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

2021 ◽  
Author(s):  
Zhang Jianghui ◽  
Yu Guo ◽  
Jiacheng Wang ◽  
Chuancai Zhang ◽  
Yan He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Evaporation Heat ◽  
Enhanced Tubes ◽  
Evaporation Heat Transfer

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.

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.

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.

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