Stratified Flow Condensation of CO2 in a Tube at Low Temperatures

2015 ◽  
Vol 789-790 ◽  
pp. 184-192
Author(s):  
Pei Hua Li ◽  
Joe Deans ◽  
Stuart Norris
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Stratified Flow ◽  
Heat Transfer Process ◽  
Film Condensation ◽  
Significant Feature ◽  
Transfer Coefficients ◽  
Flow Condensation

This study presents an experimental investigation of CO2flowing condensation at the saturation temperature of-10°C, mass flux in the range from 40 to 60kgm-2s-1and vapour quality ranging from 0.2 to 0.8, in a 6.52mm inside diameter horizontal tube. Previous research on refrigerant condensation has shown that under these conditions, CO2two phases are expected to develop as a stratified flow. The significant feature of the stratified flow heat transfer is vapour film condensation in the upper region which dominates the overall heat transfer process. Test series in this study confirm that the saturation-to-tube wall temperature difference has a significant influence on the condensing heat transfer coefficient when the temperature difference is within 3K. Comparisons between the experimental results and the predictions by the Dobson, Cavallini and Thome models show that CO2stratified flow condensation heat transfer coefficients are over-predicted by these models with mean deviations of 104%, 81% and 127%, respectively.

An Analytical Study of Laminar Film Condensation: Part 2—Single and Multiple Horizontal Tubes

1961 ◽  
Vol 83 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Michael Ming Chen
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Horizontal Tube ◽  
Vertical Tube ◽  
Film Condensation ◽  
Transfer Coefficients ◽  
Inertia Effects ◽  
Horizontal Tubes ◽  
Laminar Film ◽  
Laminar Film Condensation

The boundary-layer equations for laminar film condensation are solved for (a) a single horizontal tube, and (b) a vertical bank of horizontal tubes. For the single-tube case, the inertia effects are included and the vapor is assumed to be stationary outside the vapor boundary layer. Velocity and temperature profiles are obtained for the case μvρv/μρ ≪ 1 and similarity is found to exist exactly near the top stagnation point, and approximately for the most part of the tube. Heat-transfer results computed with these similar profiles are presented and discussed. For the multiple-tube case, the analysis includes the effect of condensation between tubes, which is shown to be partly responsible for the high observed heat-transfer rate for vertical tube banks. The inertia effects are neglected due to the insufficiency of boundary-layer theory in this case. Heat-transfer coefficients are presented and compared with experiments. The theoretical results for both cases are also presented in approximate formulas for ease of application.

Analysis and Prediction of Condensation Heat Transfer of the Zeotropic Mixture R-125/236ea

2000 ◽  
Author(s):  
Alberto Cavallini ◽  
Giuseppe Censi ◽  
Davide Del Col ◽  
Luca Doretti ◽  
Luisa Rossetto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Heat Transfer Coefficients ◽  
On Line ◽  
Zeotropic Mixture ◽  
Film Method ◽  
Experimental Runs

Abstract The high temperature glide mixture R-125/236ea at three mass compositions (28/72%, 46/54%, 63/37%) is tested during condensation against water in a tube-in-tube heat exchanger. The experimental runs to measure the heat transfer coefficients are carried out at saturation temperature ranging from 40°C to 60°C and mass velocities ranging from 100 to 750 kg/(m2 s). A gas chromatograph is used for on-line concentration measurements. By comparing the heat transfer performances of the three compositions to the condensation coefficients previously measured for the two pure components inside a smooth horizontal tube [Cavallini et al. (2000)], the dependence of the heat transfer performance on composition during condensation for a non-azeotropic mixture is investigated. The film method by Colburn and Drew (1937) is applied to predict the experimental coefficients and it is found to underestimate the heat transfer rate, with more conservative results as compared to the equilibrium method by Silver (1947), Bell and Ghaly (1973).

Evaporation of Ammonia in a Smooth Horizontal Tube: Heat Transfer Measurements and Predictions

1999 ◽  
Vol 121 (1) ◽  
pp. 89-101 ◽  
Author(s):  
O. Zu¨rcher ◽  
J. R. Thome ◽  
D. Favrat
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Steel Tube ◽  
Heat Fluxes ◽  
Stainless Steel Tube ◽  
Transfer Coefficients ◽  
Two Phase

Experimental test results for flow boiling of pure ammonia inside horizontal tubes were obtained for a plain stainless steel tube. Tests were run at a nominal saturation temperature of 4°C, nine mass velocities from 20–140 kg/m2 s, vapor qualities from 1–99 percent and heat fluxes from 5–58 kW/m2. Two-phase flow observations showed that the current test data covered the following regimes: fully stratified, stratified-wavy, intermittent, annular, and annular with partial dryout. The Kattan-Thome-Favrat flow boiling model accurately predicted the local heat transfer coefficients measured in all these flow regimes with only two small modifications to their flow map (to extend its application to G < 100 kg/m2 s). Their flow boiling model was also successfully compared to the earlier ammonia flow boiling data of Chaddock and Buzzard (1986). The Gungor-Winterton (1987) correlation instead gave very poor accuracy for ammonia.

