An Experimental Study of R-113 Film Condensation on Horizontal Integral-Fin Tubes

1990 ◽  
Vol 112 (3) ◽  
pp. 758-767 ◽  
Author(s):  
P. J. Marto ◽  
D. Zebrowski ◽  
A. S. Wanniarachchi ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Theoretical Models ◽  
Smooth Tube ◽  
Film Condensation ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Drainage Patterns ◽  
Fin Tube ◽  
Fin Tubes

Heat transfer measurements were made at near-atmospheric pressure on a smooth tube, on 24 integral-fin tubes having machined, rectangular-shaped fins, and on a commercial integral-fin tube. All tubes were made of copper. The vapor flowed vertically downward with a nominal velocity of 0.4 m/s. Vapor-side heat transfer coefficients were determined with a typical uncertainty of ± 7 percent using a “modified Wilson plot” technique. The vapor-side heat transfer coefficient of the integral-fin tubes (based upon the outside surface area of the smooth tube) was enhanced considerably more than the surface area enhancement provided by the fins. Heat transfer enhancements (for the same vapor-to-wall temperature difference) up to around 7 were measured for a corresponding area enhancement of only 3.9. The optimum fin spacing was found to lie between 0.2 and 0.5 mm, depending upon fin thickness and height. The data were compared with those of other investigations and with several existing theoretical models. Visual observations of condensate drainage patterns from the finned tubes were also made.

Accurate Heat Transfer Measurements for Condensation on Horizontal, Integral-Fin Tubes

1992 ◽  
Vol 114 (3) ◽  
pp. 719-726 ◽  
Author(s):  
A. Briggs ◽  
X.-L. Wen ◽  
J. W. Rose
Keyword(s):  
Heat Transfer ◽  
Significant Proportion ◽  
Theoretical Models ◽  
Experimental Investigations ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Tube Wall Temperature ◽  
Overall Resistance ◽  
Fin Tubes

In most earlier experimental investigations of condensation on low-fin tubes, vapor-side heat transfer coefficients have been found from overall (vapor-to-coolant) measurements using either predetermined coolant-side correlations or “Wilson plot” methods. When the outside resistance dominates, or is a significant proportion of the overall resistance, these procedures can give satisfactory accuracy. However, for externally enhanced tubes, and particularly with high-conductivity fluids such as water, significant uncertainties may be present. In order to provide reliable, high-accuracy data, to assist in the development of theoretical models, tests have been conducted using specially constructed plain and finned tubes fitted with thermocouples to measure the tube wall temperature, and hence the vapor-side heat transfer coefficient, directly. The paper describes the technique for manufacturing the tubes and gives results of systematic heat transfer measurements covering the effects of fin height, thickness, and spacing, tube diameter, and vapor velocity. The tests were carried out with steam, ethylene glycol, and R-113, with vertical vapor downflow. The heat flux was measured using an accurately calibrated 10-junction thermopile and paying particular attention to coolant mixing and isothermal immersion of thermocouple junctions. Care was taken to avoid errors due to the presence in the vapor of noncondensing gas and the occurrence of dropwise condensation. Smooth, consistent, and repeatable results were obtained in all cases. The data are presented in easily accessible form and are compared with the results of previous investigations, where indirect methods were used to determine the vapor-side data, and with theory.

Film Condensation of R-113 on In-Line Bundles of Horizontal Finned Tubes

1991 ◽  
Vol 113 (2) ◽  
pp. 479-486 ◽  
Author(s):  
H. Honda ◽  
B. Uchima ◽  
S. Nozu ◽  
H. Nakata ◽  
E. Torigoe
Keyword(s):  
Heat Transfer ◽  
Tube Bundle ◽  
Three Dimensional ◽  
Finned Tube ◽  
Film Condensation ◽  
Line Bundles ◽  
Finned Tubes ◽  
Fin Tube ◽  
Fin Tubes ◽  
Annular Fins

Film condensation of R-113 on in-line bundles of horizontal finned tubes with vertical vapor downflow was experimentally investigated. Two tubes with flat-sided annular fins and four tubes with three-dimensional fins were tested. The test sections were 3×15 tube bundles with and without two rows of inundation tubes at the top. Heat transfer measurements were carried out on a row-by-row basis. The heat transfer enhancement due to vapor shear was much less for a finned tube bundle than for a smooth tube bundle. The decrease in heat transfer due to condensate inundation was more marked for a three-dimensional fin tube than for a flat-sided fin tube. The predictions of the previous theoretical model for a bundle of flat-sided fin tubes agreed well with the measured data for low vapor velocity and a small to medium condensate inundation rate. Among the six tubes tested, the highest heat transfer performance was provided by the flat-sided fin tube with fin dimensions close to the theoretically determined optimum values.

