10
9
8
7
6
5
6
7
8
10
10
10
Rayleigh Number
Figure 23. Nusselt and Rayleigh number plot for the 2-in. pipe in the
1-ft 1-ft enclosure (experimental data).
10
9
8
7
6
5
105
106
107
Rayleigh Number
Figure 24. Nusselt and Rayleigh number plot for the 2-in. insulated pipe
in the 1-ft 1-ft enclosure (experimental data).
Experimental data obtained for the 2-ft 4-ft enclosure are somewhat limited.
Time constraints resulted in only one pipe configuration and limited temperature
combinations. Steady-state temperatures took longer to achieve (compared to the
1-ft 1-ft enclosure), and even then may have been influenced by the room tem-
perature, which fluctuated over a 5F temperature range. Some low temperature
tests were attempted with only the 8-in. pipe heated; however, the pipe heater was
not able to hold the desired temperature (at or above 235F) for all desired tests.
Figure 25 shows the Nusselt and Rayleigh number plots. Gap width was deter-
mined by using an effective radius of the heated pipe(s); the values are in Table 8.
The interior temperature range for these data is from about 3F to 80F. This
almost spans the range of interest for most utilidor designs, even though a rather
narrow range of Rayleigh numbers was obtained.
34
Go to Contents
Previous Page
