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Research Papers: Heat and Mass Transfer

Optimization Arrangement of Two Pulsating Impingement Slot Jets for Achieving Heat Transfer Coefficient Uniformity

[+] Author and Article Information
S. D. Farahani

School of Mechanical Engineering,
University College of Engineering,
University of Tehran,
Tehran 1417466191, Iran
e-mail: sdfarahani@ut.ac.ir

M. A. Bijarchi

School of Mechanical Engineering,
University College of Engineering,
University of Tehran,
Tehran 1417466191, Iran
e-mail: ali_bijarchi@ut.ac.ir

F. Kowsary

School of Mechanical Engineering,
University College of Engineering,
University of Tehran,
Tehran 1417466191, Iran
e-mail: fkowsari@ut.ac.ir

M. Ashjaee

School of Mechanical Engineering,
University College of Engineering,
University of Tehran,
Tehran 1417466191, Iran
e-mail: Ashjaee@ut.ac.ir

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 10, 2015; final manuscript received May 5, 2016; published online June 7, 2016. Assoc. Editor: P. K. Das.

J. Heat Transfer 138(10), 102001 (Jun 07, 2016) (13 pages) Paper No: HT-15-1590; doi: 10.1115/1.4033616 History: Received September 10, 2015; Revised May 05, 2016

In this paper, an optimization was performed to achieve uniform distribution of convective heat transfer coefficient over a target plate using two impinging slot (air) jets. The objective function is the root mean square error (Erms) of the local Nusselt distribution computed by computational fluid dynamic (CFD) simulations from desired Nusselt numbers. This pattern search minimized this objective function. Design variables are nozzle widths, jet-to-jet distance, jet-to-target plate distance, frequency of pulsations (for pulsating jets), and the flow rate. First, an inverse design is performed for two steady jets for simplicity and the obtained errors for three different desired Nusselt numbers, NuD = 7, 10, and 13, were 20.73%, 20.08%, and 22.92%, respectively. Uniform distribution of heat transfer coefficient for two steady jets was not achieved. Thus, two pulsating jets are considered. The range of design variables for pulsating state is as same as steady-state and heat transfer rates increased about 400% over steady-state due to the effects of pulsations in inlet velocity. Thus, in the pulsating state, optimization must be performed for the desired Nusselt numbers around four-times NuD in the steady-state, i.e., NuD = 28, 40, and 52. The Erms reduced less than 0.01% and distribution of heat transfer coefficient for all cases was uniform. An experimental study using an inverse heat conduction method (conjugate gradient method with adjoint equation) has been performed and the experimental results for the case of NuD = 52 are presented. The estimated distribution of Nusselt number on the target plate with the numerical distribution has around 3.2% relative error with optimal configuration.

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References

Figures

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Fig. 2

(a) Experimental setup and (b) target plate for inverse method

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Fig. 1

(a) Schematic of the design surface and (b) boundary condition on domain

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Fig. 3

(a) Schematic of the computational domain and boundary condition for a confined slo-jet, (b) comparison the numerical result with the obtained result by Chirac and Ortega, comparison of experimental and numerical results for a pulsating confined slot-jet at Re = 900 and H/Dh = 4, (c) f = 0 Hz, and (d) f = 80 Hz

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Fig. 4

(a) Convergence history of Erms and (b) local Nusselt number at optimal state for Nu = 7, 10, and 13 in steady-state

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Fig. 5

(a) Convergence history of local Nusselt number and (b) local Nusselt number distribution at optimal state for different iterations at NuD = 28

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Fig. 6

(a) Convergence history of local Nusselt number and (b) local Nusselt number distribution at optimal state for different iterations at NuD = 40

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Fig. 7

(a) Convergence history of local Nusselt number and (b) local Nusselt number distribution at optimal state for different iterations at NuD = 52

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Fig. 12

Convergence history of Reynolds for NuD = 28, 40, and 52

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Fig. 13

Convergence history of St for NuD = 28, 40, and 52

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Fig. 14

Experimental and numerical local Nusselt distribution for NuD = 52

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Fig. 8

Convergence history of Erms for NuD = 28, 40, and 52

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Fig. 9

Convergence history of w/wt number for NuD = 28, 40, and 52

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Fig. 10

Convergence history of H/wt for NuD = 28, 40, and 52

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Fig. 11

Convergence history of s/wt for NuD = 28, 40, and 52

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