An experimental study on flow patterns and heat transfer characteristics during cryogenic chilldown in a vertical pipe |
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| Authors: | Hong Hu Jacob N Chung Samuel H Amber |
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| Affiliation: | 1. Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida 32611, United States;2. Department of Physics and Nuclear Engineering, U.S. Military Academy, West point, New York 10928, United States;1. NASA Kennedy Space Center, M/S: NE-F6 Kennedy Space Center, FL, USA, 32899;2. NASA Marshall Space Flight Center, M/S:ER-24 Huntsville, AL, USA, 35812;1. Mary Kay O''Connor Process Safety Center, College Station, TX, USA;2. Mary Kay O''Connor Process Safety Center Extension, Texas A&M University at Qatar, Doha, Qatar;1. SGT, Inc., Greenbelt, MD 20770, USA;2. Ames Research Center, Moffett Field, CA 94035, USA;3. Kennedy Space Center, FL 32899, USA;1. Cryogenics Heat Transfer Laboratory, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611-6300, USA;2. NASA Glenn Research Center, Cleveland, OH 44135, USA;1. State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China;2. Kunming Institute of Physics, Kunming 650223, PR China;1. Graduate School of Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Japan;2. Japan Aerospace Exploration Agency, Chohu 182-8522, Japan;1. Cryogenics Heat Transfer Laboratory, Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611-6300, USA;2. Nanostructured Interfaces Laboratory, Department of Chemical Engineering, University of Florida, Gainesville, FL 32611-6005, USA |
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| Abstract: | In the present paper, the experimental results of a cryogenic chilldown process are reported. The physical phenomena involve unsteady two-phase vapor–liquid flow and intense boiling heat transfer of the cryogenic fluid that is coupled with the transient heat conduction inside pipe walls. The objective for the present study is to compare the chilldown rates and flow patterns between the upward flow and downward flow in a vertical pipe. Liquid nitrogen is employed as the working fluid and the test section is a vertical straight segment of a Pyrex glass pipe with an inner diameter of 8 mm. The effects of mass flow rate on the flow patterns, heat transfer characteristics and interface movement were determined through experiments performed under several different mass flow rates. Through flow visualization, measurement and analysis on the flow patterns and temperature variations, a physical explanation of the vertical chilldown is given. By observing the process and analyzing the results, it is concluded that pipe chilldown in a vertical flow is similar to that in microgravity to some extent. |
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