Effect of Vapor Velocity on Condensation of Low-Pressure Steam on Integral-Fin Tubes

2007 ◽  
Vol 129 (11) ◽  
pp. 1486-1493 ◽  
Author(s):  
Satesh Namasivayam ◽  
Adrian Briggs
Keyword(s):  
Heat Transfer ◽  
Low Pressure ◽  
Heat Transfer Process ◽  
Root Diameter ◽  
Absolute Pressure ◽  
Vapor Velocity ◽  
Pressure Steam ◽  
Two Parameters ◽  
Fin Tubes ◽  
Fin Spacing

Experimental data are presented for forced-convection condensation of low-pressure steam on a set of single, integral-fin tubes. The five tubes had fin-root diameter of 12.7mm and identical fin geometry except for fin spacing, which was varied from 0.25mmto2mm. The range of vapor velocity was 14.7–62.3m∕s at an absolute pressure of 14kPa. Heat-transfer enhancement was a strong function of both vapor velocity and fin spacing, and the interrelationship of the two parameters led to complex trends in the data. Observations of the extent of condensate flooding (i.e., condensate trapped between the fins at the bottom of the tube) indicated that the effect of vapor shear on flooding was a significant controlling factor in the heat-transfer process, and this factor explained, at least quantitatively, the trends observed.

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.

Film Condensation of Refrigerant-113 and Ethanediol on a Horizontal Tube—Effect of Vapor Velocity

1984 ◽  
Vol 106 (3) ◽  
pp. 524-530 ◽  
Author(s):  
W. C. Lee ◽  
S. Rahbar ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Horizontal Tube ◽  
Low Pressure ◽  
Film Condensation ◽  
Vapor Velocity

Heat transfer measurements are reported for condensation of refrigerant-113 and ethanediol (ethylene glycol) on a single horizontal tube with vertical downflow. For refrigerant-113, vapor velocities up to around 6 m/s were obtained, while for ethanediol, velocities in excess of 100 m/s were obtained at low pressure. The results are compared with those of earlier investigators and with theory.

Local and Average Characteristics of Heat/Mass Transfer Over Flat Tube Bank Fin With Four Vortex Generators per Tube

2002 ◽  
Vol 124 (3) ◽  
pp. 546-552 ◽  
Author(s):  
L. B. Wang ◽  
F. Ke ◽  
S. D. Gao ◽  
Y. G. Mei
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Heat Transfer Process ◽  
Attack Angle ◽  
Vortex Generators ◽  
Back Surface ◽  
Flat Tube ◽  
Fin Spacing

The analogy between heat and mass transfer has been used to obtain local and average heat transfer characteristics over a complete flat tube-fin element with four vortex generators (VGs) per tube. Several types of surfaces involved in heat transfer process such as fin surface mounted with VGs, its back surface (mounted without VGs) and flat tube surface are considered. The mass transfer experiments are performed using naphthalene sublimation method. The effects of the fin spacing and VG parameters such as height and attack angle on heat transfer and pressure drop are investigated. The comparisons of heat transfer enhancement with flat tube-fin element without VG enhancement under three constraints are carried out. The local Nusselt number distribution reveals that VGs can efficiently enhance the heat transfer in the region near flat tube on fin surface mounted with VGs. On its back surface the enhancement is almost the same as on the fin surface mounted with VGs but enhanced region is away from flat tube wall with some distance. Average results reveal that increasing of VG height and attack angle increases the enhancement of heat transfer and pressure drop, whereas small fin spacing causes greater increase of pressure drop. The heat transfer performance, correlations of Nusselt number and friction factor are also given.

Horizontal Plain and Low-Finned Condenser Tubes—Effect of Fin Spacing and Drainage Strips on Heat Transfer and Condensate Retention

1986 ◽  
Vol 108 (4) ◽  
pp. 946-950 ◽  
Author(s):  
K. K. Yau ◽  
J. R. Cooper ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Heat Transfer Performance ◽  
Marginal Effect ◽  
Transfer Performance ◽  
Finned Tubes ◽  
Plain Tube ◽  
Fin Tubes ◽  
Fin Spacing ◽  
The Heat Transfer Coefficient

The paper reports a continuation of an experimental investigation of the effect of fin pitch on the heat transfer performance of horizontal, integral-fin tubes for condensation of steam at near-atmospheric pressure. The effects of “drainage strips” located along the lower edge of finned and plain tubes have been studied. These gave significant increases in the heat transfer coefficient for finned tubes but had only marginal effect for the plain tube. Condensate retention angles have also been measured for simulated condensation using water, ethylene glycol, and refrigerant-113 for finned tubes with and without drainage strips. In the latter case the data agreed satisfactorily with theory. Drainage strips were found to reduce the extent of holdup significantly.

