Shell-Side Condensation Characteristics of R410A on Horizontal Enhanced Tubes

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Weiyu Tang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Diffusion Resistance ◽  
Outer Diameter ◽  
Vapor Quality ◽  
Enhanced Tubes ◽  
The Heat Transfer Coefficient

Abstract An experimental investigation into heat transfer characteristics during condensation on two horizontal enhanced tubes (EHTs) was conducted. All the tested EHTs s have similar geometries with an outer diameter of 12.7 mm, and a plain tube was also tested for comparison. Investigated enhanced surfaces consist of dimples, protrusions, and grooves, which may produce more flow turbulence and enhanced the liquid drainage effect. The effects of mass fluxes and vapor quality were compared and analyzed. Test conditions were as follows: saturation temperature fixed at 45 °C, mass flux varying from 100 to 200 kg m−2 s−1, and vapor quality ranging from 0.3 to 0.8. The heat transfer coefficient was presented, and the results show that the proposed enhanced surfaces seem to have worse performance than the conventional tubes when the mass flux is less than 150 kg m−2 s−1, while one of the enhanced tubes (2EHT-1) produce an enhanced ratio of 1.03–1.14 when G = 200 kg m−2 s−1. Besides, it was found that the heat transfer coefficient increases with increasing vapor quality, which can be attributed to the increasing diffusion resistance. Mass flux seems to have little effect on the heat transfer performance of smooth tubes, while that of 1EHT increases obviously with increasing mass flux, especially for high vapor qualities.

Experimental Study on Flow Evaporation Heat Transfer Characteristics Inside Horizontal Three-Dimensional Enhanced Tubes

2018 ◽  
Author(s):  
Wei Li ◽  
Chuancai Zhang ◽  
Zhichuan Sun ◽  
Zhichun Liu ◽  
Lianxiang Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Three Dimensional ◽  
Outer Diameter ◽  
Evaporation Heat ◽  
Enhanced Tubes ◽  
Evaporation Heat Transfer ◽  
The Heat Transfer Coefficient

Experimental investigation was performed to measure the evaporation heat transfer coefficients of R410A inside three three-dimensional enhanced tubes (1EHT-1, 1EHT-2 and 4LB). The inner and outer enhanced surface of the 4LB tube is composed by arrays of grooves and square pits, while 1EHT-1 tube and 1EHT-2 tube consist of longitudinal ripples and dimples of different depths. All these tubes have an inner diameter of 8.32 mm and an outer diameter of 9.52 mm. Experiment operational conditions are conducted as follows: the saturation temperature is 279 K, the vapor quality ranges from 0.2 to 0.8, and the mass flux varies from 160 kg/(m2·s) to 380 kg/(m2·s). With the mass flux increasing, the heat transfer coefficient increases accordingly. The heat transfer coefficient of 1EHT-2 is the highest of all three tubes, and that of 1EHT-1 is the lowest. The heat transfer coefficient of 4LB ranks between the 1EHT-1 and 1EHT-2 tube. The reason is that the heat transfer areas of the 1EHT-2 and 4LB tube are larger than that of 1EHT-1 and interfacial turbulence is enhanced in 1EHT-2.

Comparison of Evaporation and Condensation Characteristics Among Three Enhanced Tubes

2018 ◽  
Author(s):  
Kunrong Shen ◽  
Zhichuan Sun ◽  
Xiaolong Yan ◽  
Wei Li ◽  
David J. Kukulka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Heat Transfer Performance ◽  
Saturation Temperature ◽  
Transfer Performance ◽  
Vapor Quality ◽  
Enhanced Tubes

With the current ozone depletion and global warming issues, it is critical to develop systems with better heat transfer performance and nontoxic refrigerants. An experimental investigation was performed to evaluate convective condensation and evaporation heat transfer characteristics using R410A at low mass fluxes. Experiments were conducted in a 12.0-mm O.D. horizontal smooth tube, and three enhanced tubes: 2EHT1 tube, 2EHT2 tube and 1EHT1 tube (O.D. 12.7 mm), with different sizes and shapes of dimple/protrusion and petal arrays. Refrigerant inlet quality varied in this study. Single phase experiment was conducted before the two-phase flow measurement. In-tube evaporation measurements of R410A were reported for saturation temperature at 6°C with vapor quality in the range of 0.2 to 0.9, and mass flux varied from 60 to 200 kg/m2s. Condensation tests were performed at saturation temperature of 45°C, vapor quality of 0.9 to 0.2, and mass flux of 60 to 260 kg/m2s. For evaporation with mass flux less than 200 kg/m2s, heat transfer coefficient of the 2EHT2 tube, 2EHT1 tube and 1EHT1 tube were greater than the experimental HTC (heat transfer coefficient) of smooth tube results by an average factor of 1.71, 1.69 and 1.87, respectively. Pressure drop in the 2EHT2 tube was 5% higher than the 2EHT1 tube and 1EHT1 tube. For condensation, when mass flux was less than 200 kg/m2s, the 1EHT1 tube showed obvious enhancement in heat transfer coefficient, while the pressure drop in the 1EHT1 tube was slightly 3–5% higher than that of the 2EHT1 tube and the 2EHT2 tube. In conclusion, for mass flux below 200 kg/m2s, the 1EHT1 tube presented the best heat transfer performance among others with R410A as the refrigerant.

