Heat-transfer measurements on two bodies of revolution at a Mach number of 3.12 Page: 5 of 37
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NACA TN 3776
optical differentiator. The optical differentiator was similar to that
described in reference 9 plus the added provision for attaching it to a
drafting machine thus permitting a direct reading of the tangent angle.
Slopes obtained by both methods were found to have a maximum deviation
of ~a percent franm the slope of an analytical curve. For most of the
data presented herein, the optical differentiator was used.
The adiabatic wall temperature Tad needed to evaluate the heat-
transfer coefficient is usually obtained with the model at the zero heat-
transfer condition. However, because of the effect of heat transfer, a
the location of transition varied considerably from that obtained at a
adiabatic wall conditions (see ref. 7). For this reason, the recovery
temperature was taken as
Tad = T1 +1(T'-T1)
where the temperature recovery factor 4 = ,JF for laminar flow and
- = / for turbulent flow, with the Prandtl number Pr evaluated
at adiabatic wall temperature. In the cases that could be checked, the
experimental recovery temperatures agreed closely with those calculated
using the theoretical recovery factor.
A knowledge of the variation of specific heat with temperature of
the model material is required to apply equation (2) over a large tem-
perature range. The specific heat of monel has been established over
the temperature range of this investigation (refs. 10 and 11); however,
the specific heat of "'K" monel is unknown. Since the composition of
"K" moel and monel are very nearly the same (table I), it was antici-
pated that the respective specific heats would be approximately equal.
To verify this assumption, the theoretical specific heats for monel and
"K" monel were evaluated using Kopp's rule (ref. 12) and compared with
the experimental values for monel. Figure 5 shows the result of this
comparison. The theoretical specific heats obtained for both alloys
agree closely with the experimental values for monel between 1500 and
5000 R. As a result, the experimental specific heats for monel were
used to reduce the data. The disagreement that exists between theory
and experiment at the high temperatures is due to the inadequacy of the
theory in this temperature range.
The accuracy of the experimental data was determined from the esti-
mated uncertainties of the individual measurements entering into the de-
termination of the final results. (Appendix B explains the radiation and
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Jack, John R. & Diaconis, N. S. Heat-transfer measurements on two bodies of revolution at a Mach number of 3.12, report, October 1956; (https://digital.library.unt.edu/ark:/67531/metadc56003/m1/5/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.