Effect of Fin Structure on the Condensation of R-134a, R-1234ze(E), and R-1233zd(E) Outside the Titanium Tubes

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Wen-Tao Ji ◽  
Shuai-Feng Mao ◽  
Guo-Hun Chong ◽  
Chuang-Yao Zhao ◽  
Hu Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Three Dimensional ◽  
Saturation Temperature ◽  
Finned Tube ◽  
Finned Tubes ◽  
Enhanced Tubes ◽  
Enhanced Tube ◽  
Condensing Heat Transfer ◽  
R 134A

Abstract In order to test the effect of fin structure on the condensing heat transfer of refrigerants outside the low thermal conductivity tubes, condensation of R-134a, R-1234ze(E), and R-1233zd(E) on two enhanced titanium tubes were experimentally investigated. The two tubes have basically the same fin density while the fin structures are different. One tube is a typical low-fin (two-dimensional, 2D), and the other is a three-dimensional (3D) finned tube. In experiment heat flux was in the range of 10–80 kW·m−2. It was found that at higher heat flux, the condensing heat transfer coefficient (HTC) of 3D-finned tubes was apparently lower than that of 2D-enhanced tubes. The condensing HTC of R-134a for the two tubes was the highest. R-1233zd(E) was the lowest. It was shown from experimental results that the condensing HTC for R-1233zd(E) was notably affected by the change of saturation temperature outside the 3D-enhanced tube, but was less affected by the 2D fin structures.

Nucleate Pool Boiling Heat Transfer of R134a and R134a-PVE Lubricant Mixtures on Smooth and Five Enhanced Tubes

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Wen-Tao Ji ◽  
Ding-Cai Zhang ◽  
Nan Feng ◽  
Jian-Fei Guo ◽  
Mitsuharu Numata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Enhanced Tubes ◽  
Mass Fractions

Pool boiling heat transfer coefficients of R134a with different lubricant mass fractions for one smooth tube and five enhanced tubes were tested at a saturation temperature of 6°C. The lubricant used was polyvinyl ether. The lubrication mass fractions were 0.25%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 7.0%, and 10.0%, respectively. Within the tested heat flux range, from 9000 W/m2 to 90,000 W/m2, the lubricant generally has a different influence on pool boiling heat transfer of these six tubes.

Condensation and Evaporation Heat Transfer Characteristics of Low Mass Fluxes in Horizontal Smooth Tube and Three-Dimensional Enhanced Tubes

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Xiang Ma ◽  
Wei Li ◽  
Chuan-cai Zhang ◽  
Zhi-chuan Sun ◽  
David J. Kukulka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Three Dimensional ◽  
Saturation Temperature ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Evaporation Heat ◽  
Enhanced Tubes ◽  
Evaporation Heat Transfer ◽  
Enhanced Surface

Abstract An experimental investigation of condensation and evaporation heat transfer characteristics was performed in 15.88-mm-OD and 12.7-mm-OD smooth and three-dimensional enhanced tubes (1EHT, 3EHT) using R134A and R410A as the working fluid. The enhanced surface of the 1EHT tube is made up of dimples and a series of petal arrays; while the 3EHT tube is made up of rectangular cavities. Evaluations are performed at a saturation temperature of 45 °C, over the quality range of 0.8–0.2 for condensation; while for evaporation the saturation temperature was 6 °C and the quality ranged from 0.2 to 0.8. For condensation, the enhancement ratio (enhanced tube/smooth tube) of the heat transfer coefficients was 1.42–1.95 for the mass flux ranging from 80 to 200 kg/m2s; while for evaporation, the heat transfer enhancement ratio is 1.05–1.42 for values of mass flux that range from 50 to 180 kg/m2s. Furthermore, the 1EHT tube provides the best condensation and evaporation heat transfer performance, for both working fluids at the mass flux considered. This performance is due to the dimples in the enhanced surface that produce interface turbulence; additionally, the increased surface roughness causes additional disturbances and secondary flows near the boundary, producing higher heat fluxes. The main objective of this study was to evaluate the heat transfer enhancement of two enhanced tubes when using R134A and R410A as a function of mass flux, saturation temperature, and tube diameter. As a result of this study, it was determined that the heat transfer coefficient decreases with an increase in saturation temperature and tube diameter.

