Shell-Side Flow Condensation of R410A on Horizontal Tubes at Low-Mass Fluxes

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Wei Li ◽  
Xu Chen ◽  
Jing-Xiang Chen ◽  
Zhi-Chuan Sun ◽  
Terrence W. Simon
Keyword(s):  
Saturation Temperature ◽  
Superior Performance ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Vapor Quality ◽  
Mass Fluxes ◽  
Enhanced Tube ◽  
Low Mass ◽  
Side Flow

An investigation of refrigerant R410A condensation on a shell and tube heat exchanger simulation is conducted. Tests are on the outside of a horizontal smooth tube, a herringbone tube, and a newly developed three-dimensional-enhanced tube, called the enhanced tube (EHT) tube, all of the same outer diameter. Experiments were conducted at a constant saturation temperature of 45 °C, a constant inlet vapor quality of 0.8, a constant outlet vapor quality of 0.1, and mass fluxes ranging from 5 kg/(m2 s) to 50 kg/(m2 s). At low-mass velocities, the smooth tube shows superior performance over the herringbone tube and the EHT tube. The cause might lie in surface tension effects that result in liquid inundation at the lower portion of the tube, thickening the film on the tube and deteriorating the heat transfer performance. Analyses were conducted to find a suitable correlation of the experimental data.

Experimental Study of Evaporation Frictional Pressure Drop in Horizontal Enhanced Tube

2020 ◽  
Author(s):  
Zong-bao Gu ◽  
Yu Guo ◽  
Xiang Ma ◽  
Yan He ◽  
Wei Li
Keyword(s):  
Pressure Drop ◽  
Mass Flux ◽  
Three Dimensional ◽  
Saturation Temperature ◽  
Smooth Tube ◽  
Working Fluid ◽  
Outer Diameter ◽  
Vapor Quality ◽  
Frictional Pressure Drop ◽  
Enhanced Tube

Abstract An experimental investigation for evaporation frictional pressure drop in horizontal enhanced tubes with an outer diameter of 12.7 mm was studied using R410A as the working fluid. The experiment was conducted: the mass flux in the range of 100 kg/(m2s) to 200 kg/(m2s), over a vapor quality range of 0.2 to 0.8, an average saturation temperature at 279 K. The inner tubes were the tested tubes, which included a smooth tube, a three-dimensional enhanced tube (a tube enhanced by protrusions and petal arrays background patterns), respectively. The results show that the frictional pressure drop increases with the mass flux increasing. Moreover, the frictional pressure drop of the enhanced tube is 1.6∼2.4 times than that of the smooth tube. This is mainly due to the increase of the flow resistance inside the enhanced tube, which is caused by the increased interfacial turbulence, flow separation and secondary flow. It is also observed that the pressure drop increases with vapor quality increasing. In addition, some existing correlations are used to compare with our experimental data and verify their accuracy. A new modified correlation is proposed to predict the frictional pressure drop of EHT-1 tube.

Condensation Heat Transfer Characteristics on the Outside of Horizontal Smooth, Herringbone and Enhanced Surface 1EHT Tubes

2015 ◽  
Author(s):  
Xiao-peng Zhou ◽  
David J. Kukulka ◽  
Jing Li ◽  
Jian-Jun Sun ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Thermal Systems ◽  
Low Mass ◽  
Enhanced Surface

Heat transfer enhancement plays an important role in improving energy efficiency and developing high performance thermal systems. Phase-change heat transfer processes take place in thermal systems; typically heat transfer enhanced tubes are used in these systems and they are designed to increase heat transfer coefficients in evaporation and condensation. Enhanced heat transfer tubes are widely used in refrigeration and air-conditioning applications in order to reduce cost and create a smaller footprint of the application. Microfins, roughness and dimples are often incorporated into the inner surface of tubes in order to enhance heat transfer performance. Under many conditions, enhanced surface tubes can recover more energy and provide the opportunity to advance the design of many heat transfer products. Convective condensation heat transfer and pressure loss characteristics were investigated for R410A on the outside of: (i) a smooth tube (outer diameter 12.7 mm); (ii) an external herringbone tube (fin root diameter 12.7 mm); and (iii) the 1EHT tube (outer diameter 12.7 mm) for very low mass fluxes. Data was obtained for values of mass flux ranging from 8 to 50 kg/(m2 s); at a saturation temperature of 318 K; with an inlet quality of 0.8 (±0.05) and an outlet quality of 0.1 (±0.05). In a comparison of heat transfer at a low mass flux, both the 1EHT tube and the herringbone tube did not perform as well as the smooth tube. And it’s difficult to analyze the reason for this strange phenomenon.

