Film Condensation of Steam on Externally Enhanced Horizontal Tubes PDF Download
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Author: Evagelos S. Mitrou
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 0
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Book Description
Heat-transfer measurements were made for filmwise condensation of steam on externally enhanced horizontal tubes under vacuum and at atmospheric pressure. Data were obtained for copper tubes with circular fins of rectangular, triangular, trapezoidal, and parabolic cross sections for spiral fins of triangular cross section, for commercially available finned tubes and for wire-wrapped tubes. Four spirally finned tubes from each of Cu, Cu-ni, A1 and stainless steel and two tubes with fins of rectangular cross section from each of Cu-Ni and A1 were manufactured and tested to investigate the effect of thermal conductivity. Among sprially finned tubes, the optimum fin pitch was found to be 1.6 mm. The tubes with a parabolic fin shape showed the best performance with steam-side enhancements of 4.1 and 6.2 under vacuum and at the atmospheric pressure respectively. Enhancement ratios as high as 3.5 and 2.1 were obtained under vacuum and at atmospheric pressure, respectively, for the commercially available finned tubes. The heat-transfer performance decreased with decreasing tube metal thermal conductivity. For the wire-wrapped tubes, an optimum pitch to wire diameter ratio of about 5.1 was found, with steam-side enhancements of about 1.9 and 2.2 under vacuum and at atmospheric pressure, respectively. A recent theoretical analysis of laminar film of low-surface-tension fluids on wire-wrapped tubes was modified to include the condensate retention of the tube due to the high surface tension of water. Agreement between this modified analysis and the experimental data was favorable. Keywords: Heat transfer coefficient.
Author: Evagelos S. Mitrou
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 0
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Book Description
Heat-transfer measurements were made for filmwise condensation of steam on externally enhanced horizontal tubes under vacuum and at atmospheric pressure. Data were obtained for copper tubes with circular fins of rectangular, triangular, trapezoidal, and parabolic cross sections for spiral fins of triangular cross section, for commercially available finned tubes and for wire-wrapped tubes. Four spirally finned tubes from each of Cu, Cu-ni, A1 and stainless steel and two tubes with fins of rectangular cross section from each of Cu-Ni and A1 were manufactured and tested to investigate the effect of thermal conductivity. Among sprially finned tubes, the optimum fin pitch was found to be 1.6 mm. The tubes with a parabolic fin shape showed the best performance with steam-side enhancements of 4.1 and 6.2 under vacuum and at the atmospheric pressure respectively. Enhancement ratios as high as 3.5 and 2.1 were obtained under vacuum and at atmospheric pressure, respectively, for the commercially available finned tubes. The heat-transfer performance decreased with decreasing tube metal thermal conductivity. For the wire-wrapped tubes, an optimum pitch to wire diameter ratio of about 5.1 was found, with steam-side enhancements of about 1.9 and 2.2 under vacuum and at atmospheric pressure, respectively. A recent theoretical analysis of laminar film of low-surface-tension fluids on wire-wrapped tubes was modified to include the condensate retention of the tube due to the high surface tension of water. Agreement between this modified analysis and the experimental data was favorable. Keywords: Heat transfer coefficient.
Author: Frederick A. Flook
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 147
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Book Description
Filmwise condensation measurements of steam were made on horizontal finned tubes under vacuum and near-atmospheric conditions. Data were obtained for copper tubes with fins of rectangular, triangular, trapezoidal, and parabolic cross sections, and for a commercially-available finned tube. A stainless steel finned tube was also tested to investigate the effect of thermal conductivity. Maximum enhancements of about 4.8 were obtained under vacuum conditions, and about 6.9 at atmospheric pressure, compared to a smooth tube having an outside diameter equal to the root diameter of the finned tubes. The optimum fin spacing was found to be about 2.0 mm for rectangularly shaped-fins with a fin-thickness of 1.0 mm, and fin height of 0.5 and 1.5 mm. Fins with a parabolic shape were shown to perform better than fins of rectangular shape, and fins were shown to degrade the performance of stainless steel tubes. The effects of vapor shear were also shown to have only a small influence on the steam-side heat transfer coefficient. A theoretical model proposed by Webb et al. was found to underpredict the experimental data. Several suggestions to modify this model are described. Keywords: External fin; Heat transfer coefficient; Enhancement, Condenser tubes (Theses).
Author:
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ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Filmwise condensation measurements of steam were made on horizontal finned tubes under vacuum and near-atmospheric conditions. Data were obtained for copper tubes with fins of rectangular, triangular, trapezoidal, and parabolic cross sections, and for a commercially-available finned tube. A stainless steel finned tube was also tested to investigate the effect of thermal conductivity. Maximum enhancements of about 4.8 were obtained under vacuum conditions, and about 6.9 at atmospheric pressure, compared to a smooth tube having an outside diameter equal to the root diameter of the finned tubes. The optimum fin spacing was found to be about 2.0 mm for rectangularly shaped-fins with a fin-thickness of 1.0 mm, and fin height of 0.5 and 1.5 mm. Fins with a parabolic shape were shown to perform better than fins of rectangular shape, and fins were shown to degrade the performance of stainless steel tubes. The effects of vapor shear were also shown to have only a small influence on the steam-side heat transfer coefficient. A theoretical model proposed by Webb et al. was found to underpredict the experimental data. Several suggestions to modify this model are described. Keywords: External fin; Heat transfer coefficient; Enhancement, Condenser tubes (Theses).