Effect of Fin Spacing on the Performance of Horizontal Integral-Fin Condenser Tubes

1985 ◽  
Vol 107 (2) ◽  
pp. 377-383 ◽  
Author(s):  
K. K. Yau ◽  
J. R. Cooper ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Finned Tube ◽  
Transfer Enhancement ◽  
Rectangular Section ◽  
Local Maxima ◽  
Finned Tubes ◽  
Plain Tube ◽  
Fin Tubes ◽  
Fin Spacing ◽  
Outside Diameter

The dependence of heat transfer performance on fin spacing has been investigated for condensation of steam on horizontal integral-fin tubes. Thirteen tubes have been used with rectangular section fins having the same width and height (0.5 mm and 1.6 mm) and with fin pitch varying from 1.0 mm to 20.5 mm. For comparison, tests were made using a plain tube having the same inside diameter and an outside diameter equal to that at the root of the fins for the finned tubes. All tests were made at near-atmospheric pressure with vapor flowing vertically downward with velocities between 0.5 m/s and 1.1 m/s. The observed heat transfer enhancement for the finned tubes significantly exceeded that to be expected on grounds of increased area. Plots of enhancement against fin density were repeatable and showed local maxima and minima. The dependence of enhancement on fin density did not depend appreciably on vapor velocity or condensation rate for the ranges used. The maximum vapor-side enhancement (i.e., vapor-side heat transfer coefficient of finned tube/vapor-side coefficient for plain tube) was found to be around 3.6 for the tube with a fin spacing of 1.5 mm.

scholarly journals Effect of condensate flow rate, surface tension, density and vapor velocity on condensate retention of wire wrapped tubes

2021 ◽  
pp. 275-275
Author(s):  
Aaqib Imdad ◽  
Hassan Ali ◽  
Haroon Farooq ◽  
Hafiz Ali
Keyword(s):  
Surface Tension ◽  
Flow Rate ◽  
Root Diameter ◽  
Air Velocity ◽  
Good Correspondence ◽  
Flow Rates ◽  
Vapor Velocity ◽  
Static Conditions ◽  
Authentic Data ◽  
Fin Spacing

Simulated condensation has been conducted on three wire wrapped tubes having same root diameter but different fin spacing of 1.5mm, 2mm and 2.5mm. Different fluids (Ethanol, Ethylene Glycol and Water) are used for condensation by providing them to the tubes through tiny holes in inter-fin spacing on the top of the surface of tubes. The major parameters are to be controlled in this research are fin spacing, vapor velocity, condensate flow rate and ratio of surface tension to density of the fluid. Obtained results show that flooding angle (calculated from the top of the tube to the level where fluid fills the fin) rises by increasing fin spacing. Also, retention angles increase by reducing ratio of surface tension to density of fluid. Acute flooding angles at zero air velocity and zero flow rate, elevates by increasing air velocity. However, obtuse flooding angles at static conditions drop by reducing air velocity. An interesting result is obtained regarding retention angle which remains almost even for the higher condensation flow rates until the tube gets inundated with condensation. Moreover, critical flow rates for all the tubes against using different working fluids are measured. Results obtained for static conditions have good correspondence with already available authentic data for flooding angle. Pictures showing condensate retention angles have been included in this paper.

scholarly journals Condensation Heat Transfer on Enhanced Surface Tubes: Experimental Results and Predictive Theory

2002 ◽  
Vol 124 (4) ◽  
pp. 754-761 ◽  
Author(s):  
M. Belghazi ◽  
A. Bontemps ◽  
C. Marvillet
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Condensation Heat Transfer ◽  
Finned Tubes ◽  
Pure Fluid ◽  
Fin Tubes ◽  
Predictive Theory ◽  
Enhanced Surface ◽  
Fin Spacing ◽  
The Heat Transfer Coefficient

Condensation heat transfer in a bundle of horizontal enhanced surface copper tubes (Gewa C+ tubes) has been experimentally investigated, and a comparison with trapezoidal shaped fin tubes with several fin spacing has been made. These tubes have a specific surface three-dimensional geometry (notched fins) and the fluids used are either pure refrigerant (HFC134a) or binary mixtures of refrigerants (HFC23/HFC134a). For the pure fluid and a Gewa C+ single tube, the results were analyzed with a specifically developed model, taking into account both gravity and surface tension effects. For the bundle and for a pure fluid, the inundation of the lowest tubes has a strong effect on the Gewa C+ tube performances contrary to the finned tubes. For the mixture, the heat transfer coefficient decreases dramatically for the Gewa C+ tube.

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.

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