Comparison of R410A Condensation Heat Transfer Performance on Three Horizontal Tubes

2017 ◽  
Author(s):  
Xu Chen ◽  
Xiaoqiang Hong ◽  
Wei Li ◽  
David J. Kukulka
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Heat Transfer Performance ◽  
Smooth Tube ◽  
High Mass ◽  
Outer Diameter ◽  
Transfer Performance ◽  
Vapor Quality ◽  
Helical Angle

An experimental investigation of R410A condensation outside a horizontal smooth tube, a herringbone tube and a newly developed enhanced surface EHT tube has been conducted. The herringbone tube has a fin root diameter of 11.43 mm, a helical angle of 21.3 °, 48 fins with a fin height of 0.262 mm and an apex angle of 36 °, the EHT tube has an outer diameter of 11.5 mm with special structure, while the smooth tube has an outer diameter of 11.43 mm. Experiments were taken at a constant saturation temperature of 45 °C, a constant inlet vapor quality of 0.8 and a constant outlet vapor quality of 0.1; mass flux ranging from 5 kg/(m2.s) to 250 kg/(m2.s). Those tubes have different heat transfer performance at different mass flux. The EHT tube has the least heat transfer coefficient than the other two tubes at a low mass flux, while at a high mass flux, the enhanced tubes have a better heat transfer performance than the smooth tube. Heat transfer performance combined with pressure drop measurements reveal that the herringbone tube generally has a better heat transfer performance than the EHT tube, pointing out the herringbone is a wise choice for shell side condensation instead of the EHT tube. Characteristic analysis is made to account for various phenomena in this series of experiments.

Experimental Research on Condensation Outside a Horizontal Tube at Low Mass Fluxes

2015 ◽  
Author(s):  
Wei Li ◽  
Xu Chen
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Mass Velocity ◽  
Smooth Tube ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Helical Angle ◽  
Low Mass

An experimental investigation of R410a condensation outside a horizontal herringbone tube and a smooth tube has been conducted. The herringbone tube has a fin root diameter of 11.43 mm, a helical angle of 21.3 °, 48 fins with a fin height of 0.262 mm and an apex angle of 36 °, while the smooth tube has an inner diameter of 11.43 mm. Experiments were taken at a constant saturation temperature of 45°C, an inlet vapor quality of 0.8 and an outlet vapor quality of 0.1. The mass velocity ranged from 5 kg/(m2.s) to 50 kg/(m2.s). The outside condensation heat transfer coefficients for the herringbone tube vary from 617.53 W/(m2.K) to 856.37 W/(m2.K), whereas the heat transfer coefficients for the smooth tube vary from 1066.29 W/(m2.K) to 1413.09 W/(m2.K), nearly 1.5 times higher than the data of the herringbone tube. At such a low mass velocity, the smooth tube seems superior to the herringbone tube, which has not been discovered yet. The cause of such phenomenon might consist in the surface tension which plays a vital role in the condensation process. Under a low mass velocity, the surface tension results in the retention of liquid on the lower part of the tube, which thickens the film on the tube and worsens the heat transfer. Several calculations were made to find a suitable correlation for this experiment, aiming to find the point where the herringbone tube starts to lose its enhancement function.

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.

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.

Evaluation of Existing Frictional Pressure Drop Correlations During Condensation of R410A in Four Horizontal Tubes

2019 ◽  
Author(s):  
Kunrong Shen ◽  
Zhichuan Sun ◽  
Wei Li ◽  
Xiang Ma ◽  
Yan He ◽  
...  
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Flow Model ◽  
Saturation Temperature ◽  
Separated Flow ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Homogeneous Flow ◽  
Frictional Pressure Drop ◽  
Horizontal Tubes

Abstract Results are presented here from an experimental investigation on tube side condensation characteristics that took place in four tested tubes — 1EHT-1, 1EHT-2, 4LB and a smooth tube. The equivalent outer diameter of the tubes was 9.52 mm and the inner diameter was 8.32 mm. Condensation tests were conducted using refrigerant R410A at a saturation temperature of 318K, over a mass flow range of 150–450 kgm−2s−1, with inlet and outlet vapor quality of 0.8 and 0.2, respectively. Pressure drop data of the four tested tubes were collected to evaluate five identified prediction correlations based on the separated flow model and the homogeneous flow model. For 1EHT-2 and the smooth tube, all the listed correlations manage to present predictions with the Mean Absolute Relative Deviation (MARD) less than 30%, while they underestimate the frictional pressure drop of the 4LB tube with MARD exceeding 40% averagely. Regarding the experimental data, it is found that the Muller-Steinhagen and Heck correlation presents the most accurate and stable prediction for the 4 tested tubes. The listed homogeneous flow correlations can provide acceptable predictions with MARD ranging from 25% to 40% under a few conditions, but their average predictive accuracies are inferior to that of the separated flow correlations. Consequently, the separated flow approach performs better than the homogeneous flow model in the prediction of frictional pressure drop for our experimental data.