Effect of Temperature Difference on In-Tube Condensation Heat Transfer Coefficients

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Malcolm Macdonald ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Film Theory ◽  
Horizontal Tube ◽  
Condensation Heat Transfer ◽  
Effect Of Temperature ◽  
Test Fluid ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Underlying Mechanisms

The effect of temperature difference (Tsat − Tcoolant) on condensation heat transfer coefficients inside horizontal tubes is investigated in detail. Condensation experiments are conducted on propane inside a 7.75 mm horizontal tube at four temperature differences between the test fluid and coolant at three mass fluxes and four saturation temperatures. The heat transfer coefficient is shown to increase with temperature difference, with this effect diminishing with larger temperature differences, and being most significant at higher saturation temperatures. Heat transfer coefficients at the low-reduced pressures (Pr = 0.25) corresponding to lower saturation temperatures (30 °C) are mostly unaffected by the temperature difference. Subcooling of the condensate is expected to increase heat transfer coefficients at the larger temperature differences. Flow visualization studies are used to explain the inadequacy of the Nusselt film theory for the conditions investigated. The underlying mechanisms are also used to explain why the correlations from the literature do not predict the observed trend, and a new correlation to account for the effect of temperature difference is developed.

Film Condensation of R-134a on Tube Arrays With Plain and Enhanced Surfaces: Part II—Empirical Prediction of Inundation Effects

2005 ◽  
Vol 128 (1) ◽  
pp. 33-43 ◽  
Author(s):  
D. Gstoehl ◽  
J. R. Thome
Keyword(s):  
Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Process ◽  
Finned Tube ◽  
Film Condensation ◽  
Condensation Temperature ◽  
Asymptotic Model ◽  
Transfer Coefficients ◽  
Empirical Prediction ◽  
R 134A

New predictive methods for R-134a condensing on vertical arrays of horizontal tubes are proposed based on visual observations revealing that condensate is slung off the array of tubes sideways and significantly affects condensate inundation and thus the heat transfer process. For two types of three-dimensional (3D) enhanced tubes, the Turbo-CSL and the Gewa-C, the local heat flux is correlated as a function of condensation temperature difference, the film Reynolds number, the tube spacing, and liquid slinging effect. The measured heat transfer data of the plain tube were well described by an existing asymptotic model based on heat transfer coefficients for the laminar wavy flow and turbulent flow regimes or, alternatively, by a new model proposed here based on liquid slinging. For the 26fpi low finned tube, the effect of inundation was found to be negligible and single-tube methods were found to be adequate.

An Experimental Study of Flow Condensation Heat Transfer Inside Circular and Rectangular Mini-Channels

2004 ◽  
Author(s):  
J. S. Shin ◽  
M. H. Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Experimental Apparatus ◽  
Mini Channels ◽  
Flow Condensation

By using unique experimental techniques and careful construction of the experimental apparatus, the characteristics of the local heat transfer were investigated using the condensing R134a two-phase flow, in horizontal single mini-channels. The circular channels (Dh = 0.493, 0.691, and 1.067 mm) and rectangular channels (Dh = 0.494, 0.658, and 0.972 mm) were tested and compared. Tests were performed for a mass flux of 100, 200, 400, and 600 kg/m2s, a heat flux of 5 to 20 kW/m2, and a saturation temperature of 40°C. In this study, effect of heat flux, mass flux, vapor qualities, hydraulic diameter, and channel geometry on flow condensation were investigated and the experimental local condensation heat transfer coefficients are shown. The experimental data of condensation Nusselt number are compared with existing correlations.

Heat Transfer Coefficient in Falling Film Evaporators With Different Tube Arrangements

2012 ◽  
Author(s):  
Shengqiang Shen ◽  
Gangtao Liang ◽  
Yali Guo ◽  
Xingsen Mu ◽  
Rui Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Falling Film ◽  
Overall Heat Transfer Coefficient ◽  
Spray Density ◽  
Total Temperature

A set of experimental facilities were set up to measure overall heat transfer coefficient of horizontal-tube falling film evaporators with triangular, rotated square and square-pitch bundles. Effect of spray density, saturation temperature, total temperature difference and inlet steam velocity on the overall heat transfer coefficient K is studied respectively. The tubes are made of HAL77-2A aluminium brass with an outer diameter of 25.4 mm. Fluids inside and outside the tubes are steam and fresh water respectively. The results indicate that growth of spray density and saturation temperature helps to increase the K. The K could also be increased by reducing the total temperature difference. However, the impact of the inlet steam velocity on the K is less significant. The K in the evaporator with rotated square-pitch arrangement is supreme. Furthermore, space distribution of local overall heat transfer coefficient K̃ in the evaporators is also discussed. Based on this investigation, basic engineering design information will be provided to establish the governing parameters for horizontal-tube falling film evaporator in the field of seawater desalination.

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

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