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强化传热期刊
影响因子: 0.562 5年影响因子: 0.605 SJR: 0.211 SNIP: 0.361 CiteScore™: 0.33

ISSN 打印: 1065-5131
ISSN 在线: 1026-5511

强化传热期刊

DOI: 10.1615/JEnhHeatTransf.v4.i4.50
pages 297-308

Heat Transfer and Friction Characteristics of Turbulent Flow in Circular Tubes with Twisted-Tape Inserts and Axial Interrupted Ribs

Y. M. Zhang
Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A & M University, College Station, TX 77843-3123
Je-Chin Han
Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A&M University College Sation, TX 77843-3123, USA
Ching-Pang Lee
General Electric Company, Cincinnati, Ohio 45215, U.S.A.

ABSTRACT

Local heat transfer distributions and pressure drop in smooth circular tubes with twisted-tape inserts and axial interrupted ribs were investigated. Experimental data for isothermal friction factors and regionally averaged Nusselt numbers are presented for turbulent air flows for Reynolds numbers ranging from 17,000 to 82,000. The circular tube is composed of ten isolated copper sections with a tube length-to-diameter ratio (L/D) of 15. Three different 360° twisted-tape ratios are studied: H/D = 6(2.5 turns), 7.5 (2 turns), and 10 (1.5 turns). Three axial interrupted rib configurations attached to the inner wall of three test tubes with twisted-tape inserts are investigated: e/D = 0.0625 in-line rib, e/D = 0.0625 staggered rib, and e/D = 0.125 staggered rib.
The results show that the heat transfer and pressure drop in the tube with twisted-tape inserts increase by increasing the number of twisted-tape turns. The tube with twisted-tape inserts provide 1.5−2.0 times the heat transfer augmentation with 3-4 times the pressure drop penalty. The tube with twisted-tape inserts and staggered ribs produce higher heat transfer and pressure drop than that with twisted-tape inserts and in-line ribs, and significantly higher than without ribs. The tube with twisted-tape inserts (H/D = 7.5) and e/D = 0.125 staggered ribs provides 1.8−2.8 times the heat transfer enhancement with about 9−10 times the pressure drop penalty. The tube with twisted-tape inserts (H/D = 6) and with staggered ribs (e/D = 0.125) gains 2.2−3.2 times the heat transfer while paying 13−14 times the pressure drop. The best heat transfer performance in the tube with twisted-tape insert and staggered ribs (e/D = 0.125) is about 25−40% higher than that with the twisted-tape only for different H/D for a constant pumping power.


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