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.

Experimental Investigation of Condensation Heat Transfer and Adiabatic Pressure Drop Characteristics Inside a Microfin and Smooth Tube

2017 ◽  
Vol 25 (03) ◽  
pp. 1750027 ◽  
Author(s):  
M. Mostaqur Rahman ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Frictional Pressure Drop

Experiments on condensation heat transfer and adiabatic pressure drop characteristics of R134a were performed inside smooth and microfin horizontal tubes. The tests were conducted in the mass flux range of 50[Formula: see text]kg/m2s to 200[Formula: see text]kg/m2s, vapor quality range of 0 to 1 and saturation temperature range of 20[Formula: see text]C to 35[Formula: see text]C. The effects of mass velocity, vapor quality, saturation temperature, and microfin on the condensation heat transfer and frictional pressure drop were analyzed. It was discovered that the local heat transfer coefficients and frictional pressure drop increases with increasing mass flux and vapor quality and decreasing with increasing saturation temperature. Higher heat transfer coefficient and frictional pressure drop in microfin tube were observed. The present experimental data were compared with the existing well-known condensation heat transfer and frictional pressure drop models available in the open literature. The condensation heat transfer coefficient and frictional pressure drop of R134a in horizontal microfin tube was predicted within an acceptable range by the existing correlation.

Convective Boiling of R-22 in a Flat Aluminum Multi-Minichannel Tube With Dh = 1.4 mm

2008 ◽  
Author(s):  
Nae-Hyun Kim ◽  
Wang-Kyu Oh ◽  
Jung-Ho Ham ◽  
Do-Young Kim ◽  
Tae-Ryong Shin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
High Mass ◽  
High Heat Flux ◽  
Convective Boiling ◽  
The Heat Transfer Coefficient

Convective boiling heat transfer coefficients of R-22 were obtained in a flat extruded aluminum tube with Dh = 1.41 mm. The test range covered mass flux from 100 to 600 kg/m2 s, heat flux from 5 to 15 kW/m2 and saturation temperature from 5°C to 15°C. The heat transfer coefficient curve shows a decreasing trend after a certain quality (critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique ‘cross-over’ of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kandlikar correlations underpredict the low mass flux and overpredict the high mass flux data.

Convective Boiling of R-22 in a Flat Extruded Aluminum Multi-Port Tube

2004 ◽  
Author(s):  
Nae-Hyun Kim ◽  
Young-Sup Sim ◽  
Chang-Keun Min
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
High Mass ◽  
High Heat Flux ◽  
Convective Boiling ◽  
The Heat Transfer Coefficient

Convective boiling heat transfer coefficients of R-22 were obtained in a flat extruded aluminum tube with Dh = 1.41 mm. The test range covered mass flux from 200 to 600 kg/m2 s, heat flux from 5 to 15 kW/m2 and saturation temperature from 5°C to 15°C. The heat transfer coefficient curve shows a decreasing trend after a certain quality (critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique ‘cross-over’ of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kandlikar correlations underpredict the low mass flux and overpredict the high mass flux data.

A General Correlation for Condensation Heat Transfer in Micro-Fin for Herringbone and Dimple-Texture Tubes

2015 ◽  
Author(s):  
Wei Li ◽  
Si-pu Guo ◽  
Xiao-peng Zhou ◽  
David J. Kukulka ◽  
Jin-liang Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Coefficient Multiplier ◽  
The Heat Transfer Coefficient

An experimental investigation was performed to evaluate the condensation characteristics inside smooth, herringbone and dimple-textured (Vipertex 1EHT) tubes; with the same outer diameter (12.7 mm); using R22 and R410a refrigerants; for a mass flux that ranges from 81 to 178.5 kg/m 2 s. The condensation saturation temperature is 47°C; with an inlet quality of 0.8 and an outlet vapor quality of 0.2. Results indicate that the condensation heat transfer coefficient of the herringbone tube was approximately 3 times that of the smooth tube for R22; and has an enhancement heat transfer factor of 2.3 for R410a. The enhancement heat transfer coefficient multiplier for the textured dimple tube is approximately 2 times that of a smooth tube for R22; and 1.8 for R410a. Severalpreviously reported correlations are used to compare the heat transfer coefficient measurements in the plain tube; while a new equation is proposed to predict the heat transfer coefficient in the herringbone tube.

