forced Convection ◽  
Rural Areas ◽  
Color Change ◽  
Drying Process ◽  
Scientific Medicine ◽  
Drying Time ◽  
Bacterial Proliferation ◽  
Wide Range ◽  
Very High

For millennia, humans have used hundreds of medicinal plants to treat diseases. Currently, many species with important characteristics are known to alleviate a wide range of health problems, mainly in rural areas, where the use of these resources is very high, even replacing scientific medicine almost completely. This paper presents the dehydration of medicinal plants that are grown in the State of Campeche through direct and indirect solar technologies in order to evaluate the influence of air flow and temperature on the color of the final product through the L* a* scale. b*, analyzing the activity of water and humidity during the drying process. The experimental results showed that the direct solar dryer with forced convection presents a little significant color change in a drying time of 400 min on average, guaranteeing the null bacterial proliferation and reaching a final humidity between 9 % and 11 %.

Qualitative Analysis of Underlying Factors Affecting Vaccine Hesitancy in Iran- A Study Protocol (Preprint)

2020 ◽  
Author(s):  
Salime Goharinezhad
Keyword(s):  
Vaccine Coverage ◽  
Deep Understanding ◽  
World Health ◽  
Vaccine Hesitancy ◽  
Slight Reduction ◽  
Cultural Variation ◽  
Global Public Health ◽  
Factors Affecting ◽  
Wide Range ◽  
Context Specific

BACKGROUND World Health Organization declared the vaccine hesitancy as a global public health threat in 2019. Since even a slight reduction in vaccine coverage rates can lead to a decrease in herd immunity, it is imperative to explore the underlying factors affecting vaccine hesitancy. in specific contexts, considering socioeconomic and cultural variation, to ensure interventions targeting hesitancy are well formulated and intervened. OBJECTIVE The main objective of this study is to identify underlying factors affecting vaccine hesitancy in Iran. METHODS A framework qualitative study will be conducted in the west of Tehran province in 2020. Participants in the study will be recruited hesitance-parents who extracted from the SIB system (an electronic health record in Iran) to maximize diversity. Interviews will be analyzed based on ''Determinants of Vaccine Hesitancy Matrix'' which developed by the WHO-SAGE Working Group. RESULTS deep understanding from the context-specific reasons for vaccine hesitancy cause to formulate better strategies to address them. The ultimate goal of this study is to inform future policies to increase the uptake of the vaccine in Iran. CONCLUSIONS This result of study will show variety opinions about vaccination among different types of socioeconomic and demographic households. The wide range of reasons related to vaccine hesitancy imply to more comprehensive, context-specific interventions. Today, the most important intervention issues focus on improving information about effectiveness and safety of vaccines, while other interventions for promoting vaccination is need to addressed.

scholarly journals Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 421
Author(s):  
Dariusz Puchala ◽  
Kamil Stokfiszewski ◽  
Mykhaylo Yatsymirskyy
Keyword(s):  
Statistical Analysis ◽  
Image Encryption ◽  
Experimental Studies ◽  
Quality Measures ◽  
Input Image ◽  
Jpeg Compression ◽  
Image Statistics ◽  
Compression Stage ◽  
Wide Range ◽  
The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

Sign in / Sign up

Export Citation Format

Share Document