ABSTRACT Numerical investigation of the unsteady two-dimensional slot jet impingement cooling of a horizontal heat source is carried out in the present article. The jet velocity is assumed to be in the laminar flow regime and it has a periodic variation with the flow time. The solution is started with zero initial velocity components and constant initial temperature, which is same as the jet temperature. After few periods of oscillation the flow and heat transfer process become periodic. The performance of the jet impingement cooling is evaluated by calculation of friction coefficient and Nusselt number. Parametric study is carried out and the results are presented to show the effects of the periodic jet velocity on the heat and fluid flow. The results indicate that the average Nusselt number and the average friction coefficient are oscillating following the jet velocity oscillation with a small phase shift at small periods. The simulation results show that the combination of Re =200 with the period of the jet velocity between 1.5 sec and 2.0 sec and high amplitude (0.25 m/s to 0.3 m/s) gives average friction coefficient and Nusselt number higher than the respective steady-state values.
Cite this paper
nullN. SAEID, "Effect of Oscillating Jet Velocity on the Jet Impingement Cooling of an Isothermal Surface," Engineering, Vol. 1 No. 3, 2009, pp. 133-139. doi: 10.4236/eng.2009.13016.
 E. M. Sparrow and T. C. Wong, “Impingement transfer coefficient due to initially laminar slot jets,” Int. J. Heat Mass Transfer, Vol. 18, pp. 597–605, 1975.
S. Al-Sanea, “A numerical study of the flow and heat transfer characteristics of an impinging laminar slot-jet including crossflow effects,” Int. J. Heat Mass Transfer, Vol. 35, pp. 2501–2513, 1992.
Z. H. Lin, Y. J. Chou, and Y. H. Hung, “Heat transfer behaviors of a confined slot jet impingement,” Int. J. Heat Mass Transfer, Vol. 40, pp. 1095–1107, 1997.
M. A. Rady, “Buoyancy effects on the flow and heat transfer characteristics of an impinging semi-confined laminar slot jet,” Int. J. Trans. Phenomena, Vol. 2, pp. 113–126, 2000.
H. Chattopadhyay and S. K. Saha, “Simulation of laminar slot jets impinging on a moving surface,” J. Heat Transfer, Vol. 124, pp. 1049-1055, 2002.
L. B. Y. Aldabbagh, I. Sezai, and A. A. Mohamad, “Three- dimensional investigation of a laminar impinging square jet interaction with cross flow,” J. Heat Transfer, Vol. 125, pp. 243–249, 2003.
D. Sahoo and M. A. R. Sharif, “Numerical modeling of slot-jet impingement cooling of a constant heat flux surface confined by a parallel wall,” Int. J. Therm. Sci., Vol. 43, pp. 877–887, 2004.
X. Li, J. L. Gaddis, and T. Wang, “Multiple flow patterns and heat transfer in confined jet impingement,” Int. J. Heat Fluid Flow, Vol. 26, pp. 746–754, 2005.
V. A. Chiriac and A. Ortega, “A numerical study of the unsteady flow and heat transfer in a transitional confined slot jet impinging on an isothermal surface,” Int. J. Heat Mass Transfer, Vol. 45, pp. 1237–1248, 2002.
Y. M. Chung, K. H. Lao, and N. D. Sandham, “Numerical study of momentum and heat transfer in unsteady impinging jets,” Int. J. Heat Fluid Flow, Vol. 23, pp. 592–600, 2002.
C. Camci and F. Herr, “Forced convection heat transfer enhancement using a self-oscillating impinging planar jet,” J. Heat Transfer, Vol. 124, pp. 770–782, 2002.
H. J. Poh, K. Kumar, and A. S. Mujumdar, “Heat transfer from a pulsed laminar impinging jet,” Int. Comm. Heat Mass Transfer, Vol. 32, pp. 1317–1324, 2005.
T. Hayase, J. A. C. Humphrey, and R. Greif, “A consistently formulated QUICK scheme for fast and stable convergence using finite-volume iterative calculation procedures,” J. Comput. Phys., Vol. 98, pp. 108–118, 1992.
H. K. Versteeg and W. Malalasekera, “Computational fluid dynamics: An introduction,” Longman, 1995.
N. H. Saeid, “Periodic free convection from vertical plate subjected to periodic surface temperature oscillation,” Int. J. Therm. Sci., Vol. 43, pp. 569–574, 2004.
N. H. Saeid, “Mixed convection flow along a vertical plate subjected to time-periodic surface temperature oscillations,” Int. J. Therm. Sci., Vol. 44, pp. 531–539, 2005.