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Research Papers: Heat and Mass Transfer

Effect of Variable Properties and Radiation on Convective Heat Transfer Measurements at Engine Conditions

[+] Author and Article Information
Nathan J. Greiner, Marc D. Polanka, James L. Rutledge, Andrew T. Shewhart

Department of Aeronautics and Astronautics,
Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received September 18, 2015; final manuscript received April 26, 2016; published online June 14, 2016. Assoc. Editor: Jim A. Liburdy.This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Approved for public release; distribution is unlimited.

J. Heat Transfer 138(11), 112002 (Jun 14, 2016) (8 pages) Paper No: HT-15-1606; doi: 10.1115/1.4033537 History: Received September 18, 2015; Revised April 26, 2016

Convective heat transfer from a fluid to a surface is an approximately linear function of driving temperature if the properties within the boundary layer are approximately constant. However, in environments with large driving temperatures like those seen in the hot sections of gas turbine engines, significant property variations exist within the boundary layer. In addition, radiative heat transfer can be a significant contributor to the total heat transfer in a high-temperature environment such that it can not be neglected. As a result, heat transfer to the surface becomes a nonlinear function of driving temperature and the conventional linear heat flux assumption cannot be employed to characterize the convective heat transfer. The present study experimentally examines the nonlinearity of convective heat flux on a zero-pressure-gradient flat plate with large freestream to wall-temperature differences. In addition, the need to account for the radiative component of the overall heat transfer is highlighted. Finally, a method to account for the effects of both variable properties and radiation simultaneously is proposed and demonstrated. Overall, the proposed technique provides the means to quantify the independent contributions of radiative and variable property convective heat transfer to the total conductive heat transfer to or from a surface in a single experiment.

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References

Figures

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Fig. 1

Numerical results of Greiner et al. [4] showing (a) the nonlinearity of convective heat flux (no radiation component) and (b) the variability of the convective heat transfer coefficient with Tw/T∞

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Fig. 2

Diagram of experimental facility

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Fig. 6

Nondimensionalized ratio of convective heat transfer coefficient with a radiation correction for various n applied to the temperature ratio method of Kays et al. [6]: (a) n = 0.00, (b) n = −0.14, (c) n = −0.20, (d) n = −0.30, (e) n = −0.39, and (f) n = −(0.129 + 0.171Tw/T)

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Fig. 5

Conductive heat flux modeled by Eq. (8) with n= Eq. (4)

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Fig. 4

Conductive heat flux (a) and convective heat transfer coefficient ratio (b) assuming variable property flow with n = Eq. (4) and negligible radiation (i.e., qconv″=qcond″)

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Fig. 3

Conductive heat flux with regressed function assuming constant property flow and negligible radiation

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Fig. 7

Convective component of the measured conductive heat transfer after removing the measured radiative component; n= Eq. (4)

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