Prediction of Heat Transfer Coefficients in Gas Flow Normal to Finned and Smooth Tube Banks

1981 ◽  
Vol 103 (4) ◽  
pp. 705-714 ◽  
Author(s):  
J. C. Biery
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Finned Tube ◽  
Smooth Tube ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Tube Banks

A new method is presented to predict heat transfer coefficients for gas flow normal to smooth and finned tube tanks with triangular pitch. A transformation from the actual tube bank to an equivalent equilateral triangular pitch infinite smooth tube bank (ETP-I-STB) is made. A function of Ch(Ch = NSTNPR2/3NRe0.4) versus (Xt D0)Δ, ratio of transverse pitch to tube diameter for the ETP-I-STB, was developed. The Ch for the equivalent ETP-I-STP then applies to the actual tube bank. The method works with circular finned tubes, smooth tubes, continuous finned tubes, and segmented finned tubes with any triangular pitch. Also, fair predictions were made for in-line tubes with high Reynolds numbers.

Enhanced Condensation of Ethylene Glycol on Single Pin-Fin Tubes: Effect of Pin Geometry

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Hafiz Muhammad Ali ◽  
Adrian Briggs
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Ethylene Glycol ◽  
Heat Transfer Enhancement ◽  
Surface Area ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
Pin Fin ◽  
Fin Tube ◽  
Fin Tubes

This paper presents a fundamental study into the underlying mechanisms influencing heat transfer during condensation on enhanced surfaces. New experimental data are reported for condensation of ethylene glycol at near atmospheric pressure and low velocity on 11 different 3-dimensional pin-fin tubes tested individually. Enhancements of the vapor-side, heat-transfer coefficients were found between 3 and 5.5 when compared to a plain tube at the same vapor-side temperature difference. Heat-transfer enhancement was found to be strongly dependent on the active surface area of the tubes, i.e., on the surface area of the parts of the tube and pin surface not covered by condensate retained by surface tension. For all the tubes, vapor-side, heat-transfer enhancements were found to be approximately twice the corresponding active-area enhancements. The best performing pin-fin tube gave a heat-transfer enhancement of 5.5; 17% higher than obtained from “optimised” two-dimensional fin-tubes reported in the literature and about 24% higher than the “equivalent” two-dimensional integral-fin tube (i.e., with the same fin-root diameter, longitudinal fin spacing and thickness, and fin height). The effects of surface area and surface tension induced enhancement and retention are discussed in the light of the new data and those of previous investigations.

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.

An Experimental Study of Boiling Heat Transfer on Mesh-Covered Fins

2009 ◽  
Author(s):  
Liang-Han Chien ◽  
H.-L. Huang
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Mesh Size ◽  
Wire Mesh ◽  
Finned Tubes ◽  
Enhanced Tubes ◽  
Boiling Heat Transfer Coefficient ◽  
Fin Tube ◽  
Enhanced Boiling ◽  
Fin Tubes

This study investigates a new enhanced boiling surface, which is made by wrapping wire mesh on finned tubes. Pool boiling performance of the new enhanced tubes has been tested in Refrigerant-134a at 5, 10, 20, and 26.67°C saturation temperatures. Brass or copper mesh of 80, 100, or 120 meshes per inch was wrapped on finned tubes of 42 or 60 FPI (fins per inch). The fin heights were either 0.2 mm or 0.4 mm. The test results show that the mesh covered fin tubes significantly enhanced the boiling performance by forming many pores of proper sizes on the surface and sustaining vapor in the tunnels formed by the mesh and fins. The preferred mesh size decreases with decreasing heat flux. The mesh covered on 60FPI fin tube having 0.4 mm fin height and 100 mesh per inch yields the best boiling performance. It enhances the boiling heat transfer coefficient by 7∼8 folds at 5°C as compared with the smooth tube.

Augmentation of Horizontal In-Tube Condensation by Means of Twisted-Tape Inserts and Internally Finned Tubes

1978 ◽  
Vol 100 (1) ◽  
pp. 17-24 ◽  
Author(s):  
J. H. Royal ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Finned Tube ◽  
Smooth Tube ◽  
Twisted Tape ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Augmentation Techniques ◽  
The One

Low pressure steam was condensed inside horizontal tubes of different internal geometries to investigate passive heat transfer augmentation techniques. A smooth tube, the smooth tube having two twisted-tape inserts, and four internally finned tubes were tested. The twisted-tape inserts were found to increase average heat transfer coefficients by as much as 30 percent above smooth tube values on a nominal area basis. The best performing internally finned tube increased average heat transfer coefficients by 150 percent above the nominal smooth tube values. Techniques were developed to correlate the improved heat transfer performance of the two twisted-tape inserts and the four internally finned tubes. The equations developed provide a reasonably accurate description of both the sectional and the average heat transfer coefficients. The finned tube correlation was also reasonably successful in predicting the data from the one other investigation of this augmentation technique for which detailed data were available.

