An experimental investigation of two-phase crossflow over rigidly and flexibly mounted tubes

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/31686· OSTI ID:31686

Gerhart, Susan Marie ^[1]

---

1. Univ. of California, Los Angeles, CA (United States)

Two-phase crossflow over heat exchanger tubes induces vibrations which contribute greatly to the wear on the tubes. Of the three mechanisms leading to two-phase flow-induced vibrations which have been identified, fluid-elastic instability has been recognized as that which leads to the vibrations with the largest amplitude. The mass damping parameter is used to predict the onset of fluid-elastic instability, and the mean drag coefficient is used to calculate the mass damping parameter. In this thesis, the drag coefficient measured over single tubes and tubes within array, in single-phase and two-phase flow at various Reynolds numbers, is discussed. The drag coefficient was measured by two methods. For flexibly mounted tubes, strain gages were mounted on cantilever beams which held the tube in place and allowed it to vibrate in the direction parallel to the flow only. For both rigidly and flexibly mounted tubes, pressure distributions were measured around the perimeter of the tube. Forces, and then the drag coefficient, could be calculated from this information. The drag coefficient was not found to depend upon the flexibility of the tube mounting. As the void fraction of the flow increases, the drag coefficient over the tube increases. This effect was found to be quite large at low Reynolds numbers, and weaker at higher Reynolds numbers, and a different effect was found at very high Reynolds numbers.

• Research Organization: California Univ., Los Angeles, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: FG02-89ER12902
• OSTI ID: 31686
• Report Number(s): DOE/ER/12902--T2; ON: DE95006084
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
TUBES
TWO-PHASE FLOW