Condensation and Evaporation Heat Transfer Characteristics in Horizontal Smooth and Three-Dimensional Enhanced Tubes

2020 ◽  
Author(s):  
Jianghui Zhang ◽  
Yu Guo ◽  
Chuancai Zhang ◽  
Yan He ◽  
David J. Kukulka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Saturation Temperature ◽  
Secondary Flows ◽  
Outer Diameter ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Evaporation Heat ◽  
Enhanced Tubes ◽  
Evaporation Heat Transfer

Abstract An experimental investigation of condensation and evaporation heat transfer characteristics was performed in a smooth tube and two enhanced tubes (1EHT, 3EHT) using R134A as refrigerant. All tested tubes have the same inner diameter of 14.68mm and outer diameter of 15.88mm. The enhanced surface of the 1EHT tube is made up by dimples and a series of petal arrays, while that of 3EHT tube is rectangular cavities. The test runs are performed at a saturation temperature of 45°C, over the quality range of 0.8–0.2 for condensation and at a saturation temperature of 6°C, over the quality range of 0.1–0.6 for evaporation. For evaporation, the heat transfer coefficient ratio (hEHT/hs) is approximately 1.2–1.4 for mass from 50–90 kg/m2s. For condensation, the 1EHT tube provides the best condensation heat transfer performance. This is mainly due to the dimples and rectangular cavities that increase heat transfer surface area and interface turbulence, producing additional disturbances, secondary flows near the boundary and flow separation.

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.

scholarly journals Experimental Investigation of Condensation Heat Transfer Characteristics of R-134a Vapor in Horizontal Heat Exchanger

2018 ◽  
Vol 26 (6) ◽  
pp. 16-31
Author(s):  
Ahmed Jasim Hamad ◽  
Rasha Abdulrazzak Jasim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Vapor Quality ◽  
Test Conditions ◽  
R 134A ◽  
The Heat Transfer Coefficient

An experimental investigation of refrigerant R-134a two-phase flow condensation heat transfer coefficient and pressure drop in condenser tube section of refrigeration system under different operating conditions is presented. The experimental and theoretical investigations are based on test conditions in range of 10 -17 kW/m2 for heat flux, 42-63 kg/m2s for mass flux, vapor quality 1-0.03 and saturation temperature 44 to 49˚C. The experimental tests are conducted on test rig supplied with a test section to simulate the water cooled double pipe heat exchanger, which is designed and constructed in the present work. “The experimental results have revealed that, the heat flux and mass flux have significant impacts on the heat transfer coefficient. “The heat transfer coefficient was increased with increase in heat flux and mass flux at prescribed test conditions, where the enhancement in heat transfer coefficient was about 47% and 14% for relatively higher heat flux and mass flux, respectively. “The enhancement in the heat transfer coefficient was about 51% for relatively lower saturation temperature 45.97˚C and 43% for higher vapor quality 0.88 compared to other values at constant test conditions. “The pressure drop was higher in the range of 12% and 49% for relatively higher mass flux and heat flux respectively. “The present work results have validated by comparison with predictive models and with similar research work results and the comparison has revealed  an acceptable agreement.

Condensation of R-134a on Horizontal Enhanced Tubes Having Three-Dimensional Roughness

2016 ◽  
Vol 24 (02) ◽  
pp. 1650013 ◽  
Author(s):  
Nae-Hyun Kim
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
High Heat ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Process Industries ◽  
High Heat Transfer ◽  
Enhanced Tubes ◽  
R 134A ◽  
Geometric Variation

Enhanced tubes are widely used in shell and tube condensers of refrigeration, air-conditioning and process industries because of their high heat transfer performance. In this study, condensation heat transfer tests were conducted for four three-dimensional enhanced tubes having different fin density and fin height using R-134a. The satuartion temperature was 40[Formula: see text]C. The heat transfer was significantly enhanced by the present enhanced geometry. At 5[Formula: see text]K wall subcooling, the enhancement ratio is 6.3 for 1654[Formula: see text]fpm, 4.6 for 1575[Formula: see text]fpm, 4.0 for 1496[Formula: see text]fpm and 3.3 for 1102[Formula: see text]fpm tubes. Within the geometric variation of the present study, the condensation heat transfer coefficient increased with the increase of fin density and of fin height. The heat transfer coefficients of the 1654[Formula: see text]fpm tube were approximately the same as those of the commercial three-dimensional enhanced tube Turbo-C.

