Impingement Cooling

Dr. Phil Ligrani:    p_ligrani@msn.com

  • Applicable to internal cooling of turbine airfoils for gas turbine engines
  • Independent effects of Mach number and Reynolds number
  • Effects of relative values of surface temperature, impingement temperature, cross-flow temperature
  • Surface heat transfer coefficients and surface impingement effectiveness

Impinging gas jets are commonly used to cool aircraft turbines and the electrical apparatus and to dry lightweight paper such as tissue and toweling. These applications need relatively high rates of heat transfer because of high speed operation and production, and the limited time and surface areas. Impingement with high velocity gas jets is a solution to produce high heat transfer. Surface heat transfer coefficients generated by impingement of air jets are generally higher in magnitude than many other conventional techniques. The figure above shows one test section used in the Convective Heat Transfer Laboratory at the University of Utah to investigate heat transfer and surface effectiveness distributions from impinging air jets.

The heat transfer coefficient distributions produced by arrays of impingement jets depend upon many parameters. These include the Reynolds number of the jet holes (Rej), the crossflow velocity of the spent air to air jet velocity ratio (Gc/Gj), the streamwise hole spacing (Xn), the spanwise hole spacing (Yn), the distance between the impingement plate and the target plate (Z), and jet hole diameter (d). Some researchers have also investigated the effects of both flat and concave target surfaces for a single jet, for lines of jets, and for array of jets. Kercher and Tabakoff (1970), Florschuetz et al. (1981), and Bailey and Bunker (2002) give correlations which provide information on the effects of Reynolds number, geometry, and crossflow.

Experimental data are needed to provide information on the influences of Mach number and Reynolds number (independently) on surface heat transfer coefficient distributions produced by arrays of jets impinging on a target surface. As Mach numbers with the modern turbojet, turbo-fan, and gas turbine turbines becomes higher, estimation of Mach number effect on the impingement heat transfer coefficient becomes more important. One goal of the efforts underway in the Convective Heat Transfer Laboratory at the University of Utah is to obtain new data on the separate effects of Reynolds number and Mach number on surface heat transfer coefficient distributions. A second goal is to provide data on the influences of surface temperature, impingement temperature, and cross-flow temperature and to extend the range of applicability of existing current correlations.

Impingement Cooling REFERENCES
1. Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer, (M. Goodro, J. Park, P. M. Ligrani, M. Fox, and H.-K. Moon), International Journal of Heat and Mass Transfer, Vol. 50, No. 1, pp. 367-380, January 2007.

2. Separate Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer (J. Park, M. Goodro, P. M. Ligrani, M. Fox, and H.-K. Moon), ASME Transactions-Journal of Turbomachinery, Vol. 129, No. 2, pp. 269-280, April 2007.

3. Effect of Hole Spacing on Spatially-Resolved Jet Array Impingement Heat Transfer (M. Goodro, J. Park, P. M. Ligrani, M. Fox, and H.-K. Moon), International Journal of Heat and Mass Transfer, Vol. 51, Nos. 25-26, pp. 6243-6253, December 2008.

4. Effect of Temperature Ratio on Jet Array Impingement Heat Transfer (M. Goodro, J. Park, P. M. Ligrani, M. Fox, and H.-K. Moon), ASME Transactions-Journal of Heat Transfer, Vo. 131, No. 1, Pages 012201-1 to 12201-10, January 2009.

5. Mach Number, Reynolds Number, Jet Spacing Variations: Full Array of Impinging Jets (M. Goodro, P. M. Ligrani, M. Fox, and H.-K. Moon), AIAA Journal of Thermophysics and Heat Transfer, Vol. 24, No. 1, pp. 133-144, January – March 2010.

6. Influence of Surface Roughness On the Aerodynamic Losses of a Turbine Vane (Q. Zhang, M. Goodro, P. M. Ligrani, R. Trindade, S. Sreekanth), Paper Number GT2005-68832, 50th ASME TURBO EXPO Gas Turbine and Aeroengine Technical Congress, Exposition, and Users Symposium, Reno, Nevada, June 6-9, 2005.

7. Separate Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer (J. Park, M. Goodro, P. M. Ligrani, M. Fox, and H.-K. Moon), Paper Number GT2006-90628, 51st ASME TURBO EXPO Gas Turbine and Aeroengine Technical Congress, Exposition, and Users Symposium, Barcelona, Spain May 8-11, 2006.

8. Effect of Temperature Ratio on Jet Array Impingement Heat Transfer (M. Goodro, J. Park, P. M. Ligrani, M. Fox, and H.-K. Moon), Paper Number GT2007-28293, 52nd ASME TURBO EXPO Gas Turbine and Aeroengine Technical Congress, Exposition, and Users Symposium, Montreal, Canada, May 14-17, 2007.

9. Effect of Hole Spacing on Jet Array Impingement Heat Transfer (M. Goodro, J. Park, P. M. Ligrani, M. Fox, and H.-K. Moon), Paper Number GT2007-28292, 52nd ASME TURBO EXPO Gas Turbine and Aeroengine Technical Congress, Exposition, and Users Symposium, Montreal, Canada, May 14-17, 2007.

10. Effects of Mach Number, Reynolds Number, and Jet Spacing on Surface Heat Transfer for a Full Array of Impinging Jets (M. Goodro, P. M. Ligrani, M. Fox, H.-K. Moon), TURBINE09 – International Symposium on Heat Transfer in Gas Turbine Systems, Antalya, Turkey, August 9-14, 2009.

11. Effects of Jet-To-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer (J. Lee, Z. Ren, J. Haegele, G. Potts, J. S. Jin, P. M. Ligrani, M. Fox, and H.-K. Moon), ASME Transactions-Journal of Turbomachinery, accepted for publication, 2013, to appear, 2014.

12. Effects of Jet-To-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer (J. Lee, Z. Ren, J. Haegele, G. Potts, J. S. Jin, P. M. Ligrani, M. Fox, and H.-K. Moon), Paper Number GT2013-94651, TURBO EXPO 2013 – 58th TURBO EXPO Turbine Technical Conference and Exposition, San Antonio, Texas, USA, June 3-7, 2013.

Copyright Trademarks Ligrani Research Group 2009