An Investigation of Heat Transfer Characteristics of Swirling Flow in a 180$^{\circ}$ Circular Section Bend with Uniform Heat Flux

  • Chang, Tae-Hyun (Division of Mechanical and Automation Engineering, Kyungnam University)
  • Published : 2003.10.01

Abstract

An experiment was performed to obtain the local heat transfer coefficient and Nusselt number in a circular duct with a 180$^{\circ}$ bend for Re=6 x 10$^4$, 8 x 10$^4$ and 1 x 10$\^$5/ under swirling flow and non-swirling flow conditions. The test tube with a circular section was made from stainless steel having a curvature ration of 9.4. Current heat flux of 5.11 kW/㎡ was applied to the test tube by electrical power and the swirling motion of air was produced by a tangential inlet to the pipe axis at 180$^{\circ}$. Measurements of local wall temperatures and the bulk mean temperatures of air were made at four circumferential positions at 16 stations. The wall temperatures showed a reduced distribution curve at the bend for the non-swirling flow, but this effect did not appear for the swirling flow. The Nusselt number distributions for the swirling flow, which was calculated from the measured wall and the bulk temperatures, were higher than that of the non-swirling flow. The average Nusselt number of the swirling flow increased by about 90-100%, compared to that of the non-swirling flow. The Nu/Nu$\_$DB/ values at the 90$^{\circ}$ station for non-swirling flow and swirling flow were approximately 2.5 and 4.8 at Re=6x10$^4$ respectively. The values agree well with Said's results for non-swirling flow.

Keywords

References

  1. Baughm, J. W., Lacovides, H., Jackson, D. C. and Launder, B. E., 1987, 'Local Heat Transfer Measurements in Turbulent Flow Around a 180-Deg Pipe Bend,' Journal of Heat Transfer, Vol. 109, pp. 43-48
  2. Chang, S. M., Humphrey, J. A. and Modavi, A., 1988, 'Turbulent Flow in Strongly Curved U-bend and Downstream Tangent of Square Cross Section,' PCH Physico Chemical Hydrodynamic, Vol. 4, pp.243-253
  3. Enayet, M. M., Gibson, M. M., Taylor, A. M., K. P. and Yiannekis, M., 1982, 'Laser-Doppler Measurements of Laminar and Turbulent Flow in a Pipe Bend,' Int. J. Heat & Fluid Flow, Vol. 3, No. 4, pp. 213-220 https://doi.org/10.1016/0142-727X(82)90024-8
  4. Ito, H., 1960, 'Pressure Losses in Smooth Pipe Bends,' Journal of Basic Engineering, pp. 131-139
  5. Kays, W. M. and Crawford, M. E., 1980, Convective Heat Transfer, Second Edition, McGraw Hill
  6. Medwell, J. O.,Chang, T. H. and Kwon, S. S., 1989, 'A Study of Swirling Flow in a Cylindrical Tube,' Korean J. of Air-Conditioning and Refrigeration Engineering, Vol. 1, No. 4, pp. 265-275
  7. Metha, N. D. and Bell, K. J., 1981, 'Laminar Flow Heat Transfer,' Soviet Research, Vol. 103, No. 6, pp. 71-80
  8. Mullin, T. and Greated, C. A., 1980, 'Oscillatory Flow in a Curved Pipe, Part 1 :The Developing Flow Case,' J. Fluid Mech., Vol. 98, pp. 383-395 https://doi.org/10.1017/S0022112080000201
  9. Richard W. Johnson, 1988, 'Numerical Simulation of Local Nusselts Number for Turbulent Flow in a Square Duct with a 180 Degree Bend,' Numerical Heat Transfer, Vol. 13, pp. 205-228 https://doi.org/10.1080/10407788808913612
  10. Said Dini, Nader Saniei and Daniel Bartlett, 1992, 'Use of Liquid Crystal for Local Heat Transfer Coefficient Measurement Around a 180 Degree Bend,' ASME, HTD, Vol. 210, pp. 107-114
  11. Tae Hyun Chang and Hee Young Kim, 2001, 'A Investigation of Swirling Flow in a Cylindrical Tube,' KSME Internationnal Journal, Vol. 15, No. 12, pp. 1892-1899
  12. Talbot, L., 1954, 'Laminar Swirl Flow,' J. of Applied Mechanics, ASME, Vol. 21, pp. 1-7
  13. Thomson, J., 1876, 'On the Origin of Winding of River in Alluvial Planic, with Remarks on the Flow of Water Pound Bend in Pipe,' duroc. K. Soc. London Ser, A25, pp. 5-8