Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지
DOI QR코드

DOI QR Code

Effects of Prandtl Numbers on Heat Transfer of Backward-Facing Step Laminar Flow with a Pulsating Inlet

입구유동 가진이 있는 층류 후향계단 유동에서 열전달에 대한 프란틀수 효과해석

  • Kim, Won-Hyun (School of Mechanical Engineering, Kyungpook Nat'l Univ.) ;
  • Park, Tae-Seon (School of Mechanical Engineering, Kyungpook Nat'l Univ.)
  • 김원현 (경북대학교 기계공학부) ;
  • 박태선 (경북대학교 기계공학부)
  • Received : 2012.03.08
  • Accepted : 2012.06.30
  • Published : 2012.09.01
Download PDF
⟨ Previous Next ⟩

Abstract

The wall heat transfer of backward-facing step laminar flows with different Prandtl numbers and a pulsating inlet is investigated by unsteady simulations. The inlet is perturbed by the variation of frequency and amplitude. Temperature-dependent transport properties are adopted. Various characteristics of the wall heat transfer are explained by the variation of the thermal boundary layer. For Pr < 1, the wall heat transfer of temperature-dependent properties is decreased compared to that of constant properties, whereas it increases for Pr < 1. In addition, the wall heat transfer increases depending on the pulsating amplitude. However, the results of frequency variation for St < 0.2 show that the heat transfer is strongly enhanced at a specific frequency. In particular, the increase in the wall heat transfer is strongly related to the root mean square of the fluctuations of the reattachment length.

입구유동 가진이 있는 층류 후향계단 유동에서 Pr수의 변화에 따른 열전달 특성변화를 조사하기 위하여 비정상 수치해석을 수행하였다. 입구는 가진주파수와 가진진폭의 변화에 따른 교란이 주어졌고, 온도함수의 물성치가 적용되었다. 열전달 변화에 대한 다양한 특징들이 열경계층 변화에 의해서 설명되었다. 물성치가 일정한 경우와 비교하였을 때, 물성치가 온도의 함수성이 있는 경우 Pr < 1인 조건에서 열전달은 감소하였고, 반대로 Pr > 1인 조건에서 열전달은 증가하였다. 또한 가진진폭이 증가함에 따라 계단 후류 바닥면에서 열전달도 증가하였다. 그렇지만 가진주파수 변화의 경우 St < 0.2인 조건에서 열전달이 크게 증가하는 특정주파수 영역이 존재하였다. 특히, 열전달의 증가는 재부착 길이의 rms값의 변동정도와 밀접한 관련이 있음을 보여주었다.

Keywords

References

  1. Inaoka, K., Nakamura, K. and Senda, M., 2004, "Heat Transfer Control of a Backward-Facing Step Flow in a Duct by Means of Miniature Electromagnetic Actuators," International Journal of Heat and Fluid Flow, Vol 25, No 5, pp. 711-720. https://doi.org/10.1016/j.ijheatfluidflow.2004.05.006
  2. Chen, X. B., Yu, P., Winoto, S. H. and Low, H. T., 2008, "Forced Convection Over a Backward- Facing Step with a Porous Floor Segment," Numerical Heat Transfer Part A, Vol 53, No 11, pp. 1211-1230. https://doi.org/10.1080/10407780701852852
  3. Park, H. M., Jeon, W. P., Choi H. C. and Yoo, J. Y., 2007, "Mixing Enhancement Behind a Backward-Facing Step Using Tabs," Physics of Fluids, Vol 19, No 10, pp. 105103-105103-12. https://doi.org/10.1063/1.2781597
  4. Rhee, G. H. and Sung, H. J., 2000, "Numerical Prediction of Locally Forced Turbulent Separated and Reattaching Flow," Fluid Dynamics Research, Vol 26, No 6, pp. 421-436. https://doi.org/10.1016/S0169-5983(99)00035-0
  5. Valencia, A. and Hinojosa, L., 1997, "Numerical Solutions of Pulsating Flow and Heat Transfer Characteristics in a Channel with a Backward- Facing Step," Heat and Mass Transfer, Vol 32, No 3, pp. 143-148. https://doi.org/10.1007/s002310050104
  6. Khanafer, K., Azmi, B. A., Shammari, A. A. and Pop, I., 2008, "Mixed Convection Analysis of Laminar Pulsating Flow and Heat Transfer over a Backward Facing Step," International Journal of Heat and Mass Transfer, Vol 51, No 25-26, pp. 5785-5793. https://doi.org/10.1016/j.ijheatmasstransfer.2008.04.060
  7. Velazquez, A., Arias, J. R. and Mendez, B., 2008, "Laminar Heat Transfer Enhancement Downstream of a Backward Facing Step by Using a Pulsating Flow," International Journal of Heat and Mass Transfer, Vol 51, No 7-8, pp. 2075-2089. https://doi.org/10.1016/j.ijheatmasstransfer.2007.06.009
  8. Yu, J. C., Li, Z. X. and Zhao, T. S., 2004 "An Analytical Study of Pulsating Laminar Heat Convection in a Circular Tube with Constant Heat Flux," International Journal of Heat and Mass Transfer, Vol 47, No 24, pp. 5297-5301. https://doi.org/10.1016/j.ijheatmasstransfer.2004.06.029
  9. Hemida, H. N., Sabry, M. N., Abdel-Rahim, A. and Mansour, H., 2002, "Theoretical Analysis of Heat Transfer in Laminar Pulsating Flow," International Journal of Heat and Mass Transfer, Vol 45, No 8, pp. 1767-1780. https://doi.org/10.1016/S0017-9310(01)00274-5
  10. Park, T. S., 2006, "Effects of Time-Integration Method in a Large-Eddy Simulation Using the PISO Algorithm: Part I-Flow Field," Numerical Heat Transfer Part A, Vol 50, No 3, pp. 229-245. https://doi.org/10.1080/10407780600602374
  11. Issa, R. I., 1985, "Solution of the Implicitly Discretised Fluid Flow Equations by Operator- Splitting," Journal of Computational Physics, Vol 62, No 1, pp. 40-65.
  12. Zografos, A. I., Martin, W. A. and Sunderland, J. E., 1987, "Equations of Properties as a Function of Temperature for Seven Fluids," Computer Methods in Applied Mechanics and Engineering, Vol 61, No 2, pp. 177-187. https://doi.org/10.1016/0045-7825(87)90003-X
  13. Khan, M. H., 2004, "Modeling, Simulation and Optimization of Ground Source Heat Pump Systems," Ph. D. Dissertation, Oklahoma State University.
  14. Armaly, B. F., Durst, F., Pereira, J. C. F. and Schonung, B., 1983, "Experimental and Theoretical Investigation of Backward-Facing Step Flow," Journal of Fluid Mechanics, Vol 127, pp. 473-496. https://doi.org/10.1017/S0022112083002839
  15. Sparrow, E. M., Kang, S. S. and Chuck, W., 1987, "Relation Between the Points of Flow Reattachment and Maximum Heat Transfer for Regions of Flow Separation," International Journal of Heat and Mass Transfer, Vol 30, No 7, pp. 1237-1246. https://doi.org/10.1016/0017-9310(87)90157-8