An Experimental Study of R134a Condensation Heat Transfer in Horizontal Smooth and Enhanced Tubes

2020 ◽  
Author(s):  
Yu Guo ◽  
Zong-bao Gu ◽  
Zahid Ayub ◽  
Wei Li ◽  
Xiang Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Surface Structures ◽  
Condensation Heat Transfer ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Enhanced Tubes

Abstract In this paper, the condensation heat transfer characteristics of R134a inside enhanced tubes using two type of surface structures with different materials was investigated, which were then compared with plain tubes under the same test conditions. The enhanced tubes were: 1EHTa tube with dimpled and petal arrays structure and 1EHTb tube with protrusion and similar petal arrays structure. The experiment was conducted for a mass flux ranging from 100 to 200 kg m−2 s−1 with saturation temperature of 318 K. The inlet and outlet vapor qualities were fixed at 0.8 and 0.2, respectively. The test tubes had the same outer diameter of 12.7 mm. Results showed that the dimpled and protruded surface tubes enhanced the convection condensation heat transfer and the heat transfer coefficient was 1.4 to 1.6 times higher than that of the smooth tube. Heat transfer enhancement of the 1EHTa and 1EHTb tube was mainly due to the complex roughness surface structures that created swirling and increased the interface turbulence. Enhanced tubes exhibited higher performance factors compared to the smooth tube. The average performance factor was 1.3–1.5. As the flow rate increases, there is no significant increase in the condensation heat transfer coefficient. The pressure drop penalty increased with mass flux. Compared with smooth tube, the pressure drop penalty of enhanced tube was larger.

scholarly journals Evaporation Heat Transfer and Pressure Drop of Low-Global Warming Potential Refrigerant HFO-1234yf in 6.95-mm Horizontal Smooth Tube

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6325
Author(s):  
Chang-Hyo Son ◽  
Nam-Wook Kim ◽  
Jung-In Yoon ◽  
Sung-Hoon Seol ◽  
Joon-Hyuk Lee
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Experimental Conditions ◽  
Evaporation Heat ◽  
R 134A ◽  
The Heat Transfer Coefficient

This study investigated the evaporative heat transfer coefficient and pressure drop characteristics of R-1234yf in a horizontal tube with an inner diameter of 6.95 mm under various experimental conditions. The heat transfer coefficient increased with an increase in quality but showed a sharp decrease in the high-quality area. In addition, the heat transfer coefficient increased as the mass flux, heat flux, and saturation temperature increased. Although R-1234yf and R-134a presented similar heat transfer coefficients, that of R-134a was higher. The pressure drop increased with an increase in the quality and mass flux but decreased with an increase in the saturation temperature. The pressure drop of R-134a was larger than that of R-1234yf. In light of the flow pattern diagram by Taitel and Dukler, most of the experiments were included in the annular flow region, and some regions showed intermittent and stratified corrugated flow regions. Kandlikar’s heat transfer coefficient correlation provided the best prediction for the experimental database, with approximately 84% of the predicted data within ±30%. Moreno Quibén and Thome’s equation for pressure drop predicted approximately 88.71% of the data within ±30%.

An Experimental Study of R134a Condensation Heat Transfer in Horizontal Smooth and Enhanced Tubes

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Wei Li ◽  
Yu Guo ◽  
Zong-Bao Gu ◽  
Xiang Ma ◽  
Zahid Ayub ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Surface Structures ◽  
Condensation Heat Transfer ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Enhanced Tubes

Abstract In this paper, the condensation heat transfer characteristics of R134a inside enhanced tubes using two types of surface structures with different materials were investigated, which were then compared with plain tubes under the same test conditions. The enhanced tubes were: 1EHTa tube with dimpled and petal arrays structure and 1EHTb tube with protrusion and similar petal arrays structure. The experiment was conducted for a mass flux ranging from 100 to 200 kg m−2 s−1 with saturation temperature of 318.15 K. The inlet and outlet vapor qualities were fixed at 0.8 and 0.2, respectively. The test tubes had the same outer diameter of 12.7 mm. Results showed that the dimpled and protruded surface tubes enhanced the convection condensation heat transfer and the heat transfer coefficient was 1.4–1.6 times higher than that of the smooth tube. Heat transfer enhancement of the 1EHTa and 1EHTb tube was mainly due to the complex roughness surface structures that created swirling and increased the interface turbulence. The condensation heat transfer coefficient increased slightly with increasing mass flux. The pressure drop penalty was found to increase as mass flux increased. Compared with the smooth tube, the pressure drop of Cu-1EHTa tube, SS-1EHTa tube, and Cu-1EHTb tube were 1.15, 1.21, and 1.14 of smooth tube, respectively. Enhanced tubes exhibited higher performance factors (PFs) compared to the smooth tube. The average PF was 1.3–1.5. A new correlation of heat transfer coefficient has been developed within ±15% error band.

Sign in / Sign up

Export Citation Format

Share Document