Comparison Between Numerical and Experimental Gas Side Heat Transfer and Pressure Drop of a Tube Bank With Solid and Segmented Circular I-Fins

2012 ◽  
Author(s):  
Rene Hofmann ◽  
Heimo Walter
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Tube Bundle ◽  
Three Dimensional ◽  
Finned Tube ◽  
Three Dimensional Model ◽  
Finned Tubes ◽  
Numerical Predictions ◽  
Staggered Arrangement ◽  
Flow Experiments

In the present work, a comparison between numerical and experimental gas side heat transfer and pressure drop for a tube bundle with solid and segmented circular finned tubes in a staggered arrangement is investigated. For the numerical simulations a three dimensional model of the finned tube are applied. Renormalization group theory (RNG) based k–ε turbulence model was used to calculate the turbulent flow. Experiments have been carried out to validate the numerical predictions. The numerical results for the Nu-number and pressure drop coefficient show a good agreement with the data from measurement. A comparison between solid and segmented finned tubes from the global calculation of the Nu-numbers within the analyzed Re-range shows an enhancement by applying segmented finned tubes rather than finned tubes with solid fins.

Experimental and Numerical Investigation of the Gas Side Heat Transfer and Pressure Drop of Finned Tubes—Part II: Numerical Analysis

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Rene Hofmann ◽  
Heimo Walter
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Study ◽  
Three Dimensional ◽  
Finned Tube ◽  
Renormalization Group Theory ◽  
Tube Material ◽  
Finned Tubes ◽  
Steady State Temperature ◽  
Volume Method

The heat transfer and pressure drop behavior of segmented circular and helical as well as solid finned tubes are investigated in a three-dimensional numerical study. The simulation is carried out using a finite volume method for calculating the steady-state temperature and flow field of the fluid as well as the temperature distribution of the tube material. For modeling the turbulence, the k-ε turbulence model based on the renormalization group theory (RNG) is used to resolve the near-wall treatment between adjacent fins. All simulations are performed in the Re range between 3500 ≤ Re ≤ 50,000. The influence of Reynolds number and fin geometry (segmented or solid and circular or helical) on the local and global averaged heat transfer and pressure drop was studied. A comparison between solid and segmented finned tube has shown that the heat transfer and pressure drop for the segmented finned tubes is higher. The numerical results are compared with experimental data.

Vapor Bubble Interaction With a Superheated Wall

2017 ◽  
Author(s):  
M. Wasy Akhtar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Vapor Bubble ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Saturation Temperature ◽  
Bubble Wall ◽  
Initial Flow ◽  
Transfer Rates ◽  
Wall Interaction

Sliding bubbles are known to augment heat transfer rates on the surface on which they slide. The pre-cursor problem — the bubble approaching an inclined superheated wall provides the initial flow and thermal field for the sliding bubble problem. An FC-87 vapor bubble rising in a thermally stratified flow field is simulated along with the bubble wall interaction effects. The simulation is conducted on a dynamic octree grid for improved accuracy and efficiency. The evolution of the bubble shape and the wake behind the rising bubble is captured in a three-dimensional model, which takes into account bubble growth due to superheat at the liquid-vapor interface and the effect of interface heat flux on the local saturation temperature. After the first bubble-wall interaction, a microlayer tens of microns thick forms between the bubble and the wall; a thermal wake develops behind the bubble as it begins to slide against the wall. The predicted shapes, Re and Weber numbers and microlayer thicknesses show excellent agreement in comparison to experimental data from other researchers. Evolution of the flow and temperature fields were examined with the aid of contours of vapor volume fraction and iso-lines of mixture temperature superimposed on three-dimensional shapes of the bubble. Overall bubble dynamics and microlayer dynamics, including microlayer thickness and microlayer heat flux, are presented as functions of time. Using the wall, microlayer and wake heat transfer rates, an enhancement of the total wall heat flux was found to be on the order of 6 times the background heat flux. This work describes the bubble evolution through the first rebounding in detail, but the dynamic octree adaption algorithm lends itself to study of the long-term dynamics well into the sliding regime. The technique can also be used to investigate other multiphase flow phenomena — especially bubble coalescence and breakup.

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