Author: William M. Poole
Publisher:
ISBN:
Category : Condensation (Meteorology)
Languages : en
Pages : 86
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Book Description
The film-condensation characteristics of a smooth tube and six externally-finned tubes having fins 1 mm high and 1 mm thick, and ptiches of 1.5, 2.0, 2.5, 3.0, 5.0, and 10.0 mm, were experimentally tested. A smooth copper tube with an active length of 133.5 mm, an outside diameter of 19.05 mm, and an inside diameter of 12.7 mm was first tested to correlate the inside heat-transfer coefficient using the Sieder-Tate equation. The leading coefficient for this equation was found to be 0.034 + or - 0.001, and was used to derive the external condensing coefficient for all of the tubes by subtracting the inside and wall resistances from the measured overall resistance. The condensing coefficient was measured, both at atmospheric pressure and vacuum (84 mm hg), with the heat flux as a variable. Condensation data taken for the smooth tube were compared with data in the literature to check the reliability of the apparatus and the data-reduction procedures. The data for the finned tubes showed an optimum pitch of 2.5 mm. (Author).
Author:
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ISBN:
Category :
Languages : en
Pages :
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Book Description
The problem of condensation of steam on a vertical tier of horizontal tubes is investigated by both analytical and experimental methods in this study. A computer program is written to perform the analysis of laminar film condensation on the horizontal tubes. The program is capable to calculate condensate film thickness and velocity distribution, as well as the heat transfer coefficient within the condensate. An experimental setup was also manufactured to observe the condensation phenomenon. Effects of tube diameter and temperature difference between steam and the tube wall on condensation heat transfer have been analytically investigated with the computer program. Experiments were carried out at different inclinations of the tier of horizontal tubes. Effects of the steam velocity and the distance between the horizontal tubes are also experimentally investigated. Results of the experiments are compared to those of the studies of Abdullah et al., Kumar et al. and Nusselt as well as to the analytical results of the present study.
Author:
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ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Heat transfer and hydrodynamic performance of eight different geometrically enhanced tubes of different metals was determined. Results were compared to a 25.4 mm (1.0 in.) OD, smooth stainless steel tube. Steam at about 21 kPa (3 psia) was condensed on the outside surface of each enhanced tube, horizontally mounted in the center of a dummy tube Bank. Each tube was cooled on the inside by water. The overall heat transfer coefficient was determined directly from experimental data. The inside and outside heat transfer coefficients were determined using the Wilson plot technique. The cooling water pressure drop was measured inside the tube and converted to the friction factor in the enhanced section. The overall heat transfer coefficients of the enhanced tubes were increased as much as 1.9 times, and the corrected pressure drops of the enhanced tubes were as large as 4 times the corresponding smooth tube value for the same cooling water velocity. The helix angle should be 45 deg to 60 deg on the inside surface and 90 deg on the outside surface of the tube to obtain maximum inside and outside heat transfer coefficients. (Author).
Author: Huseyin Ciftci
Publisher:
ISBN:
Category : Mechanical engineering
Languages : en
Pages : 170
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Book Description
Heat transfer and hydrodynamic performance of eight different geometrically enhanced tubes of different metals was determined. Results were compared to a 25.4 mm (1.0 in.) OD, smooth stainless steel tube. Steam at about 21 kPa (3 psia) was condensed on the outside surface of each enhanced tube, horizontally mounted in the center of a dummy tube Bank. Each tube was cooled on the inside by water. The overall heat transfer coefficient was determined directly from experimental data. The inside and outside heat transfer coefficients were determined using the Wilson plot technique. The cooling water pressure drop was measured inside the tube and converted to the friction factor in the enhanced section. The overall heat transfer coefficients of the enhanced tubes were increased as much as 1.9 times, and the corrected pressure drops of the enhanced tubes were as large as 4 times the corresponding smooth tube value for the same cooling water velocity. The helix angle should be 45 deg to 60 deg on the inside surface and 90 deg on the outside surface of the tube to obtain maximum inside and outside heat transfer coefficients. (Author).
Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 936
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Book Description
Author: James M. Coumes
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Book Description
Heat-transfer measurements were made for filmwise condensation of steam on smooth tubes and finned tubes with rectangular-shaped fins. The influence of fin root diameter on a single horizontal finned tube was examined by taking data for two families of tubes whose fin root diameters were 12.7 and 19.05 mm. Each family of tubes had fins that were 1 mm thick and 1 mm high, but with fin spacings of 0.25, 0.50, 1.0, 1.5, 2.0, and 4.0 mm. To compare results being obtained in a concurrent research project with Queen Mary College (University of London), data were collected on two tubes whose fin root diameters were 12.7 mm, and which had fin thickness of 0.5 mm, fin heights of 1.59 mm, and fin spacings of 1.0 mm. A comparison of the enhancement ratios (based on constant vapor-side temperature drop) with past Naval Postgraduate School (nps) studies showed good agreement. The apparatus was then modified in order to study the effects of condensate inundation.
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Category :
Languages : en
Pages : 0
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Book Description
In an effort to explore the possibility of building compact naval steam condensers, an experimental apparatus was designed and constructed to study enhanced condensation heat transfer of steam on horizontal tubes. Special care was taken to ensure a leak-tight apparatus so that the non-condensable gas content of the steam can be kept to a few parts-per-million. The boiler and steam piping is made of glass and stainless steel with rubber gaskets. Copper is used for the condensing tubes. The completed system has been tested satisfactorily at full power. (Author).