R-22 and Zeotropic R-22/R-142b Mixture Condensation in Microfin, High-Fin, and Twisted Tape Insert Tubes

2002 ◽  
Vol 124 (5) ◽  
pp. 912-921 ◽  
Author(s):  
F. J. Smit ◽  
J. P. Meyer
Keyword(s):  
Heat Transfer ◽  
Saturation Temperature ◽  
Twisted Tape ◽  
Outer Diameter ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Smooth Tubes ◽  
Enhancement Method

Using mixtures of the zeotropic refrigerant mixture R-22/R-142b, a series of experiments was performed to determine the sectional and average heat transfer coefficients. Experiments were also conducted to compare three different heat transfer enhancement methods to that of smooth tubes. They were microfins, twisted tapes, and high fins. Measurements at different mass fluxes were obtained at six refrigerant mass fractions from 100 percent R-22 up to a 50 percent/50 percent mixture of R-22/R-142b. All condensation measurements were conducted at an isobaric inlet pressure of 2.43 MPa. This pressure corresponds to a saturation temperature of 60°C for R-22. The measurements were taken in 9.53 mm outer diameter smooth tubes and microfin tubes with lengths of 1603 mm. The heat transfer coefficients were determined with the Log Mean Temperature Difference equations. It was found that microfins were more suitable as an enhancement method than twisted tubes or high fins. Also, that the heat transfer coefficients and pressure drops decrease as the mass fraction of R-142b increases.

Condensation Heat Transfer and Pressure Drop of R134A in Horizontal Micro-Scale Enhanced Tube

2020 ◽  
Author(s):  
Zongbao Gu ◽  
Xiang Ma ◽  
Yan He ◽  
Lianxiang Ma ◽  
David J. Kukulka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Evaluation Criteria ◽  
Smooth Tube ◽  
Vapor Quality ◽  
Micro Scale ◽  
Friction Pressure ◽  
Friction Pressure Drop ◽  
Enhanced Surface

Abstract This study was performed to investigate the heat transfer and pressure drop of R134A during condensation inside a stainless steel micro-scale enhanced surface tube (EHT tube) and smooth tube. The tests were conducted at a saturation temperature of 45°C, over the mass fluxes range of 100 to 200 kg/m2s, the heat fluxes of 14–25 kW/m2, an inlet vapor quality of 0.8 and outlet vapor quality of 0.2. The heat length and inner diameter of the tested tube were 2 m and 11.5 mm. The micro-scale enhanced surface tube has complex surface structures composed of dimples and petal arrays background patterns. It can be observed the condensation heat transfer coefficients of the EHT tube is about 1.6–1.7 times higher than that of a stainless steel smooth tube. Enhancement of the EHT tube was achieved due to disruption of the boundary layer, secondary fluid generation, increasing fluid turbulence and heat transfer area. In addition, considering the friction pressure drop, the EHT tube produces the larger friction pressure drop, which is 1.05–1.20 times as compared to the smooth tube. Finally, the performance factors were performed to evaluate the enhancement effect of the EHT tube based on heat transfer coefficient-pressure drop evaluation criteria value (η1) and heat transfer coefficient-area evaluation criteria value (η2).

The Characteristics of Flow Boiling Heat Transfer and Pressure Drop in Small Tube with the Pipe Sections Having Increased Diameters

2013 ◽  
Vol 651 ◽  
pp. 525-529
Author(s):  
Mao Yu Wen ◽  
Kang Jang Jang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Small Diameter ◽  
Saturation Temperature ◽  
Smooth Tube ◽  
Flow Boiling Heat Transfer ◽  
Small Tube

This study presents an experimental investigation of the characteristics of the flow boiling heat transfer and pressure drop for refrigerant of R134a flowing in a small - diameter evaporative tube with the pipe sections having increased diameters. The experiments were performed at the saturation temperature of 5°C , heat flux of 5.12 ~ 10.96 ( KW/m2), mass flux of 200~600 ( kg/m2s), different length-to-diameter ratios of the test tubes and refrigerant quality of 0.07~0.78, and based on the same surface area of heat transfer. The enhancement performance ratios, θa/s for the tubes with the pipe sections having increased diameters relative to the smooth tube are higher than 1 (about 1.01~1.10). It means that the augmented tubes show the better overall performance than the smooth tube under study.

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