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.

scholarly journals Heat transfer performance of R1234yf for convective boiling in horizontal micro-fin and smooth tubes

2020 ◽  
Vol 207 ◽  
pp. 01009
Author(s):  
Thanh Nhan Phan ◽  
Van Hung Tran ◽  
Nikola Kaloyanov ◽  
Momchil Vassilev
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Mass Flux ◽  
Heat Transfer Performance ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Transfer Performance ◽  
Convective Boiling ◽  
Penalty Factor ◽  
Smooth Tubes

This study analyses the performance of heat transfer process which occurs in the convective boiling of Hydro fluoro Olefin (HFO) refrigerant, R1234yf, in horizontal tube. Heat transfer and pressure drop of R1234yf are analyzed and computed at the same working conditions on the same size of outer diameter of tube do = 9.52 mm with difference of inner surface, one is a smooth surface and microfin for other. The flow pattern maps were built at 5°C saturation temperature with 8.62 kW/m2 of heat flux, it is presented that flow pattern of helix flow occurs at very low mass flux and low quality, while at that condition on smooth tube the flow is still stratified wavy flow. The comparison of heat transfer performance between microfin and smooth tube would be evaluated on enhancement factor E, penalty factor P and efficiency index I. With the mass flux on the range G = 111 -- 333 kg/m2s for 5°C boiling temperature, the results show that, average value of E is 2.18; 1.45 of P and 1.54 of I. One more impressing thing is that, at the quality “x” larger than 0.8, the dryout phenomenon takes place on smooth tubes while microfin tubes do not have this phenomenon.

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.

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.

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.

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.

Heat Transfer Performance During Condensation Inside Spiralled Micro-Fin Tubes

2004 ◽  
Vol 126 (3) ◽  
pp. 321-328 ◽  
Author(s):  
Jean-Pierre M. Bukasa ◽  
Leon Liebenberg ◽  
Josua P. Meyer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Geometric Parameters ◽  
Experimental Results ◽  
Outer Diameter ◽  
Transfer Performance ◽  
Fin Tube ◽  
R 134A ◽  
Fin Tubes ◽  
Spiral Angle

The effect of the spiral angle on the heat transfer performance in micro-fin tube condensers has not yet been clearly established because other geometric parameters affecting the heat transfer performance were simultaneously varied in previous studies. This paper reports on the influence of the spiral angle on the heat transfer during condensation inside spiralled micro-fin tubes having all other geometric parameters constant. Tests were conducted for condensation of R-22, R-134a, and R-407C inside a smooth (9.52 mm outer diameter) and three micro-fin tubes with approximately the same diameter, having spiral angles of 10 deg, 18 deg, and 37 deg, respectively. Experimental results indicated a heat transfer augmentation with spiral angle increase. A new semi-empirical predictive correlation was developed for practical design of spiralled micro-fin tubes. The proposed new correlation predicted the majority of experimental results of the present study within a deviation zone of ±20%.

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.

scholarly journals Numerical study on heat transfer and flow resistance characteristics of multi-head twisted spiral tube

2021 ◽  
pp. 206-206
Author(s):  
Zhiqun Zheng ◽  
Fayi Yan ◽  
Lei Shi
Keyword(s):  
Heat Transfer ◽  
Numerical Calculation ◽  
Cross Section ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Smooth Tube ◽  
Transfer Performance ◽  
Spiral Tube ◽  
Inside Diameter ◽  
The Cross

A numerical calculation model of multihead twisted spiral tube (MTST) was established. In the range of Reynolds number from 5000 to 35000, the influence of different twisted structure on the flow and heat transfer characteristics of the MTST was studied by numerical calculation. Numerical calculation results indicate that the Nusselt number and friction coefficient increase with the increase in the ratio of outside and inside diameter of the cross-section, the increase in the number of twisted nodes, and the increase in the number of twisted spiral tube heads. Under the condition of the same spiral structure and the same hydraulic diameter, the heat transfer performance of the MTST is better than that of the spiral smooth tube. In addition, through artificial neural network (ANN) analysis, the ratio of outside and inside diameter of the cross-section, number of twisted nodes, and the number of twisted spiral tube heads were optimized to promote the comprehensive heat transfer performance. The performance evaluation criterion is the highest when the ratio of outside and inside diameter of the cross-section is 25/22.5, the number of twisted nodes is 3, and the number of twisted spiral tube heads is 3, which is 1.849 of the spiral smooth tube.

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