Subcooled Flow Boiling Heat Transfer in Volumetrically Heated Packed Bed

Author(s):  
Xu Guangzhan ◽  
Zhongning Sun ◽  
Xianke Meng ◽  
Xiaoning Zhang ◽  
Jiqiang Su ◽  
...  

The volumetrically heated packed bed has been widely utilized in modern industry, however, due to the variability and randomness of packed bed channels, flow boiling heat transfer characteristics is complex. To study subcooled flow boiling heat transfer characteristics of volumetrically heated packed bed, here electromagnetic induction heating method was used to heat the oxidized carbon steel balls adopted to stack packed bed, while water was utilized as refrigerant in the experiment. The mass flux and heat flux effects on the subcooled flow boiling heat transfer were analyzed. A new correlation was developed to predict the subcooled flow boiling heat transfer coefficient in volumetrically heated packed bed.

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 927 ◽  
Author(s):  
Zhi-Chuan Sun ◽  
Xiang Ma ◽  
Lian-Xiang Ma ◽  
Wei Li ◽  
David Kukulka

An experimental investigation was conducted to explore the flow boiling heat transfer characteristics of refrigerants R134A and R410A inside a smooth tube, as well as inside two newly developed surface-enhanced tubes. The internal surface structures of the two enhanced tubes are comprised of protrusions/dimples and petal-shaped bumps/cavities. The equivalent inner diameter of all tested tubes is 11.5 mm, and the tube length is 2 m. The experimental test conditions included saturation temperatures of 6 °C and 10 °C; mass velocities ranging from 70 to 200 kg/(m2s); and heat fluxes ranging from 10 to 35 kW/m2, with inlet and outlet vapor quality of 0.2 and 0.8. It was observed that the enhanced tubes exhibit excellent flow boiling heat transfer performance. This can be attributed to the complex surface patterns of dimples and petal arrays that increase the active heat transfer area; in addition, more nucleation sites are produced, and there is also an increased interfacial turbulence. Results showed that the boiling heat transfer coefficient of the enhanced surface tubes was 1.15–1.66 times that of the smooth tubing. Also, effects of the flow pattern and saturated temperature are discussed. Finally, a comparison of several existing flow boiling heat transfer models using the data from the current study is presented.


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