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 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.

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

2015 ◽  
Author(s):  
Jian-jun Sun ◽  
Jing-xiang Chen ◽  
David J. Kukulka ◽  
Kan Zhou ◽  
Wei Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Smooth Tube ◽  
External Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
Enhanced Surface

An experiment investigation was performed using R410A in order to determine the single-phase and evaporation heat transfer coefficients on the outside of (i) a smooth tube; (ii) herringbone tube; and (iii) the newly developed Vipertex enhanced surface 1EHT tube; all with the same external diameter (12.7 mm). The nominal evaporation temperature is 279 K, with inlet and outlet qualities of 0.1 and 0.8. Mass fluxes ranged from 10 to 40 kg m−2s−1. Results suggest that the 1EHT tube has excellent heat transfer performance but a higher pressure drop when compared to a smooth tube. Evaporation heat transfer coefficient for the 1EHT is lower than the herringbone tube and the pressure drop is almost the same.

Prediction of Heat Transfer Coefficients in Gas Flow Normal to Finned and Smooth Tube Banks

1981 ◽  
Vol 103 (4) ◽  
pp. 705-714 ◽  
Author(s):  
J. C. Biery
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Finned Tube ◽  
Smooth Tube ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Tube Banks

A new method is presented to predict heat transfer coefficients for gas flow normal to smooth and finned tube tanks with triangular pitch. A transformation from the actual tube bank to an equivalent equilateral triangular pitch infinite smooth tube bank (ETP-I-STB) is made. A function of Ch(Ch = NSTNPR2/3NRe0.4) versus (Xt D0)Δ, ratio of transverse pitch to tube diameter for the ETP-I-STB, was developed. The Ch for the equivalent ETP-I-STP then applies to the actual tube bank. The method works with circular finned tubes, smooth tubes, continuous finned tubes, and segmented finned tubes with any triangular pitch. Also, fair predictions were made for in-line tubes with high Reynolds numbers.

Flow Boiling of Water in Minichannels: Effect of Pressure

2007 ◽  
Author(s):  
Kwang-Hyun Bang ◽  
Kun-Eui Hong ◽  
In-Seon Hwang
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Gear Pump ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Effect Of Pressure ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer

This paper reports an experimental study on flow boiling of water in a minichannel. Flow boiling heat transfer coefficients and pressure drops were measured and the data were compared with existing correlations. The effect of pressure was the major objectives in this study and the range of pressure was 1 to 18 bars. The experimental apparatus consisted mainly of a minichannel test section, gear pump, pre-heater, pressurizer, condenser and evaporator. The evaporator was used for variation of vapor quality at the inlet of test section. The pressurizer controls the desired system pressure. The test section is a round tube of 1.73 mm inside diameter, made of 316 stainless steel. The test section and the evaporator tubes were heated by DC electric current through the tubes. The measured flow boiling heat transfer coefficients showed two distinct regions; relatively high heat transfer coefficients at low vapor quality and lower heat transfer coefficients at higher vapor quality. This observation implies the change of flow regime, slug to annular flow. Comparisons of the experimental data and the prediction of correlations (Gungor & Winterton, 1987; Tran et al., 1996; Kandlikar, 2003) showed large discrepancy in both regions.

Experimental Study on Flow Boiling Heat Transfer in an Extremely Small Tube

2006 ◽  
Author(s):  
Haruhiko Ohta ◽  
Koichi Inoue ◽  
Yuichiro Shimada
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Flow Boiling ◽  
Vapor Quality ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Flow Boiling Heat Transfer ◽  
Small Tube

Flow boiling heat transfer in a single small tube is investigated by using FC72 as a working fluid. The heat transfer coefficients are measured in the ranges of heat flux 2–24kW/m2 and mass velocity 100–400kg/m2s under the condition of near atmospheric pressure. Test tube, made of stainless steel, has an inner diameter of 0.51mm and a heated length of 200mm. The tube is located horizontally in a vacuum chamber to reduce the heat loss and to minimize the time to obtain data regarded as that of steady state. In the single-phase region, heat transfer coefficients due to forced convection are in good agreement with the values from the conventional theories. In the saturated region, measured heat transfer characteristics are quite different depending on whether the test liquid is deaerated or not deaerated before the experiments. By using deaerated liquid, three different heat transfer regimes are observed: In the first regime, the heat transfer is dominated by nucleate boiling in low vapor quality, and the heat transfer is deteriorated or enhanced depending on the channel confinement and heat flux. In the second regime, the heat transfer is dominated by two-phase forced convection in moderate quality as is well known for the tubes of normal size. In the third regime, the heat transfer is dominated again by two-phase forced convection, but is deteriorated in high quality. One or two regimes can disappear or become unclear depending on the conditions of flow and heating. The effects of vapor quality and mass velocity on the heat transfer characteristics due to two-phase forced convection in the moderate vapor quality are clarified in the experimental ranges tested. And a reason for the gradual heat transfer deterioration observed in high quality is discussed based on the liquid-vapor behaviors inherent in small diameter tubes.

Experimental Study on Characteristics of Condensation and Flow Resistance Inside Horizontal Corrugated Low Finned Tubes

2018 ◽  
Author(s):  
Bin Ren ◽  
Xiaoying Tang ◽  
Hongliang Lu ◽  
Dongliang Fu ◽  
Yannan Du ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Flow Resistance ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Finned Tubes ◽  
Heat Transfer Coefficients ◽  
Inlet Conditions

It is the simplest and most feasible method to enhance heat transfer by replacing the smooth tube with various kinds of special-shaped enhanced tubes. In this paper, the characteristics of condensation and flow resistance inside horizontal corrugated low finned tubes were studied experimentally. The effects of steam inlet conditions and condensation tubes structural parameters were analyzed. The results showed that the heat transfer performance inside corrugated low finned tubes was greater than that inside smooth tubes. Like inside smooth tubes, the heat transfer coefficients increased with the vapor quality and steam mass flux. But the enhancement rate showed the opposite trend. And the heat transfer coefficients inside corrugated low finned tubes increased with the decrease of pitch and increase of protrusion height. Meanwhile, the variation trend of pressure drop gradient changing with inlet conditions and construal parameters was consistent with trend of heat transfer coefficient. The performance evaluation criteria were used to evaluate the comprehensive performance. It was found that the maximum performance evaluation factor was acquired at the minimum vapor quality and mass flux. The maximum value was 2.24 happened in the tube with pitch of 6 mm and height of 0.7mm. Finally, both the correlation for heat transfer coefficient and correlation for pressure drop gradient were developed by fitting experimental data. And this would provide calculation foundations for the design of horizontal condensers with corrugated low finned tubes.

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