A Comparison of Augmentation Techniques During In-Tube Evaporation of R-113

1991 ◽  
Vol 113 (2) ◽  
pp. 451-458 ◽  
Author(s):  
R. S. Reid ◽  
M. B. Pate ◽  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Heat Fluxes ◽  
Electrical Heating ◽  
Smooth Tube ◽  
Twisted Tape ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Mass Fluxes ◽  
Evaporation Heat ◽  
Enhancement Factors

An experimental study was conducted to determine the potential of three techniques for augmenting in-tube evaporation of refrigerants: high-fin tubes, microfin tubes, and twisted tape inserts. Five tubes with internal fins and one smooth tube with a twisted-tape insert were tested. Additionally, experiments were performed with two reference smooth tubes having diameters similar to the maximum inside diameters of the finned tubes. All experiments involved evaporating Refrigerant 113 (R-113) by direct electrical heating of the tube wall. Local evaporation heat transfer coefficients were measured as a function of quality for a range of mass fluxes and heat fluxes. Enhancement factors were calculated by forming ratios of the heat transfer coefficient for the augmented tube and a smooth tube of the same maximum inside diameter. Mass fluxes, pressure levels, and qualities were fixed when enhancement factors were calculated. For the internally finned tubes the enhancement factors varied from 1.1 to 2.8. An internally finned tube having helical spiral angles of 16 deg produced the largest enhancement of heat transfer. The tube with the twisted-tape insert typically had an enhancement factor of about 1.5. Pressure gradient ratios and enhancement performance ratios are also presented.

Numerical Simulation of Heat Transfer Characteristics in Longitudinal Flow Circular Fin Tube Based on Fluent

2013 ◽  
Vol 781-784 ◽  
pp. 2762-2769
Author(s):  
Qian Yang ◽  
Wei Guo Yi ◽  
Qun Song Li
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Simulation Method ◽  
Smooth Tube ◽  
Longitudinal Flow ◽  
Heat Transfer Characteristics ◽  
Fin Tube ◽  
Fin Tubes

Numerical simulation method were performed to comparatively study the heat transfer and resistance characteristics of smooth tubetransversal and longitudinal flow circular fin tube and longitudinal flow slotted umbrella fin tube; researched the flowheat transfer and resistance characteristics of longitudinal flow slotted umbrella fin tube with five different fin angle. Results show that, with the same piping mode and Re number, heat transfer coefficient of longitudinal flow slotted umbrella fin tube is 1.4~1.8 times of smooth tube, heat transfer coefficient of transversal and longitudinal flow circular fin tube is 1.1~1.5 times of smooth tube, longitudinal flow slotted umbrella fin tube with α=105° has the best heat transfer coefficient; the resistance of longitudinal flow slotted umbrella fin tube is 0.25~0.75 times of transversal flow circular fin tube, and higher than longitudinal flow circular fin tube, longitudinal flow slotted umbrella fin tube with α=105° has the lowest resistance of all slotted umbrella fin tubes.

Film Condensation of R-113 on Staggered Bundles of Horizontal Finned Tubes

1992 ◽  
Vol 114 (2) ◽  
pp. 442-449 ◽  
Author(s):  
H. Honda ◽  
B. Uchima ◽  
S. Nozu ◽  
E. Torigoe ◽  
S. Imai
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Three Dimensional ◽  
Film Condensation ◽  
Line Bundles ◽  
Heat Transfer Characteristics ◽  
Finned Tubes ◽  
Flow And Heat Transfer ◽  
Fin Tubes ◽  
Annular Fins

Film condensation of R-113 on staggered bundles of horizontal finned tubes with vertical vapor downflow was experimentally investigated. Two tubes with flat-sided annular fins and four tubes with three-dimensional fins were tested. The condensate flow and heat transfer characteristics were compared with the previous results for in-line bundles of the same test tubes and a staggered bundle of smooth tubes. The decrease in heat transfer due to condensate inundation was most significant for the in-line bundles of the three-dimensional fin tubes, whereas the decrease was very slow for both the staggered and in-line bundles of the flat-sided fin tubes. The predictions of the previous theoretical model for a bundle of flat-sided fin tubes agreed fairly well with the measured data at a low vapor velocity. The highest heat transfer performance was provided by the staggered bundle of flat-sided fin tubes with fin dimensions close to the theoretically determined optimum values.

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