50
10
1991 Data, Unpainted Pipe
199596 Data, Unpainted Pipe
1996 Data, Painted Pipe
1
106
107
Rayleigh Number
Figure 21. Nusselt and Rayleigh number plot for the 4-in. pipe in the
1-ft 1-ft enclosure (experimental data).
50
10
5
105
106
Rayleigh Number
Figure 22. Nusselt and Rayleigh number plot for the insulated 4-in.
pipe in the 1-ft 1-ft enclosure (experimental data).
heat flux data versus the difference between the average interior wall temperature
and the average pipe temperature, it was found that a number of data points did
not agree with a general linear trend of the data. This was eventually traced to events
involving the low temperature coolant supply and the fact that the low tempera-
ture chiller was being run manually. In these cases the coolant became too warm
before an operator was able to get the chiller back on line. This was not observed in
the thermocouple data being monitored; although it appeared that steady condi-
tions had been reached, apparently temperatures were still changing slowly.
Figure 23 contains the data for the 2-in. uninsulated pipe; two outliers are
observed. Figure 24 contains the data for the 2-in. insulated pipe; two outliers are
in this plot although they cannot easily be discerned. Those data determined to be
outliers are indicated in Appendix A and were not used in further analysis or com-
parisons.
33
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