Study on Flow and Heat Transfer Characteristics of Vapor–Liquid Two-Phase Flow in a Narrow Rectangular Channel With Longitudinal Vortex Generators

Abstract

The heat transfer enhancement of the longitudinal vortex (LV) is a kind of technology with high efficiency and low thermal resistance. An LV is produced by longitudinal vortex generators (LVGs). Due to their relative long influence distance and simple structure, the LVGs may be used in narrow channels with a flat surface. In this paper, the dimension of a narrow rectangular channel is 600 mm (length) × 40 mm (width) × 3 mm (height), and one LVG is 14 mm (length) ×2.2 mm (width) × 1.8 mm (height). The rectangular blocked LVGs are periodically laid out in the heated plate, and the attack angle of LVGs is 44°, the longitudinal pitch between LVGs is 100 mm, and the transverse pitch between LVGs is 4 mm. The test section is visual with three surfaces and heated with one surface by direct current. The working fluid is water. The experimental results show that the boiling heat transfer coefficient on the heated surface is increased by 25.8%, while the pressure drop along the test section is increased by 50.6%. At the same time, the visual experimental data shows that the bubbles’ behavior has been intensively affected by LVs, the growth and gathering of bubbles have been depressed, and the thermal boundary layer in the test section has been greatly damaged and reduced; as results, the momentum and energy exchange in the test section have been strengthened. Thus, the heat transfer is obviously enhanced by LVs.

Acknowledgments

This work is supported by the National Natural Science Foundation of China (50576089) and National Key Laboratory of Bubble Physics and Natural Circulation (9140C7101030602).

Yanping Huang received his master's and Ph.D. degrees from the Reactor Engineering Department of Xi’an Jiaotong University of China in June 1994 and December 2003, respectively. He has worked in the Nuclear Power Institute of China since 1994. His research interests are in thermohydraulic experimental and theoretical work, and safety technology development for nuclear reactor engineering.

Jun Huang is a research engineer at the Nuclear Power Institute of China. He received his Ph.D. in engineering thermophysics in 2009 from Xi’an Jiaotong University, Xi’an, China. His Ph.D. thesis was in heat transfer enhancement with longitudinal vortex generators. He is currently working on thermohydraulics of reactors.

Jian Ma is a Ph.D. student in the School of Power Engineering at ChongQing University. He did experimental and numerical simulations on the thermohydraulics of reactors. His master's thesis was on heat transfer enhancement with longitudinal vortex, and he received his M.S. in 2008. His doctoral research is focused on the large eddy simulation of thermohydraulics under water.

Qiuwang Wang is a professor at the School of Energy and Power Engineering, Xi’an Jiaotong University. He received his Ph.D degree in engineering thermophysics from Xi’an Jiaotong University in 1996. He then joined the faculty of the university and took the professor post in 2001. His main research interests include computational fluid dynamics and numerical heat transfer, heat transfer enhancement, compact heat exchangers, building energy saving, and indoor air quality. He has published more than 100 journal papers, half of which are for international journals and one US patent. He has also been authorized for 14